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| Pioneer 4 launch cover with Goldcraft cachet. The United States followed Luna 1 in March 1959 with its Pioneer 4 fly-by spacecraft. Launched on 3 March 1959, Pioneer 4 passed within 60,000 kilometers (37,300 miles) of the moon, returned data on lunar radiation levels, then entered a solar orbit. |
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 was still in solar orbit as of 1969, the first U.S. spacecraft placed in solar orbit. 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.
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| Photo: Dr. Homer J. Stewart at press conference on March 4, 1959, said the Pioneer 4 probe has passed the moon and moved into an orbit around the sun. |
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| Pioneer 4 launch cover with Farley thermographic cachet. |
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| Photo: Flight path of Pioneer 4, the sun satellite. |
(Reference from
Pioneer 4)
