2000 NASA Software of the YearAward Nomination
GPS Enhanced Orbit Determination(GEODE) Software
Submitted by GSFC, Code 570
Team Members:
Mark Beckman Dr. J. Russell Carpenter
James Garrison Roger Hart
Kathy Hartman Dr. Taesul Lee
Dr. Anne Long Victor Lu
Dr. Dipak Oza
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Our Challenge: Move Satellite Navigation from Earth to Space
◆ Satellite navigation is now performed onthe ground
◆ Our challenge is to build a navigationsystem for civilian satellites using GPSthat
– Computes satellite position andvelocity onboard, instantaneously,with high accuracy
– Operates reliably without humanintervention
– Fits within very limited computingresources
GPSSatellite
UserSatellite
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State-of-the-art navigation algorithms and operating-environment-independent, object-oriented software implementation
➘ Unprecedented accuracy, reliability, and autonomy
➘ In use by NASA and commercial projects
➘ Open-architecture, licensed GSFC product
Enables advancedautonomous satelliteoperations
Our Solution: GEODE
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GPS Receiver Solution Using Standard Method
◆ Designed primarily for near-Earth use
◆ Requires continuous visibility of at least four GPS satellites tocompute position (receiver solution)
◆ Accurate use of GPS signals in civil domain is eight times harderthan in the military domain
Unique Challenges of Using GPSfor Satellite Navigation
◆ High accuracy velocity required foraccurate position prediction
◆ GPS receiver outages due to hostilespace environment (solar particleradiation or high velocities)
◆ GPS visibility limited by antennaplacement and changing satelliteorientation
◆ Many potential science missions areabove the GPS constellation
◆ Limited computer processing powerin space
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Innovation
Science and Technology Significance and Impact
Extent of Current and Potential Use
Usability of Software
Quality Factors
Key Accomplishments vsEvaluation Criteria
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Innovative Algorithms Benefits
Accurate model forsatellite motion (gravity,Earth’s atmosphere, etc.)
Can coast through receiveroutages for more than 24 hours
Kalman filter forcomputation of correctedposition and velocity
Computes real-time corrections
Computes high-accuracy velocitysolutions
Requires measurements from only1 visible GPS satellite
Combination of accuratemodel and Kalman filter
Eliminates impact of GPS signalcorruption
Innovation: State-of-the-Art Algorithms for theSpace Environment
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Innovation: A Better Way to Fly
4 or more GPSSatellites Acquiredby Receiver
GEODE’sGEODE’s Predicted Solution Predicted Solution
TrueTrueSatellite PositionSatellite Position
Receiver’s Solution
Receiver’sSolution, if Predicted
1-3 GPSSatellitesAcquired byReceiver
No GPS SatellitesAcquired by Receiver
GEODE’sGEODE’s Filtered Solution Filtered Solution
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Innovation: Demonstrated PerformanceImprovements
GEODE’s Solution
CommercialReceiver’sSolution
5 10 15 20 25
Time (Hours)
0
50
100
150
250
Po
siti
on
Err
or
(met
ers)
0
TOPEX Satellite
200
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Significance: Unprecedented Accuracy and Reliability
GEODE is the only licensed, open-architecture productavailable that provides this level of performance!
