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 60,000 km 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.
Read more about Pioneer 4: Spacecraft Design, Launching Vehicle, Mission
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“America is the civilization of people engaged in transforming themselves. In the past, the stars of the performance were the pioneer and the immigrant. Today, it is youth and the Black.”
—Harold Rosenberg (1906–1978)