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Applied Optics

Applied Optics


  • Editor: Joseph N. Mait
  • Vol. 50, Iss. 4 — Feb. 1, 2011
  • pp: 473–483

Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes

Richard M. Clare, Miska Le Louarn, and Clementine Béchet  »View Author Affiliations

Applied Optics, Vol. 50, Issue 4, pp. 473-483 (2011)

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We propose ground-layer adaptive optics (GLAO) to improve the seeing on the 42 m European Extremely Large Telescope. Shack–Hartmann wavefront sensors (WFSs) with laser guide stars (LGSs) will experience significant spot elongation due to off-axis observation. This spot elongation influences the design of the laser launch location, laser power, WFS detector, and centroiding algorithm for LGS GLAO on an extremely large telescope. We show, using end-to-end numerical simulations, that with a noise-weighted matrix-vector-multiply reconstructor, the performance in terms of 50% ensquared energy (EE) of the side and central launch of the lasers is equivalent, the matched filter and weighted center of gravity centroiding algorithms are the most promising, and approximately 10 × 10 undersampled pixels are optimal. Significant improvement in the 50% EE can be observed with a few tens of photons/subaperture/frame, and no significant gain is seen by adding more than 200 photons/subaperture/frame. The LGS GLAO is not particularly sensitive to the sodium profile present in the mesosphere nor to a short-timescale (less than 100 s ) evolution of the sodium profile. The performance of LGS GLAO is, however, sensitive to the atmospheric turbulence profile.

© 2011 Optical Society of America

OCIS Codes
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(010.7350) Atmospheric and oceanic optics : Wave-front sensing

ToC Category:
Atmospheric and Oceanic Optics

Original Manuscript: August 31, 2010
Revised Manuscript: November 26, 2010
Manuscript Accepted: November 28, 2010
Published: January 27, 2011

Richard M. Clare, Miska Le Louarn, and Clementine Béchet, "Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes," Appl. Opt. 50, 473-483 (2011)

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