Outline

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NASA Update on GPS Use Dr. A.J. Oria Overlook
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)

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International GPS Service - Overview

• 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

JPL
JPL
JPL
JPL
Goddard
JPL
JPL
(60 out of 286 NASAs)
NASA Key Contribution Areas
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NASAs 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 realtime 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/ig
  dg

Tracking Network of the International GPS
Service Highlighting NASAs Contributions

• NASA GPS Stations
• NASA Cooperative Stations
• Other Agency Stations

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GDGPS as an Enabler - Probing the Earth with GPS
SOLID EARTH
OCEANS
IONOSPHERE
ATMOSPHERE
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GPS Technologies Applications -Example
Geodesy Oceanography

• 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 Earths gravity field by
  several orders of magnitude

• Bi-Static Ocean Reflectrometry
• Operational ocean altimeter calibrations for Navy
  and NASA

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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

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GDGPS TASS (TDRSS Augmentation Service for
Satellites)
TASS (under development)
TDRSS
Uplink
Broadcast
Space users
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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.

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TDRSS Augmentation Service for Satellites (TASS)

• TASS provides NASAs GDGPS corrections via TDRSS
  satellites
• Integrating NASAs Ground and Space
  Infrastructures
• Provides user navigational data needed to locate
  the orbit and position of NASA user satellites

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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 1970s 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)

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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)

• 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

• 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

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Contributors to this Presentation

• Dr. Lawrence Young Jet Propulsion Lab
• 818-354-5018 Lawrence.E.Young_at_jpl.nasa.gov
• Allen Farrington Earth Science Flight GPS
  Receiver Office, Jet Propulsion Laboratory
• 818-393-5260 Allen.H.Farrington_at_jpl.nasa.gov
• Dr. Yoaz Bar-Sever Jet Propulsion Lab
• 818-354-2665 Yoaz.E.Bar-Sever_at_jpl.nasa.gov
• Dr. Frank Bauer Goddard Space Flight Center
• 301-286-3102 Frank.Bauer_at_nasa.gov
• Dave Affens - Goddard Space Flight Center
• 301-286-9839 David.W.Affens_at_nasa.gov
• Dr. Michael Moreau Goddard Space Flight Center
• 301-286-8382 Mike.Moreau_at_nasa.gov
• Roger J. Flaherty Goddard Space Flight Center
• 301-286-7028 Roger.J.Flaherty_at_nasa.gov
• Scott Murray Johnson Space Center
• 281-483-8242 Scott.V.Murray_at_nasa.gov
• Dr. Scott Pace NASA Headquarters
• 202-358-1811 Scott.Pace_at_nasa.gov

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