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Explorer 7X



Explorer 7X (S-1) was launched at 16:37 UT on 16 July 1959 from the Atlantic Missile Range in Cape Canaveral, Florida on a Juno 2 rocket. It was destroyed by the Range Safety Officer 5-1/2 seconds after liftoff when it tilted sharply because of a failure of the power supply to the guidance system. The satellite was nearly identical to the later successfully launched Explorer 7.

The mission objectives were to measure the Earth's radiation balance, Lyman-alpha x-rays, heavy primary cosmic rays, micrometeorites, cosmic rays, satellite temperature, and erosion of exposed solar cells. The satellite had the shape of two truncated cones joined at the base, 76 cm in diameter and 71 cm high, with a mass of 41.5 kg. It held instrumentation to achieve the mission objectives and two transmitters, one solar powered, 20 MHz at 650 mW designed for cutoff after one year, and one battery powered, 108 MHz at 15 mW designed to operate for two months.

The Juno 2 launch vehicle (AM-16) comprised a modified Army Jupiter IRBM first stage, a cluster of 11 scaled-down Sergeant rockets for the second stage, three scaled-down Sergeants for the third stage, and a fourth stage of one scaled-down Sergeant. The rocket was 23.2 m high and 2.67 m in diameter at the base. Lift-off mass was 54,900 kg.

Alternate Names

  • Explorer7X
  • S 1

Facts in Brief

Launch Date: 1959-07-16
Launch Vehicle: Juno 2 (Juno II)
Launch Site: Cape Canaveral, United States
Mass: 41.5 kg


  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

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