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Electron Spectrometer

NSSDCA ID: 1964-054A-21

Mission Name: OGO 1
Principal Investigator:Dr. John R. Winckler


The objective of this experiment was to measure the electron energy spectrum in the radiation belts for the energy range from 50 keV to 4 MeV. The experiment consisted of a five-channel electron spectrometer containing an analyzing electromagnet, a plastic scintillator crystal, a photomultiplier tube, and a pulse-height analyzer. The analyzing electromagnet was used to define the five energy channels. The pulse-height analyzer accepted only pulses corresponding to the particular energy channel being sampled. In this way, the background due to bremsstrahlung and penetrating particles was reduced because only those background pulses in the narrow energy band being analyzed were counted. This system was mounted in the main body of the spacecraft and looked out in a direction 10 deg off the spacecraft Z axis, with a 15-deg acceptance cone. Since OGO 1 was spin stabilized (about its Z axis) shortly after launch, the acceptance cone was effectively increased to 35 deg. Directional measurements of electrons were made in five contiguous, logarithmically equispaced energy channels between 50 and 4000 keV. Background particles were counted by operating the spectrometer without the electromagnet. The system sampled the five spectral intervals and five background intervals every 2.304 s when the OGO 1 system was operating at 1 kbs. The sampling rate increased linearly with the telemetry bit rate. Data from each of the five channels were telemetered as one digital word. More details regarding experiment design may be found in Pfitzer, K. A., "An experimental study of electron fluxes from 50 keV to 4 MeV in the inner radiation belt," Ph.D. thesis, University of Minnesota, Minneapolis, Minn., August 1968 (TRF B01850). NSSDC has all the data sets that now exist from this investigation, except the highest time resolution ion chamber ramp data.

Alternate Names

  • OGO1/ElectronSpectrometer

Facts in Brief

Mass: 6.582 kg
Power (avg): 2.8 W
Bit rate (avg): 8 kbps

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • 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
Dr. Karl A. PfitzerOther InvestigatorMcDonnell-Douglas
Dr. Roger L. ArnoldyOther InvestigatorUniversity of New
Dr. John R. WincklerPrincipal InvestigatorUniversity of Minnesota
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