A Use for the Moon

The moon is proving useful as well as decorative. The Army Signal Corps announced last week that it is sending Teletype messages by ultrahigh frequency radio bounced off the moon. Transmitted from Benson, Ariz., the waves speed to the moon and reflect from its scratchy surface back to Encino, N. Mex., a total distance of 480,000 miles. Travel time: 2.6 sec. The message could have been received about as well at any place where the moon was visible.

It is no great trick to shoot radio waves at the moon and get a faint echo. The Signal Corps did it first in 1946, and even radio hams do it now. But dependable communication by lunar reflection is harder. The Signal Corps and its collaborator, Collins Radio Co. of Cedar Rapids, Iowa, use ultrashort waves (810 megacycles, 37 cm.) because they pass without much loss of energy through the ionized layers in the high atmosphere.

Moon's words to earth were militarily prosaic. Clattered the machine: "This is Teletype copy received at Encino, New Mexico on the 810-megacycle band, from Benson, Arizona, via the moon.''

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