Optical radar using a corner reflector on the Moon

In a recent letter Hunt [1964] described a microwave transponder that can be landed on the moon and that can be used, in conjunction with a modified Glotrac station, to measure the distance between station and landing site. He also suggests several interesting measurements that could be made on the earth-moon system if the range accuracy were sufficiently well developed. The purpose of this letter is to point out the capabilities and possible advantages of an optical radar system which uses a corner reflector on the moon's surface. Smullin and Fiocco [1962] have demonstrated that laser beams can be scattered from the moon's surface and detected back at the earth; however, the return signals were too weak and too spread out (in time) to be used for precision ranging. Hoffman et al. [1960] have pointed out the advantages of using corner reflectors on an artificial satellite to permit precision tracking. More recently, Plotkin [1964] has described an optical radar system that is capable of making precision range measurements to satellites which have been equipped with corner reflectors.