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Paper Abstract

The SPHERE (spectro-photometric exoplanet research) extreme-AO planet hunter saw first light at the VLT observatory on Mount Paranal in May 2014 after ten years of development. Great efforts were put into modelling its performance, particularly in terms of achievable contrast, and to budgeting instrumental features such as wave front errors and optical transmission to each of the instrument’s three focal planes, the near infrared dual imaging camera IRDIS, the near infrared integral field spectrograph IFS and the visible polarimetric camera ZIMPOL. In this paper we aim at comparing predicted performance with measured performance. In addition to comparing on-sky contrast curves and calibrated transmission measurements, we also compare the PSD-based wave front error budget with in-situ wave front maps obtained thanks to a Zernike phase mask, ZELDA, implemented in the infrared coronagraph wheel. One of the most critical elements of the SPHERE system is its high-order deformable mirror, a prototype 40x40 actuator piezo stack design developed in parallel with the instrument itself. The development was a success, as witnessed by the instrument performance, in spite of some bad surprises discovered on the way. The devastating effects of operating without taking properly into account the loss of several actuators and the thermally and temporally induced variations in the DM shape will be analysed, and the actions taken to mitigate these defects through the introduction of specially designed Lyot stops and activation of one of the mirrors in the optical train will be described.

Paper Details

Date Published: 9 August 2016
PDF: 11 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99083D (9 August 2016); doi: 10.1117/12.2233953
Show Author Affiliations
Kjetil Dohlen, Lab. d'Astrophysique de Marseille (France)
Arthur Vigan, Lab. d'Astrophysique de Marseille (France)
David Mouillet, Institut de Planétologie et d’Astrophysique de Grenoble (France)
François Wildi, Observatoire de Genève (Switzerland)
Jean-François Sauvage, Lab. d'Astrophysique de Marseille (France)
ONERA (France)
Thierry Fusco, Lab. d'Astrophysique de Marseille (France)
ONERA (France)
Jean-Luc Beuzit, Institut de Planétologie et d’Astrophysique de Grenoble (France)
Pascal Puget, Institut de Planétologie et d’Astrophysique de Grenoble (France)
David Le Mignant, Lab. d'Astrophysique de Marseille (France)
Ronald Roelfsema, ASTRON (Netherlands)
Johan Pragt, ASTRON (Netherlands)
Hans Martin Schmid, ETH Zürich (Switzerland)
Raffaele Gratton, INAF - Osservatorio Astronomico di Padova (Italy)
Dino Mesa, INAF - Osservatorio Astronomico di Padova (Italy)
Riccardo Claudi, INAF - Osservatorio Astronomico di Padova (Italy)
Maud Langlois, Ctr. de Recherche Astrophysique de Lyon, Univ. Lyon, Univ. Lyon 1, CNRS (France)
Anne Costille, Lab. d'Astrophysique de Marseille (France)
Emmanuel Hugot, Lab. d'Astrophysique de Marseille (France)
Jared O'Neil, European Southern Observatory (Chile)
Juan Carlos Guerra, European Southern Observatory (Chile)
Mamadou N'Diaye, Space Telescope Science Institute (United States)
Julien Girard, European Southern Observatory (Chile)
Dimitri Mawet, California Institute of Technology (United States)
Gerard Zins, European Southern Observatory (Chile)

Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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