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