TOPEX/Poseidon

TOPEX/Poseidon was designed to measure global sea-surface topography using radar altimetry, providing continuous data on ocean circulation patterns, wave heights, and sea level changes. The mission revolutionized oceanography by producing the first global maps of ocean surface currents with unprecedented accuracy.

TOPEX/Poseidon was launched in August 1992 as a joint mission between NASA and CNES, the French space agency. The satellite operated far beyond its planned 3-to-5-year mission lifetime, continuing to return scientific data until it was decommissioned in January 2006.

TOPEX/Poseidon's success led directly to the Jason series of satellite altimetry missions, beginning with Jason-1 launched in 2001, which continued measuring sea-surface height. Together, these missions have provided a continuous, multi-decade record of global sea level rise that is critical for climate science.

The satellite used a radar altimeter to bounce microwave signals off the ocean surface and measure the round-trip travel time, from which the distance to the sea surface could be calculated with centimeter-level precision. This data, combined with precise orbit determination using GPS and laser ranging, allowed scientists to map ocean surface topography and infer underlying current systems.