GEODE Solution
Receiver Solution
10 meters
150 meters
GEODE Solution
Receiver Solution
1 centimeter/sec
50 centimeters/sec
VelocityError
PositionError
◆ Unprecedented Accuracy– Drives down navigation
errors by a factor of 15in position, a factor of 50in velocity versus receiversolution
◆ Unprecedented Reliability– Maintains performance using measurements from only 1 GPS
satellite– Predicts position for 24 hours without GPS measurements
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Significance: Supports Advanced Earth andSpace Science Mission Concepts
◆ Critical technology for meeting NASA’s strategic needs for increasedsatellite autonomy
◆ Essential technology for collaborative science missions
◆ Opens up GPS navigation to satellites with severely limited GPSvisibility, e.g. high-Earth and geosynchronous missions
◆ Enabling technology for many proposed formation-flying/constellation missions, e.g. Orion/Emerald
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◆ High accuracy navigation products
– Increase accuracy of satellite orientation control
– Provide more precise scientific measurements
– Enable autonomous maneuver planning and control
◆ High reliability reduces risk
◆ Streamlined operationsprovide satellite positioninstantaneously inscience data stream
◆ Autonomous operationdrives down groundoperations costs
Impact: Better, Faster, Cheaper Satellite Operations
BEFOREGround-Based Navigation Scenario
AFTERGEODE Navigation Scenario
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5
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Satellite Operations Center
2-30 Day Delay Instantaneous
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Impact: Other Science and Technology Applications
◆ Enroute aircraft navigation to eliminate or augmentFAA’s GPS/WAAS
◆ Improved navigation accuracy using GPS receiversfor Search and Rescue
◆ Other commercial GPS-related applications
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Extent of Use
◆ Autonomous navigation capabilityfor the New Millennium EO-1/Landsat 7 formation-flyingexperiment
◆ Critical element in GSFC’sdevelopment of low-cost GPSreceivers for high-Earth andformation flying missions
◆ License agreements in place/undernegotiation:– OSC– ITT– United Space Alliance– MIT Lincoln Laboratory– LaRC– Ball Aerospace– UCLA– University of Colorado– Aerospace Corp.
Current Uses Potential Usesu Advanced Earth Science
formation-flying missions suchas MMS and Auroral lites
◆ Provided to LaRc for potentialuse by Picasso/CENA
◆ OSC may integrate GEODE intoa space-qualified version oftheir Astech GPS receiver
◆ Development of advancedautonomous satellite systemsby universities and industry
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Usability: Highly Reusable System
◆ Portable: ANSI standard C, environment-independentimplementation
◆ Modular: Object-based architecture, with encapsulated interfaces
◆ Reuse of GEODE by GSFC for EO-1 and SPARTAN and OSC forORBVIEW has saved more than $1million per project
ReceiverInterface
GPS Measurement
User Orbit
OrbitPropagator
GPS State SatelliteAcceleration
Driver
CommandInterface
ProductInterface
Encapsulated interfaces maximize reuse
Reusewithout change
KEY
CustomInterfaces
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Quality Factors
u Object-oriented architecture selected to build in flexibility tosupport a wide range of mission types
◆ ANSI C language selected to reduce code size and for ease ofportability
◆ Designed to be operating-environment independent
◆ Successfully executed in the following environments:
– PC/Windows
– Sun/HP/ Unix
– Dec Alpha/Linux
◆ TRL 8, flight-qualified against operational standards
◆ Recently adapted for high-Earth missions and formation-flyingapplications with relative ease
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Quality Factors: Engineered to Satisfy Cost andResource Constraints
◆ Reused GSFC-developed TONScomponents to save more than$1,400,000 in initial development
◆ Engineered to fit within the constraintsof an onboard processor withoutcompromising accuracy
ComparableNew
Development
$1,800,000
Development of GEODE
InitialDevelopment
Cost
$400,000
10,000
More Than 1,000,000
Lines of Code
ComparableGround System
GEODEwith
Optimized Algorithms
ComparableGround System
20,000 Kbytes
Memory
60 Kbytes
GEODEwith
Optimized Algorithms
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Bottom Line◆ Significance and Impact
GEODE is more accurate and more reliable than anycommercial GPS navigation system. GEODE is enablingtechnology for NASA’s future formation-flying missions.
◆ Extent of UseLicensed GSFC product. Currently active in NASA andcommercial sectors.
◆ UsabilityUsed successfully on several projects to support wide-range of missions.
◆ Quality FactorsMeets or exceeds all original performance objectives.
◆ InnovationGEODE is the only licensed, open-architecture productsuitable for satellites with limited, intermittent GPSvisibility.
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Autonomoussatellitenavigationusing GPS isstill adevelopingtechnology
Our team is apioneer andleader in thistechnology