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1
NASA Update on GPS Use
Dr. A.J. OriaOverlook Systems Technologies, Inc. NASA H.Q. Ctr
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Outline
• International GPS Service (IGS) & Global Differential GPS (GDGPS)
• TDRSS Augmentation Service for Satellites (TASS)
• Distress Alerting Satellite System (DASS)
3
International GPS Service - Overview
NASA Key Contribution Areas
(60 out of 286 NASA’s)
JPL
JPL
JPL JPL
JPL
JPLGoddard
What is IGS?
• The International GPS Service (IGS) was formally recognized in 1993 by the International Association of Geodesy (IAG), and began routine operations on January 1, 1994
• Over 10 years it has expanded to a coordinated network of over 300 GPS monitoring stations from 200 contributing organizations in 75 countries
• Mission: “to provide a service to support, through GPS data products, geodetic and geophysical research activities” – IGS Terms of Reference
• Collects, archives, processes, and distributes GPS observation data with typical 1 hour latency (not in real-time).
IGS Network Products:
• High accuracy GPS orbits• Earth rotation parameters • IGS tracking station coordinates and velocities • GPS satellite and IGS tracking station clock
information • Zenith tropospheric path delay estimates • Global ionospheric maps• Available at:
http://igscb.jpl.nasa.gov/components/prods.html
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NASA’s Contribution to IGS with GDGPS
• Global Differential GPS (GDGPS) – Fully operational since 2000– 60 dual-frequency GPS geodetic reference stations
• 10 cm horizontal & 20 cm vertical real-time positioning accuracy with dual frequency GPS receivers
• 10 cm level real–time orbit determination for LEO satellites with dual frequency GPS receivers may be possible
• Not certified for safety-of-life applications• For more information: http://gipsy.jpl.nasa.gov/igdg
• NASA GPS Stationso NASA Cooperative Stations• Other Agency Stations
Tracking Network of the International GPS Service
Highlighting NASA’s Contributions
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GDGPS as an Enabler -Probing the Earth with GPS
IONOSPHEREIONOSPHEREOCEANSOCEANS SOLID EARTHSOLID EARTH
ATMOSPHEREATMOSPHERE
Significantwave heightSignificant
wave height
Ocean geoid andglobal circulationOcean geoid andglobal circulation
Surface windsand sea state
Surface windsand sea state
Short-term eddyscale circulationShort-term eddyscale circulation
OCEANSOCEANS
High resolution 3Dionospheric imagingHigh resolution 3D
ionospheric imaging
Ionospheric struc-ture & dynamics
Ionospheric struc-ture & dynamics
Iono/thermo/atmo-spheric interactionsIono/thermo/atmo-
spheric interactions
Onset, evolution& prediction ofSpace storms
Onset, evolution& prediction ofSpace storms
TIDs and globalenergy transportTIDs and globalenergy transport
Precise ion cal forOD, SAR, altimetryPrecise ion cal forOD, SAR, altimetry
IONOSPHEREIONOSPHERE
Climate change &weather modelingClimate change &weather modeling
Global profiles of atmosdensity, pressure, temp,and geopotential height
Global profiles of atmosdensity, pressure, temp,and geopotential height
Structure, evolutionof the tropopause
Structure, evolutionof the tropopause
Atmospheric winds,waves & turbulenceAtmospheric winds,waves & turbulence
Tropospheric watervapor distribution
Tropospheric watervapor distribution
Structure & evolutionof surface/atmosphere
boundary layer
Structure & evolutionof surface/atmosphere
boundary layer
ATMOSPHEREATMOSPHERE
Earth rotationPolar motion
Earth rotationPolar motion
Deformation of thecrust & lithosphereDeformation of thecrust & lithosphere
Location & motionof the geocenter
Location & motionof the geocenter
Gross massdistributionGross massdistribution
Structure, evolution of the deep interior
Structure, evolution of the deep interior
Shape of the earthShape of the earth
SOLID EARTHSOLID EARTH
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GPS Technologies & Applications -Example – Geodesy & Oceanography
GPS 1
GPS 2
LEO
GPS 4GPS 3
Ocean surface • Height • Roughness (winds)
Reference ellipsoid
h2h1
Troposphere: vertically integrated precipitable water vapor
Bi-Static Ocean Reflectrometry• Operational ocean altimeter calibrations for Navy
and NASA
Gravity Field Measurements• GRACE dual-satellite mission • JPL GPS Receiver with integrated camera
and K-band spacecraft to spacecraft tracking
• 1-micron accuracy measurement• Improve knowledge of the Earth’s gravity
field by several orders of magnitude
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GDGPS - GPS Performance Monitoring
The GDGPS System tracks each GPS satellite by at least 6 sites, and by 15 sites on average, enabling robust, real-time GPS performance monitoring with 4 sec to alarm
The GDGPS GPS Integrity Monitor
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GDGPS - Integrity Monitoring
GDGPS is ideally suited for GPS integrity/performance monitoring:• State space approach (as in the OCS) enables separation of orbit and clock errors• Large global network allows estimation of clocks independent of models (unlike
OCS), enabling prediction of integrity failures• Large global network enables implementation of majority voting schemes• High operational reliability• High performance monitoring: high accuracy, multiple metrics, absolute metrics• Independent of any other system employed in support of GPS operations
Leverage the NASA tens of million dollar investment in the GDGPS infrastructure
A prototype GPS integrity monitor was developed by JPL funded by IGEB and NASA • Operational since May 2003• 100% availability to-date, with no known failures• No false alarms• All GPS anomalies monitored• Extremely positive feedback from 2SOPS
3000
4000
5000
6000
7000
8000
9000
15
20
25
30
35
40
5 6 7 8 9 10 11 12 13
# of Hits
# of Distinct IP
s
Month, 2003
Non-JPL/Aerospace Usage Statistics
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GDGPS & TASS (TDRSS Augmentation Service for Satellites)
Uplink
Broadcast
TDRSS
Space users
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
GDGPS Operations Center
Frame
Internet
NASA’s global real time network
TASS (under development)
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Tracking and Data Relay Satellite System (TDRSS)
• The Tracking and Data Relay Satellite Project (TDRS) system consists of in-orbit telecommunications satellites stationed at geosynchronous altitude and associated ground stations located at White Sands, New Mexico, and Guam.
• Functions:– Space Network tracking.– Provide data, voice and video services to NASA scientific satellites, the Shuttle,
International Space Station, and to other NASA missions. – Developing capability to provide user navigational data needed to locate the orbit and
position of NASA user satellites.
F-5174°WTDW
F-7171°WStored
F-1049°W
F-6047°WTDS
F-4041°WTDE
F-3275°WTDZ
WHITE SANDS COMPLEX
GODDARD SPACE FLIGHT
CENTER
GUAM REMOTE GROUND TERMINAL
F-8171.5°W
F-9150°WTest
F-10150.7°WTest
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TDRSS Augmentation Service for Satellites (TASS)
• TASS provides NASAs GDGPS corrections via TDRSS satellites
• Integrating NASA’s Ground and Space Infrastructures
• Provides user navigational data needed to locate the orbit and position of NASA user satellites
47o W171o W
85o E
~18-20o
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Distress Alerting Satellite System (DASS)
Cospas-Sarsat System• International cooperative effort with Search &
Rescue (SAR) payloads on numerous satellites and a worldwide network of 45 ground terminals
• Relay distress signals from maritime, aviation, and land-based beacons
• Over 17,000 lives saved to date• Known deficiencies including detection delay and
location accuracy – based on 1970’s technology
DASS• 1997 Canadian Follow-On SAR System (FOSS)
study showed MEO constellation would provide an optimal follow-on space platform for greatly improved performance
• SAR Payloads to fly on the GPS constellation• Under Development by the NASA SAR Mission
Office in partnership with the DoD & Sandia National Labs (SNL) in support of the National SAR Committee (NSARC)
• NASA, USAF SMC and ACC, DoE, NOAA, and USCG participate in MOA to conduct DASS POC
DASS Proof-of-Concept (POC)
406 MHz Uplink
S-Band downlink for POC
1544 MHz for OPS
SAR POC Ground Station(s)
SAR Aircraft
Beacons
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Distress Alerting Satellite System (DASS)
DASS Provides• 406 MHz ‘bent pipe’ repeaters on future GPS
satellites• Full compatibility with existing and future 406 MHz
beacons• Global near-instantaneous detection and location
• Beacons without embedded GPS – greater than Cospas-Sarsat accuracy with 3 bursts or less
• Self-locating beacons – GPS accuracy after single beacon burst
• Support USAF/military SAR responsibilities• Alert data downlink freely available internationally• Low technical risk and low cost (uses modified
existing GPS hardware)
Optionally Could Provide• Short digital message return confirmation
message • Aids in false alarm mitigation • Direct communications with survivors • Support rescue force coordination• Reduced interference susceptibility via
confirmation
Development Status
On-Orbit Testing• Two DASS satellites in-orbit, 3rd SVN60 / IIR-11
scheduled for early 2004• Testing performed (GSFC and SNL) using GPS
IIR-07• Preliminary results support feasibility analysis
DASS POC Ground Equipment• Antenna system installation completed 3rd quarter
2004• Ground station equipment acquisition process by
RFP in early 2004.• The DASS Local User Terminal being developed
at GSFC
Ground Station Site Selection• Antennas on GSFC Building 28 roof, ground
station equipment in Building 25• GSFC physical space construction detailed
planning has begin
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Contributors to this Presentation:
• Dr. Lawrence Young – Jet Propulsion Lab– 818-354-5018 [email protected]
• Allen Farrington – Earth Science Flight GPS Receiver Office, Jet Propulsion Laboratory – 818-393-5260 [email protected]
• Dr. Yoaz Bar-Sever – Jet Propulsion Lab– 818-354-2665 [email protected]
• Dr. Frank Bauer – Goddard Space Flight Center – 301-286-3102 [email protected]
• Dave Affens - Goddard Space Flight Center – 301-286-9839 [email protected]
• Dr. Michael Moreau – Goddard Space Flight Center– 301-286-8382 [email protected]
• Roger J. Flaherty – Goddard Space Flight Center– 301-286-7028 [email protected]
• Scott Murray – Johnson Space Center– 281-483-8242 [email protected]
• Dr. Scott Pace – NASA Headquarters– 202-358-1811 [email protected]
• Dr. A.J. Oria – Overlook Systems Technologies, Inc. / NASA HQ Ctr– 703-8931411 x 125 [email protected]
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