Aperture synthesis in optical astronomy; the current status

Abstract

A milestone in observational astronomy was achieved when the interferometric fringes of Lyrae (Vega) in the visible band were obtained in July 1974, by A. Labeyrie from an interferometer, called Interferometre a deux telescope (I2T), with a pair of independent telescopes on a North-South baseline conguration at Nice Observatory. These were the first fringes that are obtained by using the concept of merging speckles from both the telescopes. Such a success in synthesizing images impelled astronomers to venture towards ground-based very large arrays. Potentials for progress in the direction of developing large interferometric arrays of telescopes are expected to provide images, spectra of quasar host galaxies, exo-planets that may be associated with stars outside our solar system. Several interferometers using large telescopes (8-10 meters) have been successfully producing results since the dawn of this century and several new such instruments will be in operation soon both at ground, as well as in space. In view of the present scenario the current trend and the path to future progress in optical interferometry using diluted apertures are discussed.