"Missile Gap": refers to the perceived Soviet superiority in ICBMs due to exaggerated estimates by the Gaither Committee in 1957 and USAF in the early 1960's.

The words "missile gap" and "intelligence gap" were in the news. Had the US lost its strategic weapons edge over the Soviets? Clearly, the US had to learn what the Soviets were doing. The U-2 planes were no longer safe sources of intelligence: they could be shot down. The US needed to peek safely through a keyhole, at an area that crosses eleven time zones, and see what they were up to. Could the faltering US space program safely launch a spy satellite, look through that keyhole, and retrieve the results? It was the most important challenge yet to US national security.

For additional information click here.