Launch date: December 7, 2001
Purpose: Measure sea surface heights

Jason 1 is an oceanography mission to monitor global ocean circulation, study the ties between the oceans and atmosphere, improve global climate forecasts and predictions, and monitor events such as El Niño conditions and ocean eddies.

It is a follow-on to the Topex/Poseidon mission, which has been measuring ocean topography since 1992. Like its predecessor, Jason 1 is a joint mission of the United States and France. These two satellites will provide a unique global view of the oceans that is impossible to acquire using traditional ship-based sampling.

Like Topex/Poseidon, Jason 1 will be able to measure the large and small hills and valleys of the ocean's surface. These measurements of ocean topography allow scientists to calculate the speed and direction of ocean currents and monitor global ocean circulation.

The global ocean is Earth's primary storehouse of solar energy. Jason 1's measurements of sea-surface height will reveal where this heat is stored, how it moves around Earth by ocean currents, and how these processes affect weather and climate.

Jason 1 has been designed to directly measure climate change through very precise millimeter-per-year measurements of global sea-level changes.

The Jason 1 satellite, its altimeter instrument and a position-tracking antenna have been built in France. The spacecraft will also carry a radiometer instrument to measure water vapor, a Global Positioning System receiver and a laser retroreflector array built in the United States. Jason 1 was launched in December 2001 from California's Vandenberg Air Force Base.

Weighing 500 kilograms (about 1,100 pounds), Jason 1 is one-fifth the size of Topex/Poseidon. After launch, Jason 1 will fly in tandem with Topex/Poseidon, doubling the science data return for as long as Topex/Poseidon remains in good health. Jason 1 will then assume Topex/Poseidon's former flight path. The mission is planned to last for five years.

More Information:
Topex/Poseidon - Jason 1 web page