The Ocean Topography Experiment (TOPEX/POSEIDON) is a cooperative project betweenthe United States and France to develop and operate an advanced satellite systemdedicated to observing the Earth's oceans. The mission provides global sea levelmeasurements with an unprecedented accuracy. The data from TOPEX/Poseidon is usedto determine global ocean circulation and to understand how the oceans interact withthe atmosphere. This understanding will improve our ability to predict global climate.

In the summer of 1992, TOPEX/POSEIDON was launched into orbit by an Ariane rocketfrom the European Space Agency's Space Center located in Kourou, French Guiana.From its orbit 830 miles (1,336 kilometers) above the Earth's surface, TOPEX/Poseidonmakes sea level measurements along the same path every 10 days using the dualfrequency altimeter developed by NASA and the CNES single frequency solid-statealtimeter. This information is used to relate changes in ocean currents with atmospheric and climate patterns. Measurements from NASA's Microwave Radiometer provide estimates of the total water-vapor content in the atmosphere, which is used to correct errors in the altimeter measurements. These combined measurements allow scientists to chart the height of the seas across ocean basins with an accuracy of 5 inches (13 centimeters).

TOPEX/POSEIDON is a vital part of a strategic research effort to explore ocean circulation and its interaction with the atmosphere. Results from the TOPEX/Poseidon will build the foundation for a continuing program of long-term observations of ocean circulation from space, and for an extensive ocean monitoring program in the next century.

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Last Modified: Fri Feb 12, 1999