Pioneer 4
NASA robotic spacecraft designed to study the Moon / From Wikipedia, the free encyclopedia
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Pioneer 4 was an American spin-stabilized uncrewed spacecraft 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.[3] 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.
Mission type | Lunar flyby |
---|---|
Operator | NASA |
Harvard designation | 1959 Nu 1 |
COSPAR ID | 1959-013A |
SATCAT no. | 00113 |
Mission duration | 3 days |
Spacecraft properties | |
Spacecraft type | Pioneer |
Manufacturer | Jet Propulsion Laboratory |
Launch mass | 6.08 kg[1] |
Start of mission | |
Launch date | 3 March 1959, 05:10:56 GMT |
Rocket | Juno II |
Launch site | Cape Canaveral, LC-5 |
Contractor | Chrysler Corporation |
End of mission | |
Last contact | 6 March 1959, 15:40:00 GMT |
Orbital parameters | |
Reference system | Heliocentric |
Semi-major axis | 1.1015 astronomical units (164,780,000 km; 102,390,000 mi) |
Eccentricity | 0.07109 |
Perihelion altitude | 0.98 astronomical units (147,000,000 km; 91,000,000 mi) |
Aphelion altitude | 1.13 astronomical units (169,000,000 km; 105,000,000 mi) |
Inclination | 1.5° |
Period | 398.0 days |
Epoch | 3 March 1959 [2] |
Flyby of Moon | |
Closest approach | 4 March 1959, 22:25 GMT |
Distance | 58,983 kilometres (36,650 mi) |
After the Soviet Luna 1 probe conducted the first successful flyby of the Moon on 3 January 1959, the pressure felt by the US to succeed with a lunar mission was enormous, especially since American mission failures were entirely public while the Soviet failures were kept a secret.