SMOS (Soil Moisture and Ocean Salinity)

SMOS, Soil Moisture and Ocean Salinity, is ESA’s L-band mission launched 2 November 2009, the first satellite built to measure both fields. It carries MIRAS, a Y-shaped interferometric radiometer with 69 small antennas synthesizing a large aperture at 1.413 GHz to read brightness temperature at many incidence angles. From those it retrieves sea surface salinity to a few tenths of a practical salinity unit when averaged in space and time, plus surface soil moisture. L-band salinity from SMOS, SMAP, and the earlier Aquarius maps river plumes, evaporation-precipitation patterns, and the salinity that drives ocean density and circulation.