Prototype segments polishing and testing for ELT M1

摘要

Sagem – Reosc has been awarded by ESO a contract for the manufacturing and testing of seven prototype segments ofthe E-ELT primary mirror in 2008. The purpose of this contract was to demonstrate the ability to produce aspherical off-axishexagonal segments with very little edge effect and very high quality wavefront error and plan the production of the931 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 thebest segment integrated on its support an overall surface error of 23 nm RMS and 6 nm RMS after removal of theallowed amount of Focus, Astigmatism and Trefoil. This article will present the process developped by Sagem and itsperformance.Sagem has also assessed the performances of an alternate manufacturing process based on the polishing of the segmentsunder 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.