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Electron and Proton Pitch Angle Distribution

NSSDCA ID: 1977-029A-01

Mission Name: ESA-GEOS 1
Principal Investigator:Dr. Berend Wilken


This instrument (ESA experiment S-321) measured the energy and pitch angle distribution of higher energy electrons and protons than the experiment of Hultqvist (77-029A-04), and was complementary to that instrument. The detector system consisted of two separate magnetic spectrometers for electrons with two proton telescopes associated with each of the magnets that served to focus the electrons away from the proton detectors. There were five rectangular solid-state detectors mounted along the focal line of each spectrometer to measure the electrons. Each spectrometer covered an angular aperture in elevation angle (relative to the spin axis) of 60 deg. The two deflection magnets were positioned so that elevation angles (referred to the spin axis) from 10 to 120 deg, on 10 deg centers, were covered for electrons, giving elevation angles of 23, 46, 83, and 106 deg for the proton telescopes. These telescopes consisted of a front surface-barrier detector and a rear solid-state detector. Electron energies from 30 to 200 keV and proton energies from 0.04 to 1.4 MeV were covered. The effective angular aperture for protons was 10 deg x 4 deg (elevation x azimuth) and for electrons was 6 deg x 4 deg. Geometric factors in units of 1.0E-4 sq cm sr were five for protons and one for electrons. A 12-channel pulse-height analyzer (PHA) for protons could be used for any one of the four front detectors, provided a front-rear coincidence was detected, and a 15-channel PHA could be used for any one of the 10 electron detectors. The singles rate for one of the four proton detectors and the coincidence rate from one of the four proton telescopes could be selected. There were three modes for data selection: mode 0, integral count rates and spectral measurements for all 14 detectors; mode 1, integral count rates and spectral measurements for four detectors (good time resolution on integral rates); and mode 2, integral count rates and spectral measurements (good time resolution for energy spectra). The minimum time for a complete spectrum was 688 ms; the minimum time for integral flux variations was 43 ms. The spectral measurements had a resolution of delta E/E=0.35.

Alternate Names

  • ESA-GEOS1/ElectronandProtonPitchAngleDistribution
  • S321

Funding Agency

  • European Space Agency (International)


  • 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
Prof. Georg PfotzerOther InvestigatorMax-Planck-Institut fur Aeronomie
Dr. Ehrhard KepplerOther InvestigatorMax-Planck-Institut fur
Dr. Axel KorthOther InvestigatorMax-Planck-Institut fur
Dr. J. MuenchOther InvestigatorMax-Planck-Institut fur Aeronomie
Dr. Berend WilkenPrincipal InvestigatorMax-Planck-Institut fur Aeronomie
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