Joint NASA-French Satellite to Track Trends in Sea Level, Climate

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Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Alan.buis@jpl.nasa.gov

Steve Cole 202-358-0918
NASA Headquarters, Washington
Stephen.e.cole@nasa.gov

NEWS RELEASE: 2008-078 May 20, 2008

Joint NASA-French Satellite to Track Trends in Sea Level, Climate

PASADENA, Calif. – A satellite that will help scientists better monitor and understand rises in
global sea level, study the world's ocean circulation and its links to Earth's climate, and improve
weather and climate forecasts is undergoing final preparations for a June 15 launch from
California's Vandenberg Air Force Base.

The Ocean Surface Topography Mission (OSTM)/Jason 2 is a partnership of NASA, the National
Oceanic and Atmospheric Administration (NOAA), the French Space Agency Centre National
d'Etudes Spatiales (CNES) and the European Organisation for the Exploitation of Meteorological
Satellites (EUMETSAT). The mission will extend into the next decade the continuous record of
sea-surface height measurements started in 1992 by the NASA-French Space Agency's
TOPEX/Poseidon mission and extended by the NASA-French Space Agency Jason 1 mission in
2001.

The satellite will continue monitoring trends in sea-level rise, one of the most important
consequences and indicators of global climate change. Measurements from TOPEX/Poseidon and
Jason 1 have shown that mean sea level has risen by about three millimeters (0.12 inches) a year
since 1993, twice the rate estimated from tide gauges in the past century. But 15 years of data are
not sufficient to determine long-term trends.

"OSTM/Jason 2 will help create the first multi-decadal global record for understanding the vital
roles of the ocean in climate change," said OSTM/Jason 2 project scientist Lee-Lueng Fu of
NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Data from the new mission will allow us
to continue monitoring global sea-level change, a field of study where current predictive models
have a large degree of uncertainty."

Developed and proven through the joint efforts of NASA and the French Space Agency, high-
precision ocean altimetry measures the height of the sea surface relative to Earth's center to
within about 3.3 centimeters (1.3 inches). These measurements, also known as ocean surface
topography, provide information on the speed and direction of ocean currents. Because sea
surface height is strongly influenced by the amount of heat in the ocean, it also is an indicator of
ocean heat storage in most places. Combining ocean current and heat storage data is key to
understanding global climate variations.

OSTM/Jason 2 marks the transition of high-precision altimetry data collection to the world's
weather and climate forecasting agencies. Scientists soon will be able to forecast how ocean
circulation will change from one season to the next and how that circulation is linked to climate
change and weather patterns.

"What began as an investment by NASA and CNES in research tools for studying the ocean has
matured into a proven technique that will now be routinely used by the world's weather and
climate agencies to make better forecasts," said Michael Freilich, director of the Earth Science
Division in NASA's Science Mission Directorate in Washington. "People in coastal areas will
benefit from improved near-real-time data on ocean conditions, while people everywhere will
benefit from better seasonal predictions resulting from the increased understanding of Earth
system processes enabled by these measurements."

OSTM/Jason 2 will ride to space aboard a NASA-provided United Launch Alliance Delta II
rocket, entering orbit about 10 to 15 kilometers (six to nine miles) below the 1,336-kilometer-
high (830-mile-high) orbit of Jason 1. OSTM/Jason 2 will use its thrusters to raise itself into the
same orbital altitude as Jason 1 and move in close behind its predecessor.

The two spacecraft will fly in formation, making nearly simultaneous measurements. For six to
nine months after launch, scientists will verify the instruments are calibrated precisely.
OSTM/Jason 2 then will continue Jason 1's former flight path, and Jason 1 will move into a
parallel ground track midway between two of the OSTM/Jason 2 ground tracks. This tandem
mission will double the amount of data collected, further improving tide models in coastal and
shallow seas and helping researchers better understand ocean currents and eddies. OSTM/Jason
2's mission is designed to last at least three years.

The OSTM/Jason 2 spacecraft, provided by the French Space Agency, carries five primary
instruments similar to those on Jason 1. Its main instrument is the Poseidon 3 altimeter, also
provided by the French Space Agency. NASA's Advanced Microwave Radiometer measures
atmospheric water vapor, which can distort the altimeter measurements. Three location systems
combine to precisely measure the satellite's position in orbit: NASA's Laser Retroreflector Array
and Global Positioning System Payload, and the French Space Agency's Doppler Orbitography
and Radio-positioning Integrated by Satellite instrument. Instrument improvements since Jason 1
will allow scientists to monitor ocean coastal regions with increased accuracy, nearly 50 percent
closer than in the past. Three experimental instruments round out the payload: the French Space
Agency's Environment Characterization and Modelisation-2 and Time Transfer by Laser Link,
and Japan's Light Particle Telescope.

JPL manages the mission for NASA's Science Mission Directorate. After on-orbit spacecraft
commissioning, CNES will hand over mission operations and control to NOAA. NOAA and
EUMETSAT will generate, archive and distribute data products.

For more on OSTM/Jason 2 on the Web, visit: http://www.nasa.gov/ostm .

JPL is managed for NASA by the California Institute of Technology in Pasadena.

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