"University of Maryland physics professor Carroll Alley was the project's principal investigator during the Apollo years, and he follows its progress today. "Using these mirrors," explains Alley, "we can 'ping' the moon with laser pulses and measure the Earth-moon distance very precisely. This is a wonderful way to learn about the moon's orbit and to test theories of gravity.""

My teacher in Quantum Physics ( 74-78). He also developed the adjustments top the atomic clocks for GPS.