Active Laser Guide Star refocusing system for EAGLE instrument
Laboratoire d’Astrophysique de Marseille (LAM), 38 rue F. Joliot Curie, 13388
Marseille Cedex 13,
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We detail the study of a laser guide star (LGS) refocusing system based on an variable curvature mirror (VCM) of high dynamic, in the frame of the EAGLE instrument for the E-ELT. From the top level requirements, an on axis optical design based on an active component is optimised to ensure maximal performance in terms of encircled energy. The refocusing is operated by the VCM, which shape varies with the distance of the sodium layer to the telescope. The VCM system concept is based on an embedded metrology. We detail the finite element analysis (FEA) of the VCM, allowing an optimization of the thickness profile to get an optical quality better than λ/5 RMS at each curvature. Mechanical design and manufacturing of prototypes are also presented.
© Owned by the authors, published by EDP Sciences, 2010