Ground layer sensing and compensation

Andrei A. Tokovinin

doi:10.1117/12.566207

7 July 2004 Ground layer sensing and compensation

Andrei A. Tokovinin

Proceedings Volume 5382, Second Backaskog Workshop on Extremely Large Telescopes; (2004) https://doi.org/10.1117/12.566207
Event: Second Backaskog Workshop on Extremely Large Telescopes, 2003, Backaskog, Sweden

Abstract

A simple analytical method to compute the point spread function for ground-layer compensation at large telescopes is developed. It is shown that a particular form of spatial filtering of high-altitude turbulence achieves very good PSF uniformity and symmetry over a given field. Wave-front sensing with a single low-altitude Rayleigh LGS can reach performance close to optimum at telescopes of medium aperture. Using 4234 real turbulence profiles measured on 21 nights at Cerro Pachon realistic statistics of ground-layer compensation are computed for the first time. The median FWHM resolution of an AO system with a Rayleigh beacon at 10 km and actuator pitch 0.4 m at 4.2 m telescope is 0."53, 0."31, and 0."22 at 0.5, 0.7, and 1.0 μm wavelength respectively. The median increase of the bightness in the center of stellar image over uncompensated seeing is 1.2, 1.7, and 2.4 magnitudes at those wavelengths.

Citation Download Citation

Andrei A. Tokovinin "Ground layer sensing and compensation", Proc. SPIE 5382, Second Backaskog Workshop on Extremely Large Telescopes, (7 July 2004); https://doi.org/10.1117/12.566207

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