Tags: Artificialsatellite, Satellite.
Pioneer 4 was a spin-stabilized spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first U.S. probe to escape from the Earth’s gravity. 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 60000 km of the Moon’s surface. However Pioneer 4 did not come close enough to trigger its photoelectric sensor.
