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Profiling the turbulent atmosphere and novel correction techniques for imaging and photometry in astronomy

By JAMES OSBORN

Abstract

The turbulent atmosphere has two detrimental effects in astronomy. The \ud phase aberration induced by the turbulence broaden the point spread function (PSF) and limits the resolution for imaging. If there is strong turbulence high in the atmosphere then these phase aberration propagate and develop into intensity fluctuations (scintillation). This thesis describes three novel instruments related to these problems associated with atmospheric turbulence. The first is an optical turbulence profiler to measure the turbulence strength and its position within the atmospheric surface layer in real-time. The instrument is a development of the slope detection and ranging (SLODAR) method. Results from the prototype at Paranal Observatory are discussed. An instrument to improve the PSF for imaging is also discussed. The instrument works by adaptively blocking the telescope pupil to remove areas which are the most out of phase from the mean. This acts to flatten the wavefront and can therefore be used after an adaptive optics system as an additional clean up, or stand alone on a telescope as a relatively affordable and easy way to improve the PSF. The third instrument reduces the scintillation noise for high precision fast photometry. Simulation results show that it is possible to reduce the scintillation noise to a level where the measurements are photon noise dominated

Topics: atmospheric turbulence, atmospheric correction, adaptive optics, scintillation
Year: 2010
OAI identifier: oai:etheses.dur.ac.uk:513
Provided by: Durham e-Theses

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