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Low-Energy Proton and Electron Differential Energy Analyzer (LEPEDEA)

NSSDCA ID: 1967-051A-04

Mission Name: IMP-F
Principal Investigator:Prof. James A. Van Allen


This experiment was designed to separately measure low-energy electron and proton intensities inside the magnetosphere and in the interplanetary region. The instrumentation system consisted of a cylindrical electrostatic analyzer (LEPEDEA or low-energy proton and electron differential energy analyzer) and a Bendix continuous channel multiplier (channeltron) array, and, in addition, an Anton 213 GM tube designed to survey the intensities of electrons with energies >40 keV in the outer magnetosphere. The electrostatic analyzer was capable of measuring the angular distributions and differential energy spectra of proton (25 eV to 47 keV) and electron (33 eV to 57 keV) intensities, separately, within 15 contiguous energy intervals. The analyzer accumulators were read out four times every 20.48 s. Each accumulation was about 480 ms long (spacecraft spin period was initially 2.6 s). A complete scan of the spectrum for four directions in a plane perpendicular to the spacecraft spin axis required 307.2 s for each energy interval. The detector responses for four approximately 60-deg segments of the angular distribution were slaved to the spacecraft telemetry system. The viewing direction of the segments was calculated from the spacecraft optical aspect information. The instruments performed normally from launch until the satellite decayed on May 3, 1969. For further details, see Frank, J. Geophys. Res., v. 75, p. 707, 1970.

Alternate Names



  • 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. Louis A. FrankOther InvestigatorUniversity of
Prof. James A. Van AllenPrincipal InvestigatorUniversity of Iowa
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