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Update on NASA Uses of GPS

11th GNSS WorkshopSeoul, South Korea4-5 November 2004

Dr. Scott PaceOffice of Space Communications

NASA Headquarters

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Vision for Space Exploration

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NASA Vision and MissionNASA Vision and Mission

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Topics for Discussion

Satellite Navigation ActivitiesNASA’s Contribution to IGS

Global Differential GPSTDRSS Augmentation Service

Launch Vehicle Tracking Search and Rescue

GPS Technologies & ApplicationsProbing the Earth

Geodesy and Oceanography Atmosphere and IonospherePrecision Orbit Determination

Formation FlyingFuture Developments

National Policy and Vision

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Satellite Navigation Activities -International GPS Service (IGS)

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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Satellite Navigation Activities -NASA’s Contribution to IGS

• IGS Central Bureau at JPL responsible for day-to-day management and coordination

– Significant international outreach activity for GPS and NASA– Network coordination for international standardization across ~80 agencies

• JPL Analysis Center, Network Operations, and Operational Data Center• Global Data Center at GSFC+• JPL/GSFC members on IGS Governing Board

• NASA GPS Stationso NASA Cooperative Stations• Other Agency Stations

Tracking Network of the International GPS Service

Highlighting NASA’s Contributions

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Satellite Navigation Activities –Global Differential GPS (GDGPS)

Uplink

Broadcast

TDRSS

Space users

Land lines

QuickTime™ and aPhoto - JPEG decompressor

are needed to see this picture.

Terrestrial usersIridium Inmarsat

Features:• 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

• Not certified for safety-of-life applications

For more information see:http://gipsy.jpl.nasa.gov/igdg

GDGPS Operations Center

Frame

Internet

NASA’s global real time network

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Satellite Navigation Activities -Powerful 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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Satellite Navigation Activities -TDRSS Augmentation Service for Satellites (TASS)

Under Development• TASS provides NASA’s GDGPS

corrections via TDRSS satellites

• Integrating NASA’s Ground and Space Infrastructures

• Provides user navigational data needed to locate the orbit and position of user satellites

47o W171o W

85o E

~18-20o

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Satellite Navigation Activities -Launch Vehicle Tracking

• Space-based navigation and range safety technologies are key components of the next generation launch and test range architecture

– Developed by NASA in conjunction with the Defense Department and the Federal Aviation Administration

– Provides a more cost-effective launch and range safety infrastructure while augmenting range flexibility, safety, and operability

Typical EastCoast Launch

Area

Typical WestCoast Launch

Area

East Coast TDRSCoverage Footprint(s)

West Coast TDRSCoverage Footprint(s)

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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

• 1997 Canadian Follow-On SAR System (FOSS) study showed MEO constellation would provide an optimal follow-on space platform

DASS• SAR Payloads to fly on the GPS satellite

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)

• Reduces search area from square km to square meters, reduce location time from hours to minutes.

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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GPS Technologies and Applications -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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Science – Geodesy and 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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Science – Atmosphere and Ionosphere

GPS Global Network occultation techniques• Global snapshots of ionospheric structure for

scientific research and space weather applications

GPS Receivers in Low-Earth Orbit• High-resolution soundings of atmospheric

properties (e.g. temperature) and ionospheric structure and irregularities

Occulting LEO

Occulting GPS

Calibrating GPS

Ground receiver

Ionosphere

Neutral atmosphere

EarthOcculted Signal

Technology Transfer to WAAS• Real-time software for GPS orbits, clocks, and

ionosphere maps• Enhanced ionosphere capability improved

safety/availability algorithms

Ionospheric Remote Sensing• Input to Navy/AF advanced space weather models• Improved navigation• Mitigate effects on communications• Improved geo-location and surveillance• Improved understanding of ionospheric response to

storms• Improve understanding of ionosphere-

magnetosphere coupling• Improve understanding of ionosphere-lower

atmosphere coupling

GPS Satellite Occultation Techniques

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GPS Technologies and Applications - Sample Precision Orbit Determination Activities

5 cm (20-cm real-time)operational automated processing

20000 km altitude

GPS

• 2-cm radial orbits (Topex GPS flight receiver, Motorola built to JPL specs)

• 1-cm radial orbits (Jason-1 GPS flight receiver, JPL Blackjack design)

operational automated processing

1336 km altitude

Geostationary36000 km altitude(TDRSS, QZSS)

1 m, ground-based trackingWith GPS < 10 cm

MicroLab/GPSMET730 km altitude

Shuttle Radar Topography Mission (SRTM): 230-km alt45-cm orbit accuracy

CHAMP: 470-km alt< 5-cm orbit accuracy

Recent Results with JPL-Built Blackjack Flight GPS Receivers

SAC-C: 705-km alt< 5-cm orbit accuracy

GRACE: 500-km alt (2 s/c)2-cm orbit accuracy10-psec relative timing1-micron K-band ranging

• Other JPL Blackjack GPS flight receivers in development: COSMIC (6 orbiters), PARCS (Space Station), and OSTM (Jason-2).

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GPS Technologies and Applications -Formation Flying

Summary• Technology will enable a large number of

spacecraft to be managed with minimum ground support.

• The result will be a group of spacecraft with the ability to detect errors and cooperatively agree on the appropriate maneuver to maintain their desired positions and orientations.

• Applicable to any mission class, low-Earth or Deep Space, that desires to fly multiple satellites autonomously.

Technology• Innovative use of fuzzy logic decision making

capabilities and natural language to resolve multiple conflicting constraints .

• Scripting environment to enable algorithm updates without software changes.

• Flight wrapper that interfaces directly with command & data handling subsystem for input & output.

• Multiple operating modes to allow execution control.

• Generic closed-loop formation flying control algorithms applicable to many missions.

• Modular architecture design.

Missions• Earth Observing (EO-1) &

Landsat 7• Aqua, CALIPSO, CloudSat,

Parasol, & Aura.

... and many others

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GPS-Based Technologies and Applications -The final frontier in navigation...

Another ‘GPS’ - Mars Network

• Integrated Navigation and Telecommunications• Develop a communications capability to provide a

substantial increase in data rates and connectivity from Mars to Earth

• Develop an in situ navigation capability to enable more precise targeting and location information on approach and at Mars.

http://marsnet.jpl.nasa.gov/

Terrestrial Planet Finder

• Objective: find Earth-like planets up to 45 light years away • Potential technologies include precision formation flying

• Several small telescopes acting as a very large one• ~1cm accuracy levels

http://planetquest.jpl.nasa.gov/TPF/tpf_index.html

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Backup Slides (Background Material)

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Contributors to this Presentation

• Dr. Lawrence Young – Jet Propulsion Laboratory– 818-354-5018 Lawrence.E.Young@jpl.nasa.gov

• Allen Farrington – Jet Propulsion Laboratory – 818-393-5260 Allen.H.Farrington@jpl.nasa.gov

• Dr. Yoaz Bar-Sever – Jet Propulsion Laboratory– 818-354-2665 Yoaz.E.Bar-Sever@jpl.nasa.gov

• Dr. Frank Bauer – Goddard Space Flight Center – 301-286-3102 Frank.Bauer@nasa.gov

• Dr. 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

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Satellite Navigation Activities -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 customers. – 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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Satellite Navigation Activities -GPS Integrity Monitoring with GDGPS

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

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20

25

30

35

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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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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 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• Four DASS capable satellites, Block IIRs, in-orbit

as of 2004• Preliminary results support feasibility analysis

DASS POC Ground Equipment• Antenna system installation completed 3rd quarter

2004• Ground station equipment acquisition underway• 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 begin