Evaluation and Application of Space Telescope Aberration Sensing Using Phase Diversity.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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Due to mechanical aspects of fabrication, launch, and operational environment, space telescope optics can suffer from unforeseen aberrations, detracting from their intended diffraction-limited performance goals. This dissertation gives the results of simulation and theoretical studies designed to explore how wavefront aberration information for such nearly diffraction-limited telescopes can be estimated via the Gonsalves least-squares phase diversity technique. In traditional phase diversity, aberrations are estimated from two images--one conventional, focused image and one image that has been defocused by a known amount. These studies are original and significant in that this effort represents the first time the effects of photon noise have been addressed for this relatively new aberration sensing technique. The effects of image-domain noise such as photon noise are of interest since the aberration estimates are derived from image-domain data. The analysis of this dissertation consists of simulation, theoretical investigation, and experimental application. Simulation studies incorporated models of the proposed Next Generation Space Telescope, as well a more generic, Zernike-aberrated model. Theoretical investigation involved deriving and numerically analyzing the Cramer-Rao lower bound for the phase diversity problem. The practical application dealt with diagnosing aberrations for an adaptive optical, ground-based telescope system.
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