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Ion Chamber

NSSDCA ID: 1958-007A-01

Mission Name: Pioneer 1
Principal Investigator:Dr. Charles P. Sonett


The ion-chamber experiment was designed to study the high flux radiation surrounding the earth. The instrument was an aluminum-walled, cylindrically shaped vessel with a volume of 43 cubic cm filled with spectroscopically pure argon. It was mounted just inside the cylindrical wall of the satellite. The minimum areal density that a particle traversed before reaching the sensitive volume of the chamber was 0.45 gm/sq cm, the maximum was 20 gm/sq cm. The current from the ion chamber was measured by a DC electrometer amplifier with a range of 0.5 Roentgens/hr to 1E7 Roentgens/hr. The duty cycle of the instrument consisted of 180 sec of ionization chamber output followed by 20 sec of calibration voltage. The chamber was capable of responding to primary cosmic rays and also to the secondary mesons, protons, beta particles, and gamma rays that may result from the interaction of the primary particles with the walls of the chamber and the material surrounding the ion chamber. The secondaries could increase the ionization a factor of 50. Electrons must have an energy greater than 1 MeV, protons greater than 5 MeV, and alphas greater than 200 MeV in order to penetrate the walls of the chamber. It was discovered that the ion chamber had leaked and that the pressure during flight was 1.58 atmospheres. Consideration of all other errors resulted in a standard deviation as great as 50 percent for some data points. Most of the data were transmitted from 1000 to 1800 UT on October 11, 1958, and from 0800 to 2100 UT on October 12, 1958. See Rosen et al, JGR, vol 64, p 709, 1959, for further details and for resultant data.

Alternate Names

  • Pioneer1/IonChamber


  • 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
Dr. Alan RosenOther InvestigatorTRW Systems Group
Prof. Paul J. Coleman, Jr.Other InvestigatorUniversity of California, Los Angeles
Dr. Charles P. SonettPrincipal InvestigatorUniversity of Arizona
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