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Proceedings Paper

Ground layer correction: the heart of LINC-NIRVANA
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Paper Abstract

The delivered image quality of ground-based telescopes depends greatly on atmospheric turbulence. At every observatory, the majority of the turbulence (up to 60-80% of the total) occurs in the ground layer of the atmosphere, that is, the first few hundred meters above the telescope pupil. Correction of these perturbations can, therefore, greatly increase the quality of the image. We use Ground-layer Wavefront Sensors (GWSs) to sense the ground layer turbulence for the LINC-NIRVANA (LN) instrument, which is in its final integration phase before shipment to the Large Binocular Telescope (LBT) on Mt. Graham in Arizona.19 LN is an infrared Fizeau interferometer, equipped with an advanced Multi-Conjugate Adaptive Optics (MCAO) module, capable of delivering images with a spatial resolution equivalent to that of a ~23m diameter telescope. It exploits the Layer-Oriented, Multiple Field of View, MCAO approach3 and uses only natural guide stars for the correction. The GWS has more than 100 degrees of freedom. There are opto-mechanical complexities at the level of sub- systems, the GWS as a whole, and at the interface with the telescope. Also, there is a very stringent requirement on the superposition of the pupils on the detector. All these conditions make the alignment of the GWS very demanding and crucial. In this paper, we discuss the alignment and integration of the left-eye GWS of LN and detail the various tests done in the lab at INAF-Padova to verify proper system operation and performance.

Paper Details

Date Published: 21 July 2014
PDF: 13 pages
Proc. SPIE 9148, Adaptive Optics Systems IV, 91482R (21 July 2014); doi: 10.1117/12.2054988
Show Author Affiliations
Kalyan Kumar Radhakrishnan Santhakumari, Max-Planck-Institut für Astronomie (Germany)
Luca Marafatto, INAF - Osservatorio Astronomico di Padova (Italy)
Univ. degli Studi di Padova (Italy)
Maria Bergomi, INAF - Osservatorio Astronomico di Padova (Italy)
Valentina Viotto, INAF - Osservatorio Astronomico di Padova (Italy)
Jacopo Farinato, INAF - Osservatorio Astronomico di Padova (Italy)
Roberto Ragazzoni, INAF - Osservatorio Astronomico di Padova (Italy)
Tom Herbst, Max-Planck-Institut für Astronomie (Germany)
Thomas Bertram, Max-Planck-Institut für Astronomie (Germany)
Marco Dima, INAF - Osservatorio Astronomico di Padova (Italy)
Peter Bizenberger, Max-Planck-Institut für Astronomie (Germany)
Florian Briegel, Max-Planck-Institut für Astronomie (Germany)
Frank Kittmann, Max-Planck-Institut für Astronomie (Germany)
Lars Mohr, Max-Planck-Institut für Astronomie (Germany)
Demetrio Magrin, INAF - Osservatorio Astronomico di Padova (Italy)


Published in SPIE Proceedings Vol. 9148:
Adaptive Optics Systems IV
Enrico Marchetti; Laird M. Close; Jean-Pierre Véran, Editor(s)

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