Analysis of on-sky MOAO performance of CANARY using natural guide stars

¹ LESIA, Observatoire de Paris – CNRS – UPMC – Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
e-mail: fabrice.vidal@obspm.fr
² Centre for Advanced Instrumentation, Durham University, South Road, Durham DH1 3LE, UK
³ GEPI, Observatoire de Paris – CNRS – Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
⁴ UKATC, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK

Received: 6 November 2013
Accepted: 5 June 2014

Abstract

The first on-sky results obtained by CANARY, the multi-object adaptive optics (MOAO) demonstrator, are analysed. The data were recorded at the William Herschel Telescope, at the end of September 2010. We describe the command and calibrations algorithms used during the run and present the observing conditions. The processed data are MOAO-loop engaged or disengaged slopes buffers, comprising the synchronised measurements of the four natural guide stars (NGS) wavefront sensors running in parallel, and near infrared (IR) images. We describe the method we use to establish the error budget of CANARY. We are able to evaluate the tomographic and the open loop errors, having median values around 216 nm and 110 nm respectively. In addition, we identify an unexpected residual quasi-static field aberration term of mean value 110 nm. We present the detailed error budget analysed for three sets of data for three different asterisms. We compare the experimental budgets with the numerically simulated ones and demonstrate a good agreement. We find also a good agreement between the computed error budget from the slope buffers and the measured Strehl ratio on the IR images, ranging between 10% and 20% at 1530 nm. These results make us confident in our ability to establish the error budget of future MOAO instruments.