JASON 1 Mission Status 11 Jan 2002

The joint NASA/French Space Agency oceanography satellite
Jason 1 has reached its operational orbit and begun six months
of instrument calibrations with its sister spacecraft,
Topex/Poseidon.

Mission flight controllers at France’s Centre National
d’Etudes Spatiales’ (CNES) Satellite Control Center, Toulouse,
France, and NASA’s Jet Propulsion Laboratory, Pasadena,
Calif., yesterday commanded Jason 1 to fire its thrusters and
lower itself into its operational orbit of 1,337 kilometers
(830 miles). Jason 1 is now approximately one minute
(approximately 370 kilometers or 230 miles) ahead of the
Topex/Poseidon satellite, on an identical ground track.

Launched December 7, 2001 from Vandenberg Air Force Base,
Calif., Jason 1 was initially inserted into a 1,327 kilometer
(823 mile) orbit 10 kilometers (6 miles) below Topex/Poseidon.
A series of thruster maneuvers over the past five weeks
gradually placed Jason 1 into its current orbit.

Checkout of the spacecraft and its instrument payload is
now complete. All instrument and spacecraft functions and the
operations systems at the French space agency and JPL are
functioning nominally.

“Jason 1 has begun observations of the same spot of the
ocean surface as Topex/Poseidon under nearly identical
conditions,” said Dr. Lee-Lueng Fu, Jason 1 project scientist
at JPL. “These unprecedented observations will allow mission
scientists to calibrate and validate the new measurements from
Jason 1 with those of Topex/Poseidon. The combined data
records will enable us to study long-term changes in the ocean
and their effects on climate.”

Following completion of the calibration phase, plans are
for Topex/Poseidon to be placed in a parallel ground track
orbit midway between two adjacent Jason 1 ground tracks. The
paired spacecraft operations are expected to produce
observations with higher resolution than either satellite
could attain alone. This enhanced resolution will improve the
detection of ocean eddies, coastal tides and currents and will
have both scientific and practical applications.

The French space agency is expected to hand over routine
spacecraft operations to JPL in April. JPL will control the
satellite and its instruments for the remainder of the
mission, expected to last three years. The French control
center will continue to monitor the satellite, perform
navigation functions and conduct performance analyses.

Jason 1 will continue Topex/Poseidon’s observations of
ocean surface topography for monitoring world ocean
circulation, studying interactions of the oceans and
atmosphere, improving climate predictions and observing events
like El Nino.

JPL, a division of the California Institute of Technology
in Pasadena, manages the U.S. portion of the mission for
NASA’s Office of Earth Science, Washington, D.C.