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Abstract. As future astrophysics missions require space telescopes with greater sensitivity and angular resolution, the corresponding increase in the primary mirror diameter presents numerous challenges. Since fairing restrictions limit the maximum diameter of monolithic and deployable segmented mirrors that can be launched, there is a need for on-orbit assembly methods that decouple the mirror diameter from the choice of launch vehicle. In addition, larger mirrors are more susceptible to vibrations and are typically so lightly damped that vibrations could persist for some time if uncontrolled. To address these challenges, we present a segmented mirror architecture in which the segments are connected edgewise by mechanisms analogous to damped springs. These mechanisms can be damped springs, flux-pinning mechanisms, virtual mechanisms, or any other device with the same basic behavior. Using a parametric finite-element model, we show that for low to intermediate stiffnesses, the stiffness and damping contributions from the mechanisms improve both the natural frequency and disturbance response of the segmented mirror. At higher stiffnesses, the mechanisms structurally connect the segments, leading to a segmented mirror that performs comparably to a monolith-or better, depending on the mechanism damping-with the modular design enabling on-orbit assembly and scalability.

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. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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