Defense Science Board 

Task Force 

on 

The Future of the Global 

Positioning System 

October 2005 

Office of the Under Secretary of Defense 

For Acquisition, Technology, and Logistics 

Washington, D.C. 20301-3140 
Report Documentation Page Form Approved

OMB No. 0704-0188

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and

maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information,

including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington

VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it

does not display a currently valid OMB control number.

1. REPORT DATE

OCT 2005

2. REPORT TYPE

N/A

3. DATES COVERED

 - 

4. TITLE AND SUBTITLE

Defense Science Board Task Force on: The Future of the Global

Positioning System

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) 5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Office of the Secretary of Defense Acquisition and Technology and

Logistics Washington, DC 20301-3140

8. PERFORMING ORGANIZATION

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

11. SPONSOR/MONITOR’S REPORT 

NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release, distribution unlimited

13. SUPPLEMENTARY NOTES

The original document contains color images.

14. ABSTRACT

15. SUBJECT TERMS

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

ABSTRACT

SAR

18. NUMBER

OF PAGES

109

19a. NAME OF

RESPONSIBLE PERSON

a. REPORT

unclassified

b. ABSTRACT

unclassified

c. THIS PAGE

unclassified

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std Z39-18 
 

 

This report is a product of the Defense Science Board (DSB). 

The DSB is a Federal Advisory Committee established to provide independent 

advice to the Secretary of Defense. Statements, opinions, conclusions and 

recommendations in this report do not necessarily represent the official position of 

the Department of Defense. 

This report is unclassified.

This page intentionally left blank. 




 

___________________________________________________________ TABLE OF CONTENTS

_______________________________________________________________________ 

 

i

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...............................................................................................3

Task Force Background and Approach .............................................3

GPS Background and Current Issues.................................................4

Task Force Recommendations ..........................................................13

System and Program Recommendations ........................................14

CHAPTER 1. INTRODUCTION ...................................................................................25

1.1 Task Force Approach...................................................................25

1.2 GPS Description............................................................................25

1.3 Introduction of the Issues............................................................29

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS AND THE NATIONAL 

INFRASTRUCTURE.....................................................................................................33

2.1 National Security Infrastructure (Domains and 

Missions)........................................................................................33

2.2 National Economic Infrastructure .............................................38

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ..........................................................43

3.1 Lack of Balance among the GPS Segments...............................43

3.2 GPS Satellites & the GPS Constellation.....................................44

3.3 System Operations, Signal Monitoring and 

Performance Assessment ............................................................48

3.4 User Equipment & Improvements in Anti-Jam 

Performance ..................................................................................54

3.5 Security Policy – Protection & Exclusivity................................63

CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT67

4.1 GPS and the Global Marketplace ...............................................67

4.2 Advent of European Union’s Galileo ........................................68

4.3 National Governance of GPS and the PNT 

Infrastructure ................................................................................70

4.4 Execution of GPS Management Responsibilities in the 

DoD ................................................................................................71

CHAPTER 5. RECOMMENDATIONS ..........................................................................73

5.1 GPS User Priorities .......................................................................73

5.2 System and Program Recommendations ..................................74

APPENDIX A. TERMS OF REFERENCE ...................................................................83

APPENDIX B. TASK FORCE MEMBERSHIP ............................................................85
 

TABLE OF CONTENTS____________________________________________________________ 

________________________________________________________________________ 

 

ii 

APPENDIX C. BRIEFINGS RECEIVED BY THE TASK FORCE...................................87

APPENDIX D. GPS CONSIDERATIONS FOR SMALL DIAMETER BOMB (SDB) AND 

THE F-22....................................................................................................................89

APPENDIX E. SPATIAL INTEROPERABILITY ..........................................................91

Military Spatial Interoperability ...................................................... 91

Civil/Homeland Security Spatial Operations ............................... 92

APPENDIX F. USER EQUIPMENT UPGRADE COSTS (“SILVER BULLET”

CAPABILITY) .............................................................................................................95

APPENDIX G. ACRONYMS........................................................................................97
EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 3

EXECUTIVE SUMMARY

TASK FORCE BACKGROUND AND APPROACH

On April 9, 2004, the acting USD (AT&L) and the ASD (NII) jointly 

requested that the Defense Science Board undertake a Task Force on the 

future of the Global Positioning System (GPS). The request focused on 

the implications for GPS from a civil-commercial Galileo, the European 

Union’s proposed Global Navigation Satellite System (GNSS). The 

Terms of Reference also requested assessment of several other aspects of 

GPS military and commercial competitiveness and of upgrade strategies 

and technical alternatives. 

The DSB empanelled a Task Force comprised of GPS experts with 

extensive public and private sector experience. Deliberations on 

relevant GPS topics were conducted primarily among the Task Force 

members with outside briefings limited to current activities affecting the 

program itself and other directly relevant topics. 

During the course of the year several outside events significantly 

modified the issues of uncertainty that had existed when the Task Force 

was formed. Those events included the signing of a cooperative 

agreement on GPS and Galileo between the United States and the 

European Union in June 2004, a major study on GPS commercial 

viability as approved by the Deputy Secretary of Defense in October 

2004 and signature by the President of an updated national policy on 

GPS and related systems in December 2004. While each of these events 

moderated specific areas of uncertainty that had been complicating GPS 

planning, each is still a work in progress that will require monitoring as 

leadership moves to address the still substantive issues facing GPS 

operation and evolution. 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 4

GPS BACKGROUND AND CURRENT ISSUES

Background 

The GPS is a space-based positioning, navigation and timing (PNT) 

system developed by the DoD and currently managed by the U.S. 

government through an interagency process that seeks to fuse civilian 

and military interests. That process was the subject of the recently 

signed Presidential Directive. The U.S. Air Force finances and operates 

the system of 24+ GPS satellites (distributed in six orbital planes) and a 

control segment with associated ground monitoring stations located 

around the world. GPS signals permit simultaneous determination of 

both precise three-dimensional position and precise time. GPS was the 

first and remains the only global, three-dimensional radio navigation 

and timing system providing continuous operational service today. Its 

civil signal represents a commodity service, provided as a public good 

by the U.S. government (for safe navigation, improved quality of life and 

diverse economical purposes) and freely available to all without direct 

cost or other encumbrance. Its military signals are encrypted for 

exclusivity of access by U.S. and allied military forces. 

GPS Pervades National Security and Economic Infrastructures – 

GPS is vital to the United States and to the DoD because, as a 

fundamental information system, it provides a common thread of 

precise position and time throughout our national security and 

economic infrastructures. This global, seamless service is invaluable for 

safe and efficient movement, measurement, and tracking of people, 

vehicles, and other objects anywhere from the earth’s surface to 

geosynchronous orbit, as well as providing timing and synchronization 

for global communications, electronic transactions of all types, and 

power-distribution networks. GPS is used by national mapping 

agencies worldwide as a basic component of geographic information 

systems and for natural hazards mitigation (earthquakes, volcanoes, sealevel rise), climate monitoring, severe storm predictions, and in 

characterizing space weather (ionosphere). Scientific applications 

involving GPS on-board Low Earth orbiters are revolutionizing weather 

forecasting and gravity field determination from space. 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 5

GPS Quietly Underpins Quality of Life and Economic/Military 

Performance -- GPS represents a quintessential enabling technology – 

but one whose contributions are not always apparent, recognized or 

widely publicized. GPS services directly enable improved mobility, 

warfighting and communications and indirectly enable many other 

national infrastructure components to function more efficiently, safely 

and economically than they could in the absence of GPS. These 

infrastructure components interact to create quality of life for our 

citizens, enhance safety of life in our enterprises and produce efficiencies 

that sustain and enhance our economic performance and provide a 

critical advantage in military actions. Through its contributions, GPS 

has not only created its own service infrastructure that must be 

maintained at a high level of robustness and availability, it has also 

become an indispensable component of many other infrastructures on 

which our nation depends. These include telecommunications, electrical 

power distribution, banking and finance, transportation, emergency 

services, and military operations and involve hundreds of applications 

whose discrete contributions are virtually impossible to quantify. 

GPS Brings Safety & Precision to Military Operations – Militarily, 

GPS provides a constant worldwide source for highly precise position 

and time, both of which are critical for the safe and efficient conduct of 

military operations and for a transformation to net-centric operations. 

GPS enhances interoperability in all aspects of military combat 

operations because of its common-datum, common-grid, and commontime capabilities. GPS has also been the catalyst for precision operations 

by increasing individual weapon effectiveness and minimizing collateral 

damage, a combination relevant to the new Air Force initiative of the 

Small Diameter Bomb. This new concept requires extremely precise 

target location and weapon delivery and, consequently, is particularly 

demanding of accuracy and availability from GPS. 

GPS Becoming a Global Standard – Internationally, GPS provides 

significant benefits for civil and scientific users. GPS enables global georeferencing – tying all points to a common grid. Also, GPS observations 

dominate contributions to realizing the International Terrestrial 

Reference Frame (ITRF) - which even Galileo will adhere to. 

Sustaining GPS Contributions Requires Prompt Leadership 

Attention -- From all outward appearances, GPS seems to be a healthy, 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 6

successful program. At its current level of performance, GPS is 

providing, on average, better than 5-meter horizontal accuracy, better 

than 10-meter vertical accuracy and absolute time within 0.1 

microsecond of Universal Coordinated Time (UTC). With differential 

GPS techniques, local accuracies of 1-meter and better are routine. 

However, our investigation into various aspects of GPS operation and 

management reveals serious issues that affect its operational viability 

and require prompt leadership action to correct. These include issues of 

military effectiveness, civil performance and competitiveness, and 

governance. 

A Vision for GPS 

GPS has been implemented and operated to this point without 

benefit of a commonly accepted vision of its potential contributions. 

Even so, it has produced dramatic improvements both globally and for 

our nation that exceeded the expectations of its creators. Those 

achievements have occurred largely because of consistent support 

provided to GPS by the civilian leadership in the DoD and despite the 

fact that we may have forgone opportunities for more rapid 

improvement. For the future, post-2020, it should be apparent from our 

experience thus far that GPS can continue to improve quality of life and 

performance to the extent that opportunities for those improvements 

continue to be incorporated into its total system design within the global 

PNT architecture. GPS initiatives for the future should focus on 

proactive improvements to GPS service fidelity and robustness to 

continue expanding its performance benefits while protecting against 

possible asymmetric attacks directed at GPS enhanced infrastructure 

components. 

Military Effectiveness Issues 

Improvements Needed, Implementation Lacking – While GPS has 

proven itself technically effective in meeting military mission 

requirements in general, it is neither robust enough to overcome credible 

jamming threats nor are the military signals available in sufficient 

quantity to meet warfighter needs under many likely operational 

scenarios. Operational control and equipment acquisition strategies 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 7

now being executed are insufficient to address these deficits as rapidly 

as necessary. The warfighter leadership is becoming more aware of the 

extent to which GPS is integral to individual mission concepts of 

operation and operational architectures. However, this growing level of 

awareness has yet to translate into accelerated implementation, or even 

plans for implementation, of the GPS improvements necessary to 

effectively support those missions and architectures in the future. The 

Task Force finds this lack of improvement to be unsatisfactory, and has 

included recommendations to stimulate proactive planning for GPS 

improvements within the operational planning process. 

Serious Delays Affecting Military Signals and Equipment -- Full 

operational availability of new military GPS signals, and the user 

equipment to receive them, is not forecast before 2013 (24 satellites), 

though the first new signals will be on GPS Block IIR-M satellites to be 

launched beginning in 2005. The GPS control segment has experienced 

significant problems over the last several years in activating new 

capabilities even as the GPS satellites have evolved, and those problems 

persist. There are also coverage gaps in the military GPS signal monitor 

network that have affected timely identification of satellite problems. 

The coverage problems will be mitigated to a large extent with the 

addition of data from six National Geospatial Intelligence Agency 

(NGA) monitor stations, improving the visibility of the constellation to 

the control segment. However, unanswered questions remain about use 

of additional global monitoring data collected by civil government and 

scientific organizations. To date the Air Force has not included the 

monitoring of the civil signals as an element of its mission of operating 

GPS. In consideration of its overall responsibilities for GPS operation, 

the Task Force included recommendations for the Air Force to add civil 

monitoring and performance measurement to its operational control 

mission. 

Higher Anti-Jam Margins are Essential ASAP – Recent experience 

in Iraq has shown that the ability to maintain GPS service to our military 

forces in the presence of hostile jamming is essential. The principal 

vulnerability affecting that objective is the threat of proliferated, 

inexpensive, low-power jammers. Improved versions of these jammers 

are now being offered in the international arms market. Potential 

enemies are undoubtedly aware of GPS effectiveness, and will take 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 8

advantage of this jammer technology in future conflicts. It is imperative 

therefore that anti-jam margins for military GPS equipment be raised in 

order to mitigate the effect of these low power jammers. Additionally, 

the potential growth in the use of proliferated ultra-wideband 

networking and communications devices and its effect on the noise floor 

will likely make consistent reception of all GPS signals more 

challenging, particularly in metropolitan areas. 

Anti-Jam Solutions are Known but Implementation Lags Need – 

Two principal techniques are available to decrease vulnerability: more 

power in the GPS satellite signal, and improved technology in GPS user 

equipment. While increasing the delivered power of the transmitted 

satellite signal using a spot beam antenna is in the current GPS III plan, 

it will not be available for the full constellation until at least 2020. The 

current GPS program of record for user equipment will not field such 

anti-jam capability improvements in significant numbers for 10-15 years. 

Development of new user equipment capable of receiving all military 

GPS signals is underway. However, preproduction prototypes will not 

be available until at least 2008, and those will only represent two card 

designs, one for avionics and one for ground receivers. Obtaining 

modernized user equipment in other form factors for other platforms 

and weapons will require separate development efforts not presently 

planned or budgeted. Also, the current user equipment development 

program is focused on integrating the new military signal structure with 

existing GPS signals. Additional effort is needed to advance and 

integrate digital processing and antenna technologies that will provide 

sufficient anti-jam margin to defeat jammers already appearing on the 

international market. Because of the importance of these issues to the 

overall objective of achieving timely and affordable improvements in 

GPS anti-jam performance, the Task Force convened a separate subgroup to focus particular attention on them. Following that review, the 

Task Force concluded that schedule and cost risk in the GPS-III program 

are real and its very long procurement schedule leaves an intolerable 

window of jamming vulnerability. These concerns can be addressed by 

an approach that improves military receivers in the near term as the 

GPS-III program proceeds. 

Exclusivity a Two-Edged Sword; Preserves Military Access but 

Limits Options – Since the inception of GPS, use of an exclusive military 

signal has been a guiding component of GPS security policy. A critical 

element of that security policy, navigation warfare (Navwar), is a set of 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 9

strategies and capabilities designed to preserve the asymmetric 

advantage afforded by GPS in the battlespace. Exclusive access to a 

military GPS signal set is one of the central tenets of Navwar. 

Maintaining such an asymmetric advantage in position determination, 

movement and timing over an adversary requires access to exclusive 

frequency spectrum and use of signal processing, encryption and 

physical protection measures that make military GPS receivers more 

complex and costly than comparable civilian receivers. Because of their 

complexity, and related security requirements, those measures also 

preclude early migration of GPS functions to “software-only” radio 

systems. Further, the pending advent of new civil and military signals 

presents opportunities for more diverse signal reception strategies that 

may increase service robustness in many situations. The Task Force 

does not recommend abandoning exclusivity or the capabilities afforded 

by Navwar. However, the Task Force considers the rigid application of 

exclusivity to be constraining to potential signal reception benefits that 

can result from the future diverse signal mix. Consequently, the Task 

Force recommends adjustments to current GPS receiver acquisition 

policies to permit more flexible procurement of GPS user equipment 

within approved military mission Information Assurance parameters. 

The Task Force also recommends including increased signal flexibility in 

the satellites to permit operational choices with regard to exclusivity in 

the longer run. 

30 Satellites Enable 15 Degree Mask Angle and Urban/Mountain 

Coverage – There are no plans at present to manage the GPS 

constellation to provide continuous availability of more than 24 satellites 

on orbit, though at least 30 satellites are necessary to assure adequate 

signal coverage at a minimum 15 degree mask angle to support ground 

operations in mountainous terrain and urban environments. Trade 

studies show that a more realistic number of operational satellites would 

be in the 30 to 36 range, and the Task Force concurs that a 30 satellite 

constellation is necessary to provide the required service in challenged 

environments. A larger constellation should also be deployed in three 

planes vice the current six plane configuration. 

GPS III Cost & Weight are Critical Issues – In this context, there is 

also a very high level of concern among the Task Force membership 

regarding projected growth in cost and weight of future generation GPS 

satellites. Affordability is a driving factor in operating and sustaining a 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 10

satellite constellation of this size, and the Task Force finds that the GPS 

III payload as currently envisioned will probably not be affordable in 

terms of satellite cost and weight. Both factors together determine 

payload-to-orbit costs, which, if not closely controlled, create an 

unacceptable budgetary environment in which to consider constellation 

size and replenishment rate decisions. History has shown that the Air 

Force has had chronic difficulty in adequately funding GPS, even in the 

absence of the more expensive GPS III satellites. If the Air Force 

continues to use its GPS investments as a funding source to offset other 

space/aircraft programs, then GPS service continuity will remain in 

jeopardy even without the more costly GPS III. The Task Force 

recommends that cost and weight of the GPS III satellites be key 

parameters in their design, and specifically recommends measures to 

limit GPS III weight to ensure two satellites may be launched aboard a 

medium-class launch vehicle. 

Civil Performance and Competitiveness Issues 

U.S. Should Take Leadership Role – As noted above, the economic 

and social value of a global PNT system based on GPS civil services is so 

compelling that the U.S. should lead the way in assuring that this global 

infrastructure is created and maintained. In this context, GPS service to 

civil users is confronted with a similar situation as that facing the 

military. Satellites to be launched beginning this year will contain the 

capability to transmit new civil signals that were announced by the U.S. 

