Optimizing Rayleigh laser guide star range-gate depth during initial loop closing

The use of a Rayleigh laser guide star (LGS) as a wavefront reference for adaptive optics (AO) allows complete control over the distance to, and depth of, the slice of the Rayleigh plume that is selected. By altering the LGS range-gate depth (RGD) and distance at three defined stages during closed-loop operations, the LGS performance can be optimized. For the given example of a 20 km LGS on a 4.2 m telescope the application of this technique would increase the permissible RGD from 200to930 m after optimization. This can allow either an increase in LGS altitude or an increase in wavefront sensor frame rate, thereby increasing AO system performance.