Douglas C.-J. Bock
Combined Array for Research in Millimeter-Wave Astronomy, University of California, Berkeley, California
Most array processing in astronomy is in radio astronomy. Arrays are used to obtain resolution and image quality unobtainable with single reflectors. The high image quality facilitates quantitative analysis and comparison with images at other wavelengths. Radio astronomy arrays can be divided into two main classes, beamforming arrays and correlation arrays. The beamforming arrays produce instantaneous summed array beams from a direction of interest. Correlation arrays provide images over the entire single-element primary beam pattern, computed off-line from records of all the possibles correlations between the antennas, pairwise. The next generation of instruments will use techniques from both types of instruments.
This chapter will focus primarily on correlation arrays, including their theory, design, and processing, but also mention aperture-plane phased arrays, focal-plane phased arrays, and array processing at optical and infrared wavelengths. It will follow the conventions usual in radio astronomy, although the results are applicable to (and increasingly used in) optical astronomy. The first part of array processing in radio astronomy occurs before the instrument is even built: the design of the ...