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Cosmic Ray Detector

NSSDCA ID: 1962-041A-04

Mission Name: Mariner 2
Principal Investigator:Dr. Hugh R. Anderson


The particle experiment was designed to: (1) investigate the dependence of the intensity of ionizing particles in space upon distance from the sun; (2) examine temporal variations of the particles and their correlation with variations of the magnetic field and plasma flux at the location of the spacecraft and with solar-terrestrial disturbances; and, (3) characterize the intensity and extent of magnetically trapped particles, if any, around Venus. The instrumentation consisted of three detectors: (1) a gas-filled, integrating, ionization chamber with a wall of stainless steel; (2) an omnidirectional thin-walled cylindrical glass Geiger-Mueller (GM) tube shielded with stainless steel; and, (3) an identical glass GM tube shielded with beryllium. The two GM tubes differed in the efficiency with which they detected non-penetrating electrons by the Bremsstrahlung process. All three detectors were sensitive to electrons of energies greater than 500 keV and protons of energies greater than 10 MeV. The ionization chamber was sampled for 221.76 s once every 443.52 s. The count accumulation of the GM tube shielded with stainless steel was sampled once for 0.828 s and once for 9.6 s every 443.52 s, and the count accumulation of the beryllium-shielded GM tube was sampled once for 0.828 s and once for 9.6 s every 887.04 s. The detectors were mounted close together with the axes of the GM tubes perpendicular to the roll axis of the spacecraft and hence to the radius vector from the sun. The GM tubes shielded with stainless steel and beryllium had omnidirectional geometric factors of 6.97 and 6.91 sq cm, respectively. The experiment operated normally throughout the mission.

Alternate Names

  • Mariner2/CosmicRayDetector

Facts in Brief

Mass: 1.2 kg
Power (avg): 0.3 W


  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. H. Victor NeherCo-InvestigatorCalifornia Institute of Technology
Prof. James A. Van AllenCo-InvestigatorUniversity of Iowa
Dr. Hugh R. AndersonGeneral ContactRice University
Dr. Hugh R. AndersonPrincipal InvestigatorRice University

Selected References

  • Neher, H. V., and H. R. Anderson, Change of cosmic-ray intensity with distance from the sun, J. Geophys. Res., 69, 1911-1913, doi:10.1029/JZ069i009p01911, May 1964.
  • Anderson, H. R., Energetic particles measured near Venus by Mariner 2, J. Geophys. Res., 69, 2651-2657, doi:10.1029/JZ069i013p02651, July 1964.
  • Anderson, H. R., Mariner II: High-energy radiation experiment, Science, 139, 42-45, doi:10.1126/science.139.3549.42, Jan. 1963.
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