Government several years ago but have been delayed. Even so, the 

capability to operationally control those signals will not be present in the 

GPS control segment until 2009 at the earliest, and that date is uncertain 

pending determination of a revised acquisition strategy for GPS control 

functions. With the FAA’s supplemental WAAS system and the Coast 

Guard’s NDGPS, GPS is now providing 1 to 2 meters of accuracy in the 

US. Similar European systems provide equivalent capability. Thus, civil 

expectations for GPS service fidelity are high and substantially surpass 

the official commitment to civil performance (SPS Signal 

Specification/Performance Standard) signed up to by the DoD 

beginning several years ago. Initiatives are underway to consider use of 

civil signal monitoring data by the GPS operational control system as an 

additional source of information regarding civil signal fidelity in 

conjunction with an updated civil service performance standard. The 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 11

Task Force felt it was important that the Air Force, in its operation of 

GPS, should seriously consider taking advantage of well-established 

global monitoring capabilities operated by civil and scientific 

organizations. 

EU’s Galileo Presents Challenges & Opportunities – The emergence 

of Galileo as a potential European counterpart or competitor to GPS 

heightens the importance of GPS civil performance. The Europeans 

have offered both security and economic reasons to justify creation of a 

Galileo system in parallel with GPS. European entry into this arena has 

changed the world’s perspective on the composition of a global PNT 

system. The projected business models for Galileo may impact the use 

of GPS; however, it is too early to project how Galileo will be 

implemented, and the EU has not yet fully established the financing 

necessary to bring it into sustainable operation. 

Final Galileo Form Remains Uncertain, but Discussions Offer 

Promise – The June 2004 U.S.-EU agreement on GPS/Galileo 

cooperation is encouraging in that it appears to have resolved several 

technical compatibility issues and establishes an environment for further 

cooperation. Diverse perceptions that arose during negotiation of the 

agreement regarding comparability of service between the two systems 

remain to be resolved as cooperative discussions proceed under the 

agreement. Even with the agreement in place, uncertainty remains 

regarding the eventual form Galileo will take as well as regarding 

European resolve to bring it into full operation. In this context, the 

recently signed Presidential directive establishes as a goal that U.S.-

provided civil GPS services and augmentations remain competitive with 

foreign civil systems. If/when Galileo is fully operational, its additional 

satellites should increase signal availability and overall system integrity 

for dual mode civil GPS-Galileo receivers. This should be particularly 

useful for users in urban “canyons” and other obstructed areas. In more 

open environments a single receiver may see a sufficient number of 

satellites to enable signal integrity verification within the receiver itself. 

The cooperative discussions now envisioned with the EU should have 

such improvements as an objective. From a military perspective, 

Galileo’s eventual form could present additional challenges with 

potential effects on Navwar implementation in the NATO environment. 

As Galileo evolution and adoption proceeds, the DoD must be prepared 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 12

to address its possible use by one or more NATO nations or for NATO 

purposes. 

Governance Issues 

GPS Serves Broad & Crucial National Purposes – GPS has become a 

truly “national” program of critical importance to essentially all aspects 

of U.S. life and well beyond the scope of any single Department. The 

burden of justifying the capabilities appropriate for GPS and the 

resources to implement those capabilities falls on the DoD, which has an 

easily identifiable worldwide need for the system. Civil, commercial 

and scientific users around the world who are now dependent on GPS 

are not institutionally organized to justify and pay for any system 

characteristics peculiar to their needs that exceed those of the military. 

Perception of Military Dominance in Governance – Even though 

the current interdepartmental governance structure seeks to support the 

needs of civil and military users without prejudice, there is a perception 

that the military exerts undue influence in decisions affecting civil GPS. 

This perception has been used as a principal argument by those who 

would seek to advance competing technologies or services to supplant 

or ‘augment’ GPS, in some cases where technical or economic 

justification falls short. It has also provided potential underpinning for 

various initiatives to commercialize GPS in order to improve its financial 

base and to generate non-defense resources for system operation and 

improvement. 

Need to Assess Viability of Alternative Governance Structures – 

Over the past two years, studies have been authorized by the Deputy 

Secretary of Defense to investigate the viability of alternative 

governance structures for managing and financing GPS to both sustain 

and enhance its services for its full complement of domestic and 

international users. The studies to date have found that such a strategy 

could be feasible; however, much additional work would be necessary 

before any such changes could or would be implemented. The Task 

Force believes that any substantive change in GPS governance would 

require extensive cooperation and support among the Executive and 

Legislative Branches of U.S. Government, as well as commercial 

acceptance by GPS users. 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 13

Comprehensive National Strategy has been Lacking – In its 

implementation and operation of GPS thus far, the U.S. Government has 

not made use of a comprehensive strategy accounting for all the national 

equities at stake in the resolution of issues affecting acquisition and 

operation of the system. Similarly, there has not been a systematically 

constructed and commonly accepted architecture to foster consensus 

among the various agencies responsible for implementation of GPS and 

its components and complements. The recently signed Presidential 

Directive is intended to strengthen the interagency management process 

and requires the preparation and update of a 5-year space-based PNT 

Plan which could provide the basis for such a strategy. 

Responsibilities & Authorities for GPS in DoD Need Clarification 

– Within the DoD, policy and operational responsibilities for GPS have 

been diffused by various management decisions over the last several 

years. The sometimes overlapping, sometimes disconnected roles of the 

OSD staff components, the Joint Staff, the U.S. Strategic Command 

(STRATCOM) and the Air Force, as DoD Executive Agent for Space, in 

the management of GPS have created some confusion over where 

responsibility actually rests. This sense of confusion has also impacted 

civil and international perceptions of the importance the U.S. places on 

GPS and the commitment of the U.S. to GPS sustainment and evolution. 

It is incumbent on the DoD to redefine lines of authority and 

responsibility for the system and to reestablish its position of leadership 

for GPS as the heart of the space-based PNT infrastructure both 

domestically and internationally. The Task Force recommends that the 

DoD remain the steward for all GPS satellite services and considers it 

vitally important that GPS responsibilities within the Department be 

clearly assigned and described. The Task Force recommends that the 

Secretary of Defense provide such clear guidance applicable to the full 

range of military and civil GPS signal services in the future. 

TASK FORCE RECOMMENDATIONS

Before detailing our recommendations, it is important to delineate 

priorities for GPS customers: the worldwide military, civil, commercial 

and scientific users who benefit from and rely on its services. 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 14

GPS User Priorities: 

As shown in the following table, GPS user priorities are generally 

common. 

User Priority Military GPS User Civil, Commercial, 

Scientific GPS User 

Availability (Short and 

long term and despite 

interference) 

9 9

Accuracy 9 9

Bounded inaccuracy 9 

(Minimize collateral 

damage) 

9 

(Assure service integrity) 

Denial of PNT sources to 

hostile parties 9

A substantive role in 

determining system 

configuration (Governance) 

9 9

Compatibility with like 

services (e.g., Galileo, 

QZSS, GLONASS) 

9 9

Table 1. GPS User Priorities 

SYSTEM AND PROGRAM RECOMMENDATIONS

GPS Satellites and Constellation (Improve Availability and 

Accuracy) 

 Commit to sustaining a 30-satellite constellation (vice 

the current 24). 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 15

− Increases tolerable mask angle from 5 degrees to 

15 degrees to improve performance in 

mountainous terrain and urban environments. 

 Configure the constellation in three planes with 10 

satellites per plane (this will simplify constellation 

sustainment, enabling dual satellite launches to be 

conducted more efficiently than for a six-plane, fivesatellite per plane configuration). 

− Begin transition from the current six-plane 

constellation as soon as possible rather than 

waiting until GPS III launches begin. 

 Limit GPS III satellite weight to permit launch of two 

satellites on a single mid-size EELV 

− If the satellite exceeds weight or power 

thresholds that would compromise dual-manifest 

(maintain sufficient margin for each through 

development), the removal of secondary 

payloads must be evaluated. In this instance, 

NDS mission modifications and alternatives must 

be explored. 

− A regional signal (broader beam) should be 

considered as a lighter-weight and less complex 

alternative to the narrow spot beam planned for 

GPS III. 

 Continue to acquire high fidelity space-based clocks 

and navigation payloads to enable direct, highreliability military accuracy in the range of 2-4 meters 

for precise targeting and weapons delivery (ensure that 

the industrial base for this technology is assured). 

 As a part of the acquisition strategy for GPS III, include 

the option to procure higher power earth coverage 

satellites without non-GPS payloads to permit 

operation of a mixed constellation of higher-cost, high 

functionality satellites and lower-cost, utility satellites, 

increasing signal robustness and availability while 

lowering overall constellation life cycle costs. This will 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 16

also provide significant global mitigation for GPS 

against both intentional and unintentional interference. 

 Incorporate a fully reprogrammable Navigation 

Payload aboard GPS satellites as soon as practicable to 

enable future flexibility in signal structure and content. 

GPS Control Segment and Satellite Operations (Improve 

functionality, Accelerate Capability)

 In the face of continuing, intractable Operational 

Control Segment (OCS) development problems, 

provide a near-term workaround to allow early and 

continuous operation of all new signals as they are 

present on-orbit (M-code, L2C, L5 and, eventually, 

L1C). 

− Use of the new civil signals will be on an “atrisk” basis, pending declaration by the AF of full 

operational status. 

 As a solution to long-standing OCS development 

problems, conduct a parallel development of OCS 

functionality based on layered control engineering 

principles with clearly defined application 

programming interfaces between software components 

rather than the current heavily patched software 

engineering methodology that has proven unworkable. 

− This recommendation is consistent with that 

contained in a tasking conveyed to the Air Force 

by the ASD (NII) in DoD PNT Executive 

Committee meetings during early-mid 2003. 

 Modify the operational concept for satellite operations. 

− Air Force personnel continue to provide guidance 

and direction to satellite operations. 

− As a means of mitigating the disruptions caused 

by personnel turnover and to provide an 

experienced cadre of GPS operators, selectively 

integrate contractor technical personnel into 

positions involving direct satellite system 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 17

monitoring and execution of commands. In 

addition to its other benefits, implementing this 

practice should result in operational cost savings 

for the Air Force as well as freeing uniformed 

billets for other assignments. 

 Implement direct, independent and continuous 

monitoring of both military and civil operational 

capability. This should include projections of capability 

to meet user needs in both normal and stressed 

environments as well as historical data to provide 

assessments of past performance, as necessary. 

− For military assessments and projections, 

complete the addition of remaining National 

Geospatial-Intelligence Agency monitor station 

data into the OCS. 

− Include a direct connection to the WAAS 

monitoring system. This would provide very 

high fidelity continuous sampling of GPS 

availability, integrity and accuracy in the U.S. 

− For civil assessments and projections, consider 

use of existing worldwide civil, commercial and 

scientific GPS monitoring networks. 

− As a means of improving GPS global 

competitiveness, the GPS Civil Performance 

Standard should be updated to more closely 

reflect system performance improvements. 

− Establish an independent “civil report card” 

based on the WAAS monitoring network. This 

should be included in the weekly assessment of 

GPS performance. 

GPS Military User Equipment Acquisition and Installation 

(Accelerate Anti-Jam Capability) 

 Each Service should fund its own R&D program to best 

ensure position and timing information is integrated 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 18

into equipment and operational capabilities, following 

a STRATCOM-developed roadmap for joint, integrated, 

seamless, precision operations and to ensure operation 

in accordance with a STRATCOM established PPS 

performance standard. 

 Continue fielding Selective Availability Anti-Spoofing 

Module (SAASM) GPS equipment for missions and 

applications where access to exclusive GPS military 

signals is necessary pending production and 

operational availability of user equipment 

incorporating the M-Code and other modernization 

features (see below). 

 Evolve GPS user equipment from SAASM to YMCA 

configurations as rapidly as possible. 

− Change policy guidelines for procuring future 

GPS user equipment to permit at least three 

levels of performance and protection. 

 Full capability to operate with “military exclusive” GPS 

signal(s). 

 Full capability to operate with “military exclusive” GPS 

signal(s) with the additional capability to receive and 

exploit other civil and foreign satellite navigation 

signals. 

 User equipment not configured for exclusive military 

signals but which can receive and exploit the full range 

of accessible signals to enable less expensive operations 

in more benign interference environments. 

 In parallel with development of YMCA and M-Code 

user equipment, invest in complementary technologies 

that promise significant improvements in anti-jam 

performance. Integrate these features into SAASM and 

YMCA receiver designs at the earliest opportunity. 

Such technologies include, but are not limited to: 

− Adaptive multi-beam steering to counter 

proliferated mobile jammers 

− Digital antenna processing 

− Narrow-band adaptive filters 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 19

− Vector delay lock tracking 

− Deep inertial coupling 

− Network assist for acquisition/better platform 

handoffs 

− All-in-view 

− Chip-scale atomic clocks 

 Carefully plan for early integration of anti-jam receiver 

technology into high priority/high payoff weapon 

systems. 

− Develop a silver-bullet force comprised of 

specific delivery platform types equipped with 

upgraded GPS-aided munitions capable of 

operating in hostile jamming environments. 

− Ensure mission concepts of operation and system 

architectures accurately reflect GPS contributions 

and relevant concepts of operation are updated to 

define workable employment concepts for silverbullet resources. 

 Continue efforts to evolve the current security 

architecture to the more diversified and robust 

PRONAV security architecture. 

 One decision that the Task Force considers essential to 

improving opportunities for future flexibility in GPS 

satellites and user equipment is to permanently 

eliminate the requirement for Selective Availability in 

all future equipment designs with the objective of 

deleting the hardware and software overhead for its 

implementation from throughout the future system. 

Improving Anti-Jam Performance

 Initiate an aggressive program to introduce anti-jam 

enhancements soon in appropriate military receivers, 

namely: 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 20

− Receivers that are being redesigned to 

accommodate M-code 

− Receivers in new weapon systems being 

developed 

− Selected “silver-bullet” subsets of receivers in 

munitions 

 Proceed with GPS III with a firm resolve and process to 

control satellite weight such that two satellites can be 

launched on a single booster, namely: 

− Control “requirements creep” through consistent 

program oversight exercised by the ASD(NII) 

and USD(AT&L) 

− Maintain sufficient weight and power margins 

through development 

− Be prepared to off-load portions or all of other 

payloads such as NDS if necessary. 

Dealing with Galileo

 Remain open to and promote opportunities for 

cooperation under the recent U.S.-EU agreement and in 

accordance with the recent Presidential Directive. 

 Strongly promote true civil interoperability – well 

defined geodetic and time transformations that can be 

easily implemented in user equipment. 

 Insist on full disclosure of the open signal structure. 

 Continue purposeful implementation of a separate 

strategy to provide a superior military and an 

acceptable civil PNT capability for U.S. interests 

globally using the militarily supported GPS as the core 

capability. 

 Maintain a PNT system configuration that will permit 

Galileo assets to increase the capability presented by 

the combination of both systems for civil users. 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 21

 Prepare for discussions within the NATO environment 

regarding possible use of Galileo services for military 

purposes by NATO member nations. 

 Explore with the Europeans a collaborative approach 

that maintains the sovereign independence of both 

parties while permitting the creation of greater 

capability at lower cost than either could achieve alone 

for commercial benefit. 

 Explore cooperative exchange of monitoring 

information. 

Organization and Governance

 The recently signed Presidential Directive on SpaceBased PNT affords an opportunity for all stakeholders 

to correct deficiencies of the former Interagency GPS 

Executive Board. The following recommendations 

address the effectiveness of the new structure. 

− If Deputies do not routinely participate, then 

designated representatives to the National SpaceBased PNT Executive Committee (NPEC) must 

be formally empowered to speak for and act on 

behalf of their respective Deputies for all matters 

coming before the NPEC. 

− Strengthen the effectiveness of the full-time 

National Space-Based PNT Coordination Office 

(NPCO) by formally designating senior technical 

focal points within each department who will 

keep the NPEC principals fully apprised of all 

PNT matters being developed by the NPCO for 

executive level consideration and action. 

− Stakeholders can use this forum to investigate the 

viability of alternative methodologies for 

managing and financing GPS to address current 

issues and more effectively sustain and enhance 

services for its full complement of domestic and 

international users into the future. 
 

EXECUTIVE SUMMARY ___________________________________________________________ 

_________________________________________________________________________ 22

 The Secretary of Defense should also clarify lines of 

authority and responsibility within the Department to 

eliminate ambiguity regarding GPS responsibilities that 

hinders decision making internally and that 

perpetuates the perception externally that the DoD has 

lost sight of its GPS stewardship responsibilities. 

− Designate a single focal point within the Office of 

the Secretary of Defense responsible for all GPS 

policy and oversight matters including clearly 

defined relationships with the Joint Staff and 

Services (including the Air Force) regarding GPS 

operations and acquisition, respectively. 

− Use the DoD PNT Executive Committee process 

to conduct a top-to-bottom review and develop 

recommendations regarding organizational 

structure(s) for DoD PNT role. 

− Sponsor and lead an interagency effort to 

develop a comprehensive national PNT 

architecture to guide future investment and 

implementation decisions regarding GPS and 

complementary systems and technologies. 

− The Secretary of Defense should reemphasize in 

writing the criticality of GPS operations, similar 

to the emphasis he has previously issued for GPS 

acquisition. 

 Commander STRATCOM can quickly demonstrate 

improved operations through support of Commander 

14th AF tasking to stand up a Joint GPS Service Support 

Center (as part of the Joint Space Operations Center). 

The center’s primary operational task would be 

improved position and time services to military users, 

achieving this initially through the collection and 

assessment of GPS monitor information from reliable, 

independent global sources and in the longer term by 

providing operational guidance for updating the 

control segment software. The center could also 

provide a source of information on all foreign GNSS 
 

__________________________________________________________ EXECUTIVE SUMMARY

___________________________________________________________________________ 23

available (GLONASS, Galileo, other systems), for space 

situation awareness. 

− In fulfilling its stewardship obligation for 

providing civil and military space-based PNT, 

the Commander, STRATCOM should be directed 

by the Secretary of Defense to develop and 

maintain a roadmap for achieving joint, 

integrated, seamless, precision military 

operations, to coordinate Service-developed user 

equipment roadmaps for compatibility and to 

establish and maintain SPS and PPS performance 

standards. STRATCOM could then task its 

component (Air Force Space Command) to 

implement standards and reporting criteria in 

accordance with routine joint system 

performance reporting instructions. 

− Include designated representatives from 

STRATCOM on all DoD and interagency 

executive committees and working groups 

involved with management and operation of 

GPS. 

− Ensure that the concept of stewardship for GPS 

operations as passed from the Secretary of 

Defense to STRATCOM includes responsibility 

for being aware of and meeting civil service 

performance needs as mutually agreed between 

the DoD and civil users and reflected in the GPS 

Civil Performance Standard. 
EXECUTIVE SUMMARY ___________________________________________________________ 

________________________________________________________________________ 24

This page intentionally left blank. 

. 
CHAPTER 1. INTRODUCTION _______________________________________________________ 

________________________________________________________________________ 25

CHAPTER 1. INTRODUCTION

1.1 TASK FORCE APPROACH

This Task Force on the future of the Global Positioning System (GPS) 

was originally empanelled to assess the implications for GPS from a civilcommercial Galileo, the European Union’s proposed Global Navigation 

Satellite System (GNSS). The Terms of Reference (Appendix A) also 

requested assessment of several other aspects of GPS military and 

commercial competitiveness and of upgrade strategies and technical 

alternatives. 

The Task Force was comprised of acknowledged GPS experts with 

extensive public and private sector experience (Appendix B). 

Assessments of the various issues before the Task Force were obtained 

through the insights and extensive experience of the members. Use of 

outside briefings was minimized, and those presented to the group 

(Appendix C) were focused primarily on updating current program 

activities bearing on specific issues under consideration. 

1.2 GPS DESCRIPTION

GPS is a space-based positioning, navigation and timing system 

developed by the U.S. Department of Defense (DoD). It emerged in the 

late 1960s and early 1970s as a merger of synergistic Navy and Air Force 

programs for timing and space-based navigation, respectively. The U.S. 

Air Force currently finances and operates the basic system of 24+ satellites 

and associated ground monitoring stations located around the world. 

GPS is widely characterized as a satellite navigation or a satellite 

positioning system, providing signals for geolocation and for safe and 

efficient movement, measurement, and tracking of people, vehicles, and 

other objects anywhere from the earth’s surface to geosynchronous orbit 

in space. A less-known element omitted from many GPS descriptions is 

the embedded timing that serves an essential role in its navigation 

services. The precise time and stable frequency signals available from 
 

CHAPTER 1. INTRODUCTION ______________________________________________________ 

_________________________________________________________________________ 26

GPS are at least equal in importance to its navigation and velocity 

determination functions. They serve as synchronization sources for global 

communications, electronic transactions of all types, power-distribution 

networks and innumerable other applications. 

From its beginning, the GPS architecture was designed to minimize 

military navigation and timing vulnerability by moving the vital 

electronic processing and transmitting equipment into space to make 

them extremely difficult to reach. From there, GPS signals provide a 

multi-mission force multiplier service for an unlimited number of U.S. and 

allied military users. Though many believe civil applications only came 

along much later, in fact, GPS scope was expanded early in its 

development to include complementary civil capabilities as well. 

Simplistically, GPS implements a time-difference-of-arrival concept 

using precise satellite position and on-board atomic clocks to generate 

navigation messages that are continuously broadcast from each of the GPS 

satellites. These messages can be received and processed by users 

anywhere in the world to determine position and time accurate to within a 

few meters and a few nanoseconds, respectively (Figure 1). 

Figure 1 How GPS Works 
 

______________________________________________________ CHAPTER 1. INTRODUCTION

___________________________________________________________________________ 27

Each GPS satellite on-board computer and navigation message 

generator knows its own orbital location and system time very precisely. 

A global network of monitor stations keeps constant track of these 

parameters. Corrections are uploaded to each satellite at least daily by the 

worldwide operational control segment with Master Control Station at 

Schriever Air Force Base near Colorado Springs, Colorado. The uploads 

include orbit position projections for each satellite in the constellation, 

based on sophisticated models and effective for several weeks, as well as 

corrections to on-board satellite clocks. All GPS satellite capabilities are 

enabled by control segment software. New capabilities designed into the 

satellites require corresponding control software to be developed, tested 

and validated for operational use before those capabilities can be declared 

operationally available for GPS users. 

System time is maintained aboard each satellite by Cesium and 

Rubidium atomic frequency standards. In general, these on-board clocks 

are accurate to within a few nanoseconds of global coordinated time 

(UTC) as maintained by the Master Clock at the U.S. Naval Observatory 

and are individually stable to a few parts in 1013 or better. Early GPS 

satellites contain two Cesium and two Rubidium standards each, later 

versions have all Rubidium standards. Only one standard is operational 

aboard each satellite at any given time. 

To produce accurate positions in three dimensions, a user must be able 

to see four GPS satellites, separated sufficiently and geometrically 

oriented in three-dimensional space so that processing will define a 

precise signal intersection. After much analysis, this basic requirement for 

simultaneous multi-satellite global coverage resulted in a constellation 

design comprising at least 24 satellites at semi-synchronous altitude 

(about 11,000 nautical miles). The system was originally designed with 

eight satellites in each of three orbital planes, inclined at 63 degrees; 

however, as a result of budget fluctuations during system development, as 

well as a plan to launch GPS on the Space Shuttle (later abandoned), the 

current operational constellation was implemented in six orbital planes, 

each of which is inclined at 55 degrees (Figure 2). 
 

CHAPTER 1. INTRODUCTION ______________________________________________________ 

_________________________________________________________________________ 28

Each GPS satellite transmits the navigation messages in military and 

civil signals in the L-band at L1 (1575.42 MHz) and military only signals at 

L2 (1227.6 MHz). A new civil signal will be added to L2 beginning in 2005 

and an additional frequency will be added for civil use in late 2006 at L5 

(1176.45 MHz). The GPS receiver uses the position and time information, 

broadcast in the navigation messages and traveling at the speed of light, to 

calculate approximate ranges to each of the satellites within line of sight to 

its antenna. These approximate ranges are called pseudoranges, since 

biases in the user receiver clocks prevent the precise individual ranges 

from being measured directly. The pseudorange from each individual 

satellite for a specific but unknown value of user clock error defines a 

sphere on which a user may be located in three-dimensional space. The 

intersection of three spheres defines a point, though the intersection is 

imprecise due to the aforementioned biases in the receiver clock (which in 

nearly all cases is not an atomic clock) and to effects of ionosphere and 

atmosphere on the signal transit time. Addition of a pseudorange from a 

fourth satellite allows calculation of the user receiver clock error and 

permits computation of the three physical dimensions of the precise 

intersection, as well as precise time. GPS operates within an EarthCentered-Earth-Fixed (ECEF) reference frame, so position determinations 

are essentially independent of the local topography, which must be 

accommodated by geodetic models within the GPS receivers. The 
 

______________________________________________________ CHAPTER 1. INTRODUCTION

___________________________________________________________________________ 29

baseline geodetic reference for GPS is World Geodetic System 1984 (WGS84), though many other geodetic references are included in most GPS 

receivers. 

1.3 INTRODUCTION OF THE ISSUES

The GPS comprises the core component of a broader, worldwide PNT 

system-of-systems that is important for the U.S. military, for the U.S. 

economy and infrastructure, for military allies and coalition partners of 

the U.S and for the world’s economy and infrastructure. The PNT systemof-systems consists of both local-area and space-based (wide-area) 

augmentation services designed to enhance GPS accuracy and/or 

availability. It also includes complementary stand-alone systems such as 

inertial measurement units and electronic clocks that work in close 

connection with GPS, which serves to mitigate the natural drift of standalone systems. There is also a reverse benefit from GPS-inertial coupling, 

as the inertial aids the GPS processors to maintain dynamic tracking in the 

presence of high accelerations. 

As a direct result of its integral functions in the global PNT system-ofsystems, we as a nation have become critically dependent on GPS. This 

point requires emphasis because the extent of our dependence on GPS, 

derived from its effectiveness and pervasive availability, amounts to a 

new paradigm which military and civilian decision makers must take into 

account. Efficiencies in positioning, movement and timing derived from 

the ubiquitous GPS signals have already quietly permeated virtually 

every level of our national infrastructure to the extent that, in many cases, 

there is no going back to earlier ways of doing things without tremendous 

but unrecognized penalties. All of the domains, missions and 

infrastructure components addressed by this Task Force are already 

affected to a greater or lesser degree by this dependency, and we believe 

the effects will only become more pronounced over time. 

From outward appearances, GPS seems a healthy, successful program. 

At its current level of performance and with nearly thirty satellites in the 

constellation, GPS is providing, on average, better than 5-meter horizontal 

accuracy, better than 10-meter vertical accuracy and absolute time within 

0.1 microsecond of Universal Coordinated Time (UTC). With differential 
 

CHAPTER 1. INTRODUCTION ______________________________________________________ 

_________________________________________________________________________ 30

GPS techniques, local accuracies of 1-meter and better are routine. 

However, our investigation into various aspects of GPS operation and 

management reveals serious issues that affect its operational viability and 

require prompt leadership action to correct. These include issues of 

military effectiveness, civil performance and competitiveness, and 

governance. 

In the ongoing transformation of military capabilities, assurance of 

precision affords a basis for new military operational concepts, and GPS 

provides the core infrastructure component for precision. Many of these 

new operational concepts have as essential elements small conventional 

munitions that enable tailoring of attack effects while minimizing 

collateral damage. These new concepts are particularly demanding of 

accuracy in both target location and weapon delivery and of precision 

signal service availability. New paradigms such as the Air Force’s small 

diameter bomb (see Appendix D), the Navy’s Extended Range Guided 

Munition (ERGM) and the Army’s Excalibur XM982 GPS-guided artillery 

projectile epitomize these new miniaturized munitions. The consequences 

for future military requirements of using these smaller munitions will be 

felt in areas of accuracy and of anti-jam signal and receiver performance. 

Within this context, from a military perspective, the Task Force 

considered the following issues: 

 The potential of constrained investment leading to below 

minimum required number of satellites on orbit. 

 Inadequate numbers of satellites for many applications in 

the longer run. 

 Availability of anti-jam capability and the threat of 

increasingly more potent and possibly mobile jammers. 

 Control and User segment schedules do not match 

satellite availability. 

 The value of military signal exclusivity and its attendant 

costs. 

 The state of the Operational Control Segment relative to 

monitoring GPS signal fidelity and operating the satellite 

constellation. 

 The status of GPS III and the factors affecting cost and 

weight of proposed GPS III satellites. 
 

______________________________________________________ CHAPTER 1. INTRODUCTION

___________________________________________________________________________ 31

 GPS has also become a critical element of infrastructure 

for positioning, navigation and timing for a wide variety 

of civil applications and for countless commercial 

applications. PNT is a big business and growing. A 

variety of government and private sector studies have 

projected multi-billion dollar annual markets for civil 

and commercial GPS-enabled products and services 

continuing into the future. These studies focus on 

projected sales and do not project the multi-sector cost 

savings attendant on the ubiquitous use of GPS and the 

attendant efficiencies in operations and safety it affords 

affecting both the U.S. and international economies. 

 Within this context, from the perspective of civil and 

commercial applications, the Task Force considered the 

following issues: 

− The potential of constrained investment leading to 

below minimum number of satellites on orbit. 

− Inadequate numbers of satellites for many 

applications in the longer run. 

− The perception in the civil/commercial sector and 

the international community that the U.S. military 

dominates decisions about the system and is not 

responsive to their needs and concerns. 

− The potential effects of the European Galileo 

system on the U.S. leadership position with respect 

to global PNT. 

The economic and social values of a global PNT infrastructure based 

on GPS-like systems for both military and civilian purposes are 

compelling. The U.S. should take a position of leadership in assuring that 

this global infrastructure is created and maintained. Within this context, 

the Task Force considered the following issues: 

 The strategic value to the United States of GPS as a 

central component in a coherent, global PNT system. 
 

CHAPTER 1. INTRODUCTION ______________________________________________________ 

_________________________________________________________________________ 32

 Assuring availability of GPS to U.S. military forces in 

times of stress and conflict. 

 Providing confidence to the civil, commercial and 

international communities that they can depend on GPS 

as a long term part of their PNT infrastructure. 

 Necessary actions to achieve these objectives (capability, 

resources and schedules). 

 Appropriate operations, management and governance 

structures. 
CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE _______________________________________________ 

_________________________________________________________________________ 33

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS AND THE 

NATIONAL INFRASTRUCTURE

2.1 NATIONAL SECURITY INFRASTRUCTURE (DOMAINS AND 

MISSIONS) 

For military missions, GPS provides an unparalleled force-enhancement 

tool. GPS aids in all aspects of military combat operations because of its 

common-datum, common-grid, common-time capabilities. GPS is unique in 

its ability to establish an unambiguous correlation in four dimensions 

between a target and a dynamic weapon system aimed at that target — all 

the time, anywhere on the earth, and under any conditions of light, weather, 

or other source of target obscuration. This translates directly into increased 

probability of kill for any particular weapon, increased force employment 

efficiency for military mission planners, and overall lower risk for the 

individual military members and units that must execute the missions. To 

the extent that a target point is defined and a weapon is guided by precise 

GPS signals, the probability that the target will be hit despite any other 

circumstances that exist is significantly higher with GPS than with any other 

combination of targeting and positioning technologies. Further, since GPS 

requires no electronic transmissions for access, it enables safe, efficient and 

precise operations in situations where complete radio silence is required. 

Because of those performance features, both the DoD and Congress have 

long mandated GPS for military operations. Its functionality has been or is 

being installed and integrated into virtually every significant operational 

warfighting and support system operated by the DoD, including 

communications and data systems. 

The following summarizes the Task Force assessment of GPS 

contributions to diverse military missions. 

2.1.1 Air Operations 

GPS enables global precision air operations in all categories of manned 

and unmanned air platforms. It permits point-to-point air navigation 

anywhere in the world without reliance on ground-based navigation aids or 

ground control through all phases of flight up to precision approach and 
 

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE________________________________________________ 

_________________________________________________________________________ 34

landing. GPS works best in aircraft applications when coupled with an 

inertial navigation unit. In this coupled configuration, GPS provides 

initialization for the inertial system and compensates for inertial drift, and 

the inertial system improves GPS tracking in the presence of high 

acceleration and changes in direction. In many applications, use of GPS 

allows lower cost inertial systems than would otherwise be required if the 

inertial were stand-alone. GPS positions relayed across Joint Tactical 

Information Distribution System (JTIDS) communications networks afford 

air commanders a continuous precise picture of the three-dimensional 

disposition of air assets. Both aircraft and weapons carried aboard aircraft 

employ GPS. However, only a few aircraft types provide the data transfer 

capability to directly initialize onboard GPS weapons so that they may 

rapidly acquire and track GPS signals once they are released from under the 

wing or from the bomb bay, thereby reducing their effectiveness. 

2.1.2 Naval Operations 

GPS enables seamless global maritime navigation on the open ocean, 

littoral waters, harbors and inland waterways. It has replaced two former 

radionavigation systems used for open ocean navigation by naval vessels 

and submarines. It has eliminated the need for high-power radio 

transmissions formerly needed for open ocean aircraft recovery in carrier 

operations. It also improves safety of close proximity operations at night 

and in limited visibility conditions. 

2.1.3 Land Operations 

GPS enables efficient and safe land operations globally. Use of GPS with 

properly gridded maps enables ground forces to conduct coordinated 

operations in featureless terrain and, when coupled with laser range 

finders, to precisely determine target coordinates from a distance for attack 

by GPS guided munitions. Integrated with tactical secure communications 

devices, GPS enables commanders to maintain continuous awareness of 

force location and movement for more effective operations and to mitigate 

fratricide. Unique constraints imposed on GPS by land operations in 

forests, mountainous terrain and urban areas can be mitigated by increasing 

military signal strength and by raising the mask angle below which signal 

reception from the satellites is blocked to at least 15 degrees. 
 

_________________________________________ CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE

___________________________________________________________________________ 35

2.1.4 Space Operations 

GPS enables highly precise and continuous determination of satellite 

orbits out to at least geosynchronous earth orbit (GEO – about 22,000 mi). 

For this purpose, GPS acts in place of ground-based radars, which must be 

scheduled and cannot track individual satellites continuously, and many of 

which are located on foreign soil. The GPS constellation orbits at about 

11,000 nmi (medium earth orbit – MEO). For satellites orbiting below about 

4,000 nmi (and low earth orbits are well below this altitude), continuous 

point positioning is possible, as with aircraft navigation. Satellites at or 

above MEO track GPS signals coming past the edge of the earth from the 

other side of the GPS constellation, and use serial data collection techniques 

for orbit determination. Use of GPS by MEO and GEO systems requires that 

GPS signals directed toward the earth be broadcast such that sufficient 

signal energy can be received by satellites on the other side of the earth so 

they can perform orbit determination calculations. 

2.1.5 Weapons Delivery 

GPS enables all-weather, day/night precision weapons delivery 

anywhere in the world. GPS has improved employment efficiency and 

accuracy of all types of bombs, cruise missiles and artillery systems. It 

affords improved safety for aircrews by enabling weapon release at 

increased stand-off ranges from targets. It affords wider ranges of 

employment options for cruise missiles in cases where lack of terrain 

features or shortage of mission planning material would have otherwise 

precluded a mission. It affords improved safety for ground support of 

forces in close contact with adversaries by enabling precise GPS-guided 

bombing or artillery fires against GPS-designated target coordinates (see 

discussion on spatial uniformity – Appendix E). 

