APPLIED ENGINEERING AND TECHNOLOGY DIRECTORATE

 

Flight Dynamics Analysis Branch 

End of Fiscal Year 2000 Report 

 

 

National Aeronautics and 

Space Administration 

Goddard Space Flight Center 

Flight Dynamics Analysis Branch/Code 572 

Greenbelt, Maryland 20771

October 2000 

 

Flight Dynamics Analysis Branch 

End of Fiscal Year 2000 Report 

 

 

 

National Aeronautics and 

Space Administration 

 

Goddard Space Flight Center 

Flight Dynamics Analysis Branch/Code 572 

Greenbelt, Maryland 20771

Acknowledgements

The contents of this report are based on inputs generously supplied by members of the Guidance, 

Navigation, and Control Center (GNCC) Flight Dynamics Analysis Branch (FDAB) at NASA/Goddard

Space Flight Center (GSFC). 

The primary editors of this report are: 

Tom Stengle, Head, Flight Dynamics Analysis Branch, Code 572 

Felipe Flores-Amaya, Flight Dynamics Analysis Branch, Code 572 

Additional information concerning FDAB activities may be obtained through the following Branch

management:

John P. Lynch, Associate Head, Flight Dynamics Analysis Branch, Code 572 

Karen Richon, Associate Head, Flight Dynamics Analysis Branch, Code 572 

Published copies of this report are available from:

Catherine A. Waltersdorff 

Flight Dynamics Analysis Branch 

Code 572 

NASA/Goddard Space Flight Center 

Greenbelt, MD 20771 

A Hypertext Markup Language (HTML) version of this document will be available on the Internet World

Wide Web (WWW) in the Uniform Resource Locator (URL): 

http://aetd.gsfc.nasa.gov/gncc/branches/fdab/FDAB_EOFY2000.html.

 

 

ABSTRACT 

This report summarizes the major activities and accomplishments carried out by the Flight Dynamics 

Analysis Branch (FDAB), Code 572, in support of flight projects and technology development initiatives in

Fiscal Year (FY) 2000. The report is intended to serve as a summary of the type of support carried out by 

the FDAB, as well as a concise reference of key accomplishments and mission experience derived from the 

various mission support roles. The primary focus of the FDAB is to provide expertise in the disciplines of

flight dynamics, spacecraft trajectory, attitude analysis, and attitude determination and control. The FDAB 

currently provides support for missions and technology development projects involving NASA, 

government, university, and private industry.

TABLE OF CONTENTS 

1.0 Introduction 

2.0 Flight Project Support

2.1 Development Missions 

2.1.1 Earth Observing–1 (EO-1) 

2.1.2 Microwave Anisotropy Probe (MAP) 

2.1.3 EOS AQUA Mission 

2.1.4 TRIANA 

2.1.5 EOS AURA 

2.1.6 Space Technology (ST)-5 

2.1.7 Geostationary Operational Environmental Satellite (GOES)-(N-Q) 

2.1.8 Balloon Program

2.2 Operational Missions 

2.2.1 EOS Earth Observing System Terra 

2.2.2 GOES-L Launch Support 

2.2.3 The Re-Entry of the Compton Gamma Ray Observatory 

2.2.4 TRMM Tropical Rainfall Measuring Mission Reentry Planning 

2.2.5 General Space Operations Management Office (SOMO) Support 

3.0 Study Mission Support

3.1 IMDC Integrated Mission Design Center 

3.2 Ana Lani 

3.3 Fluorescence Experiment (FLEX) 

3.4 Global Precipitation Mission (GPM) 

3.5 Joule 

3.6 Mars Areo-stationary Relay Satellite (MARSAT) 

3.7 Living With a Star (LWS)

3.8 NGST/Nexus 

3.9 NPP

3.10 Ocean Surface Salinity Mission (OSSM) 

3.11 Solar Sail 

3.12 Constellation X 

3.13 Magnetospheric Multiscale Mission (MMS) 

3.14 KRONOS

3.15 Leonardo

4.0 Technology Development Activities 

4.1 Advanced Mission Design

4.2 Autonomous Onboard Navigation Systems 

4.2.1 Terra Onboard Navigation - The TDRSS Onboard Navigation System (TONS)

4.2.2 Onboard Navigation Systems Using Communication Links 

4.2.3 Global Positioning System Advanced Concepts

4.2.4 EO-1 Global Positioning System (GPS) 

4.2.5 Relative Navigation 

4.2.6 Celestial Navigation 

4.3 Formation Flying Technologies 
4.3.1 EO-1 Formation Flying Experiment 

4.3.2 Integration of a Decentralized Linear-Quadratic-Gaussian Control into

 GSFC’s Universal 3-D Autonomous Formation Flying Algorithm 

4.3.3 Tethered Formation Flying Examined for SPECS 

4.4 Attitude Determination and Modeling Techniques 

4.4.1 SKYMAP 

4.4.2 Attitude Sensor Performance Analysis 

4.4.3 Advanced Attitude Determination and Sensor Calibration Techniques 

5.0 Branch Infrastructure 

5.1 Flight Dynamics Tool Program

5.2 GNCC Flight Dynamics Data Lab 

5.3 Branch Library 

5.4 Employee Handbook 

6.0 Interagency Activities 

6.1 GSFC Standards Program

6.2 Mars Climate Orbiter Mishap Investigation 

7.0 Outreach Activities 

7.1 Educational Outreach: International Space University 

7.2 SAMPEX University Operations 

7.3 Educational Outreach: NASA Academy 

7.4 PREST Program 

7.5 Graduate Student Research Program (GSRP) 

7.6 Public Education/Community Outreach 

Appendix A – Awards 

Appendix B - University Grants 

Appendix C – Conferences and Papers 

Appendix D- Acronyms and Abbreviations 
1.0 Introduction

The Guidance, Navigation and Control Center (GNCC) at the Goddard Space Flight Center (GSFC)

provides the skills, vision and leadership in guidance, navigation and control (GN&C) systems, 

engineering, operations and mission analysis to enable revolutionary Earth and Space Science discovery. 

The scope of technical disciplines encompassed by the GNCC is broad and includes all aspects of flight

dynamics, propulsion, flight mechanics, guidance, navigation and control engineering for space systems, 

experiments, and sub-orbital missions. The range of products and services is also broad and requires 

expertise in skill areas such as advanced component design, control system architecture, propulsion design, 

trajectory analysis, autonomy and mission design. 

Within the GNCC, the Flight Dynamics Analysis Branch (FDAB), Code 572, is responsible for providing

Guidance, Navigation and Control analytic expertise for trajectory and attitude systems. This includes 

dynamics and control analyses and simulations of space vehicles. The Branch creates and maintains stateof-the-art analysis tools for mission design, trajectory optimization, orbit analysis, navigation, attitude

determination, and controls analysis. The Branch also provides the expertise to support a wide range of

flight dynamics services such as mission design, on-orbit sensor calibration, and launch/early orbit

operations. The FDAB also maintains an active technology development program, with special emphasis 

on developing new techniques and algorithms for autonomous orbit/attitude systems and advanced

approaches for trajectory design. Specific areas of expertise resident in the FDAB are: 

• Attitude and trajectory analysis and control design

• Control/Structure interaction analysis 

• Mission (attitude & trajectory) planning

• Estimation techniques 

• Vehicle autonomy 

• Constellation analysis 

• Flight Dynamics model development

This document summarizes the major activities and accomplishments performed by the FDAB in support 

of flight projects and technology development initiatives in Fiscal Year (FY) 2000. The document is 

intended to serve as both an introduction to the type of support carried out by the FDAB, as well as a 

concise reference summarizing key analysis results and mission experience derived from the various 

mission support roles assumed over the past year. The FDAB staff that are involved in the various analysis 

activities within the branch prepared this document. Where applicable, these staff members are identified

and can be contacted for additional information on their respective projects. 

Among the major highlights by engineers in the FDAB during FY2000 are:

• Controlled reentry planning and operations for the Compton Gamma Ray Observatory (CGRO) 

• Successful launch and early operations support for the Terra and GOES-L missions 

• Design and implementation of the control system for Triana 

• Successful mission design and attitude control system analysis support to numerous mission concept 

studies such as GPM, MMS, Constellation X and Nexus 

• First operational use of the Tracking Data Relay Satellite System (TDRSS) Onboard Navigation

System software in support of routine Terra operations

• GSFC Software of the Year award given to the Global Positioning System (GPS) Enhanced Orbit

Determination (GEODE) software (runner-up for the NASA Software of the Year award)

• Delivery of GEODE release (V5) supporting relative navigation in Highly Elliptical Orbit (HEO) and

Geosynchronous Earth Orbit (GEO) missions, and relative navigation 

• GEODE initial integration with PiVoT GPS Receiver & ITT Low Power Transceiver 

• More than a dozen technical papers and journal articles as well as active participation at national and

international GN&C/Flight Dynamics conferences 

• Initial “operational” configuration of the Flight Dynamics Lab completed
2.0 Flight Project Support

This section summarizes FDAB support to Goddard flight projects during FY00. For purposes of this

report, these projects are classified as: 

• Development Missions: Approved missions under development.

• Operational Missions: Missions that were in-flight in FY00. This includes missions that were in the 

final stages of development and were successfully launched in FY00 (e.g. Terra). 

Support to future mission concept studies and proposal support for missions seeking project approval are 

covered in section 3. 

2.1 Development Missions

2.1.1 Earth Observing–1 (EO-1) (planned launch 11/2000)

The Earth Observing –1 mission (EO-1) is scheduled for launch in the later half of November, 2000. This

sun-synchronous mission will fly in formation with the Landsat-7 spacecraft during its nominal one year 

lifetime. The formation will consist of EO-1 remaining one minute (+/- 6 seconds) behind Landsat-7 in

Mean Local Time at the descending node. Other orbital parameters are to remain essentially the same as

those of Landsat-7. EO-1 contains three primary instruments: the Advanced Land Imager (ALI), the

Atmospheric Corrector (AC) and Hyperion. The ALI, built by the Massachusetts Institute of 

Technology/Lincoln Laboratories (MIT/LL), is the next generation of Earth Imager that will continue the 

work carried on through 25 years of NASA’s Landsat programs. To validate the quality of the ALI, the 

mission’s main goal is to compare 200 co-fly scenes taken by both EO-1 and Landsat-7. Approximately 

1000 co-fly scenes will be taken to achieve the best 200 scenes. In addition to the instruments mentioned,

EO-1 is a space technology mission featuring a total of 10 different space related technologies. 

The Flight Dynamics Analysis Branch (FDAB) has taken the lead in preparing the tools and training 

personnel to provide Flight Dynamics support to EO-1 during EO-1 Launch & Early Orbit (L&EO) and

Normal Operations. For L&EO, the team will consist of members of the FDAB, the EO-1 Flight

Operations Team (FOT), the Flight Dynamics Facility and AI-Solutions, Inc. Support from the L&EO 

flight dynamics team will continue until approximately Launch + 45 days. All Flight Dynamics support 

after the first 8-10 hours of the mission will be performed in the EO-1 Mission Operations Center (MOC). 

The institutional Flight Dynamics Facility will provide some early orbit support, mostly involving TDRS. 

The EO-1 Flight Dynamics Support Subsystem (FDSS) will reside on redundant HP Workstations and 

PC/NTs in the MOC. The four major processes for this support include: orbit determination, orbit 

maneuver control, orbit & attitude product generation and attitude support, including planning instrument

calibrations. All are supported using Commercial Off-the-Shelf 

(COTS) based software to reduce costs. The L&EO period nominally includes 8 orbit maneuvers taking 17

days to phase EO-1 into its required orbit with respect to Landsat-7. Between these maneuvers, sensor and 

gyro calibrations will be performed . 

Tracking data for EO-1 is nominally from the Global Positioning System (GPS) with S-Band tracking used

for validation of GPS and backup. After supporting EO-1 for several months using ground based 

Formation Flying calculations for orbit maneuvers, the onboard Enhanced Formation Flying algorithm will 

become prime with the ground software used as a validation tool and a backup. 

The FDSS will provide approximately 25 orbit and attitude products weekly to the EO-1 Principal 

Investigators and the Mission Operations Planning and Scheduling System (MOPSS) personnel at GSFC 

who support the EO-1 Mission Science Office. 
Note: See section 4.3.1 for a description of the EO-1 formation flying experiment, and section 4.2.4 for a 

description of FDAB involvement with the EO-1 GPS package. 

[Technical contacts: Robert L. DeFazio, Richard J. Luquette, Chad Mendelsohn] 

2.1.2 Microwave Anisotropy Probe (MAP) (planned launch 7/2001)

Microwave Anisotropy Probe (MAP) is a MIDEX-class mission produced in partnership between GSFC

and Princeton University. The primary objective is to measure temperature fluctuations and to produce a 

high sensitive and spatial resolution map of the cosmic microwave background radiation over the entire 

sky. There is only one instrument on the spacecraft. The MAP will be placed in a Lissajous orbit about the 

Sun-Earth L2 Lagrange point 1.5 million kilometers from Earth. 

FY 2000 has been a very productive and busy year for the MAP team as we are preparing for a launch in

the second quarter of 2001. The MAP spacecraft launch has been manifested for no earlier than April 18, 

2001. Flight Dynamics Analysis Branch members of the Attitude Control System (ACS), and flight

dynamics teams have successfully completed a number of important milestones during this year. 

In the trajectory design area, several major reviews were held during this fiscal year to present the status of 

the trajectory design, maneuver operations and navigation support. Several independent (outside GSFC)

flight dynamics experts supported the reviews. These included trajectory peer reviews in December 1999 

and September 2000, in addition to a trajectory review conducted as part of the Flight Operations Review 

in April 2000. At the beginning of January 2000, a tiger team, consisting of representatives from all areas 

of the MAP project, was formed to address the action items from the December 1999 Trajectory Design 

Review. Once the tiger team identified all the work needed to be done in the Trajectory Design and

Maneuver Operations areas, it evolved into the Maneuver Operations Team. The team currently consists of

representatives from Trajectory Design, ACS, Propulsion, Flight Software, S/C controllers, and Navigation. 

The Maneuver Ops Team was formed to address the problem of planning, executing, and verifying all

maneuvers. The Maneuver Team has generated information flow diagrams and has developed processes to

plan, execute, and verify maneuvers. This entire process has been demonstrated during several maneuver

simulations, and is currently being refined and updated. The Maneuver team has also been instrumental in

setting up for these simulations, evaluating anomalies, and verifying the performance of the maneuvers. 

We have also identified interfaces between subsystems, the software required to plan the maneuver, and the 

data and file formats. Interface Control Documents (ICDs) are currently under development and various

procedures have been written and implemented in support of the simulations. To increase the accuracy of 

the simulations, we added a propulsion blowdown model to the Hybrid Dynamic Simulator (HDS) and to

the ACS HiFi simulation to properly model the effects of thruster firings on the fuel mass. In addition, fuel 

budgets were produced many times in support of many reviews during the year. The team has already 

supported several simulations and will continue to support simulations on a monthly basis. 

 

The MAP team has also completed a significant amount of analysis work. In particular, we have completed 

and delivered most of the nominal trajectories for the prospective launch months of April, May, June, and

July to Boeing. We have completed and documented a number of contingency analyses as well as other 

trajectory analysis requested by the Trajectory Peer review panel from the December 1999 review and by 

the MAP project. We have completed the following contingency analysis: Using Mid Course Correction

(MCC) delta V to remove L2 lunar Shadows, lunar shadow avoidance at L2, missed first perigee (P1)

maneuver, strategy to move perigee maneuvers into a station contact and splitting perigee maneuvers to

mention a few. In addition, we completed an orbit determination covariance analysis for the phasing loops 

and L2 phases which was used to derive the orbit determination requirements and tracking requirements for 

maneuver calibration and planning. Figure 2-1 shows the MAP trajectory.

Moreover, the trajectory team also built an analytic model for the phasing loops that determines delta-V 

distribution across perigee maneuvers to achieve the proper timing and energy. We also performed analysis

to design the MAP trajectories with an opening Lissajous and to determine the Lissajous amplitude to meet 

MAP constraints. In addition to all the analysis mentioned above, the trajectory team performed a 
parametric study and later a Monte Carlo analysis to investigate the launch vehicle dispersions in order to

guarantee that trajectories that satisfy all mission requirements are available for all dispersions and within

the fuel budget. We also developed a Matlab script as an automated way to evaluate the maneuver 

execution errors. 

Finally the MAP team has supported a large numbers of MAP reviews such as the MAP L-1 year review, 

the Flight Operations Review, Environmental Review, and the Red Team Review. 

