Surface Water and Ocean Topography

Earlier altimetry missions — the Jason series and their predecessors — measured ocean and lake surface heights along narrow ground tracks, producing a sparse grid of sampled points. SWOT was designed to map rather than sample. Its Ka-band Radar Interferometer, KaRIn, scanned a 120 km wide swath on each orbit, collecting water-surface elevation data for rivers, lakes, reservoirs, and the open ocean at centimeter-scale precision.

The mission launched on 16 December 2022 aboard a Falcon 9 from Vandenberg into an 857 km orbit. Developed jointly by NASA and CNES with contributions from the Canadian Space Agency and the UK Space Agency, SWOT set out to conduct the first truly global survey of Earth's surface water — cataloguing freshwater bodies down to roughly 100 metres across and tracking how their levels shift over time.