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Ocean Surface Topography from Space
NEWSROOM
USA-FRANCE TANDEM SATELLITE MISSION SERVING UP FRESH SEA FARE
July 21, 2003

Article courtesy of JPL

Artists concept of the Tandem Mission
Artists concept of the Tandem Mission




Take one well-seasoned oceanography satellite, the joint
NASA-CNES (French Space Agency) TOPEX/Poseidon, nearing its
11th year in orbit to study the world's ocean circulation and
its effect on climate, mix in a fresh sibling satellite,
Jason, and add a dash of ingenuity, and you get what
scientists are calling the Jason-TOPEX/Poseidon tandem
mission.

Since last September, when the older spacecraft was
maneuvered into a tightly spaced orbit with Jason's, the two
have engaged in a spicy experimental orbital tango. The
spacecraft is serving up exceptionally high-resolution data
on the height of the world's ocean surfaces, a key measure of
heat storage in the ocean, that influences weather and future
planetary climate events. The experimental tandem mission
data will help scientists better detect and understand ocean
currents, tides and eddies.

In a paper in the American Geophysical Union newsletter Eos,
Dr. Lee-Lueng Fu, project scientist for the Jason and
TOPEX/Poseidon missions at JPL, reports the mission is
producing ocean surface topography data that reveal twice as
many details as seen before.

"The Jason-TOPEX/Poseidon tandem mission doubles the
resolution of ocean surface topography data, creating a
continuous, simultaneous record of superior-quality radar
measurements that will be used to map ocean surface current
speed and direction revealing important new information about
these energetic swirls that are often too small to be
resolved by a single satellite," Fu said. "Tandem mission
data will allow scientists to revise ocean models, improving
their ability to predict ocean currents in the future," he
said.

Fu said data from the mission is expected to improve our
knowledge of ocean tides in coastal and other shallow-water
regions, the changing transports of boundary currents, the
horizontal transport of heat in the oceans and other climate-
relevant properties. Also, it may validate theories of ocean
turbulence caused by the Coriolis force, a phenomenon caused
by Earth's rotation that deflects moving objects, such as
water or air, to the right in the northern hemisphere and to
the left in the southern hemisphere.

The data may provide valuable information about ocean eddies,
a type of ocean "weather." These intermediate-sized (30 to
120 miles across), ocean features generally last only a few
months, yet play an important role in transporting ocean
heat. Eddies help create ocean weather patterns and transport
nutrients from deep to shallower waters, where they enhance
the growth of marine life.

Beyond Jason and the tandem mission, scientists are
developing ways to achieve even higher resolution ocean
measurements without flying multiple conventional altimeters.
A Jason follow-on project, the Ocean Surface Topography
Mission, may carry a Wide-Swath Ocean Altimeter. It would
make wide-swath ocean surface height measurements using radar
interferometry. The wide-swath instrument would provide a
resolution of about nine miles on the ocean surface, an
eight-fold improvement in data resolution over the tandem
mission.

With Jason's instruments fully calibrated, NASA and CNES
released via the Internet Jason's first high accuracy science
data products. The products represent the final, validated
records of Jason altimetry data and associated background
information. Scientists around the world will use these
records to develop products and perform investigations. The
Jason science team has accumulated approximately 50, 10-day
cycles from the mission. These will be reprocessed over the
next several months to create a single data record for each
cycle. Future records will be made available to the public
about 35 days after spacecraft collection. Specialized
products are available to scientists.

Jason is continuing TOPEX/Poseidon's observations of ocean
surface topography, monitoring world ocean circulation,
studying interactions of the oceans and atmosphere, improving
climate predictions and observing events like El Niño.
Jason's onboard altimeter precisely maps the surface height
of 95 percent of Earth's ice-free oceans every 10 days to an
accuracy of about 1.33 inches. The spacecraft provides
continuous data on wind speed and wave height.

For information about Jason on the Internet, visit:

http://sealevel.jpl.nasa.gov/index.html
http://www.jason.oceanobs.com/html/portail/general/welcome_uk.php3

Data products are available on the Internet at:

http://podaac.jpl.nasa.gov/jason/jason_data_products.html
ftp://spike.cst.cnes.fr/pub/AVISO/JASON-1/


Source: Jet Propulsion Laboratory

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