On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

• Published in: Monthly notices of the Royal Astronomical Society 2017-05, Vol.466 (4), p.stx062-5010
• Main Authors: Basden, A. G., Bardou, L., Calia, D. Bonaccini, Buey, T., Centrone, M., Chemla, F., Gach, J. L., Gendron, E., Gratadour, D., Guidolin, I., Jenkins, D. R., Marchetti, E., Morris, T. J., Myers, R. M., Osborn, J., Reeves, A. P., Reyes, M., Rousset, G., Stangalini, M., Townson, M. J., Vidal, F.
• Format: Article
• Language: English
• Subjects: Astrophysics; Sciences of the Universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stx062

The performance of adaptive optics systems is partially dependent on the algorithms used within the real‐time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack‐Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40 m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on‐sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on‐sky H‐band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on‐sky demonstration.