2.1.6 Targeting 

Target location error (TLE) is the single largest contributor to total 

system error in the employment of GPS-guided munitions against fixed 

targets. To the extent that GPS is used in the determination of target 

coordinates, the ability to attack those coordinates with precision is 

significantly enhanced. GPS is used in conjunction with laser range finders 
 

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE________________________________________________ 

_________________________________________________________________________ 36

by ground forces and forward air controllers. GPS is also used in 

conjunction with synthetic aperture radar aboard aircraft to obtain precise 

targeting information relative to the aircraft’s position (see discussion on 

spatial uniformity – Appendix E).

2.1.7 Special Operations 

In addition to its contributions to land, sea and air navigation, targeting 

and weapons delivery as they apply to special operations, GPS enables 

covert and precise day/night rendezvous on land, sea and air under all 

weather conditions. The combination of precise position and timing 

information provides the capability to rendezvous without the need for 

radio transmissions or other displays which might attract unwanted 

attention. 

2.1.8 Logistics Operations 

GPS enhances safety and efficiency of all types of logistics and supply 

operations. It enables pre-positioning of military supplies in covert 

locations for planned operations as well as precise delivery of needed 

supplies when pre-positioning is unfeasible. In sea-based 

resupply/refueling and air refueling operations, it allows precise, covert 

day/night rendezvous under all weather conditions. 

2.1.9 Mine Clearing/Explosive Ordinance Disposal (EOD) 

GPS, augmented by differential techniques, enables precise charting of 

mine fields in land or water for construction of safe lanes and for improving 

safety of EOD operations. 

2.1.10 Search & Rescue 

GPS enables precise location of downed aircrew members and improves 

the probability for a successful rescue. GPS is combined with low 

probability of intercept/low probability of detection (LPI/LPD) over-thehorizon and direct communications in Combat Survivor/Evader Locator 

(CSEL) handsets now in production. 
 

_________________________________________ CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE

___________________________________________________________________________ 37

2.1.11 Communications 

GPS provides timing and frequency synchronization for wired and 

wireless communications and data networks. Synchronization is necessary 

for encrypted communications and data transmissions, in particular, and for 

maintaining efficient throughput at connection nodes between different 

networks. The U.S. Naval Observatory (USNO) is the official timekeeper 

for the DoD. As a part of its mission, the USNO maintains its Alternate 

Master Clock at the GPS Master Control Station and provides the data 

necessary to steer GPS time directly to the USNO standard. The timing 

signal from the GPS satellite constellation represents the transmitted 

version of USNO time and has been designated in JCS publications as the 

official time source for military operations. 

2.1.12 Intelligence, Surveillance and Reconnaissance (ISR) 

GPS enables increased efficiency in geo-referencing ISR data and 

provides the precise timing information used in ISR systems of all types. 

2.1.13 Net-Centric Operations 

GPS provides the timing and synchronization necessary for effective netcentric operations for both support and attack activities. It also enables 

precise short- or long-duration navigation for all types of unattended 

vehicles that may be employed in net-centric operations.

2.1.14 Battlespace Awareness 

GPS enables the spatial and communications components underlying 

effective battlespace awareness. Spatial information relayed through 

tactical comm/nav networks such as JTIDS and Enhanced Position Location 

Reporting System (EPLRS), among others, provide the foundation for 

continuous battlespace awareness at all command levels. Precise spatial 

and timing information are also important components of Blue Force 

Tracking and Joint Blue Force Situational Awareness capabilities that 

contribute to reduced fratricide and coordinated operations. 
 

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE________________________________________________ 

_________________________________________________________________________ 38

2.2 NATIONAL ECONOMIC INFRASTRUCTURE

As an information resource, GPS provides an essential linkage between 

the largely locationless electronic/communications environment and the 

physical world. Even the best overhead images and maps must be 

accurately geo-referenced in order to be useful for precise navigation and 

GPS provides that direct connection. GPS also provides primary timing and 

synchronization for most of our national telecommunications and data 

networks. In addition to its economic and scientific contributions, GPS is 

also integral to enabling speed and precision in domestic emergency 

response operations of all types. DoD and Department of Homeland 

Security officials responsible for protection of our national infrastructures 

must be aware of the contributions GPS makes to their daily operation. In 

executing their responsibilities for ensuring homeland security, federal, 

State, and local agencies will have to be able to respond quickly in the real 

world to warning and attack information from a variety of sources. GPS is 

integral to making that information immediately and uniformly useful. 

The following summarizes the Task Force assessment of GPS 

contributions to national infrastructure elements. 

2.2.1 Civil Telecommunications 

Beginning even before GPS became fully operational, global timing and 

communications infrastructures began adopting GPS as the primary 

distribution mechanism for time and frequency synchronization. The 

USNO maintains its Alternate Master Clock at the GPS Master Control 

Station and provides the data necessary to steer GPS time directly to the 

USNO standard. As a direct result, the timing signal from the GPS satellite 

constellation is being used internationally as a continuous, globally 

available source of UTC. Additionally, major national and international 

telecommunications service providers, including both wireless and wireline 

technologies, have recognized the value of using the freely accessible GPS 

timing signals. Beginning in the late 1980s, many have largely replaced their 

complements of ground-based atomic frequency standards in favor of 

receiving continuous precise time and frequency signals from GPS. With its 

signals providing a principal source of timing synchronization and 

frequency syntonization at the Stratum 1 (Primary Reference Source) level, 
 

_________________________________________ CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE

___________________________________________________________________________ 39

GPS has become an essential component in the flow of digital data between 

multiple service providers, relevant to both Internet operations and 

diversified telecommunications networks. GPS has also become an 

essential, and largely transparent, enabling technology for the economical 

operation of cellular telephone and other wireless media nationwide and 

around the world.

2.2.2 Electrical Power Distribution 

Nationwide, many electric power companies have begun to use GPS 

timing and frequency services to improve the economy and efficiency of 

their operations. They primarily use GPS signals for monitoring stability of 

line frequencies, frequency synchronizing or “syntonizing” services with 

adjacent power company networks, and isolating faults in transmission 

networks. The fidelity of service provided by GPS exceeds the routine 

needs of power companies, but its ready, free availability makes it very 

appealing, and the precise timing signal is extremely useful in isolating 

damage in remote lines to within a single tower span. GPS is also the 

technology of choice for maintaining phase differences to very tight 

standards when loads are transferred among substations, as would happen 

as a consequence of a major power perturbation. Use of GPS has enabled 

load transfers to be accomplished in a few hours where previous techniques 

required days. As electrical service deregulation spreads across the country 

while the nation faces a real new threat of intentional power grid 

disruptions, interoperability dependencies between individual service 

providers heighten the importance of GPS as companies must respond to 

widespread load variations and to system surges created by environmental 

effects such as solar storms or potentially by hostile actions of terrorists. 

2.2.3 Electronic Commerce and Finance 

Many banking and financial firms employ GPS timing for 

synchronization of their encrypted computer networks, though this 

function is in most cases buried within contracted telecommunications 

services and transparent to management. Also, computer transactions are 

routinely time-tagged, and with the advent of Internet trading, the precise 

timing of transactions is becoming more important. Presently, both the 

USNO and the National Institute of Standards and Technology (NIST) are 
 

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE________________________________________________ 

_________________________________________________________________________ 40

legally certified time stamping services for the purpose of determining 

financial transaction sequences. The mechanism for distribution of the 

precise timing signals across the Internet is GPS. As e-commerce and etrading expand in the U.S. and internationally, the importance of precise 

time stamping will continue to increase. 

2.2.4 Transportation 

Since GPS reached operational status in the early 1990s, its consistently 

high-quality performance and low cost of use have created dramatic 

changes in the civil and commercial transportation infrastructure. Two 

federal agencies, the U.S. Coast Guard and the Federal Aviation 

Administration (FAA), have both embraced GPS and have initiated 

programs to augment GPS accuracy. The Coast Guard initially began with a 

differential augmentation service to provide sub-10 meter accuracy using 

marine radio-beacons around the contiguous US coastline (Maine-Texas 

and California-Alaska), the Great Lakes and St. Lawrence Seaway, and the 

Mississippi and Missouri River watersheds. That service is now fully 

operational at an actual precision of 1-2 meters. The service has also been 

expanded to interior land applications in the last several years in a 

cooperative venture with the Federal Railroad Administration and the Air 

Force and called Nationwide Differential GPS (NDGPS). NDGPS is 

transmitting augmentation signals to provide one-meter accuracy to rail 

and other land users across the U.S. using Low Frequency signals from the 

obsolete AF Ground Wave Emergency Network which is being dismantled. 

This service was originally intended to support positive train control, but 

has service implications far beyond railways. 

At the same time, the FAA has implemented a multi-billion dollar 

program called the Wide-Area Augmentation System (WAAS) to increase 

the accuracy, reliability and availability of GPS-based services for aviation 

users by transmitting special augmentation signals over satellite 

communications links. The FAA has also begun a companion project called 

the Local Area Augmentation System (LAAS) wherein signals are 

transmitted in the area of an airport to aid instrument landings and ground 

operations. The WAAS is a model for international civil aviation ventures 

in Europe and Japan to provide seamless global augmentation to GPS. 

Japan is also planning a complementary space-based adjunct to GPS, 

transmitting civil GPS signals, called the Quazi-Zenith Satellite System 

(QZSS). The QZSS comprises a small number of satellites in an orbital 
 

_________________________________________ CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE

___________________________________________________________________________ 41

arrangement configured to increase the number of civil GPS signals over 

Japan to improve availability in dense urban areas. In addition to these 

activities, foreign differential GPS services, mostly (but not all) governmentsponsored, are widely available to serve a diverse range of positioning 

(Geographic Information Systems) and transportation needs. Together, 

these international activities reflect a growing commitment to satellite 

navigation services, and specifically to GPS. 

Though not directly related to transportation, another service called 

Global Differential GPS (GDGPS) uses a worldwide network of civil 

reference stations to develop differential GPS corrections. The GDGPS 

service was originally developed for NASA by the Jet Propulsion 

Laboratory and is now additionally offered through commercial vendors to 

enable precision agriculture. The GDGPS also provides a valuable source of 

monitoring information for civil GPS signals as will be addressed in Section 

3 of this report. 

A common thread through all this activity is that each represents an 

augmentation to the core service provided by the GPS satellites – and none 

will operate on its own without the presence of the basic GPS signals. In 

most cases, the augmentations serve as checks on the quality of the basic 

signals, but together, they will soon represent an absolutely critical 

component of transportation economy and public safety. 

2.2.5 Emergency Services 

Closely related to GPS contributions to both communications and 

transportation are its contributions to the emergency services infrastructure 

of police, fire, and ambulance providers and other emergency responders. 

Use of GPS is growing significantly among regional ambulance providers as 

a means of managing fleets of emergency vehicles. As its use increases in 

automobiles, it is becoming a significant factor in E-911-type situations, 

where emergency vehicles are dispatched to accident locations by activation 

of a GPS location keyed to activation of an air bag. Further, GPS-derived 

positions are now being included in planning for E-911 capabilities required 

by legislation from cellular telephone service providers. GPS has also 

proven its value to fire departments operating in devastated parts of the 

California hills after the Oakland fire of several years ago, to the diverse 
 

CHAPTER 2. GPS ROLE IN MILITARY MISSIONS 

AND THE NATIONAL INFRASTRUCTURE________________________________________________ 

_________________________________________________________________________ 42

government emergency response teams dealing with the aftermath of 

hurricanes in the Southeast and with flooding in the Midwest. GPS use is 

growing in this sector and its incorporation in E-911 situations and in 

improving spatial interoperability among multi-jurisdictional response 

organizations will increase its importance in the future. Those 

improvements would be hastened even more by Federal Government 

leadership in promoting education regarding GPS benefits and training in 

the uniform application of its services to all participants in emergency 

response at federal, State and local levels (see discussion on spatial 

uniformity – Appendix E). This type of institutionalized spatial 

coordination will be especially important to rapid and efficient response in 

the case of an unpredictable widespread disaster resulting from terrorist or 

other hostile activity involving biological agents or nuclear devices. 
CHAPTER 3. SYSTEM AND PROGRAM ISSUES ___________________________________________ 

_________________________________________________________________________ 43

CHAPTER 3. SYSTEM AND PROGRAM ISSUES

3.1 LACK OF BALANCE AMONG THE GPS SEGMENTS

As discussed in Section 1.2, GPS is comprised of three distinct, but 

closely related, segments. The space segment (satellites) provides the 

signals that are received and processed by the user segment, and the quality 

and content of the signals, as well as the health of the satellites, is 

maintained by the control segment. In order for the system to perform 

optimally and provide the best possible service to users, the capabilities of 

all three segments must evolve in synchronization. As new signal 

capabilities are added to new satellites, the capability to activate, monitor 

and operate those new signal capabilities must be designed, tested and 

incorporated into the operational control segment. This must be done such 

that the continuing operation of legacy services by the control segment is 

not degraded or affected in any way. At the same time, new user segment 

receivers/chipsets must be developed put into production and 

installed/integrated into user systems so they will be able to process and 

exploit the new signal capabilities when they are present in sufficient 

quantities in on-orbit satellites and they are activated and then declared 

operational by the control segment. 

While those factors were synchronized during the initial stages of GPS 

operation, the program is now out of balance in several respects and that 

threatens to delay availability of needed operational capabilities. The out of 

balance situation has occurred for a variety of reasons, primarily related to 

technical issues and funding. Since the satellites are the critical signal 

sources and even new satellites can be operated by the existing control 

segment to maintain legacy services, they have taken priority when 

technical problems arise that endanger future launch schedules. In some 

cases, those problems have required diversion of funding from the other 

segments, causing delays in their improvement and evolution. One 

operational capability that has been particularly affected has been antijamming performance, which requires both control and user segment 

improvements to take advantage of new satellite signals. Additionally, 

diversion of funding from user equipment development delays other 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 44

improvements in signal processing that can provide anti-jam improvements 

independent of new satellite signals. 

3.2 GPS SATELLITES & THE GPS CONSTELLATION

GPS satellites presently come in five vintages, Block II/IIA 

(manufactured by Rockwell), Block IIR/IIR-M (Lockheed-Martin – formerly 

GE) and Block IIF (Boeing – formerly Rockwell). As of 15 Apr 05, the 

current constellation is comprised of one Block II, fifteen Block IIA and 

twelve Block IIR satellites. Of the twenty-eight satellites on orbit, a 

significant number are operating in a single-string condition. Still in the 

pipeline are eight Block IIR satellites and nineteen Block IIF satellites. All 

Block II-vintage satellites carry a sensor payload set supporting the Nuclear 

Detonation (NUDET) Detection System, or NDS. The NDS payload was 

designed to detect and characterize NUDET bursts for the DoD and other 

agencies, and based on global coverage afforded by GPS, replaced similar 

sensors that had been performing this function on other systems. All Block 

II-class satellites also employ UHF crosslink antennas, used to transmit 

information around the GPS constellation. With the growth of UHF 

ground-based communications activity in recent years, signal interference 

on the crosslinks is becoming more prevalent, and future GPS satellites will 

adopt higher frequency crosslinks in spectrum bands protected for space-tospace use. The next generation GPS satellite intended to replace the Block II 

versions is a part of the GPS III overall system upgrade. 

3.2.1 Block IIR/IIR-M 

The Block IIR satellites duplicated the signal configuration of the Block 

II/IIA satellites and incorporated additional capabilities for extended 

operation and crosslink ranging. A total of twenty-one Block IIR satellites 

were procured via multi-year contract. One was destroyed on launch due 

to booster failure. Up to eight of the remaining twenty Block IIR satellites 

will be modified to add a second civil code (L2C) at the L2 frequency and a 

new military code (M-code) at both L1 and L2. The modification will also 

allow the ability (called flex power) to shift power between the M-code and 

the P(Y)-code for increased anti-jam protection. Flex power allows for a 

potential increase in P(Y)-code power by turning M-code off. Alternatively, 

turning off the P(Y)-code will only slightly increase M-code power, which 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 45

will likely not provide operational benefit because backward compatibility 

will be lost in that case. Despite this limitation, flex power represents a first 

significant step toward improving system anti-jam performance by 

providing a means to increase delivered power of the legacy P(Y)-code to 

the user. The modified satellites will be designated as Block IIR-M versions. 

The addition of new signals to the Block IIR satellites was a FY 01 budget 

action that had been pending since 1998 and was finally directed via OMB 

pass-back action. The first Block IIR-M satellite was to have been launched 

in 2003, and ten to twelve were originally considered for modification; 

however, decision delays and a subsequent problem with space qualified 

electronics that affected the entire satellite fleet pushed schedules out. The 

first Block IIR-M satellite is now scheduled for launch in 2005. The original 

unit cost of Block IIR satellites in quantity of twenty-one was on the order of 

$35-40 million. Unit cost of the eight upgraded Block IIR-M satellites will be 

about $70-75 million. 

3.2.2 Block IIF 

The first six Block IIF satellites were procured in FY97/98 as the first 

multi-year block of a 33-satellite buy. Subsequently, the Air Force decided 

not to exercise an option for the second multi-year buy of fifteen satellites 

but to procure the satellites via annual procurements of three satellites each. 

Since that decision, thirteen additional Block IIF satellites have been 

procured. Also, an FY02 budget action included funding to upgrade all 

Block IIF satellites by adding civil and military signals and flex power 

capability as on the Block IIR-M vehicles, and, in addition, a third civil 

signal designed for civil aviation use at a new frequency, L5 (1175.42 MHz). 

Originally scheduled for late 2005, the first Block IIF satellite launch is now 

planned in early 2007. The original unit cost of Block IIF satellites, 

predicated on the expected 33-satellite buy, was on the order of $30 million. 

Unit cost of the upgraded satellites is now in the range of $70-80 million. 

