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Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes

Laidlaw, Douglas J; Osborn, James; Morris, Timothy J; Basden, Alastair G; Beltramo-Martin, Olivier; Butterley, Timothy; Gendron, Eric; Reeves, Andrew P; Rousset, Gerard; Townson, Matthew J; Wilson, Richard W

Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes Thumbnail


Authors

Douglas J Laidlaw

Olivier Beltramo-Martin

Eric Gendron

Andrew P Reeves

Gerard Rousset



Abstract

Advanced adaptive optics (AO) instruments on ground-based telescopes require accurate knowledge of the atmospheric turbulence strength as a function of altitude. This information assists point spread function reconstruction, AO temporal control techniques and is required by wide-field AO systems to optimize the reconstruction of an observed wavefront. The variability of the atmosphere makes it important to have a measure of the optical turbulence profile in real time. This measurement can be performed by fitting an analytically generated covariance matrix to the cross-covariance of Shack–Hartmann wavefront sensor (SHWFS) centroids. In this study we explore the benefits of reducing cross-covariance data points to a covariance map region of interest (ROI). A technique for using the covariance map ROI to measure and compensate for SHWFS misalignments is also introduced. We compare the accuracy of covariance matrix and map ROI optical turbulence profiling using both simulated and on-sky data from CANARY, an AO demonstrator on the 4.2 m William Herschel telescope, La Palma. On-sky CANARY results are compared to contemporaneous profiles from Stereo-SCIDAR – a dedicated high-resolution optical turbulence profiler. It is shown that the covariance map ROI optimizes the accuracy of AO telemetry optical turbulence profiling. In addition, we show that the covariance map ROI reduces the fitting time for an extremely large telescope-scale system by a factor of 72. The software package we developed to collect all of the presented results is now open source.

Citation

Laidlaw, D. J., Osborn, J., Morris, T. J., Basden, A. G., Beltramo-Martin, O., Butterley, T., …Wilson, R. W. (2018). Optimizing the accuracy and efficiency of optical turbulence profiling using adaptive optics telemetry for extremely large telescopes. Monthly Notices of the Royal Astronomical Society, 483(4), 4341-4353. https://doi.org/10.1093/mnras/sty3285

Journal Article Type Article
Acceptance Date Nov 27, 2018
Online Publication Date Dec 3, 2018
Publication Date Dec 3, 2018
Deposit Date Jan 17, 2019
Publicly Available Date Jan 24, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 483
Issue 4
Pages 4341-4353
DOI https://doi.org/10.1093/mnras/sty3285

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Copyright Statement
© 2018 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.





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