The Thirty Meter Telescope (TMT) support and positioner assembly for its secondary mirror’s design is now complete. This achievement follows the successful completion of the Final Design Review (FDR) by the TMT International Observatory (TIO) for its Secondary Mirror Support System and Positioner Assembly (M2SSP). This is a critical system of the telescope that holds the secondary mirror (M2) and positions it to keep it always aligned and in focus. Passing the FDR means the M2SSP’s design is complete and marks a major milestone on the path to construction. The M2SSP contractor Advanced Mechanical and Optical Systems (AMOS) in Liège, Belgium, hosted the review from 10–12 June 2025.
The eight-member review panel included TIO stakeholders as well as members from National Optical-Infrared Astronomy Research Laboratory, National Research Council Canada, and retired experts from Lowell Observatory, Gemini Observatory, and TIO itself. The review was chaired by TIO’s Project Systems Engineer Dr. Gelys Trancho.
M2SSP FDR participants at AMOS in Belgium and remote
Presentations were made by AMOS and ADS-International (Italy), who is responsible for the M2 Positioner (M2POS) design. Together with the TIO Optics and Systems Engineering teams, they delivered a comprehensive FDR demonstrating the maturity, completeness, and compliance of the final design. The review evaluated design requirements, interface definitions, analysis and modeling results, verification planning, risk management, and plans for fabrication, integration, and maintenance. The team passed all of these evaluations and the review panel determined they are ready to go to the next phase to prepare for production: AMOS, ADS, TIO Optics and Systems Engineering teams are commended for achieving a mature final design within [just] 11 months after the [Preliminary Design Review]. The panel also praised the team’s collaboration, quality of documentation, resolution of all the last Preliminary Design Review items, and thorough responsiveness.
Additionally, the panel offered forward-looking recommendations for production and integration, including refinements to baffle handling, connector reliability, obsolescence planning, and ergonomic considerations during the Assembly, Integration, and Verification phase, along with a few other suggestions that align with ongoing development efforts. These thoughtful recommendations will guide the next phase of development leading up to the Production Readiness Review, the last review before production starts.
TMT M2SSP final design. The secondary mirror will be mounted in a stainless steel mirror cell (M2CA) that contains the axial and lateral supports for the mirror. An internal interface exists between the M2CA and the hexapod M2 positioner (M2POS). The M2POS interfaces with the Telescope Structure. Image credit: AMOS
TIO extends sincere gratitude to all members of the review panel, the AMOS and ADS teams, and the broader TIO community for their dedication, collaboration, and technical excellence. The successful completion of the M2SSP Final Design Review reflects the strength of international collaboration and the shared commitment to advancing one of the most ambitious astronomical observatories ever undertaken. With this achievement, the project continues forward with momentum and confidence toward production readiness and the realization of first light.
This material is based upon work supported by the National Science Foundation under Cooperative Agreement No. 2331108. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.