Detection and mitigation of radio frequency interference in SMOS data.

The Soil Moisture and Ocean Salinity (SMOS) mission was launched by ESA on November 2009 and it comprises a single payload Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) that measures the radiation emitted by the Earth in the protected frequency of 1.4 GHz (the L-band) and uses it to retrieve geophysical parameters. During the preparation of the mission it was foreseen that there might be some Radio Frequency Interference (RFI) affecting the data produced by SMOS and several algorithms to detect and flag the data were designed, but it has been shown at the early stages of the In-Orbit Commissioning Phase that these algorithms were un-effective. One of the first independent and self contained methods to detect, mitigate and flag data affected by RFIs was developed by DEIMOS Engenharia as part of the Level 1 Prototype Processor (L1PP) and it's fully functional since November 2010. The Detection Algorithm in L1PP uses the multi-angular SMOS data to detect the probable position of RFIs. The Mitigation Algorithm is based on a technique to remove the influence of point-like sources (like the Sun [1]) from SMOS data. The Flagging Algorithm has been developed with ESA and the Level 2 Teams so that geolocated pixels are flagged depending on the intensity of the RFI affecting them.