| Name: Alikhan Basheer |
| Affiliation: Indian Institute of Astrophysics |
| Conference ID: ASI2026_560 |
| Title: Fabrication & Qualification of Roundel Polishing for TMT at India-TMT Optics Fabrication Facility |
| Abstract Type: Poster |
| Abstract Category: Facilities, Technologies and Data science |
| Author(s) and Co-Author(s) with Affiliation: Alikhan Basheer(Indian Institute of Astrophysics), Pramod Panchal(Indian Institute of Astrophysics), Sanjeev Kumar Jha(Indian Institute of Astrophysics), Karthic Kumar(Indian Institute of Astrophysics), Prasanna Deshmukh(Indian Institute of Astrophysics), S Sriram(Indian Institute of Astrophysics) |
| Abstract: As a partner of Thirty Meter Telescope Project, India agreed to supply 84 Polished Segments to the project. All the 84 segments, which are non-axisymmetric aspheric in shape, need to fabricate within a short period of 4 years. To achieve this milestone in a short timeline, India-TMT transferred a unique technology from Coherent Inc. USA called the Stressed Mirror Polishing (SMP) technology. SMP technology allows to polish thin non-axisymmetric aspheric segments in a faster way compared to the conventional technology. Using the technology and trained manpower, India TMT polished first prototype roundel at India-TMT Optics fabrication facility (ITOFF) located at the CREST campus of Indian Institute of Astrophysics.
The prototype roundel was polished using the Coherent Equipment and met all the TMT requirements in terms of Surface figure, Mid spatial frequency error and surface roughness. All these parameters are verified using various metrology tools and the End Item Data Package (EIDP) was sent to TMT for third party verification. After analyzing the data, the TMT cleared the Fabrication Readiness Review and qualified India-TMT to produce TMT roundels.
The production of TMT roundels at ITOFF is planned in two phases. The Low-Rate Initial Production (LRIP) will begin in April 2026 and extends for 2 years, and the rate of production will be 9 roundels per year. After the completion of LRIP, ITOFF will enter full production, where the production rate will surge to 24 roundels per year. We report the roundel polishing technology, process, challenges, qualification and future plans for the TMT roundel production at ITOFF.
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