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Ion Chamber and GM Counters

NSSDCA ID: 1966-058A-04

Mission Name: Explorer 33
Principal Investigator:Prof. Kinsey A. Anderson


This experiment consisted of a 10.2-cm, Neher-type ionization chamber and two Lionel type 205 HT Geiger-Mueller (GM) tubes. The ion chamber responded omnidirectionally to electrons above 0.7 MeV and protons above 12 MeV. Both GM tubes were mounted perpendicular to the spacecraft spin axis. GM tube A detected electrons above 45 keV which were scattered off a gold foil. The acceptance cone for these electrons had a full-angle of 61 deg and axis of symmetry which was perpendicular to the spacecraft spin axis. GM tube B responded to electrons and protons above 22 and 300 keV, respectively, in an acceptance cone of 45-deg full-angle with axis of symmetry perpendicular to the spacecraft spin axis. Both GM tubes responded omnidirectionally to electrons and protons of energies above 2.5 and 35 MeV, respectively. Pulses from the ion chamber and counts from each GM tube were accumulated for 39.72 s and read out every 40.96 s. The time between the first two ion-chamber pulses in an accumulation period was also telemetered. The ion chamber operated normally from launch through September 2, 1966. From September 2, 1966, the ion chamber operated at a lower threshold voltage. For further details, see Lin, Solar Physics, v. 12, p. 266, 1970. NSSDC has all the useful data that now exist.

Alternate Names

  • Energetic Particles
  • Explorer33/IonChamberandGMCounters


  • Space Physics: Magnetospheric Studies
  • 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. Kinsey A. AndersonPrincipal InvestigatorUniversity of California,
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