 

 

 

Figure 2-1 Sample of the MAP 3-loop trajectory 

The ACS team has also had a busy and productive year. Spacecraft integration and testing (I&T) started in 

earnest for us, as did the mission simulations. We continued updating and refining our design as test results

and updated mass properties became available. 

Much of the I&T was at the subsystem or spacecraft level. Some components were reintegrated and 

retested, but the main goal was to get the ACS subsystem ready for the Comprehensive Performance Test 

(CPT). In February, we ran a series of functional tests on the spacecraft. These tests ensure that the openloop commanding of the spacecraft and the stimulating of the sensors produces the desired results. We

tested such components as the Coarse Sun Sensors (CSS), Reaction Wheels Assemblies (RWA), and the

Digital Sun Sensor (DSS), in addition to testing the Kalman filter (with the Autonomous Star Tracker 

(AST) and star tracker stimulus), Observing Mode, Delta V Mode, Sun Acquisition Mode, and our 

Safehold modes. 

April 2000 brought more functional testing on the spacecraft, the AST standalone functional and thermal 

vac tests, and four days of CPT dry run testing. This testing culminated with 8 days of continuous testing

on the spacecraft during CPT #1. The ACS team provided 24-hour coverage during the week of testing. 

In addition to spacecraft testing, there was also operations testing in the form of mission simulations. We 

did a launch simulation in the MAP SMOC with the spacecraft in the spring, and that transitioned into an

early ops sim on FlatSat. The mission sims that included maneuvers, and involved all the subsystems and 

spacecraft controllers, started in June. These simulations were a combination of nominal and contingency 

scenarios. The ACS team and the Maneuver team were involved in setting up for the simulations, 

supporting the sims while they were running, and evaluating and recovering from any anomalies 

encountered. 
Figure 2-2 

CSS (6) 

RWA (3) DSS (sun side) 

IRU (2) 

AST(2

)

The ACS team also performed other analysis and support duties during the year. In case the current 

baselined star trackers failed during testing, the MAP project decided to buy two Ball star trackers. During 

the past year, team members refined the software requirements, added a star catalog, coded software, 

modified a version of the HDS, and got ready for software testing for the Ball tracker if it was needed. 

We received new mass properties in Spring 2000 and noticed that the center of mass was out of 

specifications. This caused one of our backup thruster modes to be unstable. The fix to this problem

included software changes, and, more significantly, the addition of a bend to two of the thrusters to regain a 

backup mode. Also, we recalculated the control gains to give us the desired stability margins and 

performance with the new inertias. Figure 2-2 shows the spacecraft. 

Other work performed in FY00 included:

• Helped deliver flight software (FSW) builds. 

• FSW acceptance testing, regression testing 

• Failure Detection and Correction/Telemetry Statistics Monitor/Relative Time Sequence updates and

modifications, based on testing. 

• Supported Launch-1 Year Review. 

• Supported Pre-Environmental Review. 

• Component electrical integration and testing.

• Updated and corrected alignment document. 

• Electro-Static Discharge training for team members who are going to be working near the spacecraft. 

• Optical alignment shots during Aug. and Sept to check pre-thermal-vacuum component alignments. 

• Started work on ops contingency flowcharts. 

The public MAP home page is http://map.gsfc.nasa.gov. You can find pictures of the spacecraft, the 

instrument, and some science background and procedures. 

 

[Technical Contacts: Osvaldo Cuevas, Steve Andrews] 
2.1.3 EOS AQUA Mission (planned launch 7/2001)

During FY00, FDAB engineers finalized the FDS (Flight Dynamics System) segment of the Ground

System Requirements Document (GSRD) and boarded the Interface Control Documents (ICDs) for the

FDS to Flight Operations Team (FOT), FDS to Distributed Active Archive Center (DAAC), and FDS to 

EOS Mission Operations System (EMOS) documents. The team also continued with orbit determination 

error and tracking requirements analyses, launch window analysis, and maneuver analysis. A new ascent 

scenario was developed and nominal launch parameters were adjusted to reduce the inclination adjust 

maneuver frequency and eliminate the possibility of 3-sigma launch dispersions resulting in undesirable 

maneuvers. The FDAB continued working with the software development team on the FDS operations

concept and system specifications. An attitude and maneuver telemetry mnemonic list based on the Aqua 

Project Data Base was delivered and the team supported Project-level meetings with the spacecraft vendor, 

Principal Investigators (PIs), and other Goddard mission interfaces. Finally, the FDAB worked with 

Project personnel to define FDS participation in mission/spacecraft simulations and delivered FDS 

planning products used by the Mission Planning Team to develop nominal mission timeline for use by

other AQUA mission groups. Installation of FDS hardware in the EOS mission operations center and 

testing the FDS software was initiated.

[Technical contact: David Tracewell] 

2.1.4 TRIANA (planned launch 4/2002)

The Triana ACS team completed all preliminary design reviews last year (May '99 - July '99). The onboard control system utilizes five distinct controllers to support orbit maintenance, safing and science 

operations. One innovative feature is the gyroless Safehold control scheme, developed by Roger Chen of

K&D, which allows Triana to control rates based on the behavior of the reaction wheels. In September the 

FDAB engineers held a second peer review to cover the flexible mode stability issues that were not 

addressed in the May 1999 review. 

This year, the FDAB ACS analysis team worked closely with the software development and test teams to

implement the Triana control system. We have completed the initial ACS subsystem, taking our controller 

designs from a mathematical simulation to a real time flight system; working against an incredibly 

challenging schedule. 

This fall, all of the ACS team (hardware, software, analysis) will be supporting the spacecraft integration 

and test phase of the mission. During this activity, we will integrate our ACS subsystem with the main

spacecraft bus and perform a wide range of tests to validate the flight system. 

FDAB orbit analysis engineers made some significant strides with the Generator software used for 

trajectory design. Also, they've faced a lot of challenges with the intricate “launch a second stage from the 

shuttle” plan and the commercial, yet to be built, ground system. 

Purdue University's Generator software will be used to generate the nominal Triana trajectories to the L1

Sun-Earth libration point which require planning the Triana STS deployment and Gyroscopic Upper 

Stage (GUS) burn. The upper stage which will be used to place Triana on an L1 trajectory from a low Earth 

STS deployment orbit has dispersions that are considerably larger than those used for similar missions in

the past. GSFC's Swingby software will be used to plan the trajectory correction maneuvers. The Goddard

Trajectory Determination System (GTDS) software will be used to perform orbit determination. Orbit 

determination will be performed using tracking data received from the Deep Space Network (DSN) and the 

Universal Space Network (USN). Prior to the Triana launch the USN's tracking data will be evaluated and 

certified by CSOC personnel.
Figure 2-3 shows the Triana spacecraft. For complete details about the TRIANA mission refer to 

http://triana.gsfc.nasa.gov/home/

Figure 2-3 Triana Spacecraft

[Technical contacts: Greg Marr, Wendy Morgenstern] 

2.1.5 EOS AURA (planned launch 6/2003)

The Aura Mission (formerly called Chemistry) was established in December 1991 and will be launched in 

June 2003 on a Delta 7920 rocket from the Western Test Range. The operational mission period is planned 

for six years. The Aura Mission is composed of four complementary instruments on the EOS Common 

Spacecraft. 

The EOS Aura mission’s major science objective is the study of the chemical interactions and climate 

change in the Earth's atmosphere, focusing on the upper troposphere and lower stratosphere. The Aura

spacecraft is a 3-axis stabilized vehicle that will operate in a near-circular, sun-synchronous polar orbit at

an altitude of approximately 705 km, with ascending nodal crossings at approximately 1:45 PM spacecraft 

mean local time. 

Pre-launch flight dynamics services include mission design analysis, trajectory analysis, sensor analysis, 

and operations planning. Operational flight dynamics support services include orbit and attitude

determination validation, anomaly resolution, maneuver planning and support, sensor calibration, and 

generation of planning and scheduling data products.

During FY2000 FDAB provided the following support: Completed analysis on orbital insertion options, 

launch window definition, mission phasing strategy, spacecraft reentry prediction, and station coverage; 

made recommendations on how to get the ascending node crossing time off the uplink data, and what

information can be delivered on South Pole coverage; submitted review inputs to the Operations Concept

Document and the Mission Specific Requirements Document (MSRD); presented the flight dynamics 

support briefing to the Aura instruments Mission Operations Working Group (MOWG) at TRW,

California; held a preliminary discussion with TRW flight dynamics personnel; and gave a briefing to the 

Project Scientist on flight dynamics scenarios. 

The Aura spacecraft Microwave Limb Sounder (MLS) is a forward-looking instrument that views the 

Earth’s limb. The desire is to coordinate observations between the Aqua spacecraft instruments, looking in 

the nadir direction, and the Aura MLS. The idea is for Aura to view a point on the Earth’s limb a short 

time after Aqua has flown directly over that point. Aqua will be flying on the World Reference System

(WRS). Figure 2-4 shows an example of separation between Aqua and Aura. 

For project information about the Aura mission, please refer to http://eos-aura.gsfc.nasa.gov/
Relative Positions of Aqua and Aura

Aura MLS Limb View Follows Aqua WRS Path

 AQUA

Orbit Plane

13:30 MLT

 AURA

Orbit Planes

Aqua WRS Path

13:38 MLT

13:45 MLT

AURA 22 Min

Behind AQUA

AURA 15 Min

Behind AQUA

AURA Views Earth

Limb 7 Min Ahead 

on AQUA WRS Path

8 min

7 min

7 min

Figure 2-4 Example of Separation Between the Aqua and Aura Spacecraft 

[Technical contact: Felipe Flores-Amaya] 

2.1.6 Space Technology (ST)-5 (planned launch 2003) 

Space Technology-5 (ST-5) is the fifth mission in NASA's New Millennium program and is planned for 

launch in 2003. The purpose of the mission is to validate methods of operating several highly miniaturized 

autonomous spacecraft as a system, and test technologies in the harsh space environment near the boundary 

of Earth's magnetosphere. The program's goal is to dramatically reduce the weight, size and costs of 

missions while increasing their science capabilities. 

The GNCC is responsible for the constellation mission design and the Attitude Control System (ACS) 

design. A single miniature cold gas thruster will be used for both attitude control and orbit adjustments. 

Each of the three ST-5 spacecraft is spin-stabilized. A sun sensor and magnetometer will allow for attitude

estimation. Passive nutation damping will be provided by a fluid-filled ring nutation damper. Limitations

imposed by the spacecraft onboard computer make it necessary to design computationally simple attitude 

control algorithms based on Rhumb line spin axis precession and to depend on passive nutation control. 

[Technical contacts: Marco Concha, Jim Morrissey, Mark Woodard] 
2.1.7 Geostationary Operational Environmental Satellite (GOES)-(N-Q)

Work has begun on planning the next series of NOAA geostationary spacecraft, GOES-(N-Q). The major 

procedural difference in this new series from a flight dynamics perspective is that the spacecraft builder, 

Hughes Space and Communications Company, will perform the Launch and Orbit Raising (LOR) activities 

during the first 20-30 days of the mission. The NASA/GSFC Flight Dynamics Team will only provide a 

consulting role for the pre-launch activities plus the LOR. Following LOR, the NASA GOES FD Team

will have a more active role during the spacecraft Post Launch Testing (PLT) period before handover to

NOAA. 

The NASA GOES FD Team has participated throughout the past year in reviews of the GOES-(N-Q) 

Detailed Mission Requirements, by attending major reviews of the program and by developing a plan to

update flight dynamics tools for future GOES-(N-Q) consulting activities. Despite not having the leading 

flight dynamics role in these missions, the NASA FD Team will be ready to provide any support that will 

help to insure the success of this program. 

[Technical contact: Robert L. DeFazio] 

2.1.8 Balloon Program

Balloon Train Dynamics Studies

A key problem to improvement of balloon pointing accuracy is the understanding of the disturbances from

the several-hundreds-of-feet-long load train connecting the balloon and gondola. The train dynamics has 

been under study in the past year not only for the InFocus mission but for the benefit of other experiments 

in the balloon program as well. The train includes the recovery parachute immediately below the balloon, 

and several multi-cable sections, the largest of which is a sixty-five foot-long multi-cable ladder between 

the bottom of the parachute and the top of the gondola. Disturbances about the vertical axis are particularly 

acute because the torsional rigidity is very weak. Disturbances originating from balloon oscillations, 

rotations, altitude changes, and aerodynamics propagate through the train to disturb the azimuth pointing 

control. Attempts to isolate gondolas from this effect, usually by coupled bearings below the ladder, are 

compromised by non-linear friction and an occasional need to use a bearing motor to transfer accumulated 

angular momentum from the gondola into the train itself. 

In the past, for practical reasons, measurements of these disturbances have been hard to make. This year 

the sixty-five foot long ladder section of the balloon train was suspended at GSFC from the ceiling of a 

high bay and excited under simulated load. Laser optical measurements of azimuth angular motion were 

made. Additionally, on the InFocus Test Flight, sensors were included to make in-flight measurements of 

the attitude motion. The sensors included several magnetometers on the train/gondola plus a gyro IMU on

the gondola itself. An azimuth reaction wheel was also flown and used to excite the gondola/train motion. 

A possible byproduct of this effort will be recommendations to the standard design of the balloon train for 

all balloon payloads with an aim of lessening the torque disturbance environment from the train. 

Depending on these results there could be a test flight to qualify the design. There is also the possibility 

of developing small “piggyback” self-contained instrumentation packs to be placed on many balloon flights

in order to establish a database on the train dynamics. 

The FDAB is also studying a proposal for an additional flight prior to the InFocus flight. The purpose of

the additional flight would be to demonstrate the feasibility of arc second pointing capability on balloon

payloads. This mission would develop a gimballed pointing system to carry an existing solar telescope. 

The gimbal load bearings would be continuously rotating to lessen and linearize the unwanted bearing

friction. The pointing would incorporate arc-second accuracy attitude sensors and pointed finely in two

degree-of-freedom at a high signal-to-noise ratio source such as the sun. 
Infocus

The InFocus telescope is a nine-meter long X-ray telescope being developed at GSFC for flight on high

altitude (40 km) stratospheric balloons. Part of the InFocus development effort is improving pointing

performance. An eventual goal is to point this telescope to inertial targets within an arc-second. 

Historically, this accuracy has not been achieved on balloon payloads due to the level of torque 

disturbances, which are significantly higher than those found in an orbiting environment. Several avenues 

are being pursued with analysis, modeling, and simulations in concert with ground testing and flight

measurements. 

An Infocus Balloon test flight was instrumented for making in-flight observations of the disturbances train 

dynamics. The flight was launched in August from Palestine, Texas, and measurements were made for

several hours. The test flight did not carry the entire telescope. A second balloon flight, scheduled for

June, 2001, will carry the complete Infocus telescope. The telescope will be pointed using a standard

azimuth-elevation pointing control system with the goal of achieving pointing performance of several arcminutes. A third planned flight of the InFocus Telescope changes the pointing scheme entirely. Whereas

most pointed balloon instruments use the azimuth/elevation approach, the InFocus engineering team has 

been developing a mechanical load-carrying interface between the pointed and non-pointed portions of the 

gondola payload made up of a sealed cup/ball bearing continuously charged with oil. When uncaged at

float altitude, the low-friction, three-degree-of-freedom bearing will allow the pointed section, consisting of 

the telescope and support subsystems, to be controlled with the same attitude control components found on

satellites, e.g., reaction wheels, magnetic torquers, star tracker and gyros. The goal is to achieve arc-second 

accuracy for multiple targets. Analysis, modeling, and simulation are now underway to specify and size the 

critical control elements in the system. 

[Technical contact: David Olney] 

2.2 Operational Missions

2.2.1 EOS Earth Observing System Terra 

The EOS Terra spacecraft, formerly known as EOS AM-1, launched from Vandenberg AFB on December 

18, 1999 at 18:57:36 Z, within 20 seconds of the end of the window. Terra was placed into a nominal

injection orbit of 655 x 695 km by the Atlas IIAS launch vehicle. FDAB analysts were tasked with

planning the maneuvers to place Terra into its final mission orbit, as well as monitoring and calibrating the 

attitude control system. After successfully executing pulses of each of the thrusters and an 11 sec

calibration burn, the first of four planned ascent maneuvers was set for January 11. After only 66.7 sec of

the planned 516 sec duration, however, the burn was aborted due to a high pitch rate. Careful investigation

by the spacecraft engineers revealed the cause as a combination of impingement of the thruster plume on 

the solar array and poor knowledge of the location of the spacecraft center of mass in the onboard attitude 

controller. These problems were addressed by parking the solar array at a favorable angle for minimizing 

impingement during future maneuvers and by updating the thruster pairing matrix onboard. The GN&C

maneuver team replanned the ascent using shorter maneuvers and was able to place the spacecraft on orbit 

on February 23, 2000. 

