NASA/SP—2010–216283

A History of the Lightning Launch Commit 

Criteria and the Lightning Advisory Panel for 

America’s Space Program

Francis J. Merceret, Editor

NASA, John F. Kennedy Space Center

John C. Willett, Editor

Air Force Research Laboratory (Retired)

Hugh J. Christian

University of Alabama in Huntsville

James E. Dye

National Center for Atmospheric Research, Boulder, Colorado

E. Phillip Krider

University of Arizona, Department of Atmospheric Sciences

John T. Madura

NASA, John F. Kennedy Space Center

T. Paul O’Brien

Aerospace Corporation, El Segundo, California

W. David Rust

National Severe Storms Laboratory

Richard L. Walterscheid

Aerospace Corporation, Space Sciences Department, El Segundo, California

National Aeronautics and

Space Administration

John F. Kennedy Space Center

Kennedy Space Center, FL 32899

August 2010

i

Executive Summary

Since natural and artificially-initiated (or ‘triggered’) lightning are demonstrated hazards to the launch of space 

vehicles, the American space program has responded by establishing a set of Lightning Launch Commit 

Criteria (LLCC) and Definitions to mitigate the risk. The LLCC apply to all Federal Government ranges and 

have been adopted by the Federal Aviation Administration for application at state-operated and private 

spaceports.

The LLCC and their associated definitions have been developed, reviewed, and approved over the years of the 

American space program starting from relatively simple rules in the mid-twentieth century (that were not 

adequate) to a complex suite for launch operations in the early 21st century. During this evolutionary process, a 

“Lightning Advisory Panel (LAP)” of top American scientists in the field of atmospheric electricity was 

established to guide it.

This history document provides a context for and explanation of the evolution of the LLCC and the LAP. A 

companion document on the rationale is currently being prepared by the LAP to provide the physical, 

mathematical, and operational justification for the current LLCC.

Lightning that takes place naturally in thunderstorms was recognized as a threat to spaceflight early in the 

space age, and the early launch rules prohibited flight through thunderstorms. What had not been recognized 

until Apollo XII was launched in 1969, was that an ascending rocket could “trigger” lightning if it flew into 

highly electrified clouds, even in the absence of natural lightning. Apollo XII was struck twice by triggered 

lightning, and as a result, additional rules were added to forbid flying within 5 NM of thunderstorms or 

through certain non-thunderstorm clouds that experience showed had the potential of being electrified.

During the time between Apollo XII and the beginning of the Space Shuttle Program, several important 

research programs were carried out to learn more about lightning and cloud electricity in Florida, and 

additional instrumentation was installed at the KSC and Eastern Range (ER). The LLCC were modified for the 

Skylab program in 1973 and again for the Apollo-Soyuz Test Project in 1975. Expendable launch vehicles 

(ELV) had their own separate but similar rules. In 1979 the nascent Shuttle program adopted a set of LLCC 

that included constraints and waivers that were based on surface electric field mill measurements. The ELV 

rules did not adopt the field mill criteria.

In 1987, triggered lightning caused the loss of Atlas/Centaur 67 (AC 67) and its Fleetsatcom payload. A major 

cause of this accident was the failure of the ELV rules to include a field mill criterion. The Shuttle rules would 

have prohibited the launch of AC 67. In the aftermath of several investigations and a Congressional Hearing, a 

lightning “Peer Review Committee”, a predecessor of the LAP, was established to guide NASA and the Air 

Force in the drafting of LLCC and the conduct of associated research. Several major research projects were 

undertaken, including the first “Airborne Field Mill Program” (ABFM I, 1990-1992) in which direct 

measurements of electric fields in Florida clouds were made from a specially instrumented aircraft. ABFM I 

resulted in several improvements to the LLCC, and the lessons learned ultimately led to an even more 

successful ABFM II campaign a decade later.

As new knowledge and additional operational experience has been gained, the LLCC have been updated to 

preserve or increase their safety and increase launch availability. All launches of ELV and manned vehicles 

now use the same rules, which simplifies their understanding and application and minimizes the cost of the 

weather infrastructure to support them. In the future, the processes and procedures that have evolved can be 

used to facilitate further improvements in both launch availability and safety as new research findings become 

available.

Preface

Natural and triggered lightning is a demonstrated hazard to the launch of space vehicles, and the American 

space program has responded by establishing the “Lightning Launch Commit Criteria (LLCC)” to mitigate the 

risk. These LLCC are a complex set of rules with associated Definitions which must be satisfied before the 

launch of a space vehicle is permitted. The Definitions are an integral part of the LLCC and the term LLCC as 

used in this History is explicitly intended to include those Definitions. They apply to all Federal Government 

ranges including not only the well-known Eastern Range at Cape Canaveral, Florida and the Western Range at 

Vandenberg AFB, California, but also to smaller ranges such as the NASA range at Wallops Island, Virginia 

and the Air Force range at Kwajalein Atoll in the Pacific Ocean and others. In addition, these same LLCC 

have been adopted by the Federal Aviation Administration for application at state-operated and private 

spaceports.

The LLCC are developed and approved through a complex process, but the core science and recommendations 

for precise wording of the operative parts of the rules are provided by a “Lightning Advisory Panel (LAP)” 

consisting of American scientists working in atmospheric electricity and related disciplines including cloud 

physics and statistics. The LAP works closely with the operational personnel who must implement the LLCC 

in practice to assure that the rules are not only scientifically sound, but also realistic and practical.

The LLCC have evolved over the history of the American space program from relatively simple mid-twentieth 

century rules that proved inadequate to the complex suite that governs launch operations in the early part of the 

21st century. Following the destruction of an Atlas-Centaur launch vehicle by triggered lightning in 1987, the 

LAP was established to guide the process. Expert guidance is required because there is always a tension 

between the essential need to fly safely by avoiding lightning strikes and the need to fly economically by 

avoiding unnecessary launch delays and scrubs. The LLCC have become complex because increased 

knowledge has permitted exceptions under certain conditions from what are otherwise broad prohibitions to 

flight. These exceptions reduce the number of occasions under which a launch will be scrubbed for violation of 

the LLCC when, in fact, it would have been safe to fly.

As the LLCC have become more complex, launch vehicle operators, range managers, and safety personnel 

have continuously requested briefings and discussions on the origin of the rules and the rationale behind them. 

This history document is designed to provide a historical context and explanation for the origin of the LLCC 

and the LAP. A companion rationale document is being prepared by the LAP to provide the scientific, 

mathematical, and operational basis for the current LLCC.

Acknowledgements

Reconstructing more than 50 years of the history of weather support required a substantial effort not only by 

the authors and editors of this document, but also by colleagues and associates. Much of the history has not 

been formally documented before, and much of what existed at one time has now apparently been lost. This 

task would not have been possible without the assistance of many people who took time away from their busy 

workloads and deadlines to help us track down important events that are shrouded in the mists of the past.

We especially appreciate and recognize the contributions and assistance of the USAF 45th Weather Squadron 

at Cape Canaveral Air Force Station (CCAFS) and Patrick AFB in Florida and the NOAA Spaceflight 

Meteorology Group (SMG) at Johnson Spaceflight Center in Houston, Texas. We thank Bill Roeder and Billie 

Boyd of the 45th Weather Squadron and Michael Maier and David Chapman of the Eastern Range Technical 

Services Contractor (Computer Sciences Raytheon) for providing the history of lightning-related and other 

instrumentation at Kennedy Space Center (KSC) and CCAFS. We thank Tim Oram of SMG for his insights on 

weather support during the early years of manned spaceflight. 

Bill Bihner and Jack Ernst (retired) at NASA headquarters provided recollections of the formation of the Peer 

Review Committee and its evolution into the modern Lightning Advisory Panel.

Launa Maier of the KSC Safety and Mission Assurance Directorate provided valuable recollections of the 

research programs and lightning infrastructure development during the years immediately following the AC 67 

accident.

In addition to providing a figure and some references for the document, Jennifer Wilson of the KSC Weather 

Office handled the logistics of several face-to-face meetings of the LAP at KSC. Without these meetings 

dedicated to this History’s organization and production, it could not have been completed.

Jennifer Rosenberger of the KSC Launch Processing Directorate did extensive reformatting and copy editing 

to prepare the original manuscript for public release in this NASA Special Publication series. We appreciate 

her diligence and attention to detail that substantially reduced the number of errors and inconsistencies in the 

presentation of the material.

Funding for the project was provided by the NASA Office of Safety and Mission Assurance (OSMA) 

Assurance Management Office (AMO). The authors and editors appreciate OSMA/AMO reviews of the final 

draft of this paper by Launa Maier and Tony Willingham.

Notice

Mention of a proprietary product or service does not constitute an endorsement thereof by the Editors, the 

authors, or the National Aeronautics and Space Administration.
iv

Table of Contents

Executive Summary ...............................................................................................................................................i

Preface................................................................................................................................................................. iii

Acknowledgements................................................................................................................................................i

Notice.....................................................................................................................................................................i

Table of Contents.................................................................................................................................................iv

Table of Figures...................................................................................................................................................ix

List of Tables .......................................................................................................................................................ix

List of Acronyms ..................................................................................................................................................x

Chapter 1 Introduction.......................................................................................................................................1

1.0 Background ...........................................................................................................................................1

1.1 A Summary of the 2009 Lightning Launch Commit Criteria (LLCC) .................................................2

1.1.1 Surface Electric Fields..................................................................................................................3

1.1.2 Lightning.......................................................................................................................................3

1.1.3 Cumulus Clouds............................................................................................................................3

1.1.4 Attached Anvil Clouds..................................................................................................................3

1.1.5 Detached Anvil Clouds.................................................................................................................3

1.1.6 Debris Clouds................................................................................................................................3

1.1.7 Disturbed Weather ........................................................................................................................4

1.1.8 Thick Cloud Layers.......................................................................................................................4

1.1.9 Smoke Plumes...............................................................................................................................4

1.1.10 Triboelectrification........................................................................................................................4

1.2 The Current Weather Infrastructure at the Eastern Range (including KSC).........................................4

1.2.1 Atmospheric-Electrical Sensors....................................................................................................4

1.2.2 Weather Radar...............................................................................................................................5

1.2.3 Surface Observations ....................................................................................................................5

1.2.4 Upper Air Observations................................................................................................................5

1.2.5 Other Observations and Forecast Assets.......................................................................................5

1.2.6 Numerical Weather Prediction......................................................................................................6

1.3 The Organization of Weather Support to the Shuttle Program and the Eastern Range ........................6

1.4 Infrastructure and Organization at Other Ranges..................................................................................6

Chapter 2 The Early Years (through 1969) .......................................................................................................7

2.0 Background ...........................................................................................................................................7

2.1 Infrastructure.........................................................................................................................................8

2.2 Organization........................................................................................................................................10

2.3 Operations...........................................................................................................................................10
v

2.4 Research.............................................................................................................................................. 12

Chapter 3 The Aftermath of Apollo XII (1969 – 1980) .................................................................................. 14

3.0 The Apollo XII Investigations............................................................................................................ 14

3.1 Infrastructure....................................................................................................................................... 15

3.2 Organization ....................................................................................................................................... 15

3.3 Operations........................................................................................................................................... 16

3.3.1 Apollo XIV – Apollo XVI.......................................................................................................... 16

3.3.2 Skylab ......................................................................................................................................... 16

3.3.3 The Apollo-Soyuz Test Project (ASTP)..................................................................................... 16

3.3.4 The Viking Missions................................................................................................................... 18

3.3.5 Atlas Centaur 38 (AC 38)........................................................................................................... 20

3.3.6 F11 Europa II.............................................................................................................................. 21

3.4 Research.............................................................................................................................................. 22

3.4.1 Attempts to Reduce Lightning.................................................................................................... 22

3.4.2 Russian Research ........................................................................................................................ 22

3.4.3 Post-ASTP Airborne Experiments.............................................................................................. 23

3.4.4 Thunderstorm Research International Project (TRIP)................................................................ 24

3.4.5 Sensor Development................................................................................................................... 25

Chapter 4 The Space Shuttle Era Begins (1981 – 1987)................................................................................. 29

4.0 Background......................................................................................................................................... 29

4.1 Infrastructure....................................................................................................................................... 29

4.2 Organization ....................................................................................................................................... 30

4.3 Operations........................................................................................................................................... 30

4.3.1 Challenger................................................................................................................................... 30

4.3.2 Atlas Centaur 67 (AC 67)........................................................................................................... 31

4.4 Research.............................................................................................................................................. 32

4.4.1 KSC Rocket Triggered Lightning Program (RTLP)................................................................... 32

4.4.2 Research on Lightning Strikes to Aircraft .................................................................................. 34

Chapter 5 The Aftermath of Atlas Centaur 67 (1987 – 1999)......................................................................... 35

5.0 The AC 67 Investigations................................................................................................................... 35

5.0.1 Busse Panel................................................................................................................................. 35

5.0.2 The National Academy of Sciences............................................................................................ 37

5.0.3 Aerospace Corporation-Heritage ................................................................................................ 38

5.0.4 The Subcommittee on Space Science and Applications Hearing ............................................... 40

5.1 Infrastructure....................................................................................................................................... 48

5.1.1 LPLWS Upgrade......................................................................................................................... 48
vi

5.1.2 Lightning Detection and Ranging (LDAR).................................................................................49

5.1.3 CGLSS Upgrade .........................................................................................................................49

5.1.4 Radar Display Upgrade...............................................................................................................49

5.1.5 Additional Eastern Range Systems.............................................................................................49

5.1.6 Kodiak Alaska Launch Complex ................................................................................................50

5.2 Organization........................................................................................................................................50

5.2.0 Space Shuttle Headquarters Support Office/Weather Office......................................................50

5.2.1 Lightning Advisory Panel ...........................................................................................................50

5.2.2 KSC Weather Office ...................................................................................................................51

5.2.3 Applied Meteorology Unit (AMU).............................................................................................52

5.3 Operations...........................................................................................................................................52

5.4 Research..............................................................................................................................................52

5.4.0 Methodologies for Airborne Electric Field Measurements.........................................................52

5.4.1 Airborne Field Mill Program (ABFM I) .....................................................................................53

5.4.2 Convection and Precipitation/Electrification Experiment (CaPE)..............................................56

5.4.3 Rocket Triggered Lightning Program (RTLP) Results...............................................................60

5.4.4 Stanford Research Institute (SRI) ...............................................................................................65

5.4.5 New Mexico Institute of Mining and Technology Studies.........................................................66

5.5 Lightning LCC....................................................................................................................................67

5.5.1 The LAP Process.........................................................................................................................67

5.5.2 LLCC Revisions – 1991..............................................................................................................68

5.5.3 LLCC Revisions – 1992..............................................................................................................70

5.5.4 LLCC Revisions – 1995..............................................................................................................70

5.5.5 LLCC Revisions – 1998..............................................................................................................70

5.5.6 Proposed Field Mill Aloft Rule...................................................................................................72

Chapter 6 ABFM II and Beyond (2000 – 2010)..............................................................................................73

6.0 Background .........................................................................................................................................73

6.1 Infrastructure.......................................................................................................................................73

6.2 Organization........................................................................................................................................73

6.3 Operations...........................................................................................................................................74

6.4 ABFM II Research..............................................................................................................................75

6.4.1 Overview.....................................................................................................................................75

6.4.2 Experimental Design...................................................................................................................75

6.4.3 Instrumentation ...........................................................................................................................75

6.4.4 The 2000 field campaign.............................................................................................................77

6.4.5 The 2001 Field campaign............................................................................................................78
vii

6.4.6 Quality Control and Synchronization of Data ............................................................................ 79

6.4.7 Major Results – VAHIRR........................................................................................................... 80

6.4.8 Major Results – Stand-off Distances.......................................................................................... 80

6.4.9 Other Results .............................................................................................................................. 80

6.4.10 Lessons Learned ......................................................................................................................... 82

6.5 Lightning LCC.................................................................................................................................... 82

6.5.1 ABFM II Planning Discussions.................................................................................................. 82

6.5.2 LLCC Revisions – 2005 ............................................................................................................. 83

6.5.3 LLCC Revisions – 2009 ............................................................................................................. 84

Chapter 7 Conclusions and Lessons Learned.................................................................................................. 86

Appendix I The Lightning Launch Commit Criteria (LLCC) and Associated Definitions........................... 88

A1.1 Post Apollo XII Lightning LCC (LLCC) 1970................................................................................... 88

A1.2 Skylab (1973) LLCC .......................................................................................................................... 88

A1.3 Apollo-Soyuz Lightning LLCC 1975................................................................................................. 88

A1.4 AC 38 (1976) LLCC........................................................................................................................... 88

A1.5 Original Space Shuttle LLCC 1979.................................................................................................... 89

A1.6 1986 Shuttle Lightning Launch Commit Criteria (LLCC) ................................................................. 89

A1.7 Atlas/Centaur 67 Lightning Launch Commit Criteria (1987)............................................................. 89

A1.8 Heritage LRC Recommended LLCC (1988)...................................................................................... 90

A1.9 Space Shuttle LLCC (1992 – 1998).................................................................................................... 93

A1.9.1 Space Shuttle LLCC (1992)[LCN# 00230R04] ......................................................................... 93

A1.9.2 Space Shuttle LLCC (1995)[LCN# 00520R03] ......................................................................... 95

A1.9.3 Space Shuttle LLCC (1998)[LCN# 00824R03] ....................................................................... 100

A1.10 Space Shuttle LLCC (2005)[LCN# 01166R01]................................................................................. 106

A1.11 Current Space Shuttle LLCC (adopted 2009)[LCN# WEA-1].......................................................... 115

A1.12 Current (through 25 March 2010) FAA LLCC (14 CFR 417, Appendix G)..................................... 126

A1.13 LAP Recommendation (2008) in FAA format. ................................................................................. 132

Appendix II A Detailed LAP/LLCC Chronology 1991 – 2009 .................................................................... 143

Appendix III Members of the PRC/LAP.................................................................................................... 191

Appendix IV ABFM I Science Team and Key Results.............................................................................. 194

Appendix V ABFM II Science Team and Key Results................................................................................ 195

Appendix VI Apollo XII Timeline ............................................................................................................. 197

Appendix VII Evolution of the Lightning Instrumentation at CCAFS........................................................ 200

Appendix VIII Weather Instrumentation at KSC/CCAFS ............................................................................ 205

A8.1 Systems for Atmospheric Electricity: Electric Field Mills (LPLWS), CGLSS, LDAR and NLDN .. 205

A8.1.1 Electric Field Mills (LPLWS)....................................................................................................... 205
viii

A8.1.2 Cloud To Ground Lightning Surveillance System (CGLSS)........................................................206

A8.1.3 Lightning Detection and Ranging (LDAR)...................................................................................208

A8.1.4 U.S. National Lightning Detection Network (NLDN)..................................................................209

A8.2 Weather Radar......................................................................................................................................210

A8.3 Surface Systems...................................................................................................................................210

A8.3.1 Meteorological Towers .................................................................................................................210

A8.3.2. Manual Observations ...................................................................................................................211

A8.3.3 Ceiling, Visibility and Soil Moisture ............................................................................................212

A8.3.4 Rainfall..........................................................................................................................................212

A8.3.5 Offshore Data Buoys.....................................................................................................................212

A8.4 Upper Air Systems...............................................................................................................................213

A8.4.1 Balloons.........................................................................................................................................213

A8.4.2 Doppler Radar Wind Profilers.......................................................................................................213

A8.4.3 Weather Reconnaissance Aircraft .................................................................................................215

A8.5 Additional Observation and Forecast Assets .......................................................................................216

A8.5.1 Data Integration and Display Systems.........................................................................................216

A8.5.2 Forecast Tools and Indices............................................................................................................216

A8.6 Numerical Weather Prediction (computer models)..............................................................................217

References.........................................................................................................................................................219
ix

Table of Figures

Figure 2.3.1 Sketch of meteorological conditions during the Apollo XII incident ............................................ 12

Figure 3.3.3-1 Flight plan to determine electric fields prior to the Apollo-Soyuz Test Project ........................ 17

Figure 3.3.4-1 Contours of the electric field at the ground shortly after the launch of Viking 2 ...................... 20

Figure 3.4.3-1 Measurements of electric field around a thunderstorm.............................................................. 24

Figure 3.4.5-1 KSC LDAR Sites....................................................................................................................... 28

Figure 5.4.1-1 Electric field magnitude as a function of distance from cloud edge .......................................... 56

Figure 5.4.2-1 Radar elevation scan from Jameson et al., 1996 ........................................................................ 58

Figure 5.4.2-2 Growing cumulus example adapted from Dye et al., 1992........................................................ 59

Figure 5.4.3-1 Triggering success vs. surface field during the RTLP ............................................................... 63

Figure 5.4.4-1 Table 2 reproduced from Gori and Harris-Hobbs (1991) .......................................................... 66

Figure 6.4.3-1 A field mill on the side of the Citation fuselage ........................................................................ 76

Figure 6.4.3-2 The UND Citation Wing-mounted cloud physics sensors......................................................... 77

Figure 6.4.4-1 UND Citation calibration flight at the SLF................................................................................ 78

Figure 6.4.9-1 Example of the abrupt electric field transition in an anvil......................................................... 81

Figure A1.8-1 Heritage (1988) Fig. 7-1, Instantaneous Critical Electric Field Intensity vs Altitude................ 91

Figure A2-1 Expanded Space Shuttle LLCC (1998) Attached Anvil Rule ..................................................... 164

Figure A2-2 Space Shuttle LLCC (2005) Attached Anvil Rule ...................................................................... 165

Figure A2-3 Expanded Space Shuttle LLCC (1998) Detached Anvil Rule .................................................... 166

Figure A2-4 Space Shuttle LLCC (2005) Detached Anvil Rule ..................................................................... 167

Figure A2-5 Expanded Space Shuttle LLCC (2005) Attached Anvil Rule ..................................................... 183

Figure A2-6 Expanded LAP Recommended (10/06/08) Attached Anvil Rule ............................................... 184

Figure A2-7 Expanded Space Shuttle LLCC (005) Detached Anvil Rule ...................................................... 185

Figure A2-8 Expanded LAP Recommended (10/06/08) Detached Anvil Rule............................................... 186

Figure A2-9 Expanded Space Shuttle LLCC (2005) Debris-Cloud Rule........................................................ 189

Figure A2-10 Expanded LAP Recommended (10/06/08) Debris-Cloud Rule ................................................ 190

Figure A8.1.1-1 The KSC/CCAFS Launch Pad Lightning Warning System (LPLWS)................................. 206

Figure A8.1.1-2 An electric field mill ............................................................................................................. 207

Figure A8.1.2-1 4DLSS sensor locations ........................................................................................................ 208

Figure A8.1.3-1 Locations of the original KSC LDAR sensors...................................................................... 209

Figure A8.3.1-1 Location of surface meteorological towers operated by the Eastern Range ......................... 211

Figure A8.4.2-1 Locations of the Eastern Range and KSC wind profilers...................................................... 214

List of Tables

Table 5.0.1-1 Members of the expert Sub-Panel of the Busse Panel................................................................. 36

Table 5.0.3-1 Lightning Review Committee ..................................................................................................... 39
x

List of Acronyms

30WS 30th Weather Squadron

45WS 45th Weather Squadron

4DLSS 4-Dimensional Lightning Surveillance System

AAT ABFM Analysis Team

ABFM Airborne Field Mill

AFCRL Air Force Cambridge Research Laboratories

AFETR Air Force Eastern Test Range

AGU American Geophysical Union

AIAA American Institute of Aeronautics and Astronautics

AMS American Meteorological Society

AMU Applied Meteorology Unit

ASTP Apollo-Soyuz Test Program

ATC Air Traffic Control

AWS Air Weather Service

CaPE Convection and Precipitation/Electrification Experiment

CCAFS Cape Canaveral Air Force Station

CCFS Cape Canaveral Forecast Facility

CG Cloud to Ground

CGLSS Cloud to Ground Lightning Surveillance System

CIF Central Instrumentation Facility

CSR Computer Sciences Raytheon

DRWP Doppler Radar Wind Profiler

ELV Expendable Launch Vehicle

ER Eastern Range

ESMC Eastern Space and Missile Center (early name for the ER)

ESSA Environmental Sciences Services Administration (predecessor of NOAA)

FAA Federal Aviation Administration

FSK Frequency Shift Keying

IAMAP International Association of Meteorological & Atmospheric Physics

IC In-Cloud

ICAE International Commission on Atmospheric Electricity

ID Identification

IRCC Interagency Review and Coordinating Committee

JSC Johnson Spaceflight Center

KSC Kennedy Space Center

LAP Lightning Advisory Panel

LCC Launch Commit Criteria

LCN LCC Change Notice

LDAR Lightning Detection and Ranging

LFCC Lightning Flight Commit Criteria and Associated Definitions (FAA's version of the LLCC)

LLCC Lightning Launch Commit Criteria (including their Associated Definitions)

LPLWS Launch Pad Lightning Warning System

LUT Launch Umbilical Tower

LWO Launch Weather Officer

LWT Launch Weather Team

MFFG Median Filter First Guess

MSC Manned Spaceflight Center (early name for JSC)

MSFC Marshall Spaceflight Center

NASA National Aeronautics and Space Administration
xi

NCAR National Center for Atmospheric Research

NMIMT New Mexico Institute of Mining and Technology

NRL Naval Research Laboratory

NOAA National Oceanic and Atmospheric Administration

NSF National Science Foundation

NWS National Weather Service

OAT Operational Acceptance Test

ONR Office of Naval Research

PAFB Patrick Air Force Base

PCM Pulse Code Modulation

PI Principal Investigator

PRC Peer Review Committee (early name for the LAP)

QC Quality Control

RF Radio Frequency

ROCC Range Operations Control Center (now the Morrell Operations Center [MOC])

RTLP Rocket Triggered Lightning Program

RTLS Return to Launch Site (a Space Shuttle launch abort mode)

TBD To Be Determined

TRIP Thunderstorm Research International Program

SMC Space and Missile Center

SMG Spaceflight Meteorology Group

USAF United States Air Force

VAFB Vandenberg Air Force Base

VAHIRR Volume Averaged Height Integrated Radar Reflectivity

WR Western Range

WRWS Western Range Weather System

WSO Weather Support Office

Page 1 of 234

Chapter 1 Introduction

Given the extraordinary record of accomplishments in the Earth and space sciences over the past 50 years, it is 

often difficult to remember the hazards that that have been overcome to make this progress possible.

Lightning—both natural and artificially-initiated or ‘triggered’ discharges—is still the primary weather hazard 

to spaceflight operations.

When aerospace engineers are presented with a threat from natural and/or triggered lightning, they have only 

two options: (1) hardening the system to withstand the effects of nearby and direct strikes and (2) avoiding the 

hazard by flying only under safe conditions. Hardening a system against lightning involves using a design and 

materials that can withstand large transients in the electrical environment. This approach will have a high cost 

in terms of time, money, and weight and may not even be achievable. Avoiding lightning means maintaining 

access to information that can be used to warn when a hazard is present, and it also means taking appropriate 

actions when there is a threat. The Lightning Launch Commit Criteria (LLCC) and the associated Definitions 

are a set of rules that can be used to avoid both natural and triggered lightning hazards during space launches. 

The LLCC are not perfect, but they are based on experience that suggests they are safe and produce a minimal 

number of false alarms.

The present LLCC and Definitions are a coupled set of rules that should be evaluated as a single unit. They 

have evolved in the light of imperfect scientific knowledge about cloud electricity and lightning physics. As 

new knowledge and techniques have become available, the LLCC have been improved, and they have gotten 

safer and launch availability has increased. Much of the increased knowledge and advances in technology have 

been motivated and supported by the needs of spaceflight operations. In this History, we will trace the origin 

of the LLCC and the experiences that have led to the improvements. In a companion Rationale document, we 

will describe the structure and physical basis for the current LLCC, with the hope that future advances in 

science and technology, coupled with more experience and practice, will lead to even better LLCC.

1.0 Background

From the beginning of the American space program, lightning has been a concern. If lightning strikes an 

ascending launch vehicle it can inject currents in excess of 100 kA with rise times in the microsecond range. 

Even if the primary lightning current is conducted entirely, and, for the most part, harmlessly, by the vehicle’s 

metallic skin, the resulting large electromagnetic fields can induce secondary currents in the interior structures 

leading to the destruction of the vehicle. Communications, guidance, navigation and control systems 

computers can be disrupted. Pyrotechnics designed to separate components in flight or as part of the range 

safety destruct system can also be triggered. When lightning strikes a space vehicle all effects are potentially 

adverse. The most likely result is loss of the mission, the booster and the payload.

In response to the threat of lightning and other weather hazards, weather observation and forecasting have 

been an integral part of ground support for launches at all American launch sites. In order to collect 

observations of sufficient density and sophistication, a specialized weather infrastructure is required at each 

site. To assure safety, mission success and consistency, a formal set of rules called “Lightning Launch Commit 

Criteria” (LLCC) and their associated Definitions prohibit launching unless certain weather constraints are 

met. For the newly-emerging private and state-operated spaceports, the Federal Aviation Administration 

applies similar rules that they call “Lightning Flight Commit Criteria” (LFCC). This history discusses the 

evolution of both the weather infrastructure and the LLCC from the beginning of American orbital spaceflight 

through the first decade of the 21st century. Just as importantly, it explores the organizations and people 

involved in designing and applying both the infrastructure and the LLCC.

This History focuses primarily on operations at Kennedy Space Center and Cape Canaveral Air Force Station 

(the Eastern Range), but the threat, and the responses to it, also affect Vandenberg Air Force Base (the 
Page 2 of 234

Western Range), Kwajalein Atoll (the Regan Test Range), NASA’s range at Wallops Island, the Alaskan 

Space Authority range on Kodiak Island, and the new private ranges in New Mexico, Oklahoma and 

elsewhere. The LLCC/LFCC are applied at all of these places (with a very few local variations where 

necessary) and have been designed with all of them in mind. The focus on the east coast of Florida here results 

primarily from the availability of documentation and the fact that funding and administrative leadership for the 

Lightning Advisory Panel (LAP) and much of the research on lightning and cloud electricity conducted over

the last 20 years has been provided by the Space Shuttle Program which launches only from KSC.

This work is organized largely but not strictly in chronological order beginning with the early days of 

America’s orbital space program in the next chapter. Chapter breaks are focused on major events which, by 

coincidence, fall nearly on decadal boundaries. As Chapter 2 describes, until Apollo XII was struck by 

triggered lightning in 1969, the focus of lightning avoidance was on natural lightning. Chapter 3 describes the 

changes resulting from investigations and research following Apollo XII up to the beginning of the Space 

Shuttle era. Chapter 4 covers the Shuttle and unmanned vehicle programs through the destruction of AtlasCentaur 67 by triggered lightning in 1987. Chapter 5 describes the changes resulting from investigations and 

research following AC 67 including the formation of the LAP and the first Airborne Field Mill Program 

(ABFM I) and closes out the 20th century. Chapter 6 picks up with the second Airborne Field Mill Program 

(ABFM II) which began in 2000 and takes us up to the present. In Chapter 7, the authors draw their 

conclusions and present their lessons learned. To keep the main body of the history from overwhelming the 

reader with detail, while assuring that the detail is available for those who might find it informative, eight 

appendices, some of them lengthy, are also provided. Because the material was drawn from a wide variety of 

sources covering about five decades, the units of measurement are not treated consistently. For ease of 

comparison, metric equivalents have been appended in parenthesis after non-metric units in most cases.

It will be helpful in understanding the significance of much of this history to know how weather support is 

presently provided. The remainder of this chapter will provide an overview of current (May 2010) weather 

support infrastructure and organization to the Shuttle Program and ELV operations at the Eastern Range (ER). 

A brief discussion of other Ranges is also provided. For similar reasons, a brief overview of the current 

Lightning Launch Commit Criteria (LLCC) is provided next.

1.1 A Summary of the 2009 Lightning Launch Commit Criteria (LLCC)

The current Lightning Launch Commit Criteria (LLCC), and their associated Definitions, Explanations and 

Examples are complex and are given in their entirety in Appendix I in several formats. To give the reader a 

feeling for the structure and content of the LLCC, a highly abbreviated paraphrase of each rule is offered here

(in italics to emphasize that these are not the actual rules). Note that many details about the definitions of terms 

and the required measurement techniques have been omitted for clarity and simplicity. Therefore, these 

paraphrases do not adequately describe all the hazardous weather situations and must not be used for launch 

support.

Although the Definitions associated with these rules are not given here, they should be reviewed in Appendix I 

because they are an integral part of the LLCC, and because the logic and wording of the LLCC depend in a 

critical way on these definitions. It should also be noted that all of the LLCC must be satisfied and that each 

one requires clear and convincing evidence to trained weather personnel that its constraints are not violated.

Under some conditions, trained weather personnel can make a clear and convincing determination that the 

LLCC are not violated based on visual observations alone. However, if the weather personnel have access to 

additional information, such as measurements from weather radar, lightning sensors, electric field mills, or 

aircraft, and if this information is within the criteria outlined in the LLCC, these data could allow a launch to 

take place when a visual observation alone would not.
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1.1.1 Surface Electric Fields

(Appendix I, Section A1.11, 1.4A)

Do not fly within 5 nm of any electric field mill that has shown readings in excess of 1 kV/m in the past 15 

minutes. The field threshold can be raised to 1.5 kV/m if all clouds within 10 nm of the flight path are 

transparent or if they (a)have tops warmer than +5 °C and (b) have not been part of convective clouds with 

tops colder than -10 °C for at least 3 hours.

1.1.2 Lightning

(Appendix I, Section A1.11, 1.4B)

Do not fly within 10 nm of any type of lightning, or any convective cloud that has produced it, within the past 

30 min. An exception is allowed if the cloud has moved beyond 10 nm and if an electric field mill within 5 nm 

of the lightning, and any other mills within 5 nm of the flight path, have shown less than 1000 V/m for at least 

15 minutes.

1.1.3 Cumulus Clouds

(Appendix I, Section A1.11, 1.4C)

Do not fly within 10 nm of any cumulus cloud with a top colder than -20 °C, nor within 5 nm of any cumulus 

cloud with a top colder than -10 °C. Do not fly through any cumulus cloud with its top colder than +5 °C. An 

exception is allowed for a cumulus cloud with its top between ±5 °C if that cloud is not producing 

precipitation and if a field mill within 2 nm of that top, and any other mills within 5 nm of the flight path, have 

shown the vertical component of the electric field greater than −100 V/m, but less than +500 V/m, for at least 

15 minutes.

1.1.4 Attached Anvil Clouds

(Appendix I, Section A1.11, 1.4D1)

Do not fly within 10 nm of any non-transparent, attached anvil for at least 30 minutes after the last lightning 

discharge occurs in the parent cloud or anvil, nor within 5 nm for 3 hours after the last lightning. Never fly 

within 3 nm of such a cloud. Two kinds of exceptions are allowed: 1) Flight is allowed up to 3 nm from an 

attached anvil at any time if it is colder than 0 °C everywhere within the prescribed distances of the flight 

path. 2) Flight is allowed through or within any distance of an attached anvil at any time if that anvil is colder 

than 0 °C everywhere and if its VAHIRR is less than 10 dBZ-km everywhere within 1 nm of the flight path.

1.1.5 Detached Anvil Clouds

(Appendix I, Section A1.11, 1.4D2)

Do not fly within 10 nm of a non-transparent, detached anvil for 30 minutes after the last lightning discharge 

occurs in the detached anvil (or in its parent cloud before detachment), nor within 3 nm for 3 hours after the 

last such lightning. Do not penetrate such an anvil for 3 hours after detachment, nor for 4 hours after it has 

produced lightning. Three kinds of exceptions are allowed: 1) Flight is allowed up to 3 nm from such an anvil 

during the first 30 minutes if the detached anvil is colder than 0 °C everywhere within 10 nm of the flight path.

2) Flight is allowed up to the edge of a detached anvil between 30 minutes and 3 hours after the last lightning 

if the radar reflectivity of all parts of that cloud within 5 nm of the flight path has been less than 10 dBZ, and if 

a field mill within 5 nm of the cloud, and any other mills within 5 nm of the flight path, have shown less than 

1000 V/m for at least 15 minutes. 3) Flight is allowed through or within any distance of such an anvil at any 

time if the cloud is colder than 0 °C and if its VAHIRR is less than 10 dBZ-km everywhere within the 

prescribed distances of the flight path.

1.1.6 Debris Clouds

(Appendix I, Section A1.11, 1.4E)

Do not fly within 3 nm of a non-transparent debris cloud for 3 hours after it detaches or decays from its parent 

cloud and for 3 hours after it has produced lightning. Two kinds of exceptions are allowed to the 3 nm standoff 

requirement: 1) Flight is allowed up to the edge of a debris cloud at any time if the radar reflectivity of any 
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part of that cloud within 5 nm of the flight path has been less than 10 dBZ, and if a field mill within 5 nm of the 

cloud, and any other mills within 5 nm of the flight path, have shown less than 1000 V/m, for at least 15 

minutes. 2) Flight is allowed through or within any distance of such a debris cloud at any time if the cloud is 

colder than 0 °C everywhere within 5 nm of the flight path and if VAHIRR is less than 10 dBZ-km everywhere 

within prescribed distances of the flight path.

1.1.7 Disturbed Weather

(Appendix I, Section A1.11, 1.4F)

Do not fly through any non-transparent cloud associated with disturbed weather that has cloud tops colder 

than 0 °C and that, within 5 nm of the flight path, either contains moderate or greater precipitation or shows 

evidence of melting precipitation.

1.1.8 Thick Cloud Layers

(Appendix I, Section A1.11, 1.4G)

Do not fly through a non-transparent cloud layer that is thicker than 4500 feet and contains temperatures 

between 0 °C and -20 °C, nor through any non-transparent cloud layer that is connected to such a thick cloud 

layer within 5 nm of the flight path. An exception is allowed if the thick cloud layer is cirriform, is entirely 

colder than -15 °C, contains no liquid water and has never been associated with a convective cloud.

1.1.9 Smoke Plumes

(Appendix I, Section A1.11, 1.4H)

Do not fly through any cumulus cloud that develops from a smoke plume for 60 minutes after it has detached 

from that plume.

1.1.10 Triboelectrification

(Appendix I, Section A1.12, G417.23)

Do not fly through any cloud (transparent or not) that is colder than -10 oC at vehicle velocities less than 3000 

ft/s unless the vehicle has been treated or hardened against surface discharges.

1.2 The Current Weather Infrastructure at the Eastern Range (including KSC)

The Eastern Range benefits from an extensive suite of weather instrumentation including surface 

meteorological towers, surface electric field mills, rain gauges, weather radar systems, weather balloon 

systems, Doppler wind profiling radars and more. A complete description of each system is presented in 

Appendix VIII. In this section we discuss the general types of instrumentation and their application to the 

LLCC and to weather support in general at the Range. The material is organized in the same manner and order 

as Appendix VIII. Thus, to find the detail applicable to section 1.2.x below, consult Appendix section A8.x 

where x ranges from 1 to 6.

1.2.1 Atmospheric-Electrical Sensors

The Range’s suite of lightning and electric-field sensors permits the detection and location of electric-charge 

centers aloft and lightning within clouds, between clouds, and from cloud to ground. It also permits an 

assessment of the magnitude and polarity of the lightning current in strokes to ground. The LLCC have many 

sections explicitly referring to these measurements. In addition, the lightning and electric-field sensors are 

used by the 45th Weather Squadron (45WS) forecasters for the issuance and cancellation of lightning watches 

and warnings for ground facilities at KSC/CCAFS and aircraft operations at the Shuttle Landing Facility at 

KSC.

Also, if a lightning strike occurs in close proximity to a launch complex or payload processing facility, it is 

sometimes required to retest the vehicle and/or payload to assure that no damage has been caused by the direct 

or induced electric currents from the nearby strike. The ability to precisely locate the strike points and to 
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estimate their amplitudes informs the decision-making process about whether potentially costly retesting is 

required.

Among the most unique and important of the atmospheric-electrical sensors at KSC/CCAFS is the large-area 

network of ground-based electric-field mills and the associated display that is known as the Launch Pad 

Lightning Warning System, or LPLWS (see Appendix VIII, A8.1.1). This system is unique in that it is the 

only observing system that is capable of giving advance warning of electrified clouds before the first lightning 

flash. It is used not only to issue lightning warnings for ground operations but also to provide relief in several 

of the current LLCC under otherwise questionable conditions.

Together, the suite of atmospheric electrical sensors at the KSC/ER is without question the most 

comprehensive and the most accurate that exists anywhere in the world today.

1.2.2 Weather Radar

Weather radar is used extensively, both in determining whether the LLCC are satisfied, and for forecasting the 

weather. The LLCC have sections explicitly referring to radar-based criteria (See Appendix I) for determining 

the locations, edges and heights of clouds and for assessing the threat of triggered lightning. Significant relief 

from the restrictive nature of the rules is available through the use of a radar-derived quantity called the 

Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) (See, e.g., 1.1.4 above). In addition, 

weather radar is essential to the issuance and cancellation of weather watches and warnings for protection of 

personnel, ground systems and facilities at KSC/CCAFS and aircraft operations at the Shuttle Landing Facility 

at KSC and the Air Force airfields at CCAFS and PAFB.

1.2.3 Surface Observations

Surface observations by meteorological instruments and trained human observers are used together with 

weather radar to determine quantities used by the LLCC including the altitude of the cloud base, the presence 

of thunder and whether or not the clouds are transparent. These data are also used to assess compliance with 

ground winds and visibility constraints applicable to launches and ground processing operations. They also 

support the issuance and cancellation of weather watches and warnings for protection of personnel, ground 

systems and facilities at KSC/CCAFS.

1.2.4 Upper Air Observations

Measurements of winds, temperature, pressure and relative humidity throughout the atmosphere from just 

above the surface to altitudes well above 20 km are essential for day to day weather forecasting. In addition, 

wind measurements over these altitudes are used for generating the steering commands used by launch 

vehicles on ascent and assessing the resulting aerodynamic loads that the vehicle will experience in flight. 

Finally, winds at the level of cirrus anvil clouds can be used to estimate when a thunderstorm anvil will form 

upstream that may cause a violation of the anvil LLCC.

Weather reconnaissance aircraft are used to determine the height and thickness of clouds required by the 

LLCC more precisely than radar is able to do. Although not available for day-to-day operations, on day of 

launch aircraft support may be provided. (See section A8.4.3)

1.2.5 Other Observations and Forecast Assets

A variety of tools is available to assist forecasters in making effective use of the large amount and variety of 

information provided by the weather instrumentation. These include systems for displaying the information in 

graphical or tabular form, and automated or semi-automated tools for forecasting the threat of specific weather 

events.
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1.2.6 Numerical Weather Prediction

The use of computer models has become an integral part of modern weather forecasting, and has lead to 

substantial improvements in the accuracy and lead time of forecasts. The 45WS uses the models run by the 

NOAA National Centers for Environmental Prediction as well as models run by the U.S. Navy and European 

governments. In addition, it has access to a high resolution local model run by the National Weather Service 

Office in nearby Melbourne, FL. These models all provide guidance which the forecasters may weigh and 

evaluate to inform their forecasts.

1.3 The Organization of Weather Support to the Shuttle Program

and the Eastern Range

All operational weather support to launch and ground processing operations at KSC and CCAFS is provided 

by the 45th Weather Squadron housed at Range Weather Operations in the Morrell Operations Center at 

CCAFS. Operational support for Shuttle landings (at any location including KSC) and on orbit operations is 

provided by the Spaceflight Meteorology Group (SMG) which is operated by the National Weather Service at 

Johnson Space Center (JSC) in Houston, TX. Weather support for Shuttle is split between SMG and 45WS 

because they have different customers and different mission requirements. SMG serves the Flight Directors at 

JSC and is co-located with them, while the 45WS serves the Launch Director and Shuttle Processing 

Directorate, both located at KSC. The primary responsibility for Shuttle weather support transfers from 45WS 

to SMG as soon as the Space Shuttle Vehicle leaves the launch pad and returns to 45WS upon “wheels stop” 

on landing.

In 1991 NASA, the Air Force and the National Weather Service collaborated to establish the Applied 

Meteorology Unit (AMU) co-located with Range Weather Operations at CCAFS and managed by the KSC 

Weather Office. The AMU provides technology development, evaluation and transition services to the 45WS, 

SMG and the NWS office at Melbourne, FL as well as directly to the Shuttle program. Many of the highly 

specialized tools used for weather support to both manned and unmanned operations on the Eastern Range and 

at KSC were developed or transitioned to operations by the AMU (Bauman et al., 2004).

The KSC Weather Office (KSCWO) has an agency-wide responsibility to assure that weather support to 

NASA spaceflight missions and operations, manned or unmanned, is adequate. This involves making sure 

weather requirements are well formulated and well stated by the NASA programs and properly understood by 

the weather support providers. The KSCWO manages or provides oversight to KSC-owned weather 

infrastructure, conducts or manages weather research in support of operations, and manages KSC budget line 

items directly related to weather support. Finally, the Office serves as a liaison between the weather support 

service providers and NASA managers, performing the functions of a staff meteorology office to NASA 

programs operating at KSC or CCAFS and the KSC Center Director.

1.4 Infrastructure and Organization at Other Ranges

The Western Range Weather System consists of 26 fully instrumented wind towers, six 915 MHz Boundary 

Layer Doppler Radar Wind Profilers/mini Sound Detection and Ranging System sites, a modernized Advanced 

Weather Interactive Processing System, a WSR-88D NEXRAD weather radar, a Lightning Location and 

Protection System, and two Automated Meteorological Profiling and Real Time Meteorological Profiling 

Systems. This entire suite of 173 instruments is used, in conjunction with contracted weather aircraft, to 

evaluate Lightning Launch Commit Criteria during launch operations. The Western Range does not have a 

network of electric field mills.
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Chapter 2 The Early Years (through 1969)

2.0 Background

U.S. Government-supported research into rocket-propelled vehicles began during World War II and 

accelerated with the capture of German V-2 rockets at the end of the war. The V-2 was far more capable than 

anything the U.S. had developed, and a special launch facility was built at White Sands, New Mexico to 

support test flights of the captured weapons. The New Mexico site proved inadequate for experiments with 

multi-stage versions of the V-2 since these long range flights would overfly populated areas.

After a number of studies involving considerations of everything from orbital mechanics to the logistics of 

transporting launch vehicle components to the launch site, the Joint Long Range Proving Ground was 

established in 1949 by the Department of Defense on the site of the old Banana River Air Station at Cape 

Canaveral, Florida. In 1951 this was renamed the Air Force Missile Test Center and in 1964 it was again 

renamed, this time to the Air Force Eastern Test Range. [Source: http://en.wikipedia.org/wiki/Eastern_Range 

retrieved 25 February 2010.] The Range consisted not only of the assets located at Cape Canaveral, but also of 

a network of down-range tracking stations and ships including stations at Antigua, Ascension Island and 

Argentia, Newfoundland. The best known tracking ship was the specially designed Vanguard which supported 

many of the Apollo launches and also made a number of goodwill stops at ports where the public was invited 

to tour the ship.

On 29 July, 1958, President Dwight D. Eisenhower signed Public Law 85-568, creating the National 

Aeronautics and Space Administration, also known as NASA. In July 1962, the agency established its Launch 

Operations Center adjacent to the Air Force test facility at Cape Canaveral on Florida's east coast, and renamed 

it in late 1963 to honor the president who put America on the path to the moon. The source for the material on 

the history of KSC in this section was 

<http://www.nasa.gov/centers/kennedy/about/history/timeline/1950.html accessed 25 March 2010>. Also see 

Benson and Faherty (1978).

On 24 Aug 1961 NASA announced that it intended to expand the Cape Canaveral facilities for manned lunar 

flight and other missions requiring advanced Saturn and Nova boosters by acquiring 80,000 acres of land north 

and west of the Air Force Missile Test Center facilities at the Cape. The U.S. Army Corps of Engineers was

designated to act as real estate acquisition agent for NASA, and the Lands Division of the Justice Department 

was designated to handle the legal aspects.

In July 1963 construction of the Vehicle Assembly Building began. At the time of its construction it was the 

largest building in the world, with an enclosed volume of 129,482,000 cubic feet. At a height of 525 feet, 10 

inches to the top of the finished roof of its high bays it was constructed with 98,590 tons of steel and 65,000 

cubic yards of concrete. Two years later, construction of the first stretch of the Crawlerway, between the 

Vehicle Assembly Building and Launch Pad 39A, was completed. Consisting of two 40-foot (12m) wide lanes 

separated by a 50-foot (15.2m) median, the Crawlerway was designed to support the 17,000,000 pound 

(7,727,300 kg) load of a Transporter carrying a Mobile Launcher and Apollo-Saturn V.

In January 1966 the first of three Mobile Launchers was moved into the Vehicle Assembly Building, which 

was essentially complete. Weighing in at 10,500,000 pounds, the Mobile Launchers functioned as erection 

platforms for the Apollo/Saturn Vs and launch stands for the vehicle at the pads. These same refurbished 

Mobile Launchers are used in the Space Shuttle program and are called Mobile Launch Platforms. In May of 

that year, the first Apollo/Saturn V, a facilities test model, was rolled out of the Vehicle Assembly Building 

atop a 6,000,000 pound Transporter, a public sign that the Apollo Program was well under way. Each of the 

two Transporters, built by the Marion Power Shovel Co., had a load capacity of 12,000,000 pounds, and when 

loaded, could traverse the Crawlerway between the VAB and the pad at a top speed of one mile per hour. 
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Today, these same "Crawler-Transporters" are used to move the Space Shuttle stacks atop their Mobile 

Launcher Platforms out to the pads for launch.

From the earliest days of aviation it became obvious that safe flight through the atmosphere depends critically 

on understanding the weather and avoiding its hazards. Although the flight of a spacecraft through the 

atmosphere is much briefer than that of an airliner, it is even more vulnerable to weather threats. What is less 

obvious is that ground processing of launch vehicles and their payloads is also extremely weather sensitive.

The major concerns for launch operations are winds and lightning. During ascent, the wind exerts both forces 

and torques on the rocket. In order to fly the desired trajectory, the vehicle must adjust its steering to account 

for the effects of the wind. In extreme cases, the vehicle may not have sufficient steering capability (called 

“control authority”) to make the required trajectory adjustments. As a result, the payload could end up in an 

unacceptable orbit. In some cases, flying the required trajectory may result in aerodynamic stresses that exceed 

the strength of the vehicle, resulting in its destruction. Even the surface winds at the launch pad are a concern.

As soon as the rocket lifts off, and before it has risen above any structures on the pad such as umbilical towers, 

strong winds could push the rocket into these structures causing destruction of both the vehicle and the pad.

Lightning is a concern for both launch and ground processing operations. During ascent, the absence of nearby 

natural lightning does not indicate the absence of a threat. If the flight path passes through electrically charged 

clouds, the rocket can initiate a lightning discharge that would not have occurred naturally. Avoiding such 

“triggered lightning” is the major function of the Lightning Launch Commit Criteria. A lightning strike can 

destroy a launch vehicle. The loss of Atlas Centaur 67 (see section 4.3.2 below) is an example. Natural 

lightning striking near the launch pad can damage electronic circuits in a payload, booster or ground 

processing equipment even if the lightning does not attach directly to the pad structure. This is because the 

electromagnetic fields from nearby strikes can induce harmful currents in nearly any network of electrical 

conductors. See the discussion of Gemini 2 in section 2.3 below for an example.

There are other weather concerns that can impact ground processing or launch, including heavy rainfall, 

extreme temperatures and reduced visibility, but these will not be discussed further here. The important point 

is that the weather infrastructure, weather support organizations and processes, and weather-related constraints 

to operations described in this History are all required for safe operation of any spaceport. The observations 

and lessons learned at KSC, the Eastern Range and other locations described here should be applicable to any 

spaceport anywhere.

2.1 Infrastructure

The early weather support infrastructure at the Eastern Range included not only trained weather observers, 

weather balloons and wind towers, but what for the time was an advanced technology, weather radar to detect 

and track precipitation. During the 1950s and 60s, the Range used a 3cm radar designated CPS-9 (Boyd et al., 

2003). Its short wavelength made it quite sensitive and capable of detecting very light precipitation and even 

non-precipitating clouds. However, its short wavelength also caused serious attenuation in moderate to heavy 

precipitation (ibid).

To support the 1960s manned spaceflight program, NASA constructed a 150 meter tall tower instrumented at 

seven levels to measure wind speed and direction, temperature and relative humidity. This provided vertical 

profiles of the properties of the atmosphere from the surface to a height near that of the top of the ApolloSaturn launch vehicle, thus enabling the entire environment to which the vehicle was exposed on the launch 

pad to be characterized. This tower was located northwest of Shuttle launch complex 39 (LC39) and east of 

the north end of the current Shuttle Landing Facility (SLF). Additional 18 meter towers were located at LC39 

(Johnson, 1976). When the SLF was built for the Shuttle program, three 10m towers were located respectively 

near the north, center and south ends of the runway.
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In addition to these towers dedicated to launch and landing support, NASA built a “mesonet” of surface wind 

towers on or near KSC while the Air Force built a similar network of 14 towers on and near Cape Canaveral 

Air Force Station. The surface tower networks were used for forecasting local weather such as thunderstorm 

initiation and for support to ground processing operations and facilities. As discussed in Chapter 4, Section 

4.1, these two networks were later combined. Observations of current weather, cloud type and coverage, 

visibility and current weather were made by human weather observers (see Appendix VIII, section A8.3.2).

Prior to the Apollo 12 incident, eight radioactive probes and eight corona current sensors were used to measure 

the atmospheric electric field (or potential gradient). The principle of operation of the radioactive probes 

assumes that a portion of the ions of one sign created by a radioactive source close to a conductor will be 

carried away by the field and a portion of the other sign will be returned to the sensor, depending upon the 

polarity of the field, until an equilibrium current flow is established. The output can be used as a measure of 

the field intensity and was recorded on strip chart recorders. The corona current sensor consisted of a 4-foot 

long whip antenna that was connected to a microammeter. This detector measured the current that flowed to or 

from the antenna in a large electric field, again roughly in proportion to the ambient field. All information was 

available in the weather office in real time. The primary disadvantages of both of these sensors were that they 

exhibited a non-linear response to the external field, and they were sensitive to precipitation, wind, and rapid 

field changes in a thundery environment. The sensors were also mounted close to buildings and on towers 

rather than on uniform terrain that was cleared of vegetation.

Ground-based assets did not provide the only weather observations on launch day. Weather reconnaissance 

aircraft were used at least as far back as the Apollo program. The exact landing site for Apollo 11 was 

retargeted based on aircraft confirmation of satellite data that indicated that a thunderstorm with tops to 50,000 

feet (15.2 km) was in the vicinity of the original landing target [Source: The Rescue of Apollo 11, Noel A. 

McCormach, Center for the Study of National Reconnaissance, accessed at 

<http://libertyyes.homestead.com/Hank-Brandli-25.html>]. A variety of aircraft provided by NOAA and the 

DoD were used for launch support to Apollo, the Apollo-Soyuz Test Project and Skylab 

<http://www.srh.noaa.gov/smg/apollo.htm>. These practices have continued into the present and 

reconnaissance aircraft routinely support both manned and unmanned spaceflight.

Preventing damage due to a lightning striking a spacecraft or ground support equipment at the launch pad is 

critical. If lightning strikes near a launch pad while a vehicle is present, it is highly desirable to know the exact 

location and intensity of the strike. The need to retest sensitive electronics can depend on the polarity, 

magnitude and rise time of the lightning current. The most important infrastructure solution for the Apollo 

launch pads was an insulated, folding mast mounted atop the hammerhead crane that capped the launch 

umbilical tower (LUT). This mast held up two overhead wires that were grounded several hundred meters 

from the mobile launch platform. A lightning rod on top of the mast extended above the vehicle sufficiently so 

that the lightning current would travel down one or both of the catenary wires and go into the ground without 

harming the vehicle itself. The hammerhead crane was the highest thing on the launch platform, and was 

capable of being extended over the top of the Saturn V vehicle (Benson and Faherty, 1978, Ch. 13).

This solution was only partially effective. Although no discharge ever struck the vehicle directly during the 

Apollo program, lightning did strike the LUT many times. To determine if a diverted or nearby strike may 

have induced sufficient voltages or currents to potentially damage the vehicle, payload, or ground support 

equipment, sensors were installed where the catenary wire went to ground and around the pad. In addition, 

three automatic TV cameras were installed around the periphery of the pad to help verify that lightning did not 

strike the vehicle and to estimate the strike point either by showing actual location or by triangulation.
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2.2 Organization

Weather support for all phases of Project Mercury (1960 – 1962) from ground processing through launch to 

landing was managed by the Project Mercury Weather Support Group (PMWSG) of the US Weather Bureau’s 

(USWB) National Meteorological Center (NMC) at Suitland, MD. In addition to the Suitland Office, there 

were PMWSG Units at Patrick AFB, FL and the National Hurricane Center (NHC) in Miami, FL.

Several high level reorganizations and changes in nomenclature took place between 1962 and 1966 as the 

space program grew beyond Mercury. The USWB became the Environmental Science Services Administration 

(ESSA) and the PMWSG became the Spaceflight Meteorology Group (SMG). The Suitland and NHC Units 

remained in place, but the Patrick AFB Unit was moved up the coast to Cape Canaveral/KSC and renamed the 

Cape Unit, while a Manned Spacecraft Center Unit was established in Houston, TX. A description of weather 

support during this period may be found in Nagler (1966). Under the 1963 Webb-McNamara agreement 

between NASA and DoD, the USAF provided standard weather observation and forecasting services to all 

Range users, and NASA provided specialized support through SMG.

During the Apollo era, ESSA became the National Weather Service (NWS) but the organization of SMG and 

its various units remained relatively stable. The NWS did pick up some responsibilities for coordinating 

weather support to NASA and Department of Defense (DoD) unmanned test ranges in the US and the Pacific.

2.3 Operations

Although a major focus of the LLCC today is on natural and artificially-initiated or triggered lightning, 

America’s space program was concerned almost immediately with natural lightning and its destructive 

potential due to a steady stream of lightning damage reports beginning with Mercury and Gemini programs. 

Some of the research performed and the techniques developed to avoid and mitigate damage from natural 

lightning during ground processing helped later when the space program became aware of the even greater risk 

posed by rocket-triggered lightning during ascent.

Gemini 2 & 5 On 17 Aug 1964 while the Gemini 2 launch vehicle (GLV-2) was being tested on launch 

complex 19, several observers reported a lightning strike at or near the pad. All testing was halted for a 

thorough investigation of the event. Inspection revealed no physical markings of any kind but disclosed a 

number of failed components, mostly in ground equipment with some in GLV-2. This indicated that complex 

19 had not been hit directly. The damage was attributed to indirect electromagnetic effects. [Source: 

<http://history.nasa.gov/SP-4002/p2b.htm accessed 24 Mar 2010>] The strike, coupled with other problems, 

resulted in postponement of GLV-2 until 19 Jan 1965. Subsequently, Gemini-Titan-5 was also postponed 

when a similar near miss affected the onboard computers, resulting in a two day delay (Grimwood et al., 1969)

Apollo I Natural lightning immediately impacted the Apollo program. On May 25, 1966, the first Apollo 

vehicle, a full-scale mockup of a Saturn V moon mission vehicle, identical in size and weight to the 

operational vehicle, rolled from the Vehicle Assembly Building to the Launch Pad. Two days later lightning 

struck the LUT on the Mobile Launcher (ML) initiating a series of failures which ultimately caused an object 

to contact Apollo’s second stage (Durret, 1976).

The damage caused by the Apollo I accident immediately raised interest and concern about lightning and its 

hazards, especially during Apollo rollout and pad processing, and led the Apollo program to develop a weather 

infrastructure with unique sensor systems, configurations, and data exploitation techniques to mitigate the 

potential damage from natural lightning.This unique infrastructure proved to be even more valuable in a few 

years when NASA unexpectedly encountered another kind of lightning—rocket triggered lightning.

Apollo XII Through 1969, the only lightning launch constraint was “do not launch through a thunderstorm.” 

This inadequate constraint led to a rude awakening and near disaster. Any complacency with lightning was 
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shattered on 14 Nov 1969 during the ascent of Apollo XII, America’s second manned attempt to land on the 

moon. As launch time approached, a southward moving cold front was passing thru central Florida producing 

cloudy skies and rain showers. Radar indicated cumulus congestus cloud tops in the Cape area ranging from 

18,000to 23,000 feet (5.5 – 7.0 km) well above the 12,400 foot (3.8 km) freezing level. Although no lightning 

was reported in the Cape area before the launch, potential gradient measurements from the eight sensors 

(installed in the mid to late 1960s) were varying significantly thus implying rapidly and highly fluctuating 

electric fields aloft over the launch area before T-0. For example, readings at Site 8, adjacent to Launch 

Complex 39, varied from +6 to -11 (units unknown) in the 20 minutes before launch (NASA, 1970, pp12-17).

MSC Mission Control did not want to delay the launch, especially with President Nixon and wife Pat in 

attendance. Technically, the only applicable LLCC was not to fly into thunderstorms and it was not violated 

because no thunder was being heard. Nevertheless the decision was extremely unwise given the information 

available which suggested strongly that the environment was electrically active.

Thirty six seconds after liftoff at 1122 EDT, Apollo XII was jolted. As the Saturn V rocket passed through 

6500 feet (2 km) a lightning strike disconnected the service module’s fuel cells that produced power for the 

command module. This frightening event was followed sixteen seconds later by another lightning strike at an 

altitude of 14,500 feet (4.4 km). This strike upset the Command Module’s navigation system, causing 

temporary loss of the system’s stabilizing platform and denial of critical flight data to Mission Control at 

MSC. Flight Director Gerry Griffin considered an abort while experts on the affected systems considered 

alternatives. A young engineer recalled a similar anomaly during a training simulation a year earlier and 

recommended resetting a switch to restore communications. Based on this recommendation Mission Control 

told the crew; “Flight, try SCE (Signal Condition Equipment) to Aux”. Astronaut Alan Bean positioned the 

SCE switch, which was located near his seat, as instructed. That restored flight telemetry to JSC’s computers.

Fortunately, the Saturn V booster’s systems, including navigation and communications, had not been affected 

by the lightning strikes.

Because nobody in the Apollo program had anticipated that the vehicle might be struck by lightning under 

non-thundery conditions, or understood that lightning discharges could be initiated just by flying a vehicle and 

its exhaust plume into a highly electrified cloud, the first efforts were simply to understand what had happened 

to the spacecraft and whether the astronauts should be allowed to continue their mission. This responsibility 

fell to the Mission Evaluation Team at MSC and its Head, Donald D. Arabian, who quickly determined that 

permanent damage to Apollo XII was minimal and that it was OK for the astronauts to continue their mission.

Figure 2.3.1 shows a sketch of the clouds that were present at the time of the launch of Apollo XII and the 

lightning strikes that were triggered by the vehicle together with many of the weather measurements that were 

considered in the analysis of the incident (taken from Brook et al., 1970).

Appendix VI describes the timeline of events that followed the Apollo XII lightning incident and lists the 

scientific panels and reviews that provided a basis for a multi-center NASA Report in February 1970 (NASA, 

1970). The MSC report describes the weather conditions that were present at the time of the launch, the 

relevant instrumentation, and shows photos of the CG strokes that were recorded near the launch pad. It also 

describes the ways that the lightning current affected various components of Apollo XII and the mechanisms 

whereby this current caused transient upsets and damage. The report ends with a conclusion that the best way 

to avoid a similar incident in future Apollo missions is to avoid natural lightning or highly electrified clouds 

during launch rather than attempting to harden the vehicle. In order to avoid these hazards, several new 

Lightning Launch Commit Criteria (LLCC) were adopted that were based largely on the weather conditions 

under which the ESSA forecasters at KSC had previously observed high electric fields. These LLCC were 

used for the first time during the launch of Apollo XIII and continued through the launch of Apollo XVII and 

the subsequent Skylab missions.
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Post analyses of the Apollo 12 incident revealed a new danger, triggered lightning, that had not been 

previously assessed in space program meetings on procedures and constraints, but the hazard itself was already 

known to the aviation community [Fitzgerald (1967; 1970)].

Figure 2.3.1 Sketch of meteorological conditions during the Apollo XII incident

2.4 Research

As we shall see in the next chapter, the Apollo XII incident spurred a great deal of lightning research in the 

aerospace community. There had been some previous research. Measuring electric fields aloft, especially 

inside a cloud, is an extremely challenging undertaking which is difficult even today after significant advances 

in both science and technology. Nonetheless, as early as 1957, Clark (1957) measured fair weather electric 

fields as a function of altitude using four rotating-vane field mills mounted symmetrically on the wing tips and 

the top and bottom of the fuselage of a P4Y aircraft. Similarly, in the 1960s Fitzgerald (1965, 1977) used 

rotating-vane field mills mounted on C-130 and F-100 F aircraft in conjunction with a U-2 high altitude 

aircraft to measure the electric fields simultaneously above and in thunderstorms at KSC. He used symmetric 

field mill mounting and electronic compensation to minimize the effects of aircraft charging on the 

measurement of the ambient field. For one cloud Fitzgerald (1965) studied, the strongest electric field was 

associated with the region of highest radar reflectivity with the vector field apparently pointing toward (or 

away from) the centers of charge.

When considering these early works, it is important to remember that through the early 1970s, the aircraft 

measurements were being recorded on strip-chart recorders or on analog magnetic tape recorders carried on the 

aircraft or sometimes telemetered to the ground; the radar data were recorded photographically; and 

measurements of the cloud microphysics were made by subsequent analysis of particles that had impacted on 

formvar replicator films, oil-coated glass slides, a moving belt of soft metal foil, or “snow sticks” as well as 

viewing the particles impacting upon the windscreen. The enormous progress that has been made in our 

understanding of the electrical structure of thunderstorms and the associated lightning over the past 3 to 4 
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decades is mainly due to the advances that have been made in analog and digital electronics, electronic data 

storage capabilities, and display technology.

The early efforts to examine the electrification of clouds in the lower atmosphere were not limited to passive 

examination of existing terrestrial clouds. On 25 April 1962 Saturn C-1 SA-2 lifted off from Cape Canaveral 

in the second suborbital test flight of the Saturn I configuration. The payload, designated “Project Highwater”, 

was 86 tons of water ballast that was deliberately dumped into the ionosphere at an altitude of 105 km to 

determine the effects of a sudden release of a large volume of water at high altitude. The water cloud 

continued to rise on an inertial trajectory to an altitude of 145 km and expanded to several km in diameter. A 

similar test was conducted on 16 November 1962 during flight SA-3. Both tests created “lightning-like” radio 

disturbances that were recorded on the ground. [Source: http://en.wikipedia.org/wiki/Project_Highwater 

accessed 22 February 2010]
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Chapter 3 The Aftermath of Apollo XII (1969 – 1980)

3.0 The Apollo XII Investigations

The Apollo XII lightning investigation team concluded that although the Saturn V design contained safeguards 

against electrical discharges, lightning could damage spacecraft electronics such as solid-state devices. 

Nevertheless the team opposed any spacecraft modifications due to impacts to schedule, cost, and capability 

(due to added weight) but instead recommended changing the LLCC to significantly lower the risk of being 

struck by lightning again. The following month, atmospheric electricity scientists, while participating in the 

December 1969 AGU meeting, designed new rules which attempted to identify/avoid all hazardous weather 

associated with atmospheric electricity (Benson and Faherty, 1978).

NASA estimated the new Lightning Launch Commit Criteria (LLCC) would increase the probability of a 

February delay to 18% from its existing 10%, and the probability of a summer scrub to 18% from its existing 

3%. The new LLCC were used for Apollo’s remaining moon missions, and until 1988 for Expendable Launch 

Vehicle (ELV) missions (NASA, 1970).

Post Apollo 12 Lightning LCC (LLCC) 1970

Space vehicle will not be launched if nominal flight path will carry vehicle:

Within 5 statute miles (sm) of a cumulonimbus (thunderstorm) cloud;

Within 3 sm of anvil associated with a thunderstorm;

Through cold front or squall line clouds which extend above 10,000 feet;

Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

Through cumulus clouds with tops at 10,000 feet or higher.

The Apollo 12 lightning incident brought into clear focus many of the scientific questions that were still not 

understood about the small- and large-scale processes that create high electric fields inside both thundery and 

non-thundery clouds, and also about the physics of lightning discharges. Because of this attention and NASA’s 

urgent “need-to-know,“ program managers like James Hughes in the Office of Naval Research (ONR), Ronald 

L. Taylor in the National Science Foundation (NSF), and others in ESSA and NASA were able to secure 

funding to enhance their existing investigations and support new studies of the salient phenomena. 

Measurements of the optical temperature of the Apollo 15 exhaust plume showed peak values that were near 

2370 oC (Pifer and Krider, 1972), and the presence of such temperatures in the plume, combined with trace 

amounts of sodium in the fuel, had major implications for artificially-initiating or ”triggering” lightning 

(Krider et al., 1975). In section 3.4, we will review additional studies that were undertaken at KSC by a 

number of investigators both inside and outside NASA as part of the Thunderstorm Research International 

Program (TRIP).

In subsequent years, as new techniques became available for research - particularly the development of largescale integrated circuits for both analog and digital electronics - huge advances were made in computers, 

memory technology, and communications. These advances in turn led to major improvements in the ability of 

scientists to conduct experiments in atmospheric electricity, display the results, and analyze the data. As new 

knowledge became available, the LLCC were revised, updated, and improved to increase both launch 

availability and launch safety.

Among the scientific advances that were made in the early- and mid-1970s, largely as a result of the Apollo 12 

lightning incident, were the development of (a) an improved ground-based method for detecting and 

displaying cloud electric fields and (b) improved methods for detecting, locating, and displaying both 

intracloud and cloud-to-ground (CG) lightning discharges. These advances were tested at KSC and were the 

basis for many of the subsequent improvements in the LLCC.
Page 15 of 234

3.1 Infrastructure

Except as noted below in this section, the weather infrastructure at KSC/CCAFS remained the same as that 

presented in Section 2.1 during the period covered by this chapter.

During the 1970s, the CPS-9 3 cm weather radar at the Eastern Range was replaced with a 5 cm AN/FPS-77 

located atop the Range Control Center on Cape Canaveral, but this location resulted in serious RF interference 

to sensitive spacecraft (Boyd et al., 2003). This location also placed many of the launch sites within the radar 

“cone of silence” centered on the radar site. That deficit was remedied by using data from the National 

Weather Service WSR-57 radar at Daytona Beach, FL about 50 miles (80 km) north of Cape Canaveral, and 

the FPS 77 radars at KSC and Patrick AFB about 30 miles (50 km) south of the Cape.

By the mid 1970s, a network of ground-based electric field mills had been established and designated the 

Launch Pad Lightning Warning System (LPLWS), a name that continues until this day although the details of 

the sensor design have changed. For more details and a picture, see Appendix VIII, section 8.1.1. If forecasters 

observed the surface fields increasing to above fair weather values of ~200-500 V/m, and other data indicated 

the fields may continue to rise and exceed 3000 V/m, they would issue a warning for lightning within 5 nm (9 

km) as soon as needed to provide at least a 30 minute lead time before the first strike. The 3000 V/m surface 

threshold magnitude was based on theoretical and empirical data which related surface fields to the fields aloft 

required to initiate lightning. The field mill system could also be used to estimate charge center locations and 

accompanying fields, and indicate lightning was present in the local area, but could not locate lightning impact 

points.

During the early years of the LPLWS the calibration methodologies had not matured and data from this period 

was not always quantitatively precise to the degree it is today. The Secretariat of the Thunderstorm Research 

International Program (see Section 3.4.4 below) was notified of some concerns regarding the accuracy of the 

data in a letter dated 15 September 1976 (unpublished). The authors, C.C. Moore and Stephen Friberg, wellrespected scientists in the field of atmospheric electricity, had conducted a series of comparisons between 

LPLWS sensors and a portable, research grade field mill. They reported their results and made some 

recommendations for improved calibration procedures.

The use of surface field measurements to infer field strengths aloft becomes less reliable for clouds either 

above 3050 meters or not over the field mill network (Arabian, 1976, page 2). A valuable ally was a Lear jet 

stationed at Patrick AFB equipped with field mills, that could fly where required and directly measure the 

fields aloft. The Learjet’s 45,000 foot (13.7 km) service ceiling, 464 knot (240 m/s) cruising speed, 6800 

ft/min (35 m/s) climb rate, and ability to accommodate three passengers plus instrumentation made it an ideal 

platform for helping improve lightning warning accuracy.

3.2 Organization

The time between the end of the Apollo program in the mid to late 1970s and the beginning of the Shuttle 

Program early in the 1980s was a time of transition for weather support to manned spaceflight. The NWS 

responsibilities for coordinating weather support to NASA and Department of Defense (DoD) unmanned test 

ranges in the US and the Pacific that were assigned in the late 60s had ended by 1975.

By 1978, SMG operations were consolidated at JSC, and support for ground processing and launch activities at 

the Kennedy Space Center was assumed by the US Air Force at Cape Canaveral Air Force Station. SMG 

remained responsible for support to on-orbit and landing operations world-wide including Return to Launch 

Site (RTLS) landings at KSC. This division of labor has remained in place until the current time and appeared 

to have been adopted by NASA for the Constellation Program that was scheduled to replace the Shuttle 
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Program. The status of Constellation Program components such as the Orion crew capsule is uncertain at the 

time this is being written. An in-depth description of Shuttle weather support is found in Bellue et al. (2006).

3.3 Operations

3.3.1 Apollo XIV – Apollo XVI

Apollo XII was not the end of Apollo’s lightning troubles. Apollo XIV was delayed 40 minutes by 

thunderstorms near the launch pad. Apollo XV fared even worse. While it was at the pad, several lightning 

strikes damaged two spacecraft sensors and ten ground support equipment systems in June and July 1971.

Finally, lightning struck the pad twice in March 1973 but Apollo XVI remained undamaged thanks to 

mitigation techniques adopted after Apollo XV.

3.3.2 Skylab

Five months after the last Apollo moon mission, Apollo XVII, the first Skylab mission launched on 14 May 

1973. Skylab 1 was an unmanned mission that was followed by four manned Skylab Station missions. The 

Skylab LLCC were identical to the new post Apollo 12 LLCC, except Skylab combined the first two criteria 

into one rule.

