The oceans are a vital element of our planet’s equilibrium, occupying 70 % of the surface of the globe. Ever-changing, they are subject to influences from solar radiation, wind and atmospheric pressure at the surface, exchanges of heat with the atmosphere, land and ice as well as the rotation of the Earth. They also transport heat absorbed from the atmosphere, in their turn influencing the global climate.

Space technology provides oceanographers with global, real-time observation of the oceans, completed by in situ measurements which provide information from the surface down to deeper layers. Radar altimetry can calculate sea surface height, measuring variations to the nearest centimetre.

Following the success of the experimental Topex/Poseidon programme in 1992, its successor Jason-1 meets a new challenge with operational oceanography. It ensures service continuity for scientific research and the delicate task of preparating applications such as weather bulletins, charts to aid navigation and real-time monitoring of the seas.

Jason-2 was launched on June 20, 2008 on the same orbit as its predecessors. It responds to the needs of international programmes for studying and observing the oceans and climate, which are aiming to set up an ocean observation system (OSTM, the Ocean Surface Topography Mission) to cover the entire planet. Jason-2 is this mission's first satellite.

The OSTM will provide to scientific community high-resolution data on ocean currents and their variations, as well as sea surface height measurements. This mission, which is expected to last for 20 years, will be carried out by a series of satellites, with Jason-2, scheduled to be operational for fixe years, leading the way. Satellite data are available on Aviso's and NOAA's websites.

^{Last updated: August 2009}