Hypertelescope imaging

Abstract

Single aperture interferometry by means of speckle imaging has made inroads in several important fields in astrophysics. In recent years, the adaptive optics system at the telescope has produced spectacular results. However, the laperture of a telescope limits its resolving capacity. A diluted array of two or more telescopes is required to measure the brightness distribution across most stellar sources and many other objects of astrophysical importance. Such a technique, known as aperture synthesis, provides greater resolution of images than is possible with a single member of the array. Following the success of Interferometre a deux Telescope (I2T) and Grand Interferometre a deux Telescope (GI2T), the interferometry with phased arrays of multiple large sub-apertures has become a reality. These instruments are used to obtain results from the area of stellar angular diameters with implications for emergent fluxes, effective temperatures, luminosities and structure of the stellar atmosphere, dust and gas envelopes, binary star orbits with impact on cluster distances and stellar masses, relative sizes of emission-line stars and emission region, stellar rotation, limb-darkening, and astrometry. However, in order to obtain snapshot images of the astronomical sources, many-aperture optical array with arbitrarily diluted apertures is required to be built. The concept of `hypertelescope' approach to imaging, which is viewed as a simple modification of the classical Fizeau interferometer by employing pupil densification, has a vast potential, since large array of relatively small apertures is easy to implement. In view of the present scenario, after a brief presentation on the interferometric techniques, the current trend and the path to future progress in optical interferometry using hypertelescope concept will be discussed