Doppler Scatterometer

A Doppler scatterometer measures the radial velocity of the sea surface from the Doppler shift of the radar return, retrieving ocean surface current and wind at once rather than wind alone. NASA’s DopplerScatt is the airborne demonstrator: a Ka-band pencil-beam instrument at 35.75 GHz, mechanically scanned, resolving vector winds and currents at about 200 m over a swath near 24 km. The same approach underpins the proposed satellite Winds and Currents Mission concept, WaCM. Conventional scatterometers like ASCAT read backscatter for wind only; adding the Doppler velocity gives the current vector, which matters for drift, search and rescue, and air-sea exchange. The spaceborne version remains a mission concept, not yet flown.