NASA Update on GPS Use Dr. A.J. Oria Overlook Systems Technologies, Inc. NASA H.Q. Ctr

1. NASA Update on GPS Use Dr. A.J. Oria Overlook Systems Technologies, Inc. NASA H.Q. Ctr

2. 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 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 NASA’s) NASA Key Contribution Areas

4. 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 Tracking Network of the International GPS Service Highlighting NASA’s Contributions • NASA GPS Stations • NASA Cooperative Stations • Other Agency Stations

5. SOLID EARTH OCEANS IONOSPHERE ATMOSPHERE Earth rotation Polar motion High resolution 3D ionospheric imaging Climate change & weather modeling Deformation of the crust & lithosphere Significant wave height Global profiles of atmos density, pressure, temp, and geopotential height Ionospheric struc- ture & dynamics Location & motion of the geocenter Ocean geoid and global circulation Iono/thermo/atmo- spheric interactions Structure, evolution of the tropopause Gross mass distribution Short-term eddy scale circulation Onset, evolution & prediction of Space storms Atmospheric winds, waves & turbulence Structure, evolution of the deep interior Surface winds and sea state Tropospheric water vapor distribution TIDs and global energy transport Structure & evolution of surface/atmosphere boundary layer Precise ion cal for OD, SAR, altimetry Shape of the earth GDGPS as an Enabler - Probing the Earth with GPS SOLID EARTH OCEANS IONOSPHERE ATMOSPHERE

6. 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 Earth’s gravity field by several orders of magnitude • Bi-Static Ocean Reflectrometry • Operational ocean altimeter calibrations for Navy and NASA

7. 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

8. 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

9. GDGPS Operations Center Frame Internet NASA’s global real time network GDGPS & TASS (TDRSS Augmentation Service for Satellites) TASS (under development) TDRSS Uplink Broadcast Space users

10. GODDARD SPACE FLIGHT CENTER WHITE SANDS COMPLEX GUAM REMOTE GROUND TERMINAL F-7 171°W Stored F-8 171.5°W F-5 174°W TDW F-10 150.7°W Test F-9 150°W Test F-1 049°W F-6 047°W TDS F-4 041°W TDE F-3 275°W TDZ 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.

11. 47o W 171o W ~18-20o 85o E 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

12. S-Band downlink for POC 1544 MHz for OPS 406 MHz Uplink SAR Aircraft SAR POC Ground Station(s) Beacons 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)

13. 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

14. Contributors to this Presentation: • Dr. Lawrence Young – Jet Propulsion Lab • 818-354-5018 Lawrence.E.Young@jpl.nasa.gov • Allen Farrington – Earth Science Flight GPS Receiver Office, Jet Propulsion Laboratory • 818-393-5260 Allen.H.Farrington@jpl.nasa.gov • Dr. Yoaz Bar-Sever – Jet Propulsion Lab • 818-354-2665 Yoaz.E.Bar-Sever@jpl.nasa.gov • Dr. Frank Bauer – Goddard Space Flight Center • 301-286-3102 Frank.Bauer@nasa.gov • Dave Affens - Goddard Space Flight Center • 301-286-9839 David.W.Affens@nasa.gov • Dr. Michael Moreau – Goddard Space Flight Center • 301-286-8382 Mike.Moreau@nasa.gov • Roger J. Flaherty – Goddard Space Flight Center • 301-286-7028 Roger.J.Flaherty@nasa.gov • Scott Murray – Johnson Space Center • 281-483-8242 Scott.V.Murray@nasa.gov • Dr. Scott Pace – NASA Headquarters • 202-358-1811 Scott.Pace@nasa.gov • Dr. A.J. Oria – Overlook Systems Technologies, Inc. / NASA HQ Ctr • 703-8931411 x 125 aoria@overlooksys.com Submit Inquiries to: