ESA’s Soil Moisture and Ocean Salinity (SMOS) mission is dedicated to making global observations of soil moisture over land and salinity over oceans.

The SMOS satellite carries a novel interferometric radiometer that operates in the L-band microwave range to capture ‘brightness temperature’ images.

These images are used to derive global maps of soil moisture every three days, achieving an accuracy of 4% at a spatial resolution of about 50 km. Over oceans, SMOS maps salinity down to 0.1 practical salinity units (psu, averaged over 10–30 days in areas measuring 200 × 200 km).