Obtaining information through the atmosphere at the diffraction limit of a large aperture

Abstract

An analysis is made which shows that if the pupil plane of a large telescope is relayed into a special achromatic prism interferometer of 180° rotational shear and with point symmetry, the second statistical moment of the pupil irradiance fluctuations reveals information about the source two-dimensional mutual coherence function (MCF) at spatial frequencies that, under ordinary conditions, are severely attenuated by propagation through the atmosphere. To obtain a measure of the MCF at points across the telescope pupil simultaneously, it is necessary to use a two-dimensional photo-electronic array detector, with real-time processing.