Skylab (1973) LLCC (Arabian, 1976)

Space vehicle will not be launched if nominal flight path will carry vehicle:

• Within 5 sm of a cumulonimbus (thunderstorm) cloud or within 3 sm of an associated anvil;

• Through cold front or squall line clouds which extend above 10K feet;

• Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

• Through cumulus clouds with tops at 10,000 feet or higher

Skylab 2: Natural lightning problems during ground processing operations, similar to those which had 

threatened Apollo’s XIV, XV, and XVI, continued with the remaining three Skylab missions. Lightning struck 

Skylab 2’s launch facility structure damaging four spacecraft sensors in May 1973. Then thunderstorms, which 

had continued from the previous day into the night and morning hours, threatened Skylab 2’s countdown.

However by launch time they were far enough west to allow a safe launch.

Skylab 3: Lightning struck the launch pad damaging ten spacecraft sensors, eight ground sensors and three 

ground service equipment (GSE) systems in June 1973.

Skylab 4: Among other equipment, a 200KA strike damaged the guidance and navigation inertial 

measurement unit, a signal conditioner and four spacecraft sensors in August 1973 (Arabian, 1976).

3.3.3 The Apollo-Soyuz Test Project (ASTP)

The ASTP deserves special attention and is discussed at length here. The triggering of lightning by Apollo 12 

in 1969 alerted the community to the threat of launch vehicles (and their ionized exhaust plumes) triggering 

lightning when launched into clouds containing strong electric fields. This in turn, raised questions about 

which clouds produce these fields and where these fields are located inside those clouds, particularly at the 

Kennedy Space Center where thunderstorms and lightning are frequent. Plans had been made for an earthorbiting rendezvous of an Apollo vehicle with a Soyuz vehicle to take place in July 1975. Both launches were 

planned to take place on the same day. The Soyuz vehicle would launch first from the Soviet Union, and if that 

was successful, the Apollo would launch 7 1⁄2 hours later from KSC. Because of the low Earth orbit, the timewindow for a successful Apollo launch was only 5 - 8 min (Arabian, 1976), and it needed to take place at 3:50 

PM local time on July 15, the diurnal maximum for lightning at KSC in a month of peak lightning activity.

Given the international politics of that era, NASA felt intense pressure that this Apollo launch not be delayed 

unless it was absolutely necessary (Kanter, 1975). At that time, a large network of surface electric field sensors 

was in place at KSC to identify impending lightning hazards to space vehicles, but “very little data were 
Page 17 of 234

available to correlate the field intensities aloft to those measured at ground level”. Consequently a research 

program was conducted jointly by KSC and NOAA using four aircraft to make airborne electric field 

measurements at different altitudes in clouds over the surface network (Arabian, 1976). The four aircraft were 

the New Mexico Institute of Mining and Technology (NMIMT) Schweizer powered glider instrumented with 

rotating-vane field mills, a NOAA T-29 aircraft instrumented with 2 cylindrical field mills, one on the nose 

and one atop the fuselage (Kasemir, 1972); a NRL/NOAA S-2D instrumented with 2 cylindrical field mills, 

and a NASA C-45 (NASA 6) instrumented with 2 cylindrical mills. The C-45 was also equipped to dispense 

chaff if it was necessary to reduce the electric fields over the launch path just before the Apollo launch. The 

results from the aircraft study “indicated that, below an altitude of 3050 meters, the airborne data compared 

favorably with the ground instrumentation. Above this altitude, however, the ground-based sensors could not 

be relied upon to provide an accurate measurement of the electric field intensities aloft” (Arabian, 1976). 

Therefore airborne measurements of electric field were deemed necessary to support the Apollo launch.

In order to be able to measure the electric field along the entire portion of the flight path of the Apollo vehicle 

where it might be subject to lightning strikes, four aircraft in addition to those used in the KSC/NOAA study 

were used: A NASA/Ames Learjet and a NASA/JSC T-38, both instrumented by the Stanford Research 

Institute with rotating-vane field mills, an Air Force C-130 instrumented with rotating-vane mills by Air Force 

Cambridge Research Laboratory (AFCRL) and a RF-4C from Kirtland Air Force Base instrumented by the Air 

Force Weapons Laboratory. A detailed flight pattern with exit and entry points for all aircraft was worked out 

for the hour immediately preceding the launch. The flight pattern and altitude assignments of the eight aircraft 

are shown in figure 3.3.3-1.

Figure 3.3.3-1 Flight plan to determine electric fields prior to the Apollo-Soyuz Test Project

Note: [Reproduced from Arabian, 1976]
Page 18 of 234

For the 10 days prior to July 15 there had been thunderstorms every afternoon with much rain and lightning, 

some hail and even one tornado, but the evening before the scheduled ASTP launch the prevailing winds 

changed from southwest to southeast. This greatly reduced the potential for thunderstorms at the time of the 

launch. Although there were showers in the early afternoon on July 15 (Kanter, 1975), the launch proceeded 

on schedule at 3:50 PM local time (Arabian, 1976).

The conclusions drawn from these studies and from the multiple aircraft instrumented for the ASTP launch 

were that launch delays due to the presence of clouds could be avoided by measuring the electric field aloft 

along the flight path just prior to launch using multiple instrumented aircraft and that further research was 

required to characterize the electrical properties of various cloud types (Arabian, 1976).

The ASTP launch rules were as follows (Heritage, 1988, page 4-4):

Apollo-Soyuz Lightning LLCC 1975

Space vehicle will not be launched if the nominal flight path will carry vehicle:

A. Through a cumulonimbus (thunderstorm) cloud;

B. Within 5 sm of a cumulonimbus (thunderstorm) cloud or within 3 sm of an associated anvil. This rule 

may be relaxed at the discretion of the Launch Director if the electric field at the launch pad is less 

than 1 kV//m with a very narrow launch window

C. Through cold front or squall line clouds which extend above 10K feet;

D. Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

E. Through cumulus clouds with tops at 10,000 feet or higher;

F. Rules C, D, and E above may be relaxed at the discretion of the Launch Director when electric field 

measurements in the launch pad area are stable and measure less than 1 kV/m. [Editor’s note: It 

seems likely that the 1 kV/m threshold was only for a foul-weather polarity field. Explicit use of the 

absolute value of the electric field was not made in the operational rules until 1991.]

G. Rules C, D, and E above may be further relaxed provided that airborne and ground electric field 

measurements are less than or equal to 3 kV/m at the surface and less than or equal to a vertical 

profile of electric field, EC(H), where EC(H) varies linearly from 3 kV/m at the surface to 15 kV/m at 

25K feet and remains constant above that altitude. This rule may be applied only if vertical field 

measurements along the flight path in a 3-mile area are within the described envelope and there are 

no rapid fluctuations of about 3 kV/m at about 1 minute intervals within the 3 mile area measured by 

the ground mills.

3.3.4 The Viking Missions

The two launches of Viking spacecraft that took place shortly after the ASTP launch took advantage of three 

legacies of ASTP.

1. The modified LLCC developed for ASTP and shown above.

2. The improved field mill network and display and the improved lightning detection capabilities at 

KSC/CCAFS.

3. Three of the aircraft (NASA 6, the NOAA T-29, and the NRL/NOAA S-2D) used during ASTP for the 

airborne measurements of electric field aloft remained for the Viking launches.

Although the documentation of the LLCC at the time of the Viking launches is unfortunately incomplete, we 

are including a discussion of the Viking missions because it demonstrates historically the extent to which 

personnel in the space program at that time attempted to use new measurement techniques and scientifically 

based approaches to provide safety while still not being overly restrictive. Although there were airborne 

measurements of electric fields prior to launch, as for the ASTP, the aircraft were required to depart the launch 

area no later than T minus 5 minutes (Arabian, 1976, p. 9). This left a 5 minute time-gap without airborne 

electric field measurements. However, there were continuous measurements of the surface electric field from 
Page 19 of 234

the field mill network, so Heinz Kasemir and colleagues at NOAA used the surface measurements to develop a 

probabilistic technique for forecasting the movement of the electric field contours that were measured at the 

surface. (W. D. Rust, personal communication).

There was only a short time to do the research and develop the techniques for interpreting the surface electric 

field measurements. The main objective was to devise some sort of observationally-based prediction technique 

that could forecast when high electric fields moving into the launch area would result in natural or triggered 

lightning. For the ground-based data, the criterion was the probability that a 1-kV/m contour line would reach 

a five-mile radius around a launch pad, which was the demarcation distance of a no-go for launch. The 

electrical state of the atmosphere in the pad area was to be evaluated continuously, but with specific emphasis 

on both ten minutes and five minutes before the scheduled launch. As far as we are aware, no documentation 

remains that describes the details of this technique.

It was decided to support the upcoming Viking launches using this probability prediction technique. The 

NOAA/Environmental Research Laboratory/Atmospheric Physics and Chemistry Laboratory in Boulder, 

Colorado, provided an advisor, W. David Rust, who had experience in measuring atmospheric electric fields. 

The main responsibility of the NOAA advisor was to inform the KSC weather office if a no-go 

recommendation for launch was needed given the electrical state of the atmosphere at the time. (W. D. Rust, 

personal communication)

Viking 1 was under pressure to launch on-time due to the goal of landing on Mars on the 4th of July 1975 as a 

major bicentennial event. The launch window was only seconds long due to the planetary trajectory, and this 

window was on a summer afternoon at the peak of normal thunderstorm activity. The vehicle was launched on 

20 August 1975 through thick middle clouds with temperatures approaching the freezing level (Durret, 1976).

Even though there were thick mid-level clouds, the launch was permitted because the electric field 

measurements aloft and at the surface were at acceptable levels. (Arabian, 1976, p. 14)

Viking 2 was launched from pad 41 on 9 September 1975 through opaque clouds that were estimated to be at a 

height of 2450 meters (8100 feet) (Arabian, 1976, p. 14). Large convective storms had developed offshore and 

were moving from the east toward the launch site. There were also thunderstorms over land to the west of the 

launch site. Just a few minutes before the scheduled launch, it was not clear whether a 1-kV/m contour of the 

surface field measurements would reach the 5 mile demarcation distance and create a ‘no-go’ condition for 

launch. The NOAA advisor used the rudimentary prediction technique and recommended go-for launch, and it 

was successful. The situation that existed shortly after the time of launch is depicted in Figure 3.3.4-1 below.

In the figure, the 1-kV/m threshold is the outer most contour of the electric field. Additional contours are 

probably at 1 kV/m intervals. Electric field polarities are reported using the potential gradient sign convention, 

i.e., E = -grad V. It is likely that for the ASTP and Viking launches, only foul weather polarity fields (negative 

in this plot) were considered when applying the LLCC. Thus the single positive contour line near pad 41 did 

not delay the launch. Outlines of the radar reflectivity from a base-level scan (reflectivity factor unavailable) 

are shown as white clouds and the radar-derived cloud tops are as indicated.

About a minute after launch, lightning occurred off the coast nearby. Shortly thereafter, the pad 41 area went 

red and remained so for a significant time. Both the Viking 1 and Viking 2 launches are examples of the 

usefulness of real-time electric field measurements aloft and at the surface for optimal launch support.
Page 20 of 234

Figure 3.3.4-1 Contours of the electric field at the ground shortly after the launch of Viking 2

3.3.5 Atlas Centaur 38 (AC 38)

Although the manned spaceflight program continued to refine its launch criteria to safely avoid triggered 

lightning, the ELV community, for unknown reasons, continued to rely only on the launch criteria developed 

immediately (just one month) after Apollo 12. AC 38 illustrates a close call with the near catastrophic 

consequences (later realized in the destruction of AC 67) that can result from using faulty LLCC or faulty 

implementation procedures. In preparing this history, only one AC 38 source document could be located, a 

memo by James Nicholson that discusses the weather assessments during AC 38 [Source: Memo for Record, 

Date: 28 May 1976, Subject: “Consultative Support for Atlas-Centaur Launch 13 May 76”, Signed: James R 

Nicholson.]. Mr. Nicholson is personally known to several of us as a very professional and credible source. His 

memo is summarized below.

Background: At the time of AC 38 (13 May 1976), the Air Force provided weather support for CCAFS and the 

NOAA/National Weather Service (NWS) provided weather support for KSC. The memo was written by a 

NWS forecaster based on the telephone conversations he and another NWS forecaster had with the Air Force 

Launch Weather Officer (LWO). The Post Apollo 12 Lightning LCC (LLCC) which governed AC 38 were 

provided at the end of section 3.0 above.

Significant points in the NWS memo:

1. AF and KSC field mills were different with different scales. Field mills from the two networks had 

never been collocated to calibrate the differences. Thus NWS did not understand how to compare 

Range electric field mill readings with KSC readings to determine if the AF sensors were exceeding 

the NASA LLCC.

2. Although the AF field mill network was operational, the KSC field mill network was down which 

denied the AF important upstream electric field data.
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3. The NASA 6 aircraft was not available for weather reconnaissance.

4. Cumulus began growing late morning into towering Cumulus tops 22,000 feet (6.7 km) by 1145 EDT, 

and a thunderstorm near Cocoa at 1230 EDT top 44000 feet (13.4 km) drifting slowly ENE and 

eventually over into Port Canaveral. Convection over Merritt Island eventually shifted from line just 

W of KSC to along I95 sending Anvil clouds and Mammatocumulus over KSC and CCAFS from 

1600EDT thru the 1828 EDT launch. At 1800 EDT radar indicated clouds over LC 39 had bases 

~15000 feet (4.6 km) with tops to 33000 feet (10 km).

5. When the Range informed NWS at T-20 minutes (1740EDT) that the launch would occur at the 

scheduled time (1800 EDT), NWS expressed concern about: A. Anvil clouds overhead; B. Layer of 

Mammatocumulus which in their past experience had been associated with disturbed cloud electric 

fields; and C. Radar observations of convection. Thus NWS recommended not launching.

6. AF LWO said electric fields were disturbed but ‘seemed to be quieting down’.

7. 1755EDT: Range delayed launch due to weather.

8. 1820 EDT: AF LWO recommended the Range proceed with launch

9. NWS replied radar observations indicated vertical thickness of echoes ‘seemed to be decreasing in 

vicinity of Launch Pad 36. Memo did not mention if NWS had withdrawn their recommendation not 

to launch.

10. 1821 EDT: NWS detected lightning strike at 040 degrees. Based on thunder, strike was estimated at 

10-12 miles distant.

11. 1828 EDT: Successful launch T-0 Observation: 3/10 CB @3000ft (914 m), 5/10 AC @13,000 ft (4 

km), 5/10 AC @18,000 ft (5.5 km).

12. LWO tells NWS: A. AC 38 entered clouds ~20,000 feet (6.1 km). B. AF field mills were reading 12 

kV/m which he guessed would translate to ~3 KV/m for KSC mills (thus significantly exceeding the 

NASA threshold of 1kV/M).

13. 14 May 1976 (next day): Weather Commander shows NWS a running time plot of field mill 

observations (a strip chart). NWS assesses plot as ‘indicating disturbed atmospheric (electrical) 

conditions as one would expect from visual observations of clouds’.

14. Weather Commander mentions a TV camera filming the launch showed a lightning flash descending 

part way to ground, about 6 seconds after vehicle entered the cloud base.

3.3.6 F11 Europa II

During the Apollo era, the Europeans were having their own problems with hazardous electrical discharges 

that had a different cause—triboelectrification. Although this History is based on the American space program, 

it cannot be completely separated from the world at large, and the Europa incident described here illuminates a 

significant oversight in the American program at the time. F11 Europa II was launched on 5 November 1971 

during benign weather. At T+105 seconds and at 27 km altitude, the launcher lost its attitude control because 

the guidance computer in the rocket’s third stage had ceased to function. Other electrical anomalies lasting 

about three seconds occurred at the same time. Less than a minute later, the resulting stresses on the first and 

second stages caused them to explode. This catastrophic accident led to the cancelation of a major European 

cooperative program.

The resulting investigation concluded electrostatic discharge caused the accident and identified three different 

mechanisms that could build up excess charge on a booster:

1. Electrostatic induction could cause significant charge to accumulate on the vehicle before launch if the 

environmental field is high, for example due to a nearby electrical storm. The vehicle will then carry 

the charge aloft where it will discharge in the lower atmospheric pressure.

Conclusion: Ruled out because this model does not explain the observed series of discharges; and 

because the weather was benign.

2. The vehicle could become charged by friction due to collisions with snow, ice, and/or cloud particles.
Page 22 of 234

Conclusion: Ruled out because of the good weather, and because encountering ice and snow particles 

at 27 km is rare.

3. The vehicle could become charged because negative and positive ions in the hot booster exhaust have 

different mobilites and will cause a charge separation and drain current to the metallic nozzle wall.

Conclusion: Accepted as the cause based on thorough testing and the agreement of results with models 

and theory. For a thorough explanation of the causes of this accident see Taillet (1974).

Despite the Europa failure and the fact that electrostatic charging was cited as the cause of two Minutemen 

failures, two Titan guidance anomalies, and the likely cause of two Scout failures (Andrus et al., 1969), the 

American Space Program did not introduce electrostatic charging and triboelectrification into its LLCC until 

the 1988 post AC 67 revision. The 1988 Triboelectrification rule recommended by the LAP only addresses 

collisions with cloud particles (as in Cause 2 above). The LLCC prohibited flight thru clouds at altitudes 

colder than – 10 °C unless the vehicle has been treated for a resistivity of no more than 10 -9 ohms per square.

Nanevicz (1973) established 6 x 10-9 as the threshold and the Heritage Committee reduced it to just 10- 9 ohms 

per square to allow for drift in surface resistivity and other uncertainties.

3.4 Research

3.4.1 Attempts to Reduce Lightning

The early 1970s was a period when much effort, both research and operational, was being put into cloud 

modification in order to increase precipitation and/or reduce the damage from hail storms. One area that was 

also being pursued was an attempt to reduce lightning by seeding clouds with conducting chaff needles. 

Holitza and Kasemir (1974) and Kasemir et al. (1976) reported on studies to reduce the electric field and 

lightning in small thunderstorms in eastern Colorado and Wyoming. In principle, the sharp points on the chaff 

would go into corona in strong electric fields and thereby reduce the fields inside the storm. Both seeded and 

control clouds were investigated. For these studies, a B-29 aircraft was instrumented with two cylindrical field 

mills (Kasemir, 1972), one on the nose and one on the top of the fuselage over the wings to measure the 

electric fields in the storms. The initial experiments suggested that the electric field at cloud base decayed 

about five times faster in seeded storms than in control storms (Holitza and Kasemir, 1974). Additionally, the 

number of lightning events decreased to one-third or less of those in the control storms (Kasemir et al., 1976).

3.4.2 Russian Research

The early development of LLCC for hazards in stratiform clouds was hampered by the lack of published data 

inside those clouds in the western scientific literature. In contrast, and ultimately fortunately, there were a 

large amount of in-storm electric field data in several reports from scientists in the USSR. It was difficult for 

the US space program to rely upon the USSR data because American scientists had no first-hand knowledge 

about its quality. Because the senior Russian scientist, I. M. Imyanitov, was favorably perceived by western 

scientists in atmospheric electricity, however, it was ultimately decided to use the Russian data. At some time 

during the process of interpreting and using the data, there was a controversy over the maximum electric field 

strength within stratiform clouds. The issue was finally resolved when it was discovered that the units of 

electric field, e.g., volts per meter, were incorrect in some of the translated text. Once everyone understood 

that there was a translation error, it was decided to correct the units and the data for the LLCC.

The following are short descriptions of various stratiform cloud genera from the Glossary of Meteorology 

(Glickman, 2000):

• Stratus – a gray cloud layer with a rather uniform base.

• Stratocumulus – predominantly stratiform in the form of a gray or whitish layer or patch, which nearly 

always has dark parts and is non-fibrous (except for virga)

• Altocumulus – a gray or bluish (never white) sheet or layer of striated, fibrous or uniform appearance, 

and may be precipitating.
Page 23 of 234

• Nimbostratus – gray colored and often dark, rendered diffuse by more or less continuously falling rain, 

snow or sleet and not accompanied by lightning, thunder or hail.

Over two decades, I. M. Imyanitov and his colleagues studied stratiform clouds in the USSR, mainly at three 

locations with different latitudes: Leningrad (St. Petersburg) at approximately 60 °N latitude, Kiev at 50 °N, 

and Tashkent at 41 °N. Stratiform clouds were examined from the perspective of vertical profiles of the 

electric field obtained with instrumented airplanes. The data that Imyanitov and colleagues summarized came 

from about 900 spiraling ascent soundings up through clouds to 6 km MSL. Imyanitov et al. (1971) reported 

each data point to be an average of 100 m vertically from a climb rate of about 4 m s-1

, and 3 km horizontally 

from a horizontal speed of about 50 m s-1

. The observations in the USSR showed that in general the maximum 

electric field increases as the cloud genus moves from stratus (St) to stratocumulus (Sc) to altostratus (As) to 

nimbostratus (Ns). Furthermore, within a genus, thicker clouds tended to have larger maximum electric field.

The average maximum electric field for these genera (at 60 °N) was larger in the summer than in the winter by

factors ranging from about one to seven. A summary of the Russian observations of the electrical structure of 

stratiform clouds is also available in MacGorman and Rust (1998, sections 2.1-2.3). What is clear from the 

Russian data is that stratiform clouds can be electrified, sometimes highly for clouds with thicknesses of 2000 

m or greater, and thus, they do pose a significant threat to space vehicles flying in them or in their vicinity.

3.4.3 Post-ASTP Airborne Experiments

After the ASTP mission, because of the unique capabilities of the Learjet to climb with the tops of growing 

cumulus clouds and to fly at or above anvil altitudes, arrangements were made for the NASA/Ames Learjet 

instrumented by Stanford Research Institute to remain at Patrick Air Force Base for the summer of 1975 to 

make high altitude electric field measurements. The Learjet was flown around developing thunderstorms cells 

to study the fields in the vicinity with particular emphasis on the region of the anvil. Most of the measurements 

started when a cell was very young and followed the development throughout the growth period and continued 

until it began to disintegrate (Arabian, 1976). Measurements were gathered from ten different storm cells.

The Learjet had flight capability to 45,000 ft (13.7 km), cruise speed of 240 m s-1 and climb rate of ~2000 m 

min-1

. Four rotating-vane mills were installed on the NASA/Ames Learjet and were calibrated by measuring 

the potential at the location of each mill on a model of the aircraft in an electrostatic cage. Appendix C of 

Arabian (1976) gives a general discussion of the measurement of electric fields from aircraft as well as a brief 

discussion of the calibration of the Learjet. The procedure is most probably an early version of Kositsky et al. 

(1991).

Isolated storm cells were selected for study so that measured electric fields were not affected by nearby storms. 

They also wanted to avoid unsafe flying conditions and wanted to insure level flight for making the 

measurements (Arabian, 1976). The position of the aircraft measurements could be related to ground-based 

radar observations. Apparently in-cloud measurements were not made. From a limited analysis of the data 

from these storms, Arabian (1976) stated that the high electric fields observed in the vicinity of the anvils were 

most likely associated with charge concentrations in the thunderstorm main vertical body. An example taken 

from Arabian (1976) is shown in figure 3.4.3-1 below. Because the aircraft was flying in clear air it is likely 

that the electric fields observed above the anvil are less than those that would have been observed inside the 

anvil because of the effects of screening layers.
Page 24 of 234

Figure 3.4.3-1 Measurements of electric field around a thunderstorm

Note: Measurements are from the NASA Ames Learjet [Reproduced from Arabian, 1976]

In the weeks following the ASTP launch, a NOAA study was undertaken using the C-45, the S2-D and T-29 

aircraft to investigate how effectively electric fields might be reduced by the release of chaff into Florida 

thunderstorms (Rust et al., 1977). The sample size was small, but the initial results were not promising, 

probably because Florida storms are larger and more complex than the small storms that were studied in 

Colorado and Wyoming by Holitza and Kasemir (1974).

3.4.4 Thunderstorm Research International Project (TRIP)

As a result of the Apollo XII triggered lightning event, NASA encouraged and supported a number of 

collaborative experiments at KSC involving several different groups of atmospheric scientists . These efforts 

were primarily intended to define the meteorological conditions under which rockets would trigger lightning 

and to understand better the characteristics of Florida lightning. They culminated in an intensive series of 

ground and airborne measurements that were conducted prior to and during the Apollo/Soyuz Test Project (see 

section 3.3.3). After those experiences, NASA was well aware of the mutual benefits of collaborative efforts 

and issued an invitation to the atmospheric electrical community to participate in a new series of investigations 

at KSC during the summers of 1976, 1977, and 1978. In December, 1975, this opportunity was enthusiastically 

grasped by the scientists in atmospheric electricity who attended the Fall Annual AGU Meeting in San 

Francisco.

A very loose organization for the coordinated studies emerged during and after that AGU meeting. There were 

three overall components [Pierce, 1976]:

1. Principal Investigators (PIs). Each PI brought his own equipment, furnished his own financial support 

for personnel, etc., and made his own measurements.

2. Technical support group from KSC. This group assisted the PIs by providing sites for the experimental 

equipment and some basic facilities at those sites and elsewhere. The facilities included shelter, 
Page 25 of 234

electric power, air conditioning, timing, telephone, and other linkages. Thus, data obtained by different 

investigators/techniques could be compared and the characteristics of different physical parameters 

could be correlated.

3. Secretariat. The secretariat comprised Dr. L. H. Ruhnke and Dr. E. T. Pierce. Dr. Ruhnke's main 

function was to act as an interface facilitating communications between the PIs and the KSC technical 

support group. Dr. Pierce's role was to describe the project(s) to the outside scientific community and 

to coordinate the interpretation and presentation of the scientific results. The organization was 

essentially cooperative, i.e. there was no formal structure and neither the Secretariat nor the KSC 

support group had any directive powers over the PIs. However, the PIs were expected to accept that 

the generous site support provided by KSC was limited, that no individual investigator could claim an 

excessive share of this support, and that any conflicts between PIs over, for example, experimental 

compatibility, must be resolved cooperatively.

The International Commission on Atmospheric Electricity (ICAE) is a topical commission within the 

International Association of Meteorological and Atmospheric Physics (IAMAP). The ICAE had been 

advocating coordinated thunderstorm investigations for several years, and all three officers of the ICAE were 

already participating in the work at KSC. Prof. John Latham (President, ICAE) was a Principal Investigator, 

and Dr. Lothar Ruhnke (Secretary, ICAE) and Dr. E. T. Pierce (Honorary President, ICAE) were the 

Secretariat. During the Fifth International Conference on Atmospheric Electricity held in GarmischPartenkirchen, Germany, 2-7 September 1974, the ICAE passed a unanimous resolution supporting a new 

thunderstorm project at KSC [Dolezalek and Reiter, 1977, p. 809]. Because of this international approval and 

likely participation and because "program" represented the informality of the organization better than 

"project," the preferred description for the cooperative thunderstorm studies at KSC was the Thunderstorm 

Research International Program, which had a convenient acronym, TRIP.

Perhaps the greatest experiment within the TRIP was the concept of a coordinated study itself. The basic idea 

was that the combination of results obtained by different investigators, studying the same storms at the same 

time and in the same place, would provide much more valuable scientific information than the identical 

investigations conducted independently on different storms and in different locations. Clearly, such 

collaboration could only happen if there was a host organization (like KSC) that needed the information and 

could provide technical support such as power, telephone, timing, etc. Also, there had to be enthusiastic 

investigators who were ready and willing to share their data freely on a voluntary basis.

The first TRIP experiments were held at KSC in the summer of 1976 and involved about 70 scientists in 19 

different research groups [Pierce, 1976]. Subsequent campaigns were held at KSC during the summers of 1977 

and 1978, and at the New Mexico Institute of Mining and Technology in Socorro in 1979-1981. Publications 

describing the results of these investigations have been summarized in numerous review articles and books on 

atmospheric electricity and related topics such as Uman et al. (1975); Mason and Moore (1976); Rust and 

Krehbiel (1976); Uman (1976); Dolezalek and Reiter (1977); Gaskell et al. (1978); Uman et al.,(1978); Cotton 

(1979); Illingworth and Krehbiel (1981); Hallett (1983); Lhermitte (1979); Lhermitte and Krehbiel (1979); 

Gaskell and Illingworth (1980); Latham (1981); Volland (1982); Lhermitte and Williams (1983), Uman 

(1983); Golde (1977), Uman et al. (1978); Parker and Kasemir (1982); Volland (1982), Uman and Krider 

[1982}; Volland (1982); Illingworth (1985); Williams (1985); Krider and Roble (1986); Uman (1987); Latham 

and Dye (1989); Uman and Krider (1989); Williams (1988, 1989) and others.

3.4.5 Sensor Development

As new techniques became available for research - particularly the development of large-scale integrated 

circuits for both analog and digital electronics - huge advances were made in computers, memory technology, 

and communications. These advances in turn led to major improvements in the ability of scientists to make 

measurements in atmospheric electricity, display the results, and analyze the data. As new knowledge became 
Page 26 of 234

available, the Lightning Launch Commit Criteria (LLCC) were revised, updated, and improved to increase 

both launch availability and launch safety.

Among the scientific advances that were made in the early- and mid-1970s, largely as a result of the Apollo 12 

lightning incident, were the development of (a) an improved ground-based method for detecting and 

displaying cloud electric fields and (b) improved methods for detecting, locating, and displaying both 

intracloud and cloud-to-ground (CG) lightning discharges. These advances were tested at KSC and were the 

basis for many of the subsequent improvements in the LLCC.

3.4.5.1 Launch Pad Lightning Warning System (Field Mill Network)

The LPLWS is basically a large-area network of electrostatic field sensors (field mills) that measures the 

vertical component of the electrostatic field, E, produced by cloud charges aloft, even if those clouds are not 

producing lightning. The sensors are termed ‘mills’ because they employ a rotating and grounded metallic

shutter to alternately cover and uncover a set of insulated stators that respond to E. The amplitude and phase of 

the AC current flowing to and from the stators is proportional the amplitude and polarity of the local electric 

field. When an electrified cloud forms overhead or moves into the region from somewhere else, the E field will 

increase in magnitude and often change polarity. In most cases, E will be large close to the cloud charges and 

small farther away, so 2-dimensional maps of E will show approximately where the cloud charges are located.

If the cloud electric field is measured in conjunction with a weather radar that senses precipitation, the onset of 

the electric field can be compared with the onset and type of precipitation, the rate of echo growth, and the 

time-evolution of the cells, thereby improving both the nowcasting (i.e. detection) and forecasting of high 

fields aloft. When lightning discharges occur, maps and analyses of the lightning-caused changes in E, or ΔE, 

can be used to determine an approximate location (in 3-dimensions) of the change in the cloud charge (Maier 

and Krider, 1986; Koshak and Krider, 1989; Krider, 1989).

The unique features of the LPLWS are its large area (approximately 20 x 30 square kilometers), the number of 

field mills (25 to 33), and the fact that each sensor is mounted (and calibrated) in the same way on uniform 

sites that are cleared of vegetation. A network such as this minimizes the frequency of false alarms, such as 

might be caused by a single sensor having an incorrect reading, and also any ‘failures-to-warn’ that might 

occur if the positive and negative cloud charges are not vertically aligned or if the field seen by a single sensor 

is masked by intervening space charge. Further details on the implementation and calibration of the LPLWS at 

the KSC-ER are given in Appendix VII by Michael W. Maier.

Among the first scientific studies that were based on the field mill network were analyses of the electrostatic 

field changes produced by Florida lightning by Jacobson and Krider (1976) and the overall behavior of E 

under both small and large storms at KSC by Livingston and Krider (1978). These studies showed that the 

charge centers inside Florida storms are located at altitudes where the air temperatures are below freezing, i.e. 

where the environmental temperatures are between about -10 oC and -20 oC, and that the time-average values 

of E are often surprisingly small when averaged over five minute intervals, even under active storms. The 

finding that the lightning charges are located at subfreezing temperatures lent support to the idea that a noninductive ice-ice collision process is the dominant microphysical mechanism in cloud electrification 

(Saunders, 1988; 2008), and the LLCC still rely on this assumption.

3.4.5.2 Cloud-to-Ground Lightning Surveillance System (CGLSS)

KSC has made major contributions to the development of two complementary systems for detecting and 

locating lightning, the Cloud-to-Ground Lightning Surveillance System (or CGLSS) and the Lightning 

Detection and Ranging (or LDAR) system. The CGLSS utilizes a network of gated, broadband electric and 

magnetic field sensors (Krider and Noggle, 1975) to detect the waveform signatures that are characteristic of 

return strokes, the high-current components of CG flashes (Krider et al, 1976; Herrman et al., 1976). When a 

proper signature is detected (in the time-domain) at two or more known locations (the antenna sites), the 
Page 27 of 234

coincident times-of-arrival and magnetic directions can be used to compute the point where a return stroke 

strikes the ground (Krider et al., 1980; Cummins et al., 1998; 2006).

According to a time-domain antenna theory developed by M. A. Uman and his collaborators shortly after the 

Apollo 12 incident (see for example Uman et al., 1975), the initial peak of the electromagnetic pulse that is 

radiated by a return stroke is proportional the peak current in the stroke, multiplied by the speed of the stroke 

propagating up the leader channel, and divided by the distance to the stroke. [Note: this theory is sometimes 

called the simple ‘Transmission-Line Model’ or TLM because it assumes the current pulse propagates up a 

straight channel, without distortion, and at a constant speed.] Since the CGLSS measures the peak field and 

can compute the stroke location, and since the stroke velocities are known and roughly constant, the CGLSS 

can also provide an estimate of the peak current in the stroke and its polarity.

The first CGLSS system was installed at the KSC-ER between 1 June 1979 and 12 July 1979. It was a 

prototype consisting of three medium-gain magnetic direction-finders (DFs) and was installed as part of the 

Federal Evaluation of Lightning Tracking Systems (FELTS). This system was subsequently purchased in 

February 1981 with joint funding provided by NASA and the Air Force. Later upgrades were performed as 

described in Chapters 4 and 5.

3.4.5.3 Lightning Detection and Ranging (LDAR) System

The first LDAR system was developed at KSC by Carl Lennon and associates after a design described by 

Proctor (1971). It contained seven broadband VHF radio receivers that were deployed at the sites shown in 

Figure 3.4.5-1 and were precisely time-synchronized, initially using microwave communications links and 

later GPS timing. Each site received VHF radiation at 66 MHz, logarithmically amplified the signal, and then 

transmitted the time and key signal parameters to a central station where the source locations were computed 

[Lennon and Maier, 1991; Maier et al., 1995]. The 3-D locations of the sources of lightning VHF pulses are 

computed using the differences in the times-of-arrival of the signals detected at the different receiver sites. 

Since the main sources of VHF radio emissions are the processes associated with air breakdown, the LDAR 

system detects primarily the in-cloud portions of CG flashes, leader processes, and intracloud discharges. 

Today each LDAR receiver site operates automatically and is powered by batteries that are recharged by solar 

panels. The first LDAR system was developed by the KSC Instrumentation and Measurements Branch, and the 

current one is operated and maintained by the ER Technical Services Contractor. The 45 WS receives and 

evaluates the LDAR data 24 hours a day, 7 days a week. For further details on the evolution of the LDAR

system and other instrumentation at the KSC-ER, see Boyd et al. (1995), Harms, et al.(1997; 1998; 2001) and 

Roeder et al.(1999).
Page 28 of 234

Figure 3.4.5-1 KSC LDAR Sites

3.4.5.4 U.S. National Lightning Detection Network (NLDN)

Data from the U.S. National Lightning Detection Network (NLDN) (Cummins et al., 1998, 2006; 

Cummins and Murphy, 2009) have been used to detect and track CG lightning flashes beyond the 

range of the CGLSS and LDAR systems since the early 1990s. The NLDN sensors are similar to 

those used in the CGLSS except that they have higher gains and larger distances between the sensors. 

The coincident data from two or more sensors are collected and processed in real-time by a network 

control center in Tucson, Arizona, and the GPS time, location, and polarity of each lightning stroke, 

together with an estimate of its peak current, are provided to the KSC-ER in real-time. For further 

information about the NLDN and its history, see Cummins and Murphy (2009).
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Chapter 4 The Space Shuttle Era Begins (1981 – 1987)

4.0 Background

The Space Shuttle Program initially attempted to design a vehicle to withstand lightning and thus avoid the 

restrictiveness of the LLCC. However testing and analyses were not yet complete when Shuttle began its flight 

test phase in 1981, thus Shuttle initially adopted many of the post Apollo 12 LLCC (Heritage, 1988, para4-4, p 

4-6.), although with modifications. The first Shuttle-specific LLCC (1979) read as follows (Heritage, 1988,

Table 4-3; Kapryan (1978)]:

Original Space Shuttle LLCC 1979

Space vehicle will not be launched if nominal flight path will carry vehicle:

• Through a cumulonimbus (thunderstorm) cloud; 

• Within 5 sm (7.8 km) of a cumulonimbus (thunderstorm) cloud or the edge of an associated anvil that 

is within 5 sm of its radar cell. At the discretion of the Launch Director the anvil may be penetrated if 

the static electric field is less than 1kV/m and the 5 sm rule is maintained. 

• Through or within 5sm of any other clouds where radar shows virga or precipitation and tops extend 

(or will extend at the time of launch) above the -10C temperature altitude and four or more field mills 

within the launch site have changed more than 500 V/m.

• Through single layer clouds in the dissipation stage and where these clouds have activated the delta 

electric field contours within a period of 10 minutes before launch. The maximum electric fields 

associated with subject cloud as measured on the ground must not exceed 2 kV/m. The electric field 

meter readings for double layer clouds cannot exceed 500 V/m.

Additional knowledge about cloud electrification accumulated over the years due to research and operational 

experience. During the extensive program-wide reviews of weather support that followed the Challenger 

accident described in section 4.3 below, an improved set of Shuttle LLCC were adopted. These read as follows 

(Heritage, 1988, Table 4-4):

1986 Shuttle Lightning Launch Commit Criteria (LLCC)

Do not launch if vehicle path is:

• Within 5 nm of a cumulonimbus cloud or the edge of associated anvil cloud;

• Within 5 nm of any convective cloud whose top extends to -20C isotherm with virga/precipitation; 

• Through any cloud where precipitation is observed;

• Through dissipating clouds in which the electric field network has detected lightning within 15 

minutes prior to launch;

• Through any cloud if ground level electric field at launch site is greater [in magnitude] than + or -

1000 V/m.

These included three major changes from the 1979 version:

1. The wording was simplified.

2. The surface field mill threshold was made consistent at 1000 V/m.

3. The threshold isotherm for convective cloud tops was changed from -10 oC to -20 oC based on 

research such as that of Cobb (1975).

4.1 Infrastructure

Except as noted below in this section, the weather infrastructure at KSC/CCAFS remained the same as that 

presented in Section 3.1 during the period covered by this chapter.
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Early in the Shuttle program the wind tower network that NASA maintained at KSC and the similar network 

maintained by the Air Force at CCAFS were combined as a single system belonging to the Air Force to reduce 

duplication of effort and cost. The combined network expanded to 29 and later to 47 locations (Billie Boyd, 

45WS, private communication). Although a few sites have been decommissioned, this is essentially the 

configuration of the wind tower network today. Most of these towers are 16.5m (54ft) tall and instrumented for 

wind at two levels, 12 and 54 feet, and for temperature at two levels, 6 and 54 feet. In addition to the 150 

meter tower mentioned above there are three other tall towers, each 62m (204 ft) tall instrumented at 4 levels 

[Eastern Range Handbook, 2007].

The CGLSS system was upgraded during this period. In August 1983, a low-gain system was added to obtain 

more accurate locations near the KSC-ER launch complexes. By February 1984, the system contained two 

low-gain direction-finders (DFs) that were located at the Ti-Co Airport (28.5N 80.8W) and on Merritt Island 

(28.4N 81.3W), and three medium-gain sensors, one co-located with the low-gain sensor on Merritt Island, and 

the other two were at the Orlando and Melbourne Airports (Harms, et al., 2001).

4.2 Organization

On 1 October 1978, the Air Force assumed full operational weather support for launch and ground processing 

operations at KSC and the Eastern Range, whether manned or unmanned. SMG retained responsibility for onorbit and landing operations at all locations including KSC. Following the Challenger accident in 1986, NASA 

funded additional Air Force support for the Shuttle program including a dedicated full-time civilian launch 

weather officer. Although there have been some organizational name changes, the overall structure and content 

of weather support has not changed significantly since then. Support is currently provided by the 45th Weather 

Squadron within the 45th Space Wing at Cape Canaveral Air Force Station. Although the structure and content 

of the support has remained relatively stable, the infrastructure and instrumentation has changed substantially 

and is discussed later in this History.

4.3 Operations

4.3.1 Challenger

On a cold, clear morning in January 1986, the Space Shuttle Challenger and its crew of seven, including 

school teacher Christa McAuliffe, ascended above launch complex 39 at Kennedy Space Center to the cheers 

of spectators on site and around the world, including tens of thousands of school children watching on 

television. About 70 seconds into the flight, after the routine call “go at throttle up” had been issued, the 

vehicle exploded and the crew fell to their deaths in the Atlantic Ocean just a few miles off the Cape Canaveral 

seashore. Extreme cold weather, high wind shear aloft, and defective design of the O-ring seals at the solid 

rocket booster segment joints combined to permit the super-hot booster flame to burn through the booster case 

and into the external tank containing tons of explosive rocket fuel for the Shuttle’s main engines. The defining 

operational incident during the opening years of the Shuttle Program had nothing directly to do with lightning, 

but the destruction of the Challenger and the ensuing investigations (e.g., Rogers, 1986) exposed generic 

weaknesses in weather support procedures and processes. The procedures and processes used to avoid 

lightning hazards were not immune to these weaknesses.

In the early 1980s, weather was the single most frequent cause of Space Shuttle launch scrubs and delays. 

Delays and scrubs were costly both in terms of labor hours and for expendables such as propellants consumed 

during each countdown. In an attempt to reduce these delays and scrubs, NASA had convened a “blue ribbon” 

panel of experts in November of 1985 to assess NASA weather support activities and plans. The panel, 

formally called the Space Shuttle Weather Forecasting Advisory Panel and informally called the Theon Panel 

after its chairman, Dr. John Theon, had circulated preliminary recommendations just prior to the Challenger 

accident. These were reviewed and revised by the panel following Challenger. In October 1986, it published 

its official recommendations (Theon, 1986, 1988). The mission of the Theon Panel and its recommendations 
Page 31 of 234

are important for this History because they address infrastructure, technological, and organizational issues 

directly relevant to the development and application of the LLCC. 

The Theon Panels specific tasks included the following:

• Review current weather observation, analysis, and forecasting facilities, systems, and procedures 

which provide the weather forecasts to Shuttle managers for Shuttle ground processing, launch, and 

landing operations;

• Review future plans for these facilities, systems, and procedures;

• Advise NASA Associate Administrator for Space Flight on current and planned capabilities for 

providing state-of-the-art operational weather forecasts;

• Recommend processes and/technologies to the Associate Administrator to improve weather forecasts 

for the planning and execution of Shuttle operations.

The resulting set of recommendations (as cited in National Research Council, 1988, Appendix C, pp59-63.) 

was extensive:

• Establish a Weather Support Office at top level of Shuttle operations to plan, organize, focus and 

direct weather support activities. The Office Chief should be a senior atmospheric scientist or senior 

technical manager with strong operations background;

 Establish a small, highly qualified, well-trained, and dedicated team of forecasters who 

provide weather support for operations. Forecasters should be integral part of Shuttle team and 

remain for extended periods (5-10 years). Ensure their continuity and their devotion to the 

task;

 Establish a Technique Transition Unit at each operational site. Purpose: Ensure forecasters 

have latest research results and tools; are trained to use tools effectively; and act as an 

interface between the R&D community and the forecast team;

• Quantify weather hazards;

• Re-examine models used for wind-loading calculations in view of the upcoming installation of the 

new KSC wind profiler and its ability to detect the rapid wind profile changes which undoubtedly 

occur under many weather situations;

 Establish an external Shuttle Weather Advisory Panel of experts;

 Integrate applications into MIDDS weather display systems at JSC, CCAFS, EAFB, and 

VAFB;

• NEXRAD (Doppler weather radar): Integrate into MIDDS and develop Cape-specific applications;

 Improve the Mesonet weather tower network;

 Develop Thermal Protection System (tile) rain erosion measurement and aircraft 

instrumentation;

• Review/develop local short/long-term mesoscale forecast models and Shuttle specific applications;

 Maintain KSC artificial intelligence study at a modest research level.

Because of the cost involved in implementing many of these recommendations, the NASA Administrator 

forwarded the report of the Theon Panel to the National Research Council to request a “second opinion”.

While the NRC was considering whether to review the Theon report, NASA and the Department of Defense 

suffered another major accident, the loss of AC 67 described in the next section below. As a result, the NRC 

agreed to review the Theon report but in the context of the whole American space program rather than just that 

of the Shuttle program. The NRC reinforced and expanded upon the recommendations of the Theon Panel and 

many of them were adopted as described in Chapter 5, section 5.0.2 below.

4.3.2 Atlas Centaur 67 (AC 67)

Late in the afternoon of 26 March 1987, while the NRC was still considering whether to review the Theon 

Report as requested by NASA, an Atlas-Centaur designated AC 67 lifted off into a dark, precipitating 
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stratiform overcast from launch complex 36B at Cape Canaveral Air Force Station. The payload was a Fleet 

SatCom satellite for the US Navy. NASA was responsible for managing the launch. Just under 50 seconds 

later a cloud to ground lightning strike was photographed at the pad and two seconds after that the vehicle 

began to break up. Destruction of AC 67 was completed by the Range Safety Officer. The NRC responded to 

NASA by agreeing to review the Theon Panel report, but in the broader context of the whole American Space 

Program rather than just the Shuttle Program. A discussion of panels convened, recommendations and actions 

pursued as a result of AC 67 is presented in detail in Chapter 5.

The LLCC used for AC 67 were very similar to the post-Apollo XII rules described in Section 3.0 and read as 

follows (Heritage, 1988, p. 4-9, Table 4-5)

Atlas/Centaur 67 Lightning Launch Commit Criteria (1987)

Flight path of the vehicle should not be:

A. Through a thunderstorm/cumulonimbus cloud.

B. Within 5 miles of thunderstorm/cumulonimbus cloud or 3 miles of associated anvil top.

C. Through cold front/squall line associated clouds with tops 10,000 ft or higher.

D. Through middle-level cloud layers, 6,000 ft or greater in depth, when the freezing level is in the 

clouds.

E. Through cumulus clouds with the freezing level in the clouds.

4.4 Research

4.4.1 KSC Rocket Triggered Lightning Program (RTLP)

This program was organized and operated by the KSC Engineering Directorate (DE) rather than by 

the KSC Weather Office. The NASA/DE RTLP lead engineer was William Jafferis, who was 

extremely enthusiastic about the project. Mr. Jafferis was convinced, even before the AC 67 disaster 

in 1987 (see above and Section 5.0), that not enough was known about lightning in general and 

triggered lightning in particular to safely conduct space launches in the Cape Canaveral area.

Throughout its nine-year history (1983 through 1991) he managed and directed the program with 

funding from the Shuttle Program at KSC, supplemented by private sources such as the Electric 

Power Research Institute, Florida Power and Light, and others. By its conclusion, he had built KSC 

into the world's leading center for rocket-triggering research. Three LAP members (Krider, Willett, 

and Rust) participated in the RTLP at various times during its life. In addition to numerous scientific 

papers and technical reports, an article about the program was published in the New York Times in the 

aftermath of the AC 67 accident (Wilford, 1987).

Summertime rocket-triggering experiments by the RTLP were begun in 1983 south of Melbourne, FL 

(Richmond, 1984). They were moved some 50 km north in 1984 to a site just east of the Vertical Assembly 

Building (VAB) at the NASA Kennedy Space Center (KSC). In 1985 triggering operations were moved again, 

about 15 km further north to the west bank of the Mosquito Lagoon, where they continued through 1991. The 

Mosquito Lagoon facility eventually comprised two instrumented triggering locations (the original "land pad," 

and a newer "water pad," described below), two control and instrumentation trailers (one a discarded 

Chesapeake & Ohio railroad caboose), a "headquarters" building dubbed the Atmospheric Sciences Field 

Laboratory (ASFL), and an un-energized, 448 m long, electric-power distribution line running approximately 

between the land pad and the ASFL. Diesel generators were provided for operations during storms, when 

commercial power in the area was unreliable. A tethered balloon (aerostat) was even operated during 1989 and 

1990 to support instruments aloft and to trigger lightning from an elevated and ground-isolated platform. In 

August of 1991, however, an accident with injury involving the unintended launch of a 2.75" Folding-Fin 

Aircraft Rocket by French investigators brought the program to an end [Mishap Investigation Team Report, 
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1991]. Earlier that same season, the aerostat had blown away and been lost at sea, which did not help the 

program's standing with KSC management.

Thereafter, triggering activities by some of the participants and funding sources moved to Camp Blanding in 

Starke, FL, under the management of the University of Florida, where they continue and flourish to this day.

Unfortunately, this move, coupled with the loss of Shuttle Program funding, eliminated any motivation to 

address the operational needs of the space program. The research at Camp Blanding became even more 

focused on the concerns of the electric power industry (although this focus has broadened recently because of 

significant long-term funding from the National Science Foundation).

Fundamentally, the demise of the KSC RTLP resulted from the contemporary reorganization of weather 

infrastructure throughout NASA that had been recommended by the Theon and NRC panels. The new NASA 

Weather Support Office (see Section 5.2.0) led by Jack Ernst at NASA Headquarters and its counterpart at 

KSC (see Section 5.2.2) led by Jan Zysko, assumed control of the Shuttle weather-related "research" funding 

to ensure that it was directed towards narrowly defined, operational needs. In February, 1989, Jim Nicholson 

(NASA/KSC/PT, the conduit for this funding) conducted a blue-ribbon panel review of the RTLP to get 

recommendations on how it could be restructured to support Shuttle operations more directly. This panel 

consisted of the following experts on lightning and atmospheric electricity: E. Philip Krider (University of 

Arizona, Chair), Jean-Louis Boulay (ONERA, France), Charles B. Moore (NMIMT), Richard E. Orville (State 

University of New York at Albany), Martin A. Uman (University of Florida, Gainesville), and John C. Willett 

(AFGL). Its report [Review of and Recommendations for the Rocket Triggered Lightning Program (RTLP) at 

the NASA Kennedy Space Center, revised August 1, 1989] identified several experimental efforts that would 

be of great value to the operational community and that could be carried out by the RTLP. It also 

recommended some changes in the organization of the RTLP, its funding, and the objectives to achieve these 

ends. Unfortunately, the recommended changes never came to pass, and this more or less guaranteed the 

termination of the RTLP when the above-mentioned accidents occurred.

French technicians from the Centre Etudes Nucleaires de Grenoble (CENG), who described the campaigns in a 

series of technical reports (e.g., Eybert-Berard et al., 1986; Barret, 1986; Eybert-Berard et al., 1988, 1989; 

Barret et al., 1990; Barret et al., 1991), provided some of the infrastructure, although KSC also developed its 

own operational capability. Two different triggering platforms were used at the Mosquito-Lagoon site. A "land 

pad" was constructed near the shore of the lagoon in 1985 to facilitate engineering tests on isolated conducting 

bodies and other hardware, and its configuration is quite complicated (see Leteinturier et al., 1990). A simpler 

"water pad" was constructed about 30 m offshore in 1987 to enable more precise electromagnetic 

measurements (Leteinturier et al., 1991).

The triggering techniques used in the RTLP have been described in detail by Laroche et al. (1985, 1989a, and 

1991). Two basic rocket-and-wire methods were used at KSC; in both, a spool of fine Kevlar (TM)-wrapped 

copper wire was raised by a meter-long, plastic-bodied, black-power-fueled rocket. (This approach of raising 

the spool was pioneered at the RTLP in 1983. Previously a spool of cotton-wrapped steel wire had been 

mounted on the ground, and the rocket lifted only the free end of the wire.) The rockets could reach altitudes 

of about one kilometer in a several seconds. The "classical" technique (sometimes called LRSG) involved 

unspooling a continuous, grounded wire as the rocket ascended. This method has the advantage of allowing a 

direct measurement of the lightning current at the base of the wire (lightning channel). The "altitude" 

technique (LRSA -- also pioneered at KSC in 1987) is similar, except that the rocket unspools a few hundred 

meters of non-conducting line before the conducting (un-grounded) wire was paid out. Altitude triggering was 

developed to simulate better how lightning strikes airborne vehicles and to study the leaders that develop early 

in the discharge between the lower end of the triggering wire and ground. A later innovation in the altitude 

technique was the addition of a short length of grounded wire below the non-conducting segment (LRSAG), to 

facilitate studying the ground-striking process and allow direct measurement of currents in this "lightning rod."

The key scientific results from these experiments are given in Section 5.4.3.
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4.4.2 Research on Lightning Strikes to Aircraft

More or less contemporaneously with the KSC Rocket-Triggered Lightning Program, several experimental 

studies were performed on the physics and phenomenology of lightning strikes to aircraft, and these have been 

reviewed by Uman and Rakov (2003), which is the basis for most of the following material. We will return to 

this subject in more detail in the separate Rationale document because of the fact that most lightning strikes to 

airborne vehicles are triggered by the vehicle itself after it flies into a high electric field.

Our understanding of the initiation and characteristics of lightning strikes to aircraft is derived primarily from 

airborne studies involving four instrumented aircraft, an F-100F, an F-106B, a CV-580, and a C-160. The F100F project, termed Rough Rider, could have been described in Chapter 2, but it is covered here to keep it 

together with the other three. Rough Rider was operated by Don Fitzgerald of the Air Force Geophysics 

Laboratory in collaboration with the FAA between 1964 and 1966 and is described by Fitzgerald (1967) and 

by Petterson and Wood (1968). The F-100F, a single-engine jet fighter, penetrated thunderstorms to measure 

turbulence and to obtain photographic, shock wave, and electric current records of lightning. Data were 

recorded for 49 lightning discharges on rather primitive instrumentation by today’s standards.

The NASA F-106B, a delta wing, single-engine jet fighter, was operated by the NASA Langley Research 

Center. It flew about 1500 thunderstorm traversals at altitudes ranging from 5000 to 40,000 feet (1.5–12 km) 

and was struck by lightning 714 times between 1980 and 1986 (Pitts et al., 1988). Statistics were compiled for 

aircraft surface electric and magnetic field derivatives and for lightning currents and current derivatives 

flowing through the aircraft. Detailed information on the instrumentation and data obtained can be found in 

numerous publications listed by Uman and Rakov (2003).

The USAF/FAA CV-580, a twin-engine turboprop transport aircraft, was instrumented as described by Rustan 

(1986) and others and was flown in 1984 and 1985. Numerous sensors measured the time derivative of the 

surface electric-field intensity, the rate-of-change of the surface current density, the "slow" electric-field 

change (with a lower-frequency response of 1 Hz), and the current injected into the tail and wingtips. In 

addition, five electric field mills were mounted at various locations on the fuselage. The latter instrumentation 

yielded some of the first, reasonably credible measurements of the ambient fields and aircraft charge 

immediately prior to lightning strikes (Bailey and Anderson, 1987; Anderson and Bailey, 1987).

The C-160 research aircraft that was operated by ONERA in the Transall field programs in France during 1984 

and 1988 was a twin-engine aircraft similar to the CV-580 but somewhat larger. For the 1988 study the C-160 

was instrumented specifically for investigation of the initial processes of lightning attachment, with a network 

of five electric field mills, numerous capacitive antennas and current shunts, and a high-speed video system

(Lalande et al., 1999, and others). The field-mill system was again used to determine the ambient field and 

charge on the aircraft just prior to lightning strikes.

The key results from these experimental programs are the following:

1. About 90% of lightning strikes to flying aircraft, and by inference to spacecraft in the troposphere, are 

triggered by the aircraft (Lalande and Bondiou-Clergerie, 1997).

2. The maximum current derivatives (dI/dt) measured on aircraft can be as large as those in lightning 

return strokes at the ground (see Section 5.4.3), although the peak currents are not as large and the rise 

times of the fast-rising portions are shorter (Pitts et al., 1987).

3. Current pulses that have large dI/dt values and high repetition rates occur, primarily during the early 

stages of lightning attachment. This observation has led to addition of a so-called "multiple burst" 

waveform to the aircraft test standards (e.g., Plumer, 1992).
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Chapter 5 The Aftermath of Atlas Centaur 67 (1987 – 1999)

5.0 The AC 67 Investigations

The AC 67accident closely followed the Challenger accident, thus it generated national attention. The result 

was a series of investigations by NASA; the Air Force; the Navy; the National Research Council; the media; 

standing conferences including AIAA, AMS, AGU, and AF/NASA; Congress (including formal House 

Hearings); and three Flight Rules workshops with JSC, MSFC, KSC, AF, and consultants participating.

Following are dates when Reviews were directed and either held or published:

Oct 86 NASA Theon Panel publishes report pre-AC 67 (See section 4.3)

27 Mar 87 Admiral Truly, Hq NASA/M, Office of Space Flight, directs formation of AC 67 accident 

board chaired by Jon Busse, Goddard Space Flight Center MD (GSFC)

11 May 87 Hq Air Force directs AF Space Division to form Lightning Review Committee to investigate 

AC 67 incident – results in the “Heritage Committee” report on 31 August 1988

9 June 87 NASA/Busse Preliminary Report

15 July 87 NASA/Busse Final Report

4 August 87 Congressional Hearings Chaired by Representative Bill Nelson

5 August 88 National Research Council publishes Meteorological Support for Space Operations--Review 

and Recommendations – the result of the NRC’s review of the Theon Panel report cited 

above.

31 August 88 Air Force Lightning Review Committee, chaired by Hugh Heritage, publishes final report: 

Launch Vehicle Lightning/Atmospheric Electrical Constraints Post AC 67 Incident

Each of the three expert panels formed to determine the cause(s) of the accident and to recommend ways to 

prevent such events from happening in the future is described separately below. In addition to these panels of 

technical experts, there was a Congressional investigation and hearings before Congressional Subcommittees. 

One of these is also described in detail below.

5.0.1 Busse Panel

NASA Headquarters appointed the Atlas/Centaur-67/FLTSATCOM F-6 Investigation Board chaired by Jon R. 

Busse. This Board in turn invited a Sub-Panel of experts on lightning and electromagnetic pulse to investigate 

the weather and the probable causes of the AC 67 incident and to make recommendations. The members of 

this Sub-Panel are presented in Table 5.0.1-1.

The Sub-Panel published their results in a NASA Report (Christian et al., 1987). The same authors also 

published a peer reviewed article in the Journal of Geophysical Research (Christian et al., 1989).

The Final Report of the Atlas/Centaur-67/FLTSATCOM F-6 Investigation Board (hereafter termed the Busse 

Report) was approved on May 11, 1987, and was officially dated July 15, 1987. The basic conclusion of the 

Busse Report was that the breakup of the Atlas/Centaur-67 vehicle was caused by large dynamic loads during 

flight as a result of an excessive angle of attack. This in turn was caused by an unplanned, hard-over booster 

engine gimbal command being issued by the Centaur Digital Computer Unit (DCU).

The most credible mechanism for causing the booster engine hard-over command was the DCU reacting to an 

external electrical transient. All other mechanisms are improbable. The electrical transient was caused by a 

triggered lightning strike on the vehicle. The strike occurred on the vehicle nose fairing and coupled into the 

ground bus network through multiple paths, including the wiring from the booster external equipment pod and 

the nose fairing accelerometer wiring. These transients entered the DCU and caused the alteration of a single 

word in the DCU memory associated with the computation of the Atlas engine yaw commands.
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Panel Member Name and Title Panel Member Affiliation

Bruce D. Fisher

Chairperson

Research Engineer, NASA Langley Research Center

Keith E. Crouch

Vice President

Lightning Technologies, Inc.

Dr. Vladislav Mazur

Research Physicist

NOAA National Severe Storms Laboratory

Dr. Lothar H. Ruhnke

Head, Atmospheric Physics Branch

Naval Research Laboratory

Dr. Hugh J. Christian, Jr.

Research Scientist

NASA Marshall Space Flight Center

Dr. Rodney A. Perala

Vice President

Electro Magnetic Applications, Inc.

Table 5.0.1-1 Members of the expert Sub-Panel of the Busse Panel

In the opinion of the Board, the most probable cause of the mission failure was launching the AC 67 vehicle 

into atmospheric conditions conducive to triggered lightning and in violation of the established criteria used to 

avoid potential electrical hazards.

Chapter II of the Busse Report contains a number of Determinations, Findings, Observations, and 

Recommendations, among which are:

Determination: The vehicle was launched into adverse weather conditions of rain, clouds, and intense 

electric fields. The conditions existing at launch time were in violation of the criterion stating that the 

flight path of the vehicle should not be through middle-level cloud layers 6,000 feet or greater in 

depth, when the freezing level is in the clouds. (p. II-1)

Finding: Before the AC 67 launch, there were a significant number of indications that generally the 

weather was unfavorable and that specifically there was a lightning hazard. Yet the real import of 

these indications escaped the launch management team because of imprecise communications, lack of 

awareness, or both.

Recommendation: It should be emphasized to all management personnel, whether directly or 

indirectly involved in the launch decision process, that they have a responsibility to exercise 

awareness,

judgment, and leadership. Management must be constantly alert to variations to planned launch 

activities. They must provide a questioning and challenging attitude towards the validity of inputs 

being made. (p. II-2);

Finding: The electric field mill data just prior to launch indicated the potential for lightning near the 

AC 67 pad. While the field mill data is not a part of the stated potential electrical hazards criteria, 

weather personnel were aware of the field mill data and the possible hazard to launch.

Recommendation: An electric field mill criterion should be established for Expendable Launch 

Vehicles (ELVs) to formally establish electric field strength measurements as an element of 

determining lightning potential.

Recommendation: The electric field mill system should be transitioned to operational status. (p. II-3)
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and

Finding: The weather criteria currently used for ELVs by NASA will not avoid all situations for 

known risks of lightning strikes.

Recommendation: The (weather) criteria should be revised to take into consideration the additional 

knowledge and measurement techniques of lightning phenomena that have been developed since the 

present ELV criteria were established in 1970. The Shuttle and ELV weather criteria should converge 

where practical. (p. II-3).

Appendix H of the Busse report (Volume II, Book 3) should be noted. It includes a detailed analysis of 

measurements that were obtained during the AC 67 incident (pp. H-3 to H-137), an analysis of the weather and 

applicable LLCC at the time of the incident (H-137 to H-139), an evaluation of the lightning detection systems 

that were operating at the time of the incident (H-141 to H-143), an analysis of the susceptibility of the AC 67 

vehicle to lightning, and several recommendations for hardening the vehicle against lightning disturbances.

Attachment H-1 to Appendix H describes the electric field mills that were operating at the KSC-ESMC at the 

time of AC 67 incident and the use of network of such sensors to detect and locate electrified clouds and 

lightning. It also reviews and compares four other lightning detection systems that covered the launch area at 

the time of the incident (see pp H-181 to H-234).

Attachment H-2 to Appendix H contains a description of the electric field mill calibration procedures that were 

used at the ESMC and the stability of those sensors over time (pp. H-243 to H-254), a model of the physics of 

triggering lightning in an electrified environment, including the effects of the vehicle geometry and its exhaust 

plume (pp. H-257 to H-279), and a comparison of electric fields measured on the ground with those measured 

aloft (H-280 to H-296). Attachment H-2 also contains a report of a lightning discharge that was observed 

during the launch of A/C-38 (H-297 to H-310).

5.0.2 The National Academy of Sciences

The National Academy of Sciences (NAS) appointed a “Panel on Meteorological Support for Space 

Operations” that was chaired by Dr. Charles L. Hosler of the Pennsylvania State University. The other 

members of the NAS Panel were:

Gregory S. Forbes, Pennsylvania State University

Joseph B. Klemp, National Center for Atmospheric Research

E. Philip Krider, University of Arizona

John A. McGinley, National Oceanic and Atmospheric Administration

Peter S. Ray, Florida State University

Leonard W. Snellman, University of Utah

The panel was assisted by John D. Perry and Fred D. White of the NAS staff. The Hosler panel had a number 

of meetings with people and organizations that were involved in space operations, and in 1988 it published a 

Report (National Research Council, 1988, hereafter NRC) that highlighted the importance of weather in space 

operations and made five specific recommendations to improve weather support at the KSC-ER. These were:

1. Quantify more rigorously the relationships between the magnitudes of weather variables and the 

hazards they pose to space vehicles. Flight rules and launch commit criteria should be based on these 

relationships. (NRC, p3.)

2. New and improved instrumentation must be used to detect weather conditions and phenomena that are 

hazardous to space operations. (NRC, p4.)
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3. A number of emerging techniques for weather analysis and forecasting and decision making must be 

actively pursued. (NRC, p5.)

4. Give clear and unambiguous authority to the Weather Support Office and give it sufficient budgetary

authority to ensure an integrated and coordinated meteorological support program for all phases of 

manned and unmanned spaceflight. (NRC, p6.)

5. An Applied Research and Forecasting Facility (ARFF) should be established at Kennedy Space Center 

to promote the development and application of new measurement technology and new weather 

analysis and forecasting techniques to improve weather support for space operations, to provide 

forecaster education and training, to coordinate field programs involving the meteorological 

community and to conduct an active visiting scientist program. (ibid).

Many of these recommendations were at least partially implemented or completely implemented in modified 

form. The Lightning LCC have been substantially improved based on two field programs, ABFM I (section 

5.4.1 below) and ABFM II (section 6.4 below) consistent with recommendation 1. The improvements in 

lightning instrumentation described in section 5.1 follow from recommendation 2. The creation of the Applied 

Meteorology Unit (see section 5.2.3) implemented recommendation 5 for the purpose of achieving 

recommendation 3. Recommendation 4 was at least partially implemented by providing Weather Support 

Office with sufficient funding and authority to operate the AMU and conduct detailed annual reviews of 

weather support to the Space Shuttle program.

5.0.3 Aerospace Corporation-Heritage

The Air Force Systems Command, Space Division, asked the Aerospace Corporation to study the weather 

conditions surrounding the AC 67 incident and the existing launch vehicle weather constraints and to provide 

recommendations for improvement. To satisfy this request, the Aerospace Corporation appointed a ‘Lightning 

Review Committee’ (LRC) that had 5 members from the Aerospace Corporation and 6 outside experts with 

expertise in lightning and atmospheric electricity. All members are listed in Table 5.0.3-1 taken from the 

Heritage Report (Heritage, 1988), page xvi.

This group operated as both a Team and a Committee. It held numerous meetings and discussions, and each 

member was asked to contribute to the Team in his own expert area. As a convened body, the group was 

required to consider, act, report, and recommend, and thereby was a Committee. Each committee member, 

including the chairman, had one equally weighted vote. Meetings were conducted with a provision for open, 

informal discussion of issues so that all committee members wishing to express their views could be heard.

The LRC was provided adequate time for discussion so that ‘unanimous approval’ of issues could be 

optimized. On occasions when this approach was not successful, a member vote was taken, and a simple 

majority was required to approve or reject an issue. The majority contained participating members from two 

subsets, the subsets being: (1) Aerospace employees and (2) outside consultants. Members with strong 

minority views were encouraged to submit perspective views, and they were allotted an Appendix of the LRC 

Report to express them. All items distributed for review by the LRC, other than during meetings, were given a 

one week suspense date. The member receipt of the review material, without subsequent response, was 

considered for voting purposes to be a vote in favor.

Name Company Title

Bruce Edgar Aerospace Corporation Scientist, Space Test Program

Hugh Heritage Aerospace Corporation Chairman -Lightning Review Team, Manager –

Electrical Systems, Space Launch Operations

Robert H. Holzworth II University of Washington Professor of Geophysics, Adjunct Professor of 

Physics

William Jafferis NASA/KSC Advanced Projects
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Name Company Title

Harry Koons Aerospace Corporation Senior Scientist, Space Plasma Physics

E. Philip Krider University of Arizona Professor and Director -Institute of Atmospheric 

Physics

Glenn Light Aerospace Corporation Project Engineer -Space Surveillance and 

Tracking Systems

Joseph E. Nanevicz SRI International Deputy Director -Electromagnetic Sciences 

Laboratory

W. David Rust NOAA National Severe Storm Laboratory

Martin A. Uman University of Florida Professor of Electrical Engineering

Richard Walterscheid Aerospace Corporation Research Scientist, Atmospheric Dynamics

Harry Wilson Aerospace Corporation

Table 5.0.3-1 Lightning Review Committee

The LRC published its Report as Aerospace Report No. TOR-0088(3441-45)-2 and it is dated 31 August 1988.

It contains an Executive Summary, 11 Chapters and an Appendix. The Chapter titles are:

Chapter 1. CLOUD ELECTRIFICATION

Chapter 2. NATURAL AND TRIGGERED LIGHTNING

Chapter 3. LAUNCH VEHICLE ELECTRIFICATION -SELF INDUCED, CLOUD INDUCED

Chapter 4. RELEVANT LAUNCH RULES

Chapter 5. RELEVANT INSTRUMENTATION

Chapter 6. INSTRUMENT RECOMMENDATIONS

Chapter 7. RECOMMENDED LAUNCH CONSTRAINTS AND RATIONALE

Chapter 8. TRAINING AND EDUCATION

Chapter 9. RECOMMENDED RESEARCH

Chapter 10. SUMMARY AND CONCLUSIONS

Chapter 11. GLOSSARY, TERMS, AND DEFINITIONS

The primary protection method adopted by the LRC was to hold (delay) the launch under any of the following 

four conditions from paragraph 7.2 of the Report:

a. When natural lightning has recently occurred in the vicinity of the launch complex or along the 

planned flight path (see Constraint I in paragraph 7.2).

b. When meteorological measurements indicate that electric fields may be present with sufficient 

intensity to cause the vehicle to trigger lightning (Constraint II). This heading comprises seven cloudbased rules similar to those in the current LLCC, plus exceptions to several of those rules based on 

electric-field measurements aloft along the flight path.

c. When atmospheric electrical measurements at the ground indicate that electric fields may have 

sufficient intensity to cause the vehicle to trigger lightning (Constraint III).

d. When atmospheric conditions are such that the launch vehicle interacting with cloud particles, 

precipitation, or electric fields might charge and produce electrostatic discharges capable of affecting 

vehicle subsystems (Constraint IV).

The specific launch constraints recommended by the LRC, assuming that the primary hazards are vehicletriggered lightning, natural lightning, and triboelectrification (due to interactions of the vehicle with its 

environment during the ascent phase of the mission) are described in Chapter 7 of Heritage (1988) and are 

presented in our Appendix I, section A1.8, but not reproduced here because of their length.
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The LRC concluded that ‘The primary atmospheric electrical hazard to launches is vehicle triggered lightning; 

that is, lightning initiated by the launch vehicle itself in situations where natural lightning otherwise would not 

occur. Launch vehicles, by virtue of their enhancement (concentration) of the ambient electric field, can 

initiate lightning in electric fields that are tens to hundreds of times smaller than what would be required to 

initiate natural lightning. Electric fields at the ground greater than about 1 kV/m, and all fields aloft greater 

than about 5 kV/m (or even lower at high altitudes), indicate that there is a potential for vehicle-triggered 

discharges. Fields of this level and higher can be generated by common thunderstorms and also by nonthunderstorm clouds, such as nimbostratus, cirrus anvils, other types of layer clouds, and cumulus clouds in 

various stages of development. In fact, the triggered strikes to both Apollo 12 and Atlas/Centaur-67 occurred 

in stratus clouds associated with fronts. Additional hazards to the launch vehicles include direct strikes from 

natural lightning and the effects of vehicle electrification.’ (p. 10-1)

5.0.4 The Subcommittee on Space Science and Applications Hearing

This section consists of notes paraphrasing key portions of the transcript of the hearing before the House 

Subcommittee (Committee on Science, Space and Technology, 1987). Unless the text is in quotation marks 

and explicitly designated as a direct quotation, it is not a verbatim reproduction of what was said. The 

proceedings are summarized in great detail because they provide significant insight into the mindsets of those 

responsible for assessing the weather and those responsible for assessing the weather’s potential impact on the 

mission’s safety and success. The authors of this History have added notes and comments throughout the 

section to emphasize or expand on key issues. In many cases, the initials of the specific author of the note or 

comment are provided.

Although the payload was owned by the U.S. Navy, the Department of Defense had contracted with NASA to 

provide the launch services and with the Air Force provided the operational weather support. As a result, much 

of the heat from the Congressional inquiry fell on NASA and the Air Force. In the transcript below the 

Congressmen are identified by their party affiliation and state in parentheses following their names. Key 

witnesses whose identity may not be stated explicitly in the proceedings below include the following:

• Jon R. Busse – Chairman of the NASA panel that investigated AC 67

• Brig. Gen. George E. Chapman – Commander of Air Weather Service

• Maj. Gen. Donald L. Cromer – Vice Commander of Air Force Space Division

• Lt. Gen. Forrest McCartney – NASA KSC Center Director

• George A. Rodney – NASA Associate Administrator for Safety, Reliability, Maintainability and 

Quality Assurance

• Adm. Richard Truly – NASA Administrator

• Lt. Col. John Warburton – Commander of the 45th Weather Squadron during the AC 67 launch

• James Womak – NASA/KSC Acting Director, ELV operations

Following many of the paraphrases below, the page number where the testimony may be found in Committee 

on Science, Space and Technology (1987) is noted in parentheses.

Mr. Nelson (D FL), Opening Remarks: Purpose of Hearings--Learn what happened to cause accident and how 

to prevent future accidents. ‘NASA management seemed to be improving after Challenger, was it real and 

lasting, or was NASA slipping’?

Mr. Walker (R PA), Opening Remarks: Purposely keep man in loop because the best general purpose 

computer ever devised rested between the ears of every human being. Every member of launch team has a 

responsibility to stand up and say this doesn’t make sense, aren’t we doing something dumb here? Thus want 

everyone to be open and honest. Over 2000 launches occurred from CCAFS last 30+ years with virtually no 

mission failures due to weather.
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Mr. Busse was the first witness and began by summarizing his written statement including the conclusions and

recommendations from his investigation. (See previous section, NASA Busse Report, for details.)

