Laser guide star

The properties of the design, including its ability to rely on Laser Guide Stars (LGS), have been extensively described in the literature and will not be recalled herein (Dierickx et al., 2000 Dierickx et al., 2000 Dierickx, 2001). 

Keywords lasers, laser guide star, adaptice optics, sum-frequency lasers, fiber lasers, Ra-... 

In order to overcome the requirement of having a bright "natural guide star" (NGS) near an astronomical source, a first generation of laser guide stars (LGS), or laser beacons, has been deployed to produce bright artificial stars from which wavefront distortions can be assessed. LGSs consist of the... 

Laser Guide Star Technologies and Experiments 4.1 Rayleigh Guide Star Lasers... 

Figure 14. Layout of the Lick Observatory laser guide star system.

A Systems Design Example The Keck Laser Guide Star. 

Figure 18. Layout of the pulsed dye laser guide star system at the Keck observatory.

Fiber laser guide star systems. It is now widely appreciated that the heat- dissipation characteristics of fibers, coupled with the high efficiencies demonstrated (> 80%) and excellent spatial mode characteristics, make fiber lasers a preferred candidate for many high power applications. Based on these features, fiber laser technologies would provide a compact, efficient, robust, turnkey laser source, ideally suited for LGS applications. 

Dainty, C., Ageorges, N., 2000, Laser Guide Star Adaptive Optics for Astronomy, NATO/ASl 551... 

Tyler, G.A., 1992, in Laser Guide Star Adaptive Optics Workshop Proceedings, Albuquerque, NM, 405... 

Abstract We explain the laser guide star concept and why we do need laser guide stars (LGS) to greatly enhance adaptive optics performances at large telescopes. Then we discuss the two physical limitations of LGS, which are the cone effect and the indetermination of the tilt of the incoming wavefront. Solutions to overcome them are explained. 

Keywords laser guide star, adaptive optics, lasers, cone effect, tilt... 

For all that, the laser guide star does not solve the sky coverage problem, unfortunately. Why Mainly for the three following reasons. 

Laser Guide Stars principle,cone effect and tilt measurement... 

A long path has been followed to overcome these two physical problems raised by the laser guide star, namely the cone effect and the tilt determination. And there is still a lot of work to be carried out before everything is solved. But I would say that the mathematics and the physics involved in the solutions we have today in hands are mastered, it is now clear that ... 

Ellerbroek, B. and Rigaut, R, 2001, Methods for correcting tilt anisoplanatism in laser-guide-star-based multi-conjugate adaptive optics Optics Com. 18 2539... 

Esposito, S., Ragazzoni, R., Riccardi, A., O Sullivan, C., Ageorges, N., Red-fern, M., and Davies, R., 2000, Absolute tilt from a laser guide star a first experiment, Exp. A., 10, 135... 

Koehler, B., 1998, VLT unit telescope suitability for intetferometry first results from acceptance tests on subsystems, SPIE 3350, 403 Le Louam, M., Eoy, R., Hubin, N., and Tallon, M., 1998, Laser guide star for 3.6m and 8m telescopes Performances and astrophysical implications, Mon. Not. R. Astron. Soc, 295, 756... 

Ragazzoni, R., Esposito, S., and Marchetti, E., 1995, Auxiliary telescopes for the absolute tip-tilt determination of a laser guide star, Mon. Not. R. Astron. Soc, 276, L76... 

Schock, M., Foy, R., Tallon, M., Noethe, L., and Pique, J.-R, 2002, Performance analysis of polychromatic laser guide stars used for wavefront tilt sensing, MNRAS 337, 910... 

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