SMOS L1 algorithms

The Level 1 Processing of SMOS transforms the data acquired by MIRAS (Microwave Imaging Radiometer with Aperture Synthesis) into geolocated TOA Brightness Temperatures, providing observation angles and additional parameters for the Level 2 Processor. Prior to SMOS launch in November 2009 the Level 1 Prototype Processor (L1PP) lead the way for specifying product types and contents, as well as to define, implement and validate all processing algorithms. During the six months of Commissioning, L1PP continued to be the testing environment for all new algorithms and proposed modifications to the Level 1 products. Particular emphasis should be given to LIPP´s capability to produce the first image from SMOS. Within less than three hours after the data acquisition at ESAC, L1PP generated images. L1PP has also been tuned to identify unforeseen hardware problems that have been spotted only with the satellite in-orbit. This paper is divided in 3 sections: I) a high level description of the LI processing strategy and functional blocks of the processor (called processing units); II) important results obtained during the In-Orbit Commissioning Phase (IOCP), namely for calibration optimization, image reconstruction improvement, geolocation assessment and the impact on scientific results, in particular, to insure optimal input to Level 2 Soil Moisture and Ocean Salinity retrieval; and III) conclusions from the Commissioning Phase.