ELT optics polishing: year 1 report

Green light for the construction of the 39-m aperture Extremely Large Telescope (ELT) was given by the Council of the European Southern Observatory (ESO) on Dec 4th, 2014. Procurement of the key elements, especially the optics, the dome and structure and the glass substrates, was soon after initiated by ESO team. Safran Reosc is proud to have been awarded all the key optical polishing and testing contracts with: 2015-07: the contract for thin glass petals of the Adaptive Optics M4 mirror unit, 2016-07: the contract for polishing the 4-m secondary convex mirror M2, 2017-02: the contract for polishing of the 4-m tertiary mirror M3, 2017-05: the contract for polishing and integration of the 931 1.45-m hexagonal segments constituting the giant 39-m primary mirror assembly M1. This paper reports Safran Reosc’s work progresses along these four contracts with their various challenges and more specifically those related to the mass production of the M1 segments.