Optics: Lasers to the Moon

The pictures taken by Surveyor 7's camera on the moon last week appeared to show only a crescent-shaped earth glowing in the lunar sky. But closer inspection showed two seemingly insignificant starlike dots of light on the night portion of the earth. They were historic dots. Each represented the light from an argon-ion laser beam aimed from Tucson, Ariz., and Wrightwood, Calif., at Surveyor's location near the lunar crater Tycho, some 240,000 miles away.

In an engineering test that was a preliminary to actual laser experiments during the Apollo moon mission, a group headed by University of Maryland Physicists Carroll...

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