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Proceedings Paper

Experimental study of an optimised Pyramid wave-front sensor for Extremely Large Telescopes
Author(s): Charlotte Z. Bond; Kacem El Hadi; Jean-François Sauvage; Carlos Correia; Olivier Fauvarque; Didier Rabaud; Masen Lamb; Benoit Neichel; Thierry Fusco
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Paper Abstract

Over the last few years the Laboratoire d'Astrophysique de Marseille (LAM) has been heavily involved in R&D for adaptive optics systems dedicated to future large telescopes, particularly in preparation for the European Extremely Large Telescope (E-ELT). Within this framework an investigation into a Pyramid wave-front sensor is underway. The Pyramid sensor is at the cutting edge of high order, high precision wave-front sensing for ground based telescopes. Investigations have demonstrated the ability to achieve a greater sensitivity than the standard Shack-Hartmann wave-front sensor whilst the implementation of a Pyramid sensor on the Large Binocular Telescope (LBT) has provided compelling operational results.1, 2

The Pyramid now forms part of the baseline for several next generation Extremely Large Telescopes (ELTs). As such its behaviour under realistic operating conditions must be further understood in order to optimise performance. At LAM a detailed investigation into the performance of the Pyramid aims to fully characterise the behaviour of this wave-front sensor in terms of linearity, sensitivity and operation. We have implemented a Pyramid sensor using a high speed OCAM2 camera (with close to 0 readout noise and a frame rate of 1.5kHz) in order to study the performance of the Pyramid within a full closed loop adaptive optics system. This investigation involves tests on all fronts, from theoretical models and numerical simulations to experimental tests under controlled laboratory conditions, with an aim to fully understand the Pyramid sensor in both modulated and non-modulated configurations. We include results demonstrating the linearity of the Pyramid signals, compare measured interaction matrices with those derived in simulation and evaluate the performance in closed loop operation. The final goal is to provide an on sky comparison between the Pyramid and a Shack-Hartmann wave-front sensor, at Observatoire de la Côte d'Azur (ONERA-ODISSEE bench). Here we present the adaptive optics setup at LAM and latest experimental and modelling results. The loop is closed on different static wave-front errors: the initial shape of the deformable mirror (DM) and a turbulent-like shape projected onto the DM. The results demonstrate a Pyramid closed loop performance of 7–8nm rms wave-front error compared to a reference at surface.

Paper Details

Date Published: 27 July 2016
PDF: 13 pages
Proc. SPIE 9909, Adaptive Optics Systems V, 990964 (27 July 2016); doi: 10.1117/12.2232968
Show Author Affiliations
Charlotte Z. Bond, Aix Marseille Univ., CNRS, LAM (France)
Kacem El Hadi, Aix Marseille Univ., CNRS, LAM (France)
Jean-François Sauvage, Aix Marseille Univ., CNRS, LAM (France)
ONERA (France)
Carlos Correia, Aix Marseille Univ., CNRS, LAM (France)
Olivier Fauvarque, Aix Marseille Univ., CNRS, LAM (France)
Didier Rabaud, Innovation Network (France)
Masen Lamb, Univ. of Victoria (Canada)
Benoit Neichel, Aix Marseille Univ., CNRS, LAM (France)
Thierry Fusco, Aix Marseille Univ., CNRS, LAM (France)
ONERA (Finland)

Published in SPIE Proceedings Vol. 9909:
Adaptive Optics Systems V
Enrico Marchetti; Laird M. Close; Jean-Pierre Véran, Editor(s)

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