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Proceedings Paper

Phase errors in gossamer membrane primary objective gratings
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Paper Abstract

A ribbon-shaped primary objective grating (POG) telescope lends itself to deployment in space, because it can be stowed for transport on a roll. Unlike mirrors which need to be segmented for sizes beyond the diameter of the fairing or payload bay, the ribbon is a continuous integral surface transported on a drum and unfurled during deployment. A flat POG membrane abandons a standard three dimensional figure requirement of mirrors and solves the problem of making primary objectives from tensile structures. Moreover, POG telescopes enjoy relaxed surface dimensional tolerances compared with mirrors. We have demonstrated mathematically and empirically that the tolerance for flatness relaxes as the receiving angle increases toward grazing exodus where the magnification of the POG is greatest. At the same time, the tolerance for phase error is worsened as the angle of reconstruction moves toward grazing exodus. The problem will be aggravated by the rigors of the space deployment environment. We give a mathematical treatment for the flatness and phase error. We mention engineering methods that could ameliorate the error.

Paper Details

Date Published: 12 July 2008
PDF: 8 pages
Proc. SPIE 7010, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 70104F (12 July 2008); doi: 10.1117/12.790222
Show Author Affiliations
Thomas D. Ditto, DeWitt Brothers Tool Co., Inc. (United States)
Joseph M. Ritter, Institute for Astronomy, Univ. of Hawaii (United States)

Published in SPIE Proceedings Vol. 7010:
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter
Jacobus M. Oschmann; Mattheus W. M. de Graauw; Howard A. MacEwen, Editor(s)

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