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Proceedings Paper

Control algorithm for the petal-shape segmented-mirror telescope with 18 mirrors
Author(s): Atsushi Shimono; Fumihide Iwamuro; Mikio Kurita; Yuki Moritani; Masaru Kino; Toshinori Maihara; Hideyuki Izumiura; Michitoshi Yoshida
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Paper Abstract

A 3.8 m segmented telescope is planned to be built at the Okayama Astrophysical Observatory by the joint program among Kyoto university, Nagoya university, NAOJ, and Nano-Optonics Energy Inc. This is the world’s first optical-infrared telescope whose primary mirror is composed of “petal-shaped” segment mirrors. To investigate the best layout of the displacement sensors as well as to study the control algorithm, we have developed a simulation software for the segmented petaloid mirrors. This simulator calculates the vertical position differences between the segments at the 60 displacement sensors based on the three-dimensional movements of the 54 actuators, and enables us to test the control algorithms under various conditions including random noise on the displacement sensors, random movement errors of the actuators, and unexpected lateral shifts of the segments. The outputs of the simulator are not only the phase error of the primary mirror but also the PSF image, taking the structure function of the optical surfaces into account. Using a singular value decomposition method, we found that the 18 petal-shaped segments are controllable within the required displacement errors of 15 nm under the following three conditions: 1) the displacement measurement sensors are placed in staggered fashion between segments, 2) the displacement measurement sensors are axisymmetrically placed with respect to the optical axis, and 3) the relative lateral shift and rotation of each segment are less than 500 μm and 0.05 degree, respectively. In this report, the control algorithm, requirements for the layout of the displacement measurement sensors, and the simulated performance will be presented.

Paper Details

Date Published: 17 September 2012
PDF: 8 pages
Proc. SPIE 8444, Ground-based and Airborne Telescopes IV, 84445Z (17 September 2012); doi: 10.1117/12.925828
Show Author Affiliations
Atsushi Shimono, The Univ. of Tokyo (Japan)
Fumihide Iwamuro, Kyoto Univ. (Japan)
Mikio Kurita, Kyoto Univ. (Japan)
Yuki Moritani, Kyoto Univ. (Japan)
Hiroshima Univ. (Japan)
Masaru Kino, Nagoya Univ. (Japan)
Toshinori Maihara, Nano-Optonics Energy Inc. (Japan)
Hideyuki Izumiura, National Astronomical Observatory of Japan (Japan)
Michitoshi Yoshida, Hiroshima Univ. (Japan)

Published in SPIE Proceedings Vol. 8444:
Ground-based and Airborne Telescopes IV
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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