Status of the serial production of 949 ZERODUR® ELT M1 segment blanks

Thomas Werner; Ralf Jedamzik; Thomas Westerhoff

doi:10.1117/12.2593439

24 August 2021 Status of the serial production of 949 ZERODUR® ELT M1 segment blanks

Thomas Werner, Ralf Jedamzik, Thomas Westerhoff

Proceedings Volume 11820, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems III; 1182009 (2021) https://doi.org/10.1117/12.2593439
Event: SPIE Optical Engineering + Applications, 2021, San Diego, California, United States

Abstract

The extremely large telescope (ELT) will be the largest telescope in the world with a primary mirror of 39 m aperture. In January 2019 SCHOTT has already successfully finished and delivered the 4.25 m ZERODUR® mirror blank for the secondary mirror (M2) of the extremely large telescope (ELT) of ESO, followed by 4 m ZERODUR® mirror blank for the tertiary mirror (M3) in January 2020. The ELT primary mirror M1 consists of 798 hexagonal mirror segments, each with slightly different aspherical shape to cope with the aspherical surface. Until 2024 SCHOTT will produce 949 cylindrical ZERODUR® mirror segment blanks (including spares) for the ELT M1 that will be polished and hexagonal shaped by SAFRAN REOSC in France. The production started in 2019 with the manufacturing of 18 verification blanks. The serial production started in December 2019 and will continue with roughly one blank per day until 2024. The ELT M1 specification requires tight tolerances on the scattering of the absolute CTE, high CTE homogeneity, excellent internal quality at the mirror surface and bonding interface with tight geometrical tolerances of the functional surface and back surface after acid etching. Generating high demands on the reproducibility of serial production in all relevant steps from melting, ceramization to CNC grinding and acid etching. This paper summarizes the status of the ELT M1 segment blank production at SCHOTT.

Conference Presentation

Citation Download Citation

Thomas Werner, Ralf Jedamzik, and Thomas Westerhoff "Status of the serial production of 949 ZERODUR® ELT M1 segment blanks", Proc. SPIE 11820, Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems III, 1182009 (24 August 2021); https://doi.org/10.1117/12.2593439

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