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Extracting Zero-Gravity Surface Figure of a MirrorThe technical innovation involves refinement of the classic optical technique of averaging surface measurements made in different orientations with respect to gravity, so the effects of gravity cancel in the averaged image. Particularly for large, thin mirrors subject to substantial deformation, the further requirement is that mount forces must also cancel when averaged over measurement orientations. The zerogravity surface figure of a mirror in a hexapod mount is obtained by analyzing the summation of mount forces in the frame of the optic as surface metrology is averaged over multiple clockings. This is illustrated with measurements taken from the Space Interferometry Mission (SIM) PT-Ml mirror for both twofold and threefold clocking. The positive results of these measurements and analyses indicate that, from this perspective, a lighter mirror could be used; that is, one might place less reliance on the damping effects of the elliptic partial differential equations that describe the propagation of forces through glass. The advantage over prior art is relaxing the need for an otherwise substantial thickness of glass that might be needed to ensure accurate metrology in the absence of a detailed understanding and analysis of the mount forces. The general insights developed here are new, and provide the basic design principles on which mirror mount geometry may be chosen.
Document ID
20110003010
Acquisition Source
Jet Propulsion Laboratory
Document Type
Other - NASA Tech Brief
External Source(s)
http://www.greendesignbriefs.com/component/content/article/9025
Authors
Bloemhof, Eric E. (California Inst. of Tech. Pasadena, CA, United States)
Lam, Jonathan C. (California Inst. of Tech. Pasadena, CA, United States)
Feria, Alfonso (California Inst. of Tech. Pasadena, CA, United States)
Chang, Zensheu (California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2011
Publication Information
Publication: NASA Tech Briefs, January 2011
Subject Category
Man/System Technology And Life Support
Report/Patent Number
NPO-47259
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20110002982Collected WorksNASA Tech Briefs, January 2011
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