Instrument Overview
  ===================
    (excerpted from: [BAMEETAL1992A])
 
    Abstract.  -- The Solar Wind Plasma Experiment on Ulysses is
    accurately characterizing the bulk flow and internal state
    conditions of the interplanetary plasma in three dimensions on
    the way out to Jupiter.  These observations will continue over
    the full range of heliocentric distances and heliographic
    latitudes reached by the probe after its encounter with Jupiter
    and consequent deflection out of the ecliptic plane.  Solar
    wind electrons and ions are measured simultaneously with
    independent curved-plate electrostatic analyzers equipped with
    multiple Channel Electron Multipliers (CEMs).  The CEMs are
    arranged to detect particles at chosen polar angles from the
    spacecraft spin axis; resolution in spacecraft azimuth is
    obtained by timing measurements with the spacecraft Sun clock
    as the spacecraft spins.  Electrons with central energies
    extending from 0.86 eV to 814 eV are detected at seven polar
    angles and various combinations of azimuth angle to cover the
    unit sphere comprehensively, so as to enable computation of the
    pertinent electron velocity distribution parameters.  As the
    average electron flux level changes with heliocentric distance,
    command control of the CEM counting intervals