When the news broke on Oct. 4, 1957, that the Soviet Union had sent the world’s first man-made satellite into space, the American public was shocked. The C.I.A., it now appears, much less so.

This week, the agency declassified 59 memos, reports and summaries to mark the 60th anniversary of the day the Soviet satellite Sputnik 1 went into orbit.

The documents — which include information about Soviet missile capabilities and several Sputnik satellites — suggest that in the years leading up to the first Sputnik’s success, United States intelligence agents and government officials were growing more and more certain that a launch was imminent.

“U.S. intelligence, the military and the administration of President Dwight D. Eisenhower not only were fully informed of Soviet planning to launch an earth satellite but also knew a Soviet satellite would probably achieve orbit no later than the end of 1957,” the C.I.A. said in a report released on Wednesday.