Launched in 1992, the Topex/Poseidon satellite ushered in a new era of earth studies. Its primary instrument was an "altimeter" ("high" - "measure").
Topex/Poseidon provided the first highly accurate, global measurements of sea level. This pioneering US/France collaboration has had three successors – all named Jason.
How can altimeters help us better understand our planet, now and in the future?