3.2.3 GPS III Satellite 

The GPS III satellite is still undergoing design by two contractor teams 

(led by Boeing and Lockheed-Martin/Spectrum Astro). Block III satellites 

will incorporate improved electronics, high data rate crosslinks (high 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 46

frequency/narrow beam) providing continuous contact among satellites, 

and a high power spot beam (“theater” size) for anti-jam improvement. The 

spot beam is intended to meet the JROC-endorsed anti-jam requirement for 

+20 dB signal strength improvement by providing additional power 

directly from the satellites in lieu of making substantial changes to user 

equipment antennas and processing technology. First launch for the GPS III 

satellite was originally planned for FY09 with fully populated constellation 

by 2016/17; however, go-ahead delays and funding shortages elsewhere in 

the program have delayed the first launch until at least FY13. 

The new capabilities, when added to the existing primary and secondary 

payloads, represent additional cost and weight for the GPS III satellites. 

Original GPS Block II-version satellites cost on the order of $30+ million. 

With improvements to signal structure and power (taking account of effects 

of sole source contracts and low quantities) Block IIR-M and Block IIF 

satellites now cost on the order of $60-80 million. Even at those prices, the 

Air Force has experienced difficulty in procuring sufficient satellites and 

medium-lift boosters to assure the 24-satellite constellation can be sustained 

at a high level of probability into the future. Block III satellites are 

anticipated to cost on the order of $100-150 million. Based on these 

projections, the Task Force considers it essential that the Air Force 

investigate alternatives to lower total constellation on-orbit costs. Such 

alternatives include deletion of secondary payloads with significant weight 

and power needs from some or all GPS satellites and operating a mix of 

spot-beam satellites and higher power earth coverage “utility” satellites 

with lower relative cost/complexity. 

The cost of the boosters to launch the various GPS configurations is a 

significant consideration as well. Currently, the Delta II booster used for 

remaining Block IIR and IIR-M satellites costs nearly $60 million, and the 

medium-lift Evolved Expendable Launch Vehicle (EELV) that will launch 

Block IIF satellites is projected to cost $65-70 million. GPS III is 

programmed for the medium EELV as well, and the Task Force strongly 

recommends that GPS III weight be tightly managed to enable two satellites 

to be launched on a single booster. Achieving dual-launch capability using 

a medium EELV, or even an intermediate EELV (projected cost $90-95 

million) will dramatically lower on-orbit costs for the GPS III constellation 

compared to a single satellite launch strategy. 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 47

3.2.4 GPS Satellite Constellation

Based on the forgoing, the current schedule and future investment plan 

for GPS involves significant risk of sustaining sufficient satellites for a full 

constellation. The current on-orbit inventory is 28 satellites; however, with 

expected failures, the AF Space Command December 2004 PNT Functional 

Availability Report reflects a nominal probability between 5 – 20 percent 

and a worst-case probability between 20-40 percent that the constellation 

will fall to fewer than 24 satellites in the 2007-2012 period based on current 

satellite replacement schedules. 

The Air Force has committed for the long term to maintaining only a 24 

satellite constellation. While this may be satisfactory for aviation and openocean maritime missions, the Task Force does not consider it sufficient to 

support missions in confined urban areas and mountainous regions of the 

world. The nominal 24-satellite constellation only ensures consistent foursatellite coverage with mask angles (angle to horizon which cuts off GPS 

reception) above five degrees elevation, a value the Task Force finds to be 

inadequate for surface operations. For missions involving land operations, 

assuring availability of four satellites above a fifteen-degree mask angle will 

provide adequate signals to support operations in urban and mountainous 

areas. To achieve at least four satellite coverage above fifteen degrees 

elevation requires at least a thirty satellite constellation. The Task Force 

considers this to be vitally important to obtaining the broadest military 

utility from GPS for future operations and a major factor in system design 

decisions for GPS III. 

Considerations for 30-satellite GPS III constellation configurations 

include adding one satellite to each of the existing six planes or changing 

the constellation to a three-plane configuration with ten satellites per plane. 

The Task Force is aware that many studies have been performed and 

computer simulations conducted relative to GPS constellation design over 

the past three decades. While the studies show relative strengths and 

weaknesses for both three- and six-plane configurations, on balance, the 

Task Force consensus is that a three-plane constellation is the more effective 

design. Further, if GPS III satellite weight can be constrained to permit two 

satellites at a time to be launched on a medium-lift booster, the three plane 

configuration will be more economical to sustain than six-planes. Recall 

from Section 1.2 that the original GPS constellation design was a three-plane 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 48

configuration; the six plane design was only adopted when the satellite 

count dropped to 18 and coverage had to be spread more thinly. 

3.3 SYSTEM OPERATIONS, SIGNAL MONITORING AND 

PERFORMANCE ASSESSMENT

3.3.1 System Operations 

The GPS Operational Control Segment (OCS) consists of a softwareintensive Master Control Station (MCS) at Schriever AFB, CO connected to a 

global network of six monitor stations (Schriever, Cape Canaveral, Hawaii, 

Kwajalein Atoll, Diego Garcia and Ascension Is.) and uplink antennas at 

Kwajalein, Diego Garcia, Ascension Is. and Cape Canaveral. Additional 

antennas can be used if necessary, though access for GPS use must be 

separately scheduled. The MCS is operated by the Air Force 2nd Satellite 

Operations Squadron (2SOPS). Monitor stations are unmanned and 

maintained by contractor personnel. With Air Force acquisition attention in 

recent years focused on GPS satellites and signal structure, the Task force 

believes the control segment has been seriously neglected. 

As the system was becoming operational in 1993-1995, delays in control 

segment software deliveries (IBM Federal Systems – Loral – LockheedMartin) began to be a problem. Since that time, the problems have been 

sporadically addressed but never really solved. The Block IIF contract 

placed responsibility for both the Block IIF space segment and control 

segment under the prime; however delivery delays continued, and 

coordination between BlockII/IIR and Block IIF software was an additional 

problem. A further change of contractor responsibility called the Single 

Prime Initiative was supposed to bring improvement, but it was 

accompanied by additional software delivery segmentation and capability 

deferrals – necessary to maintain baseline system performance. The control 

segment currently operates with a combination of Commercial Off-TheShelf (COTS) and uniquely modified COTS products that are minimally 

adequate for maintaining system integrity. 

In addition to the chronic software problems, Air Force Space Command 

has routinely deferred equipment maintenance and modernization of the 

monitor stations and ground antennas. As of today, the control segment is 

operating the GPS constellation of Block IIA and Block IIR satellites 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 49

basically as Block IIA satellites. Activations of improved signal processing 

capabilities already in space in the baseline Block IIR satellites have been 

deferred for up to 7 years, and attention is focused on delivery and test of 

operational software necessary to minimally operate the new versions of 

Block IIR-M and Block IIF that will be in space beginning in 2005 and 2007, 

respectively. 

Over the last several months, funding shortages have forced the Air 

Force to terminate work already on contract for Versions 6.0 and 6.1 of OCS 

software. These software versions are necessary to permit operation of all 

the new signals being launched on Block IIR-M and Block IIF satellites. 

Version 6.0 allows operational control of L2C and L5, and Version 6.1 

allows operational control of the military M-Code. Version 6.0 was also 

intended to implement the flex-power initiative and permit power shifting 

among the available signals as dictated by operational priorities. Delivery 

of both versions had recently slipped to 2009 and 2010, respectively, and 

new delivery dates are now forecast in 2010-2011. With termination of 

those elements of control software from the current contract, the Task Force 

considers it essential that new signals be activated on launch of each Block 

IIR-M and Block IIF satellite and made available at the users’ risk for testing 

and other applications, even if they cannot be declared operational until 

some time in the future. 

Based on this history of chronic problems, the intent of the GPS III effort 

is to replace rather than upgrade the existing control infrastructure. 

However, even when GPS III satellites eventually begin to replace the Block 

II versions, experience indicates that legacy satellites will likely require 

operational support well beyond 2020. 

The ability of the control segment to absorb further new requirements 

and implement additional operational changes is non-existent within 

current resources. The Task Force believes new approaches are necessary as 

soon as possible to enable consistent and timely operation of improved inspace capabilities. In this regard, the Air Force should also reevaluate the 

practice of a totally blue-suit operation at the MCS. Outsourcing of part of 

the operations mission or insertion of selected contractor support personnel 

could both aid in long-term operations continuity as well as in supporting 

consistent operation of new signal capabilities in advance of a “fully 

operational” declaration. 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 50

3.3.2 Monitoring and Performance Assessment 

3.3.2.1 DoD Monitoring Networks 

The MCS receives continuous information regarding GPS military signal 

fidelity through a global network of six dedicated monitor stations, 

identified above. Each monitor station receives the Y-Code signals from 

whichever satellites are in view, and most of the constellation is in view of 

at least one monitor station at all times. The exception is that satellites 

whose orbits take them below the equator in the eastern South Pacific may 

be out of view by any monitor station or uplink antenna for 20 minutes or 

more. An initiative was undertaken in 1995 to mitigate this situation by 

incorporating data from monitor stations operated by the National 

Geospatial-Intelligence Agency (NGA) at locations that would fill the gap 

and augment other observations. However, funding for this effort, called 

the Accuracy Improvement Initiative (AII), was insufficient to integrate the 

NGA data into MCS software until this year when data from an initial six 

NGA stations will be incorporated. Data from five more NGS stations is 

planned to be incorporated in 2006 (Figure 3). 

Figure 3. DoD Monitor Stations 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 51

3.3.2.2 Civil Monitoring Networks 

In addition to monitor stations operated by the DoD, there are separate 

regional and global networks of civil signal (C/A-Code) monitor stations 

operated by government and scientific organizations. Global networks 

include the Global Differential GPS (GDGPS) System and the International 

GPS Service (IGS). 

The GDGPS is operated by the Jet Propulsion Laboratory (JPL) with 

funding from NASA and others and gathers data from over 60 worldwide 

monitoring stations (see Figure 4). Raw data from the GDGPS provide the 

basis for a value-added commercial differential GPS service called 

GreenStar, offered by John Deere and furnishing high precision GPS 

augmentation for precision farming. The GDGPS System is completely 

independent of the GPS OCS infrastructure, thus increasing the probability 

of detecting an anomaly. The system has demonstrated extremely high 

reliability since its inception in early 2000. An integrity monitoring 

prototype based on the GDGPS System was developed in collaboration 

between JPL and the Aerospace Corporation, and was launched in May 

2003. It provides secure internet access to authorized users, including 

2SOPS operators from the MCS floor as well as from their homes. The 

developers at NASA/JPL and Aerospace are now in the process of 

implementing end-to-end secure data authentication, and automated alarms 

with 4 second latency. Feedback from the MCS indicates that the system is 

a very valuable tool. 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 52

Figure 4. 62-Station GDGPS Reference Network 

The IGS was established by the International Association of Geodesy 

and includes over 350 monitoring stations and ten analysis centers operated 

by various national and scientific geodetic organizations around the world 

(see Figure 5). NASA funds the coordinating office for this organization, 

called the Central Bureau and also located at the JPL. The IGS maintains 

over a decade of data and products from its global network. Resulting 

products are the most accurate and precise available. The IGS is often 

contacted after the fact for information on anomalies or failures, but this 

arrangement is very ad hoc. 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 53

Figure 5. IGS Network - 2004 

Historically, the practice of the Air Force to use ‘trusted data sources 

only’ has led to the dismissal of monitoring information from civilian 

sources because the integrity and fidelity of each individual source could 

not be continuously verified, and intentional errors could be introduced that 

would corrupt the process. However, given the fact that it has taken years 

for integration of the NGA station network and data into the OCS, the Task 

Force recommends the Air Force reevaluate this ‘trusted source’ practice for 

the added value such independent performance measurements could bring 

to GPS operations in addition to data from the 16 DoD stations. The Task 

Force recognized that such additional information would require special 

measures to assure its integrity and that a point of diminishing returns 

would likely apply as additional data is added; however, on balance, we 

believe the Air Force should actively seek to gain as much value as possible 

from these available resources. Further, even if the trusted resource argument 

does not allow the use of these additional monitor units in the upload calculations, 

they should be used as part of an overall performance monitoring capability.

3.3.2.3 Performance Assessment 

Assessing the performance of a satellite or satellite system necessitates 

detailed requirements for collection of measurement data, functional 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 54

requirements for system operation, and measurable performance 

parameters which provide the framework for monitor and control. Given 

the availability of monitoring stations and measurement data, it is also 

necessary to maintain performance standards against which to measure 

results. Such a performance standard has been in place for many years for 

the civil Standard Positioning Service (SPS). It was originally authored by 

AF Space Command and approved by the ASD(C3I) in the early 1990’s as 

the SPS Signal Specification, and has since been revised and reissued under 

the auspices of the GPS Joint Program Office (JPO) as the SPS Performance 

Standard. This standard provides measurement metrics for a globally 

averaged signal in space for civil applications. However, it is important to 

note that the GPS OCS does not collect SPS measurement data through the 

GPS or NGA monitor stations for assessing SPS performance against this 

standard. The OCS does monitor the military Precise Positioning Service 

(PPS) signals and measure their performance against satellite transmission 

and PPS accuracy specifications; however there is not at present a global 

PPS performance standard equivalent to the SPS standard. The Task Force 

recommends that consistent capabilities for performance measurement and 

assessment be established covering both the SPS and PPS. Development 

and maintenance of SPS and PPS standards for such performance 

assessment in the future should be the responsibility of the operational 

organizations representing GPS users, and we recommend STRATCOM as 

the organization to oversee those activities as part of its GPS stewardship 

responsibilities on behalf of the DoD. 

3.4 USER EQUIPMENT & IMPROVEMENTS IN ANTI-JAM 

PERFORMANCE 

3.4.1 Military GPS User Equipment 

Military GPS user equipment has steadily evolved since the first family 

of operational equipment, classified when keyed, was approved for 

production in the late 1980’s. During the 1980’s and early 1990’s the GPS 

JPO was the principal source of receiver development and platform 

integration activity in the DoD. Over the last decade, however, the JPO has 

de-emphasized its role in development, and even more so in production, of 

user equipment for diverse DoD applications. The evolutionary path for 

GPS user equipment has been on a track from box to card to module form 

with emphasis on standard interfaces and decentralized procurements. The 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 55

Selective Availability/Anti-Spoofing Module (SAASM), conceived in the 

early 1990’s, was intended to replace previous classified hardware receivers 

and PPS Security Module/Auxiliary Output Chip (PPS-SM/AOC) 

components in more affordable and standardized packages. However, 

funding shortages and changing production requirements delayed 

availability of working SAASM designs for several years. Currently 

SAASM is required in all new GPS equipment fielded after 1 October 2006. 

Legacy applications (PPS-SM/AOC) are required to be part of a roadmap 

for SAASM transition in order to continue to receive GPS JPO procurement 

support after that date. 

To date SAASM has been seen as expensive and power-hungry to some; 

however, production and cost data presented to the Task Force did not 

indicate SAASM costs to be excessive. There is strong Service resistance to 

SAASM in some quarters, and many believed initially there were readily 

available software-based solutions that would meet any reasonable threat 

and that would be much more affordable. However, subsequent and 

intensive discussions between the GPS JPO and Joint Tactical Radio System 

(JTRS) designers identified significant limitations in current software-based 

technology related to both GPS security requirements and software-based 

processing capacity that do not make that technology appealing for military 

GPS implementations in the near term. 

As presently envisioned, SAASM is a receiver implementation for legacy 

military signals only. The new M-code that will appear in space with the 

first Block IIR-M launch this year will involve a different security 

implementation, incorporating Protection of Navigation (PRONAV) 

features that are part of a new Information Assurance (IA) architecture (see 

Section 3.5). Original plans were to develop and deploy M-code only 

receivers and to retire legacy receivers that utilized the C/A- and P(Y)-

Codes. However, because of cost and synchronization issues, those plans 

were modified to first develop and deploy user equipment capable of 

receiving legacy signals (P(Y) and C/A) as well as the new M-Code. These 

new equipment items are termed YMCA receivers. A two-phase 

development effort is now underway at the JPO that will result in 

production-ready versions of two YMCA receiver form factors, one for 

aviation use and one for ground applications. The JPO will not take those 

receivers to production, however. The Services will be expected to 

individually procure YMCA cards to meet their requirements for upgraded 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 56

GPS receivers. The Task Force is concerned that, even though the M-Code 

signals will be present in space beginning in 2005, current user equipment 

development and production schedules will not produce the productionready YMCA receiver cards until early 2009, and actual production and 

installation of the improved GPS equipment could take much longer. 

In the fifteen-plus years that Service advisory boards and the DSB have 

been looking into GPS vulnerability, GPS user equipment has been 

recognized as providing the quickest path to system robustness. In 

comparison to satellites, user equipment is accessible, capable of rapid 

modification (antennas, processing technology, etc.), and more flexible from 

a signal-jammer geometry standpoint. Though increased power from space 

is important as well, satellite-only solutions are hampered by long lead 

times and signal power disadvantages that favor the jammer. However, for 

the last several years most of the attention and money allocated to 

improving GPS robustness has been devoted to signal structure and 

satellites. Unfortunately, full availability of such satellites cannot be 

expected prior to 2018 at the earliest, and budget pressures could reduce the 

number of satellites deployed. For many users this would have the same 

effect as jamming, as fewer satellites limit availability of signals to users 

whose missions require operations in locations where signal reception is 

masked by terrain or buildings. 

3.4.2 Military Anti-jam Capability 

The ability for our military forces to be able to navigate and determine 

positions in the presence of hostile jamming is essential. The principal 

vulnerability to be addressed is the threat of widely proliferated, mobile, 

inexpensive, relatively low-power jammers. The optimal configuration for 

such jammers is in an extensive array, in which the jammers blink on and 

off. Worldwide, we can foresee GPS jammers available in the 100 Watt size. 

This size jammer is relatively easy to manufacture and can be widely 

proliferated. 