Chairman Nelson asked Busse if his panel determined why NASA and ELV criteria for electrical hazards were 

different. Busse replied the Shuttle criteria were revised (for Shuttle) in late 1970s but ELVs did not feel 

revisions were necessary but there was nothing in writing.

Chairman Nelson asked Busse if field mills were used during countdown. Busse replied yes, there’s evidence 

in transcripts of Cape Weather discussing field mill readings with launch managers during countdown. Data is 

available in two forms: continuous readings on strip charts for selected mills; and also on a contour display 

which takes data from all operational mills and generates contours of constant electric field intensity. Busse 

added that only 21 of the 34 field mills were operating during countdown. (p 18)

Chairman Nelson questioned the rationale for the 1000 V/m criterion. Bruce Fisher (NASA Langley engineer 

involved in F106 research programs) replied it was based on the accumulated research in the scientific 

literature from balloon borne experiments with field mills, airborne field mill research, and especially the 

experiments done at KSC’s rocket triggered lightning site. A more detailed written explanation was later 

provided by Dr. Hugh Christian of NASA/MSFC and Mr. Dwight Surter of NASA/JSC: Cape foliage goes 

into Corona at about 3-5000V/m and creates screening layers between the surface and the charged clouds 

above. Rocket triggered lightning experiments suggest lightning can be triggered when fields reach 3000 V/m. 

1000 V/m was chosen as the constraint threshold to provide an added level of safety from 3000 V/m and 

because it’s below the value at which the Cape foliage begins to go into corona and produce space charge and 

screening layers. (p 21)

(Note: The LAP is currently preparing a companion document to this History explaining the scientific, 

technical and operational rationale behind the current LLCC. The Rationale document is being prepared as 

part of the same project as this History. The Rationale will contain additional detail and explanation based on 

latest research findings and theory. )

Chairman Nelson then asked, ‘since 3000 V/m is necessary to trigger lightning, how much greater is the risk of

triggered lightning if the fields were reading 6000-8000 V/m as they were prior to AC 67 launch’? No panel 

members could answer. (p 23)

Chairman Nelson asked if you looked outside that day at time of launch, what kind of weather would you have 

seen? Busse and Lt Col Kim (USAF, Weather commander at Egland AFB, representing AWS) replied it was 

raining with cloud bases at 4500 Broken and 8000 feet (1.4 and 2.4 km) Overcast. There was thunder from 

thunderstorms which had been moving east all day from the Florida West Coast to the Florida East Coast. 

(ibid)

Chairman Nelson questioned why there was no aircraft used. Busse replied an F-16 aircraft was supposed to 

come from McDill AFB in Tampa but the weather was so poor in Tampa the aircraft could not take off. Mr 

Bauman added no aircraft were available from Patrick AFB so they decided to just rely on Pilot Reports. (pp 

23-24)

When discussing the 6000 foot cloud thickness LCC, Congressman Walker concluded there was great 

uncertainty in the triggered lightning LCC and that much may have been learned since the AC 67 LLCC were 

written in 1970. Bruce Fisher agreed.

(Note: The brief dialogue was a good justification for the formation and continuing contributions of the 

Lightning Advisory Panel!) (p 25. See also discussion on p 28 for additional justification for a standing 

Lightning Advisory Panel)
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Rep. Skaggs, member of Chairman Nelson’s Science, Space and Technology Committee, was concerned that 

the analyses and discussions seemed to be compartmentalized around specific LCC. He asked whether 

someone was tasked to look at the data and situation more holistically. He did not receive an answer to his 

question and this concern was expressed in other ways throughout the Hearings.

(Note: Today’s LLCC address his concern, at least partially, in the Common Sense Rule, and the launch day 

LWT processes require the presence of a Senior Weather Officer, preferably the weather unit’s Commander or 

Director of Operations). (pp 26-27)

Throughout the Hearings the subject repeatedly arose of what the LWO (Launch Weather Officer) intended 

when he said ‘weather is GO for launch’ vs. what the Launch Director and his team thought the LWO 

intended. The LWT (Launch Weather Team) intended ‘GO’ to mean the LWT believed all the weather LCC 

had been met, but the LWT also believed the final determination whether the LCC were met was the Launch 

Director’s (LD) responsibility based on the briefings and data provided him by the LWO and his LWT. 

However, the LD believed the LWT meant GO with no caveats for reviewing the data further beyond the 

questioning of the LWO by the LD during their discussions and weather briefs over the net.

Mr. Womack: ‘When we got the GO for launch, I assumed that was a GO for criteria and we met the criteria, 

period --in retrospect I should have questioned them more closely on the criteria that day’. (pp 29-31,37, 38, 

52, 53)

When Rep Buechner asked Mr. Bauman, who’d been the Launch Director for 30 Delta launches, whether he’d 

have launched that day, he relied ‘probably Yes’ because ‘weather had always been accurate before.’ (p33)

Cost of AC 67 vehicle and payload ~ $163M (in 1987 $). (p 35)

Mr. Busse: Burden of proof ought to be on proving the weather is good enough rather than on proving the 

weather is bad.

(Note: This concept of operations is documented in today’s LCC, and has been the case since the major 1988 

LLCC revisions, which require the LWT to be ‘clearly convinced LLCC have not been violated’ i.e. are 

Green.’

Mr. Busse: Field mills are not a cure all for understanding all weather problems or conditions that might exist 

with respect to lightning. (p 37)

Mr. Womack: Decision to launch A/C vehicle required concurrence of three officials: Launch Vehicle 

Manager, Mission (payload) Manager, and Launch Director, in addition to Range who evaluate readiness of 

Weather, Range Safety, Pad Safety, and Vehicle Tracking. (pp 43-44)

LtC. Warburton: ‘We believed the constraints were met, and we recommended the launch proceed based on 

the weather.’(p 48)

LtC. Warburton: It was an overrunning or frontal type of day vs. a summer thunderstorm type of day. (p 49)

Mr. Walker: Someone who was there described the rain coming down was like a monsoon rain--it was difficult 

to drive cars near launch site or on the Cape. (p 53)

Rep. Walker to Launch Director Womack: Were you aware of the field mill readings.?
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Mr. Womack: We discussed field mills in general, the fact they were being monitored, but I received no 

numerical numbers. (p 56)

Rep. Packard to Warburton: Is there a margin of safety in weather criteria?

LtC. Warburton: I don’t believe there’s much margin.

Rep. Packard: Should there be?

LtC. Warburton: Depends on risk or necessity of launch. Some launches must occur. Some launches don’t 

need to occur, and there may even need to be different launch constraint for those. (ibid)

Mr. Womack: General McCartney had advised us that we did not have to launch that day, so be very aware. (p

59)

LtC. Warburton: During one of the 51L [Shuttle Challenger. Ed.] attempts the weather team thought we’d met 

constraints; John Young [An astronaut. Ed.] in airplane thought we’d met constraints; but the Launch Director 

(Bob Sieck) called the situation too marginal and believed we should scrub. We’ve had that type of experience 

in the past. (ibid)

Chairman Nelson: A/C decision seems to have been made in midst of poor communications and blurred lines 

of responsibility--frustrating that Atlas launch team was not well coordinated after all the years of enormous 

and successful experience. Seems the forecasters should have been aware of their role in the launch decision.

The Launch Director should have been more critical of the GO recommendation from the forecasters, and 

especially as was testified here today, that there was no pressure, no urgent need to launch on that particular 

day. So it seems from what we’ve heard so far the launch decision process was flawed with perhaps some of 

the same communications mistakes that were uncovered by the Rogers Commission [The Commission that 

investigated the Challenger accident. Ed.], namely that individuals overseeing the launch had to prove they 

were not ready to ‘go,’ rather than prove they were ready for launch. (p 60)

Adm. Truly: I’ve gone to Nat’l Research Council and asked for a blue ribbon study--to get some advice where 

we might put future funding and focus our efforts and do it in a coordinated way so we don’t duplicate efforts 

already underway. (p 62)

Adm. Truly: Revisions to the weather LCC have been initiated. Each will be clearly documented, along with 

rationale, and the required sensors and instrumentation to assure it is met. (p 65)

Note (JCW): Although the Heritage Committee [Heritage, 1988] did provide rationale for their proposed 

rules, subsequent changes have not been so justified, providing the motivation for the present pair of reports.

Maj Gen. Cromer: The Weather Office (Det 11) has developed both checklists for each LCC that state the data 

and mandatory instrumentation required to evaluate each criterion, and new CCTV displays that show the 

current and T-0 forecast for each constraint. In addition, a Senior Weather Detachment representative will be 

collocated with the Mission Director to provide face to face advice on marginal weather conditions and more 

in-depth insight into weather and resultant risks.

Note (JTM): Both NASA and the AF later evaluated this recommendation with respect to the KSC and the 

Eastern Range and declined it because they did not want to separate the weather person from his/her weather 

data and team, especially given the very dynamic weather patterns in America’s ‘lightning capital. However, 

the Western Range has a different concept of operations that suits their geographical layout and weather 

patterns better and they do station a weather officer with the Mission Director. (p 79)
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Chairman Nelson to BG Chapman: To what degree is the 1000V/m criterion a matter of discussion among AF 

weather experts?

Gen. Chapman: Criterion not discussed with me. But I’d like to add that it is an operational criterion that is 

very common throughout the AF and the Army or those commands that I support.

Note: Rep. Nelson was apparently referring to the field mill criterion in the Shuttle LLCC (see Appendix I 

Section A1.6) since the ELVs did not have such a rule at the time. It’s doubtful BG Chapman understood Rep. 

Nelson’s question correctly. The General was likely referring to electrical constraints other commands have 

for different types of operations that are also sensitive to electrical discharges. (p88)

Chairman Nelson to Cromer: Where are you applying the field mill LCC?

Gen. Cromer: Field Mill System only exists at Patrick (CCAFS and KSC). We can’t apply it at Vandenberg 

because there’s no system there. We’ll deploy it where appropriate. I don’t know that we have enough 

prevalent conditions for induced lightning on West Coast to apply field mill data there. (p 89)

(Note: Although Field Mills existed at a few locations around the world, the Field Mill network at CCAFS was 

probably the only system in existence used for operations)

Chairman Nelson to Chapman: Communication between your weather specialists and the Launch Director 

broke down. Neither completely communicated to the other their impression of the current situation. What do 

you intend to do to implement from what we’ve learned from our mistakes?

Gen. Chapman: We will emphasize what we always do throughout our support to all our NASA, Air Force and 

Army customers: go directly to them and ensure we understand their requirements. We will then document our 

procedures in detailed checklists, as General Cromer mentioned, to ensure we haven’t missed anything. 

Checklists will be a very important part of our process as they are throughout the Air Force. (p 90)

Chairman Nelson: The AF specialists were surprised to learn the count was proceeding. I wonder if the rigid 

chain of command authority, the checklist mentality would be an impingement upon expressing a difference of 

opinion?

Chapman: No sir, I don’t think so. We have a questioning attitude at all times.

Chairman Nelson: How will you tell your specialists to communicate their level of confidence? Chapman: 

Difficult question to answer. In each case there is a judgment call. We will do as our customer wants and as 

Admiral Truly recommended and require clear and convincing evidence.

Note: Level of confidence is now expressed in Probabilities for Forecasts, but for final 

evaluations/assessments of observed weather conditions, the Launch Weather Team must be ‘Clearly 

Convinced’ the constraints have been met (i.e. are Green) otherwise they are Red. (p 90)

Chairman Nelson to Truly and McCartney: Did the Launch Director or the weather office have the final 

responsibility to ensure the weather requirement were met. Truly and McCartney to Nelson: Clearly the 

Launch Director had the final responsibility.

(Note: On the Launch Weather Team, the Senior Weather Officer has the final responsibility for the 

assessment communicated to the Launch Director. However, as stated above all LWT members must be 

‘clearly convinced LLCC are met, otherwise LLCC are Red) (p 92)
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Chairman Nelson asked Truly about a Nowcasting Facility he’d heard about. Truly referenced the NRC

assessment and report on weather support to America’s Space Program which recommended a technology 

transition facility co-located with forecasters. Truly said NASA was in process of assessing the NRCs 

recommendation. (p 94)

(Comment (JTM): That ‘Nowcasting Facility’ does not do forecasting but does Technology Transition based 

on customer taskings. It is called the Applied Meteorology Unit, was formed in 1991, is co-located with the AF 

forecasters at CCAFS, and has been providing very valuable tailored weather support products to both 

manned and unmanned space programs ever since-- see Sections 1.3 and 5.2.3.)

Gen. McCartney: It was clearly a matter of everyone there in the launch decision team, the Launch Director, 

the Launch Vehicle Manager, and the Mission Director felt it was a clear situation where the mission would 

not be jeopardized by launching. In retrospect, it was not the right decision to make and as the Senior Manager 

there, if I had any indication, I, like Admiral Truly, would have stopped it immediately. We had discussed all 

afternoon, well before the launch, there would be no waiver of any criteria. The criteria were there, they would 

be followed, and there was never any intent to waive any of those criteria. So it was clearly a situation of 

everyone felt the criteria were adequate, it was being met, and the decision was made to go. In retrospect it 

was the wrong decision. (pp 92-93)

(Comment (JTM): The exchange continued. The weather personnel thought they’d communicated to the launch

team that the situation was ‘close’ and ‘hairy’ and it was the launch team’s responsibility to make the final 

assessment whether the weather criteria were met; while the launch team, knowing the weather was a concern 

and having discussed weather all afternoon, remembers hearing weather personnel say ‘the criteria are met’ 

and ‘weather is GO for launch.’ Thus weather personnel were surprised the launch proceeded, and the launch 

team was surprised to learn they should have realized it was barely acceptable to launch according to the 

criteria, since critical airplane and weather radar data were missing, and rawinsonde data was questionable 

during rain.) (pp 93-94).

Chairman Nelson read the following from a transcript of communications between Cape Weather and the 

launch team 4 minutes before launch: “We are monitoring our field mills right now and the (electric) potential 

is up east and right about the SLF which is just outside the 5 mile limit. Over the pad itself we don’t show any 

potential for lightning, and to the east of the pad, which is the path of the missile, it looks good and we haven’t 

had any lightning within 10 nm of the Cape.” (p 94)

(Comment (JTM): Two concerns: 1. The statements “(Electric) potential is up east”, and later: “to the east of 

the pad, which is the path of the missile, it looks good” appear to contradict. That aside, there are no field 

mills or other measurements over water, thus one cannot state ‘there’s no potential.’ 2. Reference the 

statement: “Over the pad itself we don’t show any potential for lightning”: At the time, the potential near the 

pad was in process of transitioning from high negative fields to high positive fields, that is, the field was 

passing through low values on its way to high values of the opposite polarity. It’s just an indication of the 

atmosphere’s disturbed state and no guarantee the electric potential isn’t high along the flight path. If one just 

views an electric field mill value in isolation and not its temporal trends, and the spatial distribution of electric 

fields surrounding the mill and along the flight path, one will be misled regarding the danger. The field mill 

display system available to the weather team includes three important displays: 1. A display of individual field 

mill values; 2. A display based on readings from all the other field mills, of contours connecting values of 

equal potential for a spatial view of the surrounding fields; and 3. A display, of ‘strip charts, with plots of the 

time history of each field mill’s values over time. This allows the Launch Weather Team to determine if each 

field mill has been varying little, at fair weather values, or is fluctuating widely between positive and negative 

electric polarities.)
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Chairman Nelson to Truly: Why does NASA use field mills for Shuttle but not for ELVs?

Adm. Truly: I do not have an answer but in hindsight it was a mistake. (p 95)

(Comment (JCW): This is really the key question.)

Adm. Truly then addressed an earlier suggestion by the AF Det 11 Weather Commander that their weather 

Go/No Go calls might be more conservative for the manned Shuttle missions than for the unmanned ELV 

launches. Truly said, ”I don’t think NASA has any launch today that would require a triggered lightning 

potential to be different for an expensive satellite that is going to launch from the Cape or anywhere else, as 

compared to a Shuttle.” Nelson agreed and said that while there may be differences with the way they are put 

together and in their redundancies, there should be no differences in the way weather is applied and evaluated. 

(p 97)

Chairman Nelson to Cromer: An aircraft was not available. What will you do in the future?

Gen. Cromer: If we can not verify a clear line of sight along the flight path and no aircraft are available, we 

will cancel the launch.

(Comment (JTM): While an aircraft can provide critical data under some weather situations that would make 

the difference between whether the launch weather team is clearly convinced the LLCC have been satisfied, 

there are many situations where the nature of the clouds along the flight path, their type, thickness, 

temperature levels, history, etc, does not require data from an aircraft because proper data is available from 

other sources.) (ibid)

Gen. McCartney to Nelson: Air Force weather has greatly improved their displays. The presentation of data is 

a significant improvement to what decision makers have had before. (pp 97-98)

Gen. McCartney and Cromer to Nelson: A Senior Weather Officer will be available in the blockhouse, eye ball

to eyeball with the launch director and launch team rather than on the net, so they can question him or her and 

assist them in interpreting the weather data they are receiving.

(Comment (JTM): Western Range: Weather Officer is located with the launch team. Eastern Range: Shuttle 

management considered proposal but decided Weather Officer should be co-located with all the weather data, 

especially since the weather can change so rapidly. They wanted all training on how to interpret data done 

before countdown supplemented over net if needed.) (p 98)

George Rodney--Director Safety, Reliability, Maintainability, and Quality Assurance (SRM&QA) at NASA 

HQ—opening statement: I chose not to go to the launch and also did not send any of my senior managers 

because I considered it a low risk event of a highly mature system and crew. This is a good example of a 

Lesson Learned. “We are continually in a high risk business. There isn’t any such thing as a low risk operation 

in our business, and we can never be complacent with that thought.” (p 100)

Mr. Rodney--Written Statement: How can such an accident be possible in the new NASA safety conscious 

environment at NASA? Three factors: A. Many successful launches conducted at KSC in conditions that were 

not blue sky and sunny. The veteran AC 67 launch team may have been less than appropriately sensitive to the 

hazards imposed by marginal conditions and may have been led to depend unquestionably on the LCC to 

protect the vehicle from weather induced hazards. B. Veteran launch teams like the AC 67 team have can-do 

attitudes they can handle any anomalies that arise in a normal countdown. While hindsight shows resolution of 

some AC 67 deviations was inappropriate, the team members believed they were reviewing, processing and 

resolving these deviations correctly and in a manner consistent with past successful launches. C. I believe the 
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ELV side of NASA has not received comparable SRM&QA emphasis when compared to Shuttle. I believe 

these underlying factors contributed to what the (Busse) board described as a lack of awareness of the 

“...indications that the weather was unfavorable and that specifically there was a lightning hazard.” The 

additional constraints, clarification of procedures, and oversight measures that the new launch decision process 

will impose, will counteract such unconscious group predispositions and group dynamics. (pp 103-104)

(Comment (JTM): ‘Group predispositions and group dynamics’ were also threats to the weather support 

process, especially with the new, post AC 67 lightning LCC. The new LCC were much more complicated and 

thus prone to misinterpretation, confusion, and thus propensity to being dominated by the loudest voice(s). 

Consequently, the Senior Weather Officer position was created to oversee the entire process and ensure group 

dynamics did not bias the evaluation. The Senior Weather Officer ensures all roles and responsibilities are 

properly executed, all LCC are properly evaluated, and the evaluation results communicated according to the 

new rules/guidelines).

Chairman Nelson to Rodney: Everybody now embraces the idea you should use field mills as another measure 

for expendable rockets, in addition to the Space Shuttle using them. We had to learn through a painful 

experience that’s what we are going to do. What’s your conclusion as to why somebody wouldn’t have 

concluded that anyway, without having to go through and lose an Atlas?

Mr. Rodney: We had planned to bounce the Shuttle against the ELVs and other programs, but it hadn’t 

occurred at the time of AC 67. (p 108)

Chairman Nelson: So since NASA had gotten into a mindset they were now having to get rid of ELVs, that 

they really didn’t worry about the launch criteria, having it updated to what otherwise would be using more 

recent technical data, that they didn’t have when that criteria was established years ago. Is there truth to that? 

(ibid)

Rodney: Yes sir, and it was coming off a very acceptable successful ELV launch rate. (ibid)

Chairman Nelson: Thank you all for a most enlightening hearing.

(Comment (JTM): Important issues related to accident the Hearing failed to consider:

Prior to launch, the Duty Forecaster issued a Lightning Advisory for lightning within 5nm based on the very 

high 8000 V/m Field Mill readings. The Advisory should have prevented launch. However the forecaster’s 

shift ended before launch which allowed the forecaster’s successor to cancel the Lightning Advisory and the 

countdown to proceed. When the Lightning Advisory was canceled, the Field Mill readings were still 8000V/m 

and remained so at launch.

The Lightning Advisory discussed above was in effect when the ‘GO’ was given for launch. Weather radar was 

not operational due to upgrade—major data source for evaluating LLCC. When discussing validity of using 

balloon data as a substitute for the missing aircraft, data in evaluating whether clouds extended above the 

freezing level and violated the Thick Cloud LLCC, the Hearings failed to consider that the balloon blows 

downstream with the wind. Consequently the moisture data the balloon was measuring may not have 

represented the moisture present and whether clouds were likely present above the freezing level along the 

flight path.

Rain, heavy at times, was reported throughout CCAFS and KSC. This, and the presence of nearby 

thunderstorms, was not consistent with either a drying atmosphere aloft or with cloud tops below the freezing 

level which were necessary in order to declare the Thick Cloud LLCC was Green. The weather team helped 

justify their ‘Go for Launch’ decision based on the decrease of several nearby field mills from very large 

values to near zero. Hearing participants failed to mention that fact by itself was insufficient unless it included 
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an evaluation of the electric field contours and field mill strip charts. This would have clearly demonstrated to 

the Congressmen that the observed electric field decrease to zero was just part of a larger very disturbed 

electric field which was swinging from large positive values through zero to large negative values (and vice 

versa . In fact, the electric field did continue changing polarity by thus passing through zero to 8 kV/m near T0.

Many major signs of potentially dangerous electric fields aloft were present simultaneously: high surface 

electric fields, locally heavy rain, upstream thunderstorms and lightning with upper winds capable of 

advecting charge laden debris cloud over CCAFS. The Apollo XII incident in 1969, AC 38 in 1976 (discussed 

earlier in this report) and AC 67 in 1987, though years apart, are startling in terms of the similarities between 

the weather conditions, faulty or ambiguous commit criteria and faulty evaluation processes for applying the 

criteria. The Apollo XII and AC 67 incidents were triggered lightning events, and the AC 38 incident was 

probably also such an event. The fact that faulty processes, so ingrained and numerous, do not occur 

overnight, likely indicates a failure of higher headquarters (HHQ) to fulfill their oversight and insight 

responsibilities. There was no indication of effective HHQ inspections, staff assistance visits, simulations, etc.)

5.1 Infrastructure

Except as noted below in this section, the weather infrastructure at KSC/CCAFS remained the same as that 

presented in Section 4.1 during the period covered by this chapter, but as described below, a number of 

improvements were made.

5.1.1 LPLWS Upgrade

In 1988 NASA established requirements for an upgrade to its network of field mills which the Range called 

the Launch Pad Lightning Warning System or LPLWS. A NASA Requirements Document (79K32611) was 

released by the joint NASA/ESMC LPLWS Task Team. The Phase I requirements were (Michael Maier, CSR, 

private communication):

• Add new field mill sites to provide coverage of all areas of interest

• Conduct survey to verify location of all field mills

• Replace the aging Tektronix monitor and strip chart recorders in the CCFF

• Improve exposure of all field mills by clearing sites per the standard included in the requirement

• Conduct an Operational Acceptance Test of the LPLWS to be overseen by a Det 11 2 WS observer

• Establish configuration management and control of LPLWS. The configuration of the LPLWS was 

frozen for the Operational Acceptance test (OAT) in December 1987 although three sites were not 

certified

• Establish appropriate configuration identification for all aspects of the LPLWS

• Begin a LPLWS replacement project (Phase II) where NASA would design and provide improved 

field mill sensors and ESMC would provide improved processing and display capability

A scientist, Michael Maier, who was personally involved in the infrastructure upgrades, recalled that the goal 

was to certify LPLWS Phase I as operational prior to the return to flight of Space Shuttle in October 1988 (See 

Appendix VII). The ultimate goal was a “Phase II” project to replace the existing LPLWS with new mills of a 

better, more modern design. This was not completed until 1997.

For Phase II a panel of experts -- Krider, Charles B. Moore (NMIMT), and Willett -- was convened by John 

McBrearty (KSC/TM-PCO-3) to make recommendations for the design of new field mill sensors, the 

associated network data system, and the data-display system, and to review proposed new designs when they 

became available. The panel met at KSC on 21 September 1987 to develop design recommendations. The 

panel formally transmitted nine recommendations for Phase I and 23 recommendations for Phase II to NASA 

in a letter dated 28 September 1987 (unpublished). The Phase I recommendations dealt with improved 

calibration methods, site inspection and maintenance and concepts of operations. They concluded with a 
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recommendation to commence Phase II as soon as possible. The Phase II recommendations dealt with many 

facets of the engineering design (both hardware and software) of the next generation of field mills. An 

important suggestion was to mount the mills in an inverted position with the sensor head pointing downward 

rather than upward as was customary at the time. This dramatically reduced the amount of cleaning and 

maintenance required by eliminating contamination by bird droppings and minimizing the amount of dirt and 

sea salt that accumulated on the sensor.

The field mill panel met again at the Eastern Space and Missile Center on 17-19 February 1988 and at the 

University of Arizona in Tucson on 4 March 1988 to review and comment on a proposed sensor design and on 

the performance of a prototype that had been assembled by Michael Stewart for NASA/MSFC. As a result, a 

set of eighteen additional recommendations for the electronic design was submitted to NASA in a letter dated 

22 March 1988 (unpublished). The panel apparently reviewed the draft Request for Proposals for the new 

LPLWS in early 1989. Presumably contract award, fabrication, installation, and calibration proceeded over the 

next few years, but operational acceptance of the new system was not completed until 1997. See Appendix 

VIII, Section A8.1.1 for a description of the current, now seriously aging, LPLWS.

5.1.2 Lightning Detection and Ranging (LDAR)

As a direct consequence of AC 67, the LDAR system which was developed and tested as described in section 

3.4.5.3 was made an operational system. LDAR provided additional lead time to issue warnings before cloud 

to ground lightning occurred which led to the establishment of a “two phase” lightning policy at KSC and 

CCAFS in the mid-90s. A “Phase I Lightning Watch” is issued when lightning is forecast within 5 nautical 

miles of a designated facility within 30 minutes, and a “Phase II Lightning Warning” is issued when lightning 

is “immanent or occurring” within 5 nmi. Ongoing sensitive operations may continue under a Phase I 

condition but must be shut down immediately when Phase II is issued. Previously, only lightning warnings 

were issued with the 30 minute lead time and sensitive operations had to stop immediately. There were 

frequent false alarms resulting in unnecessary work stoppages. Adoption of the two phase lightning policy 

saves KSC/CCAFS several million dollars in labor costs annually from reduced down time.

5.1.3 CGLSS Upgrade

After 1984, the system continued to be developed and evaluated and was eventually accepted into the ER 

inventory as a fully certified system on 24 July 1989. Between 1989 and 1994, the CGLSS was upgraded to a 

network of five LLP (Lightning Location and Prediction, Inc.) Model 141 Advanced Lightning Direction 

Finders (ALDFs), and during 1995-1998, the system was converted to a 6-station, short-baseline network of 

medium-gain IMPACT (IMproved Accuracy from Combined Technology) sensors (Cummins et al., 1998).

The present CGLSS system has an effective range of about 100 km and covers the KSC-ER launch and 

operations areas with good accuracy and high detection efficiency (Ward et al, 2008). The CGLSS is operated 

24 hours a day, 7 days a week by the Range Technical Services (RTS) Contractor, and the data are sent in realtime to the 45 WS for use in operations.

5.1.4 Radar Display Upgrade

When the WSR-74C was acquired by the Eastern Range in 1984, it used display software developed by 

McGill University. In 1997, this was replaced with commercial software (“IRIS”) marketed by Sigmet, Inc. 

The IRIS software permitted the generation of tailored launch support products such as radar cross sections 

that could not be generated by the McGill package.

5.1.5 Additional Eastern Range Systems

The Eastern Range network of boundary layer wind profilers (Appendix VIII section A8.4.2), rain gauges 

(Appendix VIII section A8.3.4) and offshore data buoys (Appendix VIII section A8.3.5) were all added to the 

ER infrastructure during the 1990s. The National Weather Service at Melbourne began its exploration of the 
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operational use of local, high-resolution numerical weather prediction systems (Appendix VIII, Section A8.6) 

during the same period.

The 50 MHz Doppler Radar Wind Profiler (Appendix VIII section A8.4.2) was built at KSC by Tycho, Inc. as 

an experimental proof of concept test bed in 1988 under the direction of the Shuttle Natural Environments 

Branch at Marshall Spaceflight Center. MSFC soon determined that the standard commercial “consensus” 

algorithm provided by Tycho was inadequate for either research or operational applications. As a result, they 

developed a new “median-filter first-guess” (MFFG) algorithm that provided more frequent, more accurate 

wind profiles than the consensus methodology (Schumann et al., 1999). The original MFFG required more 

computational resources than the wind profiler hardware could support so it could not be used in real time for 

operations, but provided excellent data for evaluating the potential value of the instrument. An evaluation by 

the AMU (section 5.2.3 below) in 1992 showed that the DRWP and MFFG combination produced wind 

profiles of high quality suitable for operations. As a result, the AMU was tasked to develop an operational 

version of the MFFG software. By reducing the size and increasing the efficiency of the code they were able to 

make it run on the operational computer system and added a real-time user interface for day of launch quality 

control.

5.1.6 Kodiak Alaska Launch Complex

To support a 2001 launch of an Athena vehicle carrying Air Force and NASA payloads (see Section 5.3 

below) from the Kodiak, Alaska spaceport, an adequate weather infrastructure had to be created. Prior to the 

Athena mission, the site had no weather radar or lightning detectors and only two ten-meter wind towers. 

Working with the 45th Space Wing, the Alaskan Aerospace Development Corporation and Lockheed Martin 

Corporation, The KSC Weather Office coordinated procurement, testing and installation of a basic weather 

radar, a lightning detector, a surface field mill, upper air balloons for measuring profiles of wind and 

thermodynamic variables, and additional surface wind sensors. In addition, on day of launch an aircraft was 

contracted to provide real-time weather observations for LLCC evaluation.

5.2 Organization

5.2.0 Space Shuttle Headquarters Support Office/Weather Office

In the late 1980s, the Space Shuttle Program created a NASA headquarters office to oversee all weather 

support to the program including launch support at KSC and landing support at KSC, WSSH, Edwards AFB 

and the overseas emergency landing sites. The office was staffed by two senior civilians and a senior military 

liaison officer from the Air Force. Although the formal title was the Space Shuttle Headquarters Support 

Office/Weather Office, it was generally known as the Weather Support Office (WSO).

5.2.1 Lightning Advisory Panel

Following the AC 67 disaster, NASA and the Air Force were eager to identify an existing instrumented aircraft 

that could measure electric fields aloft in support of space-launch operations -- an operational ABFM. A joint 

workshop was held in early 1988 at the Cape Canaveral Air Force Station (CCAFS), during which many 

scientists familiar with airborne field measurements outlined an appropriate system design and a plan of flight 

operations (Barnes and Metcalf, 1988). A few individual scientists were also asked by NASA/WSO or Air 

Force Space Command to evaluate an ABFM that had been developed by Stanford Research Institute (SRI) --

at that time the only, appropriately instrumented, high-performance aircraft -- which was eventually 

determined not to be suitable for launch support.

A group of scientists and engineers led by Hugh Christian at the NASA Marshall Space Flight Center (MSFC) 

took their cue from the CCAFS workshop, in which they participated vigorously. In 1988 they began a major 

effort to instrument another Learjet as a demonstration project. The primary goal of the MSFC group, after 

achieving a credible calibration, was to obtain statistics on the field magnitudes aloft during conditions that 
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violated the LLCC of the time. It was expected that such statistics could be used to make these LLCC less 

restrictive. MSFC conducted four field deployments during 1990, 1991, and 1992 to gather data for statistical 

analysis, as described in Section 5.4.1 on the ABFM I.

Because of the potential consequences to safety of any change in the LLCC, around 1990 the newly formed 

NASA WSO (see 5.2.0 above) and the Air Force Space Division asked an ad hoc group of experts to review 

MSFC's efforts to calibrate its ABFM. These scientists, who became known collectively as the Peer Review 

Committee (PRC), were drawn both from the old "Heritage Committee" (Heritage, 1988) and from the more 

recent individual efforts to evaluate the SRI aircraft. After the first year of the MSFC field program, the PRC's 

role expanded to reviewing the statistical significance of data collected by ABFM I for revision of the LLCC.

Statisticians from The Aerospace Corporation were enlisted to help with this effort.

In 1992 MSFC formally proposed some LLCC changes that were based on the summer ABFM I dataset. In 

response, the NASA/WSO and the Air Force 45th Weather Squadron at CCAFS (45WS) formally agreed that 

outside experts in the fields of lightning and atmospheric electricity were needed to evaluate this proposal and 

any future changes to the LLCC. The formerly ad hoc PRC became officially recognized as the standing 

committee for that purpose, although its role remained informal and no official charter was written. The

original membership of the standing committee consisted of E. Philip Krider (University of Arizona, Chair), 

James E. Dye (NCAR), Harry Koons (Aerospace Corp.), W. David Rust (NOAA), Richard L. Walterscheid 

(Aerospace Corp.), and John C. Willett (Air Force Geophysics Laboratory). In addition to having the needed 

expertise, the members represented a broad cross section of the relevant academic and government 

organizations. (The most appropriate NASA representative, Hugh Christian, was not on the PRC because it 

was his ABFM program that was under review.)

The PRC held its first face-to-face meeting at MSFC in August, 1992, to review the first MSFC-proposed rule 

changes. Over time the PRC's role gradually expanded from reviewing the proposals of others to include 

drafting its own proposed rule changes and even recommending additional experiments that could increase 

safety and launch availability. The most significant example of the latter was its December, 1999, 

recommendation to the KSC Weather Office to have an ABFM II experiment. A detailed outline of the 

PRC/LAP's activities is given in Appendix II, and a description of its operating methods can be found in 

Section 5.5.1.

James E. Dye left the PRC sometime after March, 1994, and was reappointed in December, 2003, while he 

was serving as the PI of the ABFM II campaign (see Section 6.4). In the meantime, the name, ‘PRC,’ was 

changed to ' Lightning Advisory Panel (LAP)' in February, 1997, when it was provided with a still-unofficial 

charter, and in February, 1999, Hugh Christian was added to bring a NASA perspective to the LAP. Sadly, 

Harry Koons passed away suddenly and unexpectedly on 11 May 2005, and his statistical expertise, 

penetrating logic, and clear expression were missed by all. Eventually, Dr. Koons was replaced by Paul 

O'Brien (also of the Aerospace Corporation) in October, 2007. The current membership of the LAP is Krider 

(chairman), Christian, Dye, O'Brien, Rust, Walterscheid, and Willett.

5.2.2 KSC Weather Office

In the late 1980’s, Shuttle Program managers at KSC established a local office to oversee the weather 

infrastructure and weather research it was funding in whole or in part at KSC and the Eastern Range. The 

office was initially called the KSC Weather Projects Management Office, but later the name was shortened to 

the KSC Weather Office.

As part of a NASA cost-cutting reorganization in 1995, the agency-wide responsibility for weather support to 

the Shuttle program was transferred from the NASA Headquarters Weather Office (which was abolished) to 

the KSC Weather Office. Shortly thereafter, KSC was named the lead Center for launch and payload 

processing for NASA expendable launch vehicles (ELV) regardless of where launched. That resulted in the 
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KSC Weather Office also being responsible for weather support to NASA ELV launches from sites as diverse 

as the Eastern and Western Ranges, Kwajalein Atoll, Wallops Island, VA and Kodiak, Alaska.

5.2.3 Applied Meteorology Unit (AMU)

In 1991 NASA, the Air Force and the National Weather Service collaborated in the establishment of an 

Applied Meteorology Unit co-located with Range Weather Operations at CCAFS and managed by the KSC 

Weather Office, as recommended by the Theon and NRC reports (see Section 5.0.2). The AMU provides 

technology development, evaluation and transition services to the 45WS, SMG and the NWS office at 

Melbourne, FL as well as directly to the Shuttle program. Many of the highly specialized tools used for 

weather support to both manned and unmanned operations on the Eastern Range and at KSC were developed 

by or transitioned to operations by the AMU (Bauman et al., 2004). 

5.3 Operations

The period covered by this chapter was free from major weather-related accidents or mishaps. On 29 

September 2001, the first launch of a large rocket from the Kodiak Alaska launch complex took place 

successfully. An Athena booster placed in orbit the NASA Starshine satellite and three Air Force satellites: 

PICO, PC Sat and Sapphire.

5.4 Research

The period following AC 67 was one of vigorous research activity into atmospheric electricity, lightning and 

triggered lightning. Methodologies ranged from flying instrumented aircraft into thunderstorm-associated 

clouds to triggering lightning deliberately with small rockets. Several of the major experimental programs are 

described below after a general discussion of the methodologies for making airborne electric field 

measurements.

5.4.0 Methodologies for Airborne Electric Field Measurements

Before presenting a summary of the airborne studies conducted near KSC, we will first discuss the 

measurement of electric fields from an aircraft platform and the challenges encountered. The measurement of 

electric fields using rocket-borne sensors will encounter similar difficulties but neither rocket nor balloon 

measurements are discussed here because our focus is on aircraft measurements. Airborne measurements of 

the electric field inside clouds, especially thunderstorms, are difficult because of the distortion of the ambient 

field by the aircraft and the extra field that is created by charge on the aircraft due to the engine exhaust, the 

impaction of hydrometeors, and corona discharge. Although the three spatial components of the electric field 

vector and the charge (or potential) on the aircraft itself can be determined from four independent 

measurements, five or more sensors provide the ability to verify the calibration and permit a redundant 

determination of all four variables. Some redundancy is necessary, and knowledge of charge on the aircraft is 

helpful, when assessing the accuracy of the ambient-field measurement. A further complication is that space 

charge is always being emitted by an aircraft in the high-field environment of thunderstorms. If the space 

charge passes close to one or more of the sensors, it can contaminate the reading or make the measurement of 

one or more components of the ambient field impossible (Jones et al., 1993).

Most electric field sensors used on research aircraft in recent years have been of the rotating-vane type, i.e. 

field mills, such as the ones described by Bailey and Anderson (1987), Winn (1993), and more recently by 

Bateman et al., (2007). A grounded, rotating, segmented vane, or shutter, alternately exposes and shields fixed 

sensor plates to/from the electric field. Some aircraft flown in the studies near KSC and elsewhere have used 

cylindrical electric field mills of the type described by Kasemir (1964, 1972), wherein rotating sensor plates 

are directly exposed to the electric field. The use of one cylindrical mill permits the measurement of two 

spatial components of the field, but using two mills, for example, one mounted axially on the nose and one 

mounted transversely under the fuselage, permits the measurement of three components of the field. The incloud measurements from a transversely mounted cylindrical mill can be compromised by the impaction of 
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hydrometeors on the sensing plates, however. For the NCAR sailplane, a small diameter, Kasemir-type, 

cylindrical field mill designed by William Winn was mounted on a boom that was centered ahead of the nose 

(Dye et al., 1989). Later a different type of cylindrical mill was used on the sailplane in CaPE. This mill had a 

cylindrical, rotating outer shutter that alternately exposed and covered fixed stator plates on the top and bottom 

and then on the left and right so that the charge induced on each plate could be measured as well as the charge 

on the aircraft (Dye et al., 1989).

A calibration of the full field-mill system (as opposed to a calibration of each individual field mill) is the most 

difficult requirement to achieve. This calibration is necessary to separate the effects of the aircraft itself from 

those of the ambient field. Roll and pitch maneuvers either in fair weather fields in clear air or in quasi-steady 

fields below anvils is the method that is most commonly used procedure to calibrate the aircraft measurements.

A fair-weather calibration makes severe demands of the instrumentation, because the individual sensors must 

be capable of a wide dynamic-range to accurately measure fields ranging from a few tens of V/m to hundreds 

of kV/m. The fields below anvils are often not as steady as one would like. Another part of the procedure is to 

artificially charge the aircraft in fair weather with an on-board high voltage supply and corona "stinger" to 

determine the response of the individual mills to this charge. For example, Jones et al., (1991, Vol I) and Jones 

et al. (1993) used a stinger to calibrate the New Mexico Tech SPTVAR aircraft. Mach and Koshak (2007) 

have described a mathematical procedure that was used to calibrate four different aircraft, including the 

Citation that was used in the ABFM II campaign (2000-2001). An early version of this procedure was used for 

the calibration of the Lear jet 28/29 that was used in ABFM I (1990-1992). Other system calibration 

techniques include using a numerical solution of Laplace’s equation on a mesh representation of the CV-580 

aircraft (Laroche, 1986) and laboratory measurements on a scale model (Laroche et al., 1989 for a French 

Transall aircraft; and Kositsky et al., 1991 for the Aeromet Learjet 36A). An absolute calibration of a field mill 

system can also be accomplished by flying past a calibrated field mill on the ground (Mach and Koshak, 

2007), on a tethered balloon (Winn, 1993)), or by in-flight comparisons with a previously calibrated aircraft.

Winn (1993) proposed a novel calibration method that addresses both the distortion of the external field by the 

aircraft and the problems caused by aircraft charging. This method does not require systematic placement, or 

even knowledge of the placement, of the individual field mills on the aircraft, nor does it require knowledge of 

the magnitude and direction of the ambient-field. The only requirements are that the ambient field be constant 

in magnitude and direction during aircraft maneuvers and that the field sensed by each mill be a linear 

combination of the three spatial components of the ambient field vector and the charge on the aircraft. One 

drawback of Winn’s method is that it is not able to directly determine the aircraft charge (or potential). Mo et 

al. (1998) have taken advantage of Winn’s calibration method when instrumenting the South Dakota School of 

Mines and Technology T-28 aircraft with field mills. The sensors are placed in distinctly unconventional 

locations, where they are well away from the streams of space charge that the aircraft emits while flying in 

high fields.

5.4.1 Airborne Field Mill Program (ABFM I)

NASA sponsored an airborne measurement campaign in 1990-1992 to make direct measurements of the 

electric field vector in thunderstorm-related clouds, with the hope of gaining sufficient knowledge to make 

further improvements in the LLCC. This program comprised two summer campaigns, 1990 and 1991, and two 

winter campaigns, 1991 and 1992.

A Learjet 28/29 operated by NASA Langley Research Center and instrumented by NASA Marshall Space 

Flight Center was flown from 6 July to 21 August 1990, 14 February to 18 March 1991, 8 July to 25 August 

1991, and 19 January to 6 March 1992. The aircraft had turbofan engines and a ceiling of 45,000 ft , a flight 

duration of 1 to 1.5 hrs, a typical flight speed for penetrations of 200 m/s. It was instrumented with 5 field 

mills from MSFC, an early version of those described by Bateman et al., (2007). Calibration of the field mill 

system was an early version of the procedure described by Mach and Koshak (2007). The aircraft also flew an 
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ice patch that sensed the impaction of ice particles and a King liquid water sensor. The combination of these 

two instruments allowed differentiation between all-ice and mixed-phase regions.

The main objectives of this project were to evaluate the Lightning Launch Commit Criteria and to modify 

them as necessary to maintain the same or better level of safety while making the rules less restrictive. The 

goals of the campaigns were to quantify the electric field strengths inside each type of cloud identified in the 

LLCC as a function of the cloud type, characteristics, and development. Missions were developed for each 

cloud type ranging from mature thunderstorms, to developing cumulus, to anvils (attached and detached), 

debris clouds, thick clouds and disturbed weather. Categorizing the relationships between the cloud type, 

electric field, and radar reflectivity quickly became an overarching objective of the mission.

The flight strategy varied depending on the mission and type of cloud. The overriding objective was to

determine whether the cloud violated one or more of the LLCC, and if so which one(s), and to relate the 

measured electric field to the radar reflectivity of the cloud.

Mature thunderstorm: The main objective was to measure the decrease of the cloud electric field as a function 

of distance from the storm, and for this the aircraft was flown on repeated radials, toward and away from the 

cloud. There was an effort not to penetrate too deeply into the cloud, and the aircraft altitude was often varied 

between radials.

Developing cumulus: An effort was made to measure the electric field produced by cumulus clouds before the 

cloud top penetrated the zero degree isotherm. The aircraft made repeated cross-sections as close as possible to 

the cloud top and ascended with the cloud top. A particular interest was to quantify the altitude of the cloud 

top at first sign of electrification and the electric field strength when the cloud top reached the -10 and -20 °C

temperature levels.

Anvil clouds (both attached and detached): Anvils were studied with the primary objectives of determining 

how the electric field decayed with time and distance from the core of the storm. These studies were hampered 

because of the limited flight duration of the aircraft. Often, a cloud would be investigated until the plane had to 

depart due to low fuel, and then it would then be refueled and take-off for a second mission with the intent to 

continue penetrations of the same cloud. The flight strategy was to combine repeated radials along the length 

of the anvil from the core of the storm (for attached) to the end of cloud (axial), mixed with traverse crosssections. Altitudes were varied when allowed by the FAA air traffic controllers at the Miami and Jacksonville 

ARTCC. Spiral assents and descents were performed at the beginning and end of mission, if permitted.

Debris clouds: were investigated using the same flight strategies as for anvil clouds, except the flight legs were 

usually shorter and spirals were attempted more often.

Thick Clouds and Disturbed Weather: Similar flight strategies were used on both of these cloud types.

Generally, disturbed weather passes rapidly over the Cape during the wintertime and is associated with frontal 

systems. The plane typically flew paths that were perpendicular to the cloud motion and repeated penetrations 

of the same region of the cloud were attempted to follow regions of embedded convection. For “thick clouds”, 

the initial penetrations were made at cloud base and were often followed by cloud top penetrations. The bulk 

of the penetrations were made in the center of the cloud.

During the four aircraft deployments, penetrations were made through a variety of clouds at different stages of 

development. The winter studies were primarily of thick-layer clouds and clouds associated with disturbed 

weather, and the summer studies focused mainly on growing cumulus clouds, anvils, and debris clouds.

Measurements from the WSR-74C weather radar at Patrick Air Force Base were used extensively in the data 

analysis, especially to calculate Vertically Integrated Reflectivity (VIR) above 1 km and above 4 km

(approximately the 0 °C level). VIR-1 and VIR-4 (termed VII in the reports) are the sum of the reflectivity (in 
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dBZ) in a column above the aircraft from either 1 or 4 km to 15 km. (ABFM Analysis Group, 1991, 1992a, 

1992b, 1992c ). Both gridded Cartesian and radar-coordinate reflectivity values were used during real-time 

operations and for post flight analysis. However, only gridded reflectivity data were used when calculating 

VIR-1 and VIR-4. Because of calibration issues, the WSR-74C radar could not be used quantitatively to relate 

the measured electric fields to radar reflectivity in the ABFM-I campaign. Despite the calibration uncertainties, 

the measured reflectivities are believed to be close to the true values, and therefore, they can be used to 

characterize the clouds that were being investigated. (Merceret et al, 2008).

A summary of findings from the ABFM I program (MSFC Feb 92 and Oct 92 reports and Mach et al., 1992) 

follows:

ABFM I Winter studies

1. For thick layer clouds (Rule D in the reports) there is a strong correlation between the electric field 

inside the clouds and VIR-4 and also VIR-1. The correlation for VIR-1 was slightly better than for 

VIR-4. (ABFM Analysis Group, 1992a and 1992b). Significant electric fields might have been missed 

because of aircraft icing concerns while penetrating significant mixed phase clouds.

2. In layer clouds, the electric fields at the ground were not always correlated with electric fields aloft.

3. Fields ≥ 5 kV/m were not encountered in clouds at altitudes warmer than the 0 °C isotherm, and the 

highest altitudes with fields that were ≥ 5 kV/m were at temperatures near -10 °C, suggesting that the 

main electrical hazard was between 0 and -10 °C.

4. For disturbed weather clouds (Rule E in the reports) there was a strong correlation between the electric 

field aloft and VIR-4, and the correlation with VIR-1 was not as good as VIR-4.

5. For disturbed weather clouds all penetrations with fields > 5 kV/m were between 10 and 21 kft

(approximately 0 to -10 oC).

6. Fields measured at the ground under disturbed weather clouds correlated well with fields aloft, but 

there were 3 exceptions where fields at the surface were < 1 kV/m and fields aloft were > 5 kV/m.

7. Penetrations that showed fields > 3kV/m were generally associated with regions of higher reflectivity 

(embedded convection).

8. Cloud thickness and the electric field strength were very poorly correlated.

ABFM I Summer studies

1. The fields outside storms with lightning decreased to < 5 kV/m at a distance of 5 nm (9 km).

2. For the 87 cumulus clouds that were sampled, the observed electric field depended strongly on the 

cloud top height (temperature) as defined by the (uncalibrated) 10 dBZ reflectivity. The fields in 

clouds with 10 dBZ tops lower than the 0 oC level did not exceed 3 kV m-1

. Fields > 3-5 kVm-1 did not 

develop in cumulus clouds until the echo tops had grown above the -10 oC level (~ 6.4 km msl).

Cumulus clouds did not produce natural lightning until the tops were above the -20 °C level. Fields at 

the edge of clouds with echo tops higher than the -20 oC level could be > 50 kV m-1 (Merceret et al., 

2008)

3. As long as cumulus clouds were within 5-6 nm of the LPLWS network, that system was able to 

indicate a hazard aloft as long as the fields aloft were > 5 kV/m. There were no cases when the fields 

aloft were >5 kV/m and fields at the surface were <1 kV/m.

4. Measurements of fields as a function of distance from the cloud edge showed that even with fields of 

tens of kV m-1 inside electrically active convective clouds, the fields external to those clouds decayed 

to < 3 kV m-1 within 15 km of cloud edge as shown in Figure 5.4.1-1 This was true even for clouds 

that were producing lightning and had tops above -20 oC.
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Figure 5.4.1-1 Electric field magnitude as a function of distance from cloud edge

Note: Reproduced from Merceret et al. (2008), Figure 1

5.4.2 Convection and Precipitation/Electrification Experiment (CaPE)

CaPE was a large observational program conducted during July and August of 1991 with multi-agency 

funding and investigators from many organizations and universities. One of the five main research themes was 

identification of the relationships of the co-evolving wind, water and electric fields within convective clouds. 

The scientific overview and operations plan for CaPE (Foote, 1991) describes the many facilities, radars and 

aircraft used in CaPE and gives detailed flight plans and how they would be utilized to achieve the goals 

embodied in the five themes. In this section we briefly describe the operational strategy and some findings for 

Theme 1 – the co-evolution of wind, water and electric fields in convective clouds. A key contribution of 

CaPE compared to earlier studies of electrification in Florida cumulus clouds was the close coordination of 

detailed in-situ electrical and microphysical measurements with multi-parameter radar measurements of the 

same clouds.

The aircraft primarily involved in the electrification studies were the South Dakota School of Mines and 

Technology T-28, the NCAR Explorer Sailplane, the NCAR King Air, and the NOAA P-3 aircraft. In addition 

to the electric field measurements, all four of the aircraft had a capability for cloud microphysical 

measurements. Plans were also made to have the NASA Langley Learjet (concurrently flying for ABFM I) 

participate in coordinated flights with the other aircraft, but obligations to the ABFM I campaign precluded 

that possibility. The NASA ER-2 aircraft sometimes flew over storms at high altitude and made electric field, 

radar, and radiometric measurements. The Univ. of Wyoming King Air was instrumented with an array of 

microphysical sensors and a wind measuring capability and participated in the CaPE studies.

The T-28, NCAR King Air, and NCAR sailplane were all instrumented with rotating-vane field mill sensors 

that were built at New Mexico Tech and were similar to those described by Winn (1993). Additionally, the 

sailplane also flew a new Winn-designed, rotating cylindrical mill on a nose boom that had the capability of 
Page 57 of 234

measuring the induced charge on left, right, bottom, top and bottom plates (Dye et al., 1989). The field sensors 

on the NOAA P-3 were rotating-vane field mills designed by the Desert Research Institute. The calibration of 

the field mill system on each of these aircraft used pitch and bank maneuvers and artificial charging of the 

aircraft similar to what is described in Jones et al., 1993 and in section 5.4.1 of this document. An absolute 

calibration of the King Air system was not completed, but the values were thought to be approximately a 

factor of 2 high in comparison to flybys with other aircraft (Dye et al., 1992). Each of the 4 aircraft had a 

capability for measuring the cloud liquid water content and the concentrations of cloud and precipitation 

particles together with their sizes and types.

The two King Air aircraft made repeated, stacked penetrations of growing cumulus clouds in the early stage of

development, with the Wyoming King Air flying slightly above cloud base and the NCAR King Air flying at 

mid-cloud levels near 0 o

C and then ascending as the cloud top ascended until the electric field exceeded 10 

kV/m. When conditions permitted, the sailplane entered growing cumulus clouds from the side near the 

freezing level while both King Airs were investigating the cloud, and after finding updraft, spiraled upward in 

the cloud. Prior to the sailplane entering the cloud, the NCAR King Air would change to an altitude either well 

above or well below the sailplane. If the cloud evolved into a larger stage of development, both King Air 

aircraft would exit that cloud and look for other targets. At this point the T-28 was used to penetrate regions of 

stronger convection sometimes in coordination with the sailplane and or the P-3. The P-3 flew the NOAA 

under-fuselage 3 cm Doppler radar, so it was used for coordinated Doppler radar studies in addition to the 

electrical studies. The aircraft were closely coordinated with each other and with multiple Doppler radars from 

the CaPE operations center, where aircraft track could be superimposed on radar plots. The primary radars 

involved were the NCAR CP-2 Doppler 10 cm multi-parameter, polarization diversity radar and the NCAR 5 

cm Doppler radars CP-3 and CP-4, all 3 of which were dedicated to CaPE objectives. Additionally, the WSR88D NEXRAD radar at Melbourne and the WSR-74C radar at Patrick Air Force Base also scanned the storms 

with their normal scan strategy; and NMIMT supplied a mobile 3 cm dual polarization coherent and incoherent 

unit operated in conjunction with the CP-2.

Previous airborne and radar studies in Florida had shown (e.g. Hallett et al., 1978) that large raindrops form in 

the updrafts well before the cloud top reaches the freezing level. When the cloud grows above the freezing 

level the raindrops ascend in the updraft until a temperature of about -8 to -10 o

C is reached at which point 

some rain drops freeze and the cloud rapidly glaciates. The combined aircraft and multi-parameter radar 

studies from CaPE confirmed and strengthened this scenario. The polarization radar measurements from 

several investigators showed that a strong ZDR (differential reflectivity, a measure of mean particle 

oblateness) column indicative of large drops extended up to approximately -8 to -10 o

C, at that point the ZDR 

signal would decrease and become capped by an enhanced linear depolarization ratio (LDR) indicative of ice 

formation (Willis et al., 1994; French et al., 1996; Ramachandran et al., 1996; Jameson et al., 1996; and Bringi 

et al., 1997). The aircraft measurements of cumulus clouds and the KSC field mill network both showed that 

the initial electrification of cells occurred just after the appearance of an enhanced LDR signature. For 

example, in a study of 3 clouds that examined measurements from the KSC field mill network, Jameson et al., 

(1996) showed that the onset of electrification coincided with the appearance of a significant volume of ZDR 

(indicating large rain drops) above -7 °C level and was accompanied by the nearly simultaneous appearance of 

radar depolarization indicative of the supercooled drops beginning to freeze. This is illustrated in figure 5.4.2-1 

taken from Jameson et al.
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Figure 5.4.2-1 Radar elevation scan from Jameson et al., 1996

Similarly, measurements from the NCAR King Air and sailplane showed that some clouds with tops at -8 °C 

had very limited development of ice and at fields that were only 2 kV m-1

or less. Cases that had ice 

development but limited convective growth above the 7 km level (~-10 o

C) produced fields of 5 to 10 kV m-1

(Dye et al., 1992). An example of one growing cumulus that was penetrated by the King Air near or slightly 

above the 0 o

C level eight separate times is shown in figure 5.4.2-1. Even though the radar cloud top had 

previously reached almost -20 o

C, at 1420, the maximum observed field was ~3 kV m-1. The field did not 

exceed 10 kV m-1 until the pass at 1431 just after the development of new growth had started.
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Figure 5.4.2-2 Growing cumulus example adapted from Dye et al., 1992

Note: Figure represents local time. Top panel: Maximum reflectivity plotted as a function of altitude and time. 

The short solid dashes show the times of cloud penetrations by the NCAR King Air. Bottom panel: Plots of 

the vertical component of the electric field (EFZ), liquid water content (LWC), temperature, and vertical 

velocity (W) plotted as a function of time.

It should be noted that in the high plains such as in New Mexico, Montana and Colorado where cloud bases 

are much higher and cloud base temperatures are colder (typically 5 to 10 o

C compared to 15 to 20 oC in 

Florida), large drops do not form below the freezing level. The first precipitation is formed via an ice process: 

Small ice particles are nucleated in the cloud. These embryonic particles then grow by diffusional growth from 

transfer of water vapor from the air to the ice particles until they are large enough to fall relative to cloud 

droplets. As these ice crystals fall and grow sufficiently large they begin to collide with and accrete 

supercooled water droplets to become snow pellets (graupel). This ice phase process of precipitation 

development which dominates in the high plains (e.g. Dye et al., 1974) takes much longer than the 

development of precipitation through the warm rain process in Florida clouds.
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Unlike New Mexico where initial electrification is associated with cloud vertical growth, the initial 

electrification to fields >1 kV/m in Florida sometimes occurs during the decay phase of the cloud (Breed et al., 

1992) and can be seen in figure 5.4.2-2. The electrification of cumulus clouds in Florida is similar to that 

found for New Mexican clouds by Dye et al. (1989), but in Florida clouds often become electrified once the 

cloud top exceeds -7 km (-10 o

C), whereas in New Mexico cloud tops exceed 8 km (-20 oC) before electric 

fields become greatly enhanced (Dye et al., 1989, 1992). Even though millimeter-sized raindrops and 

reflectivity of 50 to 60 dBZ can develop in Florida cumulus clouds when cloud tops were wholly warmer than 

0 o

C, the combined aircraft and multi-parameter radar measurements showed that significant electric fields do

not develop until there is development of ice and mixed phased regions. Inside the clouds that did become 

significantly electrified, both millimetric graupel and numerous smaller ice particles were found in the 

presence of supercooled water (Dye et al., 1992; Willis et al., 1994; French et al., 1996; Bringi et al., 1997), 

thus showing the importance of the mixed phase region between -10 and -20 o

C for the electrification of 

Florida convective clouds.

5.4.3 Rocket Triggered Lightning Program (RTLP) Results

"Rocket-triggered lightning" is initiated by a small rocket towing a grounded wire aloft under a thunderstorm 

(St. Privat D'Allier Group, 1985). The rocket-and-wire technique for triggering lightning was pioneered by 

Newman et al. (1958, 1967). The key to its success is likely an observation by Brook et al. (1961) that the 

sufficiently rapid introduction of a grounded conductor into a high-field region might actually initiate the 

discharge.

The KSC Rocket-Triggered-Lightning Program (RTLP) provided an invaluable source of data on, and a better 

understanding of, lightning processes during a key period in the evolution of such knowledge. The primary 

triggering technique used in this program was so-called "classical triggering," in which a small rocket lifts a 

grounded wire aloft below an active thunderstorm, and produces a lightning discharge that is usually guided by 

the wire to the launch platform and any instrumentation connected thereto. The primary categories of results 

from the RTLP that are relevant for space operations are (1) data in support of test standards, (2) exposure of 

hardware to real lightning strikes, (3) test and calibration of lightning-detection systems, (4) better 

understanding of the triggering conditions, (5) better understanding of the "attachment process," and (6) data to

constrain theoretical models. Each of these areas is treated in turn below. Wherever possible, preference is 

given to references arising directly from the RTLP.

5.4.3.1 Data in Support of Test Standards

The best and most comprehensive dataset on the peak currents, peak current derivatives, and current rise times 

produced by subsequent return strokes was compiled by the RTLP, primarily during 1985, 1987, and 1988 

(Leteinturier et al., 1990, 1991). The largest peak currents produced by strikes to ground-based objects are 

generally found in first return strokes (e.g., Rakov and Uman, 2003, Table 4.4), which do not occur in rockettriggered flashes, but the subsequent return strokes in triggered and natural lighting are believed to be similar 

(e.g., Le Vine et al., 1989). Further, the peak electric-field derivatives and the rise times of the fast-rising 

portions in natural first and subsequent stroke waveforms are very similar (Bailey et al., 1988; Willett et al., 

1990; Krider et al., 1992; Willett and Krider, 2000). Finally, Willett et al. (1989a) found approximately linear 

relationships for peak derivative and rise time between field change and current in rocket-triggered return 

strokes. (These similarities themselves were first documented with data recorded during the RTLP.) Thus it is 

reasonable to conclude that the RTLP data on lightning current rise times and derivatives are directly relevant 

for lightning test standards, even for first strokes, although the peak currents, charge transfers, and action 

integrals are not.

Peak current derivatives and current rise times are especially relevant to the coupling of damaging signals into 

electromechanical and electronic systems. For example, the induced EMF in a conducting loop is directly 

proportional to the time derivative of the magnetic flux passing through that loop. The magnetic field 

derivative inside the loop, in turn, is directly proportional to the current derivative in the nearby conductor (or 
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lightning channel) that is producing the magnetic field. Further, the peak current that is induced in an inductive 

circuit is proportional (at least over short times) to the rate of rise (di/dt) of this nearby current. If the circuit of 

interest is protected by a Faraday shield, the penetration of the transient magnetic field through that shield, 

hence the induced current in the circuit, also increases with the duration of that transient, or the duration (or 

rise time) of the fast-rising source current. The knowledge that there are very large current transients with very 

short current rise times in lightning return strokes was relatively new to the community prior to the RTLP and 

was based primarily on recent remote measurements of the electromagnetic fields produced by strokes in 

natural lightning (e.g., Uman and Krider, 1982). As a result of the RTLP, however, the current derivatives and 

rise time in triggered subsequent return strokes were well known from direct measurements. Test standards 

given, for example, by Plumer (1992) fully reflected these observed peak current derivatives and current rise 

times.

5.4.3.2 Exposure of Hardware to Real Lightning Strikes

The kinds of hardware that have been tested by exposure to rocket-triggered lightning at the RTLP include 

protection systems for structures, radomes, power lines, and even nuclear devices. Here we list a few examples 

of such tests that were conducted at the RTLP. During 1985 Lawrence Livermore and Sandia National 

Laboratories tested a prototype protective canister for nuclear devices against rocket-triggered-lightning strikes 

(Melander et al., 1988)]. Rubinstein et al. (1991, 1994) describe measurements of induced voltages on an 

overhead power-distribution line by rocket-triggered discharges striking 20 m from one end of the line during 

1986. Testing of electric power equipment was conducted during 1987 and 1988 by Power Technology 

Incorporated for the Electric Power Research Institute. In 1990 Fisher and Schnetzer (1991) measured actual 

damage to metal samples that were directly exposed to rocket-triggered lightning, as a calibration for 

laboratory testing of burn-through.

5.4.3.3 Test and Calibration of Lightning-Detection Systems

There are three characteristics of lightning-detection systems that might be tested or calibrated against rockettriggered lightning at the RTLP. The most obvious is location accuracy, since the location of the triggered 

discharges is precisely known. The primary detection systems at the time (the National Lightning Detection 

System (e.g., Orville, 2008) -- called the NLDN -- and a medium-range version of it that was deployed around 

KSC (e.g., Krider, 1988) -- called the LLP system, later CGLSS) depended on radio direction finding (DF) and 

triangulation from multiple DFs to locate strikes. DFs are notorious for "site errors" -- errors in reported 

direction due to natural or man-made electromagnetic inhomogeneities of their surroundings. Statistical 

techniques have been developed for computing site-error corrections for DFs based on the self consistency of 

results from a multi-station network over many strikes distributed throughout its domain (e.g., Hiscox et al., 

1984), but there remains a need for ground-truth verification. Examples of such verification using flashes 

triggered by the RTLP include Maier and Jafferis (1985) and Maier (1991).

In addition to location accuracy, there are the two related questions of amplitude accuracy and detection 

efficiency. In general, it was shown by Willett et al. (1988, 1989a) that there is an approximately linear 

relationship between peak electric-field change (proportional to the peak magnetic-field change that is 

measured by DFs in the "far field") and the peak current, as predicted by the simple transmission-line model. 

Stroke magnitude (in terms of inferred peak current) has been calibrated against peak currents directly 

measured in the RTLP (Orville, 1991; Idone et al., 1993). To our knowledge, detection efficiency has never 

been checked relative to RTLP data.

5.4.3.4 Understanding of the Triggering Conditions

Arguably the most important impact of the RTLP on spaceflight operations has come from a better 

understanding of the triggering process and the triggering conditions. This is a large subject that will only be 

outlined here, but the key contributions provided by the RTLP will be highlighted.
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A basic understanding of the physics of air breakdown in long gaps had already been obtained from 

experiments on long laboratory sparks, especially during the 1970s (e.g., Les Renardières Group, 1977, 1981). 

Unfortunately, the longer the spark, the lower the marginal ambient field -- that is, the increase in applied 

potential per unit increase in gap length (for "critical" time to voltage crest and 50% breakdown probability) --

required to sustain its propagation. The longest sparks then available in the laboratory implied a marginal field 

of about 55 kV/m for gap lengths of 27 m (Pigini et al., 1979). This was generally believed to be much larger 

than the average fields in which lightning discharges could propagate. For example, Pierce (1971) had 

suggested that lightning could be triggered in ambient fields of several kilovolts per meter if the ambient 

potential spanned by the triggering conductor (building, rocket, aircraft, etc.) reached a few megavolts. There 

seemed to be a considerable gap between lightning and sparks that could be produced in the laboratory, hence 

there was a clear need for the rocket-triggering experiments.

Figure 5.4.3-1 shows a histogram of all the successful and unsuccessful trigging attempts versus the electric 

field measured at the ground over the eight-year lifetime of the RTLP (including 1983, when the program was 

begun at a site south of Melbourne, FL) (Jafferis, 1995). It is evident that foul-weather (negative) surface fields 

of 3 kV/m or greater over land provide a high probability of success. The fact that lightning was triggered in 

fields that were greater than 1 kV/m certainly justifies a 1 kV/m surface-field criterion in the current LLCC.

Under a thunderstorm, the ambient field a few hundred meters aloft is considerably larger than that at the 

surface under conditions like those when triggering was successful (e.g., Standler and Winn, 1979). This was 

demonstrated at the RTLP triggering site near the Mosquito Lagoon by Soula and Chauzy (1991), who used 

several electric-field sensors suspended by a captive balloon along an insulating tether at altitudes ranging 

from 80 to 800 m. Using the same instrumentation, Chauzy et al. (1991) and Soula and Chauzy (1991) showed 

that lightning could be triggered in fields aloft of 50 - 65 kV/m using grounded and ungrounded triggering 

wires of 200 - 300 m length. Since only four triggering attempts, all of which were successful, were made 

while the balloon sensors were operating, however, it must be assumed that triggering can occur in lower 

ambient fields. Indeed it was later shown that lightning could be triggered in ambient fields as low as 10 - 20 

kV/m (Willett et al., 1999).

In the foul-weather fields generally encountered at KSC, triggered discharges were initiated by positive 

"leaders" (highly ionized, conducting, filamentary channels extending into virgin air) propagating upward 

from the tips of the triggering rockets (Rakov and Uman, 2003, Section 7.2.1). Important new information 

about such leaders was obtained from the RTLP. With optical and near-ultraviolet (UV) observations Idone 

(1992) showed that between the rocket and cloud base, they propagate at speeds of up to almost 106 m/s. This 

propagation speed was often found to increase with altitude, sometimes abruptly in association with a marked 

decrease in channel tortuosity [Idone and Orville, 1988]. Even more interestingly, Idone [1992] showed that 

this positive-leader propagation is not smooth and steady, instead comprising a relatively regular sequence of 

optical "pulses" separated by roughly 20 μs of time and spanning several meters of height. The structure of 

individual pulses was revealed by the UV streak photographs to consist of "a bright, thin stem of typically 3-5 

m in length which is surrounded in the direction of propagation by a diffuse, hemispherical corona brush that 

extends outward about 5-10 m."
Page 63 of 234

Figure 5.4.3-1 Triggering success vs. surface field during the RTLP

Detailed electrical recordings were also made during the initiation and ascent of positive leaders in the RTLP 

(e.g., Laroche et al., 1989, Fig. 5). Much of this electrical phenomenology has been summarized in a review 

paper by Willett (1992). Synchronized records of channel-base current and close electric-field change show 

that brief current pulses with amplitudes of a few tens of Amperes and repetition intervals of several tens of 

microseconds are superimposed on a gradually increasing steady current of only a few Amperes. The current 

pulses coincide with steps in the electric field record, implying discrete pulses of charge deposition, 

presumably near the tip of the extending leader. Because of their similar time history, these electrical events 

are believed to correspond to the optical pulses mentioned above, although no synchronized optical and 

electrical records are available to date.

Positive-leader onset is typically preceded hundreds of milliseconds by a series of brief, irregularly spaced, 

current pulses, sometimes called "precursors," with amplitudes of a few Amperes and repetition intervals on 

the order of 30 ms (e.g., Barret, 1986). These precursors, in turn, have been shown by Laroche et al. (1988) to 
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consist of individual current and electric-field pulses like those in the leader onset itself, or groups of a few 

such pulses with similar repetition intervals, but no optical records of these events are available. This 

observation, however, has led to the hypothesis that the precursors are essentially attempted leaders that are 

unable sustain their propagation. If this hypothesis is correct, it implies that air breakdown, and even leader 

initiation, generally begin long before the rocket has ascended to sufficient altitude to produce self-sustaining 

leader propagation. This tentative conclusion points to leader "viability" (the ability to propagate indefinitely 

in the ambient field) as the most important criterion for lightning triggering by long, thin conductors.

In the "altitude-triggering" technique, the ascending rocket first unspools a predetermined length (typically a 

few hundred meters) of insulating line attached to the ground, followed by conducting wire for the remainder 

of its flight. (Sometimes an initial length of conducting wire, typically 50 m, is unspooled before the insulating 

section of line to "encourage" the triggered lightning to attach to ground-based measurement instrumentation.) 

This new technique, which was intended to better simulate triggering by a flying aircraft or spacecraft, was 

first exploited to advantage at the RTLP (e.g., Laroche et al., 1988, 1989, 1991). In a field of foul weather 

polarity it was found that the triggered discharge still begins with an upward-propagating positive leader from 

the tip of the rocket, apparently identical to those in classical triggering, followed a few milliseconds later by a 

downward-propagating negative leader from the lower end of the conducting wire. (To our knowledge this 

technique has yet to be successfully attempted in elevated fields of fair-weather polarity.)

Since the same sequence of events has been inferred to begin most strikes to instrumented aircraft (Boulay et 

al., 1988; Mazur, 1989), there is good reason to conclude that the positive-leader-viability conditions (as 

deduced from classical rocket-triggering experiments) are important in determining the triggering conditions to 

flying aircraft and spacecraft. In this way, results from the RTLP are still playing a vital role in the 

development of the LLCC.

5.4.3.5 Understanding of the Attachment Process

The term, "attachment process," refers to the details of the junction between a natural-lightning discharge and 

an object on the earth (e.g., Rakov and Uman, 2003, Section 4.5). For negative cloud-to-ground lightning this 

process comprises the initiation of an upward positive leader from the grounded object, its connection to the 

downward negative ("stepped") leader from the thundercloud that caused it, and the ultimate development of 

an upward-propagating return stroke. A better understanding of this process is obviously key to the lightning 

protection of grounded objects.

The attachment process can be simulated, albeit at relatively low intensity, by a variation on altitude triggering 

in which a short length of grounded, conducting wire is unspooled from the ascending rocket prior to the 

insulating segment. As described in Section 5.4.3.4 above, this leads to a downward, negative leader from the 

lower end of the triggering wire, which in turn causes the emission of a positive leader from the grounded 

segment. The first successful experiment of this type was conducted at the RTLP in 1989 (Laroche et al., 

1991).

The attachment process for negative, subsequent return strokes was also investigated during the RTLP by 

Idone (1990) and by Willett et al. (1989a), who showed optically and electrically that there are probably nonnegligible upward-connecting discharges that meet downward dart or dart-stepped leaders.

5.4.3.6 Constraints on Theoretical Models

The most important RTLP data for constraint of theoretical modeling have already been mentioned in Section 

5.4.3.4 above. Having concluded that the positive leader is the controlling phenomenon, we can also conclude 

that those leaders that initiate rocket-triggered discharges are significantly different from those studied to date 

in the laboratory. Thus there is a need for further theoretical and laboratory-experimental work to develop 

adequate models of these leaders. Such models could then be used (in concert with other, yet to be developed, 

models of the effects of rocket-exhaust plumes) for quantitative prediction of the ambient fields necessary for 
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spacecraft triggering of lightning. To date one detailed, self-consistent, physical model of the positive leader 

has been developed (Bondiou et al., 1994), and an unrelated, semi-empirical model of the triggering conditions 

has been proposed (Bazelyan and Raizer, 2000, Section 4.1.1). Nevertheless, the theoretical problem is far 

from solved, and more sophisticated rocket-triggering experiments will undoubtedly be needed to complete 

this process.

