The Simonyi Survey Telescope (formerly known as the Large Synoptic Survey Telescope) of the Rubin Observatory is an 8.4m telescope now in construction on Cerro Pachón, in Chile. This telescope has been designed to conduct a 10 years’ survey of the sky in which it will map the entire night sky every three nights. The Mirror Cell Assembly system is a 9x9m steel structure that provides positioning, support, figure correction and temperature control to the primary and tertiary mirror. It is composed of two main systems, the Support System and the Thermal Control System. The Support System provides positioning, support and figure control of the mirror as well as dynamic forces compensation. The Thermal Control System will control the bulk temperature and temperature variations throughout the mirror. The temperature variations produce thermal distortions of the mirror which produce image degrading distortion of the optical surface. Variations between the bulk temperature and the ambient degrade local seeing and can produce condensation. The mirror cell assembly was designed and build in Tucson, Arizona by the LSST engineering team, and was tested, to confirm correct integration, at the Richard F Caris Mirror Lab to confirm the optical performance of the system using the real glass mirror. After successful testing, the mirror cell assembly was disassembled, packed and shipped to the Cerro Pachón summit in Chile where it was integrated with the surrogate mirror, and installed on the telescope mount assembly (TMA) for system performance test. Once system performance test concluded, the mirror cell was transported to the maintenance level to remove the metal surrogate mirror, install the glass and coat. After coating the mirror, the mirror cell assembly will be integrated with the telescope mount assembly to conduct final testing and verification.
The Richard F. Caris Mirror Lab at the University of Arizona continues production of 8.4 m lightweight honeycomb segments for the primary mirror of the Giant Magellan Telescope. GMT’s 25 m primary mirror consists of a center segment surrounded by six off-axis segments, with an additional off-axis segment to allow continuous operation as segments are removed for coating. We cast the sixth segment (5 off-axis segments + center segment) in March 2021. As of June 2022 we have tentatively completed polishing of the third off-axis segment, and we are in the process of grinding the optical surface of off-axis Segment 5. For Segment 3, we improved the measurement accuracy for small-scale structure near the edge of the mirror, which has been a challenge for the off-axis segments. In addition to full-aperture interferometry and deflectometry, we used a 20 cm test plate to obtain high-resolution interferometric measurements of the edge.
The Richard F. Caris Mirror Lab at the University of Arizona continues production of 8.4 m lightweight honeycomb segments for the primary mirror of the Giant Magellan Telescope. GMT will have a center segment surrounded by six off-axis segments, plus an additional off-axis segment to allow continuous operation as segments are removed for coating. The second off-axis segment was completed and accepted in 2019. We are currently polishing the optical surface of off-axis Segment 3. We have completed work on the rear surfaces of Segment 4, the center segment, and offaxis Segment 5. We are assembling the mold for off-axis Segment 6 with the spin-casting scheduled for March 2021.
The Richard F. Caris Mirror Lab at the University of Arizona continues the production of 8.4 m lightweight honeycomb segments for the primary mirror of the Giant Magellan Telescope. GMT will have a center segment surrounded by six identical off-axis segments, plus an additional off-axis segment to allow continuous operation as segments are removed for coating. Production highlights of the last two years include the spin-casting of Segment 5, preliminary polishing of Segment 2, and completion of the rear surface processing for Segments 3 and 4. We completed a preliminary design of the significant modifications of the test systems required for Segment 4, the center segment. We finished an upgrade of the 8.4 m polishing machine; both the upgrade and experience gained with Segment 1 have contributed to much faster polishing convergence for Segment 2. Prior to polishing Segment 2, we verified the stability and accuracy of the measurement systems by re-measuring Segment 1, achieving good agreement among multiple independent tests as well as good agreement with the original acceptance tests of Segment 1.
The Richard F. Caris Mirror Lab at the University of Arizona is responsible for production of the eight 8.4 m segments for the primary mirror of the Giant Magellan Telescope, including one spare off-axis segment. We report on the successful casting of Segment 4, the center segment. Prior to generating the optical surface of Segment 2, we carried out a major upgrade of our 8.4 m Large Optical Generator. The upgrade includes new hardware and software to improve accuracy, safety, reliability and ease of use. We are currently carrying out an upgrade of our 8.4 m polishing machine that includes improved orbital polishing capabilities. We added and modified several components of the optical tests during the manufacture of Segment 1, and we have continued to improve the systems in preparation for Segments 2-8. We completed two projects that were prior commitments before GMT Segment 2: casting and polishing the combined primary and tertiary mirrors for the LSST, and casting and generating a 6.5 m mirror for the Tokyo Atacama Observatory.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.