Due to the extended amount of time that Terra spent in the injection orbit while awaiting anomaly 

resolution, the orbit inclination drifted farther than planned. Two inclination maneuvers were performed to

bring the mean local time of descending node back within the 10:30 +/- 15 min control box. The mean 

local time is now decreasing towards 10:15 am. Maneuvers will have to be performed in about 3 years to

turn the drift back around towards 10:45 again. The maneuvers executed are shown in table 2-1 below:
Maneuver Date Duration 

(sec) 

Planned 

Delta-V 

 (m/s) 

Achieved 

Delta-V 

 (m/s) 

Planned 

Thrust 

Factor 

Achieved 

Thrust 

Factor 

Hardware Test Fire 1/4/00 0.496 0.0051 0.0038 100.00% 73.37%

Hardware Test Fire 1/15/00 0.496 0.0052 0.0042 100.00% 80.89%

Engineering Burn 1/10/00 11.000 0.1166 0.1097 100.00% 94.10%

Delta-V 1 (aborted) 1/11/00 66.560 0.6902 0.6678 99.00% 95.79%

Test Burns 2/2/00 40.000 0.4109 0.3932 99.00% 94.76%

Boost Burn 1 2/10/00 60.000 0.5937 0.5862 96.00% 94.80%

Boost Burn 2 2/12/00 150.000 1.4782 1.4488 97.00% 95.07%

Boost Burn 3 2/14/00 320.000 2.8251 2.8286 95.00% 95.12%

Boost Burn 4 2/16/00 320.000 2.9186 2.9275 95.00% 95.29%

Boost Burn 5 2/18/00 320.000 2.8338 2.8408 95.00% 95.23%

Boost Burn 6 2/20/00 320.000 2.7630 2.7592 95.20% 95.07%

Boost Burn 7 2/22/00 280.000 2.3492 2.3553 95.10% 95.35%

Boost Burn 8 2/23/00 110.000 0.9089 0.9069 95.10% 94.89%

GroundTrack 1 3/14/00 21.376 0.1774 0.1762 95.00% 94.40%

GroundTrack 2 4/12/00 26 0.2177 0.2178 94.50% 94.55%

Inclination 1 4/27/00 320 2.5970 2.6103 95.00% 95.52%

Inclination 2 4/28/00 320 2.5501 2.5478 95.50% 95.42%

Table 2-1 Terra Actual Maneuver Sequence

The FDAB also planned several attitude slews needed to calibrate the attitude sensors and science 

instruments. These included the Moderate Resolution Imaging Spectroradiometer (MODIS) roll slews on

3/24/00, MODIS yaw slews on 4/25/00 and 4/26/00, and attitude calibration slews on 3/16/00 and 4/13/00. 

The calibrated IRU and star tracker provide RSS attitude estimation errors of <3 arc-sec. 

The control of the Terra attitude and maneuver functions, in addition to the entire Flight Dynamics ground

system which produces the science and housekeeping products, was handed over to the control of the Terra

Flight Operations Team on May 1, 2000. 

Note: See section 4.2.1 for a description of the TDRS Onboard Navigation System (TONS) used for Terra.

[Technical contact: Lauri Newman] 

2.2.2 GOES-L Launch Support 

The GOES-L spacecraft, the fourth of a five spacecraft series of the National Oceanic and Atmospherics

Administration (NOAA) geostationary weather satellites, was launched on May 3, 2000 aboard an Atlas-IIa

rocket from the Kennedy Space Center. After being delayed for over a year due to a Centaur rocket motor

problem, the launch was achieved with near perfection. The NASA/Goddard Flight Dynamics Team

performed the Launch and Early Orbit flight dynamics operations from both the NOAA Spacecraft 

Operations Control Center in Suitland, Maryland and the NASA/GSFC Flight Dynamics Facility in

Greenbelt, Maryland. A well-prepared team of flight dynamics personnel consisting of NASA, Computer 

Sciences, Honeywell and Space System / Loral members supported the NASA GOES Project and the 

GOES Mission Operations Support Team (MOST) from launch through the arrival of GOES-L (eventually 

renamed GOES-11) at its initial geostationary orbit location. The support consisted of 9 orbit maneuvers

and numerous attitude maneuvers, orbit determinations, acquisition data generations and gyro calibrations. 

These were achieved with great success and met all the stated requirements of the GOES Project. The final 

spacecraft in this series is scheduled for launch in mid-July, 2001. 
2.2.3 The Re-Entry of the Compton Gamma Ray Observatory 

On June 4th, 2000, the Compton Gamma Ray Observatory (CGRO) successfully entered the Earth’s 

atmosphere over the targeted Pacific Ocean. This is the first time NASA has conducted a controlled reentry of an unmanned spacecraft from Low Earth Orbit (LEO). The criticality of this GN&C intensive

operation was enhanced due to the large mass of the spacecraft, 14,000 kg (15.5 tons) post final burn, and 

the loss of two of the four orbit control thrusters soon after launch in 1991. Over the spacecraft’s nine year 

lifetime, two orbit re-boosts were done to raise the operational orbit of the spacecraft and extend it’s 

science lifetime. During the beginning of the first re-boost effort, one of the redundant attitude control 

thrusters had a major drop in performance. This thruster had since recovered to near nominal performance 

and was considered fully operational during the re-entry. Figure 2-5 shows the spacecraft. 

 Figure 2-5 The Compton Gamma Ray Observatory

In December 1999, it was recognized that a detailed plan needed to be developed and exercised for a

controlled re-entry. Initial plans included an “Implementation Phase” for developing and testing ground 

procedures, using a preliminary mission design, before a critical failure occurred. These critical failures or 

“Trigger Points” would initiate an “Execution Phase” controlled re-entry process, including a final mission

design. Before the detailed plan could be completed, the spacecraft lost the number 3 gyro. This accelerated 

the process. Procedures where developed and rehearsed using a preliminary mission design, as the final

mission design was developed. Approximately one month before re-entry, all procedures where frozen and

rehearsed with the final mission profile. The Flight Operations Team (FOT) and Applied Engineering and

Technology Directorate (AETD) sub-system engineers repeatedly rehearsed various nominal and failure 

scenarios. Failure scenarios included thruster performance and failures, gyro and battery loss, through 

ground operations breakdowns. 
The re-entry maneuver scenario consisted of an engineering burn and four 26+ minute burns each centered 

at apogee that dropped the spacecraft from it’s 510 km circular orbit to a 510 x 50 km terminal orbit. On 

May 28th 2000, 19:44:00 GMT, the engineering burns were executed. These engineering burns consisted of

short firings of the 5lb and 100lb thrusters to verify performance. Re-entry burn #1 was conducted on May

31st 01:51:05 GMT and put the spacecraft in a 510km X 350km orbit. Re-entry burn #2 was conducted on 

June 1st 02:36:52 GMT and placed the spacecraft in a 510km X 250km orbit. The final two re-entry burns 

were done on June 4 at 03:56:00 GMT and 05:22:21 GMT respectively. Re-entry burn 3 placed the 

spacecraft in a 510km X 150km orbit and re-entry burn 4 placed the spacecraft in its 510km X 50km

terminal orbit. Within 30 minutes after the end of burn 4, the spacecraft had completed its re-entry into the 

Pacific. Confirmation of the re-entry from NORAD was received at approximately 10:00:00 GMT. 

Between Burns 1, 2 and 3, the spacecraft remained in a power positive “Parking Attitude” under wheel 

control. Six minutes before the burn, the spacecraft entered Thruster Maneuver Mode (TMM) control and 

maneuvered to a “Burn minus 2 minute attitude” using the Attitude Control Thrusters (ACTs). At the burn

minus 2 minute mark, the spacecraft pitched at 1 revolution per orbit to maintain the thrusters parallel to the 

velocity vector. A command from ground transitioned the controller to Velocity Control Mode (VCM) and

fired the 100 lb Orbit Adjust Thrusters (OATs). During VCM, attitude control followed the velocity vector

by on-modulating the ACTs for pitch and yaw and off-modulating the OATs for roll. An on-board timer 

automatically switched the controller back to TMM upon completing the burn. The spacecraft attitude

continued to follow the velocity vector until a new parking attitude was loaded. After the slew to the new 

parking attitude was complete, FOT commanded the spacecraft to a wheel based Normal Maneuver Mode

(NMM). The attitude errors reduced to a level where an automatic switch to Normal Pointing Mode (NPM) 

occurred. 

After Burn 3, the perigee altitude was reduced to approximately 150 km. At this altitude, aerodynamic 

torques would cause the controller to saturate the wheels. Therefore, the spacecraft remained under thruster 

control during a final perigee pass. On the next orbit, a 30 minute Burn 4 reduced the perigee to less than

50 km over the South Pacific Ocean. Figure 2-6 shows the predicted footprint, represented as the three stars 

connected by a line in the ocean. Since the burns were of nominal performance, the spacecraft objects fell 

around the green (center) star. 

June 4th Debris Footprint

Along track footprint is 5000 km long

Cross track footprint is 26 km wide

Figure 2-6 Predicted Debris Footprint 
The objects with a low mass to area ratio, i.e. the solar arrays, fell on the upper left side of the center star 

and the objects with a high mass to area ratio, i.e. the titanium bolts, fell down stream from the center star. 

All objects fell within the yellow (first) and white (third) stars. Visual contact from an U.S. Air Force 

plane, contracted by NASA to track re-entry, verified the proper time and location of impact. Further 

analyses are continuing to verify actual impact location of the debris.

[Technical contacts: David Mangus, Sue Hoge] 

2.2.4 TRMM Tropical Rainfall Measuring Mission Reentry Planning

The TRMM scientists continue to be extremely pleased with the resolution of the science data provided by

the tight pointing performance of the Attitude Control System (ACS). This data provides key information 

of the planet’s energy balance by supplying previously unmeasurable total rainfall over the oceans as well 

as the continents. Periodic yaw and orbit raising maneuvers continue to hold TRMM at a constant 350 km

orbit altitude and the Sun on the power positive side of the spacecraft. 

The mission level and ACS design of the TRMM re-entry plan is being revisited due to the many lessons 

learned from the successful re-entry of the Compton Gamma Ray Observatory. Potential component 

failures and fuel levels are defined as “Trigger Points” and would begin the process of re-entry. 

Components that are not critical to re-entry or that have a work-around are also defined to extend mission 

life. New orbit maneuvers are being designed to incorporate the new requirements. Also, modifications to

the ACS to maintain control at the lower altitudes are being investigated through simulation. A detailed

debris analysis and impact foot print sizing is being coordinated with NASA/Johnson as well as the 

Aerospace Corporation. 

[Technical contact: David Mangus] 

2.2.5 General Space Operations Management Office (SOMO) Support

The Space Operations Management Office (SOMO), located at Johnson Space Center, is an important 

sponsor and funding source for many of the FDAB activities. This includes much of the branch’s 

technology work (covered in Section 4) as well as general mission design and concept development work

for future missions (some of the work covered in Section 3 is sponsored by SOMO). The FDAB

periodically assists SOMO in its management of mission services and operations activities, including its 

management of the Consolidated Space Operations Contract (CSOC). This may be assistance to CSOC in 

spacecraft anomaly resolution or identification of future mission services. During FY00, the FDAB

supported the following SOMO activities: 

• Technical review of progress by the Flight Dynamics Facility (FDF) to implement the real-time orbit 

determination (RTOD) system 

• Formal monthly status reviews to the Goddard Network and Mission Services Project by the FDF 

• Preparation of material to be included as part of the “SOMO Architectural Evolution Plan” which 

identifies roadmaps for future mission service upgrades and technologies 

• Preparation and review of updates to the SOMO Mission Services Catalog

FDAB management meet regularly with CSOC management responsible for the operation of the Flight

Dynamics Facility. The purpose of these meetings is not to give direction to routine operations, but to 

continue to maintain awareness of facility upgrade plans and share knowledge of future mission plans, 

technology development activities relevant to the facility, and software system upgrades. 

[Technical Contact: Tom Stengle] 
3.0 Study Mission Support

One of the primary roles of the Flight Dynamics Analysis Branch (FDAB) within the Guidance, Navigation 

and Control Center (GNCC) is to serve the science community by providing analysis of advanced mission

concepts. This includes development of orbit/attitude designs based on science constraints, evaluation of

orbit/attitude errors and attitude dynamics analysis. Members of the branch often represent “first access” 

by Earth Science and Space Science customers to the services offered by the GNCC and the Space 

Operations Management Office (SOMO). 

In FY2000, the GNC continued its participation in supporting a wide variety of future mission concepts. 

This section describes some of the analyses performed. 

3.1 IMDC Integrated Mission Design Center 

The Integrated Mission Design Center (IMDC) is a human and technology resource dedicated to innovation 

in the development of advanced space mission design concepts to increase scientific value for NASA and 

its customers. The IMDC provides specific engineering analysis and services for mission design, and 

provides end-to-end mission design products. For information about the IMDC, please refer to URL

http://imdc.nasa.gov/default.htm

Flight dynamics analysis support, in the areas of trajectory design, orbit analysis, mission planning; and

ACS design, hardware selection and performance evaluation, was provided in the IMDC for a variety of

future mission studies. Collaboration studies with the Jet Propulsion Laboratory (JPL)'s Team X were 

performed for the Ocean Surface Salinity Mission (OSSM) and Nanosat Technologies. Some of the Earth 

Science Missions supported were Radiation Belt Mapper (RBM), Ionospheric Mapper (IM), Global

Precipitation Mission (GPM), Ocean Observing Study (OOS), and Ocean Salinity Mission. The 

Interplanetary and Space Science Missions supported included Marsat, DS-5, Solar Sail, DS-5 

Constellation, and Solar Dynamics Observatory. A total of 8 flight dynamics analysts supported various 

IMDC sessions this year: Marco Concha, Steven Cooley, David Folta, Lauri Newman, Gregory Marr, 

Michael Mesarch, Josephine San, and Frank Vaughn. 

[Technical contacts: Marco Concha, Josephine San] 

3.2 Ana Lani 

The Ana Lani mission concept is from a joint team of scientists from Goddard, University of Washington,

University of Michigan and University of Hawaii. The science objective is to generate a map of the mass 

distribution in the universe to find cosmological constants. The instrument consists of 12 modular foil

mirrors, each with a 24-cm diameter and 1.7 m focal length. Although the pointing requirement is in arc 

minutes, the jitter requirement is 2 arc seconds over 20 second. 

In addition to the general support provided while the mission was studied in the IMDC, ACS personnel 

performed analysis to show the feasibility of inertial pointing with a 5 degree sun pointing constraint, and 

defined the star tracker optimal location. 

[Technical contact: Josephine San] 

3.3 Fluorescence Experiment (FLEX) 

Flex is an earth observing mission proposed by the University of New Hampshire in response to an

Announcement of Opportunity (AO). This mission will use the existing Fabry-Perot spectrophotometer to

measure chlorophyll fluorescence and to monitor globally the stress in vegetation. In support of this low 

cost mission, FDAB personnel performed a feasibility study of the minimum wheel configuration to 
perform 180 degree slews; investigated control laws for initial sun acquisition and safe mode; and carried

out attitude sensor trades to develop a minimum hardware ACS design. 

[Technical contact: Josephine San] 

3.4 Global Precipitation Mission (GPM) 

The Global Precipitation Mission (GPM) concept study was supported by the FDAB. GPM seeks to deploy 

a constellation of spacecraft that will provide global rainfall measurement coverage with a 3 hour latency. 

FDAB involvement this year has been to provide feasibility analysis for the design, deployment and

maintenance of the constellation. GPM is a TRMM follow on mission. It consists of a core spacecraft

similar to TRMM and a constellation with 6 small spacecraft in a 6-pedal orbit configuration. It is a joint 

venture of Goddard and Japanese scientists. The mission concept was brought to the IMDC three times for

different levels of study. 

In addition to the routine ACS analysis and design, FDAB personnel provided special analysis in the 

following two critical system level design issues. First, the constellation satellite instrument Lightweight 

Rainfall Radiometer (LRR) spinning at 8 rpm is located over a meter from the spacecraft center of gravity. 

This imposes a critical issue on the spacecraft jitter performance. FDAB personnel performed a detailed 

analysis on the effect of the LRR imbalance on jitter and defined the LRR offset limit based on a two-body 

model. Secondly, the core spacecraft in a 70 degree inclination orbit requires large solar arrays, which 

induce disturbance toque due to plume impingement, as well as other flexibility issues and thermal 

snapping. FDAB personnel supported the solar array design trade from the ACS perspective. 

