Soil moisture and vegetation biomass retrievals using L band, dual polarised and multi angular radiometric data in preparation of the SMOS mission

The 2D L-band interferometer radiometer on board SMOS (Soil Moisture and Ocean Salinity) is based on an innovative bi-dimensional aperture synthesis concept. The sensor has new and very significant capabilities, especially in terms of multi-angular viewing configuration. In this study, the retrieval capabilities of SMOS, based on the actual system configuration have been assessed. From model simulations, the uncertainities on the retrieved variables is computed as a function of the uncertainties associated with both remotely sensed data (radiometric sensitivity ΔT, systematic bias) and model input parameters (errors are accounted for in the estimates of surface temperature and vegetation optical thickness, if one- or two-parameter retrievals are carried out). The simulations are performed using the τ-ω approach, which provides accurate simulations of the passive microwave signature of the land surface at L-band. This study shows how and why the 2D interferometry concept, applied to Earth remote sensing from space, may bring a major qualitative improvement, thanks to the ability to obtain many data over a significant range of viewing angles. SMOS is the first mission which aims at demonstrating and using this feature. From the results of this study, promising retrieval capabilities can be expected from SMOS over the land surface