Aktive Metallspiegel für Anwendungen in der satellitenbasierten Beobachtung

Satellite-based optical instrumentation suffers from static and low-frequency aberrations due to manufacturing of the optical components itself, thermally induced deformations, transport conditions or changes in gravity. For future space telescopes with primary mirrors larger than two meters, an active correction of these errors is strictly necessary. The present work shows the development of design guidelines for active metal mirrors for a long-term stable correction of static aberrations in satellite-based telescopes. The basis for this is the concept of a deformable mirror whose surface can be manipulated in a targeted manner by forces acting perpendicular to it. First, a model is developed with which the design parameters of the mirror substrate can be optimized with regard to the specific aberrations that should be corrected. The focus of this model are the optimization of the mechanical geometry and the position and distribution of the forces coupling into the mirror substrate. Through changes of the geometry, the actuator influence on the mirror surface and hence the compensation ability could be optimized. It is shown that the process of single-point diamond turning, which is used for the fabrication of passive metal optics, could be extended to fabricate high-quality active metal mirrors for space. Within this work, the final processing of the optical surface of a fully assembled deformable mirror is demonstrated. Using a prototype mirror, both the long-term stability as well as the compensation for application typical aberrations were experimentally proven. The present work shows that in consideration of the developed design guidelines, active metal mirrors whose implementation improves the performance of future satellite-based telescopes - can be manufactured.



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