Manufacturing of the ZERODUR 1.5-m primary mirror for the solar telescope GREGOR as preparation of light weighting of blanks up to 4-m diameter

Thomas Westerhoff; Martin Schäfer; Armin Thomas; Marco Weissenburger; Thomas Werner; Alexander Werz

doi:10.1117/12.856360

19 July 2010 Manufacturing of the ZERODUR 1.5-m primary mirror for the solar telescope GREGOR as preparation of light weighting of blanks up to 4-m diameter

Thomas Westerhoff, Martin Schäfer, Armin Thomas, Marco Weissenburger, Thomas Werner, Alexander Werz

Author Affiliations +

Proceedings Volume 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation; 77390M (2010) https://doi.org/10.1117/12.856360
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

Abstract

The 1.5 m primary ZERODUR® mirror of the solar telescope GREGOR incorporates 420 pockets at the backside for active cooling to avoid the thermal load impact of the sun deteriorating the observation. This design is also under consideration for the 2 m Indian Solar Telescope and for the 4.2 m European Solar Telescope (EST). The tip and tilt M5 mirror of the European Extremely Large Telescope (E-ELT) requires an even more demanding approach in light weighting. The approximately 3 m × 2.4 m elliptical flat mirror is specified to a weight of less than 500 kg. During the successful manufacturing of the GREGOR light weighted mirror, SCHOTT developed a systematic approach for processing such complex and long lead items which are capable for being up-scaled to a dimension of 4 m. In parallel SCHOTT has tested the machining of challenging aspect ratios of rib thickness and pocket height to prove the machinability of the E-ELT M5 design suggestions. The improved data on the bending strengths of ZERODUR® enable aggressive designs for light weighted 4 m class mirrors.

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Thomas Westerhoff, Martin Schäfer, Armin Thomas, Marco Weissenburger, Thomas Werner, and Alexander Werz "Manufacturing of the ZERODUR 1.5-m primary mirror for the solar telescope GREGOR as preparation of light weighting of blanks up to 4-m diameter", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77390M (19 July 2010); https://doi.org/10.1117/12.856360

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