Terrestrial and space-based RFI observed by the GPM microwave imager (GMI) within NTIA semi-protected passive earth exploration bands at 10.65 and 18.7 GHz

The Global Precipitation Measurement (GPM) Microwave Imager provides a valuable case study to evaluate levels and distribution of observable radio frequency interference (RFI) in semi-protected bands above 10 GHz from terrestrial and space-based sources. The GMI views the earth from a variety of different observation geometries and polarizations. The GMI detects significant earth-based RFI at 10.65 GHz over Europe, Middle East, Asia, and Mexico. In addition, 18.7 GHz channels GMI sense RFI reflected from the ocean, lakes, and frozen terrain in and around the continental United States originating from direct broadcast satellites. Over the first 2.5 years of GMI operations, the RFI levels have not significantly changed except over China, where 10 GHz RFI has significantly increased.