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Active Optics in Astronomy: Freeform Mirror for the MESSIER Telescope Proposal

Laboratoire d’Astrophysique Marseille (LAM), Aix Marseille Université (AMU) and CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille CX 13, France
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Math. Comput. Appl. 2019, 24(1), 2; https://doi.org/10.3390/mca24010002
Received: 28 November 2018 / Revised: 20 December 2018 / Accepted: 20 December 2018 / Published: 27 December 2018
(This article belongs to the Special Issue Related Problems of Continuum Mechanics)
Active optics techniques in astronomy provide high imaging quality. This paper is dedicated to highly deformable active optics that can generate non-axisymmetric aspheric surfaces—or freeform surfaces—by use of a minimum number of actuators. The aspheric mirror is obtained from a single uniform load that acts over the surface of a closed-form substrate whilst under axial reaction to its elliptical perimeter ring during spherical polishing. MESSIER space proposal is a wide-field low-central-obstruction folded-two-mirror-anastigmat or here called briefly three-mirror-anastigmat (TMA) telescope. The optical design is a folded reflective Schmidt. Basic telescope features are 36 cm aperture, f/2.5, with 1.6° × 2.6° field of view and a curved field detector allowing null distortion aberration for drift-scan observations. The freeform mirror is generated by spherical stress polishing that provides super-polished freeform surfaces after elastic relaxation. Preliminary analysis required use of the optics theory of 3rd-order aberrations and elasticity theory of thin elliptical plates. Final cross-optimizations were carried out with Zemax raytracing code and Nastran FEA elasticity code in order to determine the complete geometry of a glass ceramic Zerodur deformable substrate. View Full-Text
Keywords: telescope; active optics; aspherics; elasticity; optical design; deformable mirror telescope; active optics; aspherics; elasticity; optical design; deformable mirror
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Lemaitre, G.R.; Vola, P.; Muslimov, E. Active Optics in Astronomy: Freeform Mirror for the MESSIER Telescope Proposal. Math. Comput. Appl. 2019, 24, 2.

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