Free access article

A&A 400, 1199-1207 (2003)
DOI: 10.1051/0004-6361:20030022

Tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics

Reconstruction of the long exposure point spread function from control loop data

R. C. Flicker^{1, 2}, F. J. Rigaut² and B. L. Ellerbroek<sup>2

1</sup>  Lund Observatory, Box 43, 22100 Lund, Sweden
²  Gemini Observatory, 670 N. A'Ohoku Pl., Hilo HI-96720, USA

(Received 22 August 2002 / Accepted 6 January 2003 )

Abstract
A method is presented for estimating the long exposure point spread function (PSF) degradation due to tilt anisoplanatism in a laser-guide-star-based multiconjugate adaptive optics systems from control loop data. The algorithm is tested in numerical Monte Carlo simulations of the separately driven low-order null-mode system, and is shown to be robust and accurate with less than 10% relative error in both  H and K bands down to a natural guide star (NGS) magnitude of m_R=21, for a symmetric asterism with three NGS on a 30 arcsec radius. The H band limiting magnitude of the null-mode system due to NGS signal-to-noise ratio and servo-lag was estimated previously to m_R=19. At this magnitude, the relative errors in the reconstructed PSF and Strehl are here found to be less than 5% and 1%, suggesting that the PSF retrieval algorithm will be applicable and reliable for the full range of operating conditions of the null-mode system.

Key words: Instrumentation -- adaptive optics -- methods -- statistical

Offprint request: R. C. Flicker, ralf@astro.lu.se

© ESO 2003

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