SMOS Radiometer in the 1400–1427-MHz Passive Band: Impact of the RFI Environment and Approach to Its Mitigation and Cancellation

TLDR

The SMOS radiometer, launched in 2009, operates in the 1400–1427 MHz passive band and its soil‑moisture and ocean‑salinity images are heavily degraded by radio‑frequency interference, which can mask weaker signals and lead to underestimation or data loss, especially in Asia and Europe. ESA and SMOS partner teams have deployed multiple mitigation strategies to reduce RFI impact. Worldwide RFI sources have been identified, with up to 42 % suppressed through coordination with national spectrum authorities, and about 73 % of the strongest interference originates from Asia and Europe.

Abstract

The Soil Moisture and Ocean Salinity (SMOS) radiometer operates within the Earth Exploration Satellite Service passive band at 1400-1427 MHz. Since its launch in November 2009, SMOS images are strongly impacted by radio frequency interference (RFI). So far RFI sources distributed worldwide have been detected. Up to 42% of these RFIs could be suppressed thanks to the co-operation of the National Spectrum Management Authorities. Some of the strongest RFI sources might mask other weaker sources underneath, hence it is expected the total number of RFI detected may increase as strong ones are progressively identified and switched off. Most RFIs are located in Asia and Europe, which together hold ~73% of the active sources and of the strongest interference. The areas affected by RFI may experience either an underestimation in the retrieved values of soil moisture and ocean salinity or data loss, with the associated detrimental impact on the scientific return. ESA and the teams participating in SMOS mission have put in place different strategies to alleviate this RFI situation.