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Published January 2014 | public
Journal Article

Dynamic Analysis of the Actively-Controlled Segmented Mirror of the Thirty Meter Telescope

Abstract

Current and planned large optical telescopes use a segmented primary mirror, with the out-of-plane degrees of freedom of each segment actively controlled. The primary mirror of the Thirty Meter Telescope (TMT) considered here is composed of 492 segments, with 1476 actuators and 2772 sensors. In addition to many more actuators and sensors than at existing telescopes, higher bandwidths are desired to partially compensate for wind-turbulence loads on the segments. Control-structure interaction (CSI) limits the achievable bandwidth of the control system. Robustness can be further limited by uncertainty in the interaction matrix that relates sensor response to segment motion. The control system robustness is analyzed here for the TMT design, but the concepts are applicable to any segmented-mirror design. The key insight is to analyze the structural interaction in a Zernike basis; rapid convergence with additional basis functions is obtained because the dynamic coupling is much stronger at low spatial-frequency than at high. This analysis approach is both computational efficient, and provides guidance for structural optimization to minimize CSI.

Additional Information

© 2014 IEEE. Manuscript received March 12, 2012; revised November 2, 2012; accepted December 21, 2012. Manuscript received in final form January 12, 2013. Date of publication February 12, 2013; date of current version December 17, 2013. This work was supported in part by the Gordon and Betty Moore Foundation, the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the National Research Council of Canada, the Natural Sciences and Engineering Research Council of Canada, the British Columbia Knowledge Development Fund, the Association of Universities for Research in Astronomy (AURA), and the U.S. National Science Foundation. M. M. Colavita works at the Jet Propulsion Laboratory, California Institute of Technology, which is operated under contract for NASA. Recommended by Associate Editor G. Cherubini.

Additional details

Created:
August 19, 2023
Modified:
October 25, 2023