The Advanced Research Projects Agency (ARPA) - which came to be known as DARPA in 1972 when its name changed to the Defense Advanced Research Projects Agency - emerged in 1958 as part of a broad reaction to a singular event - the launching by the Soviet Union of the Sputnik satellite on Oct. 4,1957. DARPA's primary mission is to foster advanced technologies and systems that create "revolutionary" advantages for the U.S. military.