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Proceedings Paper

Stress polishing demonstrator for ELT M1 segments and industrialization
Author(s): Emmanuel Hugot; Anaïs Bernard; Marie Laslandes; Johan Floriot; Thibaut Dufour; Denis Fappani; Jean Marc Combes; Marc Ferrari
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Paper Abstract

After two years of research and development under ESO support, LAM and Thales SESO present the results of their experiment for the fast and accurate polishing under stress of ELT 1.5 meter segments as well as the industrialization approach for mass production. Based on stress polishing, this manufacturing method requires the conception of a warping harness able to generate extremely accurate bending of the optical surface of the segments during the polishing. The conception of the warping harness is based on finite element analysis and allowed a fine tuning of each geometrical parameter of the system in order to fit an error budget of 25nm RMS over 300μm of bending peak to valley. The optimisation approach uses the simulated influence functions to extract the system eigenmodes and characterise the performance. The same approach is used for the full characterisation of the system itself. The warping harness has been manufactured, integrated and assembled with the Zerodur 1.5 meter segment on the LAM 2.5meter POLARIS polishing facility. The experiment consists in a cross check of optical and mechanical measurements of the mirrors bending in order to develop a blind process, ie to bypass the optical measurement during the final industrial process. This article describes the optical and mechanical measurements, the influence functions and eigenmodes of the system and the full performance characterisation of the warping harness.

Paper Details

Date Published: 22 July 2014
PDF: 11 pages
Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 914539 (22 July 2014); doi: 10.1117/12.2055867
Show Author Affiliations
Emmanuel Hugot, Lab. d'Astrophysique de Marseille (France)
Anaïs Bernard, Lab. d'Astrophysique de Marseille (France)
Marie Laslandes, Space Structures Lab., California Institute of Technology (United States)
Johan Floriot, Lab. d'Astrophysique de Marseille (France)
Thibaut Dufour, Thales SESO (France)
Denis Fappani, Thales SESO (France)
Jean Marc Combes, Thales SESO (France)
Marc Ferrari, Lab. d'Astrophysique de Marseille (France)

Published in SPIE Proceedings Vol. 9145:
Ground-based and Airborne Telescopes V
Larry M. Stepp; Roberto Gilmozzi; Helen J. Hall, Editor(s)

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