A solution to the problem of detecting the tip-tilt modes in multiconjugate adaptive optics (MCAO) with laser guide stars (LGS) is presented. This solution requires the presence of only a single relatively dim natural guide star (NGS) within the reconstructed field of view (FoV). The dim NGS is used for the reconstruction of the tip-tilt modes on the entire FoV, while the tomographic reconstruction of second-order and higher-order modes is made possible by having an LGS constellation with LGSs at different heights. Due to the relatively low brightness required for the tip-tilt NGS and the large corrected FoV (as compared with the case of conventional adaptive optics) the presented solution provides a means to achieve near-diffraction-limited performance of a 10-m-class telescope in the near infrared over a large portion of the sky. Sky coverage calculations assuming median seeing conditions indicate that this technique could be applied to 75% (95%) of the sky, achieving corrections with an average Strehl ratio ∼0.42(∼0.33) in the 2.2 µm K band across the 1.5′ reconstructed FoV.
© 2005 Optical Society of America
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
(010.7060) Atmospheric and oceanic optics : Turbulence
(010.7350) Atmospheric and oceanic optics : Wave-front sensing
Bruno Femenía, "Tip-tilt reconstruction with a single dim natural guide star in multiconjugate adaptive optics with laser guide stars," J. Opt. Soc. Am. A 22, 2719-2729 (2005)