A highly successful joint American/French satellite that, for almost a decade, has provided measurements of global sea levels accurate to within 4 cm. Its results have helped map ocean circulation patterns and improved our understanding of how the oceans interact with the atmosphere and our ability to predict the global climate. NASA/JPL (Jet Propulsion Laboratory) provided the satellite bus and five instruments, and is responsible for spacecraft operations; CNES (the French space agency) furnished two of the spacecraft’s instruments and the launch vehicle. Much of the payload was devoted to measuring the exact height of the satellite above the ocean using a laser altimeter and correcting the altimetry data for effects such as the delay of radio pulses because of water vapor in the atmosphere. TOPEX-Poseidon has proven so successful that a follow-on mission, Jason-1, was launched to extend sea-surface height measurements into the next decade.
