Instrument Host Overview
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      Energetic protons and heavy nucleons are detected
      by three identical charged- particle telescopes
      aligned at different angles (30deg, 60deg and
      135deg) to the spin axis which is perpendicular to
      the ecliptic plane..  Each telescope consists of a
      1 cm**2 solid-state detector of 30 micron thickness
      immediately followed by a 2 cm**2 detector of 150
      micron thickness in anticoincidence.  Pulse-height
      analysis resolves the particle total kinetic
      energies into eight channels between 35 keV and 1.6
      MeV for protons.  (These ranges are slightly
      mass-dependent for heavy ions because of detector
      dead-layer effects.) The count rate from each
      telescope and each channel is resolved into eight
      sectors in the equatorial plane to measure the
      anisotropy of the particles.  A mechanical
      collimator defines a 16 degree half-width viewing
      cone and a geometrical factor of 0.05 cm2 sr for
      each telescope.  A magnetic broom prevents < 400
      keV electrons from entering the telescope while
      higher energy electrons trigger the second detector
      and so are not counted.  To sample the three
      telescopes, eight energies and eight sectors
      requires 32 s at 1024 bit/s.