Thottappillil and Uman (1993) have demonstrated the value of RTLP measurements for testing of various 

return-stroke models. Other observations made as part of the RTLP that have already been, or will be, useful in 

lightning theory include direct measurements of the time evolution of return stroke (luminous) diameter by 

Idone (1992); the first wide-band measurements by Willett et al. (1989b) of the "narrow bipolar pulses" that 

had been discovered by Le Vine (1980); deductions about the behavior of return-stroke currents above ground 

by Willett et al. (2008); and the first fairly comprehensive measurements of close leader/return-stroke fields by 

Hubert and Hubert (1986) and by Rubinstein et al. (1992, 1995).

5.4.4 Stanford Research Institute (SRI)

In the late 1980s the Stanford Research Institute instrumented the Aeromet Inc. Learjet 36C with 8 field mills. 

Both calibration and research flights were flown from 12 August 1989 to 6 September 1989 to investigate 

electric fields of growing and towering cumulus clouds. The Learjet 36C has a ceiling of 45,000 ft (13.7 km), 

flight duration of ~ 5 hrs, a flight speed of 175 - 200 m s-1

, is certified for flight in known icing conditions, and 

lightning hardened. In addition to the field mills and instruments for determining aircraft position, attitude, and 

state parameters, the aircraft carried an array of microphysical instruments capable of determining particle 

concentration, size and types and liquid water content. The field mills are those described by Kositsky et al. 

(1991a). Calibration of the airborne field mill system was the scale-model charge-transfer technique of 

Kositsky et al., (1991) and Kositsky and Nanevicz (1991). A conductive scale-model of the aircraft was placed 

in a uniform electric field and the charge density was measured at the locations of the field mills. In-flight 

artificial charging of the aircraft and flight maneuvers in clear air were used to verify the scale model results.

Penetrations were made into cumulus and towering cumulus congestus clouds. Additionally passes were made 

outside cloud, but near the edge of clouds too large to penetrate. Flights into clouds containing ice or only 

water hydrometeors showed significant charging of the aircraft. All three components of the ambient electric

field appeared to be contaminated and proportional to those of the aircraft potential (Kositsky et al., 1991). 

However, field measurements outside of the cloud were found to be reliable. The results presented in Giori and 

Harris-Hobbs (1991) and Harris-Hobbs and Giori (1994) include only clear air measurements. Measurements 

from the WSR-74C radar at Patrick Air Force Base were used in the analysis to help determine cloud edge.

Results of maximum electric fields observed at cloud edge from the penetration of growing cumulus clouds at 

different stages of development are shown in Table 2 of Giori and Harris-Hobbs (1991) and reproduced below 

in Figure 5.4.4-1. B-1 refers to cumulus clouds with cloud top temperatures at or warmer than +5 o

C; B-2 to 

cloud top temperatures at or warmer than -10 o

C; B-2 to cloud top temperatures at or warmer than -20 oC; and 

B-4 to cumulonimbus or thunderstorm clouds. The results show that the cumulus clouds they studied did not 

develop significant electric fields until cloud top temperatures were colder than -10 o

C.

Other findings reported in Giori and Harris-Hobbs (1991) and Harris-Hobbs and Giori (1994) are:

1. For seven clouds (41 penetrations; 21 passes near cloud edge) they examined the relationship between 

the maximum field strength at cloud edge (Emax) and the distance from the cloud at which the field 

drops to slightly above fair weather fields. In all categories from B-1 through B-4, they found that the 

standoff distances in the LLCC were much larger than the distances from cloud edge for the fields to 

drop to fair weather values.

2. A study of the cloud volume containing radar reflectivity >30 dBZ above 0o

C showed a correlation 

with Emax at cloud boundary.
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3. They suggested that radar measured parameters might prove useful in determining safe standoff 

distances.

4. Anvil debris clouds studied seemed to become rather weakly electrified after they detached from the 

parent storm.

5. Three passes in a layered cloud (debris cloud in current terminology), showed that the electric field 

remained strong for at least 30 min.

Figure 5.4.4-1 Table 2 reproduced from Gori and Harris-Hobbs (1991)

5.4.5 New Mexico Institute of Mining and Technology Studies

The New Mexico Institute of Mining and Technology/Office of Naval Research Special Purpose Test Vehicle 

for Atmospheric Research (SPTVAR) aircraft was flown from 14 Sept. to 4 Nov. 1988 and again from 21 July 

to 1 Sept. 1989. The SPTVAR is a modified Schweizer 845 aircraft airframe powered by a 150 kW Lycoming 

engine with capability of flying through clouds up to 30,000 ft (9 km). It has a flight endurance of 3 to 3.5 

hours and flies at 50 m s-1

. For the studies near Kennedy Space Center it was instrumented with 5 rotatingvane electric field mills of the type described by Winn (1993). It had the capability of measuring all three 

components of the electric field and the potential due to charge on the aircraft. Additionally, the aircraft was 

instrumented to measure ambient temperature, cloud liquid water content, pressure, air speed and aircraft 

position (VOR/DME and Loran C). Gyroscopes provided measurements of heading, roll and pitch. Some 

measurements were telemetered to the ground. The capability of displaying electric fields at the ground during 

flight was developed.

The SPTVAR was directed to a cloud system to determine if fields were present and to explore the intensity, 

duration and extent of that field when it appeared that a cloud system would preclude launch of a space vehicle 

because of a potential electrical hazard, For cumulus clouds with tops below the freezing level, repeated 

penetrations were made midway between cloud base and cloud top. For taller clouds repeated penetrations 

were made near the 0o

C level through the thickest part the cloud. This flight level was flown to minimize icing 

but also to be near the larger fields within the cloud. Most of the flights were into cumulus clouds but some 

flights were also made into debris clouds and adjacent to cumulonimbus clouds too large to penetrate. A few 

layer clouds and disturbed weather clouds were also investigated.

The main goals of the project were: 1) Develop and demonstrate techniques for measuring electric field aloft 

and locating regions of charge during flight. 2) Characterize the conditions within and near clouds at KSC that 
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are presently identified as a threat to space launch vehicles. 3) Study the correlation between the electric fields 

aloft and those from the KSC ground-based field mill network for a variety of electrified clouds.

The studies conducted by SPTVAR are documented in 3 reports. Part I (Jones et al., April 27, 1990) describes 

the aircraft and instrumentation; project goals; flight plans for studying cloud over KSC; summary of 

operations flights for 1988; conclusions and recommendations. It also contains appendices on field mill 

calibration; determination of the vector field, a track plotting program “SPT” and individual flight summaries 

for 1988. Part II (Jones et al., April 27, 1990) presents a case study of the 4 Nov 1988 flight in which the 

SPTVAR found fields aloft less than 1.6 kV/m while the KSC field mill network showed fields >3 kV/m at the 

surface. Part III (Jones et al., Aug 21, 1990) describes flights made during the summer 1989 deployment and 

the overall findings and conclusions based on all data gathered.

General finding from these studies are:

1. An aircraft instrumented to measure the electric field vector can be an effective method for assessing 

electrical conditions within selected clouds over KSC.

2. For cumulus clouds with temperatures everywhere warmer than 0 o

C, no significant electrification was 

encountered. Three marginally electrified clouds had 5 dBZ tops to about the -20 o

C level. It appeared 

that dynamic growth above the -20 o

C level was necessary for the clouds to become significantly 

electrified.

3. The contour plots of the surface electric field gave misleading representations of charge locations 

outside of the network due to unjustified closing of the field contours near the edge of the network.

4. On one occasion with a widespread cloud layer, the electric field disturbances coincided with cells of 

embedded convection.

5. Screening layers on the sides of clouds, if they existed, were insufficient to mask the presence of 

charge within the clouds.

6. Usually the electric field aloft is much stronger than at the ground, but one exception was documented 

in Part II.

5.5 Lightning LCC

5.5.1 The LAP Process

The success that the LAP has had in reviewing and improving the LLCC and the associated Definitions is 

based primarily on three factors: Expertise, experience, and collaboration.

Expertise and Scientific Experience. The constitution and evolution of the LAP (formerly the PRC) has been 

described in Section 5.2.1. The expertise and experience of the individual LAP members are briefly 

summarized in Appendix III. Collectively, their experience with lightning science and lightning’s effects on 

space vehicles spans the entire period from the Apollo XII lightning strike in 1969 to the present. Their 

scientific expertise encompasses not only lightning physics and measurement, but cloud physics and 

measurement, statistics and advanced mathematics, and other aspects of atmospheric physics and even 

astrophysics. The current LAP members represent a broad cross section of the relevant knowledge, scientific 

experience, and institutional perspectives. Therefore, the LAP is uniquely qualified to advise NASA and the 

Air Force on matters relating to the LLCC.

LAP Experience Promotes Collaboration. The initial role of the PRC was fairly narrow -- essentially to review 

some proposed changes to the LLCC generated by MSFC personnel after the ABFM I campaigns (see Section 

5.4.1). Over the past two decades, however, a dual purpose has evolved. On the one hand, the LAP has rewritten sections of the LLCC in response to new scientific knowledge and instrument capabilities (e.g., new 

understanding of the electrical environment that can trigger lightning), and it has also proposed new 

experiments to advance that knowledge in areas that are important for the LLCC (e.g., the ABFM II 
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experiment and the use of radar to evaluate anvil and debris clouds -- see Section 6.4). On the other hand, the 

operational launch-weather community (particularly the KSC Weather Office and the 45WS, but also the 

SMG, the 30WS at Vandenberg AFB, and even meteorologists at the KLC) have brought questions and 

concerns to the LAP for various reasons. The dialog between the LAP and the launch-weather community has 

become a close collaboration on important tasks, such as clarifying the text of the rules, and has increased both 

launch availability and safety.

Rather than risk future lightning incidents, the LAP has always chosen to start with general rules that are 

known to be conservative, and it has recommended additional instrumentation (e.g., field mills) to cover 

unexpected conditions that may be hazardous. Close collaboration between the LAP, the 45WS, and the KSC 

Weather Office has proved to be an efficient way to identify individual launch restrictions that have a 

significant impact on launch availability or that may have an unduly high false-alarm rate. Attention has then 

focused on these situations, with the operational community gathering relevant data for the LAP to review, and 

solutions have been found that increase launch availability without compromising safety. By identifying the 

sources of false alarms, and by recommending new ways of detecting and eliminating them, the LAP has been 

able to incrementally reduce the initial conservatism of the general rules and to safely increase launch 

availability. For example, the LPLWS has thus been converted from a launch-availability negative into a 

means of relaxing certain rules through exceptions (e.g., the current field-mill exception to the long-duration, 3 

NM standoff requirements in the absence of VAHIRR by both the Detached-Anvil and the Debris-Cloud 

Rules).

Unfortunately increased launch availability (without compromising safety) comes at the price of greater 

complexity in the language of the LLCC because of the addition of numerous exceptions, and many of these 

exceptions require specialized measurements and analysis to verify them. Here again, the close working 

relationship that has developed between the LAP and the 45WS has been an invaluable tool for clarifying the 

meaning of the LLCC and has led to more efficient application of them during launch operations.

The Future of Collaboration. Logical truth-tables (for examples, see the figures in Appendix II) were 

originally introduced by Dr. Harry Koons as a technique for identifying and eliminating any inconsistencies 

between different sections of a given complex rule. Recently the LAP has been using truth tables not only to 

eliminate contradictions, but also to remove redundancies between sections of such a rule. Any inconsistency 

or redundancy can lead to ambiguity, which makes the rules more difficult to understand and apply. The truth 

tables can also make the structure of the more complex rules easier to grasp. The LAP is currently exploring 

whether graphical truth-tables might be beneficial as training materials for launch weather personnel.

5.5.2 LLCC Revisions – 1991

As mentioned in Section 5.0.3, Heritage (1988) published a set recommended LLCC together with a detailed 

scientific rationale (their Chapter 7, further justified by their Chapters 1 - 3). These recommendations are 

quoted in Appendix I, Section A1.8. After considerable discussion among the interested parties, a new set of 

launch rules that was uniform across the Shuttle and ELVs was finally agreed upon. The first operational postAC 67 rules are well represented by the "Space Shuttle LLCC (1991)" discussed in this section.

In each of the following sections, major changes from the preceding set of rules are mentioned (for a more 

complete discussion of the differences, see the corresponding entry in Appendix II), and only rules that are 

significantly changed are given in paraphrase to save space and reduce complexity, as was done with the 

current rules in Section 1.1. Note that these paraphrases are invariably given in italics to distinguish them from 

the actual LLCC, which are quoted verbatim in the corresponding sections of Appendix I. 

Space Shuttle LLCC (1991) [LCN 00048, 01/28/91]. These rules may be found in Appendix I, Section A1.9.1. 

Many of them were similar or identical to the recommendations of Heritage Committee. The primary 

difference was that these LLCC include no provision for the use of electric fields measured aloft by one or 
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more ABFMs, as had been done briefly during the Apollo-Soyuz and Viking missions (see Sections 3.3.3 and 

3.3.4) and was also recommended by the National Research Council (1988) and the PRC (see Section 5.2.1). 

The "Triboelectrification Rule" recommended by the Heritage Committee was also omitted here, presumably 

because these rules were for Shuttle only, and the Shuttle had been hardened against triboelectrification. The 

1991 Shuttle LLCC are simple enough to quote in full here as a starting point for the following sub-sections:

Even when constraints are not violated, if any other hazardous conditions exist, the Launch Weather Officer 

will report the threat to the Launch Director. The Launch Director may HOLD at any time based on the 

instability of the weather.

The Launch Weather Officer must have clear and convincing evidence the following constraints are not 

violated.

A. Do not launch if any type of lightning is detected within 10 nautical miles of the launch site or planned 

flight path within 30 minutes prior to launch, unless the meteorological condition that produced the 

lightning has moved more than 10 nautical miles away from the launch site or planned flight path.

B. Do not launch if the planned flight path will carry the vehicle:

1. Through cumulus clouds with tops higher than the 5 °C level; or

2. Through or within 5 nautical miles of cumulus clouds with tops higher than the -10 °C level; or

3. Through or within 10 nautical miles of cumulus clouds with tops higher than the -20 °C level; or

4. Through or within 10 nautical miles of the nearest edge of any cumulonimbus or thunderstorm 

cloud including its associated anvil.

C. Do not launch if, for Ranges equipped with a surface electric field mill network, at any time during the 

15 minutes prior to launch time the one minute average of absolute electric field intensity at the 

ground exceeds 1 kilovolt per meter (1kV/m) within 5 nautical miles of the launch site unless:

1. There are no clouds within 10 nautical miles of the launch site; and

2. Smoke or ground fog is clearly causing abnormal readings.

NOTE: For confirmed instrumentation failure, continue countdown.

D. Do not launch if the planned flight path is through a vertically continuous layer of clouds with an 

overall depth of 4,500 feet or greater where any part of the clouds are located between the 0 °C and the 

-20 °C temperature levels.

E. Do not launch if the planned flight path is through any cloud types that extend to altitudes at or above 

the 0 °C temperature level and that are associated with disturbed weather within 5 nautical miles of the 

flight path.

F. Do not launch through thunderstorm debris clouds, or within 5 nautical miles of thunderstorm debris 

clouds not monitored by a field mill network or producing radar returns greater than or equal to 10 

dBz.

G. Definitions

1. Debris Cloud: Any cloud layer, other than a thin fibrous layer, that has become detached from the 

parent cumulonimbus within 3 hours before launch.

2. Disturbed Weather: Any meteorological phenomenon that is producing moderate or greater 

precipitation.

3. Cumulonimbus Cloud: Any convective cloud which exceeds the -20 °C temperature level.

4. Cloud Layer: Any cloud broken or overcast layer or layers connected by cloud elements, e.g. 

turrets from one cloud layer to another.

5. Planned Flight Path: The trajectory of the flight vehicle from the launch pad through its flight 

profile until it reaches the altitude of 100,000 feet. The flight path may vary plus or minus 0.5 

nautical miles horizontally up to an altitude of 25,000 feet.

6. Anvil: Stratiform or fibrous cloud produced by the upper level outflow from thunderstorms or 

convective clouds. Anvil debris does not meet the definition if it is optically transparent.
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5.5.3 LLCC Revisions – 1992

Space Shuttle LLCC (1992) [LCN 00230R04, 03/20/92]. These rules may be found in Appendix I, Section 

A1.9.2. They are nearly identical to the above except for relatively minor changes to the Field-Mill Rule (C), 

which may be paraphrased as follows:

Surface Electric Fields. Do not launch if the electric field within 5 nm of the launch site has exceeded ±1 kV/m 

in the past 15 minutes. Exceptions are allowed if (1) all clouds within 10 nm of the launch site have not been 

associated with convective clouds with tops colder than -10 °C for at least 3 hours and are (a) thin fibrous 

(optically transparent) clouds or (b) less than 2/8 coverage with tops warmer than +5 °C, and if (2) smoke, 

ground fog, or a maritime inversion with fields between +1000 and +1500 V/m is clearly causing the elevated 

readings.

5.5.4 LLCC Revisions – 1995

Space Shuttle LLCC (1995) [LCN 00520R03, 04/25/95] (see Appendix I, Section A1.9.4). This major rule

change was based a new set of LLCC recommended the year before by the PRC (see Appendix I, Section 

1.9.3) and had more to do with reorganization and clarification than with substantive changes. Nevertheless, 

the following significant differences between the PRC's recommendations and the published rules drew a 

formal "letter of concern" from the PRC: 1) "Rationales" had been added to all of the rules without PRC 

knowledge or review. 2) The PRC-recommended Triboelectrification Rule had been dropped (only for Shuttle, 

it appears.) 3) An Electric-Fields-Aloft Rule granting exceptions to the Thick-Cloud, Disturbed-Weather, and 

Debris-Cloud Rules (the PRC's version of the Heritage Committee's recommendation) had also been dropped.

Substantive changes from the previous operational version of the LLCC included insertion of the word, 

"transparent," to limit the application of some LLCC, some relaxation of the Cumulus Clouds Rule, more 

explicit treatment of Anvil Clouds, and application of the Surface Electric Fields Rule all along the flight path. 

The PRC-recommended Electric-Fields-Aloft Rule is also paraphrased below, although it was never part of the 

Shuttle rules:

Cumulus Clouds. Do not fly within 10 nm of any cumulonimbus or thunderstorm cloud, including 

nontransparent parts of its attached anvil, nor within 10 nm of a nontransparent detached anvil for the first 

hour after detachment, nor within 5 nm of any cumulus cloud with a top colder that -10 °C. Do not fly through 

any cumulus cloud with its top colder +5 °C. An exception is allowed for a cumulus cloud with its top between 

±5 °C if that cloud is not producing precipitation and if a field mill within 3 nm (or the altitude of the -5 °C 

level, if smaller than 3 nm) of the farthest edge of that top, and any other mills within 5 nm of the flight path, 

have shown greater than −100 V/m, but less than +1000 V/m, for at least 15 minutes.

Surface Electric Fields. Do not fly within 5 nm of any electric field mill that has shown readings in excess of 

±1 kV/m in the past 15 minutes. Exceptions are allowed if (1) all clouds within 10 nm of the flight path are (a) 

transparent or (b) have tops warmer than +5 °C and have not been associated with convective clouds with 

tops colder than -10 °C for at least 3 hours and if (2) a known benign source near the mill is clearly causing 

the elevated readings.

Electric Fields Aloft. The "Thick Cloud Layers," "Disturbed Weather," and "Debris Clouds" rules need not be 

applied if, during the 15 min prior to launch time, the absolute value of the instantaneous vector electric field 

sampled within the cloud volume expected to be along the flight path is less than a designated function of 

altitude.

5.5.5 LLCC Revisions – 1998

Space Shuttle LLCC (1998) [LCN 00824R03, 06/04/98]. This major change was adopted by the LAP on 

5/20/1998, was documented by Krider et al. (1999), and is quoted in Appendix I, Section A1.9.5. It included a 

complete re-write of the rules to clarify and improve their logic. All Rationales were eliminated. Although all 
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of the rules were re-ordered and changed enough to deserve paraphrases below, key changes were the removal 

of anvil clouds from the Cumulus Cloud Rule into a separate Anvil Clouds Rule and the addition of new 

Smoke Plume Rule. In the process, several of the rules were somewhat relaxed.

Lightning. Do not fly within 10 nm of any type of lightning, or any convective cloud that has produced it, 

within the past 30 min. An exception is allowed if the cloud has moved beyond 10 nm and if an electric field 

mill within 5 nm of the lightning, and any other mills within 5 nm of the flight path, have shown less than 

±1000 V/m for at least 15 minutes.

Cumulus Clouds. Do not fly within 10 nm of any cumulus cloud with a top colder than -20 °C, nor within 5 nm 

of any cumulus cloud with a top colder that -10 °C. Do not fly through any cumulus cloud with its top colder

+5 °C. An exception is allowed for a cumulus cloud with its top between ±5 °C if that cloud is not producing 

precipitation and if a field mill within 2 nm of that top, and any other mills within 5 nm of the flight path, have 

shown greater than −100 V/m, but less than +500 V/m, for at least 15 minutes.

Anvil Clouds:

Attached Anvil Clouds. Do not fly within 10 nm of any non-transparent, attached anvil for at least 30 minutes 

after the last lightning discharge occurs in the parent cloud or anvil, nor within 5 nm for 3 hours after the last 

lightning. Never fly through such a cloud.

Detached Anvil Clouds. Do not fly within 10 nm of a non-transparent, detached anvil for 30 minutes after the 

last lightning discharge occurs in the detached anvil (or in its parent cloud before detachment), nor within 5 

nm for 3 hours after the last such lightning. Do not penetrate such an anvil for 3 hours after detachment, nor

for 4 hours after it has produced lightning. Exception: Flight is allowed up to the edge of a detached anvil 

between 30 minutes and 3 hours after the last lightning if the radar reflectivity of all parts of that cloud within 

5 nm of the flight path has been less than 10 dBZ, and if a field mill within 5 nm of the cloud (and any other 

mills within 5 nm of the flight path) have shown less than ±1000 V/m, for at least 15 minutes.

Debris Clouds. Do not fly within 5 nm of a non-transparent debris cloud for 3 hours after it detaches or decays 

from its parent cloud and for 3 hours after it has produced lightning. Exception: Flight is allowed up to the 

edge of a debris cloud at any time if the radar reflectivity of any part of that cloud within 5 nm of the flight 

path has been less than 10 dBZ, and if a field mill within 5 nm of the cloud (and any other mills within 5 nm of 

the flight path) have shown less than ±1000 V/m, for at least 15 minutes.

Disturbed Weather. Do not fly through any non-transparent cloud associated with disturbed weather that has 

cloud tops colder than 0 °C and that, within 5 nm of the flight path, either contains moderate or greater 

precipitation or shows evidence of melting precipitation.

Thick Cloud Layers. Do not fly through a non-transparent cloud layer that is thicker than 4500 feet and 

contains temperatures between 0 °C and -20 °C, nor through any non-transparent cloud layer that is 

connected to such a thick cloud layer within 5 nm of the flight path. An exception is allowed if the thick cloud 

layer is cirriform, is entirely colder than -15 °C, contains no liquid water and has never been associated with 

a convective cloud.

Smoke Plumes. Do not fly through any cumulus cloud that develops from a smoke plume for 60 minutes after it 

has detached from that plume.

Surface Electric Fields. Do not fly within 5 nm of any electric field mill that has shown readings in excess of 

±1 kV/m in the past 15 minutes. The field threshold can be raised to ±1.5 kV/m if all clouds within 10 nm of the 

flight path are transparent or if they (a) have tops warmer than +5 °C and (b) have not been part of convective 

clouds with tops colder than -10 °C for at least 3 hours.
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5.5.6 Proposed Field Mill Aloft Rule

As we have seen in Section 3.3, fields aloft were used briefly during the ASTP/Viking era as a means of 

relaxing several of the contemporary cloud-related rules. Based on his report on ASTP, Arabian [1976] clearly 

believed that a successful operations plan involving several ABFM platforms had been worked out that would 

allow the successful use of such an exception.

After the AC-67 disaster, the Hosler Committee [National Research Council, 1988] revived this idea, 

recommending "implementation of the following actions as rapidly as possible: instrumenting an aircraft to 

measure electric fields aloft [and other parameters] along the launch/landing paths..." The Heritage Committee 

[Heritage, 1988] went further in their 1988 review of the A/C-67 disaster by proposing specific exceptions of 

the following form for several of their proposed, cloud-related rules:

A. The electric field intensity at the ground (for ranges that have a ground field mill system) has remained 

below 1 kV/m within 5 nmi of the launch pad [There are no clouds within 10 nmi of the launch pad at 

the planned time of launch]; and

B. The absolute value of the instantaneous critical electric field intensity [within the clouds] sampled 

along the flight path [during the 15 minutes prior to launch] is less than the critical value, Ec, shown as 

a function of altitude in Figure 7-1.

(The referenced figure gave an altitude profile of Ec that decreased from 5 kV/m at the surface through 1 kV/m 

at about 45,000 ft in proportion to atmospheric pressure.)

A similar exception was advocated by the PRC in their first formal LLCC report [Koons and Walterscheid, 

1996], and was continued by the LAP in their second LLCC report [Krider et al., 1999]. It was dropped from 

their proposed LLCC sometime between 1998 and 2003, after Hugh Christian joined the LAP in February 

1999 and had begun making a strong case against it. Dr. Christian argued successfully (1) that there was no 

scientific consensus on the critical field profile that had been proposed by the Heritage Committee (although 

such a consensus may have evolved over the last few years -- see the Rational Document) and (2) that, 

contrary to Mr. Arabian's earlier position, no viable operations plan had been developed for use of an ABFM 

in support of launches. The latter was a position that had been espoused by the weather-support community all 

along and which was the reason that such an ABFM exception had never been implemented in the operational 

LLCC.
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Chapter 6 ABFM II and Beyond (2000 – 2010)

6.0 Background

On 1 Dec 1999, the LAP recommended that NASA sponsor a second airborne field mill program (ABFM II) 

to "validate physics-based relationships between the decay of cloud electric fields and cloud properties and to 

verify that these cloud properties, and also the presence of electric generators aloft, can be inferred from 

ground-based measurements."

Initial ABFM II funding for limited planning, instrumentation development and testing was obtained from the 

Shuttle Launch Integration Manager, Don McMonagle, in mid-1999. Funding for the field programs in 2000 

and 2001 was obtained from a variety of sources but the largest contributor by far was the Shuttle program. 

The total cost of ABFM II by the time data analysis was largely completed in 2005 was about $3M. Details of 

the program are provided in section 6.4 of this chapter. Application of the data to LLCC development and 

some limited additional analysis continued through 2009.

The ABFM II field program and subsequent extensive efforts to properly calibrate and synchronize the 

multiple in-situ and remote sensing data it produced resulted in the largest, most comprehensive and reliable 

data set of its kind ever collected. The size and quality of the data set provided the LAP sufficient information 

to recommend major revisions to the LLCC in 2005 and again in 2008. The data set is accessible to the public 

for further research at <http://abfm.ksc.nasa.gov/>.

6.1 Infrastructure

Except as noted below in this section, the weather infrastructure at KSC/CCAFS remained the same as that 

presented in Section 5.1 during the period covered by this chapter.

During the first decade of the 21st century, the consolidation of KSC and CCAFS weather infrastructure under 

the management of the Eastern Range continued. The NASA-developed Lightning Detection and Ranging 

(LDAR) system had proven its value, but it was aging and needed replacement. A commercial version of 

LDAR had been developed by Global Atmospherics, Inc. (subsequently acquired by Vaisala, Inc.) under a 

Space Act Agreement with KSC. The 45th Space Wing purchased the commercial version of LDAR from 

Vaisala. The new system, called LDAR II, is now the operational system and the KSC LDAR was 

decommissioned in November 2008.

As this is being written, a new, 5 cm, Doppler, dual-polarization weather radar is undergoing acceptance 

testing at the Eastern Range. The new radar is scheduled to replace the antique WSR-74C as soon as it is 

accepted by the Range, currently expected by late summer 2010.

During this same period, Vandenberg Air Force Base saw significant changes in range weather equipment. 

The Range Standardization and Automation system, now known as the Western Range Weather System 

(WRWS), and Space Launch Range System Contract range systems upgrade projects affected just about every 

aspect of how the Western Range conducts business. There were changes to equipment, communications, 

procedures and instructions that govern weather for launch and flight operations. The 30th Space Wing 

operationally accepted the WRWS in June 2008.

6.2 Organization

There were no significant changes in the organization of weather support for America’s space program during 

the period presented in this chapter.
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6.3 Operations

On 1 February 2003, the Space Shuttle Columbia disintegrated during its reentry into the atmosphere while 

attempting to land at KSC. All seven crew members died. Although this accident did not involve lightning or 

the LLCC, a brief description is provided here because some of the lessons learned have affected the processes 

and procedures used by NASA and the Air Force in assessing issues (like the LLCC) that may affect flight 

safety. The material in this section is based on the Columbia Accident Investigation Board Report (Columbia 

Accident Investigation Board, 2003, hereafter CAIB).

The final mission of Space Shuttle Columbia, designated as STS-107, was launched from complex 39A on 16 

January 2003 for an intensive science mission. At 81.7 seconds after launch, when the Shuttle was at about 

65,820 feet and traveling at Mach 2.46 (1,650 mph), a large piece of hand-crafted insulating foam came off an 

area where the Orbiter attaches to the External Tank. At 81.9 seconds, it struck the leading edge of Columbia’s 

left wing. This event was not detected by the crew on board or seen by ground support teams until the next 

day, during detailed reviews of all launch camera photography and videos. This foam strike had no apparent 

effect on the daily conduct of the 16-day mission, which met all its objectives. (CAIB, p11.)

On 1 February, with an extremely successful mission behind them, the STS-107 crew prepared for their return 

to a planned morning landing at KSC. The de-orbit burn to slow Columbia down for re-entry into Earth’s 

atmosphere was normal, and the flight profile throughout re-entry was standard. Time during entry is 

determined from “entry interface”, an altitude of 400,000 feet where the Orbiter begins to experience the 

effects of Earth’s atmosphere. Entry Interface for STS-107 occurred at 8:44:09 a.m. on February 1. Unknown 

to the crew or ground personnel, because the data is recorded and stored in the Orbiter instead of being 

transmitted to Mission Control at Johnson Space Center, the first abnormal indication occurred 270 seconds 

after Entry Interface. (CAIB, p.12). By the time Columbia passed over the coast of California in the pre-dawn 

hours of February 1, at Entry Interface plus 555 seconds, amateur videos show that pieces of the Orbiter were 

shedding. Analysis indicated that the Orbiter continued to fly its pre-planned flight profile, although, still 

unknown to anyone on the ground or aboard Columbia, her control systems were working furiously to 

maintain that flight profile. Finally, over Texas, just southwest of Dallas-Fort Worth, the increasing 

aerodynamic forces the Orbiter experienced in the denser levels of the atmosphere overwhelmed the 

catastrophically damaged left wing, causing the Orbiter to fall out of control at speeds in excess of 10,000 mph 

(ibid).

The Board concluded that “Columbia re-entered Earth’s atmosphere with a pre-existing breach in the leading 

edge of its left wing in the vicinity of Reinforced Carbon-Carbon (RCC) panel 8. This breach, caused by the 

foam strike on ascent, was of sufficient size to allow superheated air (probably exceeding 5,000 degrees 

Fahrenheit) to penetrate the cavity behind the RCC panel. The breach widened, destroying the insulation 

protecting the wing’s leading edge support structure, and the superheated air eventually melted the thin 

aluminum wing spar. Once in the interior, the superheated air began to destroy the left wing.” (ibid).

The Board identified a number of specific causes of the accident, including schedule pressure (CAIB, section 

6.2) and management’s failure to realize the danger and address it (CAIB, section 6.3). Of more direct 

relevance to this History and its potential value, the Board found the general cause of the accident was a 

“broken safety culture (CAIB, section 7.4). An entire chapter (CAIB, chapter 8) was entitled “History as a 

Cause”. The applicable lesson is that attitudes, processes and procedures matter as much as technology. That is 

a lesson fully applicable to the LLCC.
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6.4 ABFM II Research

This section describes ABFM II in detail.

6.4.1 Overview

The ABFM II project was lead jointly by NCAR and MSFC and had other participants from the Univ. of 

Arizona, NASA KSC, NOAA, the Univ. of North Dakota and other organizations. The University of North 

Dakota Citation 2 aircraft was deployed from 2 June 2000 through 29 June 2000 and from 22 May 2001 

through 29 June 2001. It was also deployed during the first half of February 2001 to investigate thick clouds 

and long anvils originating from the Gulf of Mexico, but because of severe drought in central Florida the 

deployment was terminated early. The UND Citation 2 is a twin-engine fanjet with an operational ceiling up to 

43,000 ft (13 km), an endurance of 4 1/2 hours, normal flight speeds of 100 to 120 m sec-1

, and certification for 

known icing conditions.

6.4.2 Experimental Design

The main general goal of the project was to obtain measurements within anvils, debris clouds and other cloud 

systems to identify possible relationships between electric field, particle concentration, size and types, and the 

radar reflectivity and structure of the clouds. A specific goal was to try to determine the decay rate of electric 

field in anvils near KSC to see if the observed decay rates were consistent with decay rates theoretically 

predicted in a simple model developed by John Willett for this project.

Initial penetrations into the anvils were normally made near the core of the storm. Then subsequent, repeated 

passes were made at different distances downstream or at different altitudes. When Air Traffic Control would 

permit (which was not very often) spiral descents/ascents were made to obtain vertical profiles of the anvil or 

sometimes in debris or trailing stratiform clouds. Vertical sampling in individual anvils was often incomplete 

but over the period of the two summer campaigns penetrations were made over a variety of altitudes at 

different locations relative to the anvil top and bottom.

The flights were coordinated with the WSR-74C 5 cm radar at Patrick Air Force Base and WSR-88D 10 cm 

NEXRAD radar at Melbourne Florida. ABFM scientists in the Range Operations Control Center viewing radar 

cross-sections helped to direct the aircraft. Both cloud-to-ground (CG) and intra-cloud (IC) lightning were 

detected and recorded using the KSC Cloud to Ground Lightning Surveillance System (CGLSS) and the 

Lightning Detection and Ranging System (LDAR), as well as the ground-based field mill network.

6.4.3 Instrumentation

The UND Citation was instrumented with 6 rotating-vane field mills described by Bateman et al. (2007) (See 

Figure 6.4.3-1). The calibration of the field mill system is described in Mach and Koshak (2007).
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Figure 6.4.3-1 A field mill on the side of the Citation fuselage

Note: Conductive paint surrounds the Mill. The Cloud Particle Imager appears below it.

The Citation had an extensive array of microphysical probes and sensors including the Particle Measuring 

Systems (PMS) FSSP, 1-DC, and 2-DC, and the Stratton Park Engineering Company (SPEC) Cloud Imaging 

Probe (CPI) and High Volume Particle System (HVPS). Thus particles from a few microns to more than 10 

mm in size could be counted, sized and imaged. Additionally there was a King liquid water probe and a 

Rosemount Icing detector for measuring and detecting the presence of supercooled liquid water (See Figure 

6.4.3-2). The aircraft, instrumentation, radars, and lightning detection systems are described in the Appendices 

of Dye et al. (2003).
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Figure 6.4.3-2 The UND Citation Wing-mounted cloud physics sensors

Note: From left to right, the High Volume Particle Sampler, King liquid water sensor, the Rosemount 

temperature sensor and the Forward Scattering Spectrometer Probe.

6.4.4 The 2000 field campaign

In 2000, all of the research flights took place in June. There were twelve days on which research flights were 

conducted, and on three of those days there was sufficient time for two flights, providing a total of fifteen 

research flights for the deployment. In addition, calibration flights over the Shuttle landing facility (See Figure 

6.4.4-1) and over the ocean were conducted as needed.

Initial penetrations were often made near to, but at a safe distance from, the convective cores of storms. Then 

subsequent passes were made in the anvil at different distances downstream to examine the decay of the 

electric field with both time and distance. When Air Traffic Control (ATC) would allow, spiral ascents or 

descents were made through the anvils, but these were not nearly as frequent as was desirable for studying the 

anvil vertical structure. As a result, sampling of the vertical structure of the anvil of individual storms was 

often incomplete.
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Figure 6.4.4-1 UND Citation calibration flight at the SLF

Note: A field mill from the KSC/CCAFS network appears on a tripod at the lower right and the U. Arizona 

mobile field mill appears at the lower left.

The Citation was flown with 2 pilots and three scientific observers: a flight scientist, a scientist to operate and 

monitor the UND data system and microphysical instruments, and a scientist or engineer to operate and 

monitor the field mill measurements. Decisions on where to fly were interactive between crew in the aircraft 

and aircraft coordinators at the KSC Range Operations Control Center (ROCC).

There were normally 2 or more ABFM team members on the ground in the ROCC. Aircraft position was 

telemetered to the ROCC and overlaid on the WSR-74C near real-time vertical and horizontal displays 

generated using Sigmet software. In the ROCC one ABFM team member communicated with the aircraft for 

both safety and scientific purposes while one person operated the 74C radar display system to produce desired 

cross sections. Often there was an additional person in the ROCC to guide the University of Arizona mobile 

field mill vehicle to the near vicinity of storms of interest and especially those being investigated by the 

Citation. Unfortunately, storms were often too distant from KSC for the mobile field mill to be deployed 

directly to storms studied by the aircraft.

6.4.5 The 2001 Field campaign

There were actually two field campaigns in 2001, a winter campaign in February and a summer campaign in 

May and June. With the hope of improving the “Thick Cloud Rule”, the month of February was selected for a 

program targeted at thick layered clouds because they are climatologically most likely to occur in central 
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Florida in the late winter. In addition to the instrumented ABFM II aircraft described above, a ground-based 35 

GHz scanning Doppler, dual-polarized cloud radar (Martner et al, 2002) was provided by NOAA’s 

Environmental Technology Laboratory. Unfortunately, during the entire three week February deployment, no 

clouds of the type covered by the Thick Cloud Rule occurred over central Florida.

The summer program ran from 20 May to 30 June 2001 with the primary objective being to increase the 

sample sizes in anvil and debris clouds using similar strategies as those used in 2000. Based on lessons learned 

in 2000, some adjustments were made in the coordination with the FAA Miami and Jacksonville Air Route 

Control Centers in an attempt to generate more opportunities for vertical profiles, but those opportunities 

remained rare. The weather cooperated for the summer program and research flights took place on eighteen 

days.

Over the period of the two summer campaigns anvils were sampled at a wide variety of altitudes in different 

locations relative to anvil top and bottom. Thus, the observations in aggregate are felt to be representative of 

conditions in anvils of Florida thunderstorms. On some occasions, stair step horizontal passes were made 

through the anvil or at other times passes were made along the downwind axis. In other cases the aircraft 

arrived during the decay stage of the anvil, but these cases are also important because we know the lightning 

and reflectivity history of that storm relative to the aircraft flights.

6.4.6 Quality Control and Synchronization of Data

Quality control (QC) and synchronization of the ABFM II data took the science team nearly two years because 

it had to be absolutely right if the results were to be reliable enough for the development of launch commit 

criteria. QC and synchronization efforts were divided among various science team institutions with MSFC 

taking the lead on calibration of the airborne field mills and NCAR taking the lead on the remaining QC and 

synchronizations with support from the entire team.

Time synchronization was necessary because of the many separate timing sources in the various data streams. 

The cloud physics and electric field measurements on the aircraft were recorded separately. The KSC/CCAFS 

instrumentation including the critical lightning instrument had its own source of timing. The weather radars, 

WRS-74C and WSR-88D each had its own separate timing source. A timing error on the order of a second or 

more could easily result in attempting to correlate data from one system measured while the aircraft was in 

cloud with another taken when the aircraft was actually outside of a cloud since the aircraft was flying at a 

speed greater than 100 m/s.

Spatial synchronization was also necessary. The aircraft position was well known as a function of time 

because of the high quality of the on-board navigation system. That position had to be connected to specific 

features displayed by two different weather radars, each at its own location with its own scan strategy. This 

required reconciling a set of locally Cartesian aircraft coordinates (latitude, longitude and altitude) with two 

different sets of spherical radar coordinates (altitude angle, azimuth angle and range) and placing all of the 

data into a common coordinate system.

Quality control of the data could not be automated because of the types (including images) and variety, and 

was extremely labor intensive and, hence, lengthy. The output of each instrument was examined by someone 

familiar with its characteristics and weaknesses. Data that seemed questionable at first glance was examined in 

detail and either validated or flagged as bad. In addition to screening the data from each instrument separately, 

the data from multiple sensors were checked for mutual consistency with each other and with the general 

meteorological environment.

After QC and synchronization had been accomplished, an integrated data set was placed on an NCAR website 

where the entire science team could access it to conduct their analysis. As noted in Section 6.0, the data set is 

now available to the public for further research.
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6.4.7 Major Results – VAHIRR

While there were many findings of interest from ABFM II, there were two that resulted in major revisions to 

the LLCC. The first, the development of the VAHIRR quantity, is discussed in this section. The second, the 

possibility of safely reducing the standoff distances in the rules, is presented in the next section.

One motivation for ABFM II was the hope that there existed a radar-derived quantity that could give a reliable 

indication of when electric fields aloft did not exceed 3 kV/m. After exploring a dozen or so potential 

candidates for such a quantity, the team was able to establish that the Volume Averaged Height Integrated 

Radar Reflectivity (VAHIRR) met the requirement. The computation of VAHIRR is described in Dye et al. 

(2006), Krider et al (2006) and Merceret et al (2006) and is too complex to discuss in detail here. Simply, it is 

the product of the average radar reflectivity in dBZ multiplied by the cloud thickness in a specified volume. 

The specified volume is centered on the point at which VAHIRR is being calculated, bounded laterally by a 

square box 11 km on a side, with its bottom at the 0C isotherm and its top at the top of the highest clouds in 

the box. If VAHIRR was less than 10 dBZ-km at a point aloft, then the probability that the electric field was 

greater than 3 kV/m at that point was less than one in ten thousand. Major revisions to the LLCC based on 

VAHIRR were proposed in 2005 and 2008. These revisions permitted the launch constraints for anvil and 

debris clouds to be significantly relaxed with no reduction in safety.

6.4.8 Major Results – Stand-off Distances

The other finding that permitted safe relaxation of the anvil and debris cloud constraints was that electric fields 

outside of anvil and debris clouds remained below 3 kV/m even when fields as high as 70 kV/m or more were 

present in the clouds (Merceret et al, 2008). As a result, the “stand-off distance” from the edge of anvil and 

debris clouds that the LLCC require be maintained for several hours after the last lightning in the cloud or its 

parent thunderstorm could be reduced from 5 to 3 NM. Compare the 2005 version of the LLCC (Appendix I 

Section A1.10) with the current version in Appendix I, Section A1.11, to see the full impact of the changes 

which are actually somewhat more complex than a simple reduction in the standoff distance.

6.4.9 Other Results

Some general findings (Dye et al., 2003, 2006a) from the ABFM II investigation of anvils and debris clouds 

are:

1. When electric fields were strong there was a surprisingly degree of consistency of particle types and 

concentrations in different size ranges; the smaller particles in anvils appear to be frozen cloud 

droplets, particles >100 to 500 μm were primarily irregularly shaped with few pristine crystals, and 

most particles >500 μm were aggregates; there was no evidence of supercooled water within the 

anvils. The largest aggregates were frequently as large as 5 to 6 mm in the dense part of anvils and 

sometimes larger. Surprisingly even near the edges of anvils 1- 2 mm aggregates were often found.

2. As expected, the best correlation between radar reflectivity and particle concentration was for particles 

>3mm in size. Interestingly, the measurements also showed that as the aircraft flew from regions of 

weak reflectivity into regions with higher reflectivity the particle concentrations in all size ranges --

small, medium and large – increased together. That is, particles over the entire particle size spectrum 

increased to reach maximum concentration in the regions of greatest reflectivity. The high reflectivity 

was not only a result of a few large particles, but also a very broad spectrum of particles.

3. Strong electric fields (>10 kV m-1) in anvils were usually associated with regions of higher 

reflectivity. The spatial transition to strong fields was usually quite abrupt as shown in Figure 6.4.9-1 

below. In the figure, the top panel shows the time history of particle concentrations measured by the 

following instruments: PMS FSSP (1 to 48 μm), light, solid line = total conc. on right scale; PMS 2DC (30 μm to ~3 mm), bold line = total conc., dashed line = conc. >1 mm on left scale; PMS 1D-C (15 

to 960 μm), dotted line = total conc. on left scale. The second panel shows the radar reflectivity and 

temperature at the aircraft position as well as the aircraft bank angle. The solid bold line is the radar, 
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the thin solid line the temperature, and the dashed line the bank angle. The third panel shows the radar 

reflectivity curtain above and below the aircraft track from the NEXRAD radar at Melbourne, FL 

(KMLB). The bold line is the aircraft altitude. The bottom panel shows the vertical component of the 

electric field, Ez as a light line on a linear scale (left) and the resultant vector field magnitude, Emag as 

a bold line on a logarithmic scale (right). Entry into the strong fields occurred at about 21:07:20 UTC 

and exit occurred about three minutes later.

Figure 6.4.9-1 Example of the abrupt electric field transition in an anvil

4. There was a threshold behavior between electric field and reflectivity such that below about 5 to 10 

dBZ the electric field was less than 3 kV m-1. This threshold behavior between electric field and 

reflectivity was observed in debris clouds as well as anvils (Dye et al., 2008) and lead to the 

development of the radar-based parameter Volume Averaged Height Integrated Radar Reflectivity 

(VAHIRR) (Dye et al., 2006b).

5. The abrupt transition in anvils from fields ~1 kV m-1 to fields >3 kV m-1 occurred well within the 

cloud so that outside of the anvils and debris clouds the electric fields dropped rapidly to values less 

than those considered a threat for triggering lightning (Merceret et al., 2008).

6. Based on the measured particle size distributions across anvils and a simplified model of the decay of 

electric field in a quiescent anvil, it was estimated that in the dense parts of anvils it could take as long 
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as 1 1/2 hours for the electric field to decay from thunderstorm strength fields of 50 kV/m to fields 

near zero, whereas on the edge of the anvil the decay from an initial field of 50 kV/m to near zero 

could occur in only a few minutes (Willett and Dye, 2003). This large variation is primarily a result of 

the large variation in observed total particle cross-sectional area (i.e. concentration and size) across the 

anvils.

7. Comparison between the observed decay times of electric field in anvils were generally consistent 

with those calculated from the simple model of field decay using observed ice particle size 

distributions, but only one case permitted a meaningful comparison (Willett and Dye, 2003). Further 

carefully designed field investigations are needed to adequately validate this model.

8. A few long-lived anvil cases developed into stratiform-like cloud layers in which both electric fields 

and reflectivity increased and persisted for long periods of time. Both reflectivity and electric fields 

became relatively uniform over appreciable horizontal distances, in one case over 70 km (Dye and 

Willett, 2006).

9. The WSR-88D (NEXRAD) and WSR-74C radar reflectivities agreed to within typical uncertainties 

found in well-calibrated weather radars over the range of reflectivity commonly found in these clouds 

(Dye et al., 2004, p 61.)

6.4.10 Lessons Learned

One thing that quickly became apparent is that following the time evolution of individual cloud volumes with 

an aircraft is extremely difficult. More careful planning will be required in future experiments of this kind if it 

is desired to look at the temporal decay of electric fields in a parcel. Pre-flight planning sessions before every 

campaign and every mission to define key objectives and approaches are wise no matter what the focus of the 

campaign or mission is.

The ability to conduct an airborne experiment in which the flight path depends on the location of rapidly 

developing and moving convective complexes can be severely constrained by the ability and willingness of the 

air traffic control authorities to accommodate the experimenter’s request for access to airspace. Airspace 

flexibility should be considered in selecting the operating location for field programs of this kind, and the FAA 

should be involved in the planning process early on.

6.5 Lightning LCC

This section briefly summarizes not only the LAP discussions directly pertaining to revisions of the LLCC, but 

also their planning and discussions relating to the ABFM II field program and subsequent data analysis. The 

two cannot really be separated. The research was designed from the start to inform revision of the LLCC, and 

the LLCC changes flow directly from new knowledge gained through the research. As with section 5.5, the 

details are provided in Appendix II and only a summary of the key events and conclusions is given here.

6.5.1 ABFM II Planning Discussions

Early in 1999, the KSC Weather Office obtained a small amount of funding from the Space Shuttle program to 

install field mills on a research aircraft that would be taking part that summer in a research project in the 

Pacific. This “target of opportunity” would permit the mills to be installed and flight tested without the 

program having to pay for the flight hours or travel expenses since these were already funded by the research 

project. Also in 1999, the KSCWO was able to assemble combined funding commitments from the Shuttle 

program and other NASA sources to support the dedicated field program in 2000 that became ABFM-II 

described in Section 6.4 above.

The LAP had begun preliminary discussions for a follow-on program to ABFM-I in February 1999. In January 

2000, after funding had been identified, the LAP held a formal ABFM-II planning meeting at KSC to design 

the overall strategy for the 2000 summer field program, including scientific goals and required 

instrumentation. In addition, logistics, schedule and budget issues were addressed. The members of the LAP, 
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representatives from the 45th Weather Squadron, the Spaceflight Meteorology Group, the Applied Meteorology 

Unit, the University of North Dakota, the Air Force Research Laboratories the KSC Weather Office, and 

several KSC administrative offices attended.

At the beginning of the field program in June, final science and operational planning meetings were held. 

Coordination meetings took place between the University of North Dakota pilots and the FAA to facilitate 

access to the air space necessary for the planned observational strategy. Additional planning, frequently by 

telephone, preceded each individual mission during the summer.

Planning for the winter and summer 2001 campaigns followed the same pattern, but took advantage of the 

experience gained during the 2000 campaign, especially with regard to improved coordination with the FAA.

Planning did not stop after the end of the field campaigns. In November 2001 an ABFM II workshop was held 

in Melbourne, Florida at the offices of the AMU contractor, ENSCO, Inc. The LAP and the ABFM science 

team extensively discussed issues relating to the calibration and archiving of the field data. Specific areas of 

research were assigned to specific investigators in order to avoid duplication of effort and provide a 

coordinated, unified approach to maximizing the utility of the data for potential revisions to the LLCC. On a 

smaller scale, such planning continued during teleconferences until the final submission of ABFM-II-based 

recommended LLCC changes by the LAP in 2009.

6.5.2 LLCC Revisions – 2005

The analysis of the ABFM II data led to a determination that the VAHIRR quantity (section 6.4.7 above) could 

serve as the basis for changes in the Anvil rules (both attached and detached) that would significantly reduce 

the number of unnecessary scrubs and delays caused by these rules. The resulting recommendation was 

adopted by NASA and the Air Force. The Shuttle version is presented in detail in Appendix I, section A1.10. 

These rules were very similar to the current rules except that they did not provide for the use of VAHIRR for 

debris clouds, and the stand-off distances for both anvil and debris clouds were longer. Another revision 

(2009) was required to make those changes. A short summary of the changes as implemented in 2005 by the 

Space Shuttle program follows.

Space Shuttle LLCC (2005) [LCN 01166R01, 06/03/05]. MAJOR Changes: This major change was the first 

application of both Harry Koons's truth-table analysis (see the figures in Appendix II), and his statistical 

analysis of the new ABFM II dataset, to both clarify and relax the anvil rules. It is quoted in full in Appendix I, 

Section A1.10. In spite of numerous wording changes throughout, however, there were no substantive changes 

to any of the other rules, except indirectly through changes in the definitions. The key definition change was in 

the radar definition of the cloud boundary, which was lowered from 10 dBZ to 0 dBZ, significantly tightening 

the rules and closing a potentially serious loophole.

A major new exception was provided for both Attached and Detached Anvil Clouds, in terms of a new radar 

parameter called the Volume-Averaged, Height-Integrated Radar Reflectivity (VAHIRR). The new versions of 

the two anvil rules are paraphrased below:

Anvil Clouds:

Attached Anvil Clouds.

Do not fly within 10 nm of any non-transparent, attached anvil for at least 30 minutes after the last lightning 

discharge occurs in the parent cloud or anvil, nor within 5 nm for 3 hours after the last lightning. Never fly 

through such a cloud.

Exception: Flight is allowed through or within any distance of an attached anvil after 30 minutes if that anvil 

is colder than 0 °C and if its VAHIRR is less than 10 dBZ-km everywhere along the flight path.
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Detached Anvil Clouds.

Do not fly within 10 nm of a non-transparent, detached anvil for 30 minutes after the last lightning discharge 

occurs in the detached anvil (or in its parent cloud before detachment), nor within 5 nm for 3 hours after the 

last such lightning. Do not penetrate such an anvil for 3 hours after detachment, nor for 4 hours after it has 

produced lightning.

Two kinds of exceptions are allowed: 1) Flight is allowed up to the edge of a detached anvil between 30 

minutes and 3 hours after the last lightning if the radar reflectivity of all parts of that cloud within 5 nm of the 

flight path has been less than 10 dBZ, and if a field mill within 5 nm of the cloud (and any other mills within 5 

nm of the flight path) have shown less than ±1000 V/m, for at least 15 minutes. 2) Flight is allowed through or 

within any distance of such an anvil after 30 minutes if the cloud is colder than 0 °C and if its VAHIRR is less 

than 10 dBZ-km everywhere along the flight path.

After considerable negotiation with the LAP, the FAA adopted essentially this version of the LLCC, translated 

into their own vocabulary and format to become what they call the LFCC, which are quoted in Appendix I, 

Section A1.12 "Current (through 25 March 2010) FAA LLCC (14 CFR 417, Appendix G)."

6.5.3 LLCC Revisions – 2009

The LAP continued to analyze and discuss the ABFM II data following the development of the 2005 

recommendations discussed above. Two additional major improvements to the rules were found to be justified 

by the analysis: application of the VAHIRR concept to debris clouds in a manner similar to their application to 

anvils, and reduction of the stand-off distances for both anvil and debris clouds (section 6.4.8 above). The final 

product was the recommendation for adoption of the currently effective rules summarized in Chapter 1, section 

1.1 and presented in detail (Space Shuttle Version) in Appendix I, section A1.11. The LAP’s recommendations 

were presented in 2008 in a format requested by the Federal Aviation Administration (FAA) for application to 

the civilian spaceports that were under development throughout the United States. The Space Shuttle program 

adopted these recommendations in substance in 2009 but did not keep the FAA format. A summary of the 

LAP recommendation follows.

This version, quoted in Appendix I, Section A1.13, includes major changes in both language and substance. In 

view of the apparent necessity of working with the FAA in the future, the LAP chose to attempt writing these 

LLCC using FAA language from the beginning.

This is the second application of Dr. Harry Koons's logical analysis and of the ABFM II dataset as further 

analyzed statistically by Paul O'Brien and Frank Merceret. The standoff distances from Attached-Anvil, 

Detached-Anvil and Debris Clouds were reduced from 5 to 3 NM under many conditions, and a VAHIRR 

exception was added to the Debris Cloud Rule. Other significant changes included placing the definitions first 

(to emphasize that they are an important part of the rules), making Surface Electric Fields the first rule (to 

emphasize its importance as the key physical parameter for triggering lightning), adding an explicit 

requirement that all LFCC must be individually satisfied, narrowing the definition of "Anvil," and explicitly 

including a Triboelectrification Rule. Since this rule set has already been paraphrased in Section 1.1, only the 

significantly changed sections will be repeated here.

All of the LLCC must be satisfied.

Attached Anvil Clouds.

Do not fly within 10 nm of any non-transparent, attached anvil for at least 30 minutes after the last lightning 

discharge occurs in the parent cloud or anvil, nor within 5 nm for 3 hours after the last lightning. Never fly 

within 3 nm of such a cloud.
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Two kinds of exceptions are allowed: 1) Flight is allowed up to 3 nm from an attached anvil at any time if it is 

colder than 0 °C everywhere within the prescribed distances of the flight path. 2) Flight is allowed through or 

within any distance of an attached anvil at any time if that anvil is colder than 0 °C and if its VAHIRR is less 

than 10 dBZ-km everywhere within 1 nm of the flight path.

Detached Anvil Clouds.

Do not fly within 10 nm of a non-transparent, detached anvil for 30 minutes after the last lightning discharge 

occurs in the detached anvil (or in its parent cloud before detachment), nor within 3 nm for 3 hours after the 

last such lightning. Do not penetrate such an anvil for 3 hours after detachment, nor for 4 hours after it has 

produced lightning.

Three kinds of exceptions are allowed: 1) Flight is allowed up to 3 nm from such an anvil during the first 30 

minutes if the detached anvil is colder than 0 °C everywhere within a 10 nm of the flight path. 2) Flight is 

allowed up to the edge of a detached anvil between 30 minutes and 3 hours after the last lightning if the radar 

reflectivity of all parts of that cloud within 5 nm of the flight path has been less than 10 dBZ, and if a field mill 

within 5 nm of the cloud (and any other mills within 5 nm of the flight path) have shown less than ±1000 V/m, 

for at least 15 minutes. 3) Flight is allowed through or within any distance of such an anvil at any time if the 

cloud is colder than 0 °C and if its VAHIRR is less than 10 dBZ-km everywhere within the prescribed distances 

of the flight path.

Debris Clouds.

Do not fly within 3 nm of a non-transparent debris cloud for 3 hours after it detaches or decays from its parent 

cloud and for 3 hours after it has produced lightning.

Two kinds of exceptions are allowed to the 3 nm standoff requirement: 1) Flight is allowed up to the edge of a 

debris cloud at any time if the radar reflectivity of any part of that cloud within 5 nm of the flight path has 

been less than 10 dBZ, and if a field mill within 5 nm of the cloud (and any other mills within 5 nm of the flight 

path) have shown less than ±1000 V/m, for at least 15 minutes. 2) Flight is allowed through or within any 

distance of such a debris cloud at any time if the cloud is colder than 0 °C everywhere within 5 nm of the flight 

path and if VAHIRR is less than 10 dBZ-km everywhere within prescribed distances of the flight path.

Triboelectrification.

Do not fly through any cloud (transparent or not) that is colder than -10 oC at vehicle velocities less than 3000 

ft/s unless the vehicle has been treated or hardened against surface discharges.
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Chapter 7 Conclusions and Lessons Learned

The development of the LLCC and their associated Definitions in the post-AC 67 era has been an ongoing 

process of collaboration between the LAP (originally the PRC), the NASA/KSC Weather Office (originally 

the NASA-HQ Weather Support Office), and the Air Force 45WS. As we have seen, the first set of lightning 

launch commit criteria was developed in the wake of the Apollo XII incident, after it was recognized that a 

launch vehicle can trigger lightning. After this incident there was considerable involvement of the scientific 

community at large, and the resulting LLCC were detailed by the Apollo Program in its official accident 

investigation (NASA, 1970, p.50). Thereafter, the LLCC evolved gradually and without formal coordination 

over a succession of manned and unmanned vehicles until the AC 67 accident. This event demonstrated that 

the triggered-lightning hazard was not being taken seriously by launch weather personnel and that the rules 

were not being applied uniformly.

In reaction to the AC 67 accident, a relatively small, blue-ribbon panel of experts, the "Heritage Committee," 

was empowered to undertake an independent study of the issues and draft a much more comprehensive and 

scientifically justified set of LLCC [Heritage, 1988, Chapter 7]. Shortly thereafter, a subset of the Heritage 

Committee was asked to serve on the first standing committee, the PRC, to evaluate and improve the LLCC 

(see Section 5.2.1).

Since the original formation of the PRC/LAP, a dual-track process has evolved. The LAP initiates, re-writes, 

or re-phrases LLCC in response to new scientific knowledge, and the LAP proposes experiments to advance 

knowledge in areas that are important for launch support. The LAP also receives questions and concerns about 

the LLCC and their implementation from launch-weather personnel (particularly the KSC Weather Office and 

the 45WS, and more recently the SMG, the 30WS, and even people at the Kodiak Launch Complex). Out of 

what might easily have become an adversarial relationship due to an imperfect science and the need to apply 

the LLCC in the real world, certain mutual goals have emerged, especially having rules that both improve 

safety and increase launch availability. This process has resulted in growing confidence in, and attention to, 

the LLCC and the associated Definitions. In this chapter we try to summarize the most significant conclusions 

and recommendations that have emerged from this process.

Summarized in a single sentence, the LLCC must be safe, physically valid, complete, not unnecessarily 

restrictive, self-consistent, clear, and faithfully implemented. Each of these requirements and its importance is 

briefly elaborated below:

Safety. First and foremost, the LLCC must be safe. No lightning strikes to vehicles during launch, triggered or 

natural, will occur when the rules are followed. Safety is assured by making the LLCC both physically valid 

and complete, as outlined in the following two sections. The LAP process for achieving these and the other 

goals outlined below has been discussed in Section 5.5.1 above. It bears repeating, however, that launch safety 

and launch availability are competing needs that must be carefully balanced.

Physical Validity. A sound physical basis for the LLCC is an obvious prerequisite for their safe and successful 

application. Furthermore, if individual launch rules could easily be challenged on technical grounds, they 

would quickly be ignored, and the whole LLCC process would lose credibility. The LAP has used the 

scientific literature and the outcomes of recommended experiments to ensure that the LLCC cover the 

meteorological conditions that will produce hazardous electric fields aloft. The science that is behind the 

current rules will be discussed in detail in the Rationale document that is planned to accompany this History.

Completeness. Safety requires that the LLCC identify all meteorological conditions that will create high 

electric fields aloft. Without this completeness, accidents will occur that will call the whole process into 

question. Rather than risk any such accidents, the LAP has started with LLCC that are conservative, and 
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additional instrumentation (e.g., field mills) has been recommended to cover unexpected conditions that might 

be hazardous. By identifying the sources of false alarms, and by recommending new methods of detecting and 

eliminating them, the LAP has incrementally reduced the initial conservatism and increased launch availability 

without sacrificing safety. Nevertheless, there will always be a tradeoff between completeness and launch 

availability in questionable weather situations.

Launch Availability. Close collaboration between the LAP, the 45WS, and the KSC Weather Office has 

emerged as an efficient way to identify individual launch restrictions that have a significant impact on launch 

availability or that appear to have an unduly high false-alarm rate. When attention is focused on these 

situations, solutions can often be found that increase launch availability without compromising safety.

Consistency. There are two important aspects of self-consistency in the LLCC. 1) Within each individual rule, 

the sub-sections should be mutually consistent to prevent confusion and incorrect evaluation by the Launch 

Weather Team (LWT). This issue has been addressed with logical truth-table analysis, which can not only 

eliminate inconsistencies between sections of a given rule but also remove redundancy that can lead to 

ambiguity. 2) Because all rules in the LLCC must be evaluated simultaneously, it is helpful, though not always 

possible, for each rule to be consistent with the others. There will occasionally be ambiguity over which rule 

applies to a given weather situation, because of the inherent subjectivity in evaluation, and in such situations 

all potentially applicable rules must be satisfied.. In these situations, an apparent inconsistency may worry the 

LWT, but if the most conservative criterion is applied, that will insure safety.

Clarity. The LLCC must be clearly written to ensure proper understanding by both customer personnel, who 

must accept them prior to any countdown, and the LWT, which must apply them during the launch. Because it 

is critical for the LWT to evaluate the LLCC quickly and accurately under pressure, the rules themselves 

should be as clear and easy to understand as possible. The close working relationship that has developed 

between the LAP and the 45WS has been invaluable for clarifying the rules and has led to more efficient 

operational use. Nevertheless, increased launch availability without compromising safety comes at the price of 

greater complexity. The desire for lower false-alarm rates has led to the addition of numerous exceptions to the 

basic LLCC that require additional conditions to be satisfied. The LAP has introduced truth tables to facilitate 

better understanding of the rules and make them self-consistent (see figures in Appendix II). These truth-tables 

are also beneficial as training materials.

Faithful Implementation. Even a perfect set of LLCC and definitions cannot assure safety unless they are fully 

and correctly applied during launch operations. The following are requirements for safe implementation: 1) 

The rules must be coordinated with, and certified by, all customers prior to use to ensure that they understand 

and accept the assumptions and associated risks. 2) The LWT must be rigorously and correctly trained, 

certified, tested, and routinely retested during the conditions of a launch countdown. 3) The LLCC must 

continue to be evaluated on the basis of data derived from a reliable, accurate, and robust weather and 

atmospheric-electricity infrastructure. 4) Each member of the LWT must be clearly convinced that each of the 

LLCC has been completely satisfied. 5) The LWT must be managed by a Senior Weather Officer who ensures 

that each LWT team member is aggressively and strictly assessing the LLCC and is freely and constructively 

communicating data and assessments with other LWT members. 6) The Senior Weather Officer in charge must 

ensure that external factors like "launch fever" or visitors, especially VIPs, do not impede or bias the LWT 

evaluations; and that manager must handle all queries, comments, and concerns from higher headquarters and 

other senior management and not on the formal customer Launch Decision Team. 7) The LAP notes that the 

civilian Launch Weather Officers (LWOs) have made a significant contribution to launch safety through 

rigorous training, careful observation, and conscientious application of the LLCC. It is essential to preserve 

this ‘corporate memory’ by maintaining a sufficient number of civilian LWO positions.
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Appendix I The Lightning Launch Commit Criteria (LLCC) and Associated 

Definitions

A1.1 Post Apollo XII Lightning LCC (LLCC) 1970

Space vehicle will not be launched if nominal flight path will carry vehicle:

• Within 5 sm of a cumulonimbus (thunderstorm) cloud;

• Within 3 sm of anvil associated with a thunderstorm;

• Through cold front or squall line clouds which extend above 10K feet;

• Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

• Through cumulus clouds with tops at 10,000 feet or higher.

A1.2 Skylab (1973) LLCC

Space vehicle will not be launched if nominal flight path will carry vehicle

• Within 5 sm of a cumulonimbus (thunderstorm) cloud or within 3 sm of an associated anvil;

• Through cold front or squall line clouds which extend above 10K feet;

• Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

• Through cumulus clouds with tops at 10,000 feet or higher

A1.3 Apollo-Soyuz Lightning LLCC 1975

(Heritage, 1988, p. 4-4)

Space vehicle will not be launched if the nominal flight path will carry vehicle:

A. Through a cumulonimbus (thunderstorm) cloud;

B. Within 5 sm of a cumulonimbus (thunderstorm) cloud or within 3 sm of an associated anvil. This rule 

may be relaxed at the discretion of the Launch Director if the electric field at the launch pad is less 

than 1 kV//m with a very narrow launch window

C. Through cold front or squall line clouds which extend above 10K feet;

D. Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

E. Through cumulus clouds with tops at 10,000 feet or higher;

F. Rules C, D, and E above may be relaxed at the discretion of the Launch Director when electric field 

measurements in the launch pad area are stable and measure less than 1 kV/m.

G. Rules C, D, and E above may be further relaxed provided that airborne and ground electric field 

measurements are less than or equal to 3 kV/m as measured by the ground based field mill network 

and less than or equal to EC(H) where EC(H) varies linearly from 3 kV/m at the surface to 15 kV/m at 

25K feet and remains constant above that altitude. This rule may be applied only if vertical field 

measurements along the flight path in a 3-mile area are within the described envelope and there are no 

rapid fluctuations of about 3 kV/m at about 1 minute intervals within the 3 mile area measured by the 

ground mills.

A1.4 AC 38 (1976) LLCC

Space vehicle will not be launched if nominal flight path will carry vehicle:

• Within 5 sm of a cumulonimbus (thunderstorm) cloud;

• Within 3 sm of anvil associated with a thunderstorm;

• Through cold front or squall line clouds which extend above 10K feet;

• Through middle cloud layers 6000 feet or greater in depth where the freeze level is in the clouds;

• Through cumulus clouds with tops at 10,000 feet or higher.
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A1.5 Original Space Shuttle LLCC 1979

(Heritage, p. 4-7, Table 4-3)

Space vehicle will not be launched if nominal flight path will carry vehicle:

• Through a cumulonimbus (thunderstorm) cloud;

• Within 5 sm (7.8 km) of a cumulonimbus (thunderstorm) cloud or the edge of an associated anvil that 

is within 5 sm of its radar cell. At the discretion of the Launch Director the anvil may be penetrated if 

the static electric field is less than 1kV/m and the 5 sm rule is maintained.

• Through or within 5 sm of any other clouds where radar shows virga or precipitation and tops extend 

(or will extend at the time of launch) above the -10 °C temperature altitude and four or more field 

mills within the launch site have changed more than 500 V/m.

• Through single layer clouds in the dissipation stage and where these clouds have activated the delta 

electric field contours within a period of 10 minutes before launch. The maximum electric fields 

associated with subject cloud as measured on the ground must not exceed 2 kV/m. The electric field 

meter readings for double layer clouds cannot exceed 500 V/m.

A1.6 1986 Shuttle Lightning Launch Commit Criteria (LLCC)

(Heritage, p. 4-8, Table 4-4)

Do not launch if vehicle path is:

• Within 5 nm of a cumulonimbus cloud or the edge of associated anvil cloud;

• Within 5 nm of any convective cloud whose top extends to -20 °C isotherm with virga/precipitation;

• Through any cloud where precipitation is observed;

• Through dissipating clouds in which the electric field network has detected lightning within 15 

minutes prior to launch;

• Through any cloud if ground level electric field at launch site is greater than + or - 1000 V/m.

A1.7 Atlas/Centaur 67 Lightning Launch Commit Criteria (1987)

(Heritage, 1988, p. 4-9, Table 4-5)

Flight path of the vehicle should not be:

A. Through a thunderstorm/cumulonimbus cloud.

B. Within 5 miles of thunderstorm/cumulonimbus cloud or 3 miles of associated anvil top.

C. Through cold front/squall line associated clouds with tops 10,000 ft or higher.

D. Through middle-level cloud layers, 6,000 ft or greater in depth, when the freezing level is in the 

clouds.

E. Through cumulus clouds with the freezing level in the clouds.
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A1.8 Heritage LRC Recommended LLCC (1988)

(Heritage, 1988, pp. 7-1 through 7-6)

LAUNCH CONSTRAINTS FOR THE AVOIDANCE OF VEHICLE-TRIGGERED LIGHTNING, 

NATURAL LIGHTNING, AND VEHICLE ELECTRIFICATION

The following launch constraints must be observed. They are designed to minimize the hazards to launch 

vehicles after launch from vehicle-triggered lightning, natural lightning, and vehicle electrification resulting 

from interactions with the environment.

Good Sense Rule: If hazardous conditions exist that approach the launch constraint limits or if hazardous 

conditions are believed to exist for any other reason, an assessment of the nature and severity of the threat shall 

be made and reported to the Test Director and Mission Director.

Constraint I. The vehicle will not be launched if any type of lightning is detected within 10 nmi of the launch 

site and within 30 minutes prior to launch time. The 30-minute time period in Constraint I may be terminated 

at the discretion of the Test Director and Mission Director if the meteorological condition that produced the 

lightning has moved more than 10 nmi away from the launch complex and planned flight path.

Constraint II. The vehicle will not be launched if the planned flight path is:

a1. Through cumulus clouds with tops that extend to an altitude above the +5 °C temperature level; or

a2. Through or within 5 nmi of cumulus clouds with tops that extend to an altitude higher than the -10 °C 

temperature level; or

a3. Through or within 10 nmi of cumulus clouds with tops that extend to an altitude higher than the -20 °C 

temperature level; or

a4. Through or within 10 nmi of the nearest edge of either a cumulonimbus cloud or a thunderstorm 

including the associated anvil; or

b. Through or within 5 nmi of a cloud layer, other than a thin transparent fibrous layer, that has become 

detached from a parent cumulonimbus cloud; or

c. Through any cloud types that extend to altitudes at or above the 0 °C temperature level and that are 

associated with disturbed weather within 5 nmi of the flight path; or

d. Through a vertically continuous layer of clouds with an overall depth of 4,500 ft, or greater, where any 

part of the clouds is located between the 0 °C and the -20 °C temperature levels.

The 10-nmi distance in Constraint IIa may be reduced to 5 nmi at the discretion of the Test Director and 

Mission Director if, in the 15 minutes prior to launch time:

a. The electric field intensity at the ground (for ranges that have a ground field mill system) has remained 

below 1 kV/m within 5 nmi of the launch pad; and

b. The absolute value of the instantaneous critical electric field intensity sampled along the flight path is 

less than the critical value, Ec, shown as a function of altitude in Figure 7-1.

Constraint IIa,, IIa2, IIb, IIc, and IId may be dispensed with at the discretion of the Test Director and Mission 

Director if, in the 15 minutes prior to launch time:

a. The electric field intensity at the ground (for ranges that have a ground field mill system) has remained 

below 1 kV/m within 5 nmi of the launch pad; and

b. The absolute value of the instantaneous critical electric field intensity within the clouds sampled along 

the flight path is less than the critical value, Ec, shown as a function of altitude in Figure 7-1. (Figure 

A1.8-1)
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Figure A1.8-1 Heritage (1988) Fig. 7-1, Instantaneous Critical Electric Field Intensity vs Altitude

Constraint III. The vehicle will not be launched if, at any time during the 15 minutes prior to launch time, the 

electric field intensity at the ground exceeds 1 kV/m anywhere within a 5-nmi radius of the launch pad. 

Constraint III may be dispensed with at the discretion of the Test Director and Mission Director if:

a. There are no clouds within 10 nmi of the launch pad at the planned time of launch; and

b. The absolute value of the instantaneous critical electric field intensity sampled along the flight path 

during the 15 minutes prior to launch is less than the critical value, Ec shown as a function of altitude 

in Figure 7-1.
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Constraint IV. A vehicle that has not been treated for surface electrification will not be launched if the planned 

flight path will go through clouds in the altitude regime extending upward from the -10 °C temperature level to 

the altitude at which the vehicle velocity exceeds 3000 ft/sec.

