NASA GNSS Applications & Geosciences Ruth E. Neilan Jet Propulsion Laboratory California Institute of Technology International GNSS Central Bureau Pasadena, CA Munich 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 PNT Policy Today: Space Based Position Navigation and Timing, December 2004

Geodesy: Measurement Of the Earth and its Potential Fields

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

International GNSS Service Formerly the International GPS Service Graph courtesy Analysis Coordinator G. Gendt, GFZ Potsdam IGS Reference Frame Timing and Precise Clocks GLONASS Pilot Service Project Ionosphere 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. Many earth science missions and measurements, and multidisciplinary applications, rely upon the openly-available IGS products such as ephemerides and coordinate time series. Atmosphere WG Sea Level - TIGA Project Real-Time WG Data Center WG GNSS WG GPS Applications in IGS Projects & Working Groups

IGS 101 International 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 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 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. Neilan International GNSS Service Central Bureau Jet Propulsion Laboratory MS Oak Grove Drive, Pasadena, CA USA tel: fax: 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/observations The 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