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Journal of Astronomical Telescopes, Instruments, and Systems • Open Access

Improving active space telescope wavefront control using predictive thermal modeling
Author(s): Jessica Gersh-Range; Marshall D. Perrin

Paper Abstract

Active control algorithms for space telescopes are less mature than those for large ground telescopes due to differences in the wavefront control problems. Active wavefront control for space telescopes at L2, such as the James Webb Space Telescope (JWST), requires weighing control costs against the benefits of correcting wavefront perturbations that are a predictable byproduct of the observing schedule, which is known and determined in advance. To improve the control algorithms for these telescopes, we have developed a model that calculates the temperature and wavefront evolution during a hypothetical mission, assuming the dominant wavefront perturbations are due to changes in the spacecraft attitude with respect to the sun. Using this model, we show that the wavefront can be controlled passively by introducing scheduling constraints that limit the allowable attitudes for an observation based on the observation duration and the mean telescope temperature. We also describe the implementation of a predictive controller designed to prevent the wavefront error (WFE) from exceeding a desired threshold. This controller outperforms simpler algorithms even with substantial model error, achieving a lower WFE without requiring significantly more corrections. Consequently, predictive wavefront control based on known spacecraft attitude plans is a promising approach for JWST and other future active space observatories.

Paper Details

Date Published: 29 October 2014
PDF: 18 pages
J. Astron. Telesc. Instrum. Syst. 1(1) 014004 doi: 10.1117/1.JATIS.1.1.014004
Published in: Journal of Astronomical Telescopes, Instruments, and Systems Volume 1, Issue 1
Show Author Affiliations
Jessica Gersh-Range, Cornell Univ. (United States)
Marshall D. Perrin, Space Telescope Science Institute (United States)

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