The Topex/Poseidon programme reflects CNES's expertise in satellite altimetry over nearly 30 years. Starting in 1968-69, French researchers submitted proposals for an altimetric satellite project called Dorade.

Since then, French technology has set the standards in this field, whether it be in laser observation, as used on all altimetry satellites, or in orbit determination, thanks to the Doris location system

French-US cooperation in Earth observation began in the 1970s. At that time, French teams actively participated in the analysis of data from the US GEOS 3 and Seasat altimetry programmes.

Cooperation between CNES and NASA increased with the Topex/Poseidon programme, the most important project managed jointly by the two countries

CNES and NASA have made Topex/Poseidon’s 50,000 daily measurements available to the scientific community since July 1993. More than 600 scientists from 54 countries currently have made use of these data, including 60 teams that work closely with the project engineers to provide long-term monitoring and continually improve performance.

Topex/Poseidon measurements were distributed via 2 data archive centres, one in the US, and the other in Toulouse, France at the Aviso centre (part of the ground segment SALP). This centre produces a monthly CD-ROM containing all the data collected by the satellite, amounting to nearly 2 million measurements per month. Since December 2001, the Jason programme, the successor to Topex/Poseidon, has also been delivering data which can be used in real time.

Observations made by Topex/Poseidon and -1are contributing to 2 major international scientific projects:

• WOCE (World Ocean Circulation Experiment), whose purpose was to collect in the 90's a complete set of ocean observations over a six-year period, on a global scale;
• TOGA (Tropical Ocean Global Atmosphere), a programme to observe climatic anomalies in the Pacific equatorial zone, set up in the 90's to improve our understanding of the role of tropical regions ;
• Clivar (Climate Variability and predictability programme), continuing work done under WOCE to study climate and ocean-ice-atmosphere interactions at global scale;
• Godae (Global Ocean Data Assimilation Experiment), from 2003-2005, setting the stage for a global pre-operational ocean monitoring and forecasting system, and Mersea, its European component.