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Trapped Radiation Experiment

NSSDCA ID: 1959-013A-01

Mission Name: Pioneer 4
Principal Investigator:Prof. James A. Van Allen


Two Geiger-Mueller tubes were used to conduct a survey of the trapped radiation surrounding Earth. An Anton-type 302 tube had its output counted by a 17-stage binary scaler in order to cover the extreme dynamic ranges expected in counting rates within the bandwidth of the communications system. This counter would saturate at about 10 roentgen/hr. An Anton-type 213 tube which saturated at about 100 roentgen/hr was used to provide coverage in the high-intensity region of radiation. The tube was encased in a lead closed-end cylinder of thickness 4.0 grams per square cm and an inner stainless steel cylinder of 0.6 grams per square cm. The counters were designed to count up to 200,000 radiation strikes per second, covering proton energies >30 MeV and electron energies > 2.2 MeV. The Geiger-Mueller tubes were mounted at the base of the nose cone within the thin fiberglass casing. The spacecraft was launched March 3, 1959 into a heliocentric orbit and passed within 60,000 km of the Moon, but no radiation was detected in the vicinity of the Moon. This was the same instrument as was used on Pioneer 3 except for the shielding added to the Anton 213 tube.

Alternate Names

  • Pioneer4/TrappedRadiationExperiment
  • Survey of Trapped Radiation, GM Detector

Funding Agency

  • NASA-Office of Space Science (United States)


  • Space Physics: Heliospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Prof. Louis A. FrankOther InvestigatorUniversity of
Prof. James A. Van AllenPrincipal InvestigatorUniversity of Iowa
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