Design and development status of the University of Tokyo Atacama Observatory 6.5m telescope

Tomoki Morokuma; Tsutomu Aoki; Mamoru Doi; Toshihiro Handa; Takafumi Kamizuka; Natsuko Kato; Kimiaki Kawara; Kotaro Kohno; Masahiro Konishi; Shintaro Koshida; Takeo Minezaki; Takashi Miyata; Kentaro Motohara; Shigeyuki Sako; Takao Soyano; Hidenori Takahashi; Yoichi Tamura; Toshihiko Tanabe; Masuo Tanaka; Ken'ichi Tarusawa; Yuzuru Yoshii

doi:10.1117/12.2054650

22 July 2014 Design and development status of the University of Tokyo Atacama Observatory 6.5m telescope

Tomoki Morokuma, Tsutomu Aoki, Mamoru Doi, Toshihiro Handa, Takafumi Kamizuka, Natsuko Kato, Kimiaki Kawara, Kotaro Kohno, Masahiro Konishi, Shintaro Koshida, Takeo Minezaki, Takashi Miyata, Kentaro Motohara, Shigeyuki Sako, Takao Soyano, Hidenori Takahashi, Yoichi Tamura, Toshihiko Tanabe, Masuo Tanaka, Ken'ichi Tarusawa, Yuzuru Yoshii

Author Affiliations +

Proceedings Volume 9145, Ground-based and Airborne Telescopes V; 91453C (2014) https://doi.org/10.1117/12.2054650
Event: SPIE Astronomical Telescopes + Instrumentation, 2014, Montréal, Quebec, Canada

Abstract

We here summarize the design and the current fabrication status for the University of Tokyo Atacama Observatory (TAO) 6.5-m telescope. The TAO telescope is operated at one of the best sites for infrared observations, at the summit of Co. Chajnantor in Chile, and is optimized for infrared observations. The telescope mount, mirrors, and mirror support systems are now at the final design phase. The mechanical and optical designs are done by following and referring to those of the Magellan telescopes, MMT, and Large Binocular Telescope. The final focal ratio is 12.2. The field-of-view is as wide as 25 arcmin in diameter and the plate scale is 2.75 arcsec mm⁻¹.

The F/1.25 light-weighted borosilicate (Ohara E6) honeycomb primary mirror is adopted and being fabricated by the Steward Observatory Mirror Laboratory. The primary mirror is supported by 104 loadspreaders bonded to the back surface of the mirror and 6 adjustable hardpoints. The mirror is actively controlled by adjusting the actuator forces based on the realtime wavefront measurement. The actuators are optimized for operation at high altitude of the site, 5640-m above the sea level, by considering the low temperature and low air pressure. The mirror is held in the primary mirror cell which is used as a part of the vacuum chamber when the mirror surface is aluminized without being detached from the cell.

The pupil is set at the secondary mirror to minimize infrared radiation into instruments. The telescope has two Nasmyth foci for near-infrared and mid-infrared facility instruments (SWIMS and MIMIZUKU, respectively) and one folded-Caseggrain focus for carry-in instruments. At each focus, autoguider and wavefront measurement systems are attached to achieve seeing-limited image quality.

The telescope mount is designed as a tripod-disk type alt-azimuth mount. Both the azimuthal and elevation axes are supported by and run on the hydrostatic bearings. Friction drives are selected for these axis drives. The telescope mount structure and primary mirror support as well as the mirrors are under thermal control and maintained at ambient air temperature to minimize the mirror seeing.

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Tomoki Morokuma, Tsutomu Aoki, Mamoru Doi, Toshihiro Handa, Takafumi Kamizuka, Natsuko Kato, Kimiaki Kawara, Kotaro Kohno, Masahiro Konishi, Shintaro Koshida, Takeo Minezaki, Takashi Miyata, Kentaro Motohara, Shigeyuki Sako, Takao Soyano, Hidenori Takahashi, Yoichi Tamura, Toshihiko Tanabe, Masuo Tanaka, Ken'ichi Tarusawa, and Yuzuru Yoshii "Design and development status of the University of Tokyo Atacama Observatory 6.5m telescope", Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91453C (22 July 2014); https://doi.org/10.1117/12.2054650

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