Though never used in combat, it was used as the expendable launch system for the Mariner space probes used to study Mercury, Venus, and Mars (1962-1973); and to launch all but the first two Mercury program missions (1962-1963). The Mercury missions resulted in the first American to orbit the earth (Lt. Col. John H. Glenn Jr.) in February of 1962. (Major Yuri A. Gagarin, a Soviet cosmonaut was the first human in orbit, in April of 1961.)
The Atlas had been suggested for use, by the United States Air Force, in what became known as Project Vanguard.
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