Definitions. The following definitions apply to the constraints above:

a. The term "nearest edge" of a cloud, as used in Constraint IIa, refers to the 10-dBZ level as measured 

by a weather radar or the visible edge. NOTE: The distance to the nearest edge is omnidirectional and 

includes the top of the cloud when the vehicle is above a cloud.

b. The term "disturbed weather", in Constraint IIc, refers to any meteorological phenomenon that is 

producing moderate or greater precipitation.

c. "Vertically continuous cloud layer", as used in Constraint IId, refers to any array of clouds, not 

necessarily all of the same type, in which some cloud elements connect the entire thickness of the

array.

d. "Electric field intensity", as used in Constraints II and III, means the absolute value of the 1-minute 

time average of the instantaneous, ground-level electric field intensity obtained from an analysis of 

ground-based electric field mill data.

e. The term "critical value", as pertains to the electrical field intensity and which is used in Constraints II 

and III, refers to the absolute value of the instantaneous minimum electric field that will just cause 

electrical breakdown. This value will be a function of altitude as shown in Figure 7-1. (Other factors, 

not considered herein, that may contribute to the electrical breakdown of the atmosphere include 

vehicle velocity and spatial extent of the electric field. The presence of nearby or distant lightning or 

cloud conditions also may be contributing factors.)

f. A vehicle is considered "treated" for surface electrification in Constraint IV if all surfaces of the 

vehicle susceptible to precipitation particle impact have been treated to assure:

1. That the surface resistivity is less than 109 ohms/square, and

2. That all conductors on surfaces (including dielectric surfaces that have been treated with 

conductive coatings) are bonded to the vehicle structure by a resistance that is less than 105 ohms.
Page 93 of 234

A1.9 Space Shuttle LLCC (1992 – 1998)

A1.9.1 Space Shuttle LLCC (1992)[LCN# 00230R04]

4.5 Natural and Triggered Lightning Constraints.

NOTICE: ANY CHANGES TO THIS SECTION WILL REQUIRE COORDINATION WITH EASTERN

 SPACE AND MISSILE CENTER RANGE SAFETY OFFICE.

Even when constraints are not violated, if any other hazardous conditions exist, the Launch Weather Officer 

will report the threat to the Launch Director. The Launch Director may HOLD at any time based on the 

instability of the weather. The Launch Weather Officer must have clear and convincing evidence the following 

constraints are not violated.

 A. Do not launch if any type of lightning is detected within 10 nautical miles of the launch site or 

planned flight path within 30 minutes prior to launch, unless the meteorological condition that produced the 

lightning has moved more than 10 nautical miles away from the launch site or planned flight path.

 B. Do not launch if the planned flight path will carry the vehicle:

 (1) Through cumulus clouds with tops higher than the 5 degrees Celsius level; or

 (2) Through or within 5 nautical miles of cumulus clouds with tops higher than the -10 degrees 

Celsius level; or

 (3) Through or within 10 nautical miles of cumulus clouds with tops higher than the -20 degrees 

Celsius level; or

 (4) Through or within 10 nautical miles of the nearest edge of any cumulonimbus or thunderstorm 

cloud including its associated anvil.

 C. Do not launch if, for Ranges equipped with a surface electric field mill network, at any time during 

the 15 minutes prior to launch time the one minute average of absolute electric field intensity at the ground 

exceeds 1 kilovolt per meter (1kV/m) within 5 nautical miles of the launch site unless:

 (1) There are no clouds within 10 nautical miles of the launch site; and

 (2) Smoke or ground fog is clearly causing abnormal readings.

 NOTE: For confirmed instrumentation failure, continue countdown.

 Relative to (1): the following clouds are acceptable if they have not been previously associated with 

a thunderstorm, or convective clouds with tops greater than -10 degree Celsius temperature level within the 

last three hours:

 (a) Thin fibrous (optically transparent) clouds;

 (b) Less than or equal to 2/8 cumulus/strato-cumulus/ stratus (CU/SC/ST) clouds with tops below 

or equal to the +5 degree Celsius temperature level. For example, 3/8 CU/SC/ST is not acceptable regardless 

of cloud top level, nor is any CU/SC/ST cloud amount above the +5 degree Celsius temperature level.
Page 94 of 234

 Relative to (2): This also includes a maritime inversion with an onshore/alongshore wind present 

over the electric field mills, causing those mills located near the ocean to be elevated with a positive polarity 

between 1kV/m and 1.5kV/m inclusive.

 D. Do not launch if the planned flight path is through a vertically continuous layer of clouds with an 

overall depth of 4,500 feet or greater where any part of the clouds are located between the zero (0) degree and 

the minus 20 (-20) degree Celsius temperature levels.

 E. Do not launch if the planned flight path is through any cloud types that extend to altitudes at or above 

the zero degree Celsius temperature level and that are associated with disturbed weather within 5 nautical 

miles of the flight path.

 F. Do not launch through thunderstorm debris clouds, or within 5 nautical miles of thunderstorm debris 

clouds not monitored by a field mill network or producing radar returns greater than or equal to 10 dBz.

 G. Definitions

 (1) Debris Cloud: Any cloud layer, other than a thin fibrous layer, that has become detached from the 

parent cumulonimbus within 3 hours before launch.

 (2) Disturbed Weather: Any meteorological phenomenon that is producing moderate or greater 

precipitation.

 (3) Cumulonimbus Cloud: Any convective cloud which exceeds the -20 degree Celsius temperature 

level.

 (4) Cloud Layer: Any cloud broken or overcast layer or layers connected by cloud elements, e.g. 

turrets from one cloud layer to another.

 (5) Planned Flight Path: The trajectory of the flight vehicle from the launch pad through its flight 

profile until it reaches the altitude of 100,000 feet. The flight path may vary plus or minus 0.5 nautical miles 

horizontally up to an altitude of 25,000 feet.

 (6) Anvil: Stratiform or fibrous cloud produced by the upper level outflow from thunderstorms or 

convective clouds. Anvil debris does not meet the definition if it is optically transparent.

 ELECTRICAL CHARGE REGIONS CAN OCCUR IN CLOUDS WITH ALTITUDES AT OR 

ABOVE THE ZERO DEGREE CELSIUS ISOTHERM. THESE CHARGE REGIONS CAN PRODUCE 

NATURAL LIGHTNING DISCHARGES OR DISCHARGES THAT ARE TRIGGERED BY THE 

PROXIMITY OF LONG ELECTRICAL CONDUCTORS (LAUNCH VEHICLE PLUS CONDUCTIVE 

PORTION OF PLUME).

 THE ABOVE CONSTRAINTS ARE FOR THE AVOIDANCE OF NATURAL OR TRIGGERED 

LIGHTNING AND ARE BASED ON THE KNOWN CLOUD TYPES WHICH CAN PRODUCE 

DISCHARGES AND THE DISTANCES TO THE CHARGE REGIONS AT WHICH DISCHARGES ARE 

KNOWN TO OCCUR.
Page 95 of 234

A1.9.2 Space Shuttle LLCC (1995)[LCN# 00520R03]

4.5 Natural and Triggered Lightning Constraints.

NOTICE: ANY CHANGES TO THIS SECTION WILL REQUIRE COORDINATION WITH THE 30TH 

AND 45TH SPACE WING RANGE SAFETY OFFICES.

Even when constraints are not violated, if any other hazardous conditions exist, the Launch Weather Officer 

will report the threat to the Launch Director. The Launch Director may HOLD at any time based on the 

instability of the weather.

The Launch Weather Officer must have clear and convincing evidence the following constraints are not 

violated:

 A. Do not launch if any type of lightning is detected within 10 nautical miles (NM) of the flight path 

within 30 minutes prior to launch, unless the meteorological condition that produced the lightning has moved 

more than 10 NM away from the flight path.

 NATURAL LIGHTNING IS AN OBVIOUS HAZARD (COMPARED TO VEHICLE TRIGGERED 

LIGHTNING) AND IS ALSO THE MOST DIRECT EVIDENCE ELECTRIC FIELDS ARE PRESENT 

WITH SUFFICIENT INTENSITY TO CAUSE TRIGGERED LIGHTNING. THE MEASURED 

FREQUENCY DISTRIBUTION OF THE DISTANCE BETWEEN SUCCESSIVE FLASHES TO GROUND 

APPROACHES ZERO NEAR 6 NM; THUS 10 NM PROVIDES A SAFETY FACTOR. THE 30 MINUTE 

TIME PERIOD WITHOUT LIGHTNING INDICATES THE STORM HAS DISSIPATED OR MOVED 

AWAY. HOWEVER, FORECASTERS MUST STILL REMAIN ALERT FOR REDEVELOPMENT OR 

FORMATION OF A NEW CELL.

 B. Do not launch if the flight path will carry the vehicle:

 (1) Through a cumulus cloud with its top between the +5.0 degrees Celcius (C) and -5.0 deg. C levels 

unless:

 (a) The cloud is not producing precipitation;

 -AND-

 (b) The horizontal distance from the furthest edge of the cloud top to at least one working field mill 

is less than the altitude of the -5.0 deg. C level or 3 NM whichever is smaller.

 -AND-

 (c) All field mill readings within 5 NM of the flight path are between -100 V/m and +1000 V/m for 

the preceeding 15 minutes.

 (2) Through cumulus clouds with tops higher than the -5.0 deg. C level.

 (3) Through or within 5 NM (horizontal or vertical) of the nearest edge of cumulus clouds with tops 

higher than the -10.0 deg. C level.

 (4) Through or within 10 NM (horizontal or vertical) of the nearest edge of any cumulonimbus or 

thunderstorm cloud, including nontransparent parts of its anvil.
Page 96 of 234

 (5) Through or within 10 NM (horizontal or vertical) of the nearest edge of a nontransparent detached 

anvil for the first hour after detachment from the parent thunderstorm or cumulonimbus cloud.

 NOTE: 'Cumulus' does not include Altocumulus or Stratocumulus.

 B(1): CUMULUS (CONVECTIVE) CLOUDS CAN DEVELOP AND PRODUCE ELECTRIC 

CHARGE VERY RAPIDLY. NORMALLY THIS OCCURS WELL ABOVE THE FREEZING LEVEL. 

HOWEVER, THE +5.0 DEG. C LEVEL WAS SPECIFIED BECAUSE ELECTRIC CHARGE HAS BEEN 

SPECULATED TO OCCUR IN SOME 'WARM' CLOUDS IN THE TROPICS AND BECAUSE CUMULUS 

CLOUDS CAN BUILD VERY RAPIDLY. CHARGE SUFFICIENT TO TRIGGER LIGHTNING IS 

NORMALLY NOT DETECTED UNTIL THE CLOUD REACHES WELL ABOVE THE -10.0 DEG. C 

LEVEL. THUS, IF THE CLOUD IS NOT PRODUCING PRECIPITATION (PRECIPITATION IS 

BELIEVED TO BE A NECESSARY CONDITION FOR CLOUD ELECTRIFICATION) AND THE 

GROUND BASED FIELD MILLS ARE NOT MEASURING ELEVATED ELECTRIC FIELDS 

ASSOCIATED WITH THE ONSET OF CUMULUS CLOUD ELECTRIFICATION, THEN LAUNCH MAY 

BE PERMITTED THROUGH CLOUDS BELOW THE -5.0 DEG. C LEVEL.

 B(2): AS CLOUD TOPS APPROACH -10.0 DEG. C, CHARGE MAY DEVELOP VERY RAPIDLY. 

THUS, NO LAUNCH IS PERMITTED THROUGH CLOUDS WITH TOPS AT OR ABOVE -5.0 DEG. C.

 B(3): CLOUDS WITH TOPS ABOVE -10.0 DEG. C CAN CREATE ELECTRIC FIELDS OUTSIDE 

THE CLOUD WITH SUFFICIENT STRENGTH TO TRIGGER LIGHTNING. THUS, NO FLIGHT PATH 

IS PERMITTED WITHIN 5 NM, HORIZONTALLY OR VERTICALLY, OF CLOUDS FROM -10.0 DEG. 

C TO -20.0 DEG. C.

 B(4): THE MOST DANGEROUS CLOUD IS THE CUMULONIMBUS WHICH TYPICALLY 

PRODUCES NATURAL LIGHTNING. THUS, THE DISTANCE CRITERION (10 NM) IS THE SAME AS 

FOR NATURAL LIGHTNING IN RULE A. DANGEROUS ELECTRIC CHARGE CAN ALSO BE 

ADVECTED INTO THE HIGH LEVEL ANVIL PRODUCED BY A CUMULONIMBUS CLOUD, THUS 

THE FLIGHT PATH MUST REMAIN 10 NM, HORIZONTALLY AND VERTICALLY, FROM THE 

ANVIL.

 B(5): SIGNIFICANT CHARGE CAN REMAIN IN AN ANVIL FOR UP TO ONE HOUR AFTER IT 

DETACHES FROM ITS PARENT SOURCE CLOUD. THUS, THE SAME 10 NM DISTANCE 

CRITERION APPLIES AS IN RULE B(4). AFTER 1 HOUR THE DETACHED CLOUD IS TREATED PER 

RULE F.

 C. Do not launch if, for Ranges equipped with a working surface electric field mill network, at any time 

during the 15 minutes prior to launch time the absolute value of any electric field intensity measurement at the 

ground is greater than 1000 V/m within 5 NM of the flight path unless:

 (1) There are no clouds within 10 NM miles of the flight path except:

 (a) transparent clouds,

 -OR-

 (b) clouds with tops below the +5.0 deg. C level that have not been associated with convective 

clouds with tops above the -10.0 deg. C level within the last 3 hours.

 -AND-
Page 97 of 234

 (2) A known source of electric field (such as ground fog) that is occurring near the sensor, and that 

has been previously determined and documented to be benign, is clearly causing the elevated readings.

 NOTE: For confirmed failure of the surface field mill system, the countdown and launch may 

continue, since the other lightning LCC completely describe unsafe meteorological conditions.

 GROUND BASED FIELD MILLS (GBFM) JUST MEASURE THE ELECTRIC POTENTIAL AT THE 

EARTH'S SURFACE. THEY CAN ONLY INFER THE ELECTRIC FIELD IN AND NEAR CLOUDS 

ALOFT (WHICH PERHAPS DECREASE WITH THE HORIZONTAL DISTANCE CUBED AND THE 

CHARGE HEIGHT SQUARED); AND THEIR READINGS CAN BE MASKED BY INTERVENING 

LAYERS OF SPACE CHARGE BETWEEN THE MILLS AND THE CLOUD. MEASUREMENTS OF 

CHARGE ALOFT USING AIRCRAFT EQUIPPED WITH FIELD MILLS, AND EXPERIMENTS WITH 

ROCKETS FIRED INTO CLOUDS TO TRIGGER LIGHTNING, INDICATE GBFM MEASUREMENTS 

GREATER THAN 1000 V/M CAN BE INDICATIVE OF ELECTRIC FIELDS ALOFT SUFFICIENTLY 

HIGH TO TRIGGER LIGHTNING.

 THERE ARE OTHER NEAR-SURFACE SOURCES OF ELECTRIC CHARGE NOT RELATED TO 

CHARGE ALOFT; FOR INSTANCE GROUND FOG, SMOKE, POWER LINES, SEA SPRAY, ETC. IF 

THERE IS NO POSSIBLE SOURCE OF CHARGE ALOFT AND THERE IS A CONFIRMED, 

DOCUMENTED SOURCE OF NEAR-SURFACE CHARGE, THEN THIS RULE IS NOT VIOLATED.

 NOTE: 'DOCUMENTED' MEANS SUFFICIENT DATA HAS BEEN GATHERED ON THE 

PHENOMENA TO PROPERLY STUDY IT, AND CIRCUMSTANCES CAUSING IT TO BE PRESENT 

ARE UNDERSTOOD AND WRITTEN IN A TECHNICAL REPORT.

 D. Do not launch if the flight path is through a vertically continuous layer of clouds with an overall 

depth of 4,500 feet or greater where any part of the clouds is located between the 0.0 deg. C and the -20.0 deg 

C levels.

 THIS RULE COVERS STRATIFORM CLOUDS. ELECTRIFICATION PROCESSES PRIMARILY 

OCCUR WITHIN CLOUDS BETWEEN -0.0 AND -20.0 DEG. C, AND INCREASE WITH INCREASING 

CLOUD THICKNESS. IF CLOUD LAYERS ARE CONNECTED BY TURRETS, THE CLOUD LAYER 

DEPTH IS DETERMINED BY MEASURING FROM THE BASE OF THE LOWER CLOUD LAYER TO 

THE TOP OF THE HIGHER CLOUD LAYER. THE TURRETS INDICATE POSSIBLE CHARGE 

PRODUCING CONVECTION, AND THE CHARGE MAY BE ADVECTED INTO THE INDIVIDUAL 

LAYERS. THUS, AN INDIVIDUAL CLOUD LAYER MAY NOT BE 4500 FEET THICK BUT THE RULE 

MAY BE VIOLATED IF TWO LAYERS ARE CONNECTED AND THEIR LAYERS SUM TO 4500 FEET 

OR GREATER.

 E. Do not launch if the flight path is through any clouds that:

 (1) Extend to altitudes at or above the 0.0 deg.C level, and

 (2) Are associated with disturbed weather that is producing moderate (29 dBz) or greater precipitation 

within 5 NM of the flight path.

 CLOUDS EXTENDING ABOVE THE FREEZING LEVEL AND SUFFICIENTLY ACTIVE TO 

PRODUCE MODERATE OR GREATER PRECIPITATION CAN ALSO CREATE ELECTRIC CHARGE. 

THIS CHARGE CAN BE ADVECTED INTO ASSOCIATED CLOUDS AND CAN CREATE ELECTRIC 
Page 98 of 234

FIELDS AT A DISTANCE. THUS, IF THE PRECIPITATION IS WITHIN 5 NM, THIS RULE IS 

VIOLATED.

 F. Do not launch if the flight path will carry the vehicle:

 (1) Through any nontransparent thunderstorm or cumulonimbus debris cloud during the first 3 hours 

after the debris cloud formed from the parent cloud.

 (2) Within 5 NM (horizontal or vertical) of the nearest edge of a nontransparent thunderstorm or 

cumulonimbus debris cloud during the first 3 hours after the debris cloud formed from a parent cloud, 

UNLESS:

 (a) There is at least one working field mill within 5 NM of the debris cloud;

 -AND-

 (b) All electric field intensity measurements at the ground are between +1000 V/m and -1000V/m 

within 5 NM of the flight path during the 15 minutes preceding the launch time;

 -AND-

 (c) The maximum radar return from the entire debris cloud is less than 10 dBz during the 15 

minutes preceding launch time.

 (3) The start of the 3-hour period is reckoned as follows:

 (a) DETACHMENT. If the cloud detaches from the parent cloud:

 The 3-hour period begins at the time when cloud detachment is observed or at the time of the last 

detected lightning discharge (if any) from the detached debris cloud, whichever is later.

 (b) DECAY or DETACHMENT UNCERTAIN. If it is not known whether the cloud is detached or 

the debris cloud forms from the decay of the parent cloud: The 3-hour period begins at the time when the 

parent cloud top decays to below the altitude of the -10.0 deg. C level, or at the time of the last detected 

lightning discharge (if any) from the parent cloud or debris cloud, whichever is later.

 CLOUDS PRODUCED BY CUMULONIMBUS AND THUNDERSTORMS CAN RETAIN THEIR 

CHARGE EVEN AFTER THE PARENT STORM HAS DECAYED AND STOPPED PRODUCING 

CHARGE, OR AFTER THE CLOUD HAS BROKEN AWAY FROM THE CHARGE SOURCE. 

AIRBORNE FIELD MILL MEASUREMENTS SUGGEST MOST OF THE CHARGE HAS DECAYED 

WITHIN 90 MINUTES. HOWEVER, THE CRITERION WAS SET AT THREE HOURS DUE TO THE 

UNCERTAINTY REGARDING THE START OF THE CLOUD DECAY OR CLOUD BREAKOFF TIME, 

AND THE POSSIBILITY OF BRIEF INTERNAL CHARGE GENERATION WITHIN THE CLOUD EVEN 

AFTER BREAKING OFF FROM THE PARENT CLOUD.

 SINCE NEGLIGIBLE RADAR RETURNS AND BENIGN GBFM READINGS INDICATE THE 

CLOUD IS NOT PRODUCING CHARGE, AND ANY RESIDUAL CHARGE HAS DECAYED 

SUBSTANTIALLY, THEN THE 5 NM STANDOFF CAN BE REDUCED TO JUST A 'FLIGHT 

THROUGH' PROHIBITION. NOTE: BENIGN GBFM VALUES CAN NOT BE USED BY THEMSELVES 

TO CONCLUDE THE CLOUD CAN BE SAFELY PENETRATED, SINCE SHIELDING LAYERS CAN 

MASK SIGNIFICANT FIELDS (AND CHARGE) INSIDE THE CLOUDS FROM THE GBFM NETWORK.
Page 99 of 234

 TRANSPARENT DEBRIS CLOUDS ARE NOT CONSIDERED CAPABLE OF CARRYING 

SUFFICIENT CHARGE TO BE DANGEROUS.

 G. Definitions/Explanations

 (1) Anvil: Stratiform or fibrous cloud produced by the upper level outflow or blow-off from 

thunderstorms or convective clouds.

 (2) Cloud Edge: The visible cloud edge is preferred. If this is not possible, then the 10 dBZ radar 

cloud edge is acceptable.

 (3) Cloud Layer: An array of clouds, not necessarily all of the same type, whose bases are 

approximately at the same level. Also, multiple arrays of clouds at different altitudes that are connected 

vertically by cloud elements, e.g., turrets from one cloud array to another. Convective clouds (e.g., clouds 

falling under Rule B) are excluded from this definition unless they are imbedded with other cloud types.

 (4) Cloud Top: The visible cloud top is preferred. If this is not possible, then the 13 dBZ radar cloud 

top is acceptable.

 (5) Cumulonimbus Cloud: Any convective cloud with any part above the -20.0 deg. C temperature 

level.

 (6) Debris Cloud: Any nontransparent cloud, that has become detached from a parent cumulonimbus 

cloud or thunderstorm, or results from the decay of a parent cumulonimbus cloud or thunderstorm.

 (7) Documented: With respect to Rule C(2), 'documented' means sufficient data has been gathered on 

the benign phenomena to both understand it and to develop procedures to evaluate it, and the supporting data 

and evaluation have been reported in a technical report, journal article, or equivalent publication. For launches 

at the Eastern Range, copies of the documentation shall be maintained by the 45th Weather Squadron and the 

KSC Weather Projects Office. The procedures used to assess the phenomena during launch countdowns shall 

be documented and implemented by the 45th Weather Squadron.

 (8) Electric Field (for surface based electric field mill measurements): The one-minute arithmetic 

average of the vertical electric field (Ez) at the ground, such as measured by a ground based field mill. The 

polarity of the electric field is the same as that of the potential gradient; that is, the polarity of the field at the 

ground is the same as that of the charge overhead.

 (9) Flight Path: The planned flight trajectory including its uncertainties ('error bounds').

 (10) Precipitating Cloud: Any cloud containing precipitation, producing virga, or having radar 

reflectivity greater than 13 dBZ.

 (11) Thunderstorm: Any cloud that produces lightning.

 (12) Transparent: Synonymous with visually transparent. Sky cover through which higher clouds, 

blue sky, stars, etc., may be clearly observed from below. Also, sky cover through which terrain, buildings, 

etc., may be clearly observed from above. Sky cover through which forms are blurred, indistinct, or obscured 

is not transparent.
Page 100 of 234

A1.9.3 Space Shuttle LLCC (1998)[LCN# 00824R03]

4.4 NATURAL AND TRIGGERED LIGHTNING CONSTRAINTS.

NOTICE: ANY CHANGES TO THIS SECTION WILL REQUIRE COORDINATION WITH THE 30TH 

AND 45TH SPACE WING RANGE SAFETY OFFICES.

Natural and Triggered Lightning Launch Commit Criteria (LCC)

The Launch Weather Team must have clear and convincing evidence that the following hazard avoidance 

criteria are not violated.

Even when these criteria are not violated, if any other hazardous condition exists, the Launch Weather Team 

will report the threat to the Launch Director. The Launch Director may HOLD at any time based on the 

instability of the weather.

 1. Lightning

 a) Do not launch for 30 minutes after any type of lightning occurs in a thunderstorm if the flight path will 

carry the vehicle within 10 NM of that thunderstorm.

 b) Do not launch for 30 minutes after any type of lightning occurs within 10 NM of the flight path 

unless:

 (1) The cloud that produced the lightning is not within 10 NM of the flight path;

 -and-

 (2) There is at least one working field mill within 5 NM of each such lightning flash;

 -and-

 (3) The absolute values of all electric field measurements at the surface within 5 NM of the flight path 

and at the mill(s) specified in (2) above have been less than 1000 V/m for 15 minutes.

 Notes:

 i) Anvils are covered in Criterion 3.

 ii) If a cumulus cloud remains 30 minutes after the last lightning occurs in a thunderstorm then Criterion 

2 applies.

 Definitions: Anvil, Electric Field Measurement at the Surface, Flight Path, Thunderstorm, Within

 2. Cumulus Clouds

 a) Do not launch if the flight path will carry the vehicle within 10 NM of any cumulus cloud with its 

cloud top higher than the -20 deg C level.

 b) Do not launch if the flight path will carry the vehicle within 5 NM of any cumulus cloud with its cloud 

top higher than the -10 deg C level.
Page 101 of 234

 c) Do not launch if the flight path will carry the vehicle through any cumulus cloud with its cloud top 

higher than the -5 deg C level.

 d) Do not launch if the flight path will carry the vehicle through any cumulus cloud with its cloud top 

between the +5 deg C and -5 deg C levels unless:

 (1) The cloud is not producing precipitation;

 -and-

 (2) The horizontal distance from the center of the cloud top to at least one working field mill is less 

than 2 NM;

 -and-

 (3) All electric field measurements at the surface within 5 NM of the flight path and at the mill(s) 

specified in (2) above have been between -100 V/m and +500 V/m for 15 minutes.

 Note: Cumulus clouds in Criterion 2 do not include altocumulus, cirrocumulus or stratocumulus.

 Definitions: Cloud Top, Electric Field Measurement at the Surface, Flight Path, Precipitation, Within

 3. Anvil Clouds

 a) Attached anvils:

 (1) Do not launch if the flight path will carry the vehicle through nontransparent parts of attached anvil 

clouds.

 (2) Do not launch if the flight path will carry the vehicle within 5 NM of nontransparent parts of 

attached anvil clouds for the first 3 hours after the time of the last lightning discharge that occurs in the parent 

cloud or anvil cloud.

 (3) Do not launch if the flight path will carry the vehicle within 10 NM of nontransparent parts of 

attached anvil clouds for the first 30 minutes after the time of the last lightning discharge that occurs in the 

parent cloud or anvil cloud.

 b) Detached Anvils:

 (1) Do not launch if the flight path will carry the vehicle through nontransparent parts of a detached 

anvil cloud for the first 3 hours after the time that the anvil cloud is observed to have detached from the parent 

cloud.

 (2) Do not launch if the flight path will carry the vehicle through nontransparent parts of a detached 

anvil cloud for the first 4 hours after the time of the last lightning discharge that occurs in the detached anvil 

cloud.

 (3) Do not launch if the flight path will carry the vehicle within 5 NM of nontransparent parts of a 

detached anvil cloud for the first 3 hours after the time of the last lightning discharge that occurs in the parent 

cloud or anvil cloud before detachment or in the detached anvil cloud after detachment unless:
Page 102 of 234

 (a) There is at least one working field mill within 5 NM of the detached anvil cloud;

 -and-

 (b) The absolute values of all electric field measurements at the surface within 5 NM of the flight 

path and at the mill(s) specified in (a) above have been less than 1000 V/m for 15 minutes;

 -and-

 (c) The maximum radar return from any part of the detached anvil cloud within 5 NM of the flight 

path has been less than 10 dBZ for 15 minutes.

 (4) Do not launch if the flight path will carry the vehicle within 10 NM of nontransparent parts of a 

detached anvil cloud for the first 30 minutes after the time of the last lightning discharge that occurs in the 

parent cloud or anvil cloud before detachment or in the detached anvil cloud after detachment.

 Note: Detached anvil clouds are never considered DEBRIS CLOUDS, nor are they covered by Criterion 

4.

 Definitions: Anvil, Debris Cloud, Flight Path, Nontransparent, Thunderstorm, Within

 4. Debris Clouds

 a) Do not launch if the flight path will carry the vehicle through any nontransparent parts of a debris 

cloud during the 3-hour period defined below.

 b) Do not launch if the flight path will carry the vehicle within 5 NM of any nontransparent parts of a 

debris cloud during the 3-hour period defined below, unless:

 (1) There is at least one working field mill within 5 NM of the debris cloud;

 -and-

 (2) The absolute values of all electric field measurements at the surface within 5 NM of the flight path 

and at the mill(s) specified in (1) above have been less than 1000 V/m for 15 minutes;

 -and-

 (3) The maximum radar return from any part of the debris cloud within 5 NM of the flight path has 

been less than 10 dBZ for 15 minutes.

 The 3-hour period in a) and b) above begins at the time when the debris cloud is observed to have 

detached from the parent cloud or when the debris cloud is observed to have formed from the decay of the 

parent cloud top below the altitude of the -10 deg C level. The 3-hour period begins anew at the time of any 

lightning discharge that occurs in the debris cloud.

 Definitions: Cloud Top, Debris Cloud, Electric Field Measurement at the Surface, Flight Path,

Nontransparent, Within

 5. Disturbed Weather
Page 103 of 234

 Do not launch if the flight path will carry the vehicle through any nontransparent clouds that are 

associated with a weather disturbance having clouds that extend to altitudes at or above the 0 deg C level and 

contain moderate or greater precipitation or a radar bright band or other evidence of melting precipitation 

within 5 NM of the flight path.

 Definitions: Associated, Flight Path, Moderate Precipitation, Nontransparent, Weather Disturbance, 

Within

 6. Thick Cloud Layers

 Do not launch if the flight path will carry the vehicle through nontransparent parts of a cloud layer that 

is:

 (1) Greater than 4,500 ft thick and any part of the cloud layer along flight path is located between the 0 

deg C and the -20 deg C levels;

 -or-

 (2) Connected to a cloud layer that, within 5 NM of the flight path, is greater than 4,500 ft thick and has 

any part located between the 0 deg C and the -20 deg C levels;

 unless the cloud layer is a cirriform cloud that has never been associated with convective clouds, is 

located entirely at temperatures of -15 deg C or colder, and shows no evidence of containing liquid water (e.g., 

aircraft icing).

 Definitions: Associated, Cloud Layer, Flight Path, Nontransparent

 7. Smoke Plumes

 Do not launch if the flight path will carry the vehicle through any cumulus cloud that has developed from 

a smoke plume while the cloud is attached to the smoke plume, or for the first 60 minutes after the cumulus 

cloud is observed to have detached from the smoke plume.

 Note: Cumulus clouds that have formed above a fire but have been detached from the smoke plume for 

more than 60 minutes are considered CUMULUS CLOUDS and are covered in Criterion 2.

 Definitions: Flight Path

 8. Surface Electric Fields

 a) Do not launch for 15 minutes after the absolute value of any electric field measurement at the surface 

within 5 NM of the flight path has been greater than 1500 V/m.

 b) Do not launch for 15 minutes after the absolute value of any electric field measurement at the surface 

within 5 NM of the flight path has been greater than 1000 V/m unless:

 (1) All clouds within 10 NM of the flight path are transparent;

 -or-
Page 104 of 234

 (2) All nontransparent clouds within 10 NM of the flight path have cloud tops below the +5 deg C level 

and have not been part of convective clouds with cloud tops above the -10 deg C level within the last 3 hours.

 Notes:

 i) Electric field measurements at the surface are used to increase safety by detecting electric fields due to 

unforeseen or unrecognized hazards.

 ii) For confirmed failure of one or more field mill sensors, the countdown and launch may continue.

 Definitions: Cloud Top, Electric Field Measurement at the Surface, Flight Path, Nontransparent, 

Transparent, Within

 9. Definitions:

 a) Anvil: Stratiform or fibrous cloud produced by the upper level outflow or blow-off from 

thunderstorms or convective clouds.

 b) Associated: Used to denote that two or more clouds are causally related to the same weather 

disturbance or are physically connected. ASSOCIATED is not synonymous with occurring at the same time. 

An example of clouds that are NOT associated is air mass clouds formed by surface heating in the absence of 

organized lifting. Also, a cumulus cloud formed locally and a physically separated cirrus layer generated by a 

distant source are not associated, even if they occur over or near the launch site at the same time.

 Subsidiary Definition: Weather Disturbance

 c) Bright Band: An enhancement of radar reflectivity caused by frozen hydrometeors falling through the 

0 deg C level and beginning to melt.

 d) Cloud Edge: The visible cloud edge is preferred. If this is not possible, then the 10 dBZ radar 

reflectivity cloud edge is acceptable.

 e) Cloud Layer: A vertically continuous array of clouds, not necessarily of the same type, whose bases 

are approximately at the same level.

 f) Cloud Top: The visible cloud top is preferred. If this is not possible, then the 10 dBZ radar reflectivity 

cloud top is acceptable.

 g) Cumulonimbus Cloud: Any convective cloud with any part above the -20 deg C temperature level.

 h) Debris Cloud: Any cloud, except an anvil cloud, that has become detached from a parent 

cumulonimbus cloud or thunderstorm, or that results from the decay of a parent cumulonimbus cloud or 

thunderstorm.

 Subsidiary Definition: Cumulonimbus Cloud

 i) Electric Field Measurement at the Surface: The one-minute arithmetic average of the vertical electric 

field (Ez) at the ground measured by a ground based field mill. The polarity of the electric field is the same as 

that of the potential gradient; that is, the polarity of the field at the ground is the same as the dominant charge 

overhead.
Page 105 of 234

 Note: Electric field contours shall not be used for the electric field measurement at the surface.

 j) Flight Path: The planned flight path including its uncertainties ("error bounds").

 k) Moderate Precipitation: A precipitation rate of 0.1 inches/hr or a radar reflectivity factor of 30 dBZ.

 l) Nontransparent: Opposite of Transparent. Sky cover through which forms are blurred, indistinct, or 

obscured is nontransparent.

 Note: Nontransparency must be assessed for launch time. Sky cover through which forms are seen 

distinctly ONLY through breaks in the cloud cover is considered nontransparent. Clouds with a radar 

reflectivity of 10 dBZ or greater are also considered nontransparent.

 Subsidiary Definition: Transparent

 m) Optically Thin: Having a vertical optical thickness of unity or less at visible wavelengths.

 n) Precipitation: Detectable rain, snow, sleet, etc., at the ground, or virga, or a radar reflectivity greater 

than 18 dBZ.

 o) Transparent: Synonymous with optically thin. Sky cover is transparent if higher clouds, blue sky, 

stars, the disk of the sun, etc., can be distinctly seen from below, or if the sun casts distinct shadows of objects 

on the ground, or if terrain, buildings, lights on the ground, etc., can be distinctly seen from above.

 Note: Visible transparency is required. Transparency must be assessed for launch time. Sky cover 

through which forms are seen distinctly ONLY through breaks in the cloud cover is considered 

NONtransparent.

 Subsidiary Definitions: Nontransparent, Optically Thin

 p) Thunderstorm: Any convective cloud that produces lightning.

 q) Weather Disturbance: A weather system where dynamical processes destabilize the air on a scale 

larger than the individual clouds or cells. Examples of disturbances are fronts, troughs and squall lines.

 r) Within: Used as a function word to specify a margin in all directions (horizontal, vertical, and slant 

separation) between the cloud edge or top and the flight path. For example, "WITHIN 10 NM of a 

thunderstorm cloud" means that there must be a 10 NM margin between every part of a thunderstorm cloud 

and the flight path.

 Subsidiary Definitions: Cloud Edge, Cloud Top, Flight Path
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A1.10 Space Shuttle LLCC (2005)[LCN# 01166R01]

1.0 Weather Rules.

This section contains the weather conditions that are a constraint to launching the Space Shuttle Vehicle 

(SSV). The weather constraints stated in this section shall not be waived.

1.4 Natural and Triggered Lightning Constraints.

Notice: Any changes to this section will require coordination with the 45th Space Wing Range Safety Office 

(RSO).

Natural and Triggered Lightning LCC

The Launch Weather Team (LWT) must have clear and convincing evidence that the following hazard 

avoidance criteria are not violated.

Even when these criteria are not violated, if any other hazardous condition exists, the LWT will report the 

threat to the Launch Director (LD). The LD may Hold at any time based on the instability of the weather.

A. Lightning

1. Do not launch for 30 minutes after any type of lightning occurs in a thunderstorm if the flight path 

will carry the SSV within 10 Nautical Miles (NM) of that thunderstorm.

2. Do not launch for 30 minutes after any type of lightning occurs within 10 NM of the flight path 

unless:

a. The cloud that produced the lightning is not within 10 NM of flight path;

-andb. There is at least one working field mill within 5 NM of each such lightning flash;

-andc. The absolute values of all electric field measurements at the surface, within 5 NM of the 

flight path and at the mill(s) specified in subparagraph 1.4.A.2.b, have been less than 1000 

Volts/meter (V/m) for 15 minutes.

Notes:

i) Anvils are covered in section 1.4.C.

ii) If a cumulus cloud remains 30 minutes after the last lightning occurs in a thunderstorm, then section 1.4.B. 

applies.

Definitions: Anvil, Electric Field Measurement at the Surface, Flight Path, Thunderstorm, Within

B. Cumulus Clouds

1. Do not launch if the flight path will carry the SSV within 10 NM of any cumulus cloud with its 

cloud top higher than the -20 degrees Celsius (C) level.

2. Do not launch if the flight path will carry the SSV within 5 NM of any cumulus cloud with its cloud 

top higher than the -10 degrees C level.
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3. Do not launch if the flight path will carry the SSV through any cumulus cloud with its cloud top 

higher than the -5 degrees C level.

4. Do not launch if the flight path will carry the SSV through any cumulus cloud with its cloud top 

between the +5 degrees C and -5 degrees C levels unless:

a. The cloud is not producing precipitation;

- andb. The horizontal distance from the center of the cloud top to at least one working field mill is 

less than 2 NM; 

-andc. All electric field measurements at the surface within 5 NM of the flight path and at the 

mill(s) specified in subparagraph 1.4.B.4.b. above have been between -100 V/m and +500 

V/m for 15 minutes.

Note: Cumulus clouds in section 1.4.B. do not include altocumulus, cirrocumulus or stratocumulus.

Definitions: Cloud Top, Electric Field Measurement at the Surface, Flight Path, Precipitation, Within

C. Anvil Clouds

1. Attached Anvil Clouds

a. Do not launch if the flight path will carry the SSV through or within 10 NM of a 

nontransparent part of any attached anvil cloud for the first 30 minutes after the last lightning 

discharge in or from the parent cloud or anvil cloud.

b. Do not launch if the flight path will carry the SSV through or within 5 NM of a 

nontransparent part of any attached anvil cloud between 30 minutes and three hours after the 

last lightning discharge in or from the parent cloud or anvil cloud unless both of the following 

conditions are satisfied:

1) The portion of the attached anvil cloud within 5 NM of the flight path is located 

entirely at altitudes where the temperature is colder than 0 degrees C;

-and2) The VAHIRR is less than +33 Range Corrected Reflectivity (dBZ)-thousand 

feet(kft) (+10 dBZ-kilometers (km)) everywhere along the portion of the flight path 

where any part of the attached anvil cloud is within the specified volume.

c. Do not launch if the flight path will carry the SSV through a nontransparent part of any 

attached anvil cloud more than 3 hours after the last lightning discharge in or from the parent 

cloud or anvil cloud unless both of the following conditions are satisfied:
Page 108 of 234

1) The portion of the attached anvil cloud within 5 NM miles of the flight path is 

located entirely at altitudes where the temperature is colder than 0 degrees C;

-and2) The VAHIRR is less than +33 dBZ-kft (+10 dBZ-km) everywhere along the 

portion of the flight path where any part of the attached anvil cloud is within the 

specified volume.

2. Detached Anvil Clouds.

For the purposes of this section, detached anvil clouds are never considered debris clouds.

a. Do not launch if the flight path will carry the SSV through or within 10 NM of a 

nontransparent part of a detached anvil cloud for the first 30 minutes after the last lightning 

discharge in or from the parent cloud or anvil cloud before detachment or after the last 

lightning discharge in or from the detached anvil cloud after detachment.

b. Do not launch if the flight path will carry the SSV between 0 (zero) and 5 NM from a 

nontransparent part of a detached anvil cloud between 30 minutes and 3 hours after the time of 

the last lightning discharge in or from the parent cloud or anvil cloud before detachment or 

after the last lightning discharge in or from the detached anvil cloud after detachment unless 

subparagraph 1.4.C.2.b.1) or subparagraph 1.4.C.2.b.2) is satisfied:

1) This section is satisfied if all three of the following conditions are met:

a) There is at least one working field mill within 5 NM of the detached anvil 

cloud;

-andb) The absolute values of all electric field measurements at the surface within 

5 NM of the flight path and at each field mill specified in subparagraph 

1.4.C.2.b.1)a) have been less than 1000 V/m for 15 minutes;

-andc) The maximum radar return from any part of the detached anvil cloud within 

5 NM of the flight path has been less than 10 dBZ for 15 minutes.

2) This section is satisfied if both of the following conditions are met:

a) The portion of the detached anvil cloud within 5 NM of the flight path is 

located entirely at altitudes where the temperature is colder than 0 degrees C;

-andb) The VAHIRR is less than +33 dBZ-kft (+10 dBZ-km) everywhere along 

the portion of the flight path where any part of the detached anvil cloud is 

within the specified volume.
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c. Do not launch if the flight path will carry the SSV through a nontransparent part of a 

detached anvil cloud unless subparagraph 1.4.C.2.c.1) or subparagraph 1.4.C.2.c.2) is satisfied

1) This section is satisfied if both of the following conditions are met.

a) At least 4 hours have passed since the last lightning discharge in or from 

the detached anvil cloud;

-andb) At least 3 hours have passed since the time that the anvil cloud is observed 

to be detached from the parent cloud.

2) This section is satisfied if both of the following conditions are met.

a) The portion of the detached anvil cloud within 5 nautical miles of the flight 

path is located entirely at altitudes where the temperature is colder than 0 

degrees C;

-andb) The Volume-Averaged, Height-Integrated Radar Reflectivity (VAHIRR) is 

less than +33 dBZ-kft (+10 dBZ-km) everywhere along the portion of the 

flight path where any part of the detached anvil cloud is within the specified 

volume.

Note: Detached anvil clouds are never considered debris clouds, nor are they covered by section 1.4.D.

Definitions: Anvil; Cloud Base; Cloud Edge; Cloud Top; Debris Cloud; Electric Field Measurements at the 

Surface; Field Mill; Flight Path; Volume-Averaged, Height-Integrated Radar Reflectivity (VAHIRR); 

Nontransparent; Specified Volume; Transparent; Within

D. Debris Clouds

1. Do not launch if the flight path will carry the SSV through any nontransparent parts of a debris 

cloud during the 3 hour period defined below.

2. Do not launch if the flight path will carry the vehicle within 5 NM of any nontransparent parts of a 

debris cloud during the 3 hour period defined below, unless:

a. There is at least one working field mill within 5 NM of the debris cloud;

-andb. The absolute values of all electric field measurements at the surface within 5 NM of the 

flight path and at the mill(s) specified in section 1.4.D.2.a. have been less than 1000 V/m for 

15 minutes;

-and-
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c. The maximum radar return from any part of the debris cloud within 5 NM of the flight path 

has been less than 10 dBZ for 15 minutes.

The 3 hour period in subparagraphs 1.4.D.2.a. and 1.4.D.2.b. begins at the time when the debris cloud is 

observed to have detached from the parent cloud or when the debris cloud is observed to have formed from the 

decay of the parent cloud top below the altitude of the -10 degrees C level. The 3 hour period begins anew at 

the time of any lightning discharge that occurs in the debris cloud.

Definitions: Cloud Top, Debris Cloud, Electric Field Measurement at the Surface, Flight Path, Nontransparent, 

Within

E. Disturbed Weather

Do not launch if the flight path will carry the vehicle through any nontransparent clouds that are associated 

with a weather disturbance having clouds that extend to altitudes at or above the 0 degree C level and contain 

moderate or greater precipitation or a radar bright band or other evidence of melting precipitation within 5 NM 

of the flight path.

Definitions: Associated, Flight Path, Moderate Precipitation, Nontransparent, Weather Disturbance, Within

F. Thick Cloud Layers

Do not launch if the flight path will carry the SSV through nontransparent parts of a cloud layer that is:

1. Greater than 4,500 foot thick and any part of the cloud layer along flight path is located between the 

0 degrees C and the -20 degrees C levels;

-or2. Connected to a cloud layer that, within 5 NM of the flight path, is greater than 4,500 foot thick and 

has any part located between the 0 degrees C and the -20 degrees C levels unless the cloud layer is a 

cirriform cloud that has never been associated with convective clouds, is located entirely at 

temperatures of -15 degrees C or colder, and shows no evidence of containing liquid water (e.g., 

aircraft icing).

Definitions: Associated, Cloud Layer, Flight Path, Nontransparent

G. Smoke Plumes

Do not launch if the flight path will carry the SSV through any cumulus cloud that has developed from a 

smoke plume while the cloud is attached to the smoke plume, or for the first 60 minutes after the cumulus 

cloud is observed to have detached from the smoke plume.

Note: Cumulus clouds that have formed above a fire but have been detached from the smoke plume for more 

than 60 minutes are considered cumulus clouds and are covered in section 1.4.B.

Definitions: Flight Path

H. Surface Electric Fields

1. Do not launch for 15 minutes after the absolute value of any electric field measurement at the 

surface within 5 NM of the flight path has been greater than 1500 V/m.
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2. Do not launch for 15 minutes after the absolute value of any electric field measurement at the 

surface within 5 NM of the flight path has been greater than 1000 V/m unless:

a. All clouds within 10 NM of the flight path are transparent;

-orAll nontransparent clouds within 10 NM of the flight path have cloud tops below the +5 

degrees C level and have not been part of convective clouds with cloud tops above the -10 

degrees C level within the last 3 hours.

Notes:

i) Electric field measurements at the surface are used to increase safety by detecting electric fields due to 

unforeseen or unrecognized hazards.

ii) For confirmed failure of one or more field mill sensors, the countdown and launch may continue.

Definitions: Cloud Top, Electric Field Measurement at the Surface, Flight Path, Nontransparent, Transparent, 

Within

I. Definitions:

1. Anvil: Stratiform or fibrous cloud produced by the upper level outflow or blow-off from thunderstorms or 

convective clouds.

2. Associated: Used to denote that two or more clouds are causally related to the same weather disturbance or 

are physically connected. Associated is not synonymous with occurring at the same time. An example of 

clouds that are not associated is air mass clouds formed by surface heating in the absence of organized lifting. 

Also, a cumulus cloud formed locally and a physically separated cirrus layer generated by a distant source, are 

not associated, even if they occur over or near the launch site at the same time.

Subsidiary Definition: Weather Disturbance

3. Bright Band: An enhancement of radar reflectivity caused by frozen hydrometeors falling through the 0 

degrees C level and beginning to melt.

4. Cloud Base: The visible cloud base is preferred. If this is not possible, then the 0 (zero) dBZ radarreflectivity cloud base is acceptable.

5. Cloud Edge: The visible cloud edge is preferred. If this is not possible, then the 0 (zero) dBZ radar 

reflectivity cloud edge is acceptable.

6. Cloud Layer: A vertically continuous array of clouds, not necessarily of the same type, whose bases are 

approximately at the same level.

7. Cloud Top: The visible cloud top is preferred. If this is not possible, then the 0 (zero) dBZ radar reflectivity 

cloud top is acceptable.

8. Cumulonimbus Cloud: Any convective cloud with any part above the –20 degrees C temperature level.

9. Debris Cloud: Any cloud, except an anvil cloud, that has become detached from a parent cumulonimbus 

cloud or thunderstorm, or that results from the decay of a parent cumulonimbus cloud or thunderstorm.

Subsidiary Definition: Cumulonimbus Cloud
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10. Electric Field Measurement at the Surface: The one-minute arithmetic average of the vertical electric field 

(Ez) at the ground measured by a ground based field mill. The polarity of the electric field is the same as that 

of the potential gradient; that is, the polarity of the field at the ground is the same as the dominant charge 

overhead. Note: Electric field contours shall not be used for the electric field measurement at the surface.

Subsidiary Definition: Field Mill

11. Field Mill: A specific class of electric-field sensor that uses a moving, grounded conductor to induce a 

time-varying electric charge on one or more sensing elements in proportion to the ambient electrostatic field

12. Flight Path: The planned flight path including its uncertainties (“error bounds”).

13. Moderate Precipitation: A precipitation rate of 0.1 inches/hour or a radar reflectivity factor of 30 dBZ.

14. Nontransparent: Sky cover through which forms are blurred, indistinct, or obscured is nontransparent. 

Note: Nontransparency must be assessed for launch time. Sky cover through which forms are seen distinctly 

only through breaks in the cloud cover is considered nontransparent. Clouds with a radar reflectivity of 0 

(zero) dBZ or greater, are also considered nontransparent.

Subsidiary Definition: Transparent

15. Precipitation: Detectable rain, snow, sleet, hail or graupel at the ground, or virga, or a radar reflectivity 

greater than 18 dBZ.

16. Specified Volume: is the volume bounded in the horizontal by vertical, plane, perpendicular sides located 

5.5 km (3 NM) north, east, south, and west of the point on the flight track, on the bottom by the 0 degree C 

level, and on the top by the upper extent of all cloud.

17. Transparent: Sky cover is transparent if higher clouds, blue sky, stars, etc., can be distinctly seen from 

below, or if terrain, buildings, lights on the ground, etc., can be distinctly seen from above.

Note: Visible transparency is required. Transparency must be assessed for launch time. Sky cover through 

which forms are seen distinctly only through breaks in the cloud cover is considered nontransparent.

Subsidiary Definitions: Nontransparent

18. Thunderstorm: Any convective cloud that produces lightning.

19. Volume-Averaged, Height–Integrated Radar Reflectivity (VAHIRR): Product of the Volume-Averaged 

Radar Reflectivity (VARR) and the average cloud thickness within a specified volume relative to a point along 

the flight track (units of dBZ-km) where The VARR is the arithmetic average (in dBZ) of the cloud radar 

reflectivity within the Specified Volume. Normally, a radar processor will report reflectivity values 

interpolated onto a regular, three-dimensional array of grid points. Any such grid point within the specified 

volume is included in the average if and only if it has a radar reflectivity equal to or greater than 0 dBZ.

-and whereThe average cloud thickness is the altitude difference (in kilometers) between the average top and the average 

base of all clouds within the specified volume. The cloud base to be averaged is the higher of (1) the 0 degree 

C level and (2) the lowest extent (in altitude) of all cloud radar reflectivities 0 dBZ or greater. Similarly, the 

cloud top to be averaged is the highest extent (in altitude) of all cloud radar reflectivities 0 dBZ or greater. 

Given the grid-point representation of a typical radar processor, allowance must be made for the vertical 

separation of grid points in computing cloud thickness: The cloud base at any horizontal position shall be 

taken as the altitude of the corresponding base grid point minus half of the grid-point vertical separation. 
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Similarly, the cloud top at that horizontal position shall be taken as the altitude of the corresponding top grid 

point plus half of this vertical separation. Thus, a cloud represented by only a single grid point having a radar 

reflectivity equal to or greater than 0 dBZ within the specified volume would have an average cloud thickness 

equal to the vertical grid-point separation in its vicinity.

Note: The VAHIRR measurement must be made in the absence of significant attenuation by intervening 

storms or by water or ice on the radome itself. The VAHIRR measurement is invalid at any point on the flight 

track that is within 20 km of any radar reflectivity of 35 dBZ or greater at altitudes of 4 kilometers above mean 

sea level or greater, and at any point that is within 20 km of any type of lightning that has occurred in the 

previous 5 minutes. The specified volume must not contain any portion of the cone of silence above the radar, 

nor any portion of any sectors that may have been blocked out for payload-safety reasons. The individual gridpoint reflectivities used to determine either the VARR or the average cloud thickness must be meteorological 

reflectivities.

Subsidiary Definition: Specified Volume

Note: See below “Interim Instructions for Implementation of VAHIRR”

20. Weather Disturbance: A weather system where dynamical processes destabilize the air on a scale larger 

than the individual clouds or cells. Examples of disturbances are fronts, troughs and squall lines.

21. Within: Used as a function word to specify a margin in all directions (horizontal, vertical, and slant 

separation) between the cloud edge, base, or top and the flight path. For example, "Within 10 NM of a 

thunderstorm cloud" means that there must be a 10 NM margin between every part of a thunderstorm cloud 

and the flight path.

Subsidiary Definitions: Cloud Base, Cloud Edge, Cloud Top, Flight Path

J. Interim Instructions for Implementation of VAHIRR

The VAHIRR quantity referred to in section 1.4.C. and the definitions require computation of both a volume 

average reflectivity and an average cloud thickness. These quantities are then multiplied to produce the 

VAHIRR. Neither of these quantities is available yet as a product on the WSR-88D and WSR-74C radar 

systems used to support launch operations. This instruction provides a methodology for evaluating VAHIRR 

criteria with currently available radar products. The methodology provides a result that is more conservative 

than a direct VAHIRR computation, but it should still permit the launch users to achieve much of the benefit 

of the VAHIRR feature.

1. Part I. Determination of average cloud thickness. The definition of VAHIRR requires determination of the 

average cloud top and the average cloud base above the height of the 0 °C isotherm within a square having 

sides 5.5 km (3 NM) north, east, south, and west of the ground projection of each point in the flight track. 

Average cloud thickness is defined as the difference of these two numbers. If the average cloud thickness 

cannot be determined at each point on the flight track, the maximum thickness within 5.5 km (3 NM) of the 

flight track may be used.

To determine the average cloud top height, the launch weather team may use any existing radar product that 

gives the height of the 0 dBZ cloud top, including "maximum height of reflectivity" and cross section 

products. If the average height cannot be determined, the maximum height of the 0 dBZ reflectivity may be 

used. If the maximum height cannot be determined, use 18 km (60 kft) for the average cloud top.

The average height of the cloud base should be derived from radar data. It is the average of the higher of (a) 

the bottom of the portion of the cloud producing a radar reflectivity of 0 dBZ or greater or (b) the height of the 

0 °C isotherm where the 0 dBZ reflectivity extends below that level. If the average height of the cloud base 

cannot be determined, use the higher of (a) the height of the 0 degree C isotherm or (b) the lowest portion of 
Page 114 of 234

the cloud producing a radar reflectivity of 0 dBZ or greater anywhere within each 5.5 km (3 n. mi.) square 

defined above.

2. Part II. Volume Averaged Radar Reflectivity (VARR). There is no operationally feasible way to use 

existing radar products to compute a volume average reflectivity. A conservative substitute is the maximum 

reflectivity since the volume average will always be smaller than the maximum. The WSR-88D has a "User 

Selectable Layer Composite Reflectivity (URL)" product and the WSR-74C has a "Max" product with user 

selectable base and top. The Launch Weather Team should configure these products with the bottom of the 

layer at the height of the 0 degree C isotherm and the top above the height of the highest radar beam within 7.8 

km (4.2 n. mi.) of the ground-projected flight track in the scan strategy being used. The WSR-88D product will 

have to be configured at the Radar Product Generator (RPG) and included in the product scheduler for the 

Principal User Processor (PUP) used by the launch weather team.

3. Part III. Evaluating the constraint. The VAHIRR constraint is satisfied for a point on the flight track if the 

"URL" or "Max" radar product (see Part II above) everywhere within the corresponding square (defined 

above) is less than 10 dBZ-km divided by the average cloud thickness in km within the same square (see Part I 

above). (In English units, this threshold would become 33 dBZ-kft divided by the average cloud thickness in 

kft.) This constraint must be satisfied for every point on the flight track.
Page 115 of 234

A1.11 Current Space Shuttle LLCC (adopted 2009)[LCN# WEA-1]

1.4 Natural and Triggered Lightning Constraints.

Notice: The lightning definitions, explanations and examples are a critical part of the lightning constraints and 

must be used when evaluating all lightning constraints in this section.

Notice: Any changes to this section will require coordination with the 45th Space Wing Range Safety Office 

(RSO).

The Launch Weather Team (LWT) must have clear and convincing evidence that the following hazard 

avoidance criteria are not violated. Even when these criteria are not violated, if any other hazardous condition 

exists, the LWT will report the threat to the Launch Director (LD). The LD may Hold at any time based on the 

instability of the weather.

A. Surface Electric Fields

1. Do not launch for 15 minutes after the absolute value of any “electric field measurement” less 

than or equal to 5 Nautical Miles (NM) from the “flight path” has been greater than or equal to 1500 

Volts/meter (V/m).

2. Do not launch for 15 minutes after the absolute value of any “electric field measurement” less 

than or equal to 5 NM of the “flight path” has been greater than or equal to 1000 V/m unless 

subparagraph 1.4.A.2.a. or subparagraph 1.4.2.b. is satisfied:

a. All “clouds” less than or equal to 10 NM from the “flight path” are “transparent”;

-orb. All "clouds" less than or equal to 10 NM from the "flight path" have "cloud tops" at 

altitudes where the temperature is warmer than +5 degrees Celsius and have not been part of 

convective "clouds" with "cloud tops" at altitudes where the temperature is colder than or 

equal to −10 degrees Celsius during the last 3 hours.

B. Lightning

1. Do not launch for 30 minutes after any type of lightning occurs in a “thunderstorm” if the 

“flight path” will carry the SSV less than or equal to 10 NM from the “thunderstorm”. An attached 

“anvil cloud” is not considered part of its parent “thunderstorm” but is covered instead by the Attached 

Anvil Cloud Rule.

2. Do not launch for 30 minutes after any type of lightning occurs less than or equal to 10 NM 

from the “flight path” unless all three of the following conditions are satisfied:

a. The “cloud” that produced the lightning is greater than 10 NM from the “flight path”;

-andb. There is at least one working “field mill” less than 5 NM from each such lightning 

discharge;

-and-
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c. The absolute values of all “electric field measurements” less than or equal to 5 NM 

from the “flight path”, and at each “field mill” specified in subparagraph 1.4.B.2.b., have been 

less than 1000 V/m for 15 minutes or longer.

C. Cumulus Clouds

For the purposes of this section, “cumulus 'clouds'” do not include cirrocumulus, altocumulus, or 

stratocumulus "clouds". An attached "anvil cloud" is never considered part of its parent cumulus "cloud," but 

is covered instead by subparagraph 1.4.D.1., Attached "Anvil Clouds". Subparagraph 1.4.D.2., Detached 

"Anvil Clouds" applies to any detached "anvil cloud". Section 1.4.E, "Debris Clouds" applies to "debris 

clouds".

1. Do not launch if the “flight path” will carry the SSV less than or equal to 10 NM from any 

cumulus “cloud” that has a “cloud top” at an altitude where the temperature is colder than or equal to -

20 degrees Celsius.

2. Do not launch if the “flight path” will carry the SSV less than or equal to 5 NM from any 

cumulus “cloud” that has a “cloud top” at an altitude where the temperature is colder than or equal to -

10 degrees Celsius.

3. Do not launch if the “flight path” will carry the SSV through any cumulus “cloud” with its 

“cloud top” at an altitude where the temperature is colder than or equal to -5 degrees Celsius.

4. Do not launch if the “flight path” will carry the SSV through any cumulus “cloud” that has a 

“cloud top” at an altitude where the temperature lies in the range from warmer than -5 degrees 

Celsius to colder than or equal to +5 degrees Celsius unless all three of the following conditions 

are satisfied:

a. The “cloud” is not producing “precipitation”;

-andb. The horizontal distance from the center of the “cloud top” to at least one working 

“field mill” is less than 2 NM;

-andc. All “electric field measurements” less than or equal to 5 NM from the “flight path” 

and at each “field mill” specified in subparagraph 1.4.B.4.b. above have been greater than -

100 V/m, but less than +500 V/m for 15 minutes or longer.

D. Anvil Clouds

1. Attached “Anvil Clouds”

For the purpose of this section, if there has never been lightning in or from the parent “cloud” or “anvil cloud”, 

subparagraphs 1.4.D.1.a and 1.4.D.1.b. shall be considered satisfied, but subparagraph 1.4.D.1.c. shall still 

apply.

a. Do not launch if the “flight path” will carry the SSV less than 10, but greater than 5 

NM from any attached “anvil cloud” for the first 30 minutes after the last lightning discharge 

in or from the parent “cloud” or “anvil cloud” unless the portion of the attached “anvil cloud” 
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less than or equal to 10 NM from the “flight path” is located entirely at altitudes where the 

temperature is colder than 0 degrees Celsius.

b. Do not launch if the “flight path” will carry the SSV less than or equal to 5, but 

greater than 3 NM from any attached “anvil cloud” for the first 3 hours after the last lightning 

discharge in or from the parent “cloud” or “anvil cloud” unless the portion of the attached 

“anvil cloud” less than or equal to 5 NM from the “flight path” is located entirely at altitudes 

where the temperature is colder than 0 degrees Celsius.

c. Do not launch if the “flight path” will carry the SSV less than or equal to 3 NM from 

any attached “anvil cloud” unless all three of the following conditions are satisfied:

1) The portion of the attached “anvil cloud” less than or equal to 5 NM from the 

“flight path” is located entirely at altitudes where the temperature is colder than 0 

degrees Celsius;

-and2) The Volume Averaged Height Integrated Radar Reflectivity (“VAHIRR”) is 

less than +10 dBZ-km (+33 dBZ-kft) at every point less than or equal to 1 NM from 

the “flight path”;

-and3) All of the “VAHIRR application criteria” are satisfied.

2. Detached “Anvil Clouds”.

For the purposes of this section, detached “anvil clouds” are never considered “debris clouds”.

For the purpose of this section, if there has never been lightning in or from the parent “cloud” or “anvil cloud”, 

subparagraphs 1.4.D.2.a, 1.4.D.2.b, 1.4.D.2.c and 1.4.D.2.d.1.a shall be considered satisfied, but subparagraphs 

1.4.D.2.d.1.b and 1.4.D.2.d.2 shall still apply.

a. Do not launch if the “flight path” will carry the SSV less than or equal to 10, but 

greater than 3 NM from a detached “anvil cloud” for the first 30 minutes after the last 

lightning discharge in or from the parent “cloud” or “anvil cloud” before detachment or after 

the last lightning discharge in or from the detached “anvil cloud” after detachment unless the 

portion of the detached “anvil cloud” less than or equal to 10 NM from the “flight path” is 

located entirely at altitudes where the temperature is colder than 0 degree Celsius.”

b. Do not launch if the “flight path” will carry the SSV between 0 (zero) and 3 NM 

inclusive, from a detached “anvil cloud” for the first 30 minutes after the time of the last 

lightning discharge in or from the parent “cloud” or “anvil cloud” before detachment or after 

the last lighting discharge in or from the detached “anvil cloud” after detachment unless all 

three of the following conditions are met:

1) The portion of the detached “anvil cloud” less than or equal to 5 NM from the 

“flight path” is located entirely at altitudes where the temperature is colder than 0 

degrees Celsius;
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-and2) The “VAHIRR” is less than +33 dBZ-kft (+10 dBZ-km) at every point less 

than or equal to 1 NM from the “flight path”;

-and3) All of the “VAHIRR application criteria” are satisfied.

c. Do not launch if the “flight path” will carry the SSV between 0 (zero) and 3 NM, 

inclusive, from a detached “anvil cloud” less than or equal to 3 hours, but greater than 30 

minutes, after the time of the last lightning discharge in or from the parent “cloud” or “anvil 

cloud” before detachment or after the last lighting discharge in or from the detached “anvil 

cloud” after detachment unless subparagraph 1.4.D.2.c.1) or subparagraph 1.4.D.2.c.2) is 

satisfied:

1) This section is satisfied if all three of the following conditions are met:

a) There is at least one working “field mill” less than 5 NM from the 

detached “anvil cloud”;

-andb) The absolute values of all “electric field measurements” less than or 

equal to 5 NM from the “flight path” and at each “field mill” specified in 

subparagraph 1.4.D.2.c.1)a) have been less than 1000 V/m for 15 minutes;

-andc) The maximum radar reflectivity from any part of the detached “anvil 

cloud” less than or equal to 5 NM from the “flight path” has been less than 

+10 dBZ for 15 minutes.

2) This section is satisfied if all three of the following conditions are met:

a) The portion of the detached “anvil cloud” less than or equal to 5 NM 

from the “flight path” is located entirely at altitudes where the temperature is 

colder than 0 degrees Celsius;

-andb) The “VAHIRR” is less than +33 dBZ-kft (+10 dBZ-km) at every 

point less than or equal to 1 NM from the “flight path”;

-andc) All of the “VAHIRR application criteria” are satisfied.

d. Do not launch if the “flight path” will carry the SSV through a detached “anvil cloud” 

unless subparagraph 1.4.D.2.d.1) or subparagraph 1.4.D.2.d.2) is satisfied:
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1) This section is satisfied if both of the following conditions are met:

a) At least 4 hours have passed since the last lightning discharge in or 

from the detached “anvil cloud”;

-andb) At least 3 hours have passed since the time that the “anvil cloud” is 

observed to be detached from the parent “cloud”.

2) This section is satisfied if all three of the following conditions are met:

a) The portion of the detached “anvil cloud” less than or equal to 5 NM 

from the “flight path” is located entirely at altitudes where the temperature is 

colder than 0 degrees Celsius;

-andb) The “VAHIRR” is less than +33 dBZ-kft (+10 dBZ-km) everywhere 

along the “flight path”; 

-andc) All of the “VAHIRR application criteria” are satisfied.

E. Debris Clouds 

The 3-hour time period defined in this section must begin again at the time of any lightning discharge in or 

from the “debris cloud”.

1. Do not launch if the “flight path” will carry the SSV between 0 and 3 NM, inclusive, from a 

debris cloud for 3 hours after the debris cloud is observed to be detached from the parent cloud or after 

the debris cloud is observed to have formed from the collapse of the parent cloud top to an altitude 

where the temperature is warmer than -10 degrees Celsius unless subparagraph 1.4.E.1.a. or 

subparagraph 1.4.E.1.b. is satisfied:

a. This section is satisfied if all three of the following conditions are met:

1) There is at least one working “field mill” less than 5 NM from the debris cloud;

-and2) The absolute values of all “electric field measurements” less than or equal to 5 NM 

from the “flight path” and at each “field mill(s)” employed by subparagraph 

1.4.E.1.a.1) of this section has been less than 1000 V/m for 15 minutes or longer;

-and3) The maximum radar reflectivity from any part of the debris cloud less than or equal 

to 5 NM of the “flight path” has been less than +10 dBZ for 15 minutes or longer.
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b. This section is satisfied if all three of the following conditions are met:

1) The portion of the debris cloud less than or equal to 5 NM from the “flight path” is 

located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

-and2) The “VAHIRR” is less than +33 dBZ-kft (+10 dBZ-km) at every point less than or 

equal to 1 NM from the “flight path”;

-and3) All of the “VAHIRR application criteria” are satisfied.

2. Do not launch if the “flight path” will carry the SSV through any “debris cloud” during the 3-

hour period defined in Section 1.4.E.1, unless all three of the following conditions are met:

a. The portion of the “debris cloud” less than or equal to 5 NM from the “flight path” is 

located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

-andb. The “VAHIRR” is less than +33 dBZ-kft (+10 dBZ-km) everywhere along the “flight 

path”;

-andc. All of the “VAHIRR application criteria” are satisfied.

F. Disturbed Weather

1. Do not launch if the “flight path” will carry the SSV through a “cloud” associated with 

“disturbed weather” that has “clouds” with “cloud tops” at altitudes where the temperature is colder 

than or equal to 0 degrees Celsius and that contains, less than or equal to 5 NM from the “flight path”, 

either:

a. “Moderate precipitation” or greater;

-orb. Evidence of melting “precipitation” such as a “radar bright” band. 

G. Thick Cloud Layers

For the purpose of this section neither attached nor detached “anvil clouds” are considered “thick cloud 

layers”.

1. Do not launch if the “flight path” will carry the SSV through a “cloud layer” that is either:
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a. Greater than or equal to 4,500 feet thick and any part of the “cloud layer” along “flight 

path” is located at an altitude where the temperature is between 0 degrees Celsius and -20 

degrees Celsius, inclusive;

-orb. Connected to a “cloud layer” that, less than or equal to 5 NM from the “flight path”, is 

greater than or equal to 4,500 feet thick and has any part located at an altitude where the 

temperature is between 0 degrees Celsius and -20 degrees Celsius, inclusive.

2. A launch operator need not apply the lightning commit criteria in subparagraph 1.4.G.1.a. and 

subparagraph 1.4.G.1.b. of this section if the “thick cloud layer” is a cirriform “cloud layer” that has 

never been “associated” with convective “clouds”, is entirely at altitudes where the temperature is 

colder than or equal to -15 degrees Celsius and shows no evidence of containing liquid water.

H. Smoke Plumes

1. Do not launch if the “flight path” will carry the SSV through any cumulus “cloud” that has 

developed from a smoke plume while the “cloud” is attached to the smoke plume, or for the first 60 

minutes after the cumulus “cloud” is observed to be detached from the smoke plume.

2. Section 1.4.C. Cumulus “Clouds” applies to cumulus “clouds” that have formed above a fire 

but have been detached from the smoke plume for more than 60 minutes.

I. Definitions, Explanations and Examples:

For the purpose of the Natural and Triggered Lightning LCC, distance from an electric "field mill" is measured 

differently than distance from any other object or measurement point: Distance between a "radar reflectivity" 

or "VAHIRR" measurement point and any object or the "flight path" is the SHORTEST SEPARATION 

(horizontal, vertical, or slant range) between that point and the NEAREST PART of the object or "flight path". 

Similarly, distance between the "flight path" and any object is the SHORTEST SEPARATION between any 

point on the "flight path" the NEAREST PART of that object. For example, "every point less than or equal to 1 

NM from the 'flight path'" [see subparagraph 1.4.D.1.c.2) Attached Anvil Clouds] means that the "VAHIRR" 

threshold must be satisfied at every point throughout the entire volume defined by a 1 NM radius from every 

point on the "flight path". In contrast, distance between a "field mill" or an "electric field measurement" and 

any object or the "flight path" is always measured HORIZONTALLY between that mill or measurement point 

and the nearest part of the VERTICAL PROJECTION of the object or "flight path" onto the surface of Earth. 

For example, "from the center of the 'cloud top' to at least one working 'field mill'" [see subparagraph 

1.4.C.4.b. Cumulus "Clouds"] means that the HORIZONTAL distance between the "field mill" and a point on 

the surface directly beneath the center of the "cloud top" must be less than 2 NM.

1. Anvil Cloud: Stratiform or fibrous “cloud” produced by the upper level outflow or blow-off 

from “thunderstorms” or “convective clouds” having tops at altitudes where the temperature is colder 

than or equal to -10 degrees Celsius.

2. Associated: When two or more "clouds" are causally related to the same "disturbed weather" 

system or are physically connected. "Clouds" occurring at the same time are not necessarily 

"associated". A cumulus "cloud" formed locally and a cirrus layer that is physically separated from 

that cumulus "cloud" and that is generated by a distant source are not "associated," even if they occur 

over or near the launch point at the same time.
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3. Average cloud thickness is the altitude difference (in kilometers, km hereafter) between the 

average top and the average base of all “clouds” in the "specified volume." The cloud base to be 

averaged is the higher of (1) the 0 degree Celsius level and (2) the lowest extent (in altitude) of all 

"radar reflectivity" measurements of 0 dBZ or greater. Similarly, the cloud top to be averaged is the 

highest extent (in altitude) of all "radar reflectivity" measurements of 0 dBZ or greater. Given the gridpoint representation of a typical radar processor, allowance must be made for the vertical separation of 

grid points in computing "average cloud thickness": The cloud base at any horizontal position shall be 

taken as the altitude of the corresponding base grid point minus half of the grid-point vertical 

separation. Similarly, the cloud top at that horizontal position shall be taken as the altitude of the 

corresponding top grid point plus half of this vertical separation. Thus, a cloud represented by only a 

single grid point having a "radar reflectivity" equal to or greater than 0 dBZ in the "specified volume" 

would have an "average cloud thickness" equal to the vertical grid-point separation in its vicinity.

4. Bright Band: An enhancement of radar reflectivity caused by frozen hydrometeors falling and 

beginning to melt at any altitude where the temperature is 0 degrees Celsius or warmer.

5. Cloud: A visible mass of suspended water droplets or ice crystals. The "cloud" is considered 

to be the entire volume enclosed by the visible, "nontransparent cloud" boundary as seen by an 

observer, or, in the absence of a visual observation, by the 0 dBZ "radar reflectivity" boundary. A 

visual evaluation of transparency is preferred whenever possible.

Distance from the "cloud" to a point in question refers to the separation between the point and the 

nearest part of that "cloud." Specifically, the wording, "less than or equal to 10 NM from any cumulus 

'cloud'" means that the "flight path" must not penetrate either the INTERIOR of the "cloud" itself or 

the volume between 0 and 10 NM, inclusive, OUTSIDE the "cloud" boundary [for example, see 

Section 1.4.C., Cumulus "Clouds"]. On the other hand, "between 0 and 3 NM, inclusive, from" refers 

ONLY to the volume at a distance that is greater than or equal to 0, but less than or equal to 3, NM 

OUTSIDE the "cloud" boundary, specifically omitting the interior of the "cloud" itself [for example, 

see Section 1.4.E, "Debris Clouds"].

6. Cloud Layer: A vertically continuous array of clouds, not necessarily of the same type, whose 

bases are approximately at the same level.

7. Cloud Top: The visible top of the cloud, or, in the absence of a visual observation, the 0 dBZ 

radar top. A visual evaluation of "cloud top" is preferred whenever possible.

8. Cone of Silence: The volume in an inverted circular cone centered on the radar that is 

generated by all elevation angles greater than the maximum elevation angle used in the radar scan 

strategy. For the purpose of "VAHIRR" calculation this volume is capped by the observed maximum 

"cloud top" height, the observed tropopause height, or an altitude of 20 km (66 kft), whichever is 

lowest.

9. Cumulonimbus Cloud: Any convective “cloud” with any part at an altitude where the 

temperature is colder than –20 degrees Celsius.

10. Debris Cloud: Any “cloud”, except an “anvil cloud”, that has become detached from a parent 

“cumulonimbus cloud” or “thunderstorm”, or that results from the decay of a parent “cumulonimbus 

cloud” or “thunderstorm”.
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11. Disturbed Weather: A weather system where dynamical processes destabilize the air on a 

scale larger than the individual “clouds” or cells. Examples of disturbances are fronts, troughs and 

squall lines.

