ESA’s Soil Moisture and Ocean Salinity (SMOS) mission provides global measurements of L-band brightness temperatures, resulting in soil moisture and ocean salinity data sets from space. The mission objectives are:

(1) To provide global volumetric soil moisture estimates with an accuracy of 0.04 m3m-3 at a spatial resolution of 35-50 km and a temporal sampling of 1-3 days

(2) To provide global ocean salinity estimates with an accuracy of 0.1 practical salinity scale units for a 10-30 day average for an open ocean area of 200 x 200 km2,

(3) to provide daily sea ice thickness estimates based on MIRAS observations for the Northern hemisphere with a spatial resolution of a 10.000 km2 up to maximum values of 50 cm. SMOS observations additionally provide valuable information on vegetation and snow covered surfaces.


The payload of SMOS consists of the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument, a passive microwave 2-D interferometric radiometer, operating in L-band (1.413 GHz, 21 cm) within a protected wavelength/frequency band. The SMOS mission is based on a sun-synchronous orbit (dusk-dawn 6am/6pm). SMOS measurements are made over a range of incidence angles (0 to 55°) across a swath of approximately 1000 km with a spatial resolution of 35 to 50 km. MIRAS can provide measurements in dual and full polarisation, with the latter being its present operating mode.

Useful links to read about SMOS: