Error breakdown of ELT-elongated LGS wavefront-sensing using CANARY on-sky measurements

Lisa Bardou; Eric Gendron; Gérard Rousset; Damien Gratadour; Alastair G. Basden; Domenico Bonaccini Calia; Tristan Buey; Mauro Centrone; Fanny Chemla; Jean-Luc Gach; Deli Geng; Zoltán Hubert; Douglas J. Laidlaw; Timothy J. Morris; Richard M. Myers; James Osborn; Andrew P. Reeves; Matthew J. Townson III; Fabrice Vidal

doi:10.1117/12.2313230

10 July 2018 Error breakdown of ELT-elongated LGS wavefront-sensing using CANARY on-sky measurements

Lisa Bardou, Eric Gendron, Gérard Rousset, Damien Gratadour, Alastair G. Basden, Domenico Bonaccini Calia, Tristan Buey, Mauro Centrone, Fanny Chemla, Jean-Luc Gach, Deli Geng, Zoltán Hubert, Douglas J. Laidlaw, Timothy J. Morris, Richard M. Myers, James Osborn, Andrew P. Reeves, Matthew J. Townson III, Fabrice Vidal

Author Affiliations +

Proceedings Volume 10703, Adaptive Optics Systems VI; 107031X (2018) https://doi.org/10.1117/12.2313230
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

Abstract

Six Laser Guide Stars (LGS) are included in the design of the European Extremely Large Telescope (ELT), with all of its current instruments taking advantage of them using Shack-Hartmann (SH) wavefront sensors (WFS). However, this implementation raises new issues related to the unprecedented elongation that results from the perspective effect combined to the thickness of the sodium layer. In order to investigate wavefront sensing with an elongated LGS on a SH WFS, we are taking advantage of the presence of the multi-object adaptive optics demonstrator CANARY on the William Herschel Telescope (WHT), in La Palma island, that was upgraded with a sodium LGS WFS for our experiment. The LGS is generated by ESO’s transportable Wendelstein LGS unit and the elongation is obtained by positioning the laser launch telescope 40 meters away from the WHT. With this experiment we are able to measure wavefronts using an elongated LGS WFS. In this paper, we present results obtained during the latest run of observations in September 2017. In these results is comprised an error breakdown of wavefront measurement on elongated LGS. The performances of several centroiding methods are compared thanks to this error breakdown. Additionally, we take advantage of varying observation conditions with respect to seeing and sodium profile to establish the robustness of the different centroiding methods. Finally, these performances are evaluated for different SH designs, to explore which compromises can be reached with respect to pixel scale and sub-aperture field of view.

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Lisa Bardou, Eric Gendron, Gérard Rousset, Damien Gratadour, Alastair G. Basden, Domenico Bonaccini Calia, Tristan Buey, Mauro Centrone, Fanny Chemla, Jean-Luc Gach, Deli Geng, Zoltán Hubert, Douglas J. Laidlaw, Timothy J. Morris, Richard M. Myers, James Osborn, Andrew P. Reeves, Matthew J. Townson III, and Fabrice Vidal "Error breakdown of ELT-elongated LGS wavefront-sensing using CANARY on-sky measurements", Proc. SPIE 10703, Adaptive Optics Systems VI, 107031X (10 July 2018); https://doi.org/10.1117/12.2313230

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