Open issues for the Soil Moisture and Ocean Salinity (SMOS) satellite mission salinity retrieval

摘要

2006 will be a key date in ocean remote sensing. Two space missions are expected to be launched with the objective, for the first time, of measuring sea surface salinity (SSS) with a resolution and accuracy capable of providing valuable global coverage for ocean large-scale and climatic studies. The two missions, the European SMOS (Soil Moisture and Ocean Salinity) and the US Aquarius, employ low frequency (L-band) microwave radiometers but use different technology. The principles of microwave SSS remote sensing are well established. At L-band the sea surface brightness temperature measured by the radiometer is linked, through the sea water dielectric constant, to salinity. The same frequency, over land, can be used to determine soil moisture. This is the reason why the SMOS mission was proposed to ESA by an international group of land and ocean scientists with the objective of measuring both variables. SMOS employs an interferometric technology in the form of a Y-shaped polarimetric radiometer, which had been under development at ESA for several years (MIRAS, Microwave Imaging Radiometer by Aperture Synthesis).