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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)

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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 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

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