While we have demonstrated the technology to cope with distributed 

fields of jammers of this size, we have not put in place a program to field 

this user equipment on a reasonable scale. It has been shown to be costprohibitive and impractical for scheduling reasons to contemplate DoD or 

Service-wide replacement of GPS user equipment. However, it is not 

impractical to consider installation of more sophisticated anti-jam GPS 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 57

receivers on selected platforms with critical, high precision missions. The 

best technique for GPS user equipment to defeat such jammers is to employ 

beam steering antennas. GPS research efforts have successfully developed 

prototypes. This technology is readily available to be incorporated into 

YMCA production equipment by 2008. 

This Task Force supports an anti-jam strategy designed to steadily force 

adversaries to increase the required offensive jamming power needed to 

attack the navigation and timing service so that: 

 It will be more expensive and more difficult to attack 

improved GPS receivers with a proliferation of relatively 

cheap and low-power jammers. 

 The higher power jammers will be easier to locate and 

attack. 

 Full visibility of this strategy as announced and executed 

will deter some from wasting their resources on jamming 

capabilities. 

We are concerned, however that the current program will not provide 

significant anti-jam operating capabilities in the field for approximately 15 

years. 

The chart at Figure 6 demonstrates the trade between anti-jam capability 

(expressed in dB), jammer power, and effective jammer range. Current 

military GPS user equipment is expected to be jammed at ranges of 5 to 50 

kilometers by a 10-watt jammer. In fact, Army ground users are seeking to 

use civil GPS equipment that will be jammed at far greater ranges by the 

same 10-watt jammer. 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 58

Current Installed Capabilities Current Installed Capabilities

RANGE TO JAMMER (km)

GPS RECEIVER ANTIJAM CAPABILITY (dB)

1 6 7 8 9 10 2 3 45

100

90

80

70

50

40

30

20

10

0

60

JAMMER ERP = 0.1 mW

1 mW

10 mW

100 mW

1 W

10 W

100 W

1 kW

10 kW

Req.

Range of 10 

Watt Jammer 

is 5 to 50 

kilometers

Range of current

A/J capabilities

Figure 6. Current Capabilities 

A reasonable expectation is that future conflicts will encounter 

distributed and possibly mobile jammers of 100 watts or more. We 

therefore believe that the requirement for user equipment jamming 

resistance should, as a minimum, be set at 90dB. This would provide a 

minimum acceptable level of protection for users who can be expected to 

operate in the range of enemy jammers. As can be seen (Figure 7) this 

would render 1 kilowatt jammers ineffective beyond a range of 3 

kilometers. 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 59

Effect of 90 dB Capability Effect of 90 dB Capability

RANGE TO JAMMER (km)

GPS RECEIVER ANTIJAM CAPABILITY (dB)

1 6 7 8 9 10 2 3 45

100

90

80

70

50

40

30

20

10

0

60

JAMMER ERP = 0.1 mW

1 mW

10 mW

100 mW

1 W

10 W

100 W

1 kW

10 kW

Req.

Range of 1 kW 

Jammer is 

less than 3 

kilometers

Range of 1 kW 

Jammer is 

less than 3 

kilometers

Figure 7. Improvements Possible 

3.4.2.1 User Equipment 

User equipment improvements can be brought on line years earlier than 

any satellite improvements (though the contributions of flex power (section 

3.2.1) and subsequent increases in transmitted power from the satellites 

remain important). As mentioned, many of these improvements have 

already been conceived and demonstrated. As a first step, implementation 

of YMCA receivers will facilitate the initial transition to the new, more 

robust military signal structure. Jam resistance is the most important goal 

of the possible improvements. Improved Jam resistance will provide 

assured availability of GPS for the many precision operations that are 

required by our modern armed forces. Done properly, these capabilities 

will defeat the effects of enemy jammers. Potential improvements are both 

long term (where a steady investment in R&D is essential), and short term 

(ready for procurement and operation in the next few years). The Task 

Force believes the DoD should vigorously support these improvements 

with both budget and direction. Our recommendations include the 

following specific examples: 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 60

Near Term (immediate and next several years) 

 Integrated, Network-Capable receivers that ensure host 

systems can hand off both time and position to GPSequipped munitions. An example is the F-16 host handing 

off four-dimensional coordinates to Joint Direct Attack 

Munitions. This will allow faster acquisition, more 

accurate positions, and greater ability to operate under 

hostile jamming operations. There are many more 

examples, especially for Army users where rapid 

acquisition will help reduce power and improve 

responsiveness. 

 “All-in-view” receivers that will lock on and use all 

satellites that are not masked. This will improve accuracy, 

integrity and availability. 

Medium Term (3 to 5 years) 

 GPS receivers should be designed to receive all GPS 

signals, both civil and military.

 Deep integration with inertial components that will 

significantly increase resistance to jamming as well as 

improve system accuracy during periods when the GPS 

receiver is being jammed.

 Inexpensive beam-steering antennas can provide very 

significant improvements in jam resistance. Faster and 

cheaper digital electronics will make these devices more 

inexpensive and hence more appealing to the high-volume 

military users.

 Smart all-in-view receivers can adaptively process all GPS 

signals and reject or attenuate any that are degraded or 

jammed.

Longer Term (5 to 10 years) 

 Chip Scale Atomic Clocks that will allow better knowledge 

of time during acquisition and hence make initial 

acquisition faster and more reliable. These small, low-
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 61

power clocks will also provide better short-term accuracy. 

In turn, when coupled with the new Lm signal, the shortterm clock accuracy will allow more averaging, and hence 

more jamming resistance. 

3.4.2.2 Satellite Spot-Beam 

 

 The principal DoD plan to reduce GPS jamming vulnerability is to 

increase satellite power for GPS military signals, and in particular for the 

next generation signal called the M-Code. The GPS III plan involves a large, 

high-gain antenna added to the normal earth-coverage antenna. This may 

be a deployable reflector antenna or a phased-array antenna; the contractor 

and the particular mechanization have not yet been selected. The large 

antenna can produce a factor of one hundred or higher signal strength in a 

limited region or “spot” on the earth at least 1000 kilometers in diameter. 

All M-Code GPS receivers in this “+ 20 dB spot” would benefit from the 

increased signal power. The current plan would achieve a full constellation 

in the CY2019 era if no further delays occur. 

 The Task Force notes the following advantages and concerns with 

the GPS III spot-beam approach: 

Advantages 

 All authorized, M-code GPS users in an area of conflict 

benefit from the substantially increased signal power 

density. 

 This GPS system enhancement involves only one major 

program versus the need to deal with a multiplicity of GPS 

individual programs which would be necessary in order to 

upgrade operational military GPS receivers 

Concerns 

 The GPS III schedule is long and likely to get even longer 

leaving an unacceptably long window of vulnerability for 

GPS users if spot-beam is the only option to improve antijam performance. 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 62

 The complexity and cost of the GPS III satellite is likely to 

grow due to the inevitable growth in “requirements”. 

 The weight of the satellites may grow such that two 

satellites cannot be launched on a single medium-lift 

booster, dramatically escalating constellation sustainment 

costs. 

 The 1000 km diameter spot may be too small to cover 

major areas of conflict. 

3.4.2.3 Augmenting the Spot-Beam 

 The actual size of the spot beam on the earth has not yet been 

finalized. There are tradeoffs between spot size (antenna gain) and radiated 

RF power. A “fatter” beam with a larger spot on the earth would alleviate 

the coverage concern and it is a configuration to consider in the GPS III 

system tradeoffs. 

 However, the main concern identified by the Task Force is the 

extended schedule for GPS III and its included spot beam approach. The 

long window of jamming vulnerability must be addressed by some 

augmentation, and the best way to do this is to upgrade individual GPS 

receivers with anti-jam enhancements, some of which are noted above. 

Such techniques are available today and they can be installed in a few years. 

The timing is propitious because weapon system managers will soon begin 

a major change-out of their receivers to accommodate the M-Code signal. 

One concern noted above is the cost of upgrading on the order of a million 

military receivers. However, most military receivers are in munitions and it 

is not necessary, for example, to upgrade all of the 230,000 Joint Direct 

Attack Munitions (JDAMs) being planned. Rather, the Task Force 

recommends upgrading 50,000 JDAMs to provide an inventory of “silverbullet” munitions to use in the event jamming is encountered. Such an 

upgrade of selected military GPS receivers could cost in the vicinity of $1 

billion as detailed in Appendix F. This is a significant cost but not 

exceedingly high in the context of major GPS satellite upgrades. 

The Task Force concludes that the risk in the GPS III program is real and 

its extended procurement schedule leaves an intolerable window of 

jamming vulnerability. These concerns can be addressed by an approach 

that improves military receivers in the near term as the GPS-III program 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 63

proceeds. Adding anti-jam enhancements to individual receivers will 

buffer the overall program by providing critical early anti-jam capability, a 

risk reduction function, and a backup if the GPS III program is further 

delayed or fails to survive. Over the long term with some form of GPS III 

“spot” online and the individual receiver enhancements recommended 

above, the 40 to 60 dB of additional anti-jam capability will make GPS 

jamming a relatively hopeless tactic for an enemy. 

3.5 SECURITY POLICY – PROTECTION & EXCLUSIVITY

GPS has been described as “like air on the battlefield.” However, unlike 

air, current GPS services are not available equally to everyone on the 

battlefield. Military GPS signals, the Precise Positioning Service or PPS, are 

intended for the exclusive use of U.S. and allied/friendly forces. They are 

intended to be receivable by only those forces for joint interoperability and 

also to be the only signals that remain available should the generally 

available civil equivalent services be denied by navigation warfare 

(Navwar) measures in a theater of conflict. Most importantly, they 

currently provide up to 100 times more resistance to interference than do 

the civil GPS signals, and with planned improvements, will provide 1,000 to 

10,000 times more resistance in the future. Maintaining this asymmetric 

advantage in position, movement and timing over an adversary requires 

access to exclusive frequency spectrum and use of signal processing, 

encryption and physical protection measures that make military GPS 

receivers appear more complex and costly than comparable civilian 

receivers. The concept of exclusivity has underpinned GPS system and 

signal design and security policy decisions for the last two decades. A 

critical element of that security policy, navigation warfare (Navwar), is a set 

of strategies and capabilities designed to preserve the asymmetric 

advantage afforded by GPS in the battlespace. Exclusive access to a military 

GPS signal set is one of the central tenets of Navwar, whose importance to 

the DoD and to national security has been emphasized over the past year in 

Deputy Secretary of Defense direction and in the recent GPS national policy 

directive signed by the President. 

The next generation military GPS signal, called M-Code, will 

significantly improve exclusivity of access because, in addition to being 

encrypted, it will be spectrally separate from civilian signals. The M-Code 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 64

will permit higher power operation than the present signal design and will 

facilitate localized tactical denial of GPS civil signals to prevent their use by 

hostile forces. As described in the Section 3.4, military GPS receivers, when 

tracking the encrypted military signals, are much more resistant to 

interference than commercial GPS equipment. Many platforms also employ 

adaptive nulling antennas to deal with jamming. The newest generation of 

military GPS receivers that can access military GPS signals directly are even 

more resistant to interference; however, future improvements in signal 

availability and receiver performance (i.e., advanced processing, digital 

beam forming antennas) will continue to be necessary, as supported by our 

recommendations. 

These new military GPS receivers will operate under an equally new 

security paradigm known as Protection of Navigation (PRONAV). 

PRONAV is being implemented by the GPS JPO to incorporate concepts of 

Information Assurance (IA) and receiver performance to address the two 

central components of GPS IA, military integrity and military exclusivity. 

Military integrity assures that authorized users can access and utilize the 

authentic modernized GPS signal-in-space in all environments for which 

the system has been specified to provide position, velocity and timing 

service integrity monitoring. As described above, military exclusivity 

protects against unauthorized exploitation and assures that the authentic 

modernized military GPS signal-in-space is exploited only by authorized 

users. PRONAV does not replace former techniques such as encryption or 

use of tamper resistant technology, but expands on the options for service 

integrity and fidelity that are available to GPS operators and users and 

provides for more flexible implementations according to mission-specific IA 

requirements. Improvements to GPS functionality resulting from PRONAV 

are shown in Figure 8. 
 

___________________________________________ CHAPTER 3. SYSTEM AND PROGRAM ISSUES

___________________________________________________________________________ 65

Figure 8. Comparison of GPS Performance in COMSEC vs. PRONAV Architecture 

(Scale 1 – 7, 1 is the lowest level of assurance, 7 is highest) 

In this environment, the pending advent of new civil signals, in 

combination with military performance improvements described, presents 

opportunities for more diverse signal reception strategies that may increase 

service robustness in many situations. The Task Force does not recommend 

abandoning exclusivity or the capabilities afforded by Navwar. However, 

the Task Force considers the rigid application of exclusivity to be 

constraining to potential signal reception benefits that can result from the 

future diverse signal mix. Consequently, the Task Force recommends 

adjustments to current GPS receiver acquisition policies to permit more 

flexible procurement of GPS user equipment within approved military 

mission Information Assurance parameters. The Task Force also 

recommends including increased signal flexibility in the satellites to permit 

operational choices with regard to exclusivity in the longer run. One 

decision that the Task Force considers essential to improving opportunities 

for future flexibility in GPS satellites and user equipment is to permanently 

eliminate the requirement for Selective Availability and to delete the 

Requirements* GPS COMSEC PRONAV (IA)

Monitoring/Termination 5 5

Key Loading 5 6

Zeroization 5 7

Self-Checks 5 5

Fail-Safe Design Features 5 6

Anti-Tamper/Reverse Engineering 5 5

Availability - J/S 1 6

Availability Blue Force Jamming 1 5

Data Integrity 5 7

Signal Integrity 1 6

Reasonableness 1 5

Consistency 1 5

External Aiding 1 5

Authentication 5 7

Cryptography 

Navigationspecific IA 

Features 
 

CHAPTER 3. SYSTEM AND PROGRAM ISSUES ____________________________________________ 

_________________________________________________________________________ 66

hardware and software overhead for its implementation from throughout 

the system. 

.
CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT _____________________ 

________________________________________________________________________ 67

 

CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL 

MANAGEMENT

4.1 GPS AND THE GLOBAL MARKETPLACE

In many ways, GPS is analogous to autos and horse-drawn carriages or 

to calculators and slide rules. However, in those cases, evolving marketdriven product lines provided steadily increasing functionality over 

previous alternatives. Acceptance in the marketplace was achieved and 

replacement and upgrade decisions for users was encouraged because 

awareness of value had been well-established through advertising and 

improvements were both marketed by manufacturers and sought by 

customers. GPS, on the other hand, offers multi-use applications derived 

by diverse users from a set of radio signals provided by the government 

for national security and as a public good. The applications create a 

market of national security and civil/commercial/scientific capabilities; 

however, broad market awareness is lacking, and application evolution is 

constrained for both domains by the willingness and ability of the 

government to improve or add to the signal set. The continued 

availability and improvement of that signal set are subject to annual 

budgetary decisions at several levels among different government 

agencies and from various committees of the Congress. At the same time, 

however, efficiencies in positioning, movement and timing derived from 

the ubiquitous GPS signals have already quietly permeated virtually 

every level of our national infrastructures to the extent that, in many 

cases, there is no going back to earlier ways of doing things without 

tremendous but unrecognized penalties. All of the domains, missions and 

infrastructure components addressed by this Task Force are already 

affected to a greater or lesser degree by this dependency, and we believe 

the effects will only become more pronounced over time. The dilemma 

that results is peculiar to GPS. Our widespread dependency on it 

demands strong advocacy by military and civilian leaders for its 

continued evolution and improvement. However, the executive and 

legislative environment where such decisions must be made is skeptical of 

advocacy, absent a strong message from the market (operational users), 
 

CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT _____________________ 

_________________________________________________________________________ 68

and so such decisions are delayed because of fiscal constraints and 

competing priorities. This situation is a direct result of institutional 

decisions regarding GPS operation and governance that guided its 

original design and implementation. However, now that GPS has become 

operational and has established dependencies because of its value, the 

structures created for its initial implementation should be reassessed. The 

internal conflicts affecting GPS in the national security arena and global 

marketplace must be understood and mitigated by government leaders 

responsible for GPS at all levels because those decisions have real and farranging effects for our national security and economic competitiveness. 

4.2 ADVENT OF EUROPEAN UNION’S GALILEO

Since the inception of GPS, the civil and commercial sectors as well as 

the international community have been uneasy about an apparent military 

dominance in GPS decisions. Even though Secretaries of Defense and 

Transportation, the President, and the Congress have produced policies 

and legislation emphasizing multi-agency management of GPS and its 

multi-use applications, the fact remains that GPS is primarily financed by 

the Department of Defense and is a critical component of U.S. National 

Military Strategy. That reality underlies the perception that the U.S. 

military could “take away” GPS from other users at any time, and enables 

detractors of GPS to create the misimpression that the U.S. or the military 

would do so arbitrarily. In this climate, the emergence of Galileo, a 

system similar to GPS planned by the European Union (EU), has created 

motivation for a reevaluation of U.S. policies and practices with regard to 

GPS. Fundamental to these are the organization and governance 

structures by which the U.S. manages and operates GPS as a “national” 

program and as part of a “national and international” PNT infrastructure. 

The Europeans have offered both security and economic reasons to 

justify creation of a Galileo system in parallel with GPS. One 

fundamental reason advanced is concern over European dependence on 

an infrastructure critical to their society that is totally controlled by the 

United States. In that context, European entry into this arena has changed 

the world’s perspective on the composition of a global PNT system. 

Clearly the Europeans intend to operate Galileo as a revenue generating 

enterprise, and its projected business models for both civil and military 

applications may impact the use of GPS internationally. Galileo’s 
 

_____________________ CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT

___________________________________________________________________________ 69

eventual role as a potential European counterpart or competitor to GPS 

has yet to become apparent, but even at this stage of its development it 

heightens the importance of evolving GPS civil performance. In the 

military arena, an initiative is also underway to take up possible joint use 

of GPS and Galileo among the NATO partners. With that being said, it is 

too early to project how Galileo will be implemented, and the EU still has 

not yet fully established the financing necessary to bring it into 

sustainable operation. 

The June 2004 U.S.-EU agreement on GPS/Galileo cooperation is 

encouraging in that it appears to have resolved several technical 

compatibility issues and establishes an environment for further 

cooperation. Diverse perceptions that arose during negotiation of the 

agreement regarding comparability of service between the two systems 

remain to be resolved as cooperative discussions proceed under the 

agreement. Even with the agreement in place, uncertainty remains 

regarding the eventual form Galileo will take as well as regarding 

European resolve to bring it into full operation. In this context, the 

recently signed Presidential directive establishes as a goal that U.S.-

provided civil GPS services and augmentations remain competitive with 

foreign civil systems. If/when Galileo is fully operational, its additional 

satellites should increase signal availability and overall system integrity 

for dual mode GPS-Galileo receivers. This should be particularly useful 

for users in urban “canyons” and other obstructed areas. In more open 

environments a single receiver may see sufficient satellites to enable signal 

integrity verification within the receiver itself. The cooperative 

discussions now envisioned with the EU should have such improvements 

as an objective. 

All of these issues compel the U.S. to take a proactive role with Europe 

and the rest of the world to assure a favorable outcome that protects U.S. 

goals and objectives for GPS while contributing positively to our 

international relationships. While it is useful for extending dialog on 

mutual technical interests, the 2004 Agreement does not provide a 

mechanism to achieve this outcome. 
 

CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT _____________________ 

_________________________________________________________________________ 70

4.3 NATIONAL GOVERNANCE OF GPS AND THE PNT

INFRASTRUCTURE

GPS has become a truly “national” program of critical importance to 

essentially all aspects of U.S. life and well beyond the scope of any single 

Department. However, the burden of justifying the capabilities 

appropriate for GPS and the resources to implement those capabilities has 

historically fallen on the DoD, which has an easily identifiable worldwide 

need for the system. Civil, commercial and scientific users around the 

world who are now dependent on GPS are not institutionally organized to 

justify and pay for any system characteristics peculiar to their needs that 

exceed those of the military. Further, to date, there has been no 

institutional mechanism to effectively exercise management authority 

more broadly than has been exercised by the DoD. 

For the past several years, various recommendations have been 

advanced to provide a more comprehensive and authoritative structure 

for dealing with the major PNT infrastructure issues of the nation. Even 

though the current interdepartmental governance structure seeks to 

support the needs of civil and military users without prejudice, there is a 

perception that the military exerts undue influence in decisions affecting 

civil GPS. This perception has been used as a principal argument by those 

who would seek to advance competing technologies or services to 

supplant or ‘augment’ GPS, in some cases where technical or economic 

justification falls short. It has also provided potential underpinning for 

various initiatives to commercialize GPS in order to improve its financial 

base and to generate non-defense resources for system operation and 

improvement. 

Over the past two years, two separate studies were authorized by the 

Deputy Secretary of Defense to investigate the viability of alternative 

governance structures for managing and financing GPS to both sustain 

and enhance its services for its full complement of domestic and 

international users. The Task Force received a briefing on a preliminary 

phase of the study, termed Project Atlas, which had looked at generic 

concepts of financing applicable to GPS. A subsequent study, termed 

Project Herakles, was concluded in April 2005 and focused in detail on a 

more specific set of alternatives. Both studies indicated that alternative 

governance strategies could be feasible; however, additional work is 
 

_____________________ CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT

___________________________________________________________________________ 71

necessary before any changes could or would be implemented. Any 

substantive change in GPS governance would of course require extensive 

cooperation and support among the Executive and Legislative Branches of 

U.S. Government. Yet, given the end of the “natural monopoly” for GPS, 

and with the rapidly emerging prospect of an altered and competitive 

environment, the Task Force believes that the government should remain 

open-minded on the governance issues highlighted by Project Herakles. 

In its implementation and operation of GPS thus far, the U.S. 

Government has not made use of a comprehensive and commonly 

accepted strategy accounting for all the national equities at stake in the 

resolution of issues affecting acquisition and operation of the system. 

Similarly, there has not been a systematically constructed and commonly 

accepted architecture to foster consensus among the various agencies 

responsible for implementation of GPS and its components and 

complements. The recently signed Presidential Directive is intended to 

strengthen the interagency management process and requires the 

preparation and update of a 5-year space-based PNT Plan which could 

provide the basis for such a strategy. Unfortunately, the Task Force notes 

that the implementation of the new management structure by all the 

Departments involved appears to be significantly lagging the schedules as 

defined in the Directive. 

4.4 EXECUTION OF GPS MANAGEMENT RESPONSIBILITIES 

IN THE DOD 

Program Execution Responsibilities 

Since the inception of GPS, the Secretary of Defense has been the 

effective Executive Agent for acquiring and operating GPS for all 

represented interests of the United States. Also, the Air Force, in various 

capacities over the life of the program, has been designated as Executive 

Agent for acquisition and operation of GPS for the Department of 

Defense. On behalf of the Secretary of Defense, the Commander, 

STRATCOM is also responsible for ensuring that required GPS services 

are available for all intended users and is separately accountable for 
 

CHAPTER 4. COMPETITION, GOVERNANCE AND OPERATIONAL MANAGEMENT _____________________ 

_________________________________________________________________________ 72

exploiting GPS for Department of Defense missions. Other Departments 

and Agencies are separately accountable for exploiting GPS for their 

unique missions. 

Even in consideration of this specific definition of accountability and 

responsibility, policy and operational responsibilities for GPS within the 

DoD have been diffused by various management decisions over the last 

several years. The sometimes overlapping, sometimes disconnected roles 

of the Office of the Secretary of Defense staff components, the Joint Staff 

and the Air Force in the management of GPS have created considerable 

confusion over where responsibility for GPS actually rests. 

This sense of confusion has also impacted civil and international 

perceptions of the importance the U.S. places on GPS and the commitment 

of the U.S. to GPS sustainment and evolution. It is incumbent on the 

Secretary of Defense to redefine lines of authority and responsibility for 

the system and to reestablish the DoD position of leadership for GPS as 

the heart of the space-based PNT infrastructure both domestically and 

internationally. The Task Force recommends that the DoD remain the 

steward for all GPS satellite services and considers it vitally important that 

GPS responsibilities within the Department be clearly assigned and 

described. The Task Force recommends that the Secretary of Defense 

provide such clear guidance applicable to the full range of military and 

civil GPS signal services in the future. 
CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

________________________________________________________________________ 73

CHAPTER 5. RECOMMENDATIONS

Before detailing our recommendations, it is important to delineate 

priorities for GPS customers: the worldwide military, civil, commercial and 

scientific users who benefit from and rely on its services. 

5.1 GPS USER PRIORITIES 

As shown in the following table, GPS user priorities are generally 

common. 

User Priority Military GPS User Civil, Commercial, 

Scientific GPS User 

Availability (Short and long 

term and despite 

interference) 

9 9

Accuracy 9 9

Bounded inaccuracy 9 

(Minimize collateral 

damage) 

9 

(Assure service integrity) 

Denial of PNT sources to 

hostile parties 9

A substantive role in 

determining system 

configuration (Governance) 

9 9

Compatibility with like 

services (e.g., Galileo, QZSS, 

GLONASS) 

9 9

Table 2. GPS User Priorities 
 

CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

_________________________________________________________________________ 74

5.2 SYSTEM AND PROGRAM RECOMMENDATIONS

5.2.1 GPS Satellites and Constellation (Improve Availability and 

Accuracy)

 Commit to sustaining a 30-satellite constellation (vice the 

current 24). 

− Increases tolerable mask angle from 5 degrees to 15 

degrees to improve performance in mountainous 

terrain and urban environments. 

 Configure the constellation in three planes with 10 satellites 

per plane (this will simplify constellation sustainment, 

enabling dual satellite launches to be conducted more 

efficiently than for a six-plane, five-satellite per plane 

configuration). 

− Begin transition from the current six-plane 

constellation as soon as possible rather than waiting 

until GPS III launches begin. 

 Limit GPS III satellite weight to permit launch of two 

satellites on a single mid-size EELV 

− If the satellite exceeds weight or power thresholds that 

would compromise dual-manifest (maintain sufficient 

margin for each through development), the removal of 

secondary payloads must be evaluated. In this 

instance, NDS mission modifications and alternatives 

must be explored. 

− A regional signal (broader beam) should be 

considered as a lighter-weight and less complex 

alternative to the narrow spot beam planned for GPS 

III. 

 Continue to acquire high fidelity space-based clocks and 

navigation payloads to enable direct, high-reliability military 

accuracy in the range of 2-4 meters for precise targeting and 

weapons delivery (ensure that the industrial base for this 

technology is assured). 
 

___________________________________________________ CHAPTER 5. RECOMMENDATIONS

___________________________________________________________________________ 75

 As a part of the acquisition strategy for GPS III, include the 

option to procure higher power earth coverage satellites 

without non-GPS payloads to permit operation of a mixed 

constellation of higher-cost, high functionality satellites and 

lower-cost, utility satellites, increasing signal robustness and 

availability while lowering overall constellation life cycle 

costs. This will also provide significant global mitigation for 

GPS against both intentional and unintentional interference. 

 Incorporate a fully reprogrammable Navigation Payload 

aboard GPS satellites as soon as practicable to enable future 

flexibility in signal structure and content. 

5.2.2 GPS Control Segment and Satellite Operations (Improve 

functionality, Accelerate Capability)

 In the face of continuing, intractable Operational Control 

Segment (OCS) development problems, provide a near-term 

workaround to allow early and continuous operation of all 

new signals as they are present on-orbit (M-code, L2C, L5 

and, eventually, L1C). 

− Use of the new civil signals will be on an “at-risk” 

basis, pending declaration by the AF of full 

operational status. 

 As a solution to long-standing OCS development problems, 

conduct a parallel development of OCS functionality based 

on layered control engineering principles with clearly 

defined application programming interfaces between 

software components rather than the current heavily 

patched software engineering methodology that has proven 

unworkable. 

− This recommendation is consistent with that contained 

in a tasking conveyed to the Air Force by the ASD(NII) 

in DoD PNT Executive Committee meetings during 

early-mid 2003. 

 Modify the operational concept for satellite operations. 
 

CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

_________________________________________________________________________ 76

− Air Force personnel continue to provide guidance and 

direction to satellite operations. 

− As a means of mitigating the disruptions caused by 

personnel turnover and to provide an experienced 

cadre of GPS operators, selectively integrate contractor 

technical personnel into positions involving direct 

satellite system monitoring and execution of 

commands. In addition to its other benefits, 

implementing this practice should result in 

operational cost savings for the Air Force as well as 

freeing uniformed billets for other assignments. 

 Implement direct, independent and continuous monitoring 

of both military and civil operational capability. This should 

include projections of capability to meet user needs in both 

normal and stressed environments as well as historical data 

to provide assessments of past performance, as necessary. 

− For military assessments and projections, complete the 

addition of remaining National Geospatial-Intelligence 

Agency monitor station data into the OCS. 

− Include a direct connection to the WAAS monitoring 

system. This would provide very high fidelity 

continuous sampling of GPS availability, integrity and 

accuracy in the U.S. 

− For civil assessments and projections, consider use of 

existing worldwide civil, commercial and scientific 

GPS monitoring networks. 

− As a means of improving GPS global competitiveness, 

the GPS Civil Performance Standard should be 

updated to more closely reflect system performance 

improvements. 

− Establish an independent “civil report card” based on 

the WAAS monitoring network. This should be 

included in the weekly assessment of GPS 

performance. 
 

___________________________________________________ CHAPTER 5. RECOMMENDATIONS

___________________________________________________________________________ 77

5.2.3 GPS Military User Equipment Acquisition and Installation 

(Accelerate Anti-Jam Capability) 

 Each Service should fund its own R&D program to best 

ensure position and timing information is integrated into 

equipment and operational capabilities, following a 

STRATCOM-developed roadmap for joint, integrated, 

seamless, precision operations and to ensure operation in 

accordance with a STRATCOM established PPS performance 

standard. 

 Continue fielding Selective Availability Anti-Spoofing 

Module (SAASM) GPS equipment for missions and 

applications where access to exclusive GPS military signals 

is necessary pending production and operational availability 

of user equipment incorporating the M-Code and other 

modernization features (see below). 

 Evolve GPS user equipment from SAASM to YMCA 

configurations as rapidly as possible. 

− Change policy guidelines for procuring future GPS 

user equipment to permit at least three levels of 

performance and protection. 

 Full capability to operate with “military exclusive” GPS signal(s). 

 Full capability to operate with “military exclusive” GPS signal(s) 

with the additional capability to receive and exploit other civil and 

foreign satellite navigation signals. 

 User equipment not configured for exclusive military signals but 

which can receive and exploit the full range of accessible signals to 

enable less expensive operations in more benign interference 

environments. 

 In parallel with development of YMCA and M-Code user 

equipment, invest in complementary technologies that 

promise significant improvements in anti-jam performance. 

Integrate these features into SAASM and YMCA receiver 

designs at the earliest opportunity. Such technologies 

include, but are not limited to: 

− Adaptive multi-beam steering to counter proliferated 

mobile jammers 
 

CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

_________________________________________________________________________ 78

− Digital antenna processing 

− Narrow-band adaptive filters 

− Vector delay lock tracking 

− Deep inertial coupling 

− Network assist for acquisition/better platform 

handoffs 

− All-in-view 

− Chip-scale atomic clocks 

 Carefully plan for early integration of anti-jam receiver 

technology into high priority/high payoff weapon systems. 

− Develop a silver-bullet force comprised of specific 

delivery platform types equipped with upgraded GPSaided munitions capable of operating in hostile 

jamming environments. 

− Ensure mission concepts of operation and system 

architectures accurately reflect GPS contributions and 

relevant concepts of operation are updated to define 

workable employment concepts for silver-bullet 

resources. 

 Continue efforts to evolve the current security architecture 

to the more diversified and robust PRONAV security 

architecture. 

 One decision that the Task Force considers essential to 

improving opportunities for future flexibility in GPS 

satellites and user equipment is to permanently eliminate the 

requirement for Selective Availability in all future 

equipment designs with the objective of deleting the 

hardware and software overhead for its implementation 

from throughout the future system. 

5.2.4 Improving Anti-Jam Performance

 Initiate an aggressive program to introduce anti-jam 

enhancements soon in appropriate military receivers, 

namely: 
 

___________________________________________________ CHAPTER 5. RECOMMENDATIONS

___________________________________________________________________________ 79

− Receivers that are being redesigned to accommodate 

M-code 

− Receivers in new weapon systems being developed 

− Selected “silver-bullet” subsets of receivers in 

munitions 

 Proceed with GPS III with a firm resolve and process to 

control satellite weight such that two satellites can be 

launched on a single booster, namely: 

− Control “requirements creep” through consistent 

program oversight exercised by the ASD(NII) and 

USD(AT&L) 

− Maintain sufficient weight and power margins 

through development 

− Be prepared to off-load portions or all of other 

payloads such as NDS if necessary. 

5.2.5 Dealing with Galileo

 Remain open to and promote opportunities for cooperation 

under the recent U.S.-EU agreement and in accordance with 

the recent Presidential Directive. 

 Strongly promote true civil interoperability – well defined 

geodetic and time transformations that can be easily 

implemented in user equipment. 

 Insist on full disclosure of the open signal structure. 

 Continue purposeful implementation of a separate strategy 

to provide a superior military and an acceptable civil PNT 

capability for U.S. interests globally using the militarily 

supported GPS as the core capability. 

 Maintain a PNT system configuration that will permit 

Galileo assets to increase the capability presented by the 

combination of both systems for civil users. 

 Prepare for discussions within the NATO environment 

regarding possible use of Galileo services for military 

purposes by NATO member nations. 
 

CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

_________________________________________________________________________ 80

 Explore with the Europeans a collaborative approach that 

maintains the sovereign independence of both parties while 

permitting the creation of greater capability at lower cost 

than either could achieve alone for commercial benefit. 

 Explore cooperative exchange of monitoring information. 

5.2.6 Organization and Governance

 The recently signed Presidential Directive on Space-Based 

PNT affords an opportunity for all stakeholders to correct 

deficiencies of the former Interagency GPS Executive Board. 

The following recommendations address the effectiveness of 

the new structure. 

− If Deputies do not routinely participate, then 

designated representatives to the National SpaceBased PNT Executive Committee (NPEC) must be 

formally empowered to speak for and act on behalf of 

their respective Deputies for all matters coming before 

the NPEC. 

− Strengthen the effectiveness of the full-time National 

Space-Based PNT Coordination Office (NPCO) by 

formally designating senior technical focal points 

within each department who will keep the NPEC 

principals fully apprised of all PNT matters being 

developed by the NPCO for executive level 

consideration and action. 

− Stakeholders can use this forum to investigate the 

viability of alternative methodologies for managing 

and financing GPS to address current issues and more 

effectively sustain and enhance services for its full 

complement of domestic and international users into 

the future. 

 The Secretary of Defense should also clarify lines of 

authority and responsibility within the Department to 

eliminate ambiguity regarding GPS responsibilities that 

hinders decision making internally and that perpetuates the 
 

___________________________________________________ CHAPTER 5. RECOMMENDATIONS

___________________________________________________________________________ 81

perception externally that the DoD has lost sight of its GPS 

stewardship responsibilities. 

− Designate a single focal point within the Office of the 

Secretary of Defense responsible for all GPS policy and 

oversight matters including clearly defined 

relationships with the Joint Staff and Services 

(including the Air Force) regarding GPS operations 

and acquisition, respectively. 

− Use the DoD PNT Executive Committee process to 

conduct a top-to-bottom review and develop 

recommendations regarding organizational 

structure(s) for DoD PNT role. 

− Sponsor and lead an interagency effort to develop a 

comprehensive national PNT architecture to guide 

future investment and implementation decisions 

regarding GPS and complementary systems and 

technologies. 

− The Secretary of Defense should reemphasize in 

writing the criticality of GPS operations, similar to the 

emphasis he has previously issued for GPS 

acquisition. 

 Commander STRATCOM can quickly demonstrate improved 

operations through support of Commander 14th AF tasking to 

stand up a Joint GPS Service Support Center (as part of the Joint 

Space Operations Center). The center’s primary operational task 

would be improved position and time services to military users, 

achieving this initially through the collection and assessment of 

GPS monitor information from reliable, independent global 

sources and in the longer term by providing operational guidance 

for updating the control segment software. The center could also 

provide a source of information on all foreign GNSS available 

(GLONASS, Galileo, other systems), for space situation 

awareness. 

− In fulfilling its stewardship obligation for providing 

civil and military space-based PNT, the Commander, 

STRATCOM should be directed by the Secretary of 

Defense to develop and maintain a roadmap for 
 

CHAPTER 5. RECOMMENDATIONS ___________________________________________________ 

_________________________________________________________________________ 82

achieving joint, integrated, seamless, precision 

military operations, to coordinate Service-developed 

user equipment roadmaps for compatibility and to 

establish and maintain SPS and PPS performance 

standards. STRATCOM could then task its component 

(Air Force Space Command) to implement standards 

and reporting criteria in accordance with routine joint 

system performance reporting instructions. 

− Include designated representatives from STRATCOM 

on all DoD and interagency executive committees and 

working groups involved with management and 

operation of GPS. 

− Ensure that the concept of stewardship for GPS 

operations as passed from the Secretary of Defense to 

STRATCOM includes responsibility for being aware of 

and meeting civil service performance needs as 

mutually agreed between the DoD and civil users and 

reflected in the GPS Civil Performance Standard. 
APPENDIX A. TERMS OF REFERENCE _________________________________________________ 

________________________________________________________________________ 83

APPENDIX A. TERMS OF REFERENCE
 

APPENDIX A. TERMS OF REFERENCE _________________________________________________ 

_________________________________________________________________________ 84

This page intentionally left blank.


APPENDIX B. TASK FORCE MEMBERSHIP_______________________________________________ 

________________________________________________________________________ 85

APPENDIX B. TASK FORCE MEMBERSHIP

Co-Chairmen 

Dr. Robert Hermann Global Technology Partners, LLC 

Hon. James Schlesinger MITRE Corporation 

Task Force Members 

Mr. John Darrah Institute for Defense Analyses 

Mr. William Delaney MIT Lincoln Laboratory 

Mr. Arnold Donahue Project Director NAPA 

Mr. Kirk Lewis Institute for Defense Analyses 

Gen James McCarthy, USAF (Ret) United States Air Force Academy 

Mr. Steve Moran Raytheon 

Ms. Ruth Neilan NASA Jet Propulsion Laboratory 

Mr. Robert Nesbit MITRE Corporation 

Dr. Brad Parkinson Stanford University 

Dr. James Spilker Stanford University 

Hon. John Stenbit Private Consultant 

Gen Larry Welch, USAF (Ret) Institute for Defense Analyses 

Executive Secretary 

Mr. Ray Swider OSD (NII) 

DSB Representative 

LtCol David Robertson, USAF 

Government Advisors 

Mr. Robert Broussard Headquarters, USAF 

LtCol Hazel Kelly, USAF Office of the Secretary 

of the Air Force 

Ms. Pamela Hodge Headquarters, USAF 

Mr. Richard McKinney Headquarters, USAF 

Staff 

Dr. Evelyn Dahm Strategic Analysis Inc. 

Mr. Jules McNeff Overlook Systems Technologies, Inc. 
APPENDIX B. TASK FORCE MEMBERSHIP ______________________________________________ 

________________________________________________________________________ 86

This page intentionally left blank.
APPENDIX C. BRIEFINGS RECEIVED BY THE TASK FORCE____________________________________ 

________________________________________________________________________ 87

APPENDIX C. BRIEFINGS RECEIVED BY THE TASK FORCE

Name Topic 

Mr. Gil Klinger NSPD-X 

Mr. Jeff Shane Civil GPS Requirements 

Mr. Ralph Braibanti Draft GPS-Galileo Agreement 

Col Rick Reaser, USAF GPS/Galileo National Security Compatibility Criteria; 

Security Architecture 

Col Allan Ballenger, USAF GPS Program Update 

Col Norman Albert, USAF NAVWAR SAR Final Report 

Mr. Jay Rixse Project Atlas 

Mr. Milt Creighton Emerging Jamming Threats 

Maj Patrick Huested, USAF GPS Control Segment Modernization 

Mr. John Darrah/ 

Ms. Ruth Neilan 

Operationalizing GPS 

Lt Col John Anderson, USAF GPS III Space Segment & Launch Vehicle Compatibility; 

GPS UE NAVWAR Initiatives 

Ms. Ruth Neilan Monitoring Task Report 

Mr. Yoaz Bar-Sever NASA Global Differential GPS System 

Mr. Eddy Emile Advanced GPS User Equipment Architectures & 

Technology Roadmap 

U.S. Navy GPS Roadmap 

 
 

APPENDIX C. BRIEFINGS RECEIVED BY THE TASK FORCE ___________________________________ 

_________________________________________________________________________ 88

This page intentionally left blank. 
APPENDIX D. GPS CONSIDERATION FOR SMALL 

DIAMETER BOMB AND THE F-22 ____________________________________________________ 

________________________________________________________________________ 89

APPENDIX D. GPS CONSIDERATIONS FOR SMALL DIAMETER 

BOMB (SDB) AND THE F-22 

Because of its light weight and compact configuration, the SDB promises 

greater mission effectiveness at lower sortie and logistic cost than was ever 

before achievable. The Task Force believes that, for optimum effectiveness, 

the employment objectives for the SDB should include all weather day-night 

delivery at an accuracy of 2 meters or better. Techniques to attain these levels 

of accuracy have been already been demonstrated for a variety of civil 

applications, including robotic farming, and precision machine operations to 

accuracies of better than 10 centimeters. The SDB objectives are achievable, 

but for successful implementation, at least four issues must be addressed: 

1. The F-22 must have ensured, continuous availability of GPS. This 

implies that it should incorporate the latest in anti-jam GPS receiver and 

antenna technology. At least 90 dB of jam resistance is essential, and beam 

steering antennas will be required to counter distributed jammers. 

2. The F-22 platform must be configured to directly hand off a complete 

GPS position, velocity and time solution to the SDB prior to release. This will 

ensure that the GPS receiver in the SDB can lock up immediately on release 

and clearance from the aircraft. This capability is essential to achieving jam 

resistance and sustaining accuracy. 

3. The SDB program should pursue options to enhance GPS-inertial 

coupling to increase jam resistance beyond that provided by the baseline 

GPS-inertial package. All SDBs may not require this “silver bullet” 

capability; however, there should be at least one version of the SDB that is so 

configured. 

4. To achieve the ultimate required operational effect, the issue of target 

location accuracy must be addressed, and will require higher precision than is 

now part of the “requirements”. To achieve 2 meter weapon-on-target 

accuracy, the allocation of Target Location Error should be less than 1 meter. 

The Task Force believes there are technologies and techniques to attain this 
 

APPENDIX D. GPS CONSIDERATION FOR SMALL 

DIAMETER BOMB AND THE F-22____________________________________________________ 

_________________________________________________________________________ 90

today, and the NGA should coordinate a system-of-systems effort to ensure 

this performance is realized. 
APPENDIX E. SPATIAL INTEROPERABILITY______________________________________________ 

________________________________________________________________________ 91

APPENDIX E. SPATIAL INTEROPERABILITY

In the specific case of air-delivered weapon support to ground forces, the 

precision bombing benefits of the common-grid capability afforded by GPS 

cannot be assumed in advance. To ensure GPS common-grid is applied in 

air-delivered weapons support, a change in joint doctrine is necessary to 

require in-theater use of the grid reference alphanumeric position reporting 

system, Military Grid Reference System (MGRS), for all 2-D positioning, 

navigation and targeting purposes and as the 2-D component of 3-D 

operations. Universal use of the MGRS for all in-theater spatial operations 

will eliminate confusion regarding which coordinate system is being used in 

navigating and reporting positions and targets. It will also eliminate the 

practice of requiring that ground personnel electronically or manually 

convert positions and targets from MGRS to latitude and longitude for the 

purpose of obtaining support from aviation components. 

In any emergency situation, whether in a war zone or the domestic 

environment, spatial interoperability is as important as communications 

interoperability. Said another way, confusion in identifying an incident 

location can be as deadly as not being able to transmit that location to a 

potential responder. GPS can solve that problem, but only if it is employed 

smartly and with forethought. GPS enables common grid operations, but 

only if the participants agree in advance on which of the many available 

coordinate grids they will use to identify locations of importance to the 

operations. Coordinate grids are the languages of location, and using 

different grids in the same operation is analogous to trying to communicate in 

different languages. 

MILITARY SPATIAL INTEROPERABILITY

In the military mission environment, spatial confusion in joint operations 

can result from different participants in an operation expressing locations 

using spherical geographic coordinates (latitude and longitude - lat/lon) and 

planar grid coordinates (Military Grid Reference System). There are good 

reasons for using each, primarily related to distances traveled, but from a 

spatial interoperability standpoint this is like discussing ground operations in 
 

APPENDIX E. SPATIAL INTEROPERABILITY _____________________________________________ 

_________________________________________________________________________ 92

English and airborne operations in Chinese. When the two have to work 

together, translation is critical, but under stress, mistakes are all too common. 

The burden of conversion routinely falls on the ground troops, who are likely 

already over tasked in a stressful environment, many times under enemy fire. 

This is the reason for the recommended revision to joint operational doctrine 

expressed in the Weapons Delivery section above. 

CIVIL/HOMELAND SECURITY SPATIAL OPERATIONS

In the civil environment, people today have great difficulty in finding map 

products (even those provided by digital sources) which contain grids that 

can be used with GPS equipment. Those map products that do include grids 

may use any of several grid systems to identify locations, a lack of 

standardization that can create time-consuming confusion in time of 

emergency. Many of the commercial proprietary grids do not permit precise 

locations to be determined, and virtually none work with GPS equipment. 

However, in a December 2001 action to address Homeland Security issues, 

the U.S. Federal Geographic Data Committee approved a new standard grid 

for such applications that can eliminate this spatial confusion. Called the U.S. 

National Grid (USNG), this standard will permit easy depiction of positions 

to 10 meters or less anywhere in the United States using an alphanumeric 

designator about the size of a telephone number. The USNG is based on the 

global standard grid called Universal Transverse Mercator, so it is nonproprietary and globally extendable. It is also designed to be identical to the 

MGRS grid coordinate system used by the Army and Marine Corps, so it can 

directly enable spatial uniformity in joint civil-military response operations. 

Lack of a uniform method for describing incident locations has long been 

a major impediment to rapid and effective emergency response in diverse 

metropolitan and rural areas. Until the adoption of the USNG, there has been 

no standard that would enable uniform large-scale map products to be 

created that could be used directly with GPS equipment and be applicable 

across jurisdictional boundaries nationwide. The USNG corrects that glaring 

discrepancy, but, having now been officially adopted, it still must be used to 

be effective. A program of education and training, beginning at the middle 

school level, would be instrumental in facilitating its use by the public. More 

focused leadership by the Federal Government to promote such basic 

education as well as training in the uniform application of GPS at federal, 
 

_____________________________________________ APPENDIX E. SPATIAL INTEROPERABILITY

___________________________________________________________________________ 93

State and local levels by emergency responders would pay nationwide 

dividends for Homeland Security. 

The immediate domestic impact of USNG will be to ensure that GPS is 

directly useable with properly gridded map products to quickly enable multiagency and multi-jurisdictional emergency responders, and the public in 

general, to precisely identify geolocations in the real world. Linking current 

technologies of overhead imagery and Nationwide Differential GPS at onemeter accuracy, the USNG can facilitate direct creation of gridded, very 

precise, large-scale image maps that would be immediately useable with GPS 

receivers. These maps will be extremely useful to emergency responders as 

they will depict the emergency environment as it exists rather than as it 

previously appeared from potentially out-of-date legacy sources. GPS 

commercial receiver manufacturers are now beginning to include the USNG 

in their newest products. As awareness of its usefulness grows, prompted by 

education, the USNG will be a principal integrating mechanism to create 

spatial interoperability nationwide. It will be equally effective among multijurisdictional civil emergency response organizations and, when necessary, 

between those organizations and the military to support any and all domestic 

emergency response and disaster relief operations. 
 

APPENDIX E. SPATIAL INTEROPERABILITY _____________________________________________ 

_________________________________________________________________________ 94

This page intentionally left blank. 
APPENDIX F. USER EQUIPMENT UPGRADE COSTS ________________________________________ 

________________________________________________________________________ 95

APPENDIX F. USER EQUIPMENT UPGRADE COSTS (“SILVER 

BULLET” CAPABILITY) 

A rough estimate of the cost of upgrading important military receivers 

with anti-jam fixes is given in the following table. These upgrades involve 

technologies such as adaptive antennas, advanced receiver processing 

architectures, and miniature precision clocks. 

The costs include both the individual anti-jam hardware and the cost of 

integration on the platform for the cases where a retrofit is assumed. Cases 

such as JDAM and artillery shells do not involve integration costs since the 

improvements would be installed in the initial production. 

An AJ upgrade to a GPS munition-like JDAM might cost $4K, an artillery 

shell $1K, a strike aircraft $50K, plus an additional $50K for retrofit 

(“integration”) cost. Some platforms, like GPS-guided artillery shells and 

JDAMS, need only a portion of the inventory upgraded (the “silver-bullet” 

approach). 
 

APPENDIX F. USER EQUIPMENT UPGRADE COSTS ________________________________________ 

_________________________________________________________________________ 96

Platform Total 

Number 

Number 

Upgraded 

Cost of AJ 

Upgrade Total Cost 

Strike Aircraft 2,000 2,000 

 $50 K 

+ $50 K 

integration 

 $ .2 B 

Various Cruise 

Missile Types 2,500 2,500 

 20 K 

+ $20 K 

integration 

 .1 B 

JDAMS 230,000 50,000 4 K .2 B 

Artillery Shells 500,000 100,000 1 K .1 B 

Hand-held 

Receivers 100,000 100,000 

 1 K 

 + $1 K 

integration 

 .2 B 

Other Platforms 5,000 5,000 

 20 K 

+ $20 K 

integration 

 .2 B 

 Total $1.0 B 
 

________________________________________________________ APPENDIX G. ACRONYMS

__________________________________________________________________________ 

97

APPENDIX G. ACRONYMS

2SOPS 2nd Satellite Operations Squadron 

 

AII Accuracy Improvement Initiative 

ASD(NII) Assistant Secretary of Defense (Networks & Information 

Integration 

 

COMSEC Communications Security 

COTS Commercial Off-the-Shelf 

CSEL Combat Survivor Evader Locator 

 

DoD Department of Defense 

DSB Defense Science Board 

 

ECEF Earth-Centered-Earth-Fixed 

EELV Evolved Expendable Launch Vehicle 

EOD Explosive Ordinance Disposal 

EPLRS Enhanced Position Location Reporting System 

ERGM Extended Range Guided Munitions 

EU European Union 

 

FAA Federal Aviation Administration 

 

GDGPS Global Differential GPS service 

GEO Geosynchronous Earth Orbit 

GLONASS Global Orbiting Navigation Satellite System 

GNSS Global Navigation Satellite System 

GPS Global Positioning System 

GPS III Global Positioning System III 

 
Appendix G. Acronyms 

98 ________________________________________________________________________

IA Information Assurance 

IGS International GPS Service 

ISR Intelligence, Surveillance/Reconnaissance 

ITRF International Terrestrial Reference Frame 

 

JCS Joint Chiefs of Staff 

JDAMs Joint Direct Attack Munitions 

JPL Jet Propulsion Laboratory 

JPO Joint Program Office 

JRIDS Joint Tactical Information Distribution System 

JROC Joint Requirements Oversight Council 

JTRS Joint Tactical Radio System 

 

L2C Civil GPS Signal at L2 Frequency 

LAAS Local Area Augmentation System 

LPI/LPD Low Probability of Intercept/Low Probability of Detection 

 

M-code Military Code 

MCS Master Control Station 

MEO Medium Earth Orbit 

MGRS Military Grid Reference System 

 

NASA National Aeronautics & Space Administration 

NATO North Atlantic Treaty Organization 

NAVWAR Navigation Warfare 

NDGPS Nationwide Differential GPS 

NDS NUDET Detection System 

NGA National Geospatial Intelligence Agency 

NIST National Institute of Standards and Technology 

NPCO National Space-based PNT Coordination Office 

NPEC National Space-based PNT Executive Committee 

NUDET Nuclear Detonation 

 

OCS Operational Control Segment 

OMB Office of Management and Budget 

OSD Office of Secretary of Defense 
 

________________________________________________________ APPENDIX G. ACRONYMS

__________________________________________________________________________ 

99

 

PNT Positioning, Navigation and Timing 

PPS Precise Positioning Service 

PPS-SM/AOC PPS Security Module/Auxiliary Output Chip 

PRONAV Protection of Navigation 

 

QZSS Quazi-Zenith Satellite System 

 

R&D Research & Development 

 

SAASM Selective Availability Anti-Spoofing Module 

SDB Small Diameter Bomb 

SSPS Signal Specification/Performance Standard 

SPS Standard Positioning Service 

STRATCOM U.S. Strategic Command 

 

TLE Target Location Error 

 

UHF Ultra High Frequency 

USD(AT&L) Office of Undersecretary of Defense (Acquisition Technology & 

Logistics 

USNG U.S. National Grid 

USNO U.S. Naval Observatory 

UTC Universal Coordinated Time 

 

WAAS Wide-Area Augmentation System 

WGS-84 World Geodetic System 1984 

 

YMCA Y-code, M-code, CA- coarse acquisition code