Multichannel interference mitigation techniques in radio astronomy

Radio-astronomical observations are increasingly corrupted by radio frequency interference, and on-line detection and filtering algorithms are becoming essential. To facilitate the introduction of such techniques into radio astronomy, we formulate the astronomical problem in an array signal processing language and give an introduction to some elementary algorithms from that field. We consider two topics in detail: interference detection by rank estimation of short-term covariance matrices and spatial filtering by subspace estimation and projection. We discuss experimental data collected at the Westerbork Synthesis Radio Telescope and illustrate the effectiveness of the spacetime detection and blanking process on the recovery of a 3C 48 absorption line in the presence of GSM mobile telephony interference.