Array signal processing for radio astronomy ∗

Radio astronomy forms an interesting application area for array signal processing techniques. Current synthesis imaging telescopes consist of a small number of identical dishes, which track a fixed patch in the sky and produce estimates of the time-varying spatial covariance matrix. The observations sometimes are distorted by interference, e.g., from radio, TV, radar or satellite tranmissions. We describe some of the tools that array signal processing offers to filter out the interference, based on eigenvalue decompositions and factor analysis, a more general technique applicable to partially calibrated arrays. We consider spatial filtering techniques using projections and interference subtraction, and discuss how a reference antenna pointed at the interferer can improve the performance. We also consider image formation and its relation to beamforming. Finally, we briefly discuss some future large scale radio telescopes.