The SMOS end-to-end performance simulator: description and scientific applications

The SMOS Earth Explorer Opportunity Mission was selected in May 1999 by the European Space Agency to provide global and frequent soil moisture and sea salinity maps. SMOS´ single payload is MIRAS (Microwave Imaging Radiometer by Aperture Synthesis), an L-band two-dimensional aperture synthesis interferometric radiometer with multi-angular observation capabilities. Two-dimensional brightness temperature images are obtained by processing the cross-relations measured by pairs of signals collected by each of the 72 elements of a Y-shaped array. Due to the significant differences with respect to its radio-astronomy predecessors (larger number of receiving channels and wider field-of-view) during the past decade a detailed instrument error model was studied, as well as new calibration and image reconstruction techniques. The analysis of the overall performance of this complex instrument required the implementation of an end-to-end performance simulator (Camps, 1996; Corbella et al., 2003; Camps et al., 2002), which has been and it is currently being used in the technical design trade-off of the instrument. This software tool was also designed to help both the engineers working in the instrument and mission design and the scientific community in the implementation of new multi-angular algorithms for soil moisture and ocean salinity retrieval. This paper briefly describes the main functionalities and capabilities of the present and next versions of the SMOS End-to-end Performance Simulator (SEPS) and presents examples of application to the soil moisture (SM) and sea surface salinity (SSS) retrieval problems.