Control algorithm for the petal-shape segmented-mirror telescope with 18 mirrors

Atsushi Shimono; Fumihide Iwamuro; Mikio Kurita; Yuki Moritani; Masaru Kino; Toshinori Maihara; Hideyuki Izumiura; Michitoshi Yoshida

doi:10.1117/12.925828

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17 September 2012 Control algorithm for the petal-shape segmented-mirror telescope with 18 mirrors

Atsushi Shimono, Fumihide Iwamuro, Mikio Kurita, Yuki Moritani, Masaru Kino, Toshinori Maihara, Hideyuki Izumiura, Michitoshi Yoshida

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Proceedings Volume 8444, Ground-based and Airborne Telescopes IV; 84445Z (2012) https://doi.org/10.1117/12.925828
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

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.

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Atsushi Shimono, Fumihide Iwamuro, Mikio Kurita, Yuki Moritani, Masaru Kino, Toshinori Maihara, Hideyuki Izumiura, and Michitoshi Yoshida "Control algorithm for the petal-shape segmented-mirror telescope with 18 mirrors", Proc. SPIE 8444, Ground-based and Airborne Telescopes IV, 84445Z (17 September 2012); https://doi.org/10.1117/12.925828

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