A laser tracking and ranging system

An engineering model of a pulsed optical radar was developed for NASA to monitor continually the position of an astronaut on the lunar surface. The system tracks and measures range to a cooperative target (retroreflector) up to a distance of 700 m with a range accuracy of +/-1 m and an angular accuracy of +/-1 mrad. The system also directs a TV camera at the astronaut. An optical radar was used because it does not require the large complex antenna system and target reflector of conventional rf radars. The system design, which features GaAs injection laser, small retroreflector target, and silicon photodiode receiver, was directed toward providing a compact, rugged, lightweight system with high accuracy and low power consumption.