Jason-1
Full Name: Jason-1
Phase: Operating
Launch Date: December 07, 2001
Mission Project Home Page: http://sealevel.jpl.nasa.gov/mission/jason-1.html
Program(s): Earth Systematic Missions
Jason is an oceanography mission to monitor global ocean circulation, improve global climate predictions, and monitor events such as El Nino conditions and ocean eddies. The Jason-1 satellite carries a radar altimeter, and it is a follow-on mission to the highly successful TOPEX/Poseidon mission, that measured ocean surface topography to an accuracy of 4.2 cm, enabled scientists to forecast the 1997-1998 El Niño, and improved understanding of ocean circulation and its effect of global climate. Jason-1 altimeter data is part of a suite of data provided by other NASA missions--the GRACE mission uses two satellites to accurately measure Earth's mass distribution, and the QuikSCAT scatterometer mission will measure ocean-surface winds. The Delta vehicle was shared with the Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) mission.
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.
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 our 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 about the heat stored in the ocean that, 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 by the Jet Propulsion Laboratory, Pasadena, Calif.