Detection of RFI in Sentinel-3 (Surface Topography Mission) Microwave Radiometer data

Marie-Laure Frery (CLS, France)

Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)

Session: Instrument Processing: Propagation, Wind Speed and Sea State Bias

Presentation type: Type Forum

ML. Frery(1), M. Siméon(1), P. Féménias (2),F. Borde(3)
1 Collecte Localisation Satellite, Ramonville Saint Agne, France
2 European Space Agency, Frascati, Italy
3 European Space Agency, Noordwidjk, Netherlands

The Sentinel-3A Surface Topography Mission has been launched on February 2016 and will soon complete its second year of operation. Its objectives are to serve primarily the marine operational users but also allow the monitoring of sea ice and land ice, as well as inland water surfaces.
A two-channels microwave radiometer (23.8 and 36.5 GHz) like the Envisat and ERS MWR sensors is combined to the altimeter to correct the altimeter range for the excess path delay (WTC for wet tropospheric correction) resulting from the presence of water vapor in the troposphere.
Sentinel-3A orbit is such that its overflights the US KREMS radar facility in the Kwajalein atoll (9°23’47’’ N - 167°28’50’’ E) in the Pacific. For safety reasons, the MWR is switched to a specific mode about a given distance before the facility location and back to nominal mode after. The safing area was not large enough and in November 2018, Sentinel-3A MWR experienced a strong interference with a radar of the facility. This impacted the calibration parameters continuously monitored. But the overall performances of the instrument are maintained.
From the 17th January, the safing area was enlarged to 300km during the investigations. It was reduced to ~100km the 29th May 2019.
Following that event, investigations were carried out in order to find if other interferences had already happened, but with a smaller amplitude, and thus more difficult to detect.
We will present in this paper the method and results. We analyzed spectra of the brightness temperatures at MWR sampling rate (7Hz) in the scales smaller than the MWR resolution, where only instrument noise is expected. Several occurrences were detected around the KREMS facility, some quite far from the facility.

Marie-Laure Frery