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Progress in the active development of large optics for astronomy

Rees, David Jon; (1994) Progress in the active development of large optics for astronomy. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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An international consortium consisting of the United States, United Kingdom, Canada, Brazil, Chile and Argentina are planning to revolutionize the field of astronomy by building the two GEMINI 8m astronomical telescopes. These are designed to provide unprecedented image quality, which should significantly increase our knowledge and understanding of the structure and dynamics of the universe. To provide such superb image quality, the specifications of almost every aspect of the telescope are tighter than for any other ever built. The work described in this thesis is part of the ongoing research currently being undertaken in the Optical Science Laboratory into the production of large, highly aspheric optical surfaces. Meeting the design specifications for the GEMINI secondary mirrors is believed to be impossible using conventional craft techniques, but it is expected to be a tractable problem when utilizing the Active Lap technique described herein. The goal of the project is to demonstrate this technique by producing a 1/3 scale model of these mirrors. Broadly speaking, the Active Lap uses closed loop control of a system comprising of arrays of load cells and force actuators to control the ablation of the mirror in real time. This is a significant step forward in the field, and aims to propel conventional craft techniques which date back to the time of Sir Isaac Newton into the 21st century! A major contribution of the author to the Active Lap research project was the data acquisition and control software, which was designed to be ergonomic and make efficient use of cpu time. Other significant contributions involved calibration methods, system testing, and development of the closed loop control algorithms. In particular the novel idea of utilizing artificial neural networks to replace these algorithms is discussed. Finally, the performance of the Active Lap is evaluated, and suggestions are made for both the strategy for its future use, and the investigations required for its future developments.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Progress in the active development of large optics for astronomy
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Large optics
URI: https://discovery.ucl.ac.uk/id/eprint/10097828
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