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
Famous quotes containing the word pioneer:
“Mead had studied for the ministry, but had lost his faith and took great delight in blasphemy. Capt. Charles H. Frady, pioneer missionary, held a meeting here and brought Mead back into the fold. He then became so devout that, one Sunday, when he happened upon a swimming party, he shot at the people in the river, and threatened to kill anyone he again caught desecrating the Sabbath.”
—For the State of Nebraska, U.S. public relief program (1935-1943)