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Proceedings Paper

Flexure design development for a fast steering mirror
Author(s): Won Hyun Park; Andrew Corredor; Myung Cho; Young-Soo Kim; Ho-Sang Kim; Kyoung-Don Lee
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Paper Abstract

The fast steering mirror (FSM) is a key element in astronomical telescopes to provide real-time angular correction of line-of-sight error due to telescope jitter and wind-induced disturbance. The Giant Magellan Telescope (GMT) will utilize a FSM as secondary mirror under unfavorable wind conditions that excites the telescope at the lowest resonance frequency around 8Hz. A flexure in the center of the mirror constrains lateral displacements, while still allowing tip-tilt motion to steer. Proper design of this central flexure is challenging to meet lateral loading capability as well as angular and axial flexibility to minimize optical surface distortion forced by redundant constraints at the flexure. We have designed the lateral flexure and estimated its performance from a variety of design case studies in a finite element analysis tool. A carefully designed finite element model at the sub-system level including the flexure, lightweight mirror and 3 point axial supports allows evaluating whether the designed flexure is qualified within specifications. In addition, distorted surface maps can be achieved as a function of forces that could be induced in telescope operation or due to misalignment errors during assembling. We have also built a test set-up to validate the finite element analysis results. Optical quality was measured by a phase shifting interferometer in various loading conditions and the measurements were decomposed by standard Zernike polynomials to concentrate specific surface shapes and to exclude low order shapes as measurement uncertainties.

Paper Details

Date Published: 18 September 2013
PDF: 11 pages
Proc. SPIE 8836, Optomechanical Engineering 2013, 88360W (18 September 2013); doi: 10.1117/12.2025409
Show Author Affiliations
Won Hyun Park, College of Optical Sciences, The Univ. of Arizona (United States)
Andrew Corredor, The Univ. of Arizona (United States)
Myung Cho, National Optical Astronomy Observatory (United States)
Young-Soo Kim, Korea Astronomy and Space Science Institute (Korea, Republic of)
Ho-Sang Kim, Institute for Advanced Engineering (Korea, Republic of)
Kyoung-Don Lee, Institute for Advanced Engineering (Korea, Republic of)

Published in SPIE Proceedings Vol. 8836:
Optomechanical Engineering 2013
Alson E. Hatheway, Editor(s)

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