NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Medium Energy Particles Instrument - Distrib. fns., p > 24 keV, e > 20 keV

NSSDCA ID: 1977-102A-09

Mission Name: ISEE 1
Principal Investigator:Dr. Donald J. Williams


This experiment was designed to identify and to study plasma instabilities responsible for acceleration, source and loss mechanisms, and boundary and interface phenomena throughout the orbital range of the mother/daughter satellites. A proton telescope and an electron spectrometer were flown on each spacecraft to measure detailed energy spectrum and angular distributions. These detectors used silicon surface-barrier, totally depleted solid-state devices of various thicknesses, areas, and configurations. Protons in 8 or 16 channels between 20 keV and 1.2 MeV, and electrons in 8 or 16 channels between 20 keV and 1 MeV, were measured. A separate solid-state detector system measured the energy spectra and pitch-angle distributions of alpha particles and heavy ions in the energy range above 125 keV per nucleon.

Alternate Names

  • MEPI

Facts in Brief

Mass: 8 kg
Power (avg): 8.5 W


  • Space Physics: Magnetospheric Studies
  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Dr. Berend WilkenOther InvestigatorMax-Planck-Institut fur Aeronomie
Dr. Carl O. BostromOther InvestigatorApplied Physics Laboratory
Dr. Ehrhard KepplerOther InvestigatorMax-Planck-Institut fur
Prof. Gerd H. WibberenzOther InvestigatorUniversitat
Prof. Theodore Allan FritzOther InvestigatorLos Alamos National
Dr. Donald J. WilliamsPrincipal InvestigatorApplied Physics

Selected References

  • Williams, D. J., Magnetopause characteristics inferred from three-dimensional energetic particle distributions, J. Geophys. Res., 84, No. A1, 101-104, doi:10.1029/JA084iA01p00101, Jan. 1979.
  • Williams, D. J., et al., ISEE 1 and 2 medium energy particles experiment, IEEE Trans. Geosci. Electron., GE-16, No. 3, 270-280, doi:10.1109/TGE.1978.294561, July 1978.
  • Williams, D. J., et al., Three-dimensional magnetosheath plasma ion distributions from 200 eV to 2 MeV, J. Geophys. Res., 93, No. A11, 12783-12794, doi:10.1029/JA093iA11p12783, Nov. 1988.
  • Williams, D. J., The earth's ring current: Present situation and future thrusts, Physica Scripta, 35, 140-151, doi:10.1088/0031-8949/1987/T18/015, 1987.
[] NASA Logo -