ZERODUR^® glass ceramic from SCHOTT is known for its very low thermal expansion coefficient (CTE) at room temperature and its excellent CTE homogeneity. It is widely used for ground-based astronomical mirrors but also for satellite applications. Many reference application demonstrate the excellent and long lasting performance of ZERODUR^® components in orbit. For space application a low CTE of the mirror material is required at cryogenic temperatures together with a good match of the thermal expansion to the supporting structure material. It is possible to optimize the coefficient of thermal expansion of ZERODUR^® for cryogenic applications. This paper reports on measurements of thermal expansion of ZERODUR^® down to cryogenic temperatures of 10 K performed by the PTB (Physikalisch Technische Bundesanstallt, Braunschweig, Germany, the national metrology laboratory). The ZERODUR^® TAILORED CRYO presented in this paper has a very low coefficient of thermal expansion down to 70 K. The maximum absolute integrated thermal expansion down to 10 K is only about 20 ppm. Mirror blanks made from ZERODUR^® TAILORED CRYO can be light weighted to almost 90% with our modern processing technologies. With ZERODUR^® TAILORED CRYO, SCHOTT offers the mirror blank material for the next generation of space telescope applications.

Date Published: 18 July 2014
PDF: 10 pages
Proc. SPIE 9151, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, 91512P (18 July 2014); doi: 10.1117/12.2055086

Published in SPIE Proceedings Vol. 9151:
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation
Ramón Navarro; Colin R. Cunningham; Allison A. Barto, Editor(s)