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TMT Tertiary Mirror Preliminary Design Review Participants on 21 November 2019 at the TMT project office, CA - From Left: Robert Anderson, Fernando Santoro, Hugh Thompson, Guo Peng (CIOMP), John Rogers, Jiang Haibo (CIOMP), Tomas Chylek, Glen Cole, Tim Campbell (Campbell Consulting), Gary Muller (GMT), Fengchuan Liu, Luo Xiao (CIOMP), Myung Cho (NOAO). Remote Participants: Liu Jing (CIOMP) and Zhang Shixue (CIOMP) - Image Credit: TMT International Observatory

TMT Tertiary Mirror Passes Preliminary Design Review

Pasadena, CA – The design of the Thirty Meter Telescope’s Tertiary Mirror (M3) recently passed the first part of its Preliminary Design Review, which took place over two days in November 2019. The review panel, which included John Rogers (TMT Systems Engineering Deputy Group Leader, Chairperson), Gary Muller (GMT), Glen Cole (TMT), Hugh Thompson (TMT) and Fernando Santoro (TMT), assessed the progress made since the 2013 Conceptual Design Review, and mainly discussed the details of the M3 mirror fabrication (polishing and metrology) and the system’s structural and opto-mechanical designs.

The tertiary mirror system (M3S) is being developed at TMT’s partner organization Chinese Academy of Sciences’ Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) in Changchun, China.

TMT Tertiary Mirror System Team Meeting

TMT Project Office engineers with TMT Tertiary Mirror System engineers from the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences (CIOMP) in front of the CIOMP Institute in June 2019, at Changchun, China. From left to right: Fan Wengiang, Jiang Haibo, Guo Peng, Yang Fei, Jimmy Johnson, Mark Sirota, Peter Thompson, Tomas Chylek, Liu Jing, Zhang Shixue Image credit: TMT International Observatory / TMT China


TMT’s M3S consists of a 3.5m by 2.5m (11 ½ x 8 feet) flat elliptical mirror made from Schott’s low-expansion ceramic material Zerodur© mounted on a passive support system. It is articulated around two axes using direct drive motors to point and keep the telescope’s light-beam onto the various instruments located on the Nasmyth platform, all with exceptional accuracy. The control of M3S must also allow a rapid and precise switch between instruments, keeping the science target aligned with the instrument optical axis as the telescope changes its elevation angle.


TMT Tertiary Mirror System (M3S) Overview

TMT Tertiary Mirror System (M3S) Overview

Located in the center of the primary mirror, M3 is used to fold and steer the light path coming down from the secondary mirror, so the science beam can be delivered to any of the instruments active on the telescope. - Image credit: TMT International Observatory

Perspectives of TMT M3 System (M3S)

Perspectives of TMT M3 System (M3S) -  The M3 system includes the M3 Blank, the M3 Mirror (a 3.5m by 2.5m flat elliptical mirror), the upper portion of the tertiary mirror (M3) system Tower, the M3 Cell Assembly, the M3 Positioner Assembly, the interface hardware between the M3 System and the Telescope Assembly, and support for receiving, assembly, inspection and verification of the M3 System onto the TMT Telescope at the Observatory. TMT M3S will approximately weigh 12 tons  -  Image credit: TMT international Observatory















TMT’s review panel was charged with evaluating the M3S Preliminary Design against the functional, operational and interface requirements of the system. The panel found that the M3S requirements and enabling technologies have been adequately defined and developed to allow the M3S design to proceed to its Final Design phase.

“Engineers from CIOMP, selected in 2011 by the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) and the M3 design team at the Project Office, have received full approval to proceed to final design by the members of our multinational review panel,” said Tomas Chylek, TMT Senior Opto-Mechanical Engineer, and Workpackage Manager for the Tertiary Mirror System. “The review committee recognized that the M3S CIOMP team displays the expertise and cohesion required to successfully bring the design of the M3 system to maturity.”

For the review, the team of CIOMP engineers was represented by Guo Peng (mirror cell assembly), Luo Xiao (mirror polishing and metrology) and Jiang Haibo (M3 positioner). Additional expertise and assistance were provided by two leading opto-mechanical experts: Myung Cho (AURA) and Marvin Campbell (Campbell Consulting).

At the end of the two-day review, John Rogers, Chairperson, stated: “The M3S team members from CIOMP and TIO demonstrated they can develop a high-standard design for M3S. Significant design choices have been evaluated and accomplished with the expertise of computer-aided modeling and prototyping. M3S team is ready to proceed to final design.”

The second part of the M3S Preliminary Design Review is planned to take place in late 2020 and will cover aspects of system controls, safety, management and software.

TMT Tertiary Mirror (M3) Engineers from Changchun Institute of Optics, Fine Mechanics, and Physics, China.

TMT Tertiary Mirror (M3) Engineers from Changchun Institute of Optics, Fine Mechanics, and Physics, China. From left to right: Hu Haixiang, Luo Xiao, Qi Erhui, Hu Haifei Engineers from TMT China Changchun Group, in charge of the fabrication of TMT M3, are testing epoxy bonding pads on a 1/4 M3 prototype in Changchun lab. - Image credit: TMT International Observatory / TMT China

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