On September 7, 2017, a TMT Primary Segment Assembly (PSA), fitted with an aluminum mirror segment, was successfully installed into the Multi-Segment Integration & Test (MSIT) facility at the TMT lab in Monrovia, California. This is the first time a PSA has been integrated into hardware in a way that accurately reflects how the segments will be installed into the final mirror cell of the Thirty Meter Telescope.
The bulk of the MSIT consists of the Mirror Cell Prototype (MCP), representing a subset of the mirror cell structure into which segments and their positioning systems are installed. The MCP will contain seven segments, about 1.5 percent of the total number in the actual mirror. It is intended as a test platform to allow TMT the opportunity, as early as possible, to work with hardware that is a close approximation of what will eventually be installed in the telescope.
“It allows us to verify 'form, fit and function' - in other words, to work with real, full-size components, to see how they fit together and are built up in assemblies of increasing complexity, and to understand how they work together as a whole,” says Chris Carter, TMT Telescope Controls Engineer. “TMT will gain experience with working in the 'mirror cell', installing and removing segments, verifying mechanical aspects of the design and then move on to the installation of actuators, edge sensors and their associated electronics, cabling and controllers. These activities not only help us verify that components, cabling and routing schemes will fit in the mirror cell but also allow us to perform extremely useful tests of basic edge sensor and actuator performance. Even though the aluminum segments are not identical to the final glass segments that will be used in the telescope, such testing is very valuable for gaining insight into the overall static and dynamic performance of the control systems involved.”
The installed Primary Segment Assembly is composed of prototype components made by various contractors in India and the USA. The Indian TMT Coordination Center (ITCC) is responsible for the production of all 492 Primary Mirror Segment Support Assemblies (M1 SSAs). The MSIT structure is a section of the full mirror cell, designed by Mitsubishi Electric Corporation (MELCO) and fabricated by Hitachi Zosen in Japan.
For more information on the MSIT, see the previous article “Major Milestone for TMT Multi Segment Integration and Test Facility”.