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13 September 2012 Prototype segments polishing and testing for ELT M1
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Sagem – Reosc has been awarded by ESO a contract for the manufacturing and testing of seven prototype segments of the E-ELT primary mirror in 2008. The purpose of this contract was to demonstrate the ability to produce aspherical off-axis hexagonal segments with very little edge effect and very high quality wavefront error and plan the production of the 931 segments needed for the primary mirror and spares. The manufacturing of the prototype segments is now completed. They have been delivered. Sagem has achieved for the best segment integrated on its support an overall surface error of 23 nm RMS and 6 nm RMS after removal of the allowed amount of Focus, Astigmatism and Trefoil. This article will present the process developped by Sagem and its performance. Sagem has also assessed the performances of an alternate manufacturing process based on the polishing of the segments under stress conditions (Stress Mirror Polishing). The results obtained by this process will also be presented.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jacques Rodolfo, Laurent Chouarche, Gilles Chaussat, Anne-Laure Hamy, Jean-Louis Carel, Bruno Pernet, Jacques Billet, Hervé Leplan, and Eric Ruch "Prototype segments polishing and testing for ELT M1", Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 845023 (13 September 2012);

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