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’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’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.