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Cadmium Sulfide Detector

NSSDCA ID: 1961-015B-02

Mission Name: Injun 1
Principal Investigator:Dr. John W. Freeman


A set of five directional cadmium sulfide (CdS) crystal energy flux detectors was used to study the flux of low-energy protons and ions trapped in the inner radiation belt. Two of the detectors (CdS total energy detectors oriented at 90 and 180 deg with respect to the satellite symmetry axis) had no physical obstruction between space and the crystal and were sensitive to electrons (200 eV to 500 keV) and protons (1 keV to 10 MeV). The second two CdS detectors (CdS proton energy detectors oriented at 90 and 180 deg with respect to the satellite symmetry axis) were identical to the total energy detectors but included small broom magnets that swept electrons with E<500 keV from the beam incident on the crystal. The magnets provided a field of 5.E-2 T and subtended a solid angle of 0.5 sr at the crystal. The fifth CdS detector (optical monitor oriented at 90 deg with respect to the satellite symmetry axis) was geometrically identical to the other four but was, in addition, fitted with a 0.5 gm/sq cm transparent quartz window and hence served as a light and X-ray detector. All five detectors had direct current outputs proportional to the incident charged corpuscular energy flux. The detectors were sampled at least once every second, and the detector accumulation times ranged from 9/64 to 61/64 s. (The spacecraft had a complex spin-and-tumble motion with an ill-defined and variable period of several minutes). The experiment performed nominally throughout the lifetime of the spacecraft.

Alternate Names

  • Injun1/CadmiumSulfideDetector
  • Low-Energy Protons and Ions Trapped in the Inner Radiation Zone

Facts in Brief

Mass: 0.6 kg
Power (avg): 0.1 W
Bit rate (avg): 0.256 kbps

Funding Agency

  • Department of Defense-Department of the Navy (United States)


  • 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. Brian J. O'BrienOther InvestigatorDepartment of Environmental
Dr. John W. FreemanPrincipal InvestigatorRice University
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