The LSST M1/M3 combines an 8.4 m primary mirror and a 5.1 m tertiary mirror on one glass substrate. The combined mirror was completed at the Richard F. Caris Mirror Lab at the University of Arizona in October 2014. Interferometric measurements show that both mirrors have surface accuracy better than 20 nm rms over their clear apertures, in near-simultaneous tests, and that both mirrors meet their stringent structure function specifications. Acceptance tests showed that the radii of curvature, conic constants, and alignment of the 2 optical axes are within the specified tolerances. The mirror figures are obtained by combining the lab measurements with a model of the telescope's active optics system that uses the 156 support actuators to bend the glass substrate. This correction affects both mirror surfaces simultaneously. We showed that both mirrors have excellent figures and meet their specifications with a single bending of the substrate and correction forces that are well within the allowed magnitude. The interferometers do not resolve some small surface features with high slope errors. We used a new instrument based on deflectometry to measure many of these features with sub-millimeter spatial resolution, and nanometer accuracy for small features, over 12.5 cm apertures. Mirror Lab and LSST staff created synthetic models of both mirrors by combining the interferometric maps and the small high-resolution maps, and used these to show the impact of the small features on images is acceptably small.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/622424 |
| Date | 22 July 2016 |
| Creators | Martin, H. M., Angel, J. R. P., Angeli, G. Z., Burge, J. H., Gressler, W., Kim, D. W., Kingsley, J. S., Law, K., Liang, M., Neill, D., Sebag, J., Strittmatter, P. A., Tuell, M. T., West, S. C., Woolf, N. J., Xin, B. |
| Contributors | Univ Arizona, Steward Observ, Univ Arizona, Ctr Opt Sci, The Univ. of Arizona (United States), The Univ. of Arizona (United States), Large Synoptic Survey Telescope (United States), College of Optical Sciences, The Univ. of Arizona (United States), Large Synoptic Survey Telescope (United States), College of Optical Sciences, The Univ. of Arizona (United States), The Univ. of Arizona (United States), The Univ. of Arizona (United States), Large Synoptic Survey Telescope (United States), Large Synoptic Survey Telescope (United States), Large Synoptic Survey Telescope (United States), The Univ. of Arizona (United States), The Univ. of Arizona (United States), The Univ. of Arizona (United States), The Univ. of Arizona (United States), Large Synoptic Survey Telescope (United States) |
| Publisher | SPIE-INT SOC OPTICAL ENGINEERING |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | © 2016 SPIE |
| Relation | http://proceedings.spiedigitallibrary.org/proceeding.aspx?doi=10.1117/12.2234501 |
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