Radius of curvature matching for the Extremely Large Telescope M1

Camille Frapolli; Laurent-Daniel Haret; Justine Hatzigeorgopoulos; Julie Armougom; Sebastien Julienne; Rémi Bourgois; Renaud Mercier-Ythier; Nicolas Ferachoglou

doi:10.1117/12.3020290

26 August 2024 Radius of curvature matching for the Extremely Large Telescope M1

Camille Frapolli, Laurent-Daniel Haret, Justine Hatzigeorgopoulos, Julie Armougom, Sebastien Julienne, Rémi Bourgois, Renaud Mercier-Ythier, Nicolas Ferachoglou

Author Affiliations +

Proceedings Volume 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI; 131000N (2024) https://doi.org/10.1117/12.3020290
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

Since the fabrication of the Keck telescope primary mirror segments, radius of curvature matching have been known to be one of the major challenge in manufacturing segmented optics with high accuracy. Curvature is generally not a critical specification for optics as any error can be compensated by alignment (for a telescope mirror, by the distance between M1 and M2). However, for a segmented primary such as the ones in the Keck, GTC or ELT telescopes, a radius of curvature mismatch prevents from generating a continuous surface when assembling the mirror through a residual surface error called scalloping. We will present how this constraint drove the design of ELT metrology means, and how we achieved a radius of curvature metrology with 50 ppm absolute accuracy on a 71m curvature reference.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Camille Frapolli, Laurent-Daniel Haret, Justine Hatzigeorgopoulos, Julie Armougom, Sebastien Julienne, Rémi Bourgois, Renaud Mercier-Ythier, and Nicolas Ferachoglou "Radius of curvature matching for the Extremely Large Telescope M1", Proc. SPIE 13100, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation VI, 131000N (26 August 2024); https://doi.org/10.1117/12.3020290

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