12. Electric Field Measurement at the Surface: The one-minute arithmetic average of the vertical 

electric field (Ez) at the surface of Earth, measured by a ground-based "field mill". The polarity of the 

electric field is the same as that of the potential gradient; that is, the polarity of the field at Earth's 

surface is the same as the dominant charge overhead. Do not use interpolated electric field contours for 

purposes of this appendix. An "'electric field measurement' less than or equal to 5 NM from the 'flight 

path'" [e.g., Section 1.4.A. Surface Electric Fields] is not applicable if the altitude of the “flight path” 

everywhere above the 5 NM circle around the "field mill" in question is greater than 20 km (66 kft).

13. Field Mill: A specific class of electric-field sensor that uses a moving, grounded conductor to 

induce a time-varying electric charge on one or more sensing elements in proportion to the ambient 

electrostatic field.

14. Flight Path: The planned nominal flight trajectory, including its vertical and horizontal 

uncertainties specified by the three-sigma guidance and performance deviations.

15. Moderate Precipitation: A precipitation rate of 0.1 inches/hour or a radar reflectivity factor of 

30 dBZ.

16. Nontransparent: "Cloud" cover is "nontransparent" if one or more of the following conditions 

is present:

(a) Objects above, including higher "clouds", blue sky, and stars, are blurred, indistinct, or 

obscured as viewed from below; or objects below, including terrain, buildings, and lights on 

the ground, are blurred, indistinct, or obscured as viewed from above; when looking through 

the "cloud" cover at visible wavelengths (the sun and moon may not be used to evaluate 

transparency);

(b) Such objects are seen distinctly only through breaks in the "cloud" cover; or

(c) The "cloud" cover has a "radar reflectivity" factor of 0 dBZ or greater.

17. Precipitation: Detectable rain, snow, hail, graupel, or sleet at the ground; virga; or a "radar 

reflectivity" factor greater than 18 dBZ at any altitude above the ground.

18. Radar Reflectivity: The radar return from hydrometeors, in dBZ, measured by a 

meteorological radar operating at a wavelength greater than or equal to 5 cm. A "radar reflectivity" 

measurement is valid only in the absence of significant attenuation by intervening "precipitation" or by 

water or ice on the radome.

19. Specified Volume: The volume bounded in the horizontal by vertical planes with 

perpendicular sides located 5.5 km (3 NM) north, east, south, and west of the point at which 

"VAHIRR" is being computed. The volume is bounded on the bottom at the altitude where the 

temperature is 0 degrees Celsius, and on the top by a fixed altitude of 20 km (66 kft).

20. Thick Cloud Layer: One or more "cloud layers" whose combined vertical extent from the base 

of the bottom layer to the "cloud top" of the uppermost layer exceeds a thickness of 4,500 feet. "Cloud 

layers" are combined with neighboring layers for determining total thickness only when they are 

physically connected by vertically continuous "clouds", as, for example, when towering "clouds" in 

one layer contact or merge with "clouds" in a layer (or layers) above.
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21. Thunderstorm: Any convective cloud that produces lightning.

22. Transparent: Any "cloud" that is not "nontransparent" is "transparent".

23. (reserved)

24. (reserved)

25. Volume-Averaged, Height–Integrated Radar Reflectivity (VAHIRR): The product of the 

"volume-averaged radar reflectivity" and the "average cloud thickness" in a "specified volume" 

surrounding any point at which "VAHIRR" is being computed (units of dBZ-km). The "specified 

volume" must not contain any portion of the "cone of silence" above the radar, nor any portion of any 

sectors that may have been blocked out for payload-safety reasons.

26. VAHIRR Application Criteria: The individual grid-point reflectivity measurements used to 

determine either the "volume-averaged radar reflectivity" or the "average cloud thickness" must be 

meteorological "radar reflectivity" measurements. For "VAHIRR"-evaluation points along the "flight 

path" itself (not those at a prescribed distance away from the "flight path"), the "volume-averaged, 

height-integrated radar reflectivity" is not applicable at any point that is less than or equal to 10 NM 

from any "radar reflectivity" of 35 dBZ or greater at altitudes of 4 km (13 kft) or greater above mean 

sea level, nor is it applicable at any point that is less than or equal to 10 NM from any type of lightning 

that has occurred in the previous 5 minutes.

27. Volume-Averaged Radar Reflectivity: the arithmetic average (in dBZ) of the "radar 

reflectivity" in the "specified volume." Normally, a radar processor will report reflectivity values 

interpolated onto a regular, three-dimensional array of grid points. Any such grid point in the 

"specified volume" is included in the average if and only if it has a "radar reflectivity" equal to or 

greater than 0 dBZ. If fewer than 10% of the grid points in the "specified volume" have "radar 

reflectivity" measurements equal to or greater than 0 dBZ, then the "volume-averaged radar 

reflectivity" is either the maximum "radar reflectivity" (in dBZ) in the "specified volume," or 0 dBZ, 

whichever is greater.

J. Interim Instructions for Implementation of VAHIRR

The “VAHIRR” quantity referred to in Section 1.4.C. and the definitions require computation of both a 

volume average reflectivity and an average cloud thickness. These quantities are then multiplied to produce the 

“VAHIRR”. Neither of these quantities is available yet as a product on the WSR-88D and WSR-74C radar 

systems used to support launch operations. This instruction provides a methodology for evaluating “VAHIRR” 

criteria with currently available radar products. The methodology provides a result that is more conservative 

than a direct “VAHIRR” computation, but it should still permit the launch users to achieve much of the benefit 

of the “VAHIRR” feature.

1. Part I. Determination of average cloud thickness. The definition of “VAHIRR” requires determination 

of the average cloud top and the average cloud base above the height of the 0C isotherm within a square 

having sides 5.5 km (3 NM) north, east, south, and west of the ground projection of each point in the flight 

track. Average cloud thickness is defined as the difference of these two numbers. If the average cloud 

thickness cannot be determined at each point on the flight track, the maximum thickness within 5.5 km (3 NM) 

of the flight track may be used.

To determine the average cloud top height, the launch weather team may use any existing radar product that 

gives the height of the 0 dBZ cloud top, including "maximum height of reflectivity" and cross section 
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products. If the average height cannot be determined, the maximum height of the 0 dBZ reflectivity may be 

used. If the maximum height cannot be determined, use 18 km (60 kft) for the average cloud top.

The average height of the cloud base should be derived from radar data. It is the average of the higher of (a) 

the bottom of the portion of the cloud producing a radar reflectivity of 0 dBZ or greater or (b) the height of the 

0C isotherm where the 0 dBZ reflectivity extends below that level. If the average height of the cloud base 

cannot be determined, use the higher of (a) the height of the 0 degree C isotherm or (b) the lowest portion of 

the cloud producing a radar reflectivity of 0 dBZ or greater anywhere within each 5.5 km (3 NM) square 

defined above.

2. Part II. Volume Averaged Radar Reflectivity (VARR). There is no operationally feasible way to use 

existing radar products to compute a volume average reflectivity. A conservative substitute is the maximum 

reflectivity since the volume average will always be smaller than the maximum. The WSR-88D has a "User 

Selectable Layer Composite Reflectivity (URL)" product and the WSR-74C has a "Max" product with user 

selectable base and top. The Launch Weather Team should configure these products with the bottom of the 

layer at the height of the 0 degree C isotherm and the top above the height of the highest radar beam within 7.8 

km (4.2 NM) of the ground-projected flight track in the scan strategy being used. The WSR-88D product will 

have to be configured at the Radar Product Generator (RPG) and included in the product scheduler for the 

Principal User Processor (PUP) used by the launch weather team.

3. Part III. Evaluating the constraint. The “VAHIRR” constraint is satisfied for a point on the flight track 

if the "URL" or "Max" radar product (see Part II above) everywhere within the corresponding square (defined 

above) is less than 10 dBZ-km divided by the average cloud thickness in km within the same square (see Part I 

above). (In English units, this threshold would become 33 dBZ-kft divided by the average cloud thickness in 

kft.) This constraint must be satisfied for every point on the flight track.
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A1.12 Current (through 25 March 2010) FAA LLCC (14 CFR 417, Appendix G)

[Editor’s note 1: The date shown here is the date which appears (at the time of this writing) when the rules are 

accessed on line in the Code of Federal Regulations (CFR). This version of the FAA rules is based on the 2005 

LAP recommendations that were adopted by the Space Shuttle program as presented above in A1.10]

[Editor’s note 2: The requirement that the launch operator must have clear and convincing evidence that the 

LFCC are satisfied, and the requirement (informally called the “Good Sense Rule”) that any potentially 

hazardous conditions that are not covered by the LFCC be brought to the attention of the Launch Director do 

not appear in Appendix G and are not reproduced here. They appear instead in 14 CFR 417.113(c)(ii), and, 

like Appendix G, are mandatory.]

G417.1 General

For purposes of this section, the requirement for any weather monitoring and measuring equipment needed to 

satisfy the lightning flight commit criteria limits the equipment to only that which is needed. Accordingly, the 

equipment could include a ground-based, or airborne field mill, or a weather radar, but may or may not be 

limited to those items. Certain equipment, such as a field mill, when utilized with the lightning flight commit 

criteria, may increase launch opportunities because of the ability to verify the electric field in any cloud within 

5 nautical miles of the flight path. However, a field mill is not required in order to satisfy the lightning flight 

commit criteria.

(a) This appendix provides flight commit criteria to protect against natural lightning and lightning triggered by 

the flight of a launch vehicle. A launch operator must apply these criteria under §417.113 (c) for any launch 

vehicle that utilizes a flight safety system.

(b) The launch operator must employ:

(1) Any weather monitoring and measuring equipment needed to satisfy the lightning flight commit criteria.

(2) Any procedures needed to satisfy the lightning flight commit criteria.

(c) If a launch operator proposes any alternative lightning flight commit criteria, the launch operator must 

clearly and convincingly demonstrate that the alternative provides an equivalent level of safety.

G417.3 Definitions, Explanations and Examples

For the purpose of appendix G417:

Anvil cloud means a stratiform or fibrous cloud produced by the upper level outflow or blow-off from 

thunderstorms or convective clouds.

Associated means that two or more clouds are causally related to the same weather disturbance or are 

physically connected. Associated does not have to mean occurring at the same time. A cumulus cloud formed 

locally and a cirrus layer that is physically separated from that cumulus cloud and that is generated by a distant 

source are not associated, even if they occur over or near the launch point at the same time.

Bright band means an enhancement of radar reflectivity caused by frozen hydrometeors falling and beginning 

to melt at any altitude where the temperature is 0 degrees Celsius or warmer.

Cloud means a visible mass of water droplets or ice crystals produced by condensation of water vapor in the 

atmosphere.

Cloud edge means the visible boundary, including the sides, base, and top, of a cloud as seen by an observer. 

In the absence of a visible boundary as seen by an observer, the 0 dBZ radar reflectivity boundary defines a 

cloud edge.
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Cloud layer means a vertically continuous array of clouds, not necessarily of the same type, whose bases are 

approximately at the same level.

Cumulonimbus cloud means any convective cloud with any part at an altitude where the temperature is colder 

than -20 degrees Celsius.

Debris cloud means any cloud, except an anvil cloud, that has become detached from a parent cumulonimbus 

cloud or thunderstorm, or that results from the decay of a parent cumulonimbus cloud or thunderstorm.

Disturbed Weather means a weather system where dynamical processes destabilize the air on a scale larger 

than the individual clouds or cells. Examples of disturbed weather include fronts and troughs.

Electric field measurement aloft means the magnitude of the instantaneous vector electric field (E) at a known 

position in the atmosphere, such as measured by a suitably instrumented, calibrated, and located airbornefield-mill aircraft.

Electric field measurement at the surface of Earth means the 1-minute arithmetic average of the vertical 

electric field (Ez) at the ground measured by a ground-based field mill. The polarity of the electric field is the 

same as that of the potential gradient; that is, the polarity of the field at Earth's surface is the same as the 

dominant charge overhead. An interpolation based on electric field contours is not a measurement for purposes 

of this appendix.

Field mill is a specific class of electric-field sensor that uses a moving, grounded conductor to induce a timevarying electric charge on one or more sensing elements in proportion to the ambient electrostatic field.

Flight path means the planned normal flight trajectory, including its vertical and horizontal uncertainties to 

include the sum of the wind effects and the three-sigma guidance and performance deviations.

Moderate precipitation means a precipitation rate of 0.1 inches/hr or a radar reflectivity factor of 30 dBZ.

Nontransparent means cloud cover is nontransparent if (1) forms seen through it are blurred, indistinct, or 

obscured; or (2) forms are seen distinctly only through breaks in the cloud cover. Clouds with a radar 

reflectivity factor of 0 dBZ or greater are also nontransparent.

Ohms/Square means the surface resistance in ohms when a measurement is made from an electrode on one 

surface extending the length of one side of a square of any size to an electrode on the same surface extending 

the length of the opposite side of the square. The resistance measured in this way is independent of the area of 

a square.

Precipitation means detectable rain, snow, hail, graupel, or sleet at the ground; virga, or a radar reflectivity 

factor greater than 18 dBZ at altitude.

Specified Volume means the volume bounded in the horizontal by vertical plane, perpendicular sides located 

5.5 km (3 NM) north, east, south, and west of the point on the flight track, on the bottom by the 0 degree C 

level, and on the top by the upper extent of all clouds.

Thick cloud layer means one or more cloud layers whose combined vertical extent from the base of the bottom 

layer to the top of the uppermost layer exceeds a thickness of 4,500 feet. Cloud layers are combined with 

neighboring layers for determining total thickness only when they are physically connected by vertically 

continuous clouds, as, for example, when towering clouds in one layer contact or merge with clouds in a layer 

(or layers) above.
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Thunderstorm means any convective cloud that produces lightning.

Transparent Cloud cover is transparent if objects above, including higher clouds, blue sky, and stars can be 

distinctly seen from below; or objects, including terrain, buildings, and lights on the ground, can be distinctly 

seen from above. Transparency is only defined for the visible wavelengths.

Triboelectrification means the transfer of electrical charge from ice particles to the launch vehicle when the ice 

particles rub the vehicle during impact.

Volume-Averaged, Height-Integrated Radar Reflectivity (units of dBZ-kilometers) means the product of the 

volume-averaged radar reflectivity and the average cloud thickness within a specified volume relative to a 

point along the flight track.

Within is a function word used to specify a distance in all directions (horizontal, vertical, and slant separation) 

between a cloud edge and a flight path. For example, “within 10 nautical miles of a thunderstorm cloud” 

means that there must be a 10 nautical mile margin between every part of a thunderstorm cloud and the flight 

path.

G417.5 Lightning

(a) A launch operator must not initiate flight for 30 minutes after any type of lightning occurs in a 

thunderstorm if the flight path will carry the launch vehicle within 10 nautical miles of that thunderstorm.

(b) A launch operator must not initiate flight for 30 minutes after any type of lightning occurs within 10 

nautical miles of the flight path unless:

(1) The cloud that produced the lightning is not within 10 nautical miles of the flight path;

(2) There is at least one working field mill within 5 nautical miles of each such lightning flash; and

(3) The absolute values of all electric field measurements made at the Earth's surface within 5 nautical miles of 

the flight path and at each field mill specified in paragraph (b)(2) of this section have been less than 1000 

volts/meter for 15 minutes or longer.

(c) If a cumulus cloud remains 30 minutes after the last lightning occurs in a thunderstorm, section G417.7 

applies. Sections G417.9 and G417.11 apply to any anvil or detached anvil clouds. Section G417.13 applies to 

debris clouds.

G417.7 Cumulus Clouds

For the purposes of this section, “cumulus clouds” do not include altocumulus, cirrocumulus, or stratocumulus 

clouds.

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle within 10 nautical 

miles of any cumulus cloud that has a cloud top at an altitude where the temperature is colder than −20 degrees 

Celsius.

(b) A launch operator must not initiate flight if the flight path will carry the launch vehicle within 5 nautical 

miles of any cumulus cloud that has a cloud top at an altitude where the temperature is colder than −10 degrees 

Celsius.

(c) A launch operator must not initiate flight if the flight path will carry the launch vehicle through any 

cumulus cloud with its cloud top at an altitude where the temperature is colder than −5 degrees Celsius.
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(d) A launch operator must not initiate flight if the flight path will carry the launch vehicle through any 

cumulus cloud that has a cloud top at an altitude where the temperature is between +5 degrees Celsius and −5 

degrees Celsius unless:

(1) The cloud is not producing precipitation;

(2) The horizontal distance from the center of the cloud top to at least one working field mill is less than 2 

nautical miles; and

(3) All electric field measurements made at the Earth's surface within 5 nautical miles of the flight path and at 

each field mill used as required by paragraph (d)(2) of this section have been between −100 volts/meter and 

+500 volts/meter for 15 minutes or longer.

G417.9 Attached Anvil Clouds

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through, or within 

10 nautical miles of, a nontransparent part of any attached anvil cloud for the first 30 minutes after the last 

lightning discharge in or from the parent cloud or anvil cloud.

(b) A launch operator must not initiate flight if the flight path will carry the launch vehicle through, or within 5 

nautical miles of, a nontransparent part of any attached anvil cloud between 30 minutes and three hours after 

the last lightning discharge in or from the parent cloud or anvil cloud unless:

(1) The portion of the attached anvil cloud within 5 nautical miles of the flight path is located entirely at 

altitudes where the temperature is colder than 0 degrees Celsius; and

(2) The volume-averaged, height-integrated radar reflectivity is less than +33 dBZ-kft everywhere along the 

portion of the flight path where any part of the attached anvil cloud is within the volume.

(c) A launch operator must not initiate flight if the flight path will carry the launch vehicle through a 

nontransparent part of any attached anvil cloud more than 3 hours after the last lightning discharge in or from 

the parent cloud or anvil cloud unless:

(1) The portion of the attached anvil cloud within 5 nautical miles of the flight path is located entirely at 

altitudes where the temperature is colder than 0 degrees Celsius; and

(2) The volume-averaged, height-integrated radar reflectivity is less than +33 dBZ-kft everywhere along the 

portion of the flight path where any part of the attached anvil cloud is within the specified volume.

G417.11 Detached Anvil Clouds

For the purposes of this section, detached anvil clouds are never considered debris clouds.

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through or within 

10 nautical miles of a nontransparent part of a detached anvil cloud for the first 30 minutes after the last 

lightning discharge in or from the parent cloud or anvil cloud before detachment or after the last lightning 

discharge in or from the detached anvil cloud after detachment.

(b) A launch operator must not initiate flight if the flight path will carry the launch vehicle within 5 nautical 

miles of a nontransparent part of a detached anvil cloud between 30 minutes and 3 hours after the time of the 

last lightning discharge in or from the parent cloud or anvil cloud before detachment or after the last lightning 

discharge in or from the detached anvil cloud after detachment unless section (1) or (2) is satisfied:

(1) This section is satisfied if all three of the following conditions are met:

(i) There is at least one working field mill within 5 nautical miles of the detached anvil cloud; and

(ii) The absolute values of all electric field measurements at the surface within 5 nautical miles of the flight 

path and at each field mill specified in (1) above have been less than 1000 V/m for 15 minutes; and

(iii) The maximum radar return from any part of the detached anvil cloud within 5 nautical miles of the flight 

path has been less than 10 dBZ for 15 minutes.

(2) This section is satisfied if both of the following conditions are met:
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(i) The portion of the detached anvil cloud within 5 nautical miles of the flight path is located entirely at 

altitudes where the temperature is colder than 0 degrees Celsius; and

(ii) The volume-averaged, height-integrated radar reflectivity is less than +33 dBZ-kft everywhere along the 

portion of the flight path where any part of the detached anvil cloud is within the specified volume.

(c) A launch operator must not initiate flight if the flight path will carry the launch vehicle through a 

nontransparent part of a detached anvil cloud unless Section (1) or (2) is satisfied.

(1) This section is satisfied if both of the following conditions are met:

(i) At least 4 hours have passed since the last lightning discharge in or from the detached anvil cloud; and

(ii) At least 3 hours have passed since the time that the anvil cloud is observed to be detached from the parent 

cloud.

(2) This section is satisfied if both of the following conditions are met.

(i) The portion of the detached anvil cloud within 5 nautical miles of the flight path is located entirely at 

altitudes where the temperature is colder than 0 degrees Celsius; and

(ii) The volume-averaged, height-integrated radar reflectivity is less than +33 dBZ-kft everywhere along the 

portion of the flight path where any part of the detached anvil cloud is within the specified volume.

G417.13 Debris Clouds

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through any 

nontransparent part of a debris cloud for 3 hours after the debris cloud is observed to be detached from the 

parent cloud or after the debris cloud is observed to have formed from the decay of the parent cloud top to an 

altitude where the temperature is warmer than −10 degrees Celsius. The 3-hour period must begin again at the 

time of any lightning discharge in or from the debris cloud.

(b) A launch operator must not initiate flight if the flight path will carry the launch vehicle within 5 nautical 

miles of a nontransparent part of a debris cloud during the 3-hour period defined in paragraph (a) of this 

section, unless:

(1) There is at least one working field mill within 5 nautical miles of the debris cloud;

(2) The absolute values of all electric field measurements at the Earth's surface within 5 nautical miles of the 

flight path and measurements at each field mill employed required by paragraph (b)(1) of this section have 

been less than 1000 volts/meter for 15 minutes or longer; and

(3) The maximum radar return from any part of the debris cloud within 5 nautical miles of the flight path has 

been less than 10 dBZ for 15 minutes or longer.

G417.15 Disturbed Weather

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through a 

nontransparent cloud associated with disturbed weather that has clouds with cloud tops at altitudes where the 

temperature is colder than 0 degrees Celsius and that contains, within 5 nautical miles of the flight path:

(1) Moderate or greater precipitation; or

(2) Evidence of melting precipitation such as a radar bright band.

G417.17 Thick Cloud Layers

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through a 

nontransparent part of a cloud layer that is:

(1) Greater than 4,500 feet thick and any part of the cloud layer along the flight path is located at an altitude 

where the temperature is between 0 degrees Celsius and −20 degrees Celsius; or
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(2) Connected to a thick cloud layer that, within 5 nautical miles of the flight path, is greater than 4,500 feet 

thick and has any part located at any altitude where the temperature is between 0 degrees Celsius and −20 

degrees Celsius.

(b) A launch operator need not apply the lightning commit criteria in paragraphs (a)(1) and (a)(2) of this 

section if the thick cloud layer is a cirriform cloud layer that has never been associated with convective clouds, 

is located only at temperatures of −15 degrees Celsius or colder, and shows no evidence of containing liquid 

water.

G417.19 Smoke Plumes

(a) A launch operator must not initiate flight if the flight path will carry the launch vehicle through any 

cumulus cloud that has developed from a smoke plume while the cloud is attached to the smoke plume, or for 

the first 60 minutes after the cumulus cloud is observed to be detached from the smoke plume.

(b) Section G417.7 applies to cumulus clouds that have formed above a fire but have been detached from the 

smoke plume for more than 60 minutes.

G417.21 Surface Electric Fields

(a) A launch operator must not initiate flight for 15 minutes after the absolute value of any electric field 

measurement at the Earth's surface within 5 nautical miles of the flight path has been greater than 1500 

volts/meter.

(b) A launch operator must not initiate flight for 15 minutes after the absolute value of any electric field 

measurement at the Earth's surface within 5 nautical miles of the flight path has been greater than 1000 

volts/meter unless:

(1) All clouds within 10 nautical miles of the flight path are transparent; or

(2) All nontransparent clouds within 10 nautical miles of the flight path have cloud tops at altitudes where the 

temperature is warmer than +5 degrees Celsius and have not been part of convective clouds that have cloud 

tops at altitudes where the temperature is colder than −10 degrees Celsius within the last 3 hours.

G417.23 Triboelectrification

(a) A launch operator must not initiate flight if the flight path will go through any part of a cloud at an altitude 

where the temperature is colder than −10 degrees Celsius up to the altitude at which the launch vehicle's 

velocity exceeds 3000 feet/second; unless

(1) The launch vehicle is “treated” for surface electrification; or

(2) A launch operator demonstrates by test or analysis that electrostatic discharges on the surface of the launch 

vehicle caused by triboelectrification will not be hazardous to the launch vehicle or the spacecraft.

(b) A launch vehicle is treated for surface electrification if

(1) All surfaces of the launch vehicle susceptible to ice particle impact are such that the surface resistivity is 

less than 109 ohms/square; and

(2) All conductors on surfaces (including dielectric surfaces that have been treated with conductive coatings) 

are bonded to the launch vehicle by a resistance that is less than 105 ohms.
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A1.13 LAP Recommendation (2008) in FAA format.

[Editor’s Note: These are essentially the same rules as those adopted by the Space Shuttle program in 2009 and 

presented above in A1.11. As of May 2010, the FAA has not yet adopted these recommended changes to the 

FAA LFCC.]

[Editor’s Note: The LAP expects section 417.113(c)(ii) (see Editor’s Note 2 to A1.12 above) to remain in 

effect if these proposed LFCC are adopted. Its content is an integral part of the LAP’s recommendation.]

A. G417.1 General

Each of the Lightning Flight Commit Criteria (LFCC) requires clear and convincing evidence to trained 

weather personnel that its constraints are not violated. A launch operator must not initiate flight unless the 

constraints of all LFCC are satisfied. Whenever there is ambiguity about which of several LFCC applies to a 

particular situation, all potentially applicable LFCC must be applied. Under some conditions trained weather 

personnel can make a clear and convincing determination that the LFCC are not violated based on visual 

observations alone. However, if the weather personnel have access to additional information such as 

measurements from weather radar, lightning sensors, electric "field mills," and/or aircraft, this information can 

be used to increase both safety and launch availability. If the additional information is within the criteria 

outlined in the LFCC, it would allow a launch to take place where a visual observation alone would not.

(a) This appendix provides flight commit criteria to protect against natural lightning and lightning 

triggered by the flight of a launch vehicle. A launch operator must apply these criteria under § 

417.113 (c) for any launch vehicle that utilizes a flight safety system.

(b) The launch operator must employ:

(1) Any weather monitoring and measuring equipment needed to satisfy the lightning flight commit 

criteria.

(2) Any procedures needed to satisfy the lightning flight commit criteria.

(c) If a launch operator proposes any alternative lightning flight commit criteria, the launch operator 

must clearly and convincingly demonstrate that the alternative provides an equivalent level of safety.

B. G417.3 Definitions, Explanations and Examples

For the purpose of this appendix, distance from an electric "field mill" is measured differently than distance 

from any other object or measurement point: Distance between a "radar reflectivity" or "VAHIRR" 

measurement point and any object or the "flight path" is the shortest separation (horizontal, vertical, or slant 

range) between that point and the nearest part of the object or "flight path." Similarly, distance between the 

"flight path" and any object is the shortest separation between any point on the "flight path" the nearest part 

of that object. For example, "every point less than or equal to 1 nautical mile from the 'flight path'" [see F. 

G417.11(c)(2) Attached "Anvil Clouds"] means that the "VAHIRR" threshold must be satisfied at every point 

throughout the entire volume defined by a 1 nautical mile radius from every point on the "flight path." (See 

also the additional explanation beneath the definition of "cloud.") In contrast, distance between a "field mill" 

or an "electric field measurement" and any object or the "flight path" is always measured horizontally between 

that mill or measurement point and the nearest part of the vertical projection of the object or "flight path" onto 

the surface of Earth. For example, "from the center of the 'cloud top' to at least one working 'field mill'" [see E. 

G417.9(d)(2) Cumulus "Clouds"] means that the horizontal distance between the "field mill" and a point on 

the surface directly beneath the center of the "cloud top" must be less than 2 nautical miles.
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The following bold-face terms are defined here and appear in quotes wherever they are used in accordance 

with these definitions elsewhere in this appendix:

Anvil cloud means a stratiform or fibrous "cloud" produced by the upper outflow or blow-off from 

"thunderstorms" or convective "clouds" having tops at altitudes where the temperature is colder than or equal 

to -10 degrees Celsius.

Associated means that two or more "clouds" are causally related to the same "disturbed weather" system or are 

physically connected. "Clouds" occurring at the same time are not necessarily "associated." A cumulus 

"cloud" formed locally and a cirrus layer that is physically separated from that cumulus "cloud" and that is 

generated by a distant source are not "associated," even if they occur over or near the launch point at the same 

time.

Average cloud thickness is the altitude difference (in kilometers, km hereafter) between the average top and 

the average base of all clouds in the "specified volume." The cloud base to be averaged is the higher of (1) the 

0 degree Celsius level and (2) the lowest extent (in altitude) of all "radar reflectivity" measurements of 0 dBZ 

or greater. Similarly, the cloud top to be averaged is the highest extent (in altitude) of all "radar reflectivity" 

measurements of 0 dBZ or greater. Given the grid-point representation of a typical radar processor, allowance 

must be made for the vertical separation of grid points in computing "average cloud thickness": The cloud 

base at any horizontal position shall be taken as the altitude of the corresponding base grid point minus half of 

the grid-point vertical separation. Similarly, the cloud top at that horizontal position shall be taken as the 

altitude of the corresponding top grid point plus half of this vertical separation. Thus, a cloud represented by 

only a single grid point having a "radar reflectivity" equal to or greater than 0 dBZ in the "specified volume" 

would have an "average cloud thickness" equal to the vertical grid-point separation in its vicinity.

Bright band means an enhancement of "radar reflectivity" caused by frozen hydrometeors falling and 

beginning to melt at any altitude where the temperature is 0 degrees Celsius or warmer.

Cloud means a visible mass of suspended water droplets or ice crystals. The "cloud" is considered to be the 

entire volume enclosed by the visible, "nontransparent cloud" boundary as seen by an observer, or, in the 

absence of a visual observation, by the 0 dBZ "radar reflectivity" boundary. A visual evaluation of 

transparency is preferred whenever possible.

Distance from the "cloud" to a point in question refers to the separation between the point and the nearest part 

of that "cloud." Specifically, the wording, "less than or equal to 10 nautical miles from any cumulus 'cloud'" 

means that the "flight path" must not penetrate either the interior of the "cloud" itself or the volume between 0 

and 10 nautical miles, inclusive, outside the "cloud" boundary [for example, see E. G417.9(a), Cumulus 

"Clouds"]. On the other hand, "between 0 and 3 nautical miles, inclusive, from" refers only to the volume at a 

distance that is greater than or equal to 0, but less than or equal to 3, nautical miles outside the "cloud" 

boundary, specifically omitting the interior of the "cloud" itself [for example, see H. G417.15(a), "Debris 

Clouds"].

Cloud layer means a vertically continuous array of "clouds," not necessarily of the same type, whose bases are 

approximately at the same level.

Cloud top means the visible top of the cloud, or, in the absence of a visual observation, the 0 dBZ radar top. A 

visual evaluation of "cloud top" is preferred whenever possible.

Cone of silence means the volume in an inverted circular cone centered on the radar that is generated by all 

elevation angles greater than the maximum elevation angle used in the radar scan strategy. For the purpose of 
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"VAHIRR" calculation this volume is capped by the observed maximum "cloud top" height, the observed 

tropopause height, or an altitude of 20 km (66 kft), whichever is lowest.

Cumulonimbus cloud means any convective "cloud" with any part at an altitude where the temperature is 

colder than –20 degrees Celsius.

Debris cloud means any "cloud," except an "anvil cloud," that has become detached from a parent 

"cumulonimbus cloud" or "thunderstorm," or that results from the decay of a parent "cumulonimbus cloud" or 

"thunderstorm."

Disturbed weather means a weather system where dynamical processes destabilize the air on a scale larger 

than individual "clouds" or cells. Examples of "disturbed weather" include fronts, troughs, and squall lines.

Electric field measurement means the 1-minute arithmetic average of the vertical electric field (Ez) at the 

surface of Earth, measured by a ground-based "field mill." The polarity of the electric field is the same as that 

of the potential gradient; that is, the polarity of the field at Earth's surface is the same as the dominant charge 

overhead. Do not use interpolated electric field contours for purposes of this appendix. An "'electric field 

measurement' less than or equal to 5 nautical miles from the 'flight path'" [e.g., C. G417.5(a) Surface Electric 

Fields] is not applicable if the altitude of the flight path everywhere above the 5 nautical mile circle around the 

"field mill" in question is greater than 20 km (66 kft).

Field mill is a specific class of electric-field sensor that uses a moving, grounded conductor to induce a timevarying electric charge on one or more sensing elements in proportion to the ambient electrostatic field.

Flight path means the planned nominal flight trajectory, including its vertical and horizontal uncertainties 

specified by the three-sigma guidance and performance deviations.

Moderate precipitation means a "precipitation" rate of 0.1 inches/hr or a "radar reflectivity" factor of 30 dBZ.

Nontransparent. "Cloud" cover is "nontransparent" if one or more of the following conditions is present:

(a) Objects above, including higher "clouds," blue sky, and stars, are blurred, indistinct, or obscured as viewed 

from below; or objects below, including terrain, buildings, and lights on the ground, are blurred, indistinct, or 

obscured as viewed from above; when looking through the "cloud" cover at visible wavelengths (the sun and 

moon may not be used to evaluate transparency);

(b) Such objects are seen distinctly only through breaks in the "cloud" cover; or

(c) The "cloud" cover has a "radar reflectivity" factor of 0 dBZ or greater.

Precipitation means detectable rain, snow, hail, graupel, or sleet at the ground; virga; or a "radar reflectivity" 

factor greater than 18 dBZ at any altitude above the ground.

Radar reflectivity means the radar return from hydrometeors, in dBZ, measured by a meteorological radar 

operating at a wavelength greater than or equal to 5 cm. A "radar reflectivity" measurement is valid only in the 

absence of significant attenuation by intervening "precipitation" or by water or ice on the radome.

Specified volume. The volume bounded in the horizontal by vertical planes with perpendicular sides located 

5.5 km (3 nautical miles) north, east, south, and west of the point at which "VAHIRR" is being computed. The 

volume is bounded on the bottom at the altitude where the temperature is 0 degrees Celsius, and on the top by 

a fixed altitude of 20 km (66 kft).
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Thick cloud layer means one or more "cloud layers" whose combined vertical extent from the base of the 

bottom layer to the "cloud top" of the uppermost layer exceeds a thickness of 4,500 feet. "Cloud layers" are 

combined with neighboring layers for determining total thickness only when they are physically connected by 

vertically continuous "clouds," as, for example, when towering "clouds" in one layer contact or merge with 

"clouds" in a layer (or layers) above.

Thunderstorm means any convective "cloud" that produces lightning.

Transparent. Any "cloud" that is not "nontransparent" is "transparent."

Treated means that a launch vehicle satisfies both of the following conditions:

(a) All surfaces of the launch vehicle susceptible to ice particle impact are such that the surface resistivity is 

less than 109 "Ohms per square;" and

(b) All conductors on surfaces (including dielectric surfaces that have been coated with conductive materials) 

are bonded to the launch vehicle by a resistance that is less than 105 ohms.

Triboelectrification means the transfer of electrical charge between ice particles and the launch vehicle when 

the ice particles collide with the vehicle during flight.

Volume-Averaged, Height-Integrated Radar Reflectivity (VAHIRR) is the product of the "volumeaveraged radar reflectivity" and the "average cloud thickness" in a "specified volume" surrounding any point at 

which "VAHIRR" is being computed (units of dBZ-km). The "specified volume" must not contain any portion 

of the "cone of silence" above the radar, nor any portion of any sectors that may have been blocked out for 

payload-safety reasons.

VAHIRR application criteria: The individual grid-point reflectivity measurements used to determine either 

the "volume-averaged radar reflectivity" or the "average cloud thickness" must be meteorological "radar 

reflectivity" measurements. For "VAHIRR"-evaluation points along the "flight path" itself (not those at a 

prescribed distance away from the "flight path"), the "volume-averaged, height-integrated radar reflectivity" is 

not applicable at any point that is less than or equal to 10 nautical miles from any "radar reflectivity" of 35 

dBZ or greater at altitudes of 4 km (13 kft) or greater above mean sea level, nor is it applicable at any point 

that is less than or equal to 10 nautical miles from any type of lightning that has occurred in the previous 5 

minutes.

Volume-averaged radar reflectivity is the arithmetic average (in dBZ) of the "radar reflectivity" in the 

"specified volume." Normally, a radar processor will report reflectivity values interpolated onto a regular, 

three-dimensional array of grid points. Any such grid point in the "specified volume" is included in the 

average if and only if it has a "radar reflectivity" equal to or greater than 0 dBZ. If fewer than 10% of the grid 

points in the "specified volume" have "radar reflectivity" measurements equal to or greater than 0 dBZ, then 

the "volume-averaged radar reflectivity" is either the maximum "radar reflectivity" (in dBZ) in the "specified 

volume," or 0 dBZ, whichever is greater.

C. G417.5 Surface Electric Fields

(a) A launch operator must not initiate flight for 15 minutes after the absolute value of any "electric field 

measurement" less than or equal to 5 nautical miles from the "flight path" has been greater than or equal to 

1500 volts/meter.
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(b) A launch operator must not initiate flight for 15 minutes after the absolute value of any "electric field 

measurement" less than or equal to 5 nautical miles from the "flight path" has been greater than or equal to 

1000 volts/meter unless either Section 1 or Section 2 is satisfied:

(1) All clouds less than or equal to 10 nautical miles from the "flight path" are "transparent;" or

(2) All "clouds" less than or equal to 10 nautical miles from the "flight path" have "cloud tops" at 

altitudes where the temperature is warmer than +5 degrees Celsius and have not been part of 

convective "clouds" with "cloud tops" at altitudes where the temperature is colder than or equal to −10 

degrees Celsius during the last 3 hours.

D. G417.7 Lightning

(a) A launch operator must not initiate flight for 30 minutes after any type of lightning occurs in a 

"thunderstorm" if the "flight path" will carry the launch vehicle less than or equal to 10 nautical miles from 

that "thunderstorm." An attached "anvil cloud" is not considered part of its parent "thunderstorm," but is 

covered instead by Section F, Attached "Anvil Clouds."

(b) A launch operator must not initiate flight for 30 minutes after any type of lightning occurs less than or 

equal to 10 nautical miles from the "flight path" unless all three of the following conditions are satisfied:

(1) The "cloud" that produced the lightning is greater than10 nautical miles from the "flight path;"

(2) There is at least one working "field mill" less than 5 nautical miles from each such lightning 

discharge; and

(3) The absolute values of all "electric field measurements" less than or equal to 5 nautical miles from 

the "flight path," and at each "field mill" specified in paragraph (b)(2) of this section, have been less 

than 1000 volts/meter for 15 minutes or longer.

E. G417.9 Cumulus "Clouds"

For the purposes of this section, “cumulus 'clouds'” do not include cirrocumulus, altocumulus, or 

stratocumulus "clouds." An attached "anvil cloud" is never considered part of its parent cumulus "cloud," but 

is covered instead by Section F, Attached "Anvil Clouds." Section G, Detached "Anvil Clouds," applies to any 

detached "anvil cloud." Section H, "Debris Clouds," applies to "debris clouds."

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 10 nautical miles from any cumulus "cloud" that has a "cloud top" at an altitude where the temperature is 

colder than or equal to -20 degrees Celsius.

(b) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 5 nautical miles from any cumulus "cloud" that has a "cloud top" at an altitude where the temperature is 

colder than or equal to -10 degrees Celsius.

(c) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through any 

cumulus "cloud" with its "cloud top" at an altitude where the temperature is colder than or equal to -5 degrees 

Celsius.

(d) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through any 

cumulus "cloud" that has a "cloud top" at an altitude where the temperature lies in the range from warmer than 
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-5 degrees Celsius to colder than or equal to +5 degrees Celsius unless all three of the following conditions 

are satisfied:

(1) The "cloud" is not producing "precipitation;"

(2) The distance from the center of the "cloud top" to at least one working "field mill" is less than 2 

nautical miles; and

(3) All "electric field measurements" less than or equal to 5 nautical miles from the "flight path," and 

at each "field mill" specified in paragraph (d)(2) of this section, have been greater than −100 

volts/meter, but less than +500 volts/meter, for 15 minutes or longer.

F. G417.11 Attached "Anvil Clouds"

For the purposes of this section, if there has never been lightning in or from the parent "cloud" or "anvil 

cloud," sub-sections (a) and (b) shall be considered satisfied, but sub-section (c) shall still apply.

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 10, but greater than 5, nautical miles from any attached "anvil cloud" for the first 30 minutes after the last 

lightning discharge in or from the parent "cloud" or "anvil cloud" unless the portion of the attached "anvil 

cloud" less than or equal to 10 nautical miles from the "flight path" is located entirely at altitudes where the 

temperature is colder than 0 degrees Celsius.

(b) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 5, but greater than 3, nautical miles from any attached "anvil cloud" for the first three hours after the last 

lightning discharge in or from the parent "cloud" or "anvil cloud" unless the portion of the attached "anvil 

cloud" less than or equal to 5 nautical miles from the "flight path" is located entirely at altitudes where the 

temperature is colder than 0 degrees Celsius.

(c) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 3 nautical miles from any attached "anvil cloud" unless all three of the following conditions are satisfied:

(1) The portion of the attached "anvil cloud" less than or equal to 5 nautical miles from the "flight 

path" is located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

(2) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 dBZkft) at every point less than or equal to 1 nautical mile from the "flight path;" and

(3) All of the "VAHIRR application criteria" are satisfied.

G. G417.13 Detached "Anvil Clouds"

For the purposes of this section, detached "anvil clouds" are never considered "debris clouds."

For the purposes of this section, if there has never been lightning in or from the parent "cloud" or "anvil 

cloud," sub-sections (a), (b), (c), and (d)(1)(i) shall be considered satisfied, but sub-sections (d)(1)(ii), and 

(d)(2), shall still apply.

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle less than or equal 

to 10, but greater than 3, nautical miles from a detached "anvil cloud" for the first 30 minutes after the last 

lightning discharge in or from the parent "cloud" or "anvil cloud" before detachment or after the last lightning 
Page 138 of 234

discharge in or from the detached "anvil cloud" after detachment unless the portion of the detached "anvil 

cloud" less than or equal to 10 nautical miles from the "flight path" is located entirely at altitudes where the 

temperature is colder than 0 degrees Celsius.

(b) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle between 0 (zero) 

and 3 nautical miles, inclusive, from a detached "anvil cloud" for the first 30 minutes after the time of the last 

lightning discharge in or from the parent "cloud" or "anvil cloud" before detachment or after the last lightning 

discharge in or from the detached "anvil cloud" after detachment unless all three of the following conditions 

are met:

(1) The portion of the detached "anvil cloud" less than or equal to 5 nautical miles from the "flight 

path" is located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

(2) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 dBZkft) at every point less than or equal to 1 nautical mile from the "flight path;" and

(3) All of the "VAHIRR application criteria" are satisfied.

(c) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle between 0 (zero) 

and 3 nautical miles, inclusive, from a detached "anvil cloud" less than or equal to 3 hours, but greater than 30 

minutes, after the time of the last lightning discharge in or from the parent "cloud" or "anvil cloud" before 

detachment or after the last lightning discharge in or from the detached "anvil cloud" after detachment unless 

Section (1) or Section (2) is satisfied:

(1) This section is satisfied if all three of the following conditions are met:

(i) There is at least one working "field mill" less than 5 nautical miles from the detached "anvil 

cloud;"

(ii) The absolute values of all "electric field measurements" less than or equal to 5 nautical 

miles from the "flight path," and at each "field mill" specified in paragraph (c)(1)(i) of this 

section, have been less than 1000 V/m for 15 minutes; and

(iii) The maximum radar reflectivity from any part of the detached "anvil cloud" less than or 

equal to 5 nautical miles from the "flight path" has been less than +10 dBZ for 15 minutes.

(2) This section is satisfied if all three of the following conditions are met:

(i) The portion of the detached "anvil cloud" less than or equal to 5 nautical miles from the 

"flight path" is located entirely at altitudes where the temperature is colder than 0 degrees 

Celsius;

(ii) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 

dBZ-kft) at every point less than or equal to 1 nautical mile from the "flight path;" and

(iii) All of the "VAHIRR application criteria" are satisfied.

(d) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through a 

detached "anvil cloud" unless Section (1) or Section (2) is satisfied

(1) This section is satisfied if both of the following conditions are met.
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(i) At least 4 hours have passed since the last lightning discharge in or from the detached 

"anvil cloud;" and

(ii) At least 3 hours have passed since the time that the "anvil cloud" is observed to be 

detached from the parent "cloud."

(2) This section is satisfied if all three of the following conditions are met.

(i) The portion of the detached "anvil cloud" less than or equal to 5 nautical miles from the 

"flight path" is located entirely at altitudes where the temperature is colder than 0 degrees 

Celsius;

(ii) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 

dBZ-kft) everywhere along the "flight path;" and

(iii) All of the "VAHIRR application criteria" are satisfied.

H. G417.15 "Debris Clouds"

The 3-hour time period defined in this Section must begin again at the time of any lightning discharge in or 

from the "debris cloud."

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle between 0 and 3 

nautical miles, inclusive, from a "debris cloud" for 3 hours after the "debris cloud" is observed to be detached 

from the parent "cloud," or after the "debris cloud" is observed to have formed by the collapse of the parent 

"cloud top" to an altitude where the temperature is warmer than −10 degrees Celsius unless Section (1) or

Section (2) is satisfied:

(1) This section is satisfied if all three of the following conditions are met:

(i) There is at least one working "field mill" less than 5 nautical miles from the "debris cloud;"

(ii) The absolute values of all "electric field measurements" less than or equal to 5 nautical 

miles from the "flight path" and at each "field mill" employed by paragraph (a)(1)(i) of this 

section has been less than 1000 volts/meter for 15 minutes or longer; and

(iii) The maximum radar reflectivity from any part of the "debris cloud" less than or equal to 5 

nautical miles from the "flight path" has been less than +10 dBZ for 15 minutes or longer.

(2) This section is satisfied if all three of the following conditions are met:

(i) The portion of the "debris cloud" less than or equal to 5 nautical miles from the "flight 

path" is located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

(ii) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 

dBZ-kft) at every point less than or equal to 1 nautical mile from the "flight path;" and

(iii) All of the "VAHIRR application criteria" are satisfied.
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(b) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through any 

"debris cloud" during the 3-hour period defined in paragraph (a) of this section, unless all three of the 

following conditions are met:

(1) The portion of the "debris cloud" less than or equal to 5 nautical miles from the "flight path" is 

located entirely at altitudes where the temperature is colder than 0 degrees Celsius;

(2) The "volume-averaged, height-integrated radar reflectivity" is less than +10 dBZ-km (+33 dBZkft) everywhere along the "flight path;" and

(3) All of the "VAHIRR application criteria" are satisfied.

I. G417.17 "Disturbed Weather"

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through a "cloud" 

"associated" with "disturbed weather" that has "clouds" with "cloud tops" at altitudes where the temperature is 

colder than or equal to 0 degrees Celsius and that contains, less than or equal to 5-nautical miles from the 

"flight path," either:

(1) "Moderate precipitation" or greater; or

(2) Evidence of melting "precipitation" such as a radar "bright band."

J. G417.19 "Thick Cloud Layers"

For the purposes of this section neither attached nor detached "anvil clouds" are considered "thick cloud 

layers."

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through a "cloud 

layer" that is either:

(1) Greater than or equal to 4,500 feet thick and any part of the "cloud layer" along the "flight path" is 

located at an altitude where the temperature is between 0 degrees Celsius and −20 degrees Celsius, 

inclusive; or

(2) Connected to a "thick cloud layer" that, less than or equal to 5 nautical miles from the "flight path," 

is greater than or equal to 4,500 feet thick and has any part located at an altitude where the temperature 

is between 0 degrees Celsius and −20 degrees Celsius, inclusive.

(b) A launch operator need not apply the lightning commit criteria in paragraphs (a)(1) and (a)(2) of this 

section if the "thick cloud layer" is a cirriform "cloud layer" that has never been "associated" with convective 

"clouds," is located entirely at altitudes where the temperature is colder than or equal to −15 degrees Celsius, 

and shows no evidence of containing liquid water.

K. G417.21 Smoke Plumes

(a) A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through any 

cumulus "cloud" that has developed from a smoke plume while the "cloud" is attached to the smoke plume, or 

for the first 60 minutes after the cumulus "cloud" is observed to be detached from the smoke plume.
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(b) Section E, Cumulus "Clouds," applies to cumulus "clouds" that have formed above a fire but have been 

detached from the smoke plume for more than 60 minutes.

L. G417.23 "Triboelectrification"

A launch operator must not initiate flight if the "flight path" will carry the launch vehicle through any part of a 

cloud, specifically including all "transparent" parts, at any altitude where both Section (a) and Section (b) are 

satisfied:

(a) The temperature is colder than or equal to −10 degrees Celsius; and

(b) The launch vehicle’s velocity is less than or equal to 3000 feet/second;

unless Section (1) or Section (2) is satisfied:

(1) The launch vehicle is “treated” for surface electrification; or 

(2) A launch operator has previously demonstrated by test or analysis that electrostatic discharges on 

the surface of the launch vehicle caused by "triboelectrification" will not be hazardous to the launch 

vehicle or the spacecraft.

Interim Instructions for Implementation of Volume Averaged Height Integrated Radar Reflectivity (VAHIRR) 

dated 28 October 2004

The VAHIRR quantity referred to in Rules G417.9 and G717.11 requires computation of both a volume 

average reflectivity and an average cloud thickness. These quantities are then multiplied to produce the 

VAHIRR. Neither of these quantities is currently available as a product on the WSR-88D and WSR-74C radar 

systems used to support launch operations. This instruction provides a methodology for evaluating VAHIRR 

criteria with currently available radar products. The methodology provides a result that is more conservative 

than a direct VAHIRR computation, but it should still permit the launch customer to reap much of the benefit 

of the new rule.

Part I. Determination of average cloud thickness. The definition of the VAHIRR requires determination of the 

average cloud top and the average cloud base above the height of the 0C isotherm within a square having sides 

5.5 km (3 n. mi.) north, east, south, and west of the ground projection of each point in the flight track. Average 

cloud thickness is defined as the difference of these two numbers. If the average cloud thickness cannot be 

determined at each point on the flight track, the maximum thickness within 5.5 km (3 n. mi.) of the flight track 

may be used.

To determine the average cloud top height, the launch weather team may use any existing radar product that 

gives the height of the 0 dBZ cloud top, including "maximum height of reflectivity" and cross section 

products. If the average height cannot be determined, the maximum height of the 0 dBZ reflectivity may be 

used. If the maximum height cannot be determined, use 18 km (60 kft) for the average cloud top.

The average height of the cloud base should be derived from radar data. It is the average of the higher of (a) 

the bottom of the portion of the cloud producing a radar reflectivity of 0 dBZ or greater or (b) the height of the 

0C isotherm where the 0 dBZ reflectivity extends below that level. If the average height of the cloud base 

cannot be determined, use the higher of (a) the height of the 0 degree C isotherm or (b) the lowest portion of 

the cloud producing a radar reflectivity of 0 dBZ or greater anywhere within each 5.5 km (3 n. mi.) square 

defined above.
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Part II. Volume Averaged Radar Reflectivity (VARR). There is no operationally feasible way to use existing 

radar products to compute a volume average reflectivity. A conservative substitute is the maximum reflectivity 

since the volume average will always be smaller than the maximum. The WSR-88D has a "User Selectable 

Layer Composite Reflectivity (URL)" product and the WSR-74C has a "Max" product with user selectable 

base and top. The launch weather team should configure these products with the bottom of the layer at the 

height of the 0 degree C isotherm and the top above the height of the highest radar beam within 7.8 km (4.2 n. 

mi.) of the ground-projected flight track in the scan strategy being used. The WSR-88D product will have to be 

configured at the RPG and included in the product scheduler for the PUP used by the launch weather team.

Part III. Evaluating the constraint. The VAHIRR constraint is satisfied for a point on the flight track if the 

"URL" or "Max" radar product (see Part II above) everywhere within the corresponding square (defined 

above) is less than 10 dBZ-km divided by the average cloud thickness in km within the same square (see Part I 

above). (In English units, this threshold would become 33 dBZ-kft divided by the average cloud thickness in 

kft.) This constraint must be satisfied for every point on the flight track.
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Appendix II A Detailed LAP/LLCC Chronology 1991 – 2009

(Provided by John Willett)

The following sources were used to create this chronology of LAP deliberations and resulting LLCC changes:

1) A collection of Shuttle LLCC versions compiled for this purpose by John Madura.

2) All available LAP-published and/or formally recommended LLCC versions.

3) Meeting and teleconference notes from John Willett's files, supplemented by some input from other 

authors of this document.

All significantly changed LLCC sets are indicated by their release date, name as used throughout this 

document, LCN number, and Appendix I reference, beginning with the first release in 1991, LCN 00048 

released on 01/28/91, immediately below. (Changes applying only to non-lightning LCC, as well as trivial 

changes of the LLCC themselves, are omitted.) For each such new LLCC set, the significant changes from the 

previous version are briefly described. (The full text of the LLCC versions are not given here -- see the 

references given to Appendix I.) Whenever possible, significant meetings, telecons, and publications by the 

LAP are also indicated by approximate date and described as to subject matter and important conclusions 

reached or recommendations made.

Note that the operational Shuttle rules that are primarily analyzed herein have never contained a 

Triboelectrification Rule, although it has been included in the PRC/LAP recommendations since at least 12 

May 1995, reportedly because the Shuttle was already hardened against triboelectric charging. Reportedly a 

Triboelectrification Rule was included in all versions of the ELV LLCC since AC 67, but we have not 

attempted to distinguish between ELV and Shuttle rules in this appendix.

An Electric Fields Aloft Rule, originally recommended by Heritage (1988, Section 7.2) and continually 

endorsed by the PRC from 11 March 1994 through at least January 1999, has never been included in any 

operational rules since ASTP and Viking. See Section 5.5.6 for more on this topic.

28 January 1991 -- Space Shuttle LLCC (1991) [LCN 00048, see Appendix I, Section A1.9.1]. This is our 

starting point for future rule comparisons in this appendix. Many of these LLCC are similar or identical to the 

recommendations of Heritage (1988, Chapter 7) (see Appendix I, Section A1.8). Here we briefly indicate the 

important differences:

The Field-Mill Rule (C):

This rule appears to use a different definition of Electric Field Intensity. The Heritage 

Committee specified "the absolute value of the 1-minute time average of the instantaneous, 

ground-level electric field intensity." The present rule, on the other hand, refers to "the one 

minute average of absolute electric field intensity at the ground." (See also the entry for 25 

April 1995, Space Shuttle LLCC (1995) [LCN 00520R03] below.)

The present rule replaces the second part of the original Heritage-Committee exception 

(involving electric-field measurements aloft) with "Smoke or ground fog is clearly causing the 

abnormal readings."

The present Debris-Cloud Rule adds both an overall three-hour-after-detachment exception and a 

field-mill/radar-reflectivity exception to the 5 NM standoff.
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The Heritage Committee's electric-fields-aloft exceptions for penetration of Cumulus Clouds warmer 

than -20 C (B1 and B2), for the 10 NM standoffs from Thunderstorms or Cumulus Clouds colder than 

-20 C (B3 and B4), and for the Debris-Cloud, Disturbed Weather, and Thick Cloud Rules (F, E, and D, 

respectively) have been eliminated. [See the PRC's attempt to re-institute parts of this exception in the 

entry for 15-17 February 1994 and in Koons and Walterscheid (1996).]

The Heritage Committee's Triboelectrification Rule has been dropped. [One of the LAP's attempts to 

document this rule can be found in Krider et al. (1999).]

23 Oct 1991 -- A telephone conference involving most current members of the LAP (then, PRC, including at 

that time Dye, Koons, Krider, Rust, Walterscheid, and Willett) was called by Jack Ernst and Bill Bihner 

(NASA/WSO) to consider relaxing the Surface-Field Rule (C). The telecon was held in the form of a vote on a 

specific change proposal that, not surprisingly, was defeated.

Discussion, apparently all by telephone and fax, continued through the winter, however. The help of the 45th 

WS was solicited and obtained in gathering supporting data, and the change below eventually evolved. This 

precedent began a push to enumerate specific exceptions in which a known, near-surface, electrification 

mechanism could be identified as responsible for elevated field readings. Eventually (see entry for Fall of 

1996), Dave Rust and Tom Marshall (University of Mississippi) were involved in obtaining near-dawn field 

profiles with a tethered balloon to document a shallow layer of enhanced field that was apparently caused by a 

"sunrise effect." This eventually worked its way into a version released on 12 May 1997 [LCN 00765R03] 

(further below).

20 March 1992 -- Space Shuttle LLCC (1992) [LCN 00230R04, see Appendix I, Section A1.9.2]. Minor 

Change:

First introduction of the term, "transparent," without a definition, into the body of the rules. Here it is 

included in a "note" relative to rule C(1). ("Transparent" had previously been included only in the 

definition of "anvil.")

Added two new "notes" to the Surface-Field Rule (C):

C(1) "Unless there are no clouds within 10 nautical miles of the launch site" has been relaxed 

to allow "thin fibrous (optically transparent) clouds" or "less than or equal to 2/8... 

(CU/SC/ST) clouds with tops below or equal to the +5 degree Celsius temperature level," as 

long as they have not been associated with a thunderstorm or CU with tops higher than -10 C 

in the last 3 hr.

C(2) "Unless smoke or ground fog is clearly causing abnormal readings" has been relaxed 

provisionally, pending more data, to also allow "a maritime inversion" that causes affected 

mills near the ocean to read between +1 and +1.5 kV/m.

3-5 August 1992 -- MSFC's analysis of their summer ABFM I dataset resulted in proposed changes to the 

existing LLCC, and Jack Ernst and Bill Bihner (NASA/WSO) organized a face-to-face meeting of the PRC at 

MSFC to consider them. The PRC signed off on a revised set of rules (outlined below), which were apparently 

never implemented, and took the opportunity to go on record that "we believe the best way to insure safety 

from atmospheric electricity hazards, and also to improve launch availability, is to utilize an instrumented 

aircraft in conjunction with the ground-based field mill network to measure the electric field environment and 

its time development along and near the flight path." Significant changes that were adopted by the PRC were 

the following:
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A "relative to" exception to cumulus clouds with tops colder than +5 C (B1) that allows penetration if 

both their radar reflectivity is low and they are verified safe by at least one nearby field mill.

A "relative to" exception to cumulus clouds with tops colder than -10 C (B2), that would allow flight 

between 3 and 5 nm from the visible edge if they were verified safe by the ground-based field-mill 

network, was proposed but not adopted, pending additional data. (This exception was eventually 

rejected.)

One of the "relative to" exceptions to no clouds within 10 nm in the presence of elevated fields (C1) 

was changed from "thin fibrous (optically transparent) clouds" to simply "optically transparent 

clouds."

The "relative to" exception to smoke's or ground fog's clearly causing elevated fields (C2), which had 

allowed surf and/or maritime-electrode-effect charge, was deleted. The PRC reminded NASA that this 

exception had been originally approved as an interim measure while further research was done on the 

phenomenon, that no new information had been forthcoming, and that recalibration of the field mills 

had recently eliminated most of the problems with this phenomenon.

Several new definitions were added, and "Debris Clouds" was significantly revised.

There was discussion of substituting the "signed one-minute average of the instantaneous electric 

field," plus the RMS deviation around that average, for the existing "one minute average of the 

absolute electric field" in both the rules and the measurement software, but this was deferred and never 

done.

Concern was expressed that the 10-4 acceptable level of risk that was desired for Shuttle by 

NASA/WSO might never be reached using ABFM data.

During 1993 several telecons were conducted (15 April 1993, 18 June 1993, 22 November 1993) regarding a 

MSFC proposal that was based on the full ABFM I dataset, now including the winter campaign. MSFC wanted 

to replace the thick-cloud and disturbed-weather rules (D & E) with a single, radar-based rule involving a 

threshold in vertically summed reflectivity ("VIR4"). Aerospace statisticians, working with the USAF, found 

that the available data did not justify the proposed new rule, and it was ultimately rejected by the PRC. 

Nevertheless, MSFC did convince the PRC that some form of radar rule was warranted, given a better 

statistical justification, and that such a rule could be very effective in reducing false alarms.

15-17 February 1994 -- A face-to-face PRC meeting was called by NASA at KSC. On the table was a 

NASA/MSFC-proposed set of rules containing several changes from the version approved by the PRC on 3-5 

August 1992 (but never implemented). Notable were the reduction of standoff distances for B3, B4 and C1 

clouds from 10 nm to 8 nm (which the PRC had previously questioned), retention of the exception relative to 

C(2) for a maritime inversion (which the PRC had specifically removed in 1992), replacement of the thickcloud rule (D) with a radar rule involving VSR0C (a revised, vertically summed radar parameter), and 

specification of a radar threshold of 29 dBZ for "moderate or greater precipitation." Ultimately these four 

specific proposals were all rejected. There was also a wide-ranging discussion of a number of topics, some of 

which are mentioned below, which resulted in an extensive list of recommendations, both by and for the PRC. 

These recommendations were summarized in an 18 February 1994 letter from John Willett to Harry Koons.

The 45th WS (USAF) raised significant concerns about complexity, ambiguities, and inconsistencies 

in the LLCC and offered a number of suggested changes.
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The PRC was asked to consider the flight rules for Shuttle, which are maintained and enforced at 

NASA/JSC/SMG.

Also at this meeting John Madura first formally presented data on the fraction of ELV scrubs due to 

various causes -- 32% due to weather -- and the fraction of weather scrubs for all vehicles that were 

due to various causes -- 38% due to LLCC.

Led primarily by Harry Koons, the PRC undertook a complete rewrite of the LLCC, primarily to 

address issues of clarity and ambiguity. By 11 March 1994 the PRC had signed off on a new LLCC 

version (Jim Dye apparently attended this meeting but was not a signatory on this document. Jim left 

the PRC somewhere around this time.) Noteworthy was the adoption of a new "Rule G," similar to a 

rule originally proposed by the Heritage (1988, Section 7.2). Rule G, as written, permitted exceptions 

to the thick-cloud, disturbed-weather, and debris-cloud rules (D, E, and F) if an operational ABFM 

showed no fields higher than a specified, altitude-dependent threshold along and near the flight path 

within the prior 15 minutes. This proposed version is documented by Koons and Walterscheid (1996 --

see entry for 1 February 1996, below, and Appendix I, Section A1.9.3) and was similar to the 

implemented version, "25 April 1995, Space Shuttle LLCC (1995) [LCN 00520R03]," listed below,

except for the omission of "Rule G" and some major issues discussed with reference to John Madura's 

12 May 1995 letter (below). Surprisingly it did not contain a triboelectrification rule.

6 October 1994 -- A PRC telecon reviewed and either approved or requested more information about several 

changes proposed by NASA/USAF. Available records do not indicate whether any of these proposals were 

adopted by the PRC.

12 May 1995 -- John Madura circulated a letter containing new rules ("25 April 1995, Space Shuttle LLCC 

(1995) [LCN 00520R03]," below) that had apparently already been implemented on the NASA side but may 

have been still pending on the USAF side.

This letter unleashed a fire-storm of protest from the PRC for several reasons:

"Rationales" had been added to the rules, apparently as part of the rules proper, without PRC 

knowledge or review. These rationales were felt to introduce the opportunity for ambiguity 

with, if not outright contradiction of, the carefully worded language of the rules. Further, some 

of these rationales were seen as misleading or incorrect.

The "note" at the end of the field-mill rule (C) was new to the PRC and appeared to contradict 

their intent with respect to failures of individual field mills.

The ABFM rule (G) had been dropped, apparently because no suitably instrumented aircraft 

was available, its cost effectiveness had not been established, and/or no detailed operations 

plan for its use had been worked out.

The triboelectrification rule had been dropped on the NASA side as irrelevant to Shuttle, 

although it was apparently still maintained on the USAF side.

A new definition of "documented" had been added without PRC knowledge or review 

(although it seemed basically OK).

All of this led to an official "letter of concern" from the PRC at the end of June of 1995. It also led to 

the PRC's raising the question of what its ongoing role might be in the rule-making process. Could an 
Page 147 of 234

official charter be created and a definite membership established? Finally it was probably the 

motivation behind the Aerospace LLCC report -- see 1 February 1996, below.

25 April 1995, Space Shuttle LLCC (1995) [LCN 00520R03, see Appendix I, Section A1.9.4]. -- MAJOR 

Change (more in the way of a reorganization and clarification than a substantive relaxation):

Wholesale introduction of the term, "nontransparent," into several rules (B(3), B(5), and F(1), as well 

as retaining it in C(1)). Now it is defined in the Definitions.

Numerous minor wording changes throughout (e.g., "launch site or planned flight path" was replaced 

with "flight path"); only substantive changes are noted below.

"Rationale" (not written nor reviewed by the LAP) were added to each of the rules IN ALL CAPS.

Cumulus Cloud Rule (B):

B(1) "Through cumulus clouds with tops higher than the 5 degrees Celsius level" has been 

separated into two temperature ranges. Between +5 and -5 C penetration is now allowed if 

three conditions are satisfied (the cloud is not precipitating, a working field mill is close 

enough to the cloud, and the relevant mill readings are between -100 and +1000 V/m). 

(Between -5 and -10 C penetration is still prohibited.)

B(3) "Cumulus clouds with tops higher than the -20 degrees Celsius level" has been replaced 

with "cumulonimbus or thunderstorm cloud, including nontransparent parts of its anvil." 

"Thunderstorm" is now defined as "any cloud that produces lightning." "Transparent" (but not 

"nontransparent") and "anvil" are also now defined. ("Cumulonimbus cloud" was already 

defined in terms of the -20 deg. C level.)

B(5) has been added to prohibit flight within 10 NM of a nontransparent detached anvil for the 

first 3 hr after detachment.

A "note" has been added excluding Altocumulus or Stratocumulus from this rule.

Field Mill Rule (C):

The reference to "launch site" in the body of this rule has been replaced with "flight path."

The traditional phrase, "the one minute average of absolute electric field intensity," in the 

body of the rule has been replaced with "the absolute value of any electric field intensity 

measurement," and a new definition of "Electric Field" now specifies "the one-minute 

arithmetic average of the vertical electric field." This would appear to be a substantive 

change from the average of the absolute value to the absolute value of the signed average.

In place of the cumbersome "Relative to..." "notes" at the end of the rule, formal exceptions 

have been added as follows:

C(1) "Thin fibrous (optically transparent) clouds" has been replaced with "transparent 

clouds," and "less than or equal to 2/8 cumulus/stratocumulus/stratus (CU/SC/ST) 

clouds" has been replaced with "clouds."
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C(2) "Smoke or ground fog is clearly causing abnormal readings," including a 

maritime inversion via the "note," has been generalized to "a known source of electric 

field (such as ground fog)... previously determined and documented to be benign, is 

clearly causing abnormal readings." A lengthy and detailed definition of 

"documented" has also been added.

Disturbed Weather Rule (E): "Are associated with disturbed weather within..." has been expanded to 

"are associated with disturbed weather that is producing moderate (29 dBZ) or greater precipitation 

within..." The previous definition of "disturbed weather" has been deleted.

Debris Cloud Rule (F) has been clarified and slightly relaxed via introduction of several more 

sections:

F(1): "Do not launch through thunderstorm debris clouds" has been expanded to "Do not 

launch... through any nontransparent thunderstorm or cumulonimbus debris cloud..." The 

definition of "Debris Cloud" has also been clarified to explicitly include the decay of a parent 

CB or TRW.

F(2): "...or within 5 nautical miles of a thunderstorm debris cloud not monitored by a field mill 

network or producing radar returns greater than or equal to 10 dBZ" has been separated into 

three sections (a, b, and c) that specify explicitly what is meant by "monitored" and clarify 

what is meant by "producing a radar return."

Two definitions have been deleted, four retained with changes, and eight new ones added.

The two all-caps paragraphs at the end, which could be considered a rudimentary rationale, have been 

removed, presumably because they were subsumed into the newly written rationales for each rule.

1 February 1996 -- Publication of Koons and Walterscheid (1996) documents the rule version that was 

formally adopted by the PRC in March 1994, without any of the subsequent tweaks. The plan was to issue a 

new version in this report series each time the PRC approved a new rule revision, although only one such new 

version has been forthcoming to date -- see entry for 15 January 1999. This report lists the full membership of 

the PRC as Dye, Koons, Krider, Rust, Walterscheid, and Willett. It does not include a triboelectrification rule.

Summer of 1995, Summer and Fall, 1996 -- As recommended by the PRC during its 15-17 February 1994 

meeting, experiments were conducted at KSC to study the conditions that had been causing "benign" 

violations of Rule C (elevated fair-weather electric fields at the surface) in apparently good weather.

Phil Krider [Studies of atmospheric electricity at the NASA Kennedy Space Center, Progress Report 

and a Supplemental Proposal for Grant NAG10-0092, 9 January 1996; Studies of atmospheric 

electricity at the NASA Kennedy Space Center (KSC) and the USAF Eastern Range (ER), Progress 

Report and Supplemental Proposal for Grant NAG10-0092, 24 February 1997] surveyed the electricfield distribution downwind from the surf zone and from high-voltage power lines, recorded electricfield enhancements during fog, and studied the electric-field and space-charge behavior during the 

"Indian River anomaly," or "sunrise effect." The only conditions suggested to be of possible concern 

were the elevated fields that sometimes occur near high-elevation, high-voltage power lines during 

persistent ground fog.

Marshall et al. (1999) made electric-field soundings with a tethered balloon to study the above 

"sunrise effect." They found that in the fields aloft are not as big as those at the ground and that 

enhanced fields extended less than 150 m above ground.
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Based on the above reports, several of the potential sources of elevated fields in fair weather were 

characterized, if not fully understood, and were determined to be benign. This determination was 

based on the limited vertical extent and/or local source of the phenomena.

6 September 1996 telecon -- preliminary look at the Marshall and Rust balloon soundings of "sunrise effect."

Dave Rust reported that the fair-weather atmosphere was not repeatable, and that there have been no 

events above 1 kV/m although several above 500 V/m have occurred. The “effect” takes about an 

hour. Pre-sunrise there is a layer about 10m deep with fields near 100 V/m. At sunrise the charge 

density lowers and the sunrise layer deepens to about 300m. Typically less than 200 V/m. We don’t 

understand the physics. Dr. Krider noted that these observations were consistent with his aspirator 

measurements of the charge density. Thought totally harmless to launches. Paul Krehbiel concurred. 

Speculations on possible mechanisms were offered by Rust and Merceret. Tom Marshall and Krider 

agreed that more data analysis was required. Additional discussions were held regarding the 

definitions of “fair weather” and “documented.”

19 November 1996 telecon -- reviewed Marshall and Rust data/interpretation from tethered-balloon soundings 

in the "sunrise effect."

4 February 1997 -- LAP meeting at Aerospace Corp. in Los Angeles:

The current PRC members (Krider, Koons, Rust, Walterscheid, Willett) agreed to a charter for the renamed Lightning Advisory Panel (LAP), drafted by an "Interagency Review and Coordinating

Committee" (IRCC, made up of 45WS, 30WS, KSC Weather Office, SMG, and AFMC/SMC), which 

appoints the LAP's members, renews its charter every three years, and to whom it reports.

Proposed exceptions to Rule C (surface fields) were discussed. It was agreed to allow specific 

exceptions for benign smoke, ground fog, and sunrise effect, with the provision that the elevated fields 

were positive and did not exceed 1500 V/m. Documentation was drafted and approved, defining each 

of these conditions and specifying how they could be recognize operationally.

Further discussion of a radar-based replacement of the thick cloud rule (D) was inconclusive because 

of lack of reliable radar data.

Harry Koons expressed concern about the potential vulnerability of space-launched payloads to sprite 

electric fields in the middle atmosphere.

12 May 1997 [LCN 00765R03] (not included in Appendix I) -- Minor Change:

In the Field Mill Rule (C), a parenthetical sentence has been added to C(2) pointing to the location of 

documentation relevant to benign ground fog, smoke, and sunrise effect.

8-9 January 1998 LAP Meeting in Tucson:

LAP charter was still under revision and had not yet been approved by IRCC.

First major participation of 45WS in the LAP process: 45WS proposed LLCC that were significantly 

reorganized (and to some extent changed in content) from the LAP original, and they requested 

clarification of (or changes to) the existing language/definitions. (The triboelectrification rule appears 

in their revision.) This degree of involvement was welcomed by the LAP, as it provided valuable 

feedback on the operational interpretation and usefulness of the rules. The basic idea of the 45WS 
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reorganization appeared sound, but some of the original nuances were lost, leading to changes in 

content and indicating lack of understanding of the original intent. As a result the LAP undertook 

another major re-write of the rules.

John Willett and Mike Maier both presented estimates of the cost savings that might accrue from an 

operational ABFM. Although historical data on the cause of launch scrubs/delays is reliable, 

information on the cost of such scrubs/delays probably is not, and requests to log the frequency of rule 

violations (in the absence of actual launch countdowns) have not been successful.

It appears to have been in this meeting that the LAP decided to eliminate the "known cause" exception 

from Rule C (along with the "documentation" for benign smoke, ground fog, and sunrise effect), in 

favor of raising the field threshold to |1500 V/m|.

27-29 April 1998 LAP Meeting at KSC: 

LAP charter was still under revision and had not yet been approved by IRCC.

This meeting was devoted primarily to working out the open issues in an LLCC version that had been 

drafted after the January meeting.

Issues involving the ground-based field-mill network were also addressed -- especially a gain shift and 

associated failure of the self-checking feature, use of measured (as opposed to interpolated) values, 

and maintenance of the sites.

6 May 1998 LAP Telecon: John Madura had applied considerable pressure to the LAP on 1 May by reporting 

that Don McMonagle (Shuttle Launch Integration Manager) wanted "the final fully staffed version [of the 

LLCC] briefed at the STS 91 Flight Readiness Review on 20 May." This began a frantic effort, documented in 

a flurry of e-mails and at least seven more revisions, both before and after this telecon, extending through the 

20 May deadline. The final LAP-approved version ("LCC-K2.doc," distributed Wed 5/20/1998 10:41 AM 

EDT) is documented in the second Aerospace LCC Report -- see entry for 15 January 1999, below. 

Astonishingly (considering the extreme time pressure) this LAP-approved version differs from operational 

revision 824R03 (below) in only two significant ways:

Proposed Rule 9 (Electric Fields Aloft -- the old "Rule G") and its corresponding definition still are 

not included in the operational version.

Proposed Rule 10 (Triboelectrification) also is not included in the operational version.

4 June 1998, Space Shuttle LLCC (1998) [LCN 00824R03, see Appendix I, Section A1.9.5] -- MAJOR 

Change: Complete re-write of the rules to clarify and improve logic. Here we identify only the substantive (as 

opposed to the formal wording) changes:

All rationale have been eliminated from the rules.

Use of the term, "nontransparent" has been further extended to Rules 2(b), 8(b), 6, and 5.

Lightning Rule (A) has been split into two parts and made more explicit as follows: "...any type of 

lightning is detected... unless the meteorological condition that produced that lightning has moved 

more than 10 NM away from the flight path" has been divided into two parts:
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1(a) "...any type of lightning occurs in a thunderstorm... within 10 NM of that thunderstorm" 

(i.e., it's the thunderstorm that is to be avoided), and 

1(b) "...any type of lightning occurs within 10 NM..." (i.e., it's the lightning itself that is to be 

avoided), unless two conditions are satisfied to assure that that lightning did not deposit 

significant charge near the flight path.

Two "notes" are added to assure that any cumulus that remain after 1(a) are covered under the 

Cumulus Rule (2), and that anvils are covered under the new Anvil Rule (3) -- see below.

Cumulus Rule (B): This rule has been completely re-ordered, but the only substantive changes are as 

follows:

B(1) becomes 2(d), in which the three "unless" requirements are changed in two ways:

The horizontal distance between the cloud and the nearest working field mill has been 

changed from "from the farthest edge of the cloud top... is less than the altitude of the 

-5.0 deg. C level or 3 NM whichever is smaller" to "from the center of the cloud top... 

is less than 2 NM."

The allowable range of field measured at the relevant mills has been narrowed from (-

100 V/m and +1000 V/m) to (-100 V/m and +500 V/m).

B(4) becomes 2(b), in which "cumulonimbus or thunderstorm cloud, including nontransparent 

parts of its anvil" has been replaced with "cumulus cloud with its cloud top higher than the -20 

deg C level."

B(5) has been dropped entirely. The obvious intent of the LAP was that anvils (either attached 

or detached) are not to be covered by this rule.

Field Mill Rule (C) has been re-ordered and relaxed to become (8):

C(1) (no launch for 15 min after 1000 V/m readings at relevant mills) has become 8(b), the 

only change being that the second "unless" condition (clouds lower than +5 °C not associated 

with towering CU) now also refers only to nontransparent clouds.

C(2) (known sources such as ground fog) has been replaced with 8(a), which now prohibits 

flight only if the relevant field readings are above |1500 V/m|.

Thick Cloud Rule (D) has been re-ordered to become (6) and has been clarified and relaxed as follows:

Launch through transparent parts of the cloud layer is no longer prohibited.

6(1) This section appears to prohibit launch through parts of the cloud layer that are both

>4500 ft thick and contain temperatures between 0 and -20 °C.

6(2) This section prohibits launch through a cloud layer that is connected to a layer that is 

both >4500 ft thick and contains temperatures between 0 and -20 °C within 5 NM of the flight 

path.
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An "unless" clause has been added to the entire rule that exempts cirriform clouds that have 

never been associated with convective clouds, are entirely colder that -15 °C, and show no 

evidence of liquid water.

Disturbed Weather Rule (E), now (5):

A definition has been added for a "weather disturbance."

Now applies only to nontransparent clouds.

The radar threshold for "moderate precipitation" has been moved to a new definition of that 

term and increased slightly to 30 dBZ.

In addition to "moderate precipitation" the penetration prohibition has been extended to "a 

radar bright band or other evidence of melting precipitation." A new definition is added for 

"bright band."

Debris Cloud Rule (F) has been re-ordered to become (4): This rule has been substantially re-worded, 

but the only substantive change is to relax an "unless" condition from F(2)(c) "the maximum radar 

return from the entire debris cloud is less than 10 dBZ..." to 4(b)(3) "the maximum radar return from 

any part of the debris cloud within 5 NM of the flight path is less than 10 dBZ..."

Anvil Rule (3): This completely new rule has been added to cover and extend parts of previous rule 

sections, B(4) and B(5).

3(a) Covers attached anvils in place of the previous practice of considering them as part of the 

CB in B(4). This allows the rule for attached anvils to be made less restrictive than that for 

CBs, as follows:

3(a)(1) The former prohibition on penetrating non-transparent, attached anvils is 

retained, but

3(a)(2) flight between 0 and 5 NM is allowed 3 hr after the last lightning discharge in 

the storm, and

3(a)(3) flight between 5 and 10 NM is allowed 30 min after the last lighting.

3(b) covers detached anvils, in place of the previous B(5). This allows the rule for attached 

anvils to be fine-tuned. relative to that for CBs, as follows:

3(b)(1) The prohibition against penetration has been made more restrictive by 

increasing the waiting time from 1 hr to 3 hr (although after 1 hr a detached anvil 

might formerly have been considered a debris cloud and therefore still had the 3 hr 

prohibition.

3(b)(2) An entirely new requirement has been added not to penetrate a detached anvil 

for 4 hr after its last lightning discharge.

3(b)(3) The prohibition against flight between 0 and 5 NM has also been made more 

restrictive by increasing the waiting time from 1 hr to 3 hr unless three conditions are 
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met, requiring adequate monitoring by at least one field mill and a radar return from 

the relevant portions less than 10 dBZ for 15 min. 

3(b)(4) The prohibition against flight between 5 and 10 NM has been relaxed by 

decreasing the waiting time from 1 hr to 30 min, but a lightning discharge in the 

parent cloud resets the clock.

It is explicitly stated that detached anvils are never to be considered debris clouds.

A totally new Smoke Plume Rule (7) prohibits launch through any CU that has developed from a 

smoke plume until 60 min after detachment. After 60 min the CU is covered by Rule 2.

Two of the previous definitions have been deleted or replaced, some of the others have been reworded, and six totally new definitions have been added. The substantive changes are the following:

"Electric Field Measurement at the Surface" now explicitly requires the use of a ground-based 

field mill.

The radar threshold for "precipitation" (which replaced "precipitating cloud") has been raised 

from 13 dBZ to 18 dBz.

"Transparent" has been significantly changed to require visible assessment of transparency. A 

separate definition of "nontransparent" has also been introduced (which causes confusion later 

on).

15 January 1999 -- Publication of Krider et al. (1999) documents the rule version formally adopted by the LAP 

in May 1998. This report is the second (and currently the last) in a series intended to document each new rule 

revision that was approved by the LAP -- see previous entry for 1 February 1996. This report lists the full 

membership of the LAP as Koons, Krider, Rust, Walterscheid, and Willett. It includes both "Electric Fields 

Aloft" and "Triboelectrification" rules.

22-25 February 1999 LAP meeting at NASA/JSC in Houston -- Topics Covered in Depth:

Consider whether the Flight Rules protect the orbiter during landing. The LAP was briefed in detail on 

the flight rules and some of SMG's concerns. (It is not clear that the LAP ever submitted any coherent 

response to SMG.)

30WS and 40WS asked for and (mostly) received clarification of a number of details in the latest 

LLCC re-write (4 June 1998, Space Shuttle LLCC (1998) [LCN 00824R03], above). Open issues were 

held over to the next rule re-write.

Reports of sporadic reduced sensitivity on field mills in the LPLWS led to considerable LAP concern 

and to several recommendations for diagnosis and correction of the problem.

Preliminary planning of another ABFM II campaign specifically to develop radar/cloudphysics/electric-field relationships for development of new radar-based LLCC. Conclusion: conduct a 

workshop to plan that campaign in detail.

Hugh Christian became a new LAP member.
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It was pointed out that the Federal Advisory Committee Act (FACA) would seriously cramp the LAP's 

style if it were constituted as an official advisory committee. LAP should consider becoming chartered 

under FACA as a subcommittee of one of the NASA Advisory Council committees.

1 December 1999 -- The LAP issued a formal recommendation to the KSC Weather Office for an ABFM II 

campaign to "validate physics-based relationships between the decay of cloud electric fields and cloud 

properties and to verify that these cloud properties, and also the presence of electric generators aloft, can be 

inferred from ground-based measurements."

25-28 January 2000 LAP Meeting at KSC:

The first planning meeting for the ABFM II Campaigns. (ABFM II is treated in detail elsewhere, but 

certain key ABFM II meetings are also listed herein because oversight of the experiment and the 

resulting data analysis was a LAP function.)

Discussion of Kodiak Launch Complex launch rules and measurements: Incredibly high surface 

electric fields had been observed during brief graupel showers from very shallow clouds.

Miscellaneous follow-up of action items from the 22-25 February 1999 LAP meeting: More 

information about LPLWS sensitivity decreases -- apparently mainly along the coast, associated with 

high humidity, and not reliably detected by the self-calibration function unless greater than about 25%. 

(It is not clear that this issue was ever resolved satisfactorily.)

12 February 2001 -- A letter of concern was sent by Phil Krider, in his capacity as LAP chairman, to the DOT 

Document Management System regarding new FAA-proposed "Lightning Flight Commit Criteria (LFCC)" --

Part 417, Appendix G, of Docket Number FAA-2000-7953. Harry Koons had been working with FAA/AST on 

their "translation" of the current LCC into FAA jargon, and he reported the inevitable changes in intent that 

had resulted. This was to become a major concern for the LAP over the next few years, with the eventual 

decision that the LAP should attempt to write its new rule versions in "FAA language," specifically to 

minimize editing by the FAA lawyers (see, for example, the entry for 6 October 2008, LAP 10/06/08 

Recommendation in FAA Format).

31 August 2001 LAP telecon on launch rules at Kodiak. The LAP decided to draft some provisional "LLCC" 

specifically for Kodiak and discuss them in a second telecon.

5 September 2001 LAP telecon to mark up provisional "orographic" and disturbed-weather launch rules for 

Kodiak, which were submitted the same day as recommendations to the KSC Weather Office.

September 2001 through April 2008 -- Numerous ABFM II and joint LAP/ABFM II Telecons were conducted 

throughout this period. Only the actual meetings and telecons having significant results will be reported below.

27-28 November 2001 -- ABFM II Workshop at the Melbourne, FL, offices of ENSCO, Inc.:

Doug Mach and Bill Koshak reviewed A/C calibrations techniques and results at length.

Monte Bateman reviewed radar (WSR74C vs. NEXRAD) inter-comparisons.

Jim Dye, Eric Defer, and others reviewed status of the NCAR/ABFM Web site and some particularly 

interesting special cases.

Jim Dye began synthesis of particle concentration vs. field intensity in anvils.
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John Willett reported on a theoretical approach to, and initial calculations of, field-decay times in 

anvils.

The LAP should be invited to the next ABFM II meeting as observers.

10 January 2002 ABFM II Telecon --

Hugh Christian officially transferred the title of Principal Investigator to Jim Dye.

Significant radar attenuation due to intervening precipitation was noted late on 10 June 2001: An 

attenuation warning should be included explicitly in next LLCC revision.

21 February 2002 ABFM II Telecon --

Monte Bateman argued for "vertically integrated reflectivity above 5 km (~0 C)" as a likely radarthreshold parameter for significant electrification.

Frank Merceret emphasized that an LLCC result is needed from ABFM II before the end of FY03 to 

meet funding commitments.

7 March 2002 ABFM II Telecon --

Beware radar geometrical cut off at low altitudes/long ranges.

26 March 2002 LAP Telecon -- The NASA/MSFC Altus Cumulus Electrification Study (ACES) experiment 

plan was outlined. MSFC requested LAP review of its lightning-strike avoidance plan.

4 April 2002 ABFM II Telecon --

Frank Merceret reported on attenuation due to wet radome.

Jim Dye advanced his conceptual model that strong fields are present when radar reflectivity is 10-15 

dBZ or greater but that the converse is not true.

12-14 November 2002 -- Joint LAP/ABFM II Workshop at the Melbourne, FL, offices of ENSCO, Inc., to 

review the progress to date in data reduction and analysis and to discuss its applicability to modification of the 

LLCC. (Here we summarize only the LAP recommendations made in response to the progress review. For 

more information, refer to "Nov '02 Workshop/Workshop Summary" on the "Reports" page at 

"http://abfm.ksc.nasa.gov/".) John Willett's Summary of LAP Recommendations (edited and reported by 

Frank Merceret) follows:

1) The ABFM Analysis Team (AAT) urgently needs a final conclusion from the MSFC group about 

which analysis algorithm, the Mach (M) algorithm, the Koshak (K) algorithm, or a combination of 

these algorithms (under what conditions), should be used to provide the best estimate of the ambient 

electric (E) field in clouds that were sampled during the ABFM campaign.

2) The AAT should "sanitize" the cloud E-field/radar-parameter dataset so as to minimize the effects 

of the following: [These later evolved into a set of "filters" that could be applied, individually or in 

combination, to the full dataset in order to remove undesirable cases.]
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A) Nearby lightning as a non-local source of the field -- use a 10 nm (18 km) standoff distance 

(the same as used in LCC Rule 1) and a standoff time TBD by the AAT;

B) Nearby cores of active thunderstorms that represent non-local sources of electric field –

using altitude/radar thresholds and standoff distances TBD by Analysis Team;

C) Radar scan gaps, to the extent that they significantly influence the various radar 

parameters; and

D) Wet-radome and/or precipitation-attenuation effects, to the extent that they significantly 

influence the various radar parameters.

3) Further explore the cloud reflectivity parameters (e.g., peak dBZ, average Z, average dBZ, box size) 

so as to optimize the potential relationships to ambient E-field in the "sanitized" dataset. Focus the 

analysis on thunderstorm anvils, thick clouds, and disturbed weather.

4) Further "sanitize" the cloud E-field/decay-time dataset so as to minimize, in addition to the effects 

listed in (2) above, any indications of a local electrical generator (i.e., radar indications of local 

development of the cloud, TBD by the AAT).

5) Pursue, to the greatest practical extent, testing of the E-field-decay model using the measured cloud 

microphysical parameters and observed field decays. For this, we also need better estimates of the 

ambient winds and the parcel trajectories in anvils.

6) Look for relationships between the predicted decay times and the associated radar reflectivities in 

the further "sanitized" dataset detailed in (4) above. Determine whether there are other types of radars 

(or ground-based sensors) that could serve as a proxy for the decay time of the cloud electric field.

7) Check ALL anvils for the presence of liquid water.

8) Archive all data obtained in the current ABFM campaign (ABFM II).

9) Retrieve and, to the extent possible, archive data obtained during the previous ABFM campaign 

(ABFM I).

10) Integrate the ABFM I dataset with the ABFM II dataset in a coherent way. This may require recalculating some of the radar parameters in ABFM II so that they match those previously calculated 

during ABFM I.

11) Re-examine in detail any specific cases that appear to be of concern in the ABFM I scatterplots.

8 January 2003 ABFM II Telecon -- An action item to use M-derived E fields only and to modify the quality 

control to set a flag if aircraft charge (presented in the same units as the electric field) is a factor of 10 or more 

larger than E.

6 March 2003 ABFM II Telecon -- Result of Frank Merceret's study of reflectivity averaging: Averaging of 

reflectivity measured in dBZ is strongly preferred to averaging in units of Z. Averaging the reflectivity before 

taking the logarithm results in a product excessively dominated by non-representative peak values.
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12-15 May 2003 -- Joint LAP/ABFM II Workshop at the Melbourne, FL, offices of ENSCO, Inc.:

The ABFM II analysis was well along, although the team still hadn't selected the "best" radar 

parameter, nor the final suite of "filters" to remove cases clearly eliminated by other LLCC. Topics 

included an overview of the database and considerable discussion of individual cases, of the time-offlight estimates vs. model decay times (including early indications of "redevelopment" of 

microphysics and electric fields within certain anvils), and of field-magnitude scattergrams for various 

radar parameters.

The LAP considered taking positions on these and other issues. Examples of key LAP 

recommendations are:

Frank Merceret and Jennifer Ward should correlate their objective determination of cloud 

edge with both visible transparency and radar reflectivity. (Results of this investigation were 

published in the January-February 2006 issue of J. Spacecraft and Rockets. They showed 

consistency among the cloud-physical, 0 dBZ radar, and visibly non-transparent estimates of 

"cloud edge.")

Harry Koons should apply "extreme-value analysis" to whatever scattergram(s) is (are) 

selected as most promising. This kind of analysis could replace the application of large safety 

margins (e.g., 20 dB) to the observed extreme values.

IMPORTANT: The cloud boundaries should be redefined uniformly in terms of the 0 dBZ 

reflectivity contour, based on some ABFM data showing fields > 3 kV/m with reflectivities < 

10 dBZ (the radar definition of cloud edge in the then-current LLCC).

A capability to display volume-averaged or -integrated radar parameters should be 

implemented for the Launch Weather Officers (LWOs) in the Range Control Center (RCC). 

This recommendation was embodied in a 20 May 2003 memo from the LAP to Col. Wyse, 

Commander, 45WS.

Frank Merceret should use the existing "merged" ABFM II data files to test the effectiveness 

of including more than one predictor for field magnitude.

The NCAR team should develop and apply a subjective filter to remove cases that are within 

10 nm of convective cores -- towering cumulus and cumulonimbus rule violations -- in 

addition to the already-existing lightning and radar-attenuation filters. They should also 

compute an additional radar parameter, Volume Integral Reflectivity, and both of these new 

parameters should be added to the "Merged Files."

Move toward a radar parameter that incorporates cloud volume and/or thickness in addition to 

average radar reflectivity.

Somebody should research possible remote-sensing proxies for the theoretical electrical decay 

time, which has been found to be dominated by particles in the size range, 0.2 - 2.0 mm. (In a 

"white paper dated 31 July 2003 triggering field John Willett showed, for spherical particles, 

that electrical decay time is proportional to optical extinction coefficient. The latter is 

unfortunately still a local parameter, but one more susceptible to remote measurement.)
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45WS presented a number of new questions of rule interpretation to the LAP for feedback. Examples 

of the most urgent questions and LAP responses are:

Does moisture on the windscreen of the reconnaissance aircraft constitute "precipitation?" 

No.

Is the mid-level blow-off from a cumulus with its top lower that the -20 °C level considered an 

anvil, a debris cloud, or what? Discussion of this is in process as of the 21 May 2003 LAP 

telecon.

Does the thick-cloud rule apply to cumulus clouds? Discussion of this is in process as of the 

21 May 2003 LAP telecon.

Most participants left the meeting with several action items. Examples of the most critical ones not 

already included under the above LAP recommendations are:

The LAP should develop an interim version of its planned radar-based anvil rule that can be 

applied immediately, based on radar information already available to the LWOs, because it 

will take some time for the range to implement calculation/display software for whatever radar 

parameter is finally selected for the new rule(s). (See entry for 2 October 2003, below, for the 

LAP response.)

The LAP should review and comment on the latest FAA re-write of the "LFCC" for accuracy 

and logical consistency re. the existing LLCC. (This re-write was provided to Phil Krider in 

an e-mail from Denny Mathew (FAA/AST) dated 5 May 2003.)

21 May 2003 LAP Telecon -- Held to discuss rule revisions (starting from the LLCC as documented by Krider 

et al. [1999]) related to the 45WS questions and other issues from the 12-15 May 2003 meeting:

Re-define "transparent?" Harry Koons will suggest revisions...

Change "convective" to "cumulonimbus" in anvil definition?

Harry will draft a new FAA definition of "thick cloud layer."

Remaining 45WS and FAA issues will be deferred until July.

29 May 2003 LAP Telecon -- Continuation of the discussion of LLCC revisions begun on 21 May 2003 

resulted in the following decisions:

Don't change the "anvil" definition because we are worried about any Cu's above -5 °C becoming 

electrified.

Do change all cloud boundaries to 0 dBZ. Also add a "cloud base" definition.

Defer any change in the definitions of "cloud layer" and of "thick cloud."

Make only minor changes to the "transparent" and "nontransparent" definitions. Defer a major reexamination of this issue.

Include a "note" under the definition of "precipitation" that specifically includes graupel.
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Adopt a new definition of "field mill."

As a result of this discussion, Harry Koons put out another draft of the definitions on 29 May 2003. 

Although everyone seemed pretty happy with this version, there is apparently no record of any vote or 

formal approval. (Richard Walterscheid offered a couple of additional suggestions from Germany on 

30 May 2003.)

17 July 2003 Joint LAP/ABFM II Telecon --

Another "filter" is added to the anvil dataset that removes those with radar bases (or falling 

precipitation) ≤ 5 km.

Need to define an electrical length for Titan, hence an electric-field threshold for triggering hazard, to 

use in the extreme-value analysis of anvil scattergrams -- see next telecon.

Need to review the latest FAA rules for next telecon.

28 July 2003 Joint LAP/ABFM II Telecon -- Consideration of provisional conditions for triggering by launch 

vehicles from John Willett.

21 August 2003 -- Having received an indication of interest from the KSC Weather Office, John Willett 

suggested to Nickolay L. Aleksandrov, who had recently presented a lightning-triggering model at an 

international meeting that they both attended, that Prof. Aleksandrov and his Russian colleagues (Edward M. 

Bazelyan and Yuri P. Raizer -- both well-known experts on long-spark breakdown) develop a proposal for a 

small contract from NASA/KSC. The specific question of interest to NASA was whether it is possible to set 

reliable lower bounds on the electrical conditions as a function of altitude for lightning initiation by either a 

launch vehicle during boost phase or a re-entry vehicle (e.g., the Space Shuttle) during glide. The altitude 

range of interest was specified as 0 - 10 km, with special attention to the triggering conditions at anvil 

altitudes. The final Russian proposal was submitted on 19 October 2003, but for various reasons it was not 

funded until 1 February 2005. (The resulting final report is referenced in the entry for 4 November 2005.)

29 September 2003 LAP Telecon defined the essential objections to the latest FAA LFCC.

21 October 2003 LAP Telecon -- Deadline is this week to review Harry's comments on the FAA "LFCC" rewrite. There was discussion of the Russian proposal to determine a lower bound on the danger threshold aloft. 

Harry Koons presented an example extreme-value analysis.

31 October 2003 -- The LAP forwarded to the FAA its official response to the latest FAA version of the rules. 

Major LAP objections included the following:

Restore the "clear and convincing evidence" requirement to the "General" section.

Restore the requirement (in the definitions) for ground-based field mills to measure the surface electric 

field.

Restore the caveat, "Detached anvil clouds are never considered debris clouds," to the Detached Anvil 

rule.

Delete the "Electric Fields Aloft" rule. (This is the first available indication that the LAP had 

withdrawn its earlier strong support for this rule.)

16 December 2003 ABFM II Telecon -- Jim Dye is again a member of the LAP, having rejoined sometime in 

2003 after leaving it sometime in 1994. Harry Koons presented extreme-value-analysis calculations for the 
Page 160 of 234

3X3X3 km cube radar averages. It was concluded that the 11X11 km column average (presented on or after 30 

October 2003) was a better radar parameter than the 3X3X3 cube.

30 March 2004 Joint LAP/ABFM II Telecon --

It is concluded that radar parameters based on volume integrals are better than reflectivity averages for 

discriminating safe from unsafe anvils, and that the best way to approximate volume integrals is to 

multiply column averages by column thicknesses.

A question remains about what lower cut off to use for reflectivity in individual radar cells: -10 dBZ, 

as currently, or 0 dBZ.

More discussion about the FAA rules, especially the question of what equipment is required by the 

"General" section 417.1(b).

6 April 2004 LAP telecon with Titan folks about modeling exhaust-plume lengths.

13 April 2004 Joint LAP/ABFM II Telecon --

Apparently there was some discussion of the latest (12 April 2003) FAA LFCC version -- the LAP is 

still not happy with the required equipment and the requirement for field mills.

Agreement to use 3 kV/m as the E-field threshold.

29 April 2004 LAP Telecon -- To discuss latest revisions, primarily to the General section, of the FAA LFCC 

and to address the 45WS question about the recent change of the cloud-edge definition from 10 dBZ to 0 dBZ.

30 April 2004 LAP Telecon -- The LAP forwarded a formal response to Todd McNamara's question about the 

cloud-boundary definition.

14 May 2004 -- The LAP forwarded to the FAA its revisions to their latest LFCC draft, as discussed in great 

detail during and after several previous LAP telecons. 

25 May LAP Telecon -- Harry Koons led the LAP through his preliminary extreme-value analysis for the 

11X11 km column-integrated reflectivity.

21 July 2004 LAP telecon --

More on the extreme-value analysis from Harry Koons.

Yet another FAA LFCC version...

Initial stab at what a radar-based anvil-rule exception might look like. (Discussion and wordsmithing 

of this exception and the associated definitions continues via e-mail between telecons.)

11 August 2004 ABFM II Telecon --

Harry Koons presented his final version of the extreme-value analysis for the "11X11 km columnintegrated reflectivity" (re-named VAHIRR on 26 August 2004) with the agreed-upon filters. Making 

worst-case assumptions, the probability of encountering fields ≥ 3 kV/m during a launch through an 

anvil having VAHIRR = 10 dBZ-km was estimated at 10-4

. This result was eventually accepted by the 
Page 161 of 234

LAP as justifying the 10 dBZ-km threshold for Anvil Clouds. (See also the entry for 3 August 2007.)

Chose a radar threshold of 0 dBZ for averages to avoid negative numbers going into averages, to 

minimize differences between radars, to reduce sensitivity to scan gaps, and to be consistent with the 

new definition of cloud edge.

The question remained whether to include in any new LLCC the radar fractional-volume filter that we 

planned to use in the data analysis.

Frank Merceret and Jennifer Ward discussed their cloud-edge determination in relation to field decay 

(standoff issue) and radar edge (transparency issue) in the ABFM II dataset.

26 August 2004 -- First introduction via e-mail of the final terminology for the chosen radar parameter (which 

I have been calling "11X11 km column-integrated reflectivity") by Jim Dye: "Volume-Averaged, HeightIntegrated Radar Reflectivity (VAHIRR)."

26 August 2004 -- "White Paper" by John Willett recommended 6.2 kV/m as the best available estimate of 

triggering conditions for a large (Titan-class) space launcher at 10 km -- a typical anvil altitude. This estimate 

involved measured triggering conditions for rockets towing grounded wires [Willett, et al., 1999], estimated 

electrical effective lengths of exhaust plumes (based on video observations of Titan and Shuttle launches, 

summarized by Frank Merceret on 5 January 2004), and estimates of the worst-case decrease in field threshold 

with atmospheric density (Paschen's Law).

23 September 2004 -- The LAP responded to John Madura's question about triggering fields for small launch 

vehicles with a caution that we don't currently know enough to drastically scale up the triggering thresholds 

with decreasing vehicle size.

22 October and 4 November 2004 LAP Telecons -- Inconclusive discussion of the VAHIRR exceptions, 

associated definitions, and an interim implementation with existing radar products. E-mail discussion 

continues.

6 November 2004 -- Harry Koons's first e-mail reference to truth-table analysis in connection with the current 

draft anvil rules. This analysis took us off into a major reorganization of the anvil rules -- mainly via extended 

e-mail discussion between John Willett and Harry Koons.

10 November 2004 LAP Telecon --

Discussed the latest truth-table-validated versions of the anvil rules.

Minor revisions to the VAHIRR definition.

12 November 2004 -- The LAP formally forwarded (via e-mail) its agreed versions of the new anvil rules, 

VAHIRR definitions, and interim implementation instruction to the KSC Weather Office (John Madura), but 

see the entry for 3 February 2005 below.

17 December 2004 -- 45WS (apparently in consultation with the 30 WS) submitted suggested revisions to the 

LAP's 12 November 1994 anvil rules.

1 February 2005 LAP Telecon -- Apparently to discuss the 45WS suggestions.

3 February 2005 -- The LAP formally forwarded (via e-mail, formal memo from chairman to follow) modified 

versions of the new anvil rules, VAHIRR definitions, and interim implementation instruction to the KSC 
Page 162 of 234

Weather Office (John Madura). No substantive changes were made to the 12 November 2004 version; most of 

the 45WS suggestions of 17 December 2004 were rejected. This seems to have been the final version 

(translated from FAA into USAF language), as faithfully reproduced on 3 June 2005 as Space Shuttle LLCC 

(2005) [LCN 01166R01, below.

11 May 2005 -- Harry Koons passed away suddenly and unexpectedly.

3 June 2005, Space Shuttle LLCC (2005) [LCN 01166R01, see Appendix I, Section A1.10] -- MAJOR 

Changes: This is the first application of both Harry Koons's truth-table analysis, and his statistical analysis of 

the new ABFM II dataset, to both clarify and relax the anvil rules. In spite of numerous wording changes 

throughout (which will be ignored here), there have been no substantive changes to any of the other rules 

(except through changes to the definitions, as detailed below).

Anvil Rules (now C) have been completely re-written. In particular, the order of the rule sections has 

been reversed so that the "least threat" (through) now comes last, and the "greatest threat" (within 10 

NM) now comes first. They have also been logically re-organized to so that the times after lightning 

and/or detachment that are referenced in their different sections no longer overlap, and so that each 

standoff-distance range is explicitly specified (e.g., 3(b)(3), "Do not launch... within 5 NM of 

nontransparent parts of a detached anvil cloud for the first 3 hours after...", has been replaced with 

C(2)(b), "Do not launch... between 0 (zero) and 5 NM from a nontransparent part of a detached anvil 

cloud between 30 minutes and 3 hours after..."). The substantive changes to these rules are less 

complex than the wording changes and can be appreciated most easily by studying the truth tables 

attached below. These substantive changes are summarized verbally here:

Attached Anvils (C(1)):

Satisfaction of all three VAHIRR conditions now allows flight >30 min after the last 

lightning at all ranges (including penetration); whereas penetration was previously 

prohibited at all times (including >3 hr), and flight between 0 and 5 NM was 

prohibited between 30 min and 3 hr after lightning.

No changes have been made to the launch permissions if any of the VAHIRR 

conditions is not satisfied.

Detached Anvils (C(2)):

Satisfaction of all three VAHIRR conditions now allows flight >30 min after the last 

lightning at all ranges (including penetration); whereas penetration previously was 

prohibited between 30 min and 4 hr under all conditions and after 4 hr unless the 

cloud had been detached for more than 3 hr, and flight between 0 and 5 NM was 

prohibited previously between 30 min and 3 hr after lightning unless a low-field lowradar condition was satisfied.

No changes have been made to the launch permissions if any of the VAHIRR 

conditions is not satisfied.

Definitions:

Two new definitions ("Volume-Averaged, Height-Integrated Radar Reflectivity" and 

"Specified Volume") have been added to define VAHIRR and how to compute it. 
Page 163 of 234

Additionally, an "Interim Instruction" has been added specifying how to conservatively 

approximate VAHIRR from currently available radar tools.

A new definition of "Field Mill" has been added to further emphasize that that is the only 

acceptable instrument for implementation of the Surface Field Rule (now H).

IMPORTANT: A new definition of "Cloud Base" has been added, and the definitions of 

"Cloud Edge," "Cloud Top," and "Nontransparent" have been substantively modified from the 

previous 10 dBZ radar threshold to 0 dBZ. This change affects all references to clouds 

throughout the rules, making them more conservative.

The definition of "Transparent" has been changed to remove references to the disk of the sun 

and distinct shadows on the ground, also making the rules somewhat more conservative.

Space Shuttle LLCC (2005) [LCN 01166R01] is substantially identical to the best available 

approximation of the rules that were approved previously by the LAP. This approximation resulted 

from starting with the LAP revisions of the LFCC that were forwarded to the FAA on 14 May 2004 

(apparently the most recent, including the definition changes that were proposed on 29 May 2003) and 

then replacing the anvil rules therein with the VAHIRR versions of those rules (together with their 

associated definitions and interim instruction) that were forwarded to the KSC Weather Office on 3 

February 2005 (also the most recent LAP-approved versions). Aside from numerous, apparently 

unimportant, changes in wording from FAA to KSC language (primarily in definitions and rules other 

than those applying to anvils) and some re-ordering of the definitions, potentially substantive 

differences between this composite and Space Shuttle LLCC (2005) [LCN 01166R01] are the 

following. (It is not clear whether the LAP actually approved these details.)

The triboelectrification rule and associated definitions present in the FAA version have been 

dropped in the NASA version.

The following "Notes" have been added to the NASA version of the "Surface Electric Fields" 

rule:

"i) Electric field measurements at the surface are used to increase safety by detecting 

electric fields due to unforeseen or unrecognized hazards."

"ii) For confirmed failure of one or more field mill sensors, the countdown and launch 

may continue."

The definition of "associated" is embellished with the following:

"An example of clouds that are not associated is air mass clouds formed by surface 

heating in the absence of organized lifting."
Figure A2-1 Expanded Space Shuttle LLCC (1998) Attached Anvil Rule
Page 165 of 234

Figure A2-2 Space Shuttle LLCC (2005) Attached Anvil Rule
Page 166 of 234

Figure A2-3 Expanded Space Shuttle LLCC (1998) Detached Anvil Rule

Not .. , 

A cd, entry ,f " "O w ... n. tho r~le d·, .. not explicitly _ntlon thl. >r>dltlon. 

" Low field" _an. (.) 21 'otot~I"" .. II, <~ n .. 1 frOlO cloud . (b) <1000 VI. lor 15 .In .t all. 11111. 

s:s n .. l ft"" fll;ht pot! IIND.t IIlll(.) In (01 . OM (C) cloud I. <It d6L 15 "",I fro. II1~M path 10 .. 1$ _In. 

Thl. rul. do •• not Inv," VAHIRR • • 0 th~ tWO panel, are Identical . 

• Tho •• coli ........ t>I;uoua boH,_n t><o rule .. ctlon • • ,n. uylnQ Nc La_ ar>d tho ot~o< 

a'ylnq La~nCh No, 'ro~lbltod . •• It th.r. ha. nev.r boon. II;htnl"" dl.c~.r;~ . t~~n thl' tl .. perIod appll ••• 
Page 167 of 234

Figure A2-4 Space Shuttle LLCC (2005) Detached Anvil Rule

If ALL ) VAHIR~ eondl~ o~ ~ •• t l.f lod : 

NOlU : 

~ ~.II enlry >{ " -- " .. on. lh. rul. d o •• ~~ explici t ly .. nt lon t hl. ~ndltlon . 

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.51\101 f rooo f11"'l poth AIlO Ol .. HI I.> in (0) , 0"" (<:1 do..cl I. <I' dB~ U ""I f,OOI !119M polh {oe 

H .. In • 

• TM. Cf 1.01Oblq, be t-., .. c t lon. (.1 , wIllch .. y. No Ll.unel , ond (el(21 , will "Y' 

LI.~n~ Not Pro~lbl od • 

•• If ch.C. ~o' neT>< been 0 llqht nl"9 di.ch.rq~, then ,hi. 11-. poclod oppll ••• 
Page 168 of 234

4 November 2005 -- A final report was received from the Russian group on a KSC contract to study triggering 

conditions aloft. (First mention of such a contract was reported in the entry for 21 August 2003.) This report 

was sent out for peer review starting about 21 December 2005. A detailed evaluation of the final report, and 

five reviews thereof, was provided to NASA/KSC by John Willett on 29 June 2006. Several recommendations 

for follow-on work were made, both by the report's authors and by John Willett, but nothing further has been 

done to date. Much of the contents of this report has now been published by Bazelyan et al. (2007).

16-17 November 2005 LAP Meeting at NASA/JSC in Houston -- Several topics were covered in some detail 

at this meeting:

Tim Oram (JSC/SMG) outlined the current SMG flight rules for Shuttle. Tim proposed a way to add a 

VAHIRR exception to the flight rules. This led to some LAP recommendations:

It is appropriate to use multiple NEXRAD radars to evaluate VAHIRR.

Conduct an experiment with near and distant NEXRAD radars looking at the same anvil to 

determine whether there is an upper range limit for accurate calculation of VAHIRR.

It is appropriate to forecast VAHIRR for evaluation of the flight rules.

It was tentatively agreed to change the level above which "core" radar reflectivities are 

reckoned in the VAHIRR-validity note from 4 km to a temperature level such as +5 C.

The problem of a really long, nontransparent anvil attached to a distant active core was raised again. 

John Willett offered a proposal to solve this problem by modifying the first section (through or within 

10 nm) of the Attached Anvil rule. This and other VAHIRR-related issues led to a long e-mail 

deliberation after the meeting.

45WS raised a number of new questions about the most recently implemented (3 June 2005, Space 

Shuttle LLCC (2005) [LCN 01166R01]) version of the anvil rules. Frank Merceret raised the question 

of how to calculate VAHIRR for nontransparent anvils that cannot be seen on radar. Again, these 

issues led to protracted e-mail deliberation.

Richard Blakeslee (NASA/MSFC) summarized measurements over thunderstorms by the ER-2 and, 

more recently, by ACES. Large fields can occur in the 15 - 21 km altitude range (>17 kV/m at 15 km 

and >8 kV/m at 20 km). Concern was raised by several LAP members about the 2 nm standoff above

thunderstorms in the flight rules.

Based on the ABFM II data, Jim Dye was optimistic about reducing standoff distances from anvils and 

debris clouds in the near future and, with considerably more effort, possibly applying VAHIRR to 

debris clouds.

Hugh Christian agreed to re-examine the question of whether it would be productive to include the 

ABFM I dataset in any such re-analysis. The main questions were whether the E-field data could still 

be read from the Exobyte (TM) tapes and whether the radar calibration could be salvaged.

Davis Sentman (University of Alaska, Fairbanks) reviewed what is known about sprites with respect 

to the hazard to Shuttle during landing. Mark Stanley (NMIMT) reviewed recent measurements of the 

charge and current moments in sprites. Although the total energies and peak currents are inferred to be 

large -- up to 10 MJ and 100 kA in extreme cases -- the energy and current densities are not well 

known. Elves and sprite halos are not a problem. Not enough is known about blue jets. The reentry 
Page 169 of 234

plasma sheath probably protects Shuttle from sprites at high velocities/altitudes, but it was not 

immediately known to how low an altitude this might give protection. Would the ~100 V/m field 

transients after large positive lightning discharges be enough to initiate sprites from Shuttle itself?

John Willett gave a preliminary summary of results of a recent NASA/KSC contract to a group of 

Russian scientists. (First mention of such a contract was reported in the entry for 21 August 2003. The 

resulting final report is referenced in the entry for 4 November 2005, immediately above.) The bottom 

line: They found a reasonable, but not a conclusive, basis for asserting that a lower bound on the 

lightning-triggering conditions by a flying vehicle (taken to be the conditions for continuous 

propagation of a positive leader, once initiated) does not depend significantly on altitude between the 

surface and 10 km. (Subsequently, the LAP has continued to use Paschen's Law -- triggering threshold 

proportional to atmospheric density -- however, to retain an ample margin of safety.)

The need was recognized for a statistician to replace Harry Koons on the LAP. Richard Walterscheid 

agreed to ask Aerospace Corp. if it might provide a suitable candidate. (Once again it is not clear 

whether Tim Oram at SMG got formal feedback on the flight rules from the LAP after the meeting.)

After the Houston meeting Frank Merceret pointed out that the anvil rules with a VAHIRR exception 

to a 5 nm standoff guaranteed that VAHIRR would be invalid outside 3 nm so that much of the 

exception could not be used. John Willett made a diagram illustrating this problem on 2 August 2007. 

It was first addressed with new rule language during the 19-20 March 2008 LAP meeting.

30 January 2006 LAP/ABFM II Meeting at the AMS Meeting in Atlanta -- Doug Mach will review his cases 

from ABFM I to determine exactly what kind of clouds they were flying in.

19 August 2006 -- Phil Krider, as chair of the LAP, sent a memo to John Madura, KSC Weather Office, 

indicating the importance of the LPLWS (ground-based field-mill system) and how both safety and launch 

availability would be decreased if it were terminated.

6 November 2006 ABFM II Telecon –

Participants concluded that continued analysis of the ABFM II dataset would focus primarily on two 

topics: (1) possible reductions of standoff distances from anvil and debris clouds and (2) extension of 

VAHIRR to debris clouds. The work would be funded by the Launch Services Program (supporter of 

expendable vehicles).

ABFM II anvil data is apparently not adequate to resolve E-field decay with time.

The LAP apparently considered Frank Merceret's draft on standoff distances from anvils and debris 

clouds, and he was tasked to draft a straw-man standoff rule for anvils and debris cloud.

Jim Dye was tasked to identify key differences between anvils and debris clouds, as classified in the 

AMFM II dataset

There was discussion of a possible follow-on aircraft experiment to investigate thick clouds and 

disturbed weather (in winter) and to further study standoff distances and field-decay times in 

anvils/debris clouds (in summer). The Viking S-3 that is owned by NASA Glenn Research Center was 

a possible candidate. The FAA is currently paying to rebuild the A/C. MSFC would be a good place to 

conduct such an experiment.
Page 170 of 234

The question of the flight rules, and results from the Houston meeting last year, was raised again. Tim 

Oram said he has some examples of CG flashes from 20 - 25 dBZ clouds.

14 February 2007 LAP/ABFM II Telecon -- Topic: The Next Steps in ABFM II Analysis

A "phasing plan" must be developed to satisfy requirements of the new Launch Services Program 

sponsor.

Frank Merceret was concerned that the fall-off of fields with distance from "anvils" appeared much 

slower in the ABFM I dataset than in ABFM II. Doug Mach resolved this paradox by noting that the 

ABFM I data that Frank was using applied mostly to developing storms and was not really applicable 

to anvils. Further, the ABFM I data on debris clouds was concerned primarily with field decay times 

inside the clouds and would not help with standoffs.

Based on the above Frank Merceret was tasked to prepare a proposal to revise the anvil and debris 

cloud rules to reduce the standoff distances, and to do a statistical evaluation of their safety. (Frank 

responded on 26 February 2007 with draft rules but pointed out that he was not sure how to evaluate 

their safety and needed guidance from a statistician.)

Monte Bateman was tasked to extend VAHIRR to debris clouds.

Jim Dye was tasked to compare ABFM II and operational definitions of debris clouds.

It was decided not to pursue ABFM I data on thick clouds.

7 March 2007 LAP/ABFM II Telecon –

Jim Dye reviewed the radar definitions of anvils and debris clouds that were used to sort the ABFM II 

database. The latter definition is much less clear than the former. Examples of debris clouds were 

shown from the ABFM II Web site.

A definition of the radar cone of silence is needed for VAHIRR validity.

5 April 2007 LAP/ABFM II Telecon –

Frank Merceret pointed out that a capping altitude is needed for the "cone of silence" above the radar 

in the VAHIRR definitions. This led to general agreement but considerable debate over what altitude 

to choose. It was decided that the cone should be capped by the cloud-top height, the local tropopause 

height, or 20 km, whichever was verifiably lowest.

Frank Merceret led discussion of his proposed new standoff rules for attached and detached anvils and 

for debris clouds (reduced from 5 to 3 nm between 30 min and 3 hr) and his preliminary analysis of 

their risk based on Gaussian statistics.

Frank Merceret's risk analysis also included the following "a fortiori" argument: VAHIRR is 

effectively zero at any location ≥ 3 nm from the cloud edge. Therefore, flight in the region of clear air 

between 3 and 5 nm from cloud edge must be at least as safe as penetration of cloud for which 

VAHIRR ≤ 10 dBZ-km, which is permitted (at least for anvils). Richard Walterschied did not accept 

the a fortiori argument and required a statistical justification for the reduced standoff distances.
Page 171 of 234

There was general agreement that Frank's Gaussian statistics, while encouraging, were not sufficiently 

rigorous to justify a rule change. John Willett suggested including clouds containing <3 kV/m fields in 

the statistics to increase the degrees of freedom by about a factor of three.

Bill Roeder volunteered to compile a list of unusual events (e.g., long-delayed lightning out of debris 

clouds) that the 45WS could track and document for the LAP. Everyone thought this was a great idea.

26 April 2007 LAP/ABFM II Telecon –

A space physicist with statistical expertise, Paul O'Brien, was apparently identified at Aerospace who 

could replace Harry Koons on the LAP and help us with the debris-cloud and standoff-distance 

analysis.

Frank Merceret agreed to repeat his standoff analysis including clouds with low fields, which were 

previously excluded, because this would increase the degrees of freedom in the analysis. Any 

Aerospace statistical analysis was deferred until this exercise was completed.

The language of the cone-of-silence definition was finalized.

Future use of the ABFM I dataset has two potentially serious problems:

The radar data is nearly inaccessible on old data tapes in "Magill format." Frank Merceret is 

trying to convert these tapes. In any case, its calibration will remain uncertain by "several 

dBZ."

As noted in November 2005, the electric-field data is archived on Exobyte (TM) tapes that 

might or might not be readable. Monte Bateman was tasked to try reading the Exobyte tapes. 

[Note: The E-field data from ABFM I has recently been salvaged and re-analyzed by Mach 

(2009) for use by Walterscheid et al. (2010).]

During May and June, 2007, Paul O'Brien complete a statistical analysis of Frank Merceret's standoff-distance 

dataset, and the LAP asked MSFC to investigate the source of persistent ~1kV/m fields outside the clouds in 

that dataset -- see O'Brien and Walterschied (2007), below.

15 June 2007 -- Publication of O'Brien and Walterscheid (2007), which gives an analysis of standoff distances 

from anvils and debris clouds based on 2-parameter Weibull statistics. Findings were (1) the electric field 

intensity does not depend on distance from the cloud edge and (2) the probability of exceeding 3 kV/m outside 

the cloud is less than 10-8

.

21 June 2007 LAP/ABFM II Telecon –

The new cone-of-silence definition was formally accepted.

The status of the statistical analysis of standoffs and the a fortiori argument were revisited, but no 

conclusions were recorded.

Jim Dye led us through a discussion of the VAHIRR scatterplots for debris clouds.

Shouldn't all of the filters (lightning, core, attenuation, wet radome, and fraction of "specified volume" 

filled -- this last not currently included) be specifically mentioned in the rules?
Page 172 of 234

Some discussion of differences in interpretation of "debris clouds" between the ABFM II analysis and 

the Range.

Now that Aerospace has identified an extreme-value-analysis expert, it would be interesting to 

compare VAHIRR results between anvils (repeat Harry Koons's analysis) and debris clouds.

3 August 2007 LAP/ABFM II Telecon –

Paul O'Brien discussed his preliminary statistics for VAHIRR in debris clouds. He pointed out a lot of 

temporal correlation in the dataset that needs to be mitigated before further analysis. (Frank Merceret 

had previously found a 10X decrease in degrees of freedom due to serial correlation.) [Harry Koons 

had dealt with this problem by requiring 10 samples to constitute a "launch" -- see entry for 11 August 

2004.]

Revised definitions to account for the altitude cap on the cone of silence and the fraction-filled 

VAHIRR filter were accepted.

Paul's final statistics for anvil standoff distances were reviewed. Final statistics will be distributed and 

voted on next telecon.

14 September 2007 LAP/ABFM II Telecon –

Further discussion of the standoff statistics led to a request for Paul O'Brien to consider anvils and 

debris clouds separately to see if there's and evidence of a difference.

The LAP accepts the 10X decimation for degrees of freedom in the VAHIRR statistics.

Doug Mach assured us that the low, near-uniform fields measured outside these clouds, which were 

found by O'Brien and Walterschied (2007), are real.

Paul O'Brien's extreme-value analysis of VAHIRR in debris clouds looks good in spite of low 

effective number of samples. For VAHIRR < 15 dBZ-km, the probability of fields >3 kV/m is well 

under 10-4

.

1 October 2007 LAP/ABFM II Telecon –

Paul O'Brien reviewed his separate standoff treatment for anvil and debris clouds. It still looks OK. 

Based on this result, the LAP approved the reduced standoff distance of 3 nm for both.

Jim Dye suggested lumping anvils (dropping the frozen requirement) and debris clouds together in a 

single VAHIRR rule, to be considered next time. (On 6 October 2007 John Willett distributed an 

analysis of the differences among these three rules that made it seem unlikely that they could be 

combined.)

Paul O'Brien will repeat the extreme-value analysis for anvils and compare with debris clouds and 

with Harry Koons's earlier analysis.

17 October 2007 -- Paul O'Brien was formally appointed a new member of the LAP.

26 October 2007 LAP/ABFM II Telecon –
Page 173 of 234

Frank Merceret volunteered to act as "secretary" for the LAP telecons and meetings from here on out. 

This was seen as a big benefit, since note-taking had not been very reliable.

Todd McNamara volunteered to distribute three master's theses on the spatial distribution of lightning 

strikes. (This was done on 29 October 2007.)

The definition of "debris cloud" was revisited from the 7 March 2007 telecon. It was not clear that the 

AF and the ABFM II team were using the same definition. Todd McNamara will try to re-define the 

term.

When in doubt about which of two LLCC applies, apply both and use the most conservative result. 

Language is needed in the rules to codify this.

It's OK to use VAHIRR in clear air pending a change in the standoff distances in the anvil rules.

The 45WS had submitted another list of LLCC questions on 23 July 2007. Some of these were easily 

answered by the LAP. Others were held over for the next telecon. A few created action items:

John Willett will draft an exception to the anvil rule for Cu with tops between ± 5 °C.

John Willett will clarify the language about starting the lightning clock in the anvil rule.

John Willett will clarify the distinction between the attached anvil and its parent Cu.

John Willett will consider further changing the definition of the cloud boundary to the 

nontransparent edge and summarize the implications for what is attached and what is 

detached.

19 November 2007 LAP/ABFM II Telecon --

The LAP resumed consideration of the 45WS questions:

John Willett will look at the logic of the cumulus rules to see if they can be changed to 

language similar to that of the revised anvil rules.

There was considerable discussion of where to place the VAHIRR-validity caveats. Frank 

Merceret pointed out that one pixel of 3 dBZ is certainly safe but results in VAHIRR 

invalidity. It was apparently decided not to worry about this prospect. Frank and Todd 

McNamara will make a list of where which caveat should be put.

John Willett will try to draft an exception to the thick-cloud rule so that anvils don't get treated 

as thick clouds.

Revised anvil rules (with 3 nm standoffs) and associated VAHIRR-related definitions (version of 27 

October 2007) were accepted by the LAP.

Revised debris-cloud rule (with 3 nm standoff -- version of 7 October 2007) was accepted by the LAP.

John Willett was to send out a new version of the rules that consolidates all of these changes, plus the 

other ones proposed in the previous telecon (lightning clock, "anvils" produced by shallow Cu, 

distinction between an anvil and its parent CB, and new cloud-edge definition) for a final vote by 30 

November 2007. Although this consolidated version is apparently not available, all (except Hugh 

Christian, who apparently didn't vote) accepted these changes.
Page 174 of 234

28 November 2007 -- John Madura distributed the rule-change history that has been used in preparing this 

chronology.

26 December 2007 -- Pre-release copy of Paul O'Brien's statistical analysis of VAHIRR for debris clouds 

[TOR-2008(1494)-1 (DRAFT)] was distributed to the LAP. It shows that debris clouds have systematically 

lower risk of >3 kV/m electric fields than do anvil clouds. 

8 January 2008 -- Todd McNamara and Frank Merceret submitted revisions to the VAHIRR definitions, anvil 

rules, and debris-cloud rules for consideration in a telecon proposed for the end of the month. This telecon 

apparently never occurred.

11 or 13 March 2008 LAP telecon with FAA on Kodiak --

Only three members of the LAP attended (Krider, Walterscheid, and Willett).

There have been no commercial launches from Kodiak.

Description of the launch rules used at Kodiak -- came from Sandia.

They appear to be conflating safety rules for ground operations with those for launch.

Description of high surface e-field readings that occur at Kodiak (6-8 kV/m) and what little is known 

of the related meteorology ("cumulus precipitation events"). Natural lightning is very rare at Kodiak.

They have a weather radar (very limited capability) operating for all launches and a reconnaissance 

aircraft also available.

Based on this telecon and further discussion at the 19-20 March 2008 LAP Meeting (immediately 

below), several recommendations were sent via e-mail from the LAP to the FAA on 26 March 2008:

1) The occurrence of clouds producing graupel is a strong indicator of risk. This is supported 

by the occurrence of the high fields (6-8 kV/m) observed during situations where graupel 

showers occur.

2) Such high fields are themselves indicators of a danger, whether they are observed to occur 

in association with graupel or not. Smaller elevated fields exceeding somewhat 1.5 kV/m may 

occur in benign situations (e.g., blowing snow), but further study is required to characterize 

the conditions that are safe. 

3) The near absence of natural lightning should not be taken as an indicator of no risk.

4) A small-rocket campaign should be conducted to assess the triggering potential in clouds.

5) A survey of conditions that occur when high fields are recorded (clear skies, clouds, 

precipitation, etc.) should be undertaken.

6) A strategy for determining the existence of embedded convective clouds should be 

developed.
Page 175 of 234

7) The weather conditions likely to present a hazard for triggering lightning during launches 

(the focus of the LAP up to now) are NOT the same as the conditions that present an 

electrostatic hazard to personnel during ground operations (the Sandia safety criteria).

8) For triggering lightning we recommended that the KLC take advantage of existing expertise 

at the University of Florida and/or New Mexico Tech rather than re-inventing that technology.

19-20 March 2008 LAP Meeting at KSC --

Reviewed an 11 March 2008 version of the LLCC that had been circulated by John Willett, which 

purported to include all changes previously agreed on in telecons, and agreed to most of them. 

Exceptions:

All agreed to move the short-parent exclusion for anvils from the rules to the definition of 

"anvil."

Language in the "General" section that requires all criteria to be evaluated was further 

clarified.

Agreed to exempt attached anvils from the cumulus rule. John Willett will add English units in 

parentheses wherever metric units were used.

Moved most of the VAHIRR-validity caveats into a separate definition of "VAHIRR Acceptance 

Criteria."

The two debris-cloud standoff-distance "outliers" were found to be in cloud, so not outliers after all.

Moved the surface-field rule to first place, before even the lightning rule.

Clarified the "through or within" language in several rules.

Finally addressed the invalid-VAHIRR problem that was caused by the previous VAHIRR exception 

to the 5 nm standoff from detached anvils (and also by the newly proposed VAHIRR exception to the 

10 nm standoff for all anvils). Thanks to Frank Merceret, it was decided to draft language requiring 

VAHIRR to be evaluated within 1 nm of the flight path for the new 3 nm standoff (8 nmi for the 10 

nm standoff) to ameliorate this problem.

It was agreed that section (a) of the attached-anvil rule was too conservative. Along the lines indicated 

above, it was decided to grant a VAHIRR exception to the 10 nm standoff from attached anvils during 

the first 30 min after lightning.

John Willett will draft language for a VAHIRR exception to the debris-cloud rule.

John Willett will draft for review a new version of the cumulus rule that is consistent with the new 

format of the anvil rules (as promised during the 19 November 2007 Telecon).

Todd McNamara pointed out that the current (LAP approved, 1 June 2005) rule permits flight up to 

the edge of any attached anvil (while respecting the Cu standoffs) before the first lightning (as for t > 3 

hr). What if the first lightning extends out into the anvil, possibly beyond the Cu standoff distance? 

John Willett was tasked to write up the threat scenario that made this situation dangerous and a 
Page 176 of 234

proposed search for first lightning in anvils. (Ultimately the LAP-approved, 6 October 2008 rules 

prohibited flight between 0 and 3 NM of an attached anvil at any time, in the absence of VAHIRR.)

The need for LAP funding to write scientific rationales for the rules was discussed. John Madura was 

urged to explore funding sources.

Frank Merceret prepared the following list of action items from the meeting:

Krider will contact Tim Oram at SMG regarding the status of the Shuttle flight rules.

Christian will examine time variations in fields above anvils when lightning occurs from the 

anvil.

Christian will send the ACES reports to the LAP.

Dye will discuss the debris-cloud cases with O'brien.

McNamara will advise the LAP what rules 45WS currently applies to an anvil-like cloud that 

is below the altitude that defines an anvil cloud in the rules.

Willett will reword the standoff rules to eliminate Frank Mercert's "donut" between 3 and 5 

miles when the reduced 3 mile stand-off distance applies.

Roeder will contact Stano and Fuelberg regarding the probability that the first flash goes into 

the anvil.

25 March 2008 LAP/ABFM II Telecon --

Paul O'Brien reported that a re-do of his debris-cloud standoff statistics without the two outliers 

strengthens the conclusion that 3 nm is more than enough.

Paul O'Brien reported that his VAHIRR statistical analysis for debris clouds is comparable to his new 

re-analysis of Harry Koons's dataset for anvil clouds. The 10 dBZ-km threshold is very safe for debris 

clouds but less so for anvil clouds using the 10X decimation. Paul finds a few tenths of one percent (a 

few cases per thousand) chance of fields exceeding 3 kV/m in his wider (5 - 15 dBZ-km) bin. This 

result leads to much discussion and plans for another telecon on 1 April 2008 to follow up on this 

issue.

1 April 2008 LAP/ABFM II Telecon --

Paul O'Brien reports that expanding the VAHIRR bin to 0 - 20 dBZ-km (which should be more 

conservative) increases the number of points without increasing the peak fields, thus improving the 

statistics. For the combined anvil dataset (all decimated anvil samples having valid VAHIRR from 

either radar), the probability of exceeding 3 kV/m is reduced to 0.016% with an upper confidence limit 

of 0.22%.

John Willett was asked to summarize the uncertainties in the triggering conditions aloft. The resulting 

"white paper" is dated 14 April 2008 and concluded, "The degree of conservatism of the 3 kV/m 

triggering field at 10 km is quite uncertain by may be as large as a factor of six."

11 April 2008 -- 45WS submitted suggested revisions to the LAP's current draft rules.
Page 177 of 234

15 April 2008 LAP/ABFM II Telecon --

Paul O'Brien presented two more analyses of VAHIRR statistics. Revising the algorithm for selecting 

the "combined" dataset (how to choose which radar to use in the presence of filter criteria when both 

VAHIRR estimates are valid) gains data a few points, reducing the risk for both anvils and debris 

clouds. Removing the decimation and correcting the error bounds later, however, makes matters worse 

(compared to the "midpoint" decimation technique) and exposes some "outliers" for debris clouds. 

Overall conclusion: It would be wise to fly another ABFM campaign to increase the degrees of 

freedom.

Paul looked up the outliers mentioned above for further study. These were examined by John Willett 

on 17 April 2008 and determined to be debris of a dying small thunderstorm but with a top still above 

the -10 C isotherm at the time and location of the high-field readings. Jim Dye concurred with this 

identification on 15 May 2008.

John Madura reported that Range Safety was willing to accept a combined risk (all causes) of 1/1000 

for its flight-termination system.

The LAP re-affirmed its approval for the use of VAHIRR exceptions for anvils and approved them for 

debris clouds as well.

Paul O'Brien was tasked to work with John Willett to produce an overall estimate of the conservatism 

build into our VAHIRR risk analysis, which, though solid for debris clouds, appears only marginally 

safe for anvils. This exercise resulted in a PowerPoint presentation dated 22 April 2008. Its 

abbreviated conclusions were the following, justifying the LAP recommendation to use VAHIRR:

1) The 3 kV/m triggering threshold includes at least an arbitrary safety factor of two.

2) Increasing that threshold to only 4 kV/m decreases the triggering probability in anvils from 

a few per thousand to less than 1/10,000.

3) Further increasing the threshold to 5 kV/m decreases the upper 95% confidence limit on 

that probability below 1/10,000! (The risk in debris clouds remains considerably less.)

9 May 2008 LAP Telecon -- A new round of wordsmithing begins:

To eliminate the confusing and sometimes logically duplicative expression, "through and within," Jim 

Dye floated the idea of a new definition of "cloud" (everything inside the cloud boundary) and of 

referencing all standoff distances to the cloud itself.

The "non-transparent" definition should be re-written so that it is the true opposite of "transparent."

Frank Merceret suggested a clever way to re-write the VAHIRR definition to prevent invalid 

evaluations due to small fractional volumes with ≥ 0 dBZ radar returns.

Many of the 45WS comments of 11 April 2008 were considered and most of these were accepted for 

incorporation into the current draft LLCC. The remainder was held over to the next telecon.
Page 178 of 234

15 May 2008 LAP Telecon --

The remaining 45WS comments were considered.

A new definition of "radar" was proposed to require wavelengths longer than 3 cm.

It was recognized that, for VAHIRR evaluation points outside the flight path, the core and lightning 

filters should not be applied.

12 June 2008 LAP Telecon --

Jim Dye and John Willett have been working together on the language and the logic of the rules, 

leading toward a major revision in both the definition of standoff distances and the structure of certain 

rules. John Willett reviewed his reconstruction of Harry Koons's original truth-table analysis of the 

anvil rules (see entries for 6 November 2004 and subsequent) and its extension to the debris-cloud and 

cumulus rules in the latest draft LLCC. Other than the necessity of avoiding contradictions between 

rule sections, the question of whether redundancies simplify the language or confuse the application 

was discussed.

Paul O'Brien suggested archival for future reference/use of the software that he developed for the 

VAHIRR statistical analysis. (At time of writing, both this software and the dataset that Paul used for 

his analysis have been acquired by Jim Dye and John Willett, with intent to post them on the 

NASA/KSC ABFM Web Site.)

Jim Dye and Frank Merceret reviewed problems that they had discovered with the automated 

VAHIRR-calculation software that was being developed for use at the Range.

8 July 2008 LAP Telecon --

On 22 June 2008 Jim Dye and John Willett had circulated a new draft of the LLCC that implemented 

the 45WS suggestions and other changes to which the LAP had agreed during prior telecons. More 

importantly, this version contained significant new changes to the definition of "cloud," to the 

description of standoff distances, and consequently to the language of the rules themselves. The logic 

of certain rules was also modified to remove one contradiction and several redundancies, as indicated 

by truth-table analysis. This new draft was discussed with the following results:

Define "radar reflectivity" to incorporate all requirements for radar and echo characteristics.

Put all words being explicitly defined in quotes in both the definitions and the body of the 

rules.

Phil Krider will work on the syntax of the definitions.

John Willett will turn a final draft on which everyone will vote at the next telecon on 22 July 

2008.

The LAP also discussed its concern about the FAA-required statement in the "General" section, "If a 

launch operator proposes any alternative lightning flight commit criteria, the launch operator must 

clearly and convincingly demonstrate that the alternative provides an equivalent level of safety." John 

Madura was asked to report on what the LAP can do about this.
Page 179 of 234

22 July 2008 LAP Telecon --

There was still no agreement on several aspects of the latest draft:

Hugh Christian didn't understand the rules.

Richard Walterscheid wanted to eliminate the term, "transparent." A contradiction was 

pointed out between the definitions of "transparent" and "nontransparent." John Willett was 

tasked to eliminate "transparent," incorporate "nontransparent" into the definition of "cloud," 

and eliminate all uses of "nontransparent" throughout the body of the rules.

Richard Walterscheid dropped his insistence on radar measurements for standoffs beyond 3 

nm. This might require a major re-write of the anvil rules if the LAP adopts this position. Phil 

Krider and Richard Walterscheid will try to come to agreement on this issue.

Bill Roeder will draft a new definition and rule for disturbed weather.

New comments and clarifications that had been submitted by the 45WS on 18 July 2008 were 

discussed.

4 September 2008 LAP Telecon --

The question of dropping radar requirements on standoff (see entry for 22 July 2008) turns on what 

filters were used in the standoff-distance statistics. Frank Merceret reported that no core- or lightningrange filters, nor the frozen filter, were applied. LAP consensus was to drop the VAHIRR 

requirement, but not the frozen requirement, for >3 nm standoffs from anvils. John Willett was tasked 

to send out a corresponding re-draft.

John Madura requested that the LAP consider volcanic ash and the possibility of writing a rule to 

cover it.

18 September 2008 LAP Telecon -- On 10 September 2008 John Willett had circulated another draft that 

incorporated the changes recommended in the previous telecon -- especially the removal of a radar (but 

retention of a frozen) requirement for anvil standoffs >3 nm. This was the primary topic for discussion:

After introducing "large" before "precipitation" into the definition of "radar reflectivity, it was decided 

to remove it.

Hugh Christian suggests that all distances from field mills be measured in horizontal projection.

Richard Walterscheid suggested splitting off the definition of "cloud" from that of "distance." This led 

to ongoing discussion (about how to specify standoffs and whether to use non-overlapping distance 

ranges) with John Willett after the telecon.

The definition of "Ohms per Square" should be deleted.

Phil Krider will do a literature search on volcanic-plume electrification.

Bill Roeder decided to drop his request to modify the disturbed-weather rule this time around.
Page 180 of 234

2 October 2008 LAP Telecon --

The LAP approved the rule version dated 19 September 2008 with very minor changes. This led 

immediately to the final version described below, which was forwarded to the KSC Weather Office on 

17 October 2008.

6 October 2008, LAP 10/06/08 Recommendation in FAA Format [see Appendix I, Section A1.13] -- MAJOR 

Changes: This is the second application of Harry-Koons-inspired logical analysis and of the ABFM II dataset, 

as further analyzed statistically by Paul O'Brien and Frank Merceret.

The order of the rule sections has been changed in the following ways: The Definitions (G417.3) now 

come immediately after the preamble to emphasize that they are an integral part of the rules. Surface 

Electric Fields (G417.5) is now the first rule, to emphasize that elevated electric fields themselves are 

the hazard. Also, the Anvil rules have been separated into two rules, Attached Anvil Clouds (G417.11) 

and Detached Anvil Clouds (G417.13). In general, an effort has been made to specify whether or not 

the end points of a measurement range are included in a criterion (e.g., "less than or equal to N, but 

greater than M, nautical miles from"). The distinction between a thunderstorm or cumulonimbus cloud 

and its attached anvil has been made even more explicit. Again we ignore minor wording changes and 

concentrate on substantive changes in the following.

General (G417.1): The requirement has been added that the constraints of all LFCC must be satisfied 

and that all potentially applicable LFCC must be applied. [Note that although the familiar “Good 

Sense Rule” is omitted from these proposed LFCC as presented here, essentially the same wording 

does appear in another section of the current FAA LFCC implementation where it is still a mandatory 

requirement. See Appendix I, A1.12 and A1.13. The LAP expects that this requirement will remain in 

the regulations as the LFCC are updated by the FAA.]

Definitions (G417.3): A substantial preamble has been added, explaining the new philosophy for 

measuring distances. (This philosophy has been further elaborated under the definition of "cloud.") In 

particular, two different kinds of distance measurements are defined. Distance between a field mill or 

measurement point and any object means the horizontal distance between that field point and the 

nearest part of the vertical projection of that object on Earth's surface. On the other hand, distance 

between a cloud and the flight path means the shortest slant range between any point on the flight path 

and any part of that cloud. The latter definition is intended to facilitate the separation of standoff 

distances in different sections of a given rule into non-overlapping ranges. For example, "if the flight 

path will carry the launch vehicle less than or equal to N nautical miles from any X cloud" means that 

the flight path must penetrate neither the interior of that cloud nor the volume between 0 and N 

nautical miles, inclusive, outside the cloud boundary. On the other hand, "between 0 and N nautical 

miles, inclusive, from a X cloud" refers only to the volume between 0 and N nautical miles, inclusive, 

outside the cloud boundary but specifically omits the interior of the cloud itself.

"Anvil Clouds" are now restricted to those produced by cumuli having tops colder than

-10 °C.

A new definition of "Cloud" now subsumes the previous "Cloud Edge" and "Cloud Base" (but 

not "Cloud Top," which is re-worded but retained) and is considered to include everything 

inside the nontransparent cloud boundary.

The definition of "Electric field measurement" has been restricted to exclude cases in which 

the flight path is at or above 20 km altitude.
Page 181 of 234

"Nontransparent" and "Transparent" have been reorganized so that the former is defined more 

clearly and the latter is defined as the opposite of the former.

New definitions have also been added for "Radar Reflectivity," "Thick Cloud Layer," 

"Treated," and "Triboelectrification."

"Within" has been eliminated and replaced by the new expressions of distance mentioned 

above.

The definition of "VAHIRR" has been reorganized to separate out the subsidiary definitions, 

"Average Cloud Thickness," Cone of Silence," "VAHIRR Application Criteria," and 

"Volume-Averaged Radar Reflectivity."

Anvil Clouds (G417.11 and G417.13): In both of these rules it has been explicitly stated that all 

waiting times after lightning are considered satisfied if there has never been a relevant lightning 

discharge. Also in both rules, the volume around the flight path in which the VAHIRR threshold (but 

NOT the VAHIRR Application Criteria) must be satisfied has been adjusted so that there is no case 

when VAHIRR is not "applicable" because too little of the cloud in question is within the Specified 

Volume to satisfy the "frac" criterion, which is now given at the end of the "Volume-Averaged Radar 

Reflectivity" definition. For other substantive changes to these rules, the reader is referred to the truthtable comparisons below. The following statements verbally summarize these changes:

Attached Anvil Clouds (G417.11):

Satisfaction of all three VAHIRR conditions now allows flight at all times after the 

last lightning at all ranges (including penetration); whereas flight was previously 

prohibited at ranges ≤ 10 NM for times ≤ 30 min.

If any of the VAHIRR conditions is not satisfied, flight is now permitted between 3 

and 5 NM for times ≤ 3 hr and between 5 and 10 NM for times ≤ 30 min if the 

relevant part of the cloud is frozen; whereas flight was previously prohibited within 

these range and time intervals.

HOWEVER, flight is now prohibited between 0 and 3 NM for times greater than 3 hr 

if any of the VAHIRR conditions is not satisfied -- conditions under which flight was 

previously allowed.

Detached Anvil Clouds (G417.13):

Satisfaction of all three VAHIRR conditions now allows flight at all times after the 

last lightning at all ranges (including penetration); whereas flight was previously 

prohibited at ranges ≤ 10 NM for times ≤ 30 min.

If any of the VAHIRR conditions is not satisfied, flight is now permitted between 3 

and 5 NM between 30 min and 3 hr; whereas a low-field/low-radar condition was 

previously required.

Also if any of the VAHIRR conditions is not satisfied, flight is now permitted 

between 3 and 10 NM during the first 30 min if the relevant part of the cloud is 

frozen; whereas flight was previously prohibited within this range and time interval.
Page 182 of 234

Debris Clouds (G417.15): A VAHIRR condition has now been introduced into this rule. As with the 

Anvil rules, the volume around the flight path in which the VAHIRR threshold must be satisfied has 

been adjusted so that there is no case when VAHIRR is not "applicable" because too little of the cloud 

in question is within the Specified Volume to satisfy the "frac" criterion. For other substantive 

changes, the reader is referred to the truth-table comparisons below. The following statements verbally 

summarize these changes:

Satisfaction of all three VAHIRR conditions now allows flight at all times after detachment 

(independent of lightning) at all ranges (including penetration); whereas flight was previously 

prohibited at ranges ≤ 5 NM for times ≤ 3 hr, with or without conditions.

If any of the VAHIRR conditions is not satisfied, flight is now permitted unconditionally 

between 3 and 5 NM for times ≤ 3 hr; whereas flight was previously permitted within this 

range and time interval only if a low-field low-radar condition was satisfied.

Thick Cloud Layers (G417.19): It is now explicitly stated that anvil clouds are never considered to be thick

cloud layers.

The Triobelectrification Rule (G417.23) now specifically includes transparent clouds. (NOTE that the 

Triboelectrification Rule does not originate in this version. It was omitted from the previous versions analyzed 

here only because they were taken from the Shuttle-Program rule collection, which did not include a 

Triboelectrification Rule.)

21 April 2009 LAP/ABFM III telecon -- Preliminary planning of another ABFM (III) campaign proposal, 

should funding be forthcoming. A final core-proposal was forthcoming from Frank Merceret on 9 July 2009.

24 June 2009 LAP Telecon -- Planning the present LAP/LLCC History/Rationale project.
Page 183 of 234

Figure A2-5 Expanded Space Shuttle LLCC (2005) Attached Anvil Rule
Page 184 of 234

Figure A2-6 Expanded LAP Recommended (10/06/08) Attached Anvil Rule

It .o..LL l VAHIRR 

Nona, 

~ c.ll .ntrv ,r " 00 " .. an. ~h. rul. do.. not .xpllcltly ~~tlon thl. OOndltlo~. 

" roo%.n" .. an. eloud I. ~ld.r than 0 C within pre.~olbed dl.~a~c. roo. rll~ht path . 

Hllow c.lh 1""lIcltly N~ ~< •• n In l~< .... trll , 'Inc. orr, ,.r," U <on. ,r th. VAHIRII 

e<>rdltlou . 

•• It there ha. n.vec ~n _ llqh~nlnq dl.ch~<ge . then thl. tl .. ~rlod .ppll ••• 
Page 185 of 234

Figure A2-7 Expanded Space Shuttle LLCC (005) Detached Anvil Rule

No t .. , 

... c.ll .ntey ,( " •• " _on. th. <~l. do.. not .~pl1c1~ly Mn lon hll eo,xHUon . 

" Low n.ld" _on. (01 II 'otOr<l nq .. Ill <~ n.,1 fro .. <'lou<!, Ibl <1000 VI. fo< 15 lOin n 011 aill. 

'5 n.1 «0. fll~h' p~'h AND ~t _11 1 1.) In (.) , .nd Ie) cloud I. <I( dBt ,& n.1 feo. (ll~h' ~th [ or 

15 .In . 

• T~I. e.ll II "',bl~Y • I>oo'-.n netlons 10J. ..t'Ileh .. y. No t..oun • • r>d Ie) ""I<:~ uy. 

t..ounch NQt PrQhlbl'~ • 

• • II t~.r. ha. n.ve< booen 0 11~htnlnq dl.cha~e , then thl. tiM period .ppll •• . 
Page 186 of 234

Figure A2-8 Expanded LAP Recommended (10/06/08) Detached Anvil Rule 

No t .. , 

~ c.ll .nt~y ,r - •• " ~ana the rule does not ~xpllcltl y .entlon thl. condition . 

" rrozen" N4an. eloud I. colder ~han 0 C wl~hln prescribed dl.tance !roa f l lQht path. 

