OSA Centennial Snapshots: Lasers, Lunar Missions and Legacies

Combined observations of the moon and Earth from two NASA missions. [NASA]

In the 1960s, during the height of the Cold War and the space race, power-electronics technician Hildreth “Hal” Walker Jr. was selected to become KORAD Laser System’s field operations manager for the U.S. Apollo 11 Lunar Laser-Ranging Experiment (LURE). On 20 July 1969, Apollo 11 astronauts Edwin “Buzz” Aldrin Jr. and Neil Armstrong placed a 10 × 10 array of corner-cube retroreflectors on the surface of the moon. With the array in place, the race was on between teams from the United States and the uninvited Soviet Union—each firing weapons-grade ruby lasers at the same reflectors—to hit that target and detect a return signal, and become the first nation to measure the distance to the moon with a pulse of laser photons.