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Proceedings Paper

Tackling down the low wind effect on SPHERE instrument
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Paper Abstract

SPHERE is the VLT second generation planet hunter instrument. Installed since May 2014 on UT3, the system has been commissioned and verified for more than one year now and routinely delivers unprecedented images of star surroundings, exoplanets and dust disks. The exceptional performance required for this kind of observation makes the appointment: a repeatable Strehl Ratio of 90% in H band, a rough contrast level of 10-5@0.5 arcsec, and reaches 10-6 at the same separation after differential imaging (SDI, ADI). The instrument also presents high contrast levels in the visible and an unprecedented 17mas diffraction-limited resolution at 0.65 microns wavelength. SAXO is the SPHERE XAO system, allowing the system to reach its final detectivity. Its high performance and therefore highly sensitive capacities turns a new eye on telescope environment. Even if XAO performance are reached as expected, some unexpected limitations are here described and a first work around is proposed and discussed. Spatial limitation: wave-front aberrations have been identified, deviating from kolmogorov statistics, and therefore not easily seen and compensated for by the XAO system. The impact of this limitations results in a degraded performance in some particular low wind conditions. Solutions are developed and tested on sky to propose a new operation procedure reducing this limitation. Temporal limitation: high amplitude vibrations on the low order modes have been issued, due to telescope environment and XAO behaviour. Again, a solution is developed and an assessment of its performance is dressed. The potential application of these solutions to E-ELT is proposed.

Paper Details

Date Published: 26 July 2016
PDF: 9 pages
Proc. SPIE 9909, Adaptive Optics Systems V, 990916 (26 July 2016); doi: 10.1117/12.2232459
Show Author Affiliations
Jean-François Sauvage, ONERA (France)
Aix Marseille Univ., CRNS, LAM (France)
Thierry Fusco, ONERA (France)
Aix Marseille Univ., CNRS, LAM (France)
Masen Lamb, Univ. of Victoria (Canada)
NRC Herzberg Astronomy (Canada)
Julien Girard, European Southern Observatory (Germany)
Martin Brinkmann, European Southern Observatory (Germany)
Andres Guesalaga, Pontificia Univ. Católica de Chile (Chile)
Aix Marseille Univ., CNRS, LAM (France)
Fondation IMéRA (France)
Peter Wizinowich, W. M. Keck Observatory (United States)
Jared O'Neal, European Southern Observatory (Germany)
Mamadou N'Diaye, Space Telescope Science Institute (United States)
Arthur Vigan, Aix Marseille Univ., CNRS, LAM (France)
European Southern Observatory (Germany)
David Mouillet, IPAG, UJF-Grenoble 1, CNRS-INSU (France)
Jean-Luc Beuzit, IPAG, UJF-Grenoble 1, CNRS-INSU (France)
Markus Kasper, European Southern Observatory (Germany)
Miska Le Louarn, European Southern Observatory (Germany)
Julien Milli, European Southern Observatory (Germany)
Kjetil Dohlen, Aix Marseille Univ., CNRS, LAM (France)
Benoît Neichel, Aix Marseille Univ., CNRS, LAM (France)
Pierre Bourget, European Southern Observatory (Germany)
Pierre Haguenauer, European Southern Observatory (Germany)
Dimitri Mawet, Jet Propulsion Lab. (United States)


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

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