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Proceedings Paper

High-accuracy surface figure measurement of silicon mirrors at 80 K
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Paper Abstract

This report describes the equipment, experimental methods, and first results at a new facility at the Goddard Space Flight Center Optics Branch for interferometric measurement of cryogenically-cooled spherical mirrors. A mirror is cooled to 80 K and 20 K within a cryostat; and its surface figure error is measured through a fused-silica window using standard phase-shifting interferometry. The first mirror tested was a concave spherical silicon foam-core mirror with a clear aperture of 120 mm. The optic surface was measured at room temperature outside the dewar using standard "absolute" techniques; and then the change in surface figure error within the dewar from room temperature to 80 K was measured, and the two measurements added to create a representation of the two-dimensional surface figure error at 80 K, with a combined standard uncertainty of 3.4 nm rms. The facility and techniques will be used to measure the surface figure error at 20K of prototype lightweight silicon carbide and Cesic mirrors developed by Galileo Avionica (Italy) for the European Space Agency (ESA).

Paper Details

Date Published: 24 September 2004
PDF: 10 pages
Proc. SPIE 5494, Optical Fabrication, Metrology, and Material Advancements for Telescopes, (24 September 2004); doi: 10.1117/12.551738
Show Author Affiliations
Peter N. Blake, NASA Goddard Space Flight Ctr. (United States)
Ronald G. Mink, NASA Goddard Space Flight Ctr. (United States)
John Chambers, NASA Goddard Space Flight Ctr. (United States)
F. David Robinson, Orbital Sciences Corp. (United States)
NASA Goddard Space Flight Ctr. (United States)
David A. Content, NASA Goddard Space Flight Ctr. (United States)
Pamela Davila, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 5494:
Optical Fabrication, Metrology, and Material Advancements for Telescopes
Eli Atad-Ettedgui; Philippe Dierickx, Editor(s)

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