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

Jensen-Clem, Rebecca and Bond, Charlotte Z. and Cetre, Sylvain and McEwen, Eden and Wizinowich, Peter and Ragland, Sam and Mawet, Dimitri and Graham, James (2019) Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor. In: Techniques and Instrumentation for Detection of Exoplanets IX. Proceedings of SPIE. No.11117. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 111170W. ISBN 9781510629271.

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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).

Item Type:Book Section
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URLURL TypeDescription Paper
Jensen-Clem, Rebecca0000-0003-0054-2953
Wizinowich, Peter0000-0002-1646-442X
Mawet, Dimitri0000-0002-8895-4735
Additional Information:© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE). The predictive wavefront control demonstration is funded by the Heising-Simons Foundation. The authors would like to thank Marcos van Dam (Flat Wavefronts) for his suggestion to use the regularized least-squares inversion method to compute the predictive filter. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The near-infrared pyramid wavefront sensor is supported by the National Science Foundation under Grant No. AST-1611623. The PYWS camera was provided by Don Hall as part of his National Science Foundation funding under Grant No. AST 1106391. Support for R. J. -C. was provided by the Miller Institute for Basic Research in the Sciences. This work benefited from the NASA Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by the NASA Science Mission Directorate. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Group:Astronomy Department
Funding AgencyGrant Number
Heising-Simons FoundationUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Miller Institute for Basic Research in ScienceUNSPECIFIED
Subject Keywords:Exoplanets, Stars, Adaptive optics, Wavefronts, Turbulence, Coronagraphy, Point spread functions, Telescopes
Series Name:Proceedings of SPIE
Issue or Number:11117
Record Number:CaltechAUTHORS:20190912-140620297
Persistent URL:
Official Citation:Rebecca Jensen-Clem, Charlotte Z. Bond, Sylvain Cetre, Eden McEwen, Peter Wizinowich, Sam Ragland, Dimitri Mawet, and James Graham "Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor", Proc. SPIE 11117, Techniques and Instrumentation for Detection of Exoplanets IX, 111170W (9 September 2019);
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98619
Deposited By: Tony Diaz
Deposited On:12 Sep 2019 21:53
Last Modified:16 Nov 2021 17:40

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