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Dr. Saku Tsuneta, TMT Board of Governor member, and also Director General of the National Astronomical Observatory of Japan (NAOJ), visits TMT technical laboratory on September 20, 2019, accompanied by TMT representatives. Photographed in front of one TMT primary mirror Segment Support Assembly (SSA), placed in a shipping container specially designed for safe transport of SSA units - From left: Robert Anderson (TMT), Saku Tsuneta (NAOJ) and Fengchuan Liu (TMT) - Image Credit: TMT International Observatory

TMT Board of Governor Member Dr. Saku Tsuneta Visits TMT Technical Lab

Pasadena, CA – 27 September 2019 –  Dr. Saku Tsuneta, Director General of the National Astronomical Observatory of Japan (NAOJ), recently met with TMT experts at the technical laboratory in Monrovia, California. Dr. Tsuneta also serves as a member of the TMT Board of Governors, which is accountable for both financial decision-making and strategic planning for the TMT International Observatory.

Robert Anderson, TMT Laboratory Manager and Acting-Environmental, Safety, and Health/Quality Assurance Group Leader, provided an overview of the lab activities to Dr. Tsuneta. The TMT lab was significantly expanded in 2015 and since then has enabled TMT engineers to conduct testing and prepare production of various telescope hardware and technical components.

The TMT technical lab is dedicated to:

- the testing and integration of TMT subsystems and components, such as prototypes of the primary mirror Segment Support Assembly and the Multi Segment Integration and Test (MSIT) facility (both discussed below)

- Verification of technical requirements and sequence of operational activities

- Research and development of technologies for TMT like TMT’s primary mirror cleaning system

The TMT’s primary mirror is made up of 492 Polished Mirror Assemblies (PMA), each consisting of one hexagonal polished mirror resting upon a support structure, the Segment Support Assembly (SSA). A total of 574 of these segments (including 82 spares) will be manufactured and shipped between several countries. SSAs are themselves manufactured in India and then shipped within India, as well as to China, Japan, and the United States, where the polished mirrors are mounted on the SSAs to become PMAs. All PMAs will then be shipped to a facility in Rochester, NY, for final polishing and ion beam figuring, and put into storage before being shipped to the observatory.

SSAs are opto-mechanical systems that will enable precise adjustment of the alignment and phasing of each mirror segment during nighttime astronomical observations. During the lab tour, Dr. Tsuneta was given a detailed explanation of the active mechanisms and sensors assemblies for the SSAs.

Specific containers - partially viewed on photographs - have been designed and fabricated to enclose and protect PMAs and SSAs from shocks, vibrations, and environmental factors during transport and storage, and be compatible with most major transport methods: water, air, road, and rail.

Throughout his career, Dr. Tsuneta has developed advanced types of instruments for space solar observations. He was very interested in the different activities at the lab, and in particular, the environmental tests for the SSAs’ warping harness system. With 21 actuators per segment, the automated warping harness system is an active-optic control system that will provide the ability to remotely control and correct the surface figure of each TMT primary mirror segment.

Prototypes of two TMT Primary Mirror Assemblies mounted on aluminum segment.

Prototypes of two TMT Primary Mirror Assemblies mounted on aluminum segment. These prototypes were assembled at the technical lab near Pasadena in California.                   Image Credit: TMT International Observatory


To date, three SSA models have been successfully assembled at the lab and are ready to be integrated into the TMT Multi Segment Integration and Test (MSIT) facility, also located at the lab.

The MSIT represents a subset of TMT primary mirror cell structure. It will include seven full-size (1.44m wide) aluminum segments and their positioning systems. It is intended as a test platform to enable work with actual TMT hardware and verify the functionality of all TMT Primary Mirror System components and assemblies prior to full-scale production.


For more information on the Multi Segment Integration and Test facility (MSIT), click here:

For more information on NAOJ and Dr. Tsuneta, click here:

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