" Low Field" __ n. (_I :>1 "or<lnQ .Ill <5 n",1 fro", do""' , (b l <1000 VI. for U .. \n U all .,Ilh 

H nal trOJO tll9M pUh.>.NO U .. 111(.) In (a) . and (c) cloud I. <I Q dBt H nOli !r_ !llQht pa t h for 

15.ln. 

80_ ~ll.".. oelh 1000lIcitly lacoooe Qr~en In lower ... trl, • • Ince " F<oun" 11 :.. o f lhe V"-Hl!U't 

condl tiona . 

• • If thH. hu n.VH been a lIQMnlnQ dlaehar9~ . th~n thl. ti_ ""dod ~ppl1 ... 
Page 187 of 234

4-6 August 2009 LAP Meeting at KSC -- LAP/LLCC History/Rationale first formal meeting:

Facing the probable resignation of Dave Rust, the LAP considered potential new members to invite. 

(As of 18 December 2009 it appears that Dave Rust will not resign, so this issue is moot.)

There is a need for the LAP to serve the entire space community beyond the retirement of Shuttle. 

John Madura and Frank Merceret indicated plans to continue in the KSC Weather Office until 2013.

Karen Shelton-Mur (FAA/AST) had requested to attend the LAP meeting on the LLCC rationales, 

apparently to ask general questions. It was decided to request salary and per diem from the FAA to 

add a day to the working meeting for that purpose.

Frank Merceret will set up regular recording of LLCC violations (or lack thereof) during all 

countdowns.

The LAP made a formal request to the KSC Weather Office and the 45WS for the above and also for 

recording of any high-field readings without explanation.

The History Document is due end of December 2009. The Rationale Document is due end of 

September 2010.

History Topic:

Three chronologies are needed: LLCC origin and evolution (and co-evolution of FAA rules), 

weather/atmospheric-electrical instrumentation at KSC, and organizational structure of 

weather support at KSC.

Numerous assignments of responsibility were made.

Rationale Topic:

A starting point might be the rationale outline in Krider et al. (2006, Section 3.2.2) -- needs 

updating to current (10/6/08) version of LLCC.

Cloud electrification -- starting point might be Krider et al. (2006, Section 3.2.1). Details go 

into an appendix.

The development of ideas about triggered lightning: When and how was it first realized that 

triggered lightning was a threat to space launches? What is now known about triggering 

conditions? (Starting point might be Krider et al. (2006, Sections 2.2 and 3.1) -- details go 

into an appendix.)

Key rationale problem will be the thick-cloud rule, because it appears to be based on and 

referenced to nimbostratus, but there is new data from the ABFM I experiment.

Numerous assignments of responsibility were made.

2 Sep 2009 -- John Madura relayed via e-mail a question to the LAP from Tim Oram (JSC/SMG), echoed by 

the 45WS, about the new anvil rules. This question was viewed as urgent, since John indicated that it was 

delaying implementation of the latest LLCC. Phil Krider was out of the country at the time, but the question 

was addressed by Jim Dye and John Willett with e-mail review by Phil but without formal discussion among 
Page 188 of 234

the entire LAP. An informal e-mail response was sent to John Madura and others by John Willett and Jim Dye 

on 18 September 2009. Below is a key quotation from that response:

"The rationale for relaxation of the rules relative to time after lightning is essentially that the ABFM II 

dataset includes a large proportion of clouds in which (or in whose parent clouds) lightning was 

actively occurring during the aircraft penetrations. There was no apparent distinction between the 

clouds that did and that did not contain lightning as far as launch safety was concerned. The changes 

were made on the assumption that ALL of the LLCC must be satisfied as a package. There was never 

any intention to allow flight within 10 nmi of lightning."

John Madura replied that this response was adequate and closed the LAP issue.

24 October 2009, Current Space Shuttle LLCC (adopted 2009) [LCN WEA-1, see Appendix I, Section A1.11] 

-- A new version of the LLCC that is essentially equivalent to the version approved by the LAP on 2 October 

2008 was implemented by the Range. Aside from numerous wording changes to translate from FAA to Range 

terminology, and reversal of the order to put the definitions at the end (counterbalanced by a statement at the 

beginning emphasizing that they are an integral part of the rules), there are only the following substantive 

changes:

The LAP wording, "Whenever there is ambiguity about which of several LFCC applies to a particular 

situation, all potentially applicable LFCC must be applied," is not echoed by any similar wording in 

the Range version (although this is current practice at the Eastern Range).

The Range wording, "Even when these criteria are not violated, if any other hazardous condition 

exists, the LWT will report the threat to the Launch Director (LD). The LD may Hold at any time 

based on the instability of the weather," does not correspond to any similar wording in the LAP/FAA 

version. [Note that although the familiar “Good Sense Rule” is omitted from these proposed LFCC as 

presented here, essentially the same wording does appear in another section of the current FAA LFCC 

implementation where it is still a mandatory requirement. See Appendix I, A1.12 and A1.13. The LAP 

expects that this requirement will remain in the regulations as the LFCC are updated by the FAA.]

The LAP reference in the "preamble" to the definitions, "(See also the additional explanation beneath 

the definition of 'cloud.')," to additional explanation of distance measurements is missing from the 

Range-approved version.

The LAP definition and rule for Triboelectrification has been removed by the Range (presumably 

because Shuttle has been hardened against triboelectric hazards).
Page 189 of 234

Figure A2-9 Expanded Space Shuttle LLCC (2005) Debris-Cloud Rule

"~t'" 

_,. 0 'U". -1l6fR ~I:'cl. _CI -' R .h' 

• 

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Thl. ~ul. do •• not Invo •• VAHIR~ , .0 ~he ~wo panel. are Identical . 

" Lo" field " .. a~. la) "1 ""rkln~ .. Ill <~ fIlIIl teca cloud . Ibl <1000 Vf. for I~ .In at all .1l1o 

S;~ n.1 fro. fl19M path NlD .. 1111111.) In (., • • nd Ic) cloud I. <10 dBZ'~ "",I fro .. !119M path foe 

15 _In • 

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fl.ld·.lll axc~llon • 

••• 1he th~ •• '~~< ".ltlnQ p*rlod b4qln. a~.ln If 11~h~nlnQ Occur. In the d~b~l. 'loud . 
Page 190 of 234

Figure A2-10 Expanded LAP Recommended (10/06/08) Debris-Cloud Rule
Page 191 of 234

Appendix III Members of the PRC/LAP

Christian, Dr. Hugh J. (1999 to present)

Principal Research Scientist

University of Alabama in Huntsville

Dr. Christian specializes in the observation and measurement of electrical phenomena in the atmosphere 

through in situ and remote sensing techniques. His expertise includes ground-based and airborne field mill 

measurements, cloud electrical structure, techniques for location of lightning using ground-based 

electromagnetic remote sensing, and location of lightning using space-based optical remote sensing. He has 

authored or co-authored numerous conference papers and peer-reviewed journal articles.

Member of Busse Committee after the AC 67 incident; Principal Investigator of ABFM I experiment; LAP 

member since 1999; planning and oversight of the ABFM II experiment; NASA perspective.

Dye, Dr. James E. (2002 to present)

Senior Scientist Emeritus 

National Center for Atmospheric Research, Boulder, Colorado

Dr. Dye is an internationally recognized leader in cloud physics, atmospheric electricity, airborne

instrumentation, polar stratospheric clouds, production of nitrogen oxides by lightning, and use of both intracloud and cloud-to-ground lightning for characterizing severe storms. He has worked extensively in the design, 

direction, participation and data analysis of coordinated multiple aircraft--radar studies of thunderstorms using 

both powered aircraft and an instrumented sailplane; and the development and evaluation of airborne cloud 

particle measuring devices and liquid water content sensors and has participated in or led more than 20 

national and international field experiments. He has published over 90 refereed journal articles, reports or 

chapters in books and over 125 conference publications and reports. He is a fellow of the American 

Meteorological Society, a member of the American Geophysical Union, a former editor of the Journal of 

Geophysical research and former Associate and Acting Editor of the Journal of Atmospheric and Oceanic 

Technology.

Principal Investigator of ABFM II experiment; PRC member initially and LAP member since 2003; academicresearch perspective.

Krider, Dr. E. Phillip, Chairman (inception to present)

Professor, Department of Atmospheric Sciences and Institute of Atmospheric Physics

The University of Arizona

Dr. Krider is an author or co-author of more than 130 reviewed publications, and he has 8 patents. He is a 

Fellow of the American Geophysical Union (AGU) and the American Meteorological Society (AMS), and a 

Member of the American Association of Physics Teachers and the History of Science Society. Dr. Krider 

received the AMS award for Outstanding Contributions to the Advance of Applied Meteorology in 1985, and 

he currently chairs the NASA/Air Force Lightning Advisory Panel for space launch operations. Dr. Krider is a 

former Co-Chief Editor and Editor of the Journal of the Atmospheric Sciences, former Associate Editor of the 

Journal of Geophysical Research, and he is a past President of the IAMAS/IUGG International Commission 

on Atmospheric Electricity (ICAE).

Participated in Apollo XII investigation; member of Aerospace (Heritage)and NAS/NRC Committees after AC 

67; Chairman of the PRC/LAP since its inception; planning and oversight of all LAP-proposed field 

experiments and direct participation in the ABFM II at KSC; academic perspective.
Page 192 of 234

Koons, Dr. Harry C. (inception to 2005, deceased)

Distinguished Scientist

Space Applications laboratory, Aerospace Corporation, El Segundo, CA.

Fields of specialization include magnetospheric physics, spacecraft charging, spacecraft environmental 

anomaly investigations, very-low-frequency propagation, wave-particle interactions, and active experiments in 

space. He pioneered the use of expert systems and neural networks in areas related to the space environment. 

He was an investigator for space flight experiments on the OV1-21, SCATHA, AMPTE and CRRES 

spacecraft. Dr. Koons was a member of the American Geophysical Union, the Union of Radio Science, the 

American Association for the Advancement of Science, the American Institute of Aeronautics and 

Astronautics and the Society of Sigma Xi.

Statistical analysis of ABFM II dataset; LAP member continuously from its inception until his death; Air 

Force-research perspective.

O’Brien, Dr. T. Paul (2007 to present)

Aerospace Corporation, El Segundo, CA.

Paul O'Brien received his B.A. in Space Physics and Astronomy from Rice University in 1997. Dr. O'Brien 

received his MS degree in 1999 from UCLA, and completed his Ph.D. in 2001 under Dr. Robert McPherron in 

the area of Geophysics and Space Physics. His work with Dr. McPherron focused on geomagnetic storms as 

space weather with focus on the ring current and trapped energetic electrons. During a 1-year post-doc at 

UCLA Dr. O’Brien worked part time with Dr. Didier Sornette covering a broad range of complex systems, 

from helicopter engines to earthquakes. At Aerospace Corporation he continues to work actively on the 

radiation belts, ring current, and other phenomena in the inner magnetosphere, with emphasis on the 

application of space science results to tools for spacecraft design and situational awareness. Dr. O'Brien's work 

frequently uses statistical, nonlinear and artificial intelligence methods for analyzing large data sets to describe 

the magnetosphere.

Statistical analysis of ABFM II dataset; LAP member continuously since 2007; Air Force-research 

perspective.

Rust, Dr. W. David (inception to present)

Physical Scientist

National Severe Storms Laboratory

Dr. Rust coauthored the graduate level text and professional reference book, “The Electrical Nature of 

Storms.” He has pursued research that covers topics ranging from the electrical structure of storms to 

lightning. He is internationally recognized as an expert in making balloon-borne measurements of electrical 

parameters in storms using free-flying, instrumented balloons, and has significant experience in the 

development and use of mobile laboratories to conduct research requiring the ability to collect data while 

tracking with storms. He has been served on the Lightning Advisory Panel, and its various predecessor groups, 

addressing atmospheric electricity launch issues since Apollo-Soyuz.

Member of the Aerospace (Heritage) Committee after the AC 67 incident; PRC/LAP member since its 

inception around 1990; planning and oversight of all LAP-proposed field experiments and direct participation 

in one at KSC; NOAA perspective.
Page 193 of 234

Walterscheid, Dr. Richard L. (inception to present)

Senior Scientist

Space Sciences Department, Aerospace Corporation, El Segundo, CA.

Dr Walterscheid has extensive experience in weather and the meteorology of cloud electrification. His 

experience in weather includes service as a Weather Officer and Aerospace Sciences Officer for the Air Force 

Air Weather Service and an Interagency Personnel Act assignment to the National Oceanic and Atmospheric 

Administration. His work related to lighting includes aviation forecasting of thunderstorm activity in Florida, a 

study of triggered lightning strikes to aircraft in Europe, and long-standing service on the NASA and Air Force 

Lighting Advisory Panel and its predecessors since 1987. His research work in the physics and dynamics of 

the atmosphere has led to approximately 130 peer reviewed publications. Dr. Walterscheid is a member of the 

American Geophysical Union, the American Meteorological Society, and Phi Beta Kappa.

Member of the Aerospace (Heritage) Committee after the AC 67 incident; PRC/LAP member since its 

inception about 1990; planning and oversight of all LAP-proposed field experiments; Air Force research 

perspective. 

Willett, Dr. John C. (inception to present)

Consultant in meteorological sciences

Dr. Willett has extensive experience in lightning physics, atmospheric electricity, and boundary-layer 

meteorology. He has served as a senior physicist at the Air Force Research Laboratory, a NRC Senior 

Research Associated at NASA/GSFC, and a meteorologist at the Naval Research Laboratory; and he was an 

Adjunct Professor in the Meteorology Department at the University of Maryland. He has served as a member 

of the USAF/NASA Lightning Advisory Panel from 1992 to the present, as chairman of the American 

Geophysical Union Committee on Atmospheric and Space Electricity from 1992 to 1996, and as an Associate 

Editor for JGR Atmospheres for two four-year terms. He has also served NASA/KSC as a member of both the 

Review Panel on the Rocket-Triggered Lightning Program and the Advisory Panel on Upgrading the Field 

Mill System. He has numerous publications on atmospheric electrical and lightning research.

PRC/LAP member since its inception around 1990; planning and oversight of all LAP-proposed field 

experiments; Navy/Air Force perspective.
Page 194 of 234

Appendix IV ABFM I Science Team and Key Results

Dr. Monte G. Bateman, NASA Global Hydrology and Climate Center, Marshall Spaceflight Center

Dr. Hugh J. Christian, NASA Global Hydrology and Climate Center, Marshall Spaceflight Center

Dr. Douglas M. Mach, NASA Global Hydrology and Climate Center, Marshall Spaceflight Center

Launa Maier, NASA, KSC

Key Results:

ABFM I Winter studies (MSFC Feb 92 and Oct 92 reports and Mach et al., 1992)

• For layer clouds a strong correlation was found between electric fields inside the clouds and vertically 

integrated radar reflectivity (VIR).

• Fields at the surface were not always correlated with fields aloft in layer clouds.

• The lowest altitude with fields >=5 kV/m was 13 kft and the highest altitude with fields >=5 kV/m 

was 20 kft (~-10 oC) suggesting that the main area of hazard was between 0 and -10 oC

• For disturbed weather clouds there was a strong correlation between the electric fields aloft and VIR.

• For disturbed weather clouds all penetrations with fields >5 kV/m were between 10 and 21 kft 

(approximately 0 to -10 oC).

• Fields measured at the surface below disturbed weather clouds correlated well with fields aloft, but 

there were 3 exceptions where fields at the surface were <1 kV/m and fields aloft were >5 kV/m.

• Penetrations with fields > 3kV/m were generally associated with regions of higher reflectivity 

(embedded convection).

• Cloud thickness and electric field strength were very poorly correlated.

ABFM I Summer studies

• The fields outside of storms with lightning fell over to <5 kV/m at a range of 5 nm.

• For cumulus clouds, the electric fields depended strongly on the cloud top height. Fields in clouds with 

10 dBZ tops lower than the 0 oC level did not exceed 3 kV m-1

. Fields >3-5 kVm-1 did not develop in 

the clouds until the echo tops had grown higher than the -10 oC level. The clouds did not produce 

lightning until the tops were higher than the -20 oC level. Fields at the edge of clouds with echo tops 

higher than the -20 oC level could be > 50 kV m-1

.

• When clouds were within 5-6 nm of the Ground Based Field Mill network there were no cases when 

the fields aloft were >5 kV/m and fields at the surface were <1 kV/m.

• Even with fields of tens of kV m-1 inside electrically active convective clouds, the fields external to 

these clouds decayed to < 3 kV m-1 within 15 km of cloud edge. This was true even for clouds that 

were producing lightning with tops above -20 oC.
Page 195 of 234

Appendix V ABFM II Science Team and Key Results

All LAP Members listed in Appendix III were part of the ABFM II Science team.

Other Members:

Dr. Monte G. Bateman, USRA, Huntsville, AL

Dr. Dennis Boccippio, NASA, MSFC

Dr. Eric Defer, NCAR

Dr. Cedric A. Grainger, University of North Dakota

Dr. William. D. Hall, NCAR

Sharon A. Lewis, NCAR

Dr. Douglas M. Mach, University of Alabama at Huntsville

John Madura, NASA, Kennedy Space Center Weather Office

Dr. Francis J. Merceret, NASA, Kennedy Space Center Weather Office

Natalie Murray, University of Arizona

Michael Stewart, NASA, MSFC

Paul T. Willis, NOAA, Hurricane Research Division

Jennifer G. Wilson, NASA, Kennedy Space Center Weather Office

In addition, the winter 2001 cloud radar team from NOAA/ETL included Brooks Martner and Bruce Bartram.

Key Results:

• An extensive set of airborne measurements of electric field; particle concentrations, sizes and types 

were obtained in coordination with radar reflectivity measurements in anvils and debris clouds.

• The measurements showed that when electric fields were strong (> 10 kV/m) the radar reflectivity at 

or near the aircraft location was always high (>5 to 10 dBZ), but high reflectivity did not always mean 

that the electric field was strong.

• Similarly, when electric fields were strong, the particle concentrations in all size ranges from ~10 

microns to several millimeters were also high.

• The transition from weak fields (< 1 kV/m) to strong fields (>10 kV/m) inside the anvil and debris 

clouds occurred quite abruptly and this transition usually occurred as the aircraft flew from weaker 

reflectivity into regions with reflectivity greater than approximately 10 dBZ.

• As a manifestation of the abrupt transition from weak to strong electric field, scatter-plots of electric 

field versus reflectivity for the entire anvil and debris cloud data set exhibited a threshold behavior 

such that for fields ~<3 kV/m the reflectivity was weak.
Page 196 of 234

• Using the above finding as a basis, the radar based parameter, volume averaged height integrated radar 

reflectivity (VAHIRR) was developed. VAHIRR is the product of the average reflectivity times the 

anvil/debris cloud thickness above the 0 oC level.

• In some long-lived anvils a secondary stratiform-like development was observed in which both 

electric field and reflectivity became enhanced and persisted for periods more than an hour over large 

areas. Even in these conditions VAHIRR was able to identify regions with strong electric fields.

• Measurements near anvil or debris cloud edges clearly showed that particles extend out to or beyond 

the 0 dBZ radar contour and well beyond the 10 dBZ radar contour. As a result of these observations 

the LAP changed the definition of “anvil edge” in the LLCC rules from +10 dBZ to 0 dBZ.

• A simple model was developed to estimate the decay of electric field in the ABFM anvils based upon 

the actually observed particle size distributions. The estimates from the model show that the time for 

the electric field to decay from 50 kV/m to near zero can be as long as 1 1⁄2 hours in the dense part of 

an anvil, but as short as only a few minutes in weak reflectivity near the edge of the anvil. These 

estimates are considered to be upper limits.

• Comparisons for case study days of electric field decay time scale from the model were generally 

consistent with observed decay times, but only one ABFM anvil case permitted a meaningful 

comparison.

• In anvil and debris clouds observed during ABFM II the electric field fell off rapidly from the cloud 

edge to values <1 kV/m by 8 km distance from the edge.
Page 197 of 234

Appendix VI Apollo XII Timeline

Launch of Apollo 12 occurred on 14 November 1969 at 16:22 UT (Returned to Earth on

24 November 1969 at 20:58 UT)

Two lightning strikes occurred after lift-off, a 2-stroke CG flash (with two ground terminations) recorded on 

video at T+36.5 sec and an IC discharge occurred at T+52 sec.

November 15, 1969 NY Times (page 22, col. 1) ‘...aircraft reported that there seemed to be no electricity in the 

clouds.'

November 17, 1969 Dr. Richard E. Orville drafted letter to NY Times pointing out that lightning can be 

‘initiated by towers and tall buildings ... and perhaps by a fueled rocket launching astronauts toward the 

moon.’

November 24, 1969 Article by B. K. Thomas, Jr. appeared in Aviation Week and Space Technology with the 

title ‘Power Source Loss Marks Apollo Launch’ illustrates initial confusion about the cause of incident. 

Mentions possibilities like ‘discharge of static electricity,’ ‘vibration during launch phase opening circuit 

breakers,’ and ‘vehicle had been struck by lightning. But this was considered remote because the effects would 

probably have been more severe than those actually experienced, according to Walter J. Kapryan, KSCs 

launch director.’

November 26, 1969 Informal Seminar and Discussion on The Apollo 12 Lightning Flash was hosted by Dr. 

Arthur A. Few, Jr. at Rice University on the occasion of a visit to MSC by Dr. Orville.

December 4, 1969 ‘Meeting on AS-507 Lightning’ held at Marshall Space Flight Center (MSFC) hosted by 

Glenn E. Daniels (S&E-AERO-YT) to discuss: Magnitude of the lightning hazard to a Saturn V vehicle in 

flight; Mechanism of atmospheric electrical charge and discharge on the Saturn V vehicle in flight; and What 

launch operational constraints should be imposed to prevent a reoccurrence of the incident.

December 5, 1969 Open letter by Dr. Few to the scientific community working on lightning physics and 

related questions stating that arrangements had been made with the AGU and the NASA-MSC to have a 

Special Session at the upcoming Fall AGU Meeting to obtain more ‘hard’ information on the Apollo 12 event.

December 8, 1969 Letter by Dr. Andrew E. Potter (NASA-MSC) to specialists in relevant areas announced 

that there would be an Open Meeting at the Jack Tar Hotel (venue for the Fall AGU meeting) at 12:15 PM on 

December 16 where the facts available on the Apollo 12 lightning incident and its effects on the spacecraft will 

be presented. Ernie Amman, the ESSA weather forecaster working at KSC at the time of the incident, will 

review the meteorological situation at the time of the launch. Potter also mentioned an invitation to a ‘small 

discussion group’ would be held at 5:00 PM to cover specific questions such as: Would these discharges have 

occurred in the absence of the rocket launch, or were they triggered by the rocket? Can the magnitude of the 

vertical electric field and the intensity of rainfall at the launch site be used to indicate hazardous launch 

conditions? Is it possible to define a characteristic weather pattern which might yield rocket-triggered lightning 

discharges? Are additional and/or improved measurements necessary to estimate the probability of lightning 

during a launch? (A list of the people who were invited to the ‘small group’ discussions are acknowledged at 

the beginning of the Preface to the MSC-01540 Report.)

December 9, 1969 M. Brook, C. R. Holmes, and C. B. Moore of New Mexico Tech draft a Technical Note 

entitled ‘Exploration of Some Hazards to Naval Equipment and Operations Beneath electrified Clouds’ for the 
Page 198 of 234

Office of Naval Research (ONR) under Project Themis. This note was subsequently published as Appendix 2 

in NASA Report MSC-01540, February 1970, and in the ONR Naval Research Reviews, April 1970.

December 16, 1969 The special session and subsequent discussions were held at the Fall AGU Meeting and 

were Chaired by Donald D. Arabian.

December 22, 1969 An article appeared in Aviation Week entitled ‘Apollo 13 Launch Rule Changes Will Be 

Recommended to NASA’ (also mentioned an article in the December 8 issue, p. 52) where D. Arabian is 

quoted as saying ‘We have to take the state of the art and apply it.’

December 23, 1969 Rocco A. Petrone, the Apollo Program Director at NASA Headquarters, called on the 

MSC, MSFC, and JSC to resolve the Apollo 12 electrical discharge incidents before the Apollo 13 Flight 

Readiness Review (FRR) on February 5, 1970. Scheduled an LDX meeting with MSC/KSC/MSFC and 

Headquarters on January 22, 1970 (this may have subsequently been postponed to February 6). Petrone asked 

for the MSC (Don Arabian) to coordinate the efforts of the three NASA centers in drafting this report.

December 30, 1969 Memorandum from W. O. Campbell of Bellcomm, Inc. on ‘Apollo 12 Launch Weather’ 

compared Apollo 12 launch weather conditions with mission rules and noted that the candidate rules for 

lightning avoidance then under discussion ‘suffer generally from ambiguity, lack of objectivity, and depend to 

some extent on local forecasting experience.’

January 7, 1970 Arabian memo ‘Reporting of the Apollo 12 lightning incident’ sent to W. Vaughan (MSFC) 

and H. Clark (KSC) suggesting eight specific chapters for the Apollo 12 report.

January 8, 1970 KSC Systems Engineering responded to request from H. J. Clark and provided:

Description of the present Lightning Instrumentation

A summary of the ESSA Research Studies then underway

Proposed instrument changes for the Apollo 13 launch

Past history of lightning strikes at the LC-39 (500F) launch site

January 13, 1970 Dr. Robert Manka (MSC) summarized recommendations for ‘Methods of Measuring Electric 

Fields’ that were discussed at the AGU Meeting on December 16. Ground-based and airborne measurements 

were considered. Stated that preliminary ‘hazardous field levels’ are between ±1 and ±3 kilovolts/meter. Need 

to obtain relationships between airborne and ground-based electric fields and values of the ‘critical electric 

field’ inside clouds.

January 14, 1970 Memo from W. J. Waugh, Manager of Spacecraft Engineering at Boeing-Houston, to D. 

Arabian on ‘Apollo 12 Electrical Power Transient During Boost Anomaly.’ Reviewed environmental factors 

at the time of the Apollo 12 launch and gave specific recommendations for ‘operationally practical mission 

launch rules’ with associated rationale.

January 14, 1970 D. Arabian invited (through E. P. Krider) M. Brook, D. Fitzgerald, G. Freier, C. B. Moore, 

and E. T. Pierce to meet at MSC on January 21-22, 1970, ‘to discuss further the problem of forecasting 

lightning hazards to Apollo launches. Particular emphasis will be placed on electric field measurements, 

sferics detection, and radar observations.’

January 21-22, 1970 Above meetings were held at MSC.

January-February, 1970 MSC-01540 Report was written.
Page 199 of 234

January 30, 1970 MSFC releases MPR-SAT-FE-70-1, ‘Saturn V Launch Vehicle Flight Evaluation Report 

AS-507 Apollo 12 Mission.’

February, 1970 Report on ‘Analysis of Apollo 12 Lightning Incident’ (MSC-01540) released by the MSFC, 

KSC, and MSC. Contained LLCC that ‘will satisfy the low risk requirements of the spacecraft and the lesser 

restrictions of the launch vehicle’ (p. 50).

February 2, 1970 Arabian announced that an LDX meeting on the Apollo 12 lightning will be held between 

NASA Headquarters, MSFC, KSC, and MSC on February 6, 1970. This meeting covered

• Precisely what happened

• Cause of the incident

• Hardware and software changes

• Instrumentation to improve identification of potentially hazardous electric fields

• Adequacy of automatic abort system and ordnance device for lightning

• Recommended changes in the launch rules

February 4, 1970 Memo from GE Apollo Systems Department described some telephone contacts that were 

made with Drs. Brook, Freier, Moore, and Fitzgerald who were asked “Are you aware of any documented 

violation of the 1 to 1 cone used for protection against direct lightning strokes?” (These were initiated in 

response to questions about the efficacy of lightning protection at the launch site.)

March 19, 1970 Memo from Drs. R. H. Manka and A. E. Potter to D. Arabian detailing consensus suggestions 

for the type of electric field sensors and other ground-based instrumentation to have at KSC (and their 

calibration). Also, recommended a ‘small, low-power radar with range-height indicator’ that could provide 

rapid scans in elevation (3 to 5 seconds per scan) through the vertical, and slowly in azimuth (about 2 to 3 

minutes per hemisphere).

April 22, 1970 Special Session held at Spring AGU Meeting on ‘Triggered Lightning/Atmospheric Electricity’ 

that was Chaired by B. Vonnegut and M. Brook. 16 abstracts of papers were published in EOS, Vol. 51, No. 4, 

April 1970.

May 21, 1970 Summary of a ‘Special Discussion’ that followed the above AGU session (prepared by Drs. 

Krider, Manka, and Freden) indicates that the discussion was divided into three parts:

i) Comments on the launch rules that existed then (i.e. after Apollo 12);

ii) Instrumentation that was required to implement the launch rules; and

iii) Experiments which would be desirable during future launches.

May 22, 1970 James Hughes (ONR) visited D. Arabian (who was busy with Apollo 13 problems) in Houston 

asking whether the Kennedy Space Center could be used to study the atmospheric electrical environment at 

KSC, cumulus clouds as they make transitions between land and sea, and electrical phenomena that are 

associated with the launching of rockets.

June 19, 1970 KSC Memo from Manager, Apollo-Skylab Programs (Brigadier General, USAF, Thomas W. 

Morgan) to MSFC (L. B. James) and MSC (J. A. McDivitt) on ‘KSC’s Role – Research in Atmospheric 

Electricity.’ Realized that additional efforts are required and that additional efforts will be ‘somewhat useless 

to NASA and other agencies if not properly integrated such that a user (launch site, such as KSC) can utilize or 

implement results into present and future operational programs.’
Page 200 of 234

Appendix VII Evolution of the Lightning Instrumentation at CCAFS

This appendix provided by Michael W. Maier, of the Range Technical Services Contractor, CSR. It includes 

his personal recollections as an active participant in the events described.

Mid-Late 1960’s (Prior to Apollo 12)

NASA deploys eight radioactive probe electric field meters at KSC manufactured by the Sweeney 

Corporation. Date of initial installation unknown, but they were operating when Apollo 12 was launched in 

November 1969. NASA also deployed eight corona current detectors (4 ft whip antenna connected to a 

microampmeter) at the same sites as the radioactive probes and operated a two station sferics locating system. 

Five of the eight were located on the ground (1.5 m above grade) and three on buildings (VAB, MSOB which 

is I think now called the O&C Building, and one other unnamed building). There is a map of stations in the 

Apollo 12 event report (NASA TM-X-62894)

There was much discussion of the calibration of these instruments (see Calibration of Atmospheric Electric 

Field Meters and Determination of Form Factors at Kennedy Space Center, by H. W. Kasemir, ERL APCL-11, 

April 1971). Kasemir concluded the maximum field values at the surface during the one hour prior to the 

Apollo 12 launch were ±4 kV/m. He also noted the instrument at Site 8 located at the pad recorded fields of -

3.2 kV/m from the steam cloud at the pad during launch of Apollo 12 launch and +3.7 kV/m during Apollo 13 

launch on a fair weather day.

1969

November 14 - Apollo 12 struck by lightning at 36.5 seconds (6400 ft vehicle altitude) and 52 seconds (14400 

ft vehicle altitude) after liftoff. Mission comes within seconds of abort due to loss of all telemetry when 

ground controller John Aaron suggests Astronaut Alan Bean select AUX setting on spacecraft signal 

conditioning equipment.

1970-1972

NASA deploys 25 field mills designed by George Freier of the University of Minnesota Physics Department at 

sites on KSC. These would later be designated the NASA Phase I instruments. The specification is found in 

KSC-SPEC-M-0007, Specification for Lightning Instrumentation System at KSC. The system begins 

operating on 1200 ET 28 July 1972. The initial transmission format from the site to the CIF was FSK. The 

FSK signals were not transmitted continuously, the CIF sent a 1.5 s long interrogation signal to all mills and 

then each mill responded following a preprogrammed delay so not two sites would be transmitting at the same 

time. Not sure what the actual sample time was.

The instruments were implemented in the original “two box” site design where the rotor, stator, and motor 

located in one box (at the center of the cleared area) with a second box located on the edge of the cleared area 

containing the signal conditioning circuit cards. The FSK signals were hard wired to the CIF PCM Data 

Station (Room 323) for conversion, recording and display. The data from up to eight instruments mills were 

converted to analog and could be plotted on Brush strip chart recorders. The PCM data was also transmitted to 

the Meteorological Predication Center (MPC) CIF for use by the NOAA SMG team resident at KSC.

1973

Calibration procedure for the NASA field mill is described in GP-1019 (Rev 1) dated 25 July 1973. 

Instruments should have a Vout of +8V when +957.6 V is applied to a plate 2.1 cm above the rotor.
Page 201 of 234

1972-1976

Sometime during this period the CIF function was relocated to the Central Measurement Data Processing 

System (CMDPS) in Rooms 2P19 and 2P20 of the LCC and the first real-time computer processing of the data 

began. I believe this was also when the interface to the NASA RDS 500 computer was established (the LCC 

Environmental and Special Measurement System) and digital processing and display of the KSC field mill 

data began with a real-time contouring program developed by Elmer Magaziner of NOAA ERL.

The AFETR installed a network of eight electrostatic field mills of a type different than the 25 NASA 

instruments in the early 1970’s. The system is described as the Launch Pad Lightning Warning System 

(LPLWS) in the July 1976 Range Instrumentation Handbook (and not in the 1965 handbook). The eight mills 

on CCAFS were located at Pad 41, Pad 40, Pad 13, Weather Station, Pad 36, Pad 17, Pad 25, and the Navy 

Port. There was also one field mill at PAFB which I recall seeing when I visited there in the 72-75 time frame. 

Data were processed by the AFETR CDC 3100 computer in real-time with a teletype output. There were also 

strip chart outputs in the Cape Canaveral Forecast Facility (CCFF) at the Range Control Center (RCC).

NASA documentation is confusing about the number of field mill sites during this period. It appears there 

were more than 25 instruments (or sites) but only 25 could be processed by the RDS computer. I have a couple 

different maps showing different configurations for manned launches versus unmanned launches. It appears 

NASA may have moved some of the instruments to sites on Air Force property just prior to STS 1 to provide 

better coverage since the ESMC mills were concentrated around the ELV pads.

1974

Phil Krider recommends NASA increase the calibration plate spacing from 2.1 to 10.0 cm based on his field 

comparisons from that summer. He reported the 2.1 cm spacing was too small to provide an accurate 

calibration since the rotor to stator spacing of the NASA mills varied from instrument to instrument by 4 mm 

(between 2 to 6 mm spacing). He also recommended that NASA improve the spacing between adjacent stator 

plates on the “second lot” of field mills. The second lot was made with larger stators and the spacing between 

adjacent stators was so small that rain drops would short the adjacent sectors during heavy rain leading to 

about half the network becoming inoperative during heavy rain.

1975

GP-1019 is revised in May 1976 (Rev 2) and still calls for a nominal Vout of 8.0V when 984.4 V is applied to 

the calibration plate with 2.1 cm spacing so evidently the increase in plate spacing recommended by Phil 

Krider was not implemented at this time.

In April NASA did field testing of mills with 10 cm calibration plate spacing. This larger spacing must have 

been implemented at some time between 1975 and 1986 when I worked for Pan Am since it was close to 10 

cm in 1986. I wasn’t aware of GP-1019 or the change to 10 cm and I didn’t measure it until 1990 when it was 

9.4 cm. I don’t have any drawings or records of when it changed.

1976

Charlie Moore and Steve Friberg of New Mexico Institute of Mines and Technology conduct an independent 

evaluation of the absolute calibration of the 25 KSC field mills. They place a portable reference instrument 

next to each KSC mill and compare data under fair weather conditions. They find the mean ratio of all 

collocated mill readings was 0.97 with a standard deviation of 0.31. However, the mean differences between 

the NMIMT reference mill and the NASA mill varied from 0.52 to 2.29. As a result of this test NASA 

considered the KSC field mills to be correctly calibrated in an absolute sense but the validity of individual site 

measurements suspect due to either maintenance problems or exposure variations.
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1980

Prior to STS 1 NASA and ESMC begin sharing field mill signals but there are two parallel real-time 

processing systems, the NASA RDS 500 system in the LCC and the ESMC Cyber 74 at CCAFS. The Cyber 

74 was now running a version of the NOAA contour plotting software which was displayed on a Tektronix 

terminal in the CCFF. The CCFF also has two eight pen strip chart recorders and could plot in real-time data 

from up to 16 mills selected using front panel switches on the console corresponding to the PCM channel IDs.

Agreement was reached between NASA and ESMC that all real-time field mill processing would move to the 

ESMC system as soon as it could be verified and proved reliable. Much effort was spent in comparing the 

outputs of the two different mill types and the two different display systems.

Also in 1980 Phil Krider recommended NASA and USAF implement a real-time delta E plotting capability to 

locate the charge centers and work begins to code this into the ESMC software. By this time, Krider had also 

recommended that the protection diodes on the input of the field mill electronics be removed because they 

introduced an irritating non-linearity in the field mill output that had to be corrected with software. By this 

time, Krider had also recommended that the protection diodes on the input of the field mill electronics be 

removed because they introduced an irritating non-linearity in the field mill output that had to be corrected 

with software.

1981

Operation and maintenance responsibility for the 25 NASA field mills was transferred to ESMC who in turn 

tasked Pan Am World Services to perform this function under the Range contract. Efforts continue to 

improve/debug software, refine the calibration of the instruments, and develop procedures to prevent bad 

instruments from contaminating the real-time display products.

A new site identification scheme was adopted for both NASA and ESMC field mills (34 sites in total)

1984

ESMC adds another 8 pen strip chart recorder to the CCFF, can now display 24 of 30 field mills

1985

The eight AFETR field mills were deactivated and replaced by NASA Phase I Field Mills at all CCAFS sites 

to form a network of 30 mills.

The original NASA instrument design was modified by replacing the multiple circuit cards in the second box 

with a single output card in the motor enclosure. Now analog data from each mill (including those on CCAFS) 

to the LCC where they were digitized and PCM coded in Room 2P19. In Room 2P20 they PMC data could be 

recorded on analog tape and sent to the NASA RDS 800 computer for processing and display. PCM data for 

all mills was also transmitted to the Central Computer Complex at CCAFS where the data was converted by 

the ARMS buffer into Cyber format for processing and display.

The instrument modifications were made by the ESMC (Pan Am) and documented in Range Engineering 

Drawings 403147 through 403153 but there was no record of a formal test since the LPLWS was not covered 

by ESMCR 80-4 (the Range configuration management policy at the time).
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1986

NASA (I think Phil Krider) observes high amplitude, high frequency noise on the field mill output during rain. 

Subsequent investigation finds the low pass filter in the original NASA design was not retained in the Range 

modification performed the prior year when the network was consolidated. All field mills were then modified 

to add a low pass filter in 1986 and 1987. These modifications are documented in ESMC engineering drawings 

404232 through 404237.

When I joined Pan Am, I was told to go to the junk yard where the electronics enclosures from the original 

NASA design were dumped, remove the low pass filters, and then solder them into each mill per the 

engineering drawings. I remember doing these modifications during the summer of 1986.

In December 1986 I leave Pan Am but before I leave I give them a report on the calibration interval of the 

LPLWS instruments. During the summer when I was assigned to the LPLWS cleaning crew I was astounded 

to find many instruments seriously out of calibration after only a week of exposure (after prior cleaning, which 

I performed). I started to record the before and after cleaning calibration data and plotted the change in 

calibration as a function of time for all of the instruments over a six month period. The data confirmed the 

Phase I field mills must be cleaned and checked weekly to maintain 10% accuracy, particularly those within a 

few kilometers of the coast. I also recommend all instruments be cleaned and checked on F-1 day and the 

before and after calibration data be recorded.

1987

On March 26 an Atlas Centaur is launched into precipitating, disturbed, debris clouds with high electric fields 

at ground measured by LPLWS and initiates a lightning flash which leads to the vehicle being destroyed.

1988

Electric Field Mill Training Handbook written by Launa Maier of NASA and Capt Tom Strange of Det 11 2 

WS is approved by Bob Sieck and John Madura and issued (January 1988). Still a great document!

LPLWS Requirements (NASA Document 79K32611) released by the joint NASA/ESMC LPLWS Task Team. 

The Phase I requirements were:

Add new field mill sites to provide coverage of all areas of interest

Conduct survey to verify location of all field mills

Replace the aging Tektronix monitor and strip chart recorders in the CCFF

Improve exposure of all field mills by clearing sites per the standard included in the requirement

Conduct an Operational Acceptance Test of the LPLWS to be overseen by a Detachment 11, 2nd Weather 

Squadron (Det 11 2 WS) observer

Establish configuration management and control of LPLWS. The configuration of the LPLWS was frozen for 

the OAT in December 1987 although three sites were not certified

Establish appropriate configuration identification for all aspects of the LPLWS

Begin a LPLWS replacement project (Phase II) where NASA would design and provide improved field mill 

sensors and ESMC would provide improved processing and display capability
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I recall the goal was to certify LPLWS Phase I as operational prior to the return to flight of Space Shuttle in 

October 1988. I think this was accomplished but I can’t find the official documentation or date, this was a 

NASA/Det 11 2 WS led effort.

1990

Concerned that the NASA/ESMC Task Team assumed the LPLWS calibration was accurate and development 

of the new instruments appeared to be dragging out, Launa and I flush mounted an LPLWS field mill next to 

the operational mill at Site 29 in September. We ensured the flush mounted mill was absolutely calibrated 

using two different plate spacing with a really large plate and collected simultaneous data over a wide range of 

fields. We found the operational LPLWS output was well correlated with the flush mount instrument but the 

operational instrument output (electric field) was systematically 40% too high. Test was repeated at another 

site (Site 11) and with other instruments and confirmed to be consistent. Error appears to be due to a change in 

the calibration plate spacing sometime between 1976 and 1990. The plate spacing in use in 1990 was 9.4 cm 

and probably should have been 10.0 cm. We reported the results to Det 11 2 WS and KSC personnel but there 

was no support to change the calibration procedure of the old instruments since the system had just been 

officially accepted and the expectation was the new Phase II instruments would be fielded shortly and these 

would be correctly calibrated by MSFC upon delivery.

1992

On 22 January the launch of STS 42 was delayed for one hour by high fair weather electric fields exceeding 

the +1000 V/m launch commit criteria. After the launch we reminded everyone the LPLWS calibration was 

40% too high and the true fields probably did not exceed the launch commit criteria. Lots of meetings and 

finger pointing, I remember being scolded by Det 11 2 WS for not doing a better job explaining to them the 

1990 findings about the calibration error and Jack Ernst for not following “proper procedures” for reporting 

the results.

Immediately following the STS 42 launch ESMC and KSC agreed to allow CSR to change the calibration 

procedure for the LPLWS based on the 1990 flush mount calibration data but Jan Zysko was still not 

convinced we knew what we were doing. Jan brought in Charlie Moore and Steve Hunyady from New Mexico 

Tech to conduct an independent verification of the LPLWS calibration using their reference mills. Their report 

to NASA on 30 May 1992 confirms our recalibration was indeed accurate and this calibration was retained 

until the Phase I instruments were decommissioned.

I consider it a major accomplishment that NASA and the USAF didn’t need to bring Charlie Moore back in 

2008 to perform yet another independent test of the field mill calibration, something that had previously been 

required every 16 years. I note with some sadness his passing last week; he was a person to be admired for 

many reasons.

1997

December – Operational acceptance of LPLWS Phase II and decommission of the Phase I instruments and 

processing systems.

2010

NASA/KSC and the 45th Space Wing are discussing ways of funding upgrades or replacements for the Eastern 

Range CGLSS, LDAR and LPLWS.
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Appendix VIIIWeather Instrumentation at KSC/CCAFS

As noted in Section 1.2, the Eastern Range benefits from an extensive suite of weather instrumentation 

including surface electric field mills, weather radar systems, surface meteorological towers, rain gauges, 

weather balloon systems, Doppler wind profiling radars and more. Each of these systems will be discussed 

separately here.

A8.1 Systems for Atmospheric Electricity: Electric Field Mills (LPLWS), CGLSS, LDAR and NLDN

The Eastern Range operates three major lightning-related instrumentation systems: electric field mills (called

the Launch Pad Lightning Warning System or LPLWS), the Cloud to Ground Lightning Surveillance System 

(CGLSS) and the Lightning Detection and Ranging (LDAR) system. CGLSS and LDAR are sometimes 

referred to in combination by the Range as the 4-Dimensional Lightning Surveillance System (4DLSS). In 

addition, the Range receives data from the commercial National Lightning Detection Network (NLDN). Each 

of these is described below.

A8.1.1 Electric Field Mills (LPLWS)

The LPLWS is basically a large-area network of electrostatic field sensors (field mills) that measures the 

vertical component of the electrostatic field, E, produced by cloud charges aloft, even if those clouds are not 

producing lightning. The sensors are termed ‘mills’ because they employ a rotating and grounded metallic 

shutter to alternately cover and uncover a set of insulated stators that respond to E. The amplitude and polarity 

of the current flowing to and from the stators is proportional to the amplitude and polarity of the local electric 

field. When an electrified cloud forms overhead or moves into the region from somewhere else, the E field will 

increase and often change polarity. In most cases, E will be large close to the cloud charges and small farther 

away, so 2-dimensional maps of E will show approximately where the cloud charges are located.

If the cloud electric field is measured in conjunction with a weather radar that senses precipitation, the onset of 

the electric field can be compared with the onset and type of precipitation, the rate of echo growth, and the 

time-evolution of the cells, thereby improving both the nowcasting (i.e. detection) and forecasting of high 

fields aloft. When lightning discharges occur, maps and analyses of the lightning-caused changes in E or ΔE 

can be used to determine an approximate location (in 3-dimensions) of the change in the cloud charge (Maier 

and Krider, 1986; Koshak and Krider, 1989; Krider, 1989).

The unique features of the LPLWS are its large area (approximately 20 x 30 square kilometers), the number of 

field mills (25 to 33), and the fact that each sensor is mounted (and calibrated) in the same way on uniform 

sites that are cleared of vegetation. A network like this minimizes the frequency of false alarms, such as might 

be caused by a single sensor having an incorrect reading, and also any ‘failures-to-warn’ that might occur if 

the positive and negative cloud charges are not vertically aligned or if the field seen by a single sensor is 

masked by intervening space charge. Further details on the implementation and calibration of the LPLWS at 

the KSC-ER are given in Appendix VII by Michael W. Maier.

Among the first scientific studies that were based on the field mill network were analyses of the electrostatic 

field changes produced by Florida lightning by Jacobson and Krider (1976) and the overall behavior of E 

under both small and large storms at KSC by Livingston and Krider (1978). These studies showed that the 

charge centers inside Florida storms are located at altitudes where the air temperatures are below freezing, i.e. 

where the environmental temperatures are between about -10 oC and -20 oC, and that the time-average values 

of E are often surprisingly small when averaged over five minute intervals, even under active storms. The 

finding that the lightning charges are located at subfreezing temperatures lent support to the idea that a noninductive ice-ice collision process is the dominant microphysical mechanism in cloud electrification 

(Saunders, 1988; 2008), and the LLCC still rely on this assumption.
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Figure A8.1.1-1 The KSC/CCAFS Launch Pad Lightning Warning System (LPLWS)

Note: Each surface field mill is depicted as a green square. Figure courtesy of William Roeder, 45WS.

A8.1.2 Cloud To Ground Lightning Surveillance System (CGLSS)

KSC has made major contributions to the development of two complementary systems for detecting and 

locating lightning, the Cloud-to-Ground Lightning Surveillance System (or CGLSS) and the Lightning 

Detection and Ranging (or LDAR) system. The CGLSS utilizes a network of gated, broadband electric and 

magnetic field sensors (Krider and Noggle, 1975) to detect the waveform signatures that are characteristic of 

return strokes, the high-current components of CG flashes (Krider et al, 1976; Herrman et al., 1976). When a 

proper signature is detected (in the time-domain) at two or more known locations (the antenna sites), the 

coincident times-of-arrival and magnetic directions can be used to compute the points where return strokes 

strike the ground (Krider et al., 1980; Cummins et al., 1998; 2006).
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Figure A8.1.1-2 An electric field mill

According to a time-domain antenna theory developed by M. A. Uman and his collaborators shortly after the 

Apollo 12 incident (see for example Uman et al., 1975), the initial peak of the electromagnetic pulse that is 

radiated by a return stroke is proportional the peak current in the stroke, multiplied by the speed of the stroke 

up the leader channel, and divided by the distance to the stroke. [Note: this theory is sometimes called the

simple ‘Transmission-Line Model’ or TLM because it assumes the current pulse propagates up a straight 

channel, without distortion, and at a constant speed.] Since the CGLSS measures the peak field and can 

compute the stroke location, and since the stroke velocities are known and roughly constant, the CGLSS can 

also provide an estimate of the peak current in the stroke and its polarity.

The first CGLSS system was installed at the KSC-ER between 1 June 1979 and 12 July 1979. It was a 

prototype consisting of three medium-gain magnetic direction-finders (DFs) and was installed as part of the 

Federal Evaluation of Lightning Tracking Systems (FELTS). This system was subsequently purchased in 

February 1981 with joint funding provided by NASA and the Air Force. In August 1983, a low-gain system 

was added to obtain more accurate locations near the KSC-ER launch complexes. By February 1984, the 

system contained two low-gain direction-finders (DFs) that were located at the Ti-Co Airport (28.5N 80.8W) 

and on Merritt Island (28.4N 81.3W), and three medium-gain sensors, one co-located with the low-gain sensor 

on Merritt Island, and the other two were at the Orlando and Melbourne Airports (Harms, et al., 2001). After 

1984, the system continued to be developed and evaluated and was eventually accepted into the ER inventory 

as a fully certified system on 24 July 1989. Between 1989 and 1994, the CGLSS was upgraded to a network of 

five LLP Model 141 Advanced Lightning Direction Finders (ALDFs), and during 1995-1998, the system was 

converted to a 6-station, short-baseline network of medium-gain IMPACT (IMproved Accuracy from 

Combined Technology) sensors (Cummins et al., 1998).
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The present CGLSS system has an effective range of about 100 km and covers the KSC-ER launch and 

operations areas with good accuracy and high detection efficiency (Ward et al, 2008). The CGLSS is operated 

24 hours a day, 7 days a week by the Range Technical Services (RTS) Contractor, and the data are sent in realtime to the 45 WS for use in operations.

Figure A8.1.2-1 4DLSS sensor locations

Note: L denotes LDAR II sensors. C denotes CGLSS sensors. Figure courtesy of William Roeder, 45WS.

A8.1.3 Lightning Detection and Ranging (LDAR)

The first LDAR system was developed at KSC by Carl Lennon and associates after a design described by 

Proctor (1971). It contained seven broadband VHF radio receivers that were deployed at the sites shown in 

Figure A8.1.3-1and were precisely time-synchronized, initially using microwave communications links and 

later GPS timing.
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Figure A8.1.3-1 Locations of the original KSC LDAR sensors

Note: Figure courtesy of Jennifer Wilson.

Each site received VHF radiation at 66 MHz, logarithmically amplified the signal, and then transmitted the 

time and key signal parameters to a central station where the source locations were computed (Lennon and 

Maier, 1991; Maier et al., 1995). The 3-D locations of the sources of lightning VHF pulses are computed using 

the differences in the times-of-arrival of the signals detected at the different receiver sites. Since the main 

sources of VHF radio emissions are the processes associated with air breakdown, the LDAR system detects 

primarily the in-cloud portions of CG flashes, leader processes, and intracloud discharges. Today each LDAR 

receiver site operates automatically and is powered by batteries that are recharged by solar panels. The first 

LDAR system was developed by the KSC Instrumentation and Measurements Branch and was operated and 

maintained by a NASA contractor. The current system, which is owned and operated by the Eastern Range, is 

a commercial version of LDAR called LDAR II marketed by Vaisala, Inc. The commercialization was done 

under a Space Act Agreement between NASA/KSC and a company called Global Atmospherics, Inc. which 

was subsequently acquired by Vaisala. The 45 WS receives and evaluates the LDAR data 24 hours a day, 7 

days a week. For further details on the evolution of the LDAR system and other instrumentation at the KSCER, see Boyd et al. (1995), Harms, et al.(1997; 1998; 2001) and Roeder et al.(1999).

A8.1.4 U.S. National Lightning Detection Network (NLDN)

Data from the U.S. National Lightning Detection Network (NLDN) (Cummins et al., 1998, 2006; Cummins 

and Murphy, 2009) have been used to detect and track CG lightning flashes beyond 100 km since the early 

1990s. The NLDN sensors are similar to those in the CGLSS except that they have higher gains and larger 

distances between the sensors. The coincident data from two or more sensors are collected and processed in 

real-time by a network control center in Tucson, Arizona, and the GPS time, location, and polarity of each 

lightning stroke, together with an estimate of its peak current, are provided to the KSC-ER in real-time. For 

further information about the NLDN and its history, see Cummins and Murphy (2009).
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A8.2 Weather Radar

The operational weather radar for the Eastern Range as of December 2009 is the WSR-74C, a 5 cm 

conventional weather radar based on pre-Shuttle technology. WSR-74C radar products are generated using 

proprietary IRIS software provided by SIGMET, Inc. It can produce constant altitude (CAPPI) displays, 

composite and max reflectivity, radar cross sections and other products at the direction of the user. (Eastern 

Range Instrumentation Handbook, 2005).

The WSR-74C has become expensive and difficult to maintain because of its age. As this is being written, a 

modern replacement is undergoing its final acceptance testing. The replacement is a Radtec model TDR-43-

250 5 cm radar located in Orange County, Florida about 25 mi southwest of the launch complexes. The new 

location provides a substantially improved viewing angle over the operational area. The new radar has both 

Doppler and dual-polarization capability, neither of which was available on the previous Eastern Range 

weather radars.

In addition to the radar owned by the Range, the National Weather Service NEXRAD 10 cm Doppler radar at 

Melbourne, Florida (KMLB) is used operationally by the 45th WS. There is a dedicated NEXRAD terminal in 

Range Weather Operations. It is expected that this radar will be upgraded to include dual-polarization 

capability in 2011.

A8.3 Surface Systems

Surface systems include a variety of sensors and observations, most of which are of the kind that appear in 

standard weather reports. These include measurements of wind direction and speed, temperature, barometric 

pressure, relative humidity, visibility and rainfall. These measurements are made by human observers and 

automated systems as described below.

A8.3.1 Meteorological Towers

The current Eastern Range tower network has 46 towers including one 150m and three 62m towers. They 

cover an area of about 122 km2 for an average station density of one tower every 27 km2

. Figure A8.3.1-1 

shows the current tower locations on the Eastern Range. The identification numbers are based on location. The 

first two digits of the 4 digit ID (including a leading zero when necessary) correspond to the distance in 

nautical miles west of the coastline. The last two digits are the distance (n. mi.) north of Port Canaveral. 

Towers south of the Port have a leading digit of 9.
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Figure A8.3.1-1 Location of surface meteorological towers operated by the Eastern Range

Note: Towers 511, 512 and 513 in the grey polygon (center, right side of the figure) are located respectively at 

the south, center and north of the Shuttle Landing Facility. In this figure, several towers are associated with 

launch complexes (LC) of the same number as follows: 17 (Delta II, SE shore of the Cape), 36 (Atlas, just 

north of the tip of the Cape), 40 and 41 (formerly Titan, now Atlas V and Falcon, north of #36) . LC 37 (Delta 

IV) is not shown but is between LC 36 and LC 40. Tower 398 on this map is located near LC39, the Shuttle 

launch complex.

Wind speed and direction are measured with propeller vane anemometers with an accuracy of about 0.3 m/s 

and 3 oC respectively. Air temperature is measured with platinum RTD sensors and RH with capacitance-type 

humidity sensors. Towers designated “launch critical” or “safety critical” are mechanically aspirated. The 

remaining towers are naturally aspirated. Temperature accuracy is better than 0.5 °C RMS and RH accuracy is 

better than 3% RMS (Eastern Range Instrumentation Handbook, 2005). Measurements are collected at one 

second intervals and reported at five minute intervals. For each five minute interval the average wind speed 

and (vector average) wind direction as well as the one second peak wind speed and direction of that peak are 

reported. The temperature and RH values are 5 minute averages.

A8.3.2. Manual Observations

Surface weather observations at the Eastern Range are made by personnel of the Range Technical Services 

Contractor for use by the 45th Weather Squadron, Range customers and the Air Force Weather Agency located 

at Offutt AFB, Nebraska. The information in this subsection is taken from the Eastern Range Instrumentation 

Handbook, July 2005 revision.

The official observing site, designated station KTTS, is located at KSC in room 4024 of the Air Traffic 

Control Tower at the Shuttle Landing Facility. Observers submit routine aviation weather reports (METAR) as 

well as non-routine aviation reports (SPEC/LOCAL) on a round-the-clock basis with additional special 

observations for Shuttle launch and landing operations. The routine observations include the following:

• Wind speed and direction (reported by three 10m towers along the SLF)
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• Maximum wind speed and wind direction variability

• Ambient air temperature and dewpoint (reported by the center SLF wind tower)

• Station pressure (as altimeter setting from an on-site ML-658/GM digital barometer)

• Observed weather (e.g., thunder, precipitation type, visibility) and sky conditions (cloud type, height 

and coverage) (based on personal observations and readings from three CT-12K laser ceilometers)

• Remarks providing any additional information for clarity or safety.

The observations are reported in accordance with Air Force Manual 15-111, Surface Weather Observations

and supplemented by the Federal Meteorological Handbook (FMH-1). Visibility, cloud cover, weather events, 

and obstructions to visibility are all based on the observer’s skill and judgment at making these observations, 

and are not provided by sensors. However, for visibility, they use known landmarks (e.g., launch towers, 

Vehicle Assembly Building [VAB], water towers) with known distances from the Weather Station (Eastern 

Range Instrumentation Handbook, 2006).

A8.3.3 Ceiling, Visibility and Soil Moisture

The Eastern Range deploys three CT-12K Laser Ceilometers. One is located near the center of the Shuttle 

Landing Facility (SLF), another is located in the KSC industrial area near the Environmental Health Center, 

and the third is located north of the SLF at Field Mill site 2.

NASA deploys five soil moisture and visibility sensors to the west of KSC to support Shuttle landings. The 

concern is that post-dawn landings could be subject to a “sunrise surprise” in which undetected ground fog in 

the St. Johns river basin in Orange County could advect over the SLF reducing visibility at landing below 

acceptable levels. If the de-orbit decision is made before dawn, there is no ground or satellite-based remote 

sensing technique that can reliably detect ground fog, so in-situ sensors must be deployed.

A8.3.4 Rainfall

At each of the 31 field mill sites described in section 1.2.6 above, a tipping bucket rain gauge is installed. 

These gauges were funded by the Tropical Rainfall Measuring Mission (TRMM) to provide ground truth for 

the TRMM satellite launched 27 November 1997. The data are available on the KSC weather data archive 

website <http://trmm.ksc.nasa.gov/>. Tipping bucket counts, each indicating 0.01 inches (.254 mm) of 

precipitation, are recorded once per second but only hourly totals are archived.

A8.3.5 Offshore Data Buoys

NASA funds the deployment and operation of two buoys by the National Data Buoy Center. One of these is 

located 20 nautical miles east of Cape Canaveral and the other is located 120 nautical miles east of Ponce De 

Leon Inlet in Florida. These buoys provide the only available measurements of off-shore conditions affecting 

the safety of operations by the Shuttle booster recovery ships, and the only upstream surface data available to 

45WS forecasters during easterly flow conditions. The buoys report hourly observations via satellite of the 

following:

• Wind speed and direction

• Barometric pressure

• Air and water temperatures

• Rainfall

• Wave height and period

(Source: NASAfacts, Space Shuttle Weather Launch Commit Criteria and KSC End of Mission Weather 

Landing Criteria, FS-2006-06-020-KSC, Rev. Nov. 2006)
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A8.4 Upper Air Systems

Upper air measurements have been made using weather balloons for more than a century. Within the last 

several decades, wind profiling radars have come into common operational use. The Eastern Range and KSC 

benefit from both kinds of upper air sensors.

A8.4.1 Balloons

The Eastern and Western Ranges use a weather balloon system called the Automated Meteorological Profiling 

System (AMPS). AMPS balloons come in two types: low resolution (lo-res) and high resolution (hi-res). Wind 

measurements from balloons assume the balloon follows the wind and derives the horizontal wind vector from 

the time derivative of the balloon’s horizontal position. Thermodynamic measurements are made in-situ using 

sensors carried by the balloon.

The lo-res AMPS uses a standard latex weather balloon with a GPS-tracked expendable sonde or “flight 

element” that contains sensors for temperature (thermistor) and relative humidity (carbon film hygristor). 

Altitude is directly measured from the GPS data and pressure is calculated from the hydrostatic equation using 

the altitude and thermodynamic data for the trajectory of the sonde as it rises. The balloon rise rate is about 

1000 ft/min (5.5 m/s) and the maximum altitude usually exceeds 100 kft (33 km). The wind measurement 

accuracy is about 1 m/s RMS with a vertical resolution of about 350m. The air temperature and RH RMS

accuracies are respectively 0.2 °C and 5%. The barometric pressure accuracy is about 0.5 hPa (mb).

Data are downlinked from the sonde on one of 16 channels near a frequency of 403 MHz GPS and 

meteorological data are transmitted separately. At the ground, the received signals are processed in an AMPS 

signal processing system and the results are provided to an Upper Air Systems Controller who can perform 

manual quality control before the data are released to MIDDS (see description in section A8.5.1 below) for 

dissemination to the users.

The hi-res AMPS uses a special balloon which is identical to radar tracked “Jimsphere” balloons except that 

they are clear because they do not have the aluminized coating used for radar tacking. The balloon is 2m in 

diameter with surface roughness elements that control boundary layer separation to reduce self-induced 

balloon motions. It rises at about 1000 ft/minute to a maximum altitude of between 55 and 60 kft (17 – 18 km). 

The flight element for these sondes is smaller and lighter because it does not carry thermodynamic sensors. 

The wind measurement accuracy and vertical resolution of the AMPS hi-res balloons is about the same as that 

of Jimspheres (a radar-tracked predecessor to the hi-res AMPS), less than 1 m/s RMS and 150m respectively 

(Eastern Range Handbook, rev July 2005; Wilfong et al., 1997). Data transmission and processing uses the 

same system as the AMPS lo-res packages.

A8.4.2 Doppler Radar Wind Profilers

The Eastern Range and Western Ranges operate networks of 915 MHz boundary layer profilers and the 

Kennedy Space Center operates a 50 MHz tropospheric wind profiler. Their locations are shown in Figure 

A8.4.2-1. These systems have much in common, and these common elements will be described first. The 

system-specifics for each type follows. Data from all of these profilers is fed into MIDDS (see section A8.5.1

below) for dissemination to the users.
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Figure A8.4.2-1 Locations of the Eastern Range and KSC wind profilers

Note: The Shuttle Landing Facility (SLF) and various space launch complexes (SLC) are also shown. The 

KSC 50 MHz profiler is the (blue) one immediately adjacent to the north end of the SLF. The remaining five 

profilers (yellow) constitute the ER 915 MHZ network. (Figure courtesy of William Roeder, 45WS).

The Doppler radar wind profilers (DRWP) transmit radio pulses sequentially along three beam directions. One 

beam, called the vertical beam, is directed straight upward. The remaining two beams, called oblique beams, 

are directed 15 degrees off of the vertical at 90 degrees with respect to each other in the horizontal. The pulses 

are backscattered from fluctuations in the radio index of refraction in the atmosphere and received by the radar 

as a function of time after transmission. From the round trip time between transmission and reception, the 

range to the scattering volume can be readily calculated. The signals are integrated over range bins (or gates) 

on the order of 300 ns duration or about 100m length in the atmosphere. The scattered signal is Doppler shifted 
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by an amount proportional to the component of the wind velocity parallel to the beam direction. Both the inphase and quadrature components of the reflected signal are measured from which the beam-aligned wind 

component can be calculated. The full wind vector is then calculated from the measured components along the 

three non-co-planer radar beam directions. The scattered signal comes primarily from atmospheric fluctuations 

with scales near half of the wavelength of the transmitted radar signal.

The KSC tropospheric profiler is designed to support launch operations and must provide reliable 

measurements to a height of 18 km. In order to reach this altitude dependably it must operate at a wavelength 

long enough for there to be significant atmospheric turbulence at that scale in the upper troposphere and have a 

very large power-aperture product. The KSC profiler operates at 49.75 MHz (6 meter wavelength) with a peak 

power of 250 kW and a physical aperture of 15,000 square meters. The range gates are 150m providing 

continuous coverage from 2 to 18 km altitude above ground level. The RMS accuracy is about the same as the 

best wind-finding balloons (Jimspheres), 1 m/s, and its effective vertical resolution is Nyquist limited at 300m 

(Schumann et al., 1999; Merceret, 1999).

Normally the KSC profiler operates unattended 24/7/365. For day of launch applications, additional manual 

quality control is provided by the Eastern Range Technical Services Contractor. This QC process involves 

examining the Doppler spectra in each beam and, if necessary, adjusting certain variable parameters of the 

Median Filter First Guess signal processing algorithm (Schumann et al., 1999).

The Ranges profiler networks are used primarily to support Range Safety requirements to identify potential 

toxic and blast hazards in the event of a processing or launch accident. Wind data are needed at multiple 

locations in the boundary layer, but not to altitudes in the upper troposphere. Boundary layer turbulence 

contains significant energy at smaller scales which permits operating the radars at smaller wavelengths. The 

ER and WR profilers operate at 915 MHz (33 cm wavelength). They are standard commercial instruments 

(Vaisala model LAP-3000). Range gates of 100m are used to cover the altitude range from about 100m to 5 

km. Wind measurement accuracy is thought to be on the order of 1 m/s RMS (Eastern Range Handbook, Rev 

January 2006; Lambert et al., 2003).

The boundary layer profilers have an additional capability called Radio-Acoustic Sounding System (RASS). 

The RASS transmits acoustic pulses upward and tracks them with the radar. Since the speed of sound depends 

only on the virtual temperature, the upward velocity of the sound pulse can be converted to a vertical profile of 

vertical temperature. In the author’s [FJM] experience, this capability has proved neither reliable nor useful.

A8.4.3 Weather Reconnaissance Aircraft

Weather reconnaissance aircraft (Wx Recon) are deployed for Space Shuttle launches and landings and for 

launches of expendable launch vehicles to assist the weather support team in evaluating operational weather 

constraints. These aircraft can more precisely determine the exact location, height and thickness of clouds than 

can radar, and can also determine whether the clouds are optically transparent, and the presence and type of 

precipitation. All of these cloud properties are important for determining whether launch commit criteria or 

landing flight rules are violated.

For the unmanned vehicles, the Eastern Range currently relies on aircraft operated by commercial contractors. 

Only pilot or trained observer reports are provided. There is no on-board instrumentation beyond the aircraft 

navigation system (Eastern Range Instrumentation Handbook, 2004). The aircraft is typically a business jet in 

the LearJet 35 class with the capability to remain on station for up to 5 hours operating out of small local 

commercial airports (ibid). Pilots and observers receive annual training on the lightning LCC from the 45th

Weather Squadron.

Wx Recon support to the Space Shuttle Program is provided by a NASA T-38 jet trainer and the Shuttle 

Training Aircraft, both flown by astronauts to observe actual conditions for evaluation by the Shuttle Weather 
Page 216 of 234

Officer at the launch site and the Spaceflight Meteorology Group (SMG) at Johnson Space Center. The Shuttle 

Weather Officer (not to be confused with the Shuttle Launch Weather Officer provided by the 45WS) is a 

weather support astronaut located in the firing room at KSC with the Mission Management Team. (Source: 

NASA Facts “Space Shuttle Weather Launch Commit Criteria and KSC End of Mission Weather landing 

Criteria”). Like the contract aircraft used for the unmanned operations, the Shuttle Wx Recon aircraft do not 

carry meteorological instrumentation.

A8.5 Additional Observation and Forecast Assets

A8.5.1 Data Integration and Display Systems

The Eastern Range collects and displays much of its meteorological data on the Meteorological Interactive 

Data Display System (MIDDS). Additional MIDDS users include the Applied Meteorology Unit (AMU, see 

section 5.2.3) co-located with Range Weather Operations, the National Weather Service Office at Melbourne, 

the Spaceflight Meteorology Group (SMG) at Johnson Space Center in Houston, the Natural Environments 

Branch at Marshall Spaceflight Center in Huntsville, and the KSC weather data archive 

<http://trmm.ksc.nasa.gov/> which obtains much of its data from the Range through exchange of MIDDS 

files.

Local data acquired by MIDDS includes the surface tower data and upper air data described in previous 

sections as well as some local radar imagery. Other data includes satellite images and output from national 

models. MIDDS provides the ability to overlay images and to generate products automatically through a 

scripting language called McBasi. The 45th Weather Squadron uses a variety of custom scripts, many 

developed by the AMU.

A8.5.2 Forecast Tools and Indices

At the Eastern Range the information provided by instrumentation and models is augmented by a variety of 

software tools. Many of these tools were developed by the Applied Meteorology Unit (AMU) co-located with 

the 45thWS at Range Weather Operations. The AMU is a joint NASA/Air Force/National Weather Service 

undertaking to develop, evaluate and transition weather technology to operations in support of America’s 

space program. More information about the AMU may be found in Sections 1.3 and 5.2.3 above and at 

<http://science.ksc.nasa.gov/amu/>.

The following list of operational tools is neither detailed nor complete. The tools used are rapidly changing 

through updates and new developments. This list is designed to show the general types of tools in routine use 

either for daily support to ground operations or for specialized support to launches or landings. Where 

applicable reports are publically available, they are cited.

1. Severe weather tools

Several severe weather tools are available on the MIDDS system (see section A8.5.1 above) for the forecasting 

of severe weather in general (Bauman et al, 2005), microbursts (Wheeler, 1996), and fair weather waterspouts.

2. Peak wind tools

Separate tools are available to assist in the forecast of peak winds by daily forecasters (Barrett and Short, 

2008) and Launch Weather Officers (Lambert, 2002).

3. Lightning forecast tools

A probability of lightning tool (Lambert, 2007; Lambert and Wheeler, 2005) assists in the issuance of daily 

lightning forecasts
Page 217 of 234

4. Daily forecast tools

Tools are available for forecasting routine daily weather phenomena such as low-level convergence (Bauman, 

2006) and fog (Wheeler, 1994)

5. Tools relating to launch constraints

Tools targeted at specialized day of launch requirements or constraints include an anvil forecast tool for 

assessing the likelihood of violating the anvil rules of the LLCC (Lambert, 2000), a Shuttle Low Temperature 

Launch Constraint recovery tool, and a Shuttle launch imaging tool that assesses the likelihood that the 

required three independent views of the flight path will be obscured by cloud cover (Short and Lane, 2005).

6. Tools relating to the effective application of specific systems

Specialized scan strategies are used with the WSR-74C radar system (see ITEM II above) to maximize the 

ability of the Launch weather team to observe parts of the atmosphere critical to spaceflight operations (Short, 

2008; Taylor, 1994). A unique Median Filter First-Guess signal processing package is used on the KSC 50 

MHz Doppler radar wind profiler (see Section A8.4.2. above). A set of specialized menus simplifies the use of 

the MIDDS system.

A8.6 Numerical Weather Prediction (computer models)

Although a locally run numerical weather prediction model is not used operationally by the 45th Weather 

Squadron, Eastern Range Safety operates an Eastern Range Dispersion Assessment System (ERDAS) which 

contains a version of the Regional Atmospheric Modeling System (RAMS) to generate wind fields for 

predictive dispersion modeling. This is used to assess toxic and blast hazards. Some details of the model and 

its use as well as an evaluation of its performance may be found in Case (2001). On the other hand, the 

National Weather Service Office at nearby Melbourne, Florida uses high resolution numerical weather 

prediction extensively. The material in this subsection was provided by David Sharp, the Science and 

Operations Officer at the NWS Office in Melbourne. His assistance is deeply appreciated. The National 

Weather Service Forecast Office in Melbourne (MLB), FL, has been involved in both individual and 

collaborative numerical weather prediction endeavors since the late 1990s (Case, 1999). Specific emphasis has 

been placed upon the assimilation of unique observational data sets (Lazarus et al., 2006; Zavodsky et al., 

2004;) and the generation of both high-resolution automated analyses (Blottman et al., 2001 ) and model 

forecasts (e.g., Watson et al., 2007) over the Florida Peninsula and adjacent coastal waters. The commitment 

has been to improve warnings and forecasts for East Central Florida for short-term (00-24 hour) operations 

(Sharp et al., 2002).

Guided by mutual operational priorities, several initiatives have resulted in community-wide benefits. The 

most notable initiative involves the provision of real-time 3-dimensional diagnostics delivered to forecasters 

every 15 minutes at 4 km resolution. Rapid-refresh analyses of countless environmental parameters are made 

available through an optimized Advanced Regional Prediction System (ARPS) Data Assimilation System (Xue 

et al., 2003). This diagnostic system (Case et al., 2002) assimilates observational data from surface observing 

systems and area mesonets, from wind profilers and tower networks at the Kennedy Space Center, from 

environmental satellites and weather radar, and more, to foster a detailed monitoring of the evolving local 

atmosphere. It has been successfully used to track the advance of freezing (0 oC) and hard freezing 

temperatures (-2 oC) for area growers, to monitor the evolution of buoyancy and shear in both pre-storm and 

near-storm environments associated with severe and tornadic convection, to identify favorable areas of lowlevel wind shear for take-off/landing aviation traffic, to assess the length and movement of wind shift lines and 

sea breezes for incident commanders, to detail areas of long duration relative humidity below 35 percent for 

(wild) fire fighters, etc. Output is available on forecaster AWIPS/D2D (Advanced Weather Interactive 

Processing System/Display 2-Dimensions) workstations for visualization and further use within gridded shortterm forecasts as persistence grids and forecast validation grids. Output is also made available on MLB web 
Page 218 of 234

pages <http://www.srh.noaa.gov/mlb/ARPS.html> for partners to use. These partners include State and 

County Emergency Management and the United States Air Force’s 45th Weather Squadron.
Page 219 of 234

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