Radio-frequency interference mitigation in radio astronomy

Radio-frequency interference (RPI) is an increasing problem for radio astronomy, given the ever-expanding use of the radio spectrum by both the communications industry (transmitting) and the radio astronomers (receiving). Regulation can protect a few windows in the radio spectrum, but many experiments now need to access parts of the spectrum outside the reserved regions. For example, spectral lines may be significantly Doppler shifted, and therefore require an observation window far from their rest frequencies. A variety of RPI-mitigation techniques has been developed in recent years. Most of these have analogs in other disciplines, but the specifics of the radio astronomers' experiments allow for some interesting refinements. As a rule, the astronomer is not interested in recovering a symbol stream in the data, seeking instead a more general description of the statistics. In this context, a number of post-correlation techniques become valuable and computationally viable.