SMOS

SMOS (Soil Moisture and Ocean Salinity), an ESA satellite launched in November 2009, is the first space mission dedicated to measuring global soil moisture over land and sea surface salinity over oceans. These two parameters are essential for improving weather forecasting, monitoring drought, and understanding the global water cycle and its role in climate change.

SMOS uses a novel instrument called MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), an L-band radiometer operating at 1.4 GHz that detects microwave radiation naturally emitted by Earth's surface. Because L-band signals are highly sensitive to water content in the top few centimeters of soil, scientists can derive soil moisture estimates at a spatial resolution of approximately 35–50 kilometers.

Yes, as of the mid-2020s, SMOS continues to operate well beyond its original three-year design life, having celebrated more than a decade of continuous science operations since its 2009 launch from Plesetsk Cosmodrome. ESA has extended the mission multiple times due to the ongoing uniqueness and scientific value of its L-band radiometer data.

SMOS flies in a sun-synchronous near-polar orbit at an altitude of approximately 758 kilometers, providing global coverage with a revisit time of about three days. This orbit ensures consistent illumination conditions for the radiometer measurements and enables regular coverage of the entire Earth's surface.