First steps in ELT optics polishing

Abstract

Green light for the construction of the 39-m aperture giant Extremely Large Telescope (ELT) was given by the European Southern Observatory (ESO) council on Dec 4th, 2014. Procurement of the key elements, especially the optics, was immediately initiated by ESO team. Up today, Safran Reosc was awarded all the key optical polishing and testing contracts with: 2015-07: contract for the Adaptive Optics M4 mirror thin glass petals, 2016-07: contract for the 4-m M2 convex mirror, 2017-02: contract for the 4-m M3 mirror. 2017-05: contract for polishing and intergation of the 931 1.45-m hexagonal segments for the giant 39-m M1 mirror assembly This paper is dedicated to highlighting the various challenges linked to these various optical fabrication projects and reporting about the progress of our work so far.