The Ocean Topography Experiment (TOPEX/Poseidon) is a cooperative project between the United States and France to develop and operate an advanced satellite system dedicated to observing the Earth's oceans. The mission provides global seal level measurements with an unprecedented accuracy. The data from TOPEX is used to determine global ocean circulation and to understand how the oceans interact with the atmosphere. This understanding will improve our ability to predict global climate.

For this joint mission, NASA provided the satellite bus and five instruments with their associated ground elements. The Centre National d'Etudes Spatiales (CNES) furnished two instruments with their associated ground elements and a dedicated launch on Ariane rocket. Both CNES and NASA provide precision orbit determination and process and distribute data to 38 science investigators from nine nations, as well as other interested scientists.