TOPEX

Launched on August 10, 1992, TOPEX/Poseidon was a joint satellite mission between NASA, the U.S. space agency; and CNES, the French space agency, to map ocean surface topography. The first major oceanographic research vessel to sail into space, TOPEX/Poseidon helped revolutionize oceanography by proving the value of satellite ocean observations. Oceanographer Walter Munk described TOPEX/Poseidon as "the most successful ocean experiment of all time." A malfunction ended normal satellite operations in January 2006.

Before TOPEX/Poseidon, scientists had only a brief glimpse of Earth's ocean as a whole from the pioneering, but short-lived Seasat satellite. TOPEX/Poseidon' radar altimeter provided the first continuous global coverage of the surface topography of the oceans. From orbit 1,330 kilometers above Earth, TOPEX/Poseidon provided measurements of the surface height of 95 percent of the ice-free ocean to an accuracy of 3.3 centimeters. The satellite's measurements of the hills and valleys of the sea surface led to a fundamental new understanding of ocean circulation and its effect on climate.

The mission's most important achievement was to determine the patterns of ocean circulation - how heat stored in the ocean moves from one place to another. Since the ocean holds most of the Earth's heat from the Sun, ocean circulation is a driving force of climate. TOPEX/Poseidon made it possible for the first time to compare computer models of ocean circulation with actual global observations and use the data to improve climate predictions.

While a three-year prime mission was planned, TOPEX/Poseidon delivered more than 10 years of data from orbit. In those years, the mission:

TOPEX/Poseidon was launched using an Ariane 42P expendable launch vehicle. Lift-off from Kourou in French Guiana took place on 1992-08-10. At lift-off the mass of the satellite was 2,402 kilograms (5,296 lb). The mission was named after the ocean TOPography EXperiment and the Greek god of the ocean Poseidon.

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