The launch was supposed to wait until 6 October 1957, the first day of the International Geophysical Year. Soviet planners moved it up by 48 hours, for political reasons — the R-7 lifted off from the Baikonur Cosmodrome at 19:28:34 UTC on 4 October 1957, placing the 83.6 kg sphere in a 215 × 939 km orbit; the TASS announcement came 14 hours and 24 minutes later, on the morning of 5 October.
The launch was originally scheduled for October 6, the first day of the International Geophysical Year, but was moved up by 48 hours for political reasons; the Soviet leadership wanted the launch before Khrushchev’s visit to a meeting in Yugoslavia. The 92-day gap before the United States launched Explorer 1 on January 31, 1958, was not for lack of effort. The U.S. Navy’s Vanguard program, the publicly designated American satellite effort, failed on national television on December 6, 1957. Explorer 1 was a derivative of von Braun’s Jupiter-C, which had been authorized as a backup on November 8, 1957, two days after the failed Vanguard test.
The political response in Washington was immediate. By February 1958, ARPA had been created (February 7), the National Defense Education Act was in draft, NASA Act had been submitted to Congress (April). The institutional reform was underway before Explorer 1 reached orbit.
For the rest of our account of the space race and the Sputnik article.