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Context. The wind driven halo is a feature observed within the imagesdelivered by the latest generation of ground-based instruments equipped with anextreme adaptive optics system and a coronagraphic device, such as SPHERE atthe VLT. This signature appears when the atmospheric turbulence conditions arevarying faster than the adaptive optics loop can correct. The wind driven haloshows as a radial extension of the point spread function along a distinctdirection (sometimes referred to as the butterfly pattern). When present, itsignificantly limits the contrast capabilities of the instrument and preventsthe extraction of signals at close separation or extended signals such ascircumstellar disks. This limitation is consequential because it contaminatesthe data a substantial fraction of the time: about 30% of the data produced bythe VLT/SPHERE instrument are affected by the wind driven halo.Aims. This paperreviews the causes of the wind driven halo and presents a method to analyze itscontribution directly from the scientific images. Its effect on the rawcontrast and on the final contrast after post-processing isdemonstrated.Methods. We used simulations and on-sky SPHERE data to verify thatthe parameters extracted with our method are capable of describing the winddriven halo present in the images. We studied the temporal, spatial andspectral variation of these parameters to point out its deleterious effect onthe final contrast.Results. The data driven analysis we propose does provideinformation to accurately describe the wind driven halo contribution in theimages. This analysis justifies why this is a fundamental limitation to thefinal contrast performance reached.Conclusions. With the established procedure,we will analyze a large sample of data delivered by SPHERE in order to propose,in the future, post-processing techniques tailored to remove the wind drivenhalo.

The wind-driven halo in high-contrast images I: analysis from the focal plane images of SPHERE