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Speckle lifetime in XAO coronagraphic images: temporal evolution of SPHERE coronagraphic images

Milli, J. and Banas, T. and Mouillet, D. and Mawet, D. and Girard, J. H. and Vigan, A. and Boccaletti, A. and Kasper, M. and Wahhaj, Zahed and Lagrange, A. M. and Beuzit, J.-L. and Fusco, T. and Sauvage, J.-F. and Galicher, R. (2016) Speckle lifetime in XAO coronagraphic images: temporal evolution of SPHERE coronagraphic images. In: Adaptive Optics Systems V. Proceedings of SPIE. No.9909. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 99094Z. ISBN 978-1-5106-0198-7.

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The major source of noise in high-contrast imaging is the presence of slowly evolving speckles that do not average with time. The temporal stability of the point-spread-function (PSF) is therefore critical to reach a high contrast with extreme adaptive optics (XAO) instruments. Understanding on which timescales the PSF evolves and what are the critical parameters driving the speckle variability allow to design an optimal observing strategy and data reduction technique to calibrate instrumental aberrations and reveal faint astrophysical sources. We have obtained a series of 52 min, AO-corrected, coronagraphically occulted, high-cadence (1.6Hz), H-band images of the star HR 3484 with the SPHERE (Spectro-Polarimeter High-contrast Exoplanet REsearch1) instrument on the VLT. This is a unique data set from an XAO instrument to study its stability on timescales as short as one second and as long as several tens of minutes. We find different temporal regimes of decorrelation. We show that residuals from the atmospheric turbulence induce a fast, partial decorrelation of the PSF over a few seconds, before a transition to a regime with a linear decorrelation with time, at a rate of several tens parts per million per second (ppm/s). We analyze the spatial dependence of this decorrelation within the well-corrected radius of the adaptive optics system and show that the linear decorrelation is faster at short separations. Last, we investigate the influence of the distance to the meridian on the decorrelation.

Item Type:Book Section
Related URLs:
URLURL TypeDescription Paper
Milli, J.0000-0001-9325-2511
Mawet, D.0000-0002-8895-4735
Girard, J. H.0000-0001-8627-0404
Vigan, A.0000-0002-5902-7828
Boccaletti, A.0000-0001-9353-2724
Wahhaj, Zahed0000-0001-8269-324X
Additional Information:© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). J.M. acknowledges support from the ESO fellowship program and we thank ESO staff and technical operators at the Paranal Observatory. T.B. acknowledges the Adaptive Optics groups at ESO Santiago and ESO Garching for support of this research.
Funding AgencyGrant Number
European Southern Observatory (ESO)UNSPECIFIED
Subject Keywords:Extreme Adaptive Optics, Speckles, High Contrast
Series Name:Proceedings of SPIE
Issue or Number:9909
Record Number:CaltechAUTHORS:20161202-145424511
Persistent URL:
Official Citation:J. Milli ; T. Banas ; D. Mouillet ; D. Mawet ; J. H. Girard ; A. Vigan ; A. Boccaletti ; M. Kasper ; Zahed Wahhaj ; A. M. Lagrange ; J.-L. Beuzit ; T. Fusco ; J.-F. Sauvage ; R. Galicher; Speckle lifetime in XAO coronagraphic images: temporal evolution of SPHERE coronagraphic images. Proc. SPIE 9909, Adaptive Optics Systems V, 99094Z (July 27, 2016); doi:10.1117/12.2231703.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72537
Deposited On:06 Dec 2016 19:54
Last Modified:11 Nov 2021 05:03

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