The Dec. 7 launch of Jason 1, NASA’s newest oceanography
satellite, will continue the mission started by
Topex/Poseidon to monitor global climate interactions between
the sea and the atmosphere.
Jason 1 will monitor world ocean circulation, study
interactions of the oceans and atmosphere, improve climate
predictions and observe events like El Nino. Jason 1 is a
joint U.S./French oceanography mission.
“Jason 1 will be a tremendous asset to our oceanography
program. It will take the research and development activities
done so successfully on Topex/Poseidon and add operational
utility and function,” said Dr. Ghassem Asrar, associate
administrator for NASA’s Earth Science Enterprise, NASA
Headquarters, Washington.
Since the oceans are so large, remote sensing from satellites
has proved to be the only way to get global information about
these vast, hard-to-measure expanses. Spaceborne altimeters,
such as the Poseidon 2 instrument that Jason 1 carries, can
calculate ocean heights to within centimeters.
Gary Kunstmann, Jason 1 project manager at NASA’s Jet
Propulsion Laboratory, Pasadena, Calif., said, “We’re very
excited about this launch and looking forward to greater
knowledge of the ‘whys’ and ‘hows’ of the world’s climate
systems.”
Jason 1 is the follow-on to the very successful
Topex/Poseidon satellite, a U.S.-French mission that has been
making precise measurements of ocean-surface topography since
1992.
The ocean and atmosphere transport heat from the equatorial
regions toward the icy poles, and the atmosphere sends heat
through a complex, worldwide pattern of winds. As these winds
blow across the oceans, they help drive the currents and
exchange heat, moisture and gases with the water. While winds
create daily, short-term weather changes, the oceans have a
slower, much longer-lasting effect on climate. The powerful
forces of wind and water combine to help regulate the
planet’s climate.
Accurate observations of sea-surface height and ocean winds
provide scientists with information about the speed and
direction of ocean currents and the heat stored in the ocean,
which in turn reveals global climate variations. Jason 1 will
help scientists in their quest to understand these global
climate forces.
Weighing about 500 kilograms (about 1,100 pounds), Jason 1 is
only one-fifth the weight of Topex/Poseidon. After launch,
Jason 1 will enter orbit about 10 to15 kilometers (6 to 9
miles) below Topex/Poseidon’s 1,337-kilometer-altitude (830-
mile) orbit. During the next few weeks, Jason 1 will use its
thrusters to raise itself into the same orbital altitude as
Topex/Poseidon, and then move in close behind its
predecessor, trailing by about 500 kilometers (300 miles).
The two spacecraft will fly in formation, making nearly
simultaneous measurements. The science team will compare the
data to make sure the instruments are calibrated exactly.
This procedure is expected to take about six months. Jason 1
will then assume Topex/Poseidon’s former flight path, and the
older satellite will move into a parallel ground track midway
between two Jason 1 ground tracks. Jason 1’s mission is
designed to last three years.
Jason 1 carries five instruments: the Poseidon 2 altimeter,
the spacecraft’s main instrument, to measure altitude; a
microwave radiometer to measure atmospheric water vapor; and
three precision location-finding instruments.
Jason 1 is a joint project between NASA and France’s Centre
National d’Etudes Spatiales. The U.S. portion of the mission
is managed for NASA’s Office of Earth Science, Washington, by
the Jet Propulsion Laboratory, Pasadena, Calif.
More information about the Jason 1 program is available at:
and on the JPL home page at:
