High precision lunar tracking for laser ranging

Laser ranging to lunar surface retroreflectors has provided a valuable source of data for the investigation of the lunar orbit, the earth's orientation in space, general relativity, and many other aspects of solar system dynamics. Due to the moon's relatively large distance, and the requirement to keep the beam from the relatively low-power laser very narrow, acquiring this data type requires very accurate telescope pointing and tracking capabilities. The nominal requirement is to keep the telescope on target within approximately 1 arcsec of its predicted location for at least several minutes. An expansion of this requirement and the methods used to accomplish this high precision pointing are presented. Difficulties encountered and a few future goals of automating the McDonald station are also discussed.