The Poseidon-2 Altimeter was the primary instrument aboard the Jason-1 spacecraft, and acquired data on ocean level, wave heights, and wind speed in real time. The altimeter sent radar pulses down to the surface of the ocean and measured the time it took for this signal to be reflected back to the satellite. 

Jason-1 was a follow-on to the highly successful Topex/Poseidon mission, and measured ocean-surface topography to an accuracy of 3.3 centimeters (1.3 inches). Topex/Poseidon enabled scientists to forecast the impact of the 1997–1998 El Niño and vastly improved the understanding of ocean circulation and its effect on global climate.