PIONEER 4

Pioneer 4 is an American spin-stabilized uncrewed spacecraft that was launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first probe of the United States to escape from the Earth's gravity. Launched on March 3, 1959, it carried a payload similar to Pioneer 3: a lunar radiation environment experiment using a Geiger–Müller tube detector and a lunar photography experiment. It passed within 58,983 km (36,650 mi) of the Moon's surface. However, Pioneer 4 did not come close enough to trigger its photoelectric sensor. The spacecraft was still in solar orbit as of 1969. It was the only successful lunar probe launched by the U.S. in 12 attempts between 1958 and 1963; only in 1964 would Ranger 7 surpass its success by accomplishing all of its mission objectives.