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
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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: Measurement
Of the Earth and its
Potential Fields
Geoscience thru GNSS
IONOSPHERE
IONOSPHERE
OCEANS
OCEANS
ATMOSPHERE
ATMOSPHERE
Earth rotation
Polar motion
High resolution 3D
ionospheric imaging
Significant
wave height
Ionospheric structure & dynamics
Iono/thermo/atmospheric interactions
Onset, evolution
& prediction of
Space storms
Ocean geoid and
global circulation
Short-term eddy
scale circulation
TIDs and global
energy transport
Precise ion cal for
OD, SAR, altimetry
SOLID EARTH
SOLID
EARTH
Surface winds
and sea state
Climate change &
weather modeling
Shape and deformation of Earth
Global profiles of atmos
density, pressure, temp,
and geopotential height
Location & motion
of the geocenter
Structure, evolution
of the tropopause
Gross mass
distribution
Structure, evolution
of the deep interior
Precise global
reference frame
Atmospheric winds,
waves & turbulence
Tropospheric water
vapor distribution
Structure & evolution
of surface/atmosphere
boundary layer
International GNSS Service
Formerly the International GPS Service
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.
Many earth science missions and measurements, and
multidisciplinary applications, rely upon the openly-available
IGS products such as ephemerides and coordinate time series.
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.
GPS Applications in IGS Projects & Working Groups
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.
IGS Reference Frame
Timing and Precise Clocks
GLONASS Pilot Service Project
Ionosphere WG
Atmosphere WG
Sea Level - TIGA Project
Real-Time WG
Data Center WG
GNSS WG
Graph courtesy Analysis Coordinator G. Gendt, GFZ Potsdam
GNSS: Global Navigation Satellite System
http://igscb.jpl.nasa.gov
IGS 101
International GNSS Service
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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
Classic IGS station: short pillar
monument, choke ring antenna,
desirable VLBI co-location
(Pie Town, NM)
Photo courtesy of D. Stowers, JPL
Photo courtesy ESA/ESOC
Think you can solve for the snow
depth from this station’s data?
(Kiruna, Sweden)
Relocating a station to a better monumented spot (Thule, Greenland)
Photos courtesy F.B. Madsen, DNSC
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Fundamental point of departure for
projects, services or products
requiring geo-spatial information is a
uniform & reliable co-ordinate
reference frame.
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Over 50 countries in Africa each with
their own system and frame and some
with 2 or more systems.
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Although many areas are in conflict
there are also areas where peace has
been restored and require a lot of
development.
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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 a
TIFF (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):
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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 238-540
4800 Oak Grove Drive, Pasadena, CA
91109-8099
USA
tel: 818-354-8330
fax: 818-393-6686
ruth.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
GPS Precise Navigation - Low Earth Orbiters
CHAMP (Jul 2000)
GRACE (Mar 2002)
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GPS Flight Receiver
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LEO Missions Objectives/ Science
Goals include:
NRC Decadal Study notes GPS to
fly on board all 35 recommended
missions (January 2007)
– Atmospheric remote sensing
– Gravity, Magnetics
– Ionospheric remote sensing
– Ice and oceans
SAC-C (Nov 2000)
ICESat (Jan 2003)
JASON-1 (Dec 2001)
COSMIC (2005)
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
The CB has developed automated
methods to…
Cycle slips x1000/observations
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