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Proceedings Paper

Preliminary design study of the TMT Telescope structure system: overview
Author(s): Tomonori Usuda; Yutaka Ezaki; Noboru Kawaguchi; Kazuhiro Nagae; Atsushi Kato; Junji Takaki; Masaki Hirano; Tomoya Hattori; Masaki Tabata; Yasushi Horiuchi; Yusuke Saruta; Satoru Sofuku; Noboru Itoh; Takeharu Oshima; Takashi Takanezawa; Makoto Endo; Junji Inatani; Masanori Iye; Amir Sadjadpour; Mark Sirota; Scott Roberts; Larry Stepp
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Paper Abstract

We present an overview of the preliminary design of the Telescope Structure System (STR) of Thirty Meter Telescope (TMT). NAOJ was given responsibility for the TMT STR in early 2012 and engaged Mitsubishi Electric Corporation (MELCO) to take over the preliminary design work. MELCO performed a comprehensive preliminary design study in 2012 and 2013 and the design successfully passed its Preliminary Design Review (PDR) in November 2013 and April 2014. Design optimizations were pursued to better meet the design requirements and improvements were made in the designs of many of the telescope subsystems as follows: 1. 6-legged Top End configuration to support secondary mirror (M2) in order to reduce deformation of the Top End and to keep the same 4% blockage of the full aperture as the previous STR design. 2. “Double Lower Tube” of the elevation (EL) structure to reduce the required stroke of the primary mirror (M1) actuators to compensate the primary mirror cell (M1 Cell) deformation caused during the EL angle change in accordance with the requirements. 3. M1 Segment Handling System (SHS) to be able to make removing and installing 10 Mirror Segment Assemblies per day safely and with ease over M1 area where access of personnel is extremely difficult. This requires semi-automatic sequence operation and a robotic Segment Lifting Fixture (SLF) designed based on the Compliance Control System, developed for controlling industrial robots, with a mechanism to enable precise control within the six degrees of freedom of position control. 4. CO2 snow cleaning system to clean M1 every few weeks that is similar to the mechanical system that has been used at Subaru Telescope. 5. Seismic isolation and restraint systems with respect to safety; the maximum acceleration allowed for M1, M2, tertiary mirror (M3), LGSF, and science instruments in 1,000 year return period earthquakes are defined in the requirements. The Seismic requirements apply to any EL angle, regardless of the operational status of Hydro Static Bearing (HSB) system and stow lock pins. In order to find a practical solution, design optimization study for seismic risk mitigation was carried out extensively, including the performing of dynamic response analyses of the STR system under the time dependent acceleration profile of seven major earthquakes. The work is now moving to the final design phase from April 2014 for two years.

Paper Details

Date Published: 22 July 2014
PDF: 10 pages
Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91452F (22 July 2014); doi: 10.1117/12.2055767
Show Author Affiliations
Tomonori Usuda, National Astronomical Observatory of Japan (Japan)
Yutaka Ezaki, Mitsubishi Electric Corp. (Japan)
Noboru Kawaguchi, Mitsubishi Electric Corp. (Japan)
Kazuhiro Nagae, Mitsubishi Electric Corp. (Japan)
Atsushi Kato, Mitsubishi Electric Corp. (Japan)
Junji Takaki, Mitsubishi Electric Corp. (Japan)
Masaki Hirano, Mitsubishi Electric Corp. (Japan)
Tomoya Hattori, Mitsubishi Electric Corp. (Japan)
Masaki Tabata, Mitsubishi Electric Corp. (Japan)
Yasushi Horiuchi, Mitsubishi Electric Corp. (Japan)
Yusuke Saruta, Mitsubishi Electric Corp. (Japan)
Satoru Sofuku, Mitsubishi Electric Corp. (Japan)
Noboru Itoh, Mitsubishi Electric Corp. (Japan)
Takeharu Oshima, Mitsubishi Electric Corp. (Japan)
Takashi Takanezawa, Mitsubishi Electric Corp. (Japan)
Makoto Endo, Mitsubishi Electric Corp. (Japan)
Junji Inatani, National Astronomical Observatory of Japan (Japan)
Masanori Iye, National Astronomical Observatory of Japan (Japan)
Amir Sadjadpour, Thirty Meter Telescope Observatory Corp. (United States)
Mark Sirota, Thirty Meter Telescope Observatory Corp. (United States)
Scott Roberts, Thirty Meter Telescope Observatory Corp. (United States)
Larry Stepp, Thirty Meter Telescope Observatory Corp. (United States)

Published in SPIE Proceedings Vol. 9145:
Ground-based and Airborne Telescopes V
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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