ADVANCES IN RADAR FORWARD AND INVERSE SCATTERING MODELS OF SUBSURFACE AND SUBCANOPY SOIL MOISTURE AND THEIR ROLE FOR THE AIRMOSS MISSION

The Airborne Observatory of Subcanopy and Subsurface (AirMOSS) is one of the five Earth Venture-1 missions selected in May 2010, and seeks to improve the estimates of the north American net ecosystem carbon exchange (NEE) through high-resolution observations of root zone soil moisture (RZSM). To obtain estimates of RZSM and assess its heterogeneities, AirMOSS will fly a P-band (430 MHz) synthetic aperture radar (SAR) over 2500 km(2) areas within nine major biomes of north America. Retrieval of RZSM in the presence of substantial vegetation requires the construction of accurate radar scattering models that account for diverse vegetation conditions as well as subsurface inhomogeneities. In this paper we provide a summary of recent advances in this area, emphasizing several coherent and incoherent models of scattering from multilayered inhomogeneous rough surfaces, as well as strategies for using these forward models in retrieval algorithms.