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Proceedings Paper

Phasing of a space-based segmented submillimeter wavelength telescope using focal plane measurements
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Paper Abstract

As part of a technology development program for realizing a space based submillimeter telescope, two different approaches to the absolute phasing of a segmented primary mirror using focal plane measurements have been implemented for feasibility. The method of optimization by simulated annealing evaluates the image quality of a point spread function after all the telescope segments have been randomly moved. It accepts each iteration which improves the image quality, as well as a random number of iterations which do not, thus keeping the Strehl in the initialization procedure from falling into local maxima. Methods for determining the annealing schedule, and the step size for random segment movements are presented and discussed. Using phase diversity and a model for the telescope imaging system, a nonlinear least squares algorithm has also been implemented which parameterizes each of the segment actuator movements. Using multiple out of focus images, the segment actuator positions are estimated using an iterative procedure. Nonlinear least squares, although computationally intensive, offers a large savings in the actuator movements over simulated annealing and pairwise phasing methods for large numbers of segments. These algorithms have been integrated into a general simulation program which models the behavior of the telescope under anticipated space conditions.

Paper Details

Date Published: 10 July 1992
PDF: 14 pages
Proc. SPIE 1696, Controls for Optical Systems, (10 July 1992);
Show Author Affiliations
Bruce Martin Levine, Jet Propulsion Lab. (United States)
Stuart B. Shaklan, Jet Propulsion Lab. (United States)
Ty M. Buxman, Jet Propulsion Lab. (United States)
Philip J. Dumont, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 1696:
Controls for Optical Systems
John A. Breakwell, Editor(s)

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