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Low-Energy Electron and Proton Pitch Angle Distribution

NSSDCA ID: 1977-029A-04

Mission Name: ESA-GEOS 1
Principal Investigator:Dr. Bengt K.G. Hultqvist


This instrument (ESA experiment S-310) measured the energy and pitch angle distribution of electrons and protons in the energy range 0.2 to 20 keV with extensive angular coverage concentrated in the loss cone region. The experiment of Wilken (77-029A-01) was complementary to this one and extended both electron and proton observations to higher energy ranges. The purpose of this investigation was to improve the understanding of auroral particle acceleration and precipitation mechanisms by comparing near-equatorial particle distributions with coordinated ground-based observations at the foot of the magnetic field line. High temporal and spatial resolution of the instrument was provided to study wave-particle interactions. A total of 10 curved-plate analyzers with channel electron multipliers for particle detection were used. Although normally eight analyzers were used to detect electrons and two to detect protons, a complex arrangement with four separate HV supplies allowed independent switching of four detector groups. The analyzing plate voltages could operate in a stepping mode, a sweeping mode, or a constant-voltage mode. In addition, the time accumulation could be varied with a nominal frame duration of 43 ms. However, this duration could be decreased by a factor of four at the expense of obtaining data from certain detectors in those cases where fast temporal variations were encountered in the loss cone. The energy intervals in the stepping mode consisted of 32 energy steps. The eight normal electron analyzers, with a geometric factor (G) of 3.0E-4 sq cm sr, consisted of four narrow-angle (2 deg x 2 deg, delta E/E of 0.11) and four wide-angle (8 deg x 7.5 deg, delta E/E of 0.09) devices. The two normal proton analyzers had delta E/E of 0.13, aperture of 6 deg x 3 deg, and G of 1.0E-3 sq cm sr. Aperture angular widths refer to elevation and azimuth, respectively, in relation to the spacecraft spin axis. This experiment planned to rely heavily on real-time ground computer control. This was possible over the eastern longitude apogee in view of the ESA-GEOS 1 ground station antenna at Michelstadt, Federal Republic of Germany, but not for the other daily apogee over the Pacific Ocean.

Alternate Names

  • ESA-GEOS1/Low-EnergyElectronandProtonPitchAngleDistribution
  • S310

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
Dr. Hans BorgOther InvestigatorKiruna Geophysical
Mr. Lars-Ake HolmgrenOther InvestigatorKiruna Geophysical Institute
Dr. Bengt K.G. HultqvistPrincipal InvestigatorKiruna Geophysical
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