Characterization of lemniscate atmospheric aberrations in Gemini Planet Imager data

Madurowicz, Alexander; Macintosh, Bruce; Ruffio, Jean-Baptiste; Chilcote, J.; Bailey, Vanessa P.; Poyneer, Lisa; Nielsen, Eric L.; Norton, Andrew

doi:10.1117/12.2314267

Cited by 14 publications

(16 citation statements)

References 11 publications

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“…In addition, by comparing the contribution from the ground layer and the contribution from the jet stream layer for each individual profile, we observe that for about 80% of the profiles, the jet stream layer has a higher contribution to v eff . By correlating the observed WDH direction within high-contrast images from GPI, Madurowicz et al (2018) also showed that the jet stream layer is indeed mainly responsible for the appearance of the WDH in HCI data.…”

Section: Temporal Variation In Atmospheric Turbulencementioning

confidence: 83%

Wind-driven halo in high-contrast images

Cantalloube

Farley

Milli

et al. 2020

A&A

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Context. The wind-driven halo is a feature that is observed in images that were delivered by the latest generation of ground-based instruments that are equipped with an extreme adaptive optics system and a coronagraphic device, such as SPHERE at the Very Large Telescope (VLT). This signature appears when the atmospheric turbulence conditions vary faster than the adaptive optics loop can correct for. The wind-driven halo is observed as a radial extension of the point spread function along a distinct direction (this is sometimes referred to as the butterfly pattern). When this is present, it significantly limits the contrast capabilities of the instrument and prevents the extraction of signals at close separation or extended signals such as circumstellar disks. This limitation is consequential because it contaminates the data for a substantial fraction of the time: about 30% of the data produced by the VLT/SPHERE instrument are affected by the wind-driven halo. Aims. This paper reviews the causes of the wind-driven halo and presents a method for analyzing its contribution directly from the scientific images. Its effect on the raw contrast and on the final contrast after post-processing is demonstrated. Methods. We used simulations and on-sky SPHERE data to verify that the parameters extracted with our method can describe the wind-driven halo in the images. We studied the temporal, spatial, and spectral variation of these parameters to point out its deleterious effect on the final contrast. Results. The data-driven analysis we propose provides information to accurately describe the wind-driven halo contribution in the images. This analysis confirms that this is a fundamental limitation of the finally reached contrast performance. Conclusions. With the established procedure, we will analyze a large sample of data delivered by SPHERE in order to propose post-processing techniques that are tailored to removing the wind-driven halo.

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Section: Temporal Variation In Atmospheric Turbulencementioning

confidence: 83%

Wind-driven halo in high-contrast images

Cantalloube

Farley

Milli

et al. 2020

A&A

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“…Such time lags are disastrous for exoplanet imaging because they often cause light leakage into the regions closest to the star where planets are most likely to be found (e.g. the "wind butterfly" effect 3,4 ). Predictive WFC is any approach that seeks to compensate for these time lags by predicting the shape of the wavefront one or more time lags into the future based on past wavefront measurements.…”

Section: Introductionmentioning

confidence: 99%

Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor

Jensen-Clem

Bond

Cetre

et al. 2019

Techniques and Instrumentation for Detection of Exoplanets IX

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The success of ground-based instruments for high contrast exoplanet imaging depends on the degree to which adaptive optics (AO) systems can mitigate atmospheric turbulence. While modern AO systems typically suffer from millisecond time lags between wavefront measurement and control, predictive wavefront control (pWFC) is a means of compensating for those time lags using previous wavefront measurements, thereby improving the raw contrast in the post-coronagraphic science focal plane. A method of predictive control based on Empirical Orthogonal Functions (EOF) has previously been proposed and demonstrated on Subaru/SCExAO. In this paper we present initial tests of this method for application to the near-infrared pyramid wavefront sensor (PYWFS) recently installed in the Keck II AO system. We demonstrate the expected root-mean-square (RMS) wavefront error and contrast benefits of pWFC based on simulations, applying pWFC to on-sky telemetry data saved during commissioning of the PYWFS. We discuss how the performance varies as different temporal and spatial scales are included in the computation of the predictive filter. We further describe the implementation of EOF pWFC within the PYWFS dedicated real-time controller (RTC), and, via daytime testing at the observatory, we demonstrate the performance of pWFC in real time when pre-computed phase screens are applied to the deformable mirror (DM).

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“…This implies different observatory sites with slower winds may have a comparative advantage, as well as the merits in scheduling observations around poor atmospheric conditions. In our previous work [17], we demonstrate that the jet stream is highly correlated with these errors, in a very large sample of observations.…”

Section: Discussionmentioning

confidence: 60%

Asymmetries in adaptive optics point spread functions

Madurowicz

Macintosh

Chilcote

et al. 2019

J. Astron. Telesc. Instrum. Syst.

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An explanation for the origin of asymmetry along the preferential axis of the PSF of an AO system is developed. When phase errors from high altitude turbulence scintillate due to Fresnel propagation, wavefront amplitude errors may be spatially offset from residual phase errors. These correlated errors appear as asymmetry in the image plane under the Fraunhofer condition. In an analytic model with an open-loop AO system, the strength of the asymmetry is calculated for a single mode of phase aberration, which generalizes to two dimensions under a Fourier decomposition of the complex illumination. Other parameters included are the spatial offset of the AO correction, which is the wind velocity in the frozen flow regime multiplied by the effective AO time delay, and propagation distance or altitude of the turbulent layer. In this model, the asymmetry is strongest when the wind is slow and nearest to the coronagraphic mask when the turbulent layer is far away, such as when the telescope is pointing low towards the horizon. A great emphasis is made about the fact that the brighter asymmetric lobe of the PSF points in the opposite direction as the wind, which is consistent analytically with the clarification that the image plane electric field distribution is actually the inverse Fourier transform of the aperture plane. Validation of this understanding is made with observations taken from the Gemini Planet Imager, as well as being reproducible in end-to-end AO simulations.

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Characterization of lemniscate atmospheric aberrations in Gemini Planet Imager data

Cited by 14 publications

References 11 publications

Wind-driven halo in high-contrast images

Wind-driven halo in high-contrast images

Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor

Asymmetries in adaptive optics point spread functions

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