Ocean topography experiment
From Glossary of Meteorology
Ocean Topography Experiment
(Acronym TOPEX.) A cooperative project between the United States and France to develop an advanced satellite system dedicated to observing the earth's oceans.
The TOPEX/Poseidon satellite, launched in September 1992, uses sophisticated altimeters to make sea level measurements in combination with a microwave radiometer to correct the altimeter measurements for changes in total water vapor content of the atmosphere, resulting in an absolute accuracy of about 4 cm.