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Proceedings Paper

Aligning a more than 100 degrees of freedom wavefront sensor
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Paper Abstract

LINC-NIRVANA is the Fizeau beam combiner for the LBT, with the aim to retrieve the sensitivity of a 12m telescope and the spatial resolution of a 22.8m one. Despite being only one of the four wavefront sensors of a layer-oriented MCAO system, the GWS, which is retrieving the deformation introduced by the lower atmosphere, known to be the main aberration source, reveals a noticeable internal opto-mechanical complexity. The presence of 12 small devices used to select up to the same number of NGSs, with 3 optical components each, moving in a wide annular 2'-6' arcmin Field of View and sending the light to a common pupil re-imager, and the need to obtain and keep a very good super-imposition of the pupil images on the CCD camera, led to an overall alignment procedure in which more than a hundred of degrees of freedom have to be contemporary adjusted. The rotation of the entire WFS to compensate for the sky movement, moreover, introduces a further difficulty both in the alignment and in ensuring the required pupil superposition stability. A detailed description of the alignment procedure is presented here, together with the lessons learned managing the complexity of such a WFS, which led to considerations regarding future instruments, like a possible review of numerical versus optical co-add approach, above all if close to zero read-out noise detectors will be soon available. Nevertheless, the GWS AIV has been carried out and the system will be soon mounted at LBT to perform what is called the Pathfinder experiment, which consists in ground-layer correction, taking advantage of the Adaptive Secondary deformable Mirror.

Paper Details

Date Published: 13 September 2012
PDF: 15 pages
Proc. SPIE 8447, Adaptive Optics Systems III, 84476F (13 September 2012); doi: 10.1117/12.926773
Show Author Affiliations
Luca Marafatto, Univ. degli Studi di Padova (Italy)
Maria Bergomi, Univ. degli Studi di Padova (Italy)
INAF - Astronomical Observatory of Padova (Italy)
Alessandro Brunelli, INAF - Osservatorio Astronomico di Padova (Italy)
Marco Dima, INAF - Osservatorio Astronomico di Padova (Italy)
Jacopo Farinato, INAF - Osservatorio Astronomico di Padova (Italy)
Giancarlo Farisato, INAF - Osservatorio Astronomico di Padova (Italy)
Luigi Lessio, INAF - Osservatorio Astronomico di Padova (Italy)
Demetrio Magrin, INAF - Osservatorio Astronomico di Padova (Italy)
Roberto Ragazzoni, INAF - Osservatorio Astronomico di Padova (Italy)
Valentina Viotto, INAF - Osservatorio Astronomico di Padova (Italy)
Thomas Bertram, Max-Planck-Institut für Astronomie (Germany)
Peter Bizenberger, Max-Planck-Institut für Astronomie (Germany)
Matthieu Brangier, Max-Planck-Institut für Astronomie (Germany)
Florian Briegel, Max-Planck-Institut für Astronomie (Germany)
Albert Conrad, Max-Planck-Institut für Astronomie (Germany)
Fulvio De Bonis, Max-Planck-Institut für Astronomie (Germany)
Tom Herbst, Max-Planck-Institut für Astronomie (Germany)
Ralph Hofferbert, Max-Planck-Institut für Astronomie (Germany)
Frank Kittmann, Max-Planck-Institut für Astronomie (Germany)
Martin Kürster, Max-Planck-Institut für Astronomie (Germany)
Daniel Meschke, Max-Planck-Institut für Astronomie (Germany)
Lars Mohr, Max-Planck-Institut für Astronomie (Germany)
Ralf-Rainer Rohloff, Max-Planck-Institut für Astronomie (Germany)

Published in SPIE Proceedings Vol. 8447:
Adaptive Optics Systems III
Brent L. Ellerbroek; Enrico Marchetti; Jean-Pierre Véran, Editor(s)

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