 Working closely together, ABMA and JPL completed the job of modifying the Jupiter-C and building Explorer 1 in 84 days.However, before work was completed, the Soviet Union launched a second satellite, Sputnik 2, on November 3, 1957.The U.S. Navy's attempt to put the first U.S. satellite into orbit failed with the launch of the Vanguard TV3 on December 6, 1957.