Mission Description
Explorer-II was to be a repeat of the Explorer I mission. However, there was a launch failure in the Jupiter-C rocket and Explorer II did not reach orbit.
The satellite was launched from Cape Canaveral (now Kennedy Space Center) in Florida on March 5, 1958, by a Jupiter-C launch vehicle.
The Jupiter-C has its origins in the United States Army's Project Orbiter in 1954. The project was canceled in 1955, however, when the decision was made to proceed with Project Vanguard.
Following the launch of the Soviet Sputnik I on October 4, 1957, ABMA was directed to proceed with the launching of a satellite using the Jupiter-C, which had already been flight-tested in nose-cone re-entry tests for the Jupiter IRBM (intermediate-range ballistic missile). Working closely together, ABMA and JPL completed the job of modifying the Jupiter-C and building the Explorer-I in 84 days.
Spacecraft Design
Explorer II was equipped with a geiger counter for the purposes of detecting cosmic rays. After Explorer III, it was decided that the original geiger counter had been overwhelmed by strong radiation coming from a belt of charged particles trapped in space by the Earth's magnetic field. (see: Van Allen radiation belt)
Mission Results
Explorer II failed to reach orbit due to Jupiter-C launch vehicle malfunction. Attempted orbit of Explorer-II (14.52 kg with 8.5 kg of instruments) failed because fourth stage did not ignite.
See Also
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