A next generation GPM (GPM Next) study was carried out together with JPL. FDAB personnel worked

with scientists to derived ACS pointing and jitter requirement due to a finer resolution instrument. The 

IMDC and JPL investigated the newest sensor and actuator technologies to put together a lightweight, low 

power, and low cost ACS system. 

[Technical contact: Marco Concha, Josephine San] 

3.5 Joule

Joule is an X-ray astronomy mission concept in response to NASA's Small Explorer (SMEX) Program. 

FDAB engineers worked in the IMDC to provide analysis and design support to complete a mission

proposal. Special ACS trades on the maximum slew angle vs. wheel momentum and torque capabilities 

were performed to reach an optimal design in mass, power, and cost. The proposal was selected as a first

round candidate for the SMEX program.

[Technical contact: Josephine San] 

3.6 Mars Areo-stationary Relay Satellite (MARSAT)

MARSAT is a proposed Mars orbiting communication satellite for the Mars Communication and 

Navigation Infrastructure to be led by JPL. This satellite will use a 2.5-m Ka-band High Gain Antenna 

(HGA) to communicate with the earth and a 1-m x-band HGA to relay other Mars orbiting satellites and

Mars’s landers to MARSAT. Jitter requirements and recovery from anomalies are major concerns. 

FDAB personnel performed rigid body jitter analysis to show the feasibility of 1 dB beam width for the 

earth link, performed flexible mode analysis, defined transfer orbit scenarios, evaluated control mode 

design approaches, and investigated hardware lifetime to ensure a 9 year mission life. Most importantly, 

FDAB personnel investigated and defined two levels of safe mode, and derived control schemes and 

operational scenarios to search for the earth. 

[Technical contact: Josephine San] 
3.7 Living With a Star (LWS) 

The Flight Dynamics Analysis Branch has been involved in the formulation of missions for the Living with

a Star Program. The FDAB was involved with the 

generation of orbits and products related to a 

distributed system of spacecraft used to understand 

the Earth’s environment and the interaction with the 

sun. Several missions are supported in this area 

including Inner Heliopsheric missions that use a 

Venusian gravity assist to align the spacecraft into 

their respective positions. A sample of these 

missions is highlighted below. Each orbit represents

a single spacecraft after a Venus encounter. A

second concept dealt with the attainment of a Sun

Earth L3 orbit. A figure describing this orbit is also 

provided (Figure 3-1). The travel time to the L3 

location was of concern and resulted in several

options for drift away style trajectories. Figures 3-2 Figure 3-1

and 3-3 show the transfer trajectories and the final 

L3 orbit.

 Figure 3-2 Figure 3-3 

This mission concept consists of four individual missions: Solar Dynamics, Radiation Belt Mapper (RBM), 

Ionosphere Mapper (IM), and Inner Heliospheric Sentinels (IHS). Each mission has its unique objectives

and design challenges. 

Solar Dynamic is a solar observer performing continuous and high cadence observations of the full solar 

disk and coronal imaging in multiple wavelengths to improve understanding and forecasting of the Sun’s 

impact. The pointing requirement is tight, especially the jitter requirement (0.25 arc second /45 second). 

FDAB personnel investigated jitter performance using the output from the guide telescope to close the 

control loop. 

RBM is a mission to establish magnetic field properties of the radiation belt. 6 spacecraft will be stacked in 

one launch vehicle and placed in 6 highly elliptical orbits, 4 in 500 km x 6.5 Re and 2 in 500 km x 2.5 Re. 

RBM is a spinner with spin axis 15 degrees from the sun line. 

 
The IM mission objective is to monitor the global plasma environment using tomography and to study

Ionosphere density, gas properties, and magnetic and electrical fields. Eight spacecraft with 6 on one

launch vehicle and 2 on another, will be placed in low earth orbit in 3 different inclinations. 

IHS is a solar orbiting mission measuring the electric and magnetic field of the sun. Four spacecraft will be 

stacked on one launch vehicle. The spacecraft is a spinner with spin axis pointing at the sun. 

The challenging problem for RBM, IM and IHS is the separation and deployment due to the stacking of

multiple spacecraft on one launch vehicle and placement in different orbit configurations. FDAB personnel 

worked along with system, mechanical and power engineers to define feasible operations scenarios, and 

sub-optimal control design approaches. 

For RBM and HIS, having the spin axis not normal to the orbit plane but toward the sun raises issues of

appropriate attitude sensors. FDAB personnel worked with the project scientist to refine the requirements, 

trading science objective, sensor cost and control complexity. 

[Technical contact: David Folta, Josephine San] 

3.8 NGST/Nexus

The Next Generation Space Telescope (NGST) and its technology demonstration support mission called 

NEXUS were studied as part of the formulation phase. Several trajectory designs were investigated for

possible use. The support provided by the FDAB allowed the NEXUS project to understand fuel, ∆V, and

launch vehicle impacts due to trajectory design. Work performed both at the IMDC and afterward resulted 

in a clear understanding of the orbit constraints and requirements. A sample trajectory design is shown

below for this L2 co-linear Sun-Earth/Moon mission orbit (Figures 3-4 and 3-5). 

 

Figure 3-4 Figure 3-5 

The objective of NEXUS is to provide a pathfinder to demonstrate technology required for the Next

Generation Space Telescope (NGST). This includes a demonstration of lightweight, actively controlled, 

cryogenic optics for astronomical observations in the infra red region and a demonstration of disturbance 

torque isolation and ACS control with a large solar mask. Since this a L2 mission, the momentum

unloading will be achieved with thrusters and is required to execute as infrequently as possible due to tight

jitter requirements (1 arc second over 1000 second). The pitch axis tilt angle requirement, from 85 to 135

degrees from the sun line, also imposes a challenge in the ACS design. 

FDAB personnel performed detailed solar torque analysis to bound the pitch tilt angle and offset between

center of pressure and center of mass. They also developed a relationship between solar torque and the 
momentum unloading frequency and wheel momentum and torque capability requirements. Detailed rigid

body jitter analysis was performed to demonstrate the importance of flexible mode analysis and the 

necessity of disturbance torque isolation. 

[Technical contacts: David Folta, Josephine San] 

3.9 NPP 

The National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project 

(NPP) is a risk-reduction demonstration mission. Another objective of NPP is to provide a continuation of

measurements of global change parameters after EOS Terra and Aqua. FDAB personnel evaluated several

Rapid Spacecraft Development Office (RSDO) buses to converge on a suitable selection based on quick 

and simple analysis on the sensor performance, actuator capability for all modes and detailed rigid body 

jitter analysis. Per the science requirement, two levels of safe mode control were designed and an 

operational scenario for each level was defined. 

[Technical contact: Josephine San] 

3.10 Ocean Surface Salinity Mission (OSSM)

FDAB personnel provided analysis support for the Ocean Surface Salinity Mission (OSSM) concept which 

is planned to be submitted in response to the next ESSP AO. The purpose of the proposed mission is to

understand processes that control the transport, storage and exchange of fresh water between Earth’s 

atmosphere, land, oceans, and polar regions.

FDAB personnel supported the development of the mission concept by performing analysis for several

instrument design concepts to identify suitable candidate orbits that will meet the mission’s data collection

requirements. The mission concept was studied in the Integrated Mission Design Center (IMDC) to 

identify the impact of the candidate instrument designs on the spacecraft design. The IMDC study resulted 

in narrowing the field of practical candidate instrument designs, and identified key cost and complexity

trade issues for the spacecraft design that result from both fixed and rotating instrument designs. The

science team is now in the process of evaluating these issues to select the instrument design that provides

the best performance without exceeding the cost and schedule constraints for the mission. FDAB personnel

will continue to provide analysis support as the proposal moves toward submittal. 

Attitude determination and control design and analysis support for the Ocean Surface Salinity Mission 

concept was also provided. For each instrument design, trades were performed to identify the impact on 

ACS hardware mass, power and cost. Low-fidelity simulations were performed to prove the control 

concepts and control mode design options were investigated. 

[Technical contacts: Frank Vaughn, Josephine San] 

3. 11 Solar Sail

The Solar Sail mission is a solar sail technology flight demonstration. Its objectives are to validate an

integrated solar sail flight system with low volume packages, and to characterize the use of large solar sails 

for future science observations. 

FDAB personnel investigated the pros and cons of gaining 3-axis control by using a sliding mass to offset

the center of gravity or by manipulating trim tabs to offset the center of pressure from the center of mass. 

The trim tab approach is superior from an ACS perspective, but increases integration complexity. FDAB 

personnel identified limitations and concerns using solar sails as control actuators. 

[Technical contact: Josephine San] 
3.12 Constellation X

Constellation X is a study mission that uses 4 x-ray telescopes in constellation at the Earth’s L2 libration

point to study black holes and galaxy formation. The instrument consists of a large area X-ray mirror with

100-meter focal length. Therefore, the detector will be on a 100-meter long boom with 50-kg mass and 1

square meter of sun shield area, which induces large disturbance torque on the spacecraft. This year the

FDAB has provided support to the Constellation X study team in the areas of orbit determination accuracy 

and trajectory design. The baseline plan is to launch the spacecraft in pairs aboard 2 Delta IV or Atlas V 

launch vehicles. The FDAB is designing the baseline trajectory to accomplish this scenario. Also, in the 

event that the larger launch vehicles are not available in the 2008 mission timeframe, there is a study

underway to determine the feasibility of launching the 4 spacecraft on 4 Delta II vehicles, then using a 

combination of hydrazine and low-thrust propulsion to achieve the desired mission orbit. Various lowthrust options are being considered, and the FDAB is studying the available constant thrust trajectory 

options. 

FDAB personnel also assessed possible spin rates and slew constraints, studied the feasibility of spinning

optics for thermal control, pinpointed momentum unloading concerns due to significant disturbance torque 

and momentum build up, and investigated dual spin spacecraft stability criteria and performance capability. 

[Technical contact: Lauri Newman] 

3.13 Magnetospheric Multiscale Mission (MMS)

The MMS mission is a four-spacecraft Solar-terrestrial Probe designed to study magnetic reconnection, 

charged particle acceleration, and turbulence in key boundary regions of the Earth’s magnetosphere. The

mission is in its study phase. The Announcement of Opportunity (AO) for the instrument complement and 

Principle Investigator teams is expected to be released in the summer of 2001. 

The analysis tasks are directed toward characterizing the orbit dynamics of the mission, in part because 

they are needed for the AO, but also because spacecraft design is underway and subsystem engineers need 

to know them. The orbits are highly elliptical. Near apogee, the size of the tetrahedron formed by the four

spacecraft varies over the life of the mission, hence the term ‘multiscale’ in the mission name. The analysis 

tasks include demonstrating that trajectories can be designed to meet the science and engineering 

requirements, determining how to control the trajectories and the amount of propellant required to do so. In

parallel, a statement of requirements is being developed by the orbit analyst in consultation with the MMS 

study management and science team. The requirements are evolving as the analysis proceeds and 

characteristics become known. 

Little of the software needed to execute the studies is in the “off the shelf” category because this is not a 

routine mission for which analysis techniques are readily available. Software has been developed to the 

prototype level that finds and analyzes suitable trajectories. A graphics program was written to illustrate

the behavior of the tetrahedron as it changes size and shape throughout each orbit. 

For more detailed information about the mission, visit http://mms.gsfc.nasa.gov. 

[Technical contact: Charles Petruzzo] 

3.14 KRONOS

The FDAB completed an extensive mission feasibility study for the KRONOS Mission High Earth Orbit 

(HEO). This unique orbit requires a lunar swingby to increase the orbit perigee radius, lift the orbit out of 

the ecliptic plane, and rotate the line of apsides such that apogee is in the northern hemisphere. The final

HEO orbit obtained via this lunar swingby has perigee near 10 Earth Radii (RE) and apogee near lunar 

distance (≈ 60 RE). A final study report contained a detailed analysis of the HEO orbit characteristics, 
launch window opportunities, and fuel budget estimates. The results, presented to the KRONOS Project . 

Deputy PI, were well received and will be used as part of future mission proposals for KRONOS and other 

missions. The KRONOS trajectory is shown in Figures 3-6, 3-7, and 3-8. 

Figure 3-6 KRONOS Direct Transfer HEO (5 year

Mission), View in Earth – Moon Rotating Coordinates

(June 1)

Figure 3-7 KRONOS Direct Transfer HEO (Post Lunar

Encounter Apogee), View from North Ecliptic Pole in

Solar Rotating Coordinates (June 1)

Figure 3-8 KRONOS Direct Transfer HEO (Post Lunar

Encounter Apogee), View in ecliptic Plane in Solar

Rotating Coordinates (June 1)

Lunar

Encounter

Perigee

Apogee

S/C Trajectory

Lunar Orbit

Lunar

Encounter

Sun Line

(ecliptic plane)

Apogee

Sun Line

(ecliptic plane)

Lunar Orbit

S/C Trajectory

Apogee Lunar

Encounter

E

E

[Technical contact: Steven Cooley] 

3.15 Leonardo

Leonardo-BRDF is a new NASA mission concept proposed to allow the investigation of radiative transfer 

and its effect on the Earth's climate and atmospheric phenomenon. Enabled by the recent developments in

small-satellite and formation flying technology, the mission is envisioned to be composed of an array of

spacecraft in carefully designed orbits. The different perspectives provided by a distributed array of 

spacecraft offer a unique advantage to study the Earth's albedo. Over the past year the Flight Dynamics 

Analysis Branch has been investigating formation flying dynamics concerns in the context of the LeonardoBRDF science requirements. Together with scientists we have investigated the albedo integral and the 

effect of viewing geometry on science return. An approach based on Gauss quadrature has been

investigated to provide the optimal formation geometry to ensure that the value of the integral is accurately 

approximated. Secondly, strategies have been developed to achieve the desired orbit geometries within the 
constraints of orbit dynamics. Both linear and non-linear techniques have been developed for two types of

formations such that all orbits composing the formation have the same node rate and mean anomaly rate

respectively, in the presence of J2. The relative geometry afforded by each design has been investigated in

terms of mission requirements. An optimal Lambert initialization scheme has been implemented to obtain

preliminary estimates of the required Delta-V to distribute all spacecraft from a common parking orbit into 

their appropriate orbits in the formation. Finally, formationkeeping strategies have been developed and the 

associated DV's are calculated to maintain the formation in the presence of perturbations. 

[Technical contact: Steven Hughes] 
4.0 Technology Development Activities

4.1 Advanced Mission Design

The Goddard Space Flight Center’s (GSFC) Guidance Navigation and Control Center (GNCC) is at the 

forefront of libration orbit mission design, algorithm and software development, and their application to

libration point missions. This mission design encompasses the detailed analysis of attaining and

maintaining Sun-Earth/Moon libration orbits via direct and lunar gravity assist transfers. Upcoming 

missions such as the Microwave Anisotropy Probe (MAP), Triana, and the Next Generation Space

Telescope (NGST) are addressed in light of improved methods for attaining constrained orbits parameters 

and their control at the collinear libration points. New developments such as invariant manifold theory and 

optimization based on eigenvector formulation to achieve constrained orbit parameters is currently under

investigation. 

Sun-Earth libration point orbits serve as excellent locations for scientific investigations. These orbits are 

often selected to minimize environmental disturbances and maximize observing efficiency. Trajectory

design in support of such missions is increasingly challenging as more complex missions are envisioned in

the next few decades. Trajectory design software must be further developed to incorporate better 

understanding of the libration orbit solution space and thus improve the efficiency and expand the 

capabilities of current approaches. Only recently applied to trajectory design, dynamical systems theory 

now offers new insights into the natural dynamics associated with the multi-body problem. In a 

cooperative effort, the Goddard Space Flight Center’s (GSFC) Guidance Navigation and Control Center 

(GNCC) and Purdue University are working together to develop this expertise. 

Nonlinear dynamical systems theory (DST) offers new insights in multi-body regimes, where qualitative 

information is necessary concerning sets of solutions and their evolution. DST is, of course, a broad subject

area. The DST work has been performed in partnership 

with Purdue University. At Purdue University, various 

dynamical systems methodologies are included in a 

software package called Generator. In Generator, 

different types of solution arcs, some based on

dynamical systems theory, are input to a process that 

differentially corrects the trajectory segments to

produce a complete path in a complex dynamical 

model. A two level iteration scheme is utilized

whenever differential corrections are required; this

approach produces position continuity (first level), then 

a velocity continuity. An understanding of the solution

space then forms a basis for computation of a

preliminary solution and the end-to-end approximation

can then be transferred to GSFC operational software

for final adjustments for launch window, launch vehicle 

error analysis, and maneuver planning. The current

goal is to blend dynamical systems theory, which

employs the dynamical relationships to construct the solution arcs, and the mission design tool Swingby,

with its strength in numerical analysis. A sample of the trajectories calculated using Generator is shown in 

Figure 4-1. 

