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Proceedings Paper

Ground layer sensing and compensation
Author(s): Andrei A. Tokovinin
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Paper 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.

Paper Details

Date Published: 7 July 2004
PDF: 10 pages
Proc. SPIE 5382, Second Backaskog Workshop on Extremely Large Telescopes, (7 July 2004); doi: 10.1117/12.566207
Show Author Affiliations
Andrei A. Tokovinin, Cerro Tololo Inter-American Observatory (Chile)

Published in SPIE Proceedings Vol. 5382:
Second Backaskog Workshop on Extremely Large Telescopes
Arne L. Ardeberg; Torben Andersen, Editor(s)

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