May 20, 2008
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.
Media contacts: 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
2008-078