The TOPEX/POSEIDON mission is sponsored by NASA and the French space agency, Centre National D'Etudes Spatiales (CNES). The satellite uses radar altimetry to measure sea-surface height. The spacecraft carries six instruments: dual- and single-frequency radar altimeters, a microwave radiometer, a laser retroreflector array, a DORIS dual-frequency system receiver, and a GPS receiver. Four independent tracking systems, SLR, DORIS, TDRSS, and GPS, determine the position of the spacecraft within 10 cm.

TOPEX/POSEIDON Characteristics: