News Release: 2003-102
July 21, 2003
USA-France Tandem Satellite Mission Serving Up Fresh Sea Fare
Take one well-seasoned oceanography satellite, the joint NASA-Centre
National d'Etudes Spatiales (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 are serving up
exceptionally high-resolution data on the height of the world's ocean
surfaces, a key measure of heat storage in the ocean, which 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 NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
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."
Fu said data from the mission are 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 (50 to 200 kilometers,
or 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 15 kilometers (9 miles) on the ocean surface, an
eight-fold improvement in data resolution over the tandem mission.
With Jason's instruments fully calibrated, NASA and the French Space
Agency 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 Nino. 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 3.3 centimeters (about 1.33 inches). The
spacecraft provides continuous data on wind speed and wave height.
For information about Jason on the Internet, visit:
Data products are available on the Internet at: