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Proceedings Paper

Minimizing high spatial frequency residual error in active space telescope mirrors
Author(s): Thomas L. Gray; Matthew W. Smith; Lucy E. Cohan; David W. Miller
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Paper Abstract

The trend in future space telescopes is towards larger apertures, which provide increased sensitivity and improved angular resolution. Lightweight, segmented, rib-stiffened, actively controlled primary mirrors are an enabling technology, permitting large aperture telescopes to meet the mass and volume restrictions imposed by launch vehicles. Such mirrors, however, are limited in the extent to which their discrete surface-parallel electrostrictive actuators can command global prescription changes. Inevitably some amount of high spatial frequency residual error is added to the wavefront due to the discrete nature of the actuators. A parameterized finite element mirror model is used to simulate this phenomenon and determine designs that mitigate high spatial frequency residual errors in the mirror surface figure. Two predominant residual components are considered: dimpling induced by embedded actuators and print-through induced by facesheet polishing. A gradient descent algorithm is combined with the parameterized mirror model to allow rapid trade space navigation and optimization of the mirror design, yielding advanced design heuristics formulated in terms of minimum machinable rib thickness. These relationships produce mirrors that satisfy manufacturing constraints and minimize uncorrectable high spatial frequency error.

Paper Details

Date Published: 27 August 2009
PDF: 11 pages
Proc. SPIE 7436, UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts IV, 74360M (27 August 2009); doi: 10.1117/12.824875
Show Author Affiliations
Thomas L. Gray, Massachusetts Institute of Technology (United States)
Matthew W. Smith, Massachusetts Institute of Technology (United States)
Lucy E. Cohan, Massachusetts Institute of Technology (United States)
David W. Miller, Massachusetts Institute of Technology (United States)


Published in SPIE Proceedings Vol. 7436:
UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts IV
Howard A. MacEwen; James B. Breckinridge, Editor(s)

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