Maximum Entropy Image Restoration in Astronomy

Imaging the two-dimensional intensity distribution of the sky has always been an important part of astronomy. This is particularly true at present, a time when aperture synthesis mapping is firmly established in radio astronomy, charge-coupled devices are revolutionizing optical imaging, and X-ray-imaging cameras are being flown in space. Atmospheric irregularities, instrument aberrations, detector noise, and the diffraction limit all cause the observed image to deviate from the ideal one. Image restoration techniques have therefore had a long history. The field owes much to the classic papers of Bracewell & Roberts ( 12) and Fellgett & Linfoot (35), which focused attention on the amount and nature of information about the image present in the measurements. These ideas have become increasingly relevant with the growth of interferometry, where the data correspond to the Fourier transform of the image. The Michelson stellar interferometer (82) was an early application in optical astronomy. However, it is at radio frequencies where interferometry has proved most fruitful and where astronomers have had to face the problem