Figure 4-1 Trajectory Manifold

[Technical Contact: David Folta/572] 
4.2 Autonomous Onboard Navigation Systems

Increasing interest in maximizing autonomy, operations “beyond LEO,” and distributed spacecraft has 

brought new challenges for navigation systems. Addressing and anticipating new requirements has led to

technology initiatives in onboard navigation systems (ONS) using communications links, Global 

Positioning System (GPS) orbit determination, and autonomous navigation for high-Earth, libration,

gravity-assist, and deep-space orbits. 

FDAB work develops and infuses autonomous navigation technologies for Earth orbiting, libration point, 

and deep space missions. In so doing, it enables highly accurate autonomous onboard inertial and relative 

navigation for multiple satellites, which reduce the cost of autonomous navigation implementation and 

testing while increasing the efficiency of the navigation process. The work is divided into four areas: 

• GPS Navigation: Enhances the GPS Enhanced Orbit Determination (GEODE) flight software to

support all near-Earth absolute and relative navigation requirements and support its integration with

one or more prototype GPS space receivers

• Onboard Navigation Systems (ONS) using Communications Systems: Provides onboard navigation

system for non-GPS missions by integrating ONS flight software used on the EUVE & Terra

spacecraft with a Navigation Processor Board (NPB) within the communications system 

• Relative Navigation: Determines the performance of relative navigation for various mission concepts

via crosslinks and/or GPS, and develops a crosslink receiver 

• Celestial Navigation: Develops an autonomous onboard system that infuses new ground-based

navigation filter processes with onboard attitude and/or Doppler measurements 

During the past year, several of these tasks have experimented with an increasingly convergent software 

development process. These two subtasks have been able to leverage common elements in navigation filter 

design and software architecture to accomplish substantially more development and analysis combined than 

either could alone. In most upcoming work, it is planned to fold all the tasks into this software process,

thereby allowing all to share the overhead of software development and maintenance, where possible. The 

unified software package, GPS-Enhanced Orbit Navigation System (GEONS), is designed so that although

all subtasks’ capabilities are resident in the source code, only those elements that are necessary for each

specific application are switched on when the package is compiled. This design allows the package to 

remain lean and fast enough to be considered for onboard flight software applications, as well as ground

support and analysis functions. The result is a multi-purpose navigation software package that maximizes 

software reusability and maintainability, and can be easily reconfigured to a user’s needs. 

The GEONS software uses heritage code to reduce errors and assure reliability and compatibility, which is 

based on flight-proven ground-based (GTDS) and onboard (TONS) navigation systems. The software has 

been and will be verified using realistic simulation data and actual satellite data for analysis & testing, 

including actual satellite data from EUVE, Terra, Polar & the Solar and Heliospheric Observatory (SOHO), 

and hardware-in-the-loop testbeds consisting of GPS signal simulators and closed-loop orbit control 

capabilities. Measurements will currently include GPS, Federal Aviation Administration (FAA) Wide Area 

Augmentation System (WAAS), and intersatellite crosslinks, and are planned to include ground station

measurements, TDRSS, star, sun, lunar, and Earth sensor measurements, and forward-link Doppler 

measurements from command link carrier. During the past year, integrated testing between hardware and 

software has been initiated for GPS and EONS target platforms. These have included an in-house openarchitecture GPS receiver (PiVoT), ITT’s low power transceiver (LPT), and, the Motorola Navigation 

Processor Board for their 4th Generation Transponder (the latter, due to heritage interface structures, does 

not use GEONS). In its GPS-only incarnation, GEODE, the GEONS software was GSFC Software of

Year, and was NASA’s Software of Year Runner-Up. 

Web-based team collaboration, using concurrent version system (CVS) code management, has allowed a 

diversity of teaming arrangements, involving government, support contractors, universities, and licensees. 

These have included GSFC, LaRC, Computer Sciences Corporation, the University of Colorado at Boulder,

Orbital Science Corporation, Ball Aerospace, ITT, Motorola, and the Johns Hopkins Applied Physics Lab. 
These collaborations and technology transfers have lead to numerous current and planned infusion of our

autonomous navigation systems, as listed below:

 

• GEODE flight qualified for Lewis mission 

• GEODE Lite to fly on EO-1

• GEODE is being transferred to LaRC for evaluation of use by Pathfinder Instruments for Cloud and

Aerosol Spaceborne Observations - Climatologie Etendue des Nuages et des Aerosols (Picasso-CENA) 

(Earth System Science Pathfinder /ESSP) 

• Potential use of GEODE on proposed Earth Science missions (Magnetic Multi-scale Mission (MMS),

Auroral Lights) under discussion with scientists and project engineers 

• Plan to solicit missions based on Terra success for EONS 

• Current analyses using Aurora Lites, MMS for Relative Navigation mission studies 

• CelNav system can be used for ground based navigation 

• CelNav “Flight Code” may be included in Discovery mission 

• GEODE licensed to Orbital Sciences Corporation for use on OrbComm

• OSC expressed interest in embedding GEODE filter into a space-qualified version of their Ashtech 

G12 GPS receiver 

• License agreement in place with MIT/Lincoln Labs via DoD, and with Ball 

• License agreements are in negotiation with UCLA & CU/Boulder 

• Agreement with ITT for infusion into Low Power Transceiver for Shuttle demo

• EONS/GEODE potential for commercialization by Motorola in their receiver units 

• Relative Navigation potential for commercialization when integrated with crosslink receiver (APL, 

Motorola, ITT) 

• CelNav potential for commercialization when integrated with GEODE, RelNav or EONS 

Below, more detailed descriptions of the past year’s accomplishments are given for FDAB autonomous 

onboard navigation system technology. 

4.2.1 Terra Onboard Navigation - The TDRSS Onboard Navigation System (TONS)

Terra is flying an autonomous onboard navigation system to provide accurate orbital parameters to the

spacecraft in real time. The system, known as the TDRSS Onboard Navigation System or TONS, is another 

first for NASA by flying onboard navigation as the operational system for orbit solutions. 

TONS measures the Doppler data off the forward communications signal from Tracking Data Relay

Satellite System (TDRSS) and processes it in onboard software with a sequential estimation algorithm to

produce the real time outputs. The accuracy requirement for TONS is 150 meters in position and 0.16

meters per second in crosstrack velocity, 3 sigma. TONS performance has far exceeded the requirement.

TONS compares to traditional orbit determination methods to 7 meters, one sigma in position and better 

than 0.015 meters per second in crosstrack velocity. After on-orbit tuning, TONS is expected to provide 

Terra with onboard position knowledge to better than 5 meters, one sigma and 20 meters, 3 sigma. TONS 

performance was monitored during the Terra ascent maneuvers and indicated excellent recovery within the 

first few measurement updates after the maneuver. TONS filter reconvergence occurs at the beginning of 

the second post-maneuver contact. TONS has since been used as the operational solution during the 

station-keeping maneuvers, staying within the 150 meter position requirement. TONS also estimates the 

local oscillator frequency, a drag correction factor, and a TDRS measurement bias for Terra. All on-orbit 

requirements have been exceeded and navigation operations have been performed nominally. TONS data

was also used to calibrate the spacecraft clock to aid the operational clock correlation system. Terra 

scientists obtain the real-time TONS navigation solution in their ancillary data. 

[Technical contact: Cheryl Gramling] 
4.2.2 Onboard Navigation Systems Using Communication Links

The Enhanced ONS (EONS) flight software package is an integrated navigation system, which can be 

procured as an option to the existing spacecraft communications equipment. For those requiring 

autonomous navigation, EONS will be significantly cheaper and more reliable than independent software 

development and system integration efforts. EONS is derived from TONS, which flew on EUVE and 

Terra. It is being integrated into a Nav Processor Board (NPB) that will be part of Motorola’s 4th 

Generation Transponder (Figure 4-2). 

Highlights of the past year’s accomplishments are 

• TONS software successfully used to support Terra operations 

• Developed 1553 Interface Software for executive/driver, embedded processor, and Special Test 

Equipment

• Developed Improved Method for Doppler Extraction (by Motorola & Government)

• Generated simulated truth data by modifying existing program to increase validity and realistic 

qualities of the data 

• Hosted EONS code on Navigation Processor Board and performed initial testing

Fourth Generation Transponder

NPB, Top

NPB, bottom

Figure 4-2 Navigation Processor Board

[Technical contact: Cheryl Gramling]

4.2.3 Global Positioning System Advanced Concepts

Global Positioning System (GPS) satellite navigation is a proven technology that provides potential for 

low-cost autonomous satellite navigation systems. The current GPS algorithms, software, receiver 

hardware, and simulators, however, need to be enhanced to broaden the mission scope to include all nearEarth missions, such as highly elliptical orbits (HEO) and geosynchronous Earth orbits (GEO), as well as to

support relative navigation for formation flying applications. This project is enhancing the GPS Enhanced 

Orbit Determination Experiment (GEODE) flight software to support such missions, and support its

integration with one or more prototype GPS space receivers. Figure 4-3 shows the GPS signal. 
42.6 degrees

GPS

GEO

Visible Region in Primary Beam 

GPS Side Lobe 

GPS Side Lobe 

HEO

Figure 4-3 Satellite Orbital Geometry With Respect to GPS Broadcast Signal 

Highlights of the past year’s accomplishments are 

• Won GSFC Software of the Year, and Runner-up for NASA Software of the Year

• Major new GEODE release (V5) supporting relative navigation in HEO and GEO missions, and

relative navigation 

• Enhanced data simulation capabilities to support weak signal tracking analysis for HEO and GEO 

missions 

• Initial integration with PiVoT GPS Receiver & ITT Low Power Transceiver 

• Papers presented to International GPS Workshop & International Flight Dynamics Conference

concerning HEO and GEO capabilities and projected performance 

• Supported formal Peer Review for Explorers Technology Development Program

A paper was presented at the International Symposium on Space Flight Dynamics in Biarritz, France. This 

paper discusses autonomous navigation improvements for high-Earth orbiters and assesses projected

navigation performance for these satellites using Global Positioning System (GPS) Standard Positioning 

Service (SPS) measurements. Navigation performance is evaluated as a function of signal acquisition

threshold, measurement errors, and dynamic modeling errors using realistic GPS signal strength and user

antenna models. These analyses indicate that an autonomous navigation position accuracy of better than 30

meters root-mean-square (RMS) with selective availability (SA) enabled and 10 meters RMS with SA 

disabled can be achieved for high-Earth orbiting satellites using a GPS receiver with a very stable 

oscillator. If the GPS receiver’s signal acquisition threshold can be reduced by 5 dB-Hertz to track weaker 

signals, this accuracy improves to better than 20 meters RMS with SA enabled and 8 meters RMS with SA 

disabled. Figures 4-4 and 4-5 show the RMS error margins. 

5

10

15

20

25

30

35

40

Baseline No SA Iono Delays 5% SRP

Error

Baseline No SA Iono Delays 5% SRP

Error

35 dB-Hertz Threshold 30 dB-Hertz Threshold 28 dB-Hertz Threshold

RMS Position Error (meters) RMS Clock Error (meters)

0

Figure 4-4 Comparison of Steady-State Time-Wise Ensemble RMS True Errors for HEO 
5

10

15

20

25

30

35

Baseline No SA Iono

Delays

3% SRP

Error

30-day

EOPs

Baseline No SA Iono

Delays

3% SRP

Error

30-day

EOPs

35 dB-Hertz Threshold 30 dB-Hertz Threshold 28 dB-Hertz Threshold

RMS Position Error (meters) RMS Clock Error (meters)

Figure 4-5 Comparison of Steady-State Time-Wise Ensemble RMS True Errors for GEO 

0

[Technical contact: Russell Carpenter] 

4.2.4 EO-1 Global Positioning System (GPS)

The Earth Observing–1 (EO–1) spacecraft launch is currently planned for November 16, 2000 from

Vandenburg Air Force base. Since the integration of the Tensor GPS receiver to the EO-1 spacecraft in

March of 1999, subsequent tests demonstrated that the integration was successful and that the spacecraft 

was ready for thermal vacuum testing. The spacecraft was then moved from the construction site at 

SWALES into the Goddard’s building 7 test facility. The first series of thermal vacuum tests were run in 

November of 1999. During these tests, the GPS receiver was exposed to and operated in no less than two 

cold soak plateaus each lasting a minimum of 24 hours and two at hot soak plateaus of similar duration.

During these tests, the GPS flight system performed flawlessly. However, the same could not be said of the 

ground support equipment (GSE). Intermittent data dropouts experienced during testing were later found to 

be a direct result of the poor RF characteristics of the GSE cables used to bring GPS signals from the 

rooftop antenna to the test chamber. The flight system was deemed ready to fly and the GSE would be 

upgraded for any subsequent tests. Figure 4-6 depicts the GPS receiver. 

Figure 4-6 EO-1 GPS receiver 

By April 2000, the EO-1 ground system was upgraded to allow the GPS flight receiver to be warm started 

from the MOCC. In a cold start, the receiver is powered on, configured for orbital operations and allowed 
to acquire a navigation fix with no further interaction required. This type of self acquisition can be very 

time consuming (on the order of hours) and may not always be practical in an operational environment. For 

this reason, it was deemed necessary for the ground system to be capable of executing a warm start of the 

GPS receiver. In a warm start, the receiver is powered on, configured for orbital operations and provided a 

GPS almanac file (position data of the 32 GPS satellites) and an ephemeris file (position data of the EO-1 

spacecraft). Given this information, the GPS receiver can begin acquiring GPS satellites and generating 

navigation solutions in only a few minutes. Warm staring the receiver from the MOCC would require 

software to allow generation and uplink of almanac and ephemeris data. This is a capability even the 

manufacturer of the GPS hardware does not possess. Since thermal vacuum testing would be employing 

the MOCC software to communicate with the EO-1 spacecraft, this newly developed capability would also 

be tested during the second set of thermal vacuum tests. 

From a thermal vacuum testing standpoint, the GPS tests were an unqualified success. Not only did the 

receiver perform as expected (just as it did during the first set of TV tests), but the new and improved GSE 

proved reliable as well. This new and improved GSE could now be used at the launch pad for any testing 

requiring real time GPS data. After a few minor bugs were corrected, the MOCC software was proven to 

enable a flight operator to download a GPS YUMA almanac file from the Coast Guard navigation web site

(where all GPS almanacs are archived) and construct a flight load from the data. In a similar manner, the 

MOCC was enabled to employ ground orbit data to generate an ephemeris load to the GPS receiver. Given 

these data, the receiver was able to acquire GPS satellites and begin producing navigation fixes in a 

relatively short time (several minutes). This capability was tested against the flight GPS using many

different YUMA files while receiving GPS inputs from first the actual constellation then from the GPS 

constellation simulator. 

Finally only one difficulty remained. The MOCC ground system was unable to translate atypical (Bus-B)

housekeeping telemetry downloads. Routine GPS navigation solutions are fed to the EO-1 ACS via the

main telemetry bus (Bus-A). This includes position, velocity and time data. From these data, the EO-1

ACS is able to create the reference frame against which attitude errors are measured and corrected. Any

other (housekeeping) data from the GPS receiver must be telemetered to the ground via Bus-B. Once on the

ground, the outputs from the receiver (i.e. signal strength, configuration status and so forth) must be 

converted from the format they are captured in into engineering units. This was not possible with the 

software in the MOCC. To correct this shortcoming, an in-house software tool (PKTVIEW – developed by

Dr. Charles Campbell of the FDAB) was updated and modified so it could be run in the MOCC. With this 

tool and the documentation on the receiver itself, operations personnel now have all the capabilities and 

insight into the GPS receiver necessary to accomplish the EO-1 mission. EO-1 GPS is now ready for the 

expected November 16 launch. 

[Technical Contact: David Quinn] 

4.2.5 Relative Navigation

The goal of this task is to provide formation flying missions with a real-time capability to determine the 

relative positions of the individual segments by using tracking data measured from crosslinks and/or GPS. 

Highlights of the past year’s accomplishments are: 

• GEODE software modifications to allow multiple simultaneous solutions with multiple data types, to

mix GPS and crosslink data; time and frequency models 

• Paper presented to International Space Flight Dynamics Conference 

• Implemented upgraded clock model

A paper was presented at the International Symposium on Space Flight Dynamics in Biarritz, France. This 

paper discusses autonomous relative navigation performance for a formation of four eccentric, mediumaltitude Earth-orbiting satellites using Global Positioning System (GPS) Standard Positioning Service 

(SPS) and “GPS-like” intersatellite measurements. The performance of several candidate relative 

navigation approaches is evaluated. These analyses indicate that an autonomous relative navigation 
0

5

10

15

20

25

30

With SA Without SA 99.8% with SA 94% with SA 55% with SA 99.8% without SA 55% without SA

RMS (meters) Maximum (meters)

Absolute Position Error Relative Position Error

Percent of GPS SVs in Common

Figure 4-7 Absolute and Relative Steady-State Time-Wise Ensemble True Position Errors 

Using Filtered Solutions with GPS Measurements

0

2

4

6

8

10

12

14

0 0.5 1 1.5 2 2.5

Elapsed Days 

Absolute Error

Relative Error

Total RMS Position Error (meters)

3

0

2

4

6

8

10

12

14

0 0.5 1 1.522.5

Elapsed Days

Absolute Error

Total RMS Velocity Error (millimeters per second)

Relative Error

3

Figure 4-8 Absolute and Relative Ensemble True RMS Position and Velocity Errors With SA Disabled

Using Filtered Solutions with 99.8% GPS SVs in Common

position accuracy of 1 meter root-mean-square can be achieved by differencing high-accuracy filtered 

solutions if only measurements from common GPS space vehicles are used in the independently-estimated

solutions. Figures 4-7 and 4-8 show the position and velocity error margins. 

[Technical contacts: Russell Carpenter, Cheryl Gramling]

4.2.6 Celestial Navigation

Celestial navigation of spacecraft opens up high earth, libration point, and deep space missions to 

autonomous navigation. Celestial navigation is a simulation/navigation system that uses onboard attitude

sensor measurements, new algorithms, and high fidelity environmental and filter models to accurately 

determine the spacecraft state. Autonomous navigation has the potential both to increase spacecraft 

navigation system performance and success and to reduce total mission cost. Figure 4-9 shows navigation 

scenarios. 

Highlights of the past year’s accomplishments are 

• Completed Kalman filter design

• Completed analysis of ingested simulated and real spacecraft tracking and attitude data and compared 

to ground based solutions

• Paper presented to International Flight Dynamics Conference 
Ground-Based Navigation Scenario Autonomous Navigation Scenario

Figure 4-9 Navigation Scenarios 

[Technical contacts: David Folta, Cheryl Gramling]

4.3 Formation Flying Technologies

4.3.1 EO-1 Formation Flying Experiment 

The formation flying requirement of EO-1 is to maintain a 1-minute separation between EO-1 and Landsat7 with EO-1 following the Landsat-7 ground track to a tolerance of +/- 3 km tolerance, approximately 6

seconds. This translates into an along-track distance of approximately 450 km with tolerance of 50 km. 

The mapping of this requirement into a formation flying requirement is to place a constraint on the initial 

separation between the two spacecraft, and maintaining that separation. Using the formation flying 

algorithms developed by GSFC simulations have shown that formation flying requirements can be easily

met by a wide margin. By performing this spacecraft separation maintenance, pair scene comparisons 

between Landsat-7 and E0-1 can be made. Figure 4-10 shows two spacecraft in formation flying 

configuration. 

The primary objective of enhanced formation 

flying is to demonstrate onboard autonomous 

formation flying control of the EO-1 spacecraft 

(using the AutoCon system) with respect to the 

Landsat-7 spacecraft. A secondary goal is to

enable the collection of correlated science

measurements and to demonstrate significantly 

improved space science data return through 

near-simultaneous observations. All algorithms

must conform to AutoCon specifications in

order to allow uploading during the extended

mission. Individual algorithms are invoked

through ground commanding of an AutoCon

control mode switch. 

 Figure 4-10 Formation Flying 

Satellite Op eration s Ce nter

P r ed ic ted

P os ition Da ta

6

Tr ack in g

 Data

4

2 3

1

S /C to S un

dir e ct ion al

 m e asur e m e nt

Ea rth

S /C to E a rth

dire c tiona l

 me asur em ent

G roun d Sta tion

 to S /C D opple r

 m e a sure m ent
The EO-1 maneuvers will be computed onboard under a single system architecture called AutoCon which

employs separate maneuver decision/design modules or algorithms. AutoCon will control execution of the 

modules through an onboard mode switch, and perform constraint evaluation via fuzzy logic control.

The enhanced formation flying technology demonstration will be fully validated during the EO-1 mission. 

In this way, science taken during the first year with autonomous onboard formation flying control

operating can be compared to previous ground operations. Likewise, operations costs with and without

onboard formation flying control can also be compared. Figure 4-11 shows the observation overlaps.

The core AutoCon flight control architecture required to support all enhanced formation flying (EFF) 

algorithms during the extended EO-1 mission was developed, integrated with the ACS, and placed onboard 

the spacecraft during the past year. Validation of the core AutoCon architecture will occur during the first 

year of EO-1 operations. The core AutoCon flight control software must be integrated with the ACS and 

the spacecraft prior to launch to reduce the risk and the amount of software being uploaded later in the

mission. Formation flying control algorithms will be uploaded and executed under the AutoCon flight

control software during the extended mission. 

The AutoCon flight control system will need data from additional sensors and spacecraft subsystems such

as propulsion data, ground track data, and navigation and attitude data. It will then be possible to

autonomously generate, analyze, and execute the maneuvers required to initialize and maintain the vehicle 

formation. Because these calculations and decisions can be performed onboard the spacecraft, the lengthy

period of ground-based planning, currently required prior to maneuver execution, will be eliminated. The 

proposed system will also be modular so that it can be easily extended to future missions. Furthermore, 

the AutoCon flight control system is designed to be compatible with various onboard navigation systems 

(i.e. GPS, ONS, or an uploaded ground-based ephemeris). The existing automated maneuver planning tool

(AutoCon) will be modified for onboard autonomous formation flying control to demonstrate that improved

science data return can be achieved by correlating nearly simultaneous data. This will be accomplished by 

having the flight control system plan a maneuver that places EO-1 within 1 minute of separation from

Landsat-7 and then maintains that separation to a tight tolerance of 6 seconds for an extended period of

time. 

The EO-1 software test validation certified that all software requirements have been properly implemented 

and that Phase-1 of the Enhanced Formation Flying (EFF) software meets all operational objectives. The

core AutoCon flight control software was qualified by executing a series of test plans, test data, and test 

scenarios. The results of each stage of validation was checked and documented. These activities were 

performed by both the developers of AutoCon and the EO-1 ACS software engineers. Quality assurance 

was integrated into each stage. 

 

 

 

Velocity

FF Maneuver

Formation Flying Spacecraft

In-Track Separation (Km)

Observation Overlaps

Radial Separation (m)

Ideal FF Location

Nadir

Direction

I-minute separation

in observations

Figure 4-11 Observation overlaps 

[Technical Contacts: David Folta, David Quinn] 
4.3.2 Integration of a Decentralized Linear-Quadratic-Gaussian Control into

 GSFC’s Universal 3-D Autonomous Formation Flying Algorithm 

A decentralized control was investigated for applicability to the autonomous formation flying control

algorithm developed by GSFC for the New Millenium Program Earth Observer-1 (EO-1) mission. This

decentralized framework has the following characteristics: 

• The approach is non-hierarchical, and coordination by a central supervisor is not required.

• Detected failures degrade the system performance gracefully. 

• Each node in the decentralized network processes only its own measurement data, in parallel with 

the other nodes. Although the total computational burden over the entire network is greater than it 

would be for a single, centralized controller, fewer computations are required locally at each node. 

• Requirements for data transmission between nodes are limited to only the dimension of the control

vector, at the cost of maintaining a local additional data vector. The data vector compresses all 

past measurement history from all the nodes into a single vector of the dimension of the state. 

• The approach is optimal with respect to standard cost functions. 

The current approach is valid for near time-invariant systems only. Similar to the GSFC formation flying

algorithm, the extension to Linear Quadratic Gaussian (LQG) time-varying systems requires that each node

propagate its filter covariance forward (navigation) and controller Riccati matrix backward (guidance) at 

each time step. Extension of the GSFC algorithm to non-linear systems can also be accomplished via 

linearization about a reference trajectory in the standard fashion, or linearization about the current state 

estimate as with the extended Kalman filter. 

To investigate the feasibility of the decentralized integration with the GSFC algorithm, an existing 

centralized LQG design for a single spacecraft orbit control problem was adapted to the decentralized 

framework while using the GSFC algorithm’s state transition matrices and framework. The existing GSFC 

design uses both reference trajectories of each spacecraft in formation and by appropriate choice of 

coordinates and simplified measurement modeling is formulated as a linear time-invariant system. Results 

for improvements to the GSFC algorithm and a multiple satellite formation were addressed. The goal of 

this investigation was to progressively relax the assumptions that result in linear time-invariance, ultimately 

to the point of linearization of the non-linear dynamics about the current state estimate as in the extended 

Kalman filter. Figure 4-12a/b Represents a sample of trajectories 

Chase

Initial Control

Initial

Chase

Desired

Control Spacecraft, Chase Target Target

Chase

Initial

Chase

Transfer

Contro

spacecraf

orbit

Chase

spacecraft

desire

orbit

-0.010

-0.005

-0.000

0.005

0.010

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

Radial Versus Along Track Separation

RadialSeparation (Km)

AlongTrackSeparation (Km)

Formation Target

Formation Reintialization

Trajectory

Formation Evolution

Figure 4-12a/b Sample of trajectories 

[Technical contacts: David Folta, J. Russell Carpenter, David Quinn] 
4.3.3 Tethered Formation Flying Examined for SPECS 

The Sub-millimeter Probe of the Evolution of Cosmic Structure (SPECS) is a bold new mission concept 

designed to address fundamental questions about the Universe, including how the first stars formed from

primordial material, and the first galaxies from pre-galactic structures, how the galaxies evolve over time, 

and what the cosmic history of energy release, heavy element synthesis, and dust formation is. Ideally, a 

very large telescope with an effective aperture approaching one kilometer in diameter would be needed to

obtain high quality angular resolution at these long wavelengths, however this approach proves to be too 

expensive and therefore impractical. Instead, a spin-stabilized, tethered formation is one possible 

configuration being considered requiring a more advanced form of formation flying controller, where 

dynamics are coupled due to the existence of the tethers between nodes in the formation network. To this

end an investigation into the dynamics and control of multiple tethered spacecraft systems was launched. 

Figure 4-13 depicts the SPECS spacecraft. 

Figure 4-13 SPECS spacecraft 

The FDAB analysis effort was divided into three separate tasks. Task-1 involved cooperation with the

Naval Research Lab in the development of the equations of motion for a rotating multi-tethered system 

applicable to the study of fundamental dynamic characteristics of a deep space interferometer concept. The 

system is assumed to be comprised of a central rigid body from which emanate n-tethered end-masses 

forming a symmetrical planar arrangement in the nominal configuration. The concept system is intended to 

execute planar rotation, to deploy and/or retract the tethered end-masses, and be capable of re-orienting the 

spin axis. Accordingly, the mathematical model must allow full three dimensional motion of all the 

constituent elements. This has been accomplished and the final report and corresponding FORTRAN model 

are undergoing examination. 
Working with the University of Texas at Austin, Task-2 examined key linear and non-linear control 

methodologies which may prove applicable to the problem of tethered formation flying, specifically gainscheduled controllers, Lyapunov based non-linear controllers and/or robust adaptive controllers. The object

was to build upon the dynamic development from Task-1 in order to create a core dynamics and control 

model, which permits iteration and expansion while maintaining the primary thrust of the tethered 

formation. The ultimate goal for this task was to develop a set of control laws centered on the core model

from Task-1. This will serve as a first order tool for examining the dynamics and control of a variety of

design configurations. 

Finally, the main objective of Task-3 was to cooperate with personnel from Payload Systems Inc. to

examine possible configurations using the Generalized Information Network Analysis (GINA) framework 

developed at the Massachusetts Institute of Technology and conduct preliminary configuration trade 

studies. Here trades such as reel-in-rate versus rotation rate versus aperture diameter were considered as

well as angular momentum management and re-targeting and rotation rate versus aperture diameter versus

tether tension. Many possibilities were examined in an effort to conduct a "broad-brush" analysis to get a

high level understanding of the issues involved with each as well as understand the favorable regions in the

trade space. This work has been of immeasurable help by providing insight into the most likely design

parameters for this complex spacecraft system. As the configuration trades narrow the trade space, the 

dynamics and control models of Tasks-1 & 2 will be employed to evaluate the overall feasibility of large 

multi-tethered spacecraft formation for interferometric and/or large aperture science missions such as 

SPECS. While detailed design work is expected to take years, this is seen as a crucial first step to making

such mission a real possibility.

[Technical contact: David Quinn] 

4.4 Attitude Determination and Modeling Techniques

4.4.1 SKYMAP 

Completion of the SKY2000 Version 3 Master Catalog (MC). The delivery of SKY2000 Version 3 MC

in June of 2000 marked the global replacement of the Henry Draper (HD) spectral type data in the

SKY2000 catalog, along with the global replacement of the photovisual (ptv) and photographic (ptg) 

magnitude data. Access to the improved spectral and magnitude data in the MC resulted in a significant

improvement in magnitude estimation capability for mission star catalog generation. The SKY2000

Version 3 MC now contains 299,160 entries, an increase of 61 over the 299,099 entries in SKY2000 

Version 2. SKY2000 Version 3 contains 273,202 photovisual magnitudes (an increase of 62,280 or 29.5% 

from Version 2) and 255,362 photographic magnitudes (an increase of 73,078 or 40.1% from Version 2). 

Many other individual corrections to MC data were also made during this period. 

Run Catalog Consultation. The FDAB provided star catalog consultation for several current and future

missions including: MAP (Run Catalog checklist, 11/99; catalog requirements meeting, 01/00), Terra (CT601 performance analysis, 12/99), VCL (Run Catalog generation, 02/00), Landsat-7 (Run Catalog content

discussion and generation, 03/00), and R-XTE (OBC catalog analysis and update). 

General SKYMAP Consultation. General information and support was provided to GSFC Projects, 

Universities, and other external users of the SKY2000 MC data and products. Some examples of

partnering during this fiscal year include: Lockheed-Martin (flux to magnitude conversion algorithms, 

04/00), U. Texas (Austin; radial velocity data & availability, 05/00), SOHO Run Catalog Generation

(11/99), Landsat-7 Run/Supplemental Catalog Generation (06/00). 

[Technical contact: David Tracewell] 
4.4.2 Attitude Sensor Performance Analysis

For this fiscal year horizon radiance modeling was studied as well as gyro modeling from mission 

experience. Using TOMS data, the following horizon radiance modeling data was obtained (Figure 4-14). 

Variations in colors/shades correspond to horizon height errors related to latitude and month. 

-8 0

-6 0

-4 0

-2 0

0

2 0

4 0

6 0

8 0

Latitude (deg)

June Sept. Dec. March

Horizon Height (k

m) 2 5

3 0

3 5

4 0

4 5

5 0

5 5

Figure 4-14 Horizon radiance modeling 

Long-term gyro performance for a variety of missions was also evaluated over the past year. The results of

this analysis indicate a long term linear change in biases. An example of this trend can be seen in gyro data 

from the Rossi X-Ray Timing Explorer (RXTE) (Figure 4-22):

RXTE Gyro Bias Correction

-300

-200

-100

0

100

200

300

400

2/5/96 3/26/96 5/15/96 7/4/96 8/23/96 10/12/96 12/1/96 1/20/97 3/11/97

Date

Arcsec/Hour

X

Y

Z

Figure 4-15 Gyro performance

[Technical contact: Rick Harman] 
4.4.3 Advanced Attitude Determination and Sensor Calibration Techniques

A new gyro calibration utility was developed which has proven to be faster and more accurate. The old

algorithm involved estimating attitudes before and after each maneuver followed by combining that data 

with the spacecraft gyro data in another algorithm to estimate the gyro parameters. This proved to be a 

cumbersome process with very little flexibility. A new process was developed this year to estimate the 

attitude and gyro parameters in one utility. Besides the timesavings involved in only running one utility, 

the ability to include non-sequential batches of data has been included. Thus, more batches of data from a 

variety of different times can be included in the estimation process allowing for greater observability of the 

estimation parameters. This utility has been flight tested on both the TERRA and WIRE data. The WIRE 

gyro in particular demonstrates what gyro calibration can do for a mission. Figure 4-16 demonstrates the 

typical attitude propagation errors though maneuvers before and after gyro calibration:

Figure 4.16 Attitude Propagation Errors Before (left plot) and After Gyro Calibration (right plot) 

The overall RSS error at the end of the maneuvers was 0.5 degrees before calibration and 0.0024 degrees (9

arc-seconds) after calibration with the new utility. 

In addition, GNCC was directed to assist in reconstructing the HST rate profile during its gyro failure, 

which occurred 5 weeks before a shuttle-servicing mission. The gyro failure mode known as “Zero Gyro

Mode” consisted of pointing the HST z-axis at the sun using sun sensors and inducing a small rotation rate

about the z-axis. During orbit night all actuator commands are disabled, and the spacecraft drifts with the 

sun line rotation providing some dynamics rigidity. The goal is to keep the spacecraft z-axis close to the 

sun line when HST enters orbit day. The results shown in Figure 4-17 were obtained using HST 

magnetometer, reaction wheel, torquer bar, and remaining gyro data. 
0 2 4 6 8 10 12 14

x 10

4

-0.25

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

Figure 4-17 HST Estimated Rates Using Only Magnetometer and Sun Sensor Data

he y-axis of the plot contains the estimated rate in degrees/second, and the x-axis is in seconds. The orbit 

night periods can be picked out in the above plots by looking at the negative peaks in the rates. During

orbit night the spacecraft is rotating about the z-axis with an approximate constant rate with actuators being 

turned off. When the computed rate was compared to the rate from the remaining gyros, an excellent fit 

was obtained. 

[Technical contact: Rick Harman] 
5.0 Branch Infrastructure

5.1 Flight Dynamics Tool Program

Flight dynamics analysis services can only be provided with a suite of specialized analytical tools. The 

branch currently uses a large complement of commercial and in-house developed software tools. Missions 

such as LISA, Marsat, MAXIM, Constellation X, GEC, MMS and Leonardo continue to drive the need for 

improved modeling and computational techniques. Thus, the tools program provides a means of enabling

new missions. 

The majority of the effort in the Flight Dynamics tools program supports the development and

enhancement of software tools for advanced mission planning activities. Flight Dynamics Tools activities 

are conducted in direct response to customer (Earth Sciences Enterprise, Space Sciences Enterprise, Human 

Exploration and Development of Space Enterprise) requirements. These tools are required in support of all 

aspects and phases of mission formulation, design, implementation, and operations. These tools are also

required in support of the flight dynamics technology development activities associated with the Flight

Dynamics Analysis Branch . Newly developed tools are also used in the Goddard Integrated Mission

Design Center (IMDC). Thus, the tools program performs the following:

• Implementation of new computational techniques in existing mission planning and analysis

tools 

• Development of new mission planning and analysis tools (based on needs identified for future 

missions) 

• Error correction 

• Configuration control of FDAB tools 

The institutional software tools used by the Flight Dynamics Analysis Branch are upgraded to use results of

various technology initiatives in order to improve capabilities and responsiveness to the Earth Science and

Space Science customers. An example is the research into dynamic system theory for improved trajectory 

targeting capability. This and other basic research is supported through the SOMO technology program

and cross enterprise programs. 

The FDAB tools program requires contractor services to assist with software configuration control. 

Support is also provided to commercialization efforts. This includes packaging of software approved for

external licensing. Currently, software available for licensing includes: 

• Goddard Trajectory Determination System (GTDS) 

• Attitude Determination Error Analysis Systems (ADEAS) 

• Orbit Determination Error Analysis System (ODEAS) 

• Swingby Trajectory Design Program (SWINGBY) 

• General Maneuver Program (GMAN) 

• Multimission Three-Axis Stabilized System (MTASS) 

• Multimission Spin-Axis Stabilized System (MSASS) 

• GPS Enhanced Orbit Determination (GEODE) 

• Elements Conversion Program(ELCONV) 

• Guide Star Occultation Utility (GSOC) 

[Technical Contact: Thomas Stengle]

5.2 GNCC Flight Dynamics Data Lab 

The Flight Dynamics Lab completed its initial configuration during FY2000. This lab is used for the 

development, test, integration, and operation of software systems as well as analysis for the performance of 
flight dynamics functions for operational and new missions. Installation of servers and migration of branch

personnel was completed. Several new computers were installed. In addition to the servers, the lab now

houses two Sun Ultra 60 workstations, two HP workstations, 6 Dell dual processor workstations, an online 

storage device with approximately 700GB of usable storage as well as printers, scanner, overhead

projector, voice and video equipment. Branch commercial software licenses are now managed by the

servers and the online storage device provides the users with regular tape backup capability. Addition of 

this equipment enabled FDAB personnel to do advanced mission analysis, mission system prototyping and

test. The CGRO Re-entry was supported using two of the Dell machines and the TRIANA mission

maneuver planning is scheduled to be supported from the lab. The TRMM dynamics simulator was

transferred to the FD Lab. The FD Lab also houses the on-line documentation server and the GNCC and 

Branch WEB page servers. 

The FD Lab provided consultation to the GNCC International Telecommunications Satellite Organization

(ITSO) for security configuration and monitoring. The lab security plan will be used as a model for the 

other area within GNCC.

Plans for the coming year call for the FD Lab to implement a wireless network capability, upgrading the 

internal lab network and testing of upgraded operating systems and networking configurations. The FD

Lab will also provide voice lines for the Expedition One support. 

[Technical contact: Sue Hoge] 

5.3 Branch Library 

During FY00, the FDAB implemented a new online technical library. This library uses the commercial tool

Docushare, which is a web based tool that can catalog, store, search and access a wide variety of files. 

Initially, the library was populated with various document files created over the last several years, which

contain technical reports from various branch technology research activities, presentation slides from many

spacecraft project technical reviews, and software documentation. The library continues to be expanded and 

will contain all future analysis reports, future mission studies, software specifications and control system

documentation created by the branch. General spacecraft reference documentation will also be placed in the 

library to enable branch engineers to quickly access spacecraft information during anomaly investigations. 

Access to the library is controlled to protect proprietary and International Traffic In Arms Regulation 

(ITAR) restricted data. In the future, the library will also contain selected flight data. 

[Technical Contact: Catherine Waltersdorff] 

5.4 Employee Handbook 

The initial draft of the FDAB Employee Handbook was completed. Authored by more than a dozen

members of the FDAB staff, the purpose of the handbook is to document for all branch employees a 

standard set of procedures for supporting flight projects, future mission analysis activities and technology 

projects. The handbook also clearly documents various administrative procedures important to the branch 

(for example, procedures for technical paper approval). While not yet complete, future updates to the 

document in FY01 will include detailed technical guidelines for control system design and trajectory 

design. The handbook will also capture flight dynamics "best practices." 

[Technical Contact: Thomas Stengle]
6.0 Interagency Activities

6.1 GSFC Standards Program

The FDAB supports the GSFC standards program and the Consultative Committee for Space Data Systems 

(CCSDS). 

The GSFC standard program aims to expand the scope of best practices, and to develop an agencyendorsed database of preferred technical standards for NASA 

The Consultative Committee for Space Data Systems (CCSDS) is an international organization of space

agencies interested in mutually developing standard data handling techniques, to support space research

conducted exclusively for peaceful purposes. 

The CCSDS Sub-Panel P1J is specifically chartered to investigate and recommend Navigation Data 

standards. P1J has a membership of representing from several international agencies. The work of P1J is

accomplished primarily at workshops, conducted at least twice a year, at facilities coordinated by the

hosting member agency. The main task of P1J is to generate documents defining the preferred standards 

for the exchange of navigation data. The latest workshops were conducted at Annapolis, Maryland, in

May, and at the European Space Agency (ESA) Vilspa facility, Spain, in October. 

Currently P1J is working on a green book, for navigation definitions and conventions, with projected

completion on December 2000. Response to the CCSDS Proximity-1 Space Link Protocol, Red Book, will 

be provided through a red book, generated by P1J, providing recommendations for navigation data

exchange in support of proximity operations. New CCSDS red books on recommendations for orbit, 

tracking, attitude, proximity ops, environmental models and astrodynamic constants will be developed in

the future. 

For information about CCSDS and the GSFC standards program please refer to

http://www.ccsds.org/ 

http://joy.gsfc.nasa.gov/GTSP/

[Technical contact: Felipe Flores-Amaya] 

6.2 Mars Climate Orbiter Mishap Investigation 

A service provided by the Flight Dynamics Analysis Branch is to support the peer reviews and

investigation reviews of missions. Last year the Mars Climate Observer (MCO) unfortunately failed in its 

Mars mission due to an underlining unit conversion error. As part of the MCO mishap board, the FDAB

supported the investigation by providing leadership in the trajectory design, navigation, and control areas. 

The FDAB participated in the MCO Mishap board with the MSFC Center Director, NASA HQ, and 

independent individuals. The findings for this mishap were released under a document that not only

provided information regarding the mishap, but also established new guidelines for future NASA mission. 

It detailed the expectations of all future missions with respect to mission success. The findings addressed 

the use of faster, better, cheaper in the context of mission success and mission safety. Copies of this 

document can be obtained through NASA HQ. 

[Technical contact: David Folta]
7.0 Outreach Activities

7.1 Educational Outreach: International Space University 

A part of the FDAB effort for educational outreach, a student of the International Space University (ISU) 

was selected to participate in analysis with the FDAB in order to fulfill his requirements for a Masters 

degree. A part of his 10week effort, a Matlab demonstration tool was developed to study formation-flying

concepts at the L1 LaGrange point. The student, Mr., Christoph Wagner of Germany, completed an initial 

investigation that included libration orbit generation, linear Quadratic Regulator controls, and formations. 

A sample of his Matlab work appears in Figure 7-1a/b. 

Figure 7-1a/b Libration Orbit Control, About an Orbit and Relative Motion 

[Technical contact: David Folta]

7.2 SAMPEX University Operations

The University of Maryland Aerospace Engineering Department completed its first full year of sole 

responsibility for flight dynamics support of the Solar Anomalous and Magnetospheric Particle Explorer 

(SAMPEX) spacecraft. In this role, a team of University of Maryland undergraduate and graduate students 

provides routine spacecraft orbit determination, attitude determination, attitude sensor analysis, and flight 

dynamics product generation. This effort is sponsored and supported by the FDAB, which provides 

consultation support as needed and periodically reviews the overall program status. This has been a very

successful outreach initiative and gives the student team practical experience and training in spacecraft 

flight dynamics computations, the use of several commercial ground support tools and analysis of flight

data. The operation also serves as a test bed for researching ground system automation techniques. During 

the past year, new team members were successfully trained following some losses due to graduation. Some

members of the team that have graduated have taken jobs in private industry supporting spacecraft 

operations. This is another measure of success for the program. 

[Technical Contact: Tom Stengle] 

7.3 Educational Outreach: NASA Academy 

As part of the GSFC outreach effort to support universities, the FDAB took part in the NASA Academy, a 

summer internship for undergraduate and graduate students who are considered tops in their field. This year 

the FDAB hosted two students, Ms. Corissa Young from Colorado and Mr. Adam Ross from Harvard. 
Their subject was to complete mission design concepts for Unique Non-Keplerian orbits. This cooperative 

work was enabled under a director’s discretionary fund for advanced research topics. The work covered 10

weeks during the summer with final results presented to a GSFC peer review panel. An example of their 

efforts is shown in Figure 7-2, the orbits of a vertical libration orbit and Earth polar sitters that enable 

continuous viewing of the Earth’s polar regions. 

Looking at the Ecliptic 

Z

X

Sun 

Spacecraft 

Lunar 

Earth 

25,000 

Earth 

Geocentric 

Inertial 

Frame

Figure 7-2 Vertical libration orbit and Earth polar sitters

[Technical contact: David Folta] 
7.4 PREST Program 

During FY00, the FDAB supported two students under a grant with the George Washington University

Program of Research and Education in Space Technology (PREST). One of these students is currently in

residence at the GSFC and is working with branch members on research of formation flying control

techniques. The other student completed analysis of new algorithms for attitude determination and rate 

estimation using GPS measurements. 

[Technical Contact: Tom Stengle] 

7.5 Graduate Student Research Program (GSRP) 

The FDAB continued its long standing support of the GSRP program. In FY00, one GSRP sponsorship 

came to a close, while two new GSRP efforts were initiated: 

• “Decentralized Control of Distributed Satellite Networks” to be performed by Mr. Belanger of UCLA 

• “Feasibility of Atmospheric Penetration for Satellite Formation Flying Experiment” to be performed

by Mr. Joseph Schultz of the University of Maryland

[Technical Contact: Tom Stengle] 

7.6 Public Education/Community Outreach 

The following outreach activities were supported in FY00:

Science Fair & Engineering Judging-

• District of Columbia Citywide Science Fair, Howard University, WDC, 3/19/00

 

Rocket Building/Engineering Design Projects- 

• Take Our Daughters to Work Program, Egg Drop Contest, NASA GSFC, Greenbelt, MD, 4/14/00 

 

Career Presentations-

• University of Maryland Department of Aerospace Engineering Sigma Gamm Tau Chapter 

• National Academy of Science, Women in Science and Engineering (WISE) Committee, WDC

10/30/99 

• Joint Education Facilities, 2574 Naylor Road, SE, WDC, 1/8/00

• Tarrant County College, “Careers in Science & Tech. – A-A Contributions to Tech.”, Ft. Worth, TX,

2/7/00

• PG Community College, Science Engineering Education Day, 301 Largo Rd, Largo, MD, 2/1/00 

• QEM/MSE National Conference, “You meet the Scientist”, JW Marriott Hotel, WDC, 2/12/00

• Jeremiah E. Burke High School, 60 Washington St., Dorchester, MA, 3/10/00 

• The Stone Ridge School, School of the Sacred Heart, 9101 Rockville Pike, Bethesda, MD, 3/13/00

• Ferrebee Hope Community School, 3999 8th St., SE, WDC, 3/20/00 

• GW Univ., Women & Power Leadership Program, Mt. Vernon Campus, WDC, 4/20/00 

• DC Metropolitan Organization of Scientists, Bolling AFB, WDC, 9/12/00 

• Trenton & Plainville HS, Rutgers Campus, Piscattaway, NJ, 7/20/00

Career Day Presentation 

• NTA Scientist and Engineer School Visitation Day, Kingsford, ES, Mitchellville, MD 11/4/99

 

Speech (Open, Award, Closing & Graduation Ceremonies, Luncheon) - 

• National School Boards Association, The Education Technology Program, Dallas TX, 11/12/99
• Zonta International Club of Charles County, “Flying into the new millenium", Charles County, MD, 

1/11/00 

• NCA&T, Ronald McNair Memorial Program, Greensboro, NC, 1/28/00 

• Tarrant County College, Luncheon, Ft. Worth, TX, 2/7/00

• National Academies’ 2000 African American History Day Program, WDC, 2/14/00 

• Defense Information Systems Agency, Women's History Month-Kickoff, Arlington, VA, 3/8/00 

• US Department of Veteran’s Affairs, Women's History Month, 810 Vermont Ave., NW, WDC,

3/14/00 

• Grant County All Academic Team Dinner, Grant IN, 5/20/00 

• Richard Montgomery H. S. Graduation-Rockville, MD, Constitution Hall, WDC, 6/8/00

• Tech 2000 Symposium, Breakfast Keynote Speaker, Eden Roc Resort, Miami FL, 7/21/00

• Tuskegee Airmen’s National Convention, Youth Luncheon, San Antonio, TX, 8/10/00 

• Rutgers University, Off.Min.Under.Prog. Freshman Orientation, Piscataway, NJ, 8/20/00 

• Minority Access National Role Models Conference, Washington Marriott, WDC, 9/17/00

Program Visits NASA GSFC/Mentor Student/Fellow-

• MIE, Faculty visit, setup by NASA HQS, 10/21/99 

• Sunbeams Program, St. Frances Xavier MS, Greenbelt, MD, 1/13/00 

• Delta Academy Baltimore, A-A Girls mentoring program, Greenbelt, MD, 2/17/00 

Education/Career Conference or Panel- 

• National Academy of Science WISE Committee, WDC 10/30/99 

• Department of Defense (DoD) Leaders of Educ. Programs w/ SME Dimensions Conference, 

Doubletree Hotel Arlington, VA 11/5/99

• QEM/MSE Natl Conf., “Career Pathways for Ph.D.'s ...”, JW Marriott Hotel, WDC, 2/12/00

• NAFEO’s Annual Black College Student’s High Tech Expo, Hilton Hotel and Towers, WDC, 2/15/00 

• Penn State, Math Options Day, Erie, PA, 5/9/00 

• Women’s Information Network, National Democratic Club, WDC, 6/1/00 

• MIT Mites 25th Anniversary Conference, MIT Sloan Bdg, Cambridge, MA, 7/15/00 

• Tech 2000 Symposium, Women’s History & Issues in Science & Technology, Miami FL, 7/22/00 

• Congressional Black Caucus, “Chic Geek on Cyberstreet”, WDC, 9/15/00 

Online/Video Conference Interactive Session- 

• Women of NASA (WON) Chatline, NASA GSFC, MD, 2/2/99, 2/25/00

• Network Resources and Training Sites (NRTS) Program, South Carolina State Univ., Video 

conference, 6/12/00 

• “Digital Diversity: Power to the People?”, Videoconference WHUT TV 32, Howard University, 

10/27/99 

• Minority University - Space Interdisciplinary (MU-SPIN) Space Mission Involvement Workshop 

• Videoconference, Morgan State University, 12/10/99 (Ref. http://nasa.utep.edu/miwc/) 

External Advisor/Mentor- 

• Howard University, Graduating Senior Architectural Student: Rodney Lapson, Thesis: Moon Base. 

Television/Radio/Magazine/Website Interviews- 

• NBC Nightly News, "Women to Watch", Andrea Mitchell, 1/13/00

• iVillage.com, "Women Who Rule", 2/00 

• NSBE Engineer, Malik Russell, 2/3/00 

• Spacekids.com, Denise Jewell, 2/3/00

• ScienceMaster.com, “Meet Dr. Aprille Ericsson-Jackson”, Gene Mascoli, 3/00

• The George Lucas Foundation, Edutopia: “Bridging the Digital Divide”, Spring 2000, Sara 

Armstrong Essence Magazine, “Ya Done Good Girl”, 5/00

• Yahoo Internet Life, “How America Uses the Net”, Jeremy Kaplan, 212-503-5167, 9/00
• Howard University Magazine, Martha Frase-Blunt, 703-683-5658, 9/00

• Woman Engineer, “To Give is to Receive”, Anne Baye Eriksen, 10/00 

Committees- 

• NASA GSFC: Black History Club, NTA GSFC Chapter-President, Diversity and Recruitment 

Team; National Technical Association: National Conference Planning Committee, National School

Visitation Committee Chair, Publications and Editorial Committee; Building STEPS Board Member. 

Proposal/Application Reviewer-

• Graduate Student Researchers Program, NASA GSFC, Code 160, Greenbelt, MD 20771, 3/00

• National Science Foundation (NSF) Undergraduate Engineering Education, Arlington, VA, 3/00

[Technical contact: Aprille Ericsson- Jackson] 

 
Appendix A – Awards

List of awards earned in FY2000: 

Earth Observing System-AM Project Team 2000 

GEODE was a runner-up in NASA's Software of the Year competition. 

Group Achievement Award, Customer Service Excellence Award Microwave Anisotropy Probe (MAP)

Flight Software Team, February 9, 2000 

Group Achievement Award, Quality and Process Improvement Annual Award Microwave Anisotropy

Probe (MAP) Simulation Team, October 15, 1999 

Group Achievement Award, Quick Scatterometer (QuikSCAT) Observatory and Mission Operations 

Team, August 14, 2000

GSFC Annual Moe I. Schneebaum Memorial Award for Engineering was given to David Folta

GSFC Award of Merit was given to Robert L. DeFazio for support to numerous Earth and space science 

flight projects 

GSFC Certificate of Appreciation to the CGRO Re-entry Team 

GSFC Outstanding Mentor Award was given to David Mangus 

GSFC Performance Awards to the FDAB CGRO Re-entry Team 

GSFC Quarterly Customer Service Excellence Award to the MAP Maneuver Team 

 

GSFC Quarterly Outstanding Teamwork Award to the EOS AM Project Team 

GSFC Quarterly Outstanding Teamwork Award to the Terra Flight Dynamics Team 

GSFC Special Act Awards to the FDAB CGRO Re-entry Team 

NASA Academy Certificate of Recognition was given to David Folta

NASA Group Achievement Award / Center of Excellence for Lunar Prospector Support 

NASA Group Achievement Award /Mars Climate Orbiter Mishap Investigation Board, Achievement 

Award via MSFC Director 

Outstanding Teamwork Group Award to the IMDC team

Terra Flight Dynamics Team 2000 

 

Appendix B - University Grants 

The following university grants being administered by FDAB engineers were in place in FY00: 

1. GRANT NAG5-9961 with the University of Maryland Department of Aerospace Engineering titled 

“Precise Virtual Rigid Body Control of a Satellite Constellation.” This grant is developing a possible 

control strategy for formation flying. 

 [Technical Contact: Thomas Stengle] 

2. GRANT NAG5-9890 with the University of Maryland Department of Aerospace Engineering titled 

“Rarefied Flow Aerodynamics for Stability and Control of Formation-Flying Satellites.” This grant is 

researching problems and control strategies for spacecraft flying in formation with low perigee passes.

This research may benefit the development of control approaches for the Geospace Electrodynamics 

Connections (GEC) mission. 

 [Technical Contact: Marco Concha] 

3. GRANT NAG5-8697 with the University of Colorado at Boulder titled “Algorithms for Autonomous

Orbit Determination and Formation Flying.” The focus of this grant is on algorithms for use of GPS 

for formation flying missions in highly elliptical orbits, including signal acquisition and tracking and 

relative navigation. 

[Technical Contact: Steve Hughes] 

4. GRANTS NAG5-8694 and NAG5-8879 with the University of California at Los Angeles titled

“Decentralized Estimation and Control of Distributed Spacecraft,” and “Precise Relative State 

Estimation and Control of Distributed Satellite Networks.” These grants are developing and applying

new decentralized control architectures for satellite formations. 

 [Technical Contract: Russell Carpenter] 

5. GRANT NAG5-9829 with the University of Texas at Austin titled “Spacecraft Rendezvous Navigation

with Integrated INS-GPS.” This grant is focusing on GPS/INS software architecture development for 

relative navigation and attitude determination. 

[Technical Contract: Russell Carpenter] 

6. GRANT NAG5-9612 with Cornell University Sibly School of Mechanical and Aerospace Engineering 

titled “New Algorithms for Magnetometer Orbit and Attitude Estimation.” This grant is studying the 

feasibility of a moderate precision navigation (<10 km orbit, <0.5 degrees attitude) using

Magnetometer data. 

[Technical Contract: Richard Harman] 

7. GRANT NAG5-9748 with Princeton University Department of Mechanical and Aerospace 

Engineering titled “ Satellite Attitude Estimation with the Two Step Optimal Estimator.” This grant is 

studying the ability of the two-step algorithm to out perform the standard Extended Kalman Filter 

currently used for spacecraft and ground attitude estimation. 

[Technical Contract: Richard Harman] 

8. GRANT NAG5-8770 with Technion-Israel Institute of Technology Department of Aerospace 

Engineering titled “Improvement of the REQUEST Attitude Determination Algorithm for Aiding
MAGNAV.” This grant is studying the possible advantages of using the Recursive QUEST algorithm

in place of the pseudo-linear and extended Kalman Filters in the real-time Magnetometer Algorithms. 

[Technical Contract: Richard Harman/572]
Appendix C – Conferences and Papers

List of conferences and professional papers in FY2000:

Lauri K Newman, Paul J. Noonan, and Cheryl. J. Gramling, "Ground System Support Of An Onboard

Navigation System: Implementation And Operations Experiences", AAS 00-121, AAS/AIAA Space Flight

Mechanics Meeting, Clearwater,FL, January 23-26, 2000. 

G. Lightsey, C. Campbell, R. Carpenter, J. Simpson, G. Davis, "Design and Performance of Space 

Algorithms for the GPS Receiver used on International Space Station and Crew Return Vehicle," 

Proceedings of the International Workshop on Aerospace Applications of the Global Positioning System, 

Jan 31-Feb 2, 2000, Breckenridge, CO. 

F. Bauer, J. Bristow, R. Carpenter, J. Garrison, K. Hartman, A. Long, T. Lee, D. Kelbel, V. Lu, J. How, F. 

Busse, P. Axelrad, M. Moreau, "Enabling Spacecraft Formation Flying in Any Earth Orbit Through 

Spaceborne GPS and Enhanced Autonomy Techniques," Proceedings of the International Workshop on

Aerospace Applications of the Global Positioning System, Jan 31-Feb 2, 2000, Breckenridge, CO. 

R. Carpenter, "A Preliminary Investigation of Decentralized Control for Satellite Formations," Proceedings 

of the 2000 IEEE Aerospace Conference, Mar 18-25, 2000. 

A. Long, D. Kelbel, T. Lee, R. Carpenter, C. Gramling, "Autonomous Relative Navigation for FormationFlying Satellites Using GPS," CNES 15th International Symposium on Space Flight Dynamics, June 26-30, 

2000, Biarritz, France. 

A. Long, D. Kelbel, T. Lee, R. Carpenter, J. Garrison, "Autonomous Navigation Improvements for High

Earth Orbiters Using GPS," CNES 15th International Symposium on Space Flight Dynamics, June 26-30, 

2000, Biarritz, France. 

R. Carpenter, D. Folta, C. Wagner, "Formation Flying with Decentralized Control in Libration Point 

Orbits," CNES 15th International Symposium on Space Flight Dynamics, June 26-30, 2000, Biarritz, 

France. 

Cheryl Gramling, "Preliminary Operational Results of the TDRSS Onboard Navigation System (TONS) for 

the Terra Mission", June 2000, ISSD conference, Biarritz, France. 

Lauri K. Newman, Richard J. McIntosh, and Paul J. Noonan, "Terra Ascent Planning to Meet Landsat-7

Phasing Requirements,"AIAA 2000 -4342, AIAA Astrodynamics Specialist Conference, Denver, CO, 

August 14-17, 2000. 

Julie Deutschmann, Itzhack Bar-Itzhack, and Rick Harman, "A LEO Satellite Navigation Algorithm Based 

on GPS and Magnetometer Data", International GPS Workshop & International Flight Dynamics 

Conference, Biarritz, France. 

Seminar/Technical Presentations: 

Dr. Aprille Ericsson- Jackson, technical presentation on MAP ACS Summary, May 2000, Taylor

University, Physics Department, IN. 

Dr. Aprille Ericsson- Jackson, NCA&T, “Experiences & Opportunities for a Ph.D. Student”, Greensboro, 

NC, 1/28/00 

 

Dr. Aprille Ericsson- Jackson, Texas Southern University, “How to Make an Outstanding Technical 

Presentation” Dallas, TX, 2/5/00

 
Dr. Aprille Ericsson- Jackson, Tarrant County College, “Obtaining One’s Goals in a Technical 

Environment”, Ft. Worth, TX, 2/7/00

 
Appendix D- Acronyms and Abbreviations 

This appendix gives the definitions of acronyms used in this document. 

AAS American Astronautical Society 

ACS Attitude Control System

ACT Attitude Control Thrusters 

AETD Applied Engineering and Technology Directorate 

AI Artificial Intelligence 

ALI Advanced Land Imager 

AO Announcement of Opportunity 

APL Applied Physics Laboratory 

AST Autonomous Star Tracker

ATMS Advanced Technology Microwave Sounder 

CCSDS Consultative Committee for Space Data Systems 

CETDP Cross Enterprise Technology Development Program

CGRO Compton Gamma Ray Observatory 

COTS Commercial Off-the-Shelf 

CPT Comprehensive Performance Test 

CSOC Consolidated Space Operations Contract 

CVS Concurrent Version System 

DACC Distributed Active Archive Center

DoD Department of Defense 

DSN Deep Space Network 

DSS Digital Sun Sensor 

DST Dynamical Systems Theory 

EFF Enhanced Formation Flying 

EMOS EOS Mission Operations System

EO Earth Observing 

EOS Earth Observing System

ESA European Space Agency 

ESSP Earth System Science Pathfinder 

EUVE Extreme Ultraviolet Explorer 

FAA Federal Aviation Administration 

FDAB Flight Dynamics Analysis Branch 

FDS Flight Dynamics System

FDSS Flight Dynamics Support System

FDF Flight Dynamics Facility 

Flex Fluorescence Experiment 

FOT Flight Operations Team

FSW Flight Software 

FY Fiscal Year 

GEO Geosynchronous Earth Orbit 

GEODE GPS Enhanced Orbit Determination Experiment

GEONS GPS-Enhanced Orbit Navigation System

GINA Generalized Information Network Analysis

GNCC Guidance, Navigation, and Control Center 

GOES Geostationary Operational Environmental Satellite 

GPM Global Precipitation Mission

GPS Global Positioning Satellite 

GRO Gamma Ray Observatory 

GSE Ground Support Equipment 

GSFC Goddard Space Flight Center 

GSRD Ground System Requirements Document 

GSRP Graduate Student Research Program

GTDS Goddard Trajectory Determination System
GUS Gyroscopic Upper Stage 

HD Henry Draper

HDS Hybrid Dynamic Simulator 

HEO High Earth Orbit/ Highly Elliptical Orbit 

HGA High Gain Antenna 

HTML HyperText Markup Language

ISEE-3 International Sun-Earth Explorer 3 

I&T Integration and Test 

ICD Interface Control Document 

IHS Inner Heliospheric Sentinels 

IM Ionosphere Mapper

IMDC Integrated Mission Design Center 

IMU Inertial Measurement Unit 

ISU International Space University 

ITAR International Traffic In Arms Regulation 

ITSO International Telecommunications Satellite Organization

JPL Jet Propulsion Laboratory 

LEO Low Earth Orbit 

LOR Launch and Orbit Raising 

LPT Low Power Transceiver 

LQG Linear Quadratic Gaussian 

LRR Lightweight Rainfall Radiometer

MAP Microwave Anisotropy Probe 

MARSAT Mars Areo-stationary Relay Satellite 

MC Master Catalog 

MCC Mid Course Correction 

MCO Mars Climate Observer

MIT Massachusetts Institute of Technology

MLS Microwave Limb Sounder 

MMS Magnetic Multi-scale Mission 

MOC Mission Operations Center 

MOCC Mission Operations Command and Control

MODIS Moderate Resolution Imaging Spectroradiometer 

MOPSS Mission Operations Planning and Scheduling System

MOST Mission Operations Support Team

MOWG Mission Operations Working Group 

MSRD Mission Specific Requirements Document

MU-SPIN Minority University - Space Interdisciplinary 

NASA National Aeronautical and Space Administration 

NGST Next Generation Space Telescope 

NMM Normal Maneuver Mode 

NOAA National Oceanic and Atmospherics Administration 

NPB Navigation Processor Board 

NPM Normal Pointing Mode 

NRTS Network Resources and Training Sites 

NSF National Science Foundation 

NT New Technology 

OAT Orbit Adjust Thrusters 

ONS Onboard Navigation Systems 

OSSM Ocean Surface Salinity Mission 

PC Personal Computer 

PI Principal Investigator 

PICASSO-CENA Pathfinder Instruments for Cloud and Aerosol Spaceborne Observations - 

Climatologie Etendue des Nuages et des Aerosols 

PLT Post Launch Testing 

PREST Program of Research and Education in Space Technology 
QuikSCAT Quick Scatterometer 

R&D Research and Development 

RBM Radiation Belt Mapper 

RMS Root-Mean-Square 

RPO Radiation Protection Office 

RSDO Rapid Spacecraft Development Office 

RTOD Real-time Orbit Determination 

RWA Reaction Wheel Assembly 

RXTE Rossi X-Ray Timing Explorer 

SA Selective Availability 

SAMPEX Solar Anomalous and Magnetospheric Particle Explorer 

SMEX Small Explorer 

SOHO Solar and Heliospheric Observatory 

SOMO Space Operations Management Office 

SPECS Evolution of Cosmic Structure 

SPS Standard Positioning Service 

ST Space Technology 

TDRSS Tracking Data Relay Satellite System 

TMM Thruster Maneuver Mode 

TONS TDRSS Onboard Navigation System 

TRACE Transition Region and Coronal Explorer 

TRMM Tropical Rainfall Measuring Mission 

URL Uniform Resource Locator 

USN Universal Space Network 

VCM Velocity Control Mode 

VIIRS Visible Infrared Imaging Radiometer Suite 

WAAS Wide Area Augmentation System 

WIRE Wide-Field Infrared Explorer 

WISE Women in Science and Engineering 

WON Women of NASA 

WRS World Reference System 

WWW World Wide Web