NASA GNSS Applications

& Geosciences

Ruth E. Neilan

Jet Propulsion Laboratory

California Institute of Technology

International GNSS Central Bureau

Pasadena, CAMunich GNSS Summit

March 8, 2007

Overview

• Early NASA role in GPS - historical perspective• GNSS for Geodesy and Geosciences• International GNSS Service (IGS)• Some photos of IGS stations• AFREF - Unification of African Reference Frames • Global Geodetic Observing System (GGOS)• Contact Info

Rear Admiral John D. Bossler, &Charles.W. Chalstrom

“GPS Instrumentation and Federal Policy”, Proceedings, First International Symposium on Precise Positioning with the Global Positioning System,

Vol. 1, Rockville, MD, May 1985

GPS Policy Affects Civil Use - 1980

PNT Policy Today: Space Based Position Navigation and Timing, December 2004

Geodesy: MeasurementOf the Earth and its

Potential Fields

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

Shape and defor-mation of Earth

Shape and defor-mation of Earth

Location & motionof the geocenter

Location & motionof the geocenter

Gross massdistributionGross massdistribution

Structure, evolution of the deep interior

Structure, evolution of the deep interior

Precise globalreference framePrecise global

reference frame

SOLID EARTHSOLID EARTH

Geoscience thru GNSS

International GNSS ServiceFormerly the International GPS Service

Graph courtesy Analysis Coordinator G. Gendt, GFZ Potsdam

IGS Reference FrameTiming and Precise Clocks GLONASS Pilot Service ProjectIonosphere WG

GNSS: Global Navigation Satellite System

The IGS is a voluntary federation of more than 200 worldwide agencies in more than 80 countries that pool resources and permanent GPS station data to generate precise GPS products.

Over 350 permanent tracking stations operated by more than 100 worldwide

agencies comprise the IGS network. Currently the IGS supports two GNSS:

GPS and the Russian GLONASS.

IGS products are formed by combining independent results from each of several Analysis Centers. Improvements in signals and computations have brought the centers’ consistency in the Final GPS satellite orbit calculation to ~ 2cm.

http://igscb.jpl.nasa.gov

Many earth science missions and measurements, and multidisciplinary applications, rely upon the openly-available IGS products such as ephemerides and coordinate time series.

Atmosphere WGSea Level - TIGA ProjectReal-Time WGData Center WGGNSS WG

GPS Applications in IGS Projects & Working Groups

IGS 101International GNSS Service

• Recognized as an international scientific service– Advocates an open data policy, equal access

• Mission statement: ‘… IGS provides the highest-quality GNSS data and products in support of the terrestrial reference frame, Earth rotation, Earth observation(s) and research, positioning, navigation and timing and other applications that benefit society….’ , Recent strategy planning meetings, December 2006.

• Name change GPS - GNSS in 2005 reflects incorporation of GLONASS and interest in incorporating Galileo

• Highest accuracy GPS & GLONASS satellite orbits available anywhere – -3-5 cm 3-d wrms GPS – ~25-30cm GLONASS– mm-level station positions and velocities

• Network of over 350+ stations precision geodetic receivers produce GPS data on a continuous basis – ~ 35 also track GLONASS – ~100 report hourly– Sub-network moving towards real-time for upcoming pilot project

Photo courtesy of D. Stowers, JPL

Classic IGS station: short pillar monument, choke ring antenna, desirable VLBI co-location

(Pie Town, NM)

Photo courtesy ESA/ESOC Think you can solve for the snow depth from this station’s data? (Kiruna, Sweden)

Photos courtesy F.B. Madsen, DNSC

Relocating a station to a better monumented spot (Thule, Greenland)

• Fundamental point of departure for projects, services or products requiring geo-spatial information is a uniform & reliable co-ordinate reference frame.

• Over 50 countries in Africa each with their own system and frame and some with 2 or more systems.

• Although many areas are in conflict there are also areas where peace has been restored and require a lot of development.

• Many private commercial enterprises are setting up own reference frames particularly in the oil industry.

AFREF is an African initiative to unify reference frames based on the ITRF through a network of GNSS / GPS base stations at spacing such the users will be at most within ~1000 km of a base station.IGS is very engaged in the support and dedicated to the success of AFREF since 2000.

AFREF Planning

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Cairo, Egypt, 2005 Planning Call for Participation

Cape Town, South Africa, July 2006, 1st Technical Workshop

Catch the Earth!GGOS is a program of the International

Association of Geodesy (IAG):

• Ensures observations of the three fundamental geodetic observables and their variations: Earth's shape, gravity field and rotational motion

• Integrates different geodetic techniques, models, and approaches to ensure long-term, precise monitoring of observables in agreement with the Integrated Global Observing Strategy (IGOS)

• Is a recognized member of the Global Earth Observing System of Systems (GEOSS)

• Is a powerful tool consisting mainly of high quality services (e.g., IGS), standards and references, and of theoretical and observational innovations

Contact Information

Ms. Ruth E. NeilanInternational GNSS Service Central BureauJet Propulsion LaboratoryMS 238-5404800 Oak Grove Drive, Pasadena, CA 91109-8099USAtel: 818-354-8330fax: 818-393-6686ruth.neilan@jpl.nasa.gov

Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National

Aeronautics and Space Administration.

Back-up Charts

GRACE (Mar 2002)

CHAMP (Jul 2000)

SAC-C (Nov 2000)

JASON-1 (Dec 2001)

ICESat (Jan 2003) COSMIC (2005)

• GPS Flight Receiver

• NRC Decadal Study notes GPS to fly on board all 35 recommended missions (January 2007)

• LEO Missions Objectives/ Science Goals include:

– Atmospheric remote sensing

– Gravity, Magnetics

– Ionospheric remote sensing

– Ice and oceans

GPS Precise Navigation - Low Earth Orbiters

IGS GLONASS Tracking Network and Final Orbit Comparisons

WHY IGS? Historical notes

– Geodynamics, geodetic, and space agency organizations realized the potential of GPS by late 1980’s

– Motivating goal: millimeter positioning in support of science & engineering anywhere in the world

– No single agency can or should assume the capital investment & recurring operations costs for the entire infrastructure

– Join with key international partners to form federation, define cooperation, set standards, driven by science quality

– Global framework for virtually all regional & national networks – Implement a global civilian GPS tracking system for science and

research– Participants are enthusiastic!– Later, more products (tropospheric, ionospheric…) from the same

rich data set

Network coordination

Cycle slips x1000/observationsThe CB has developed automated methods to…

Use Change Point Analysis to detect unreported changes or degrading equipment

Cycle slips x1000/observations

And compare an IGS site against all the others in mean and standard deviation of several data quality monitoring measures