A comparison of radio frequency interference within and outside of allocated passive earth exploration bands at 10.65 GHz and 18.7 GHz using the GPM microwave imager and windsat

Radio Frequency Interference (RFI) continues to be an annoyance to passive microwave remote sensing as spectrum demands escalate. For microwave imagers such as GMI and WindSat, the X-band and Ku allocated passive bands exhibit RFI from terrestrial based sources and from space-based geostationary satellites reflecting from the ocean, lakes, frozen ground, and other reflective surfaces. The GMI bands were designed to maintain the 3-dB bandpasses within the ITU allocated Earth Exploration-Passive bands, while WindSat, due to its sensitivity requirements, has much wider bandpasses. Both sensors have very similar viewing geometries, creating an ideal situation to address the question “Is it worth compromising radiometric sensitivity with lower bandwidths to stay within the allocated bands.” We find that the only benefit for these sensors of remaining within the allocated band is the elimination of reflected RFI from geosynchronous satellites around Europe at 10 GHz. Other than that, remaining within the protected bands appears to not provide much benefit.