Astronomical radio interferometry

Radio interferometry and its application to arrays of element antennas enable sensitive studies of celestial objects with angular resolutions comparable with, or surpassing, optical imaging at wavelengths thousands of times shorter. The aperture synthesis technique offers the advantage of improving the angular resolution by effectively creating a telescope as large as the greatest separation between array elements. This Primer introduces radio interferometry systems that receive cosmic electromagnetic signals at submillimetre to metre wavelengths. First, the concept of aperture synthesis, the basic instrumental components and the calibration of data are described with an overview of currently operational astronomical arrays. The process of image synthesis and the factors that need to be considered in producing a radio astronomy image are described and common data formats and software applications for processing observation data are introduced. Various factors that limit the capabilities and/or optimization of arrays are outlined. Future plans for radio interferometry are presented to close the Primer. Arrays of element antennas in radio interferometry enable the study of celestial objects with angular resolutions comparable with, or surpassing, optical imaging at wavelengths thousands of times shorter. In this Primer, Asaki et al. describe aperture synthesis, the basic instrumental components and data calibration.