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Proceedings Paper

Cryogenic (70-K) measurement of an all-composite 2-m-diameter mirror
Author(s): Brian E. Catanzaro; Steven J. Connell; Mark Mimovich; Stan Backovsky; Grant Williams; James A. Thomas; Daniel D. Barber; Roger A. Johnston; Joseph C. Hylton; Kelly J. Dodson; Eri J. Cohen
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Paper Abstract

The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. As part of a JPL- funded effort to develop lightweight telescope technology suitable for this mission, COI designed and fabricated a spherical, F/1, 2 m aperture prototype primary mirror using solely carbon fiber reinforced polymer (CFRP) materials. To assess the performance of this technology, optical metrology of the mirror surface was performed from ambient to an intended operational temperature for IR-telescopes of 70K. Testing was performed horizontally in a cryogenic vacuum chamber at Arnold Engineering Development Center (AEDC), Tennessee. The test incorporated a custom thermal shroud, a characterization and monitoring of the dynamic environment, and a stress free mirror mount. An IR-wavelength phase shifting interferometer (IR PSI) was the primary instrument used to measure the mirror surface. From an initial surface figure of 2.1 microns RMS at ambient, a modest 3.9 microns of additional RMS surface error was induced at 70K. The thermally induced error was dominated by low-order deformations, of the type that could easily be corrected with secondary or tertiary optics. In addition to exceptional thermal stability, the mirror exhibited no significant change in the figure upon returning to room temperature.

Paper Details

Date Published: 5 November 2001
PDF: 18 pages
Proc. SPIE 4444, Optomechanical Design and Engineering 2001, (5 November 2001); doi: 10.1117/12.447305
Show Author Affiliations
Brian E. Catanzaro, CFE Services (United States)
Steven J. Connell, Composite Optics Inc. (United States)
Mark Mimovich, Composite Optics Inc. (United States)
Stan Backovsky, Composite Optics Inc. (United States)
Grant Williams, Composite Optics Inc (United States)
James A. Thomas, LightWorks Optics, Inc. (United States)
Daniel D. Barber, LightWorks Optics, Inc. (United States)
Roger A. Johnston, LightWorks Optics, Inc. (United States)
Joseph C. Hylton, Composite Optics Inc. (United States)
Kelly J. Dodson, Composite Optics Inc. (United States)
Eri J. Cohen, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 4444:
Optomechanical Design and Engineering 2001
Alson E. Hatheway, Editor(s)

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