NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Charged Particle Detector

NSSDCA ID: 1958-005A-01

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


The purpose of this experiment was to extend the first measurements of the trapped radiation belt discovered with Explorers 1 and 3 and to provide measurements of artificially injected electrons from the three high-altitude Argus nuclear detonations. Four separate radiation detectors were used in the experiment: a shielded directional plastic scintillation counter sensitive to electrons (E>700 keV) and protons (E>10 MeV), a shielded directional cesium iodide scintillation counter sensitive to electrons (E>20 keV) and protons (E>400 keV), an omnidirectional Anton type 302 GM counter sensitive to electrons (E>3 MeV) and protons (E>30 MeV), and a shielded omnidirectional Anton type 302 GM tube sensitive to electrons (E>5 MeV) and protons (E>40 MeV). The plastic scintillation counter and the cesium iodide scintillation counter were each viewed by a separate photomultiplier tube. These detectors were mounted orthogonally to the longitudinal axis of the satellite with apertures facing in opposite directions. The two GM counters were located side by side along the satellite longitudinal axis. The plastic scintillation counter failed about September 3, 1958, while the two GM counters and the cesium iodide detectors continued to operate normally until September 19, 1958.

Alternate Names

  • Explorer4/ChargedParticleDetector


  • Space Physics: Magnetospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. George H. LudwigOther InvestigatorNOAA Environmental Research Laboratories
Prof. Carl E. McIlwainOther InvestigatorUniversity of California, San
Prof. Louis A. FrankOther InvestigatorUniversity of
Prof. James A. Van AllenPrincipal InvestigatorUniversity of Iowa
[] NASA Logo -