Pioneer 4 cover

Pioneer 4 was launched March 3, 1959, and successfully passed within 60,000 kilometers (37,300 miles) of the Moon the following day. The satellite was tracked for 82 hours to a distance of 655,000 kilometers (407,000 miles) from Earth, a record at that time. Pioneer 4 is now orbiting the Sun, the first U.S. spacecraft placed in solar orbit.