A robust algorithm for soil moisture retrieval from the soil Moisture Active Passive mission radar observations

The Soil Moisture Active Passive (SMAP) mission will combine spaceborne L-band radar and radiometer observations to provide improved estimates of Earth´s surface geophysical parameters. In this paper we present a new robust radar-only snapshot approach (independent of ancillary data on roughness and vegetation) for mapping near real-time soil moisture at high spatial resolution. Simple formulations are developed based on traditional theories and parameterizations are obtained using electromagnetic scattering basis available in the form of “data cubes”. This new algorithm is tested using Passive and Active L- and S-band (PALS) airborne data and in situ soil moisture observations acquired during different field campaigns, i.e., SGP99, SMEX02, CLASIC07 and SMAPVEX08. The soil moisture retrieval root mean square error observed is in the range of the quality target (0.06 cm³/cm³) set for the SMAP mission.