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Title: Extending the limits of direct high angular resolution infrared astronomical imaging
Author: Brockie, Richard
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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Observing in the infrared (IR) part of the electromagnetic spectrum is now an established tool of astronomy. It allows investigations of, among others, high redshift galaxies, star formation regions and very low mass stars close to the hydrogen burning limit as well as providing information complementary to that obtained in other regions of the spectrum. The dimensions of infrared arrays have increased over the years from 62 x 58 in IRCAM1, the first infrared imager on the UK Infrared Telescope, to the 2562 array in IRCAM3, the current camera, soon to be superseded by 10242 arrays in the next generation of instruments. In this thesis, I describe the first observing programme which uses infrared observations to measure trigonometric parallaxes - made possible through the introduction of larger IR assays. In this programme, certain difficulties associated with infrared techniques are encountered and described with results presented for a previously measured star and a brown dwarf candidate. A major benefit of observing in the infrared is that atmospheric distortion has less of an effect on the formation of images - seeing on a good site can be < 0.5" at 2μm. The recent development of Adaptive Optics (AO) systems, which compensate for wavefront aberrations as observations are made, further reduce the effects of atmospheric distortion. AO systems have a servo-loop in which a deformable mirror attempts to remove the distortion present in the measured wavefront. In this thesis, I describe a method of real time characterisation of the most recent behaviour of the atmosphere, as observed by an AO system. Rather than reacting to the last measured distortion, this knowledge can be used in the servo-loop to reduce mirror fitting errors by predicting the next mirror shape. I describe a series of simulations which prove the validity of this novel technique. Finally, with simulations of the AO system being built for the William Herschel Telescope, I show that the improvement in performance available through prediction allows use of an AO guide star about 0.25 magnitudes fainter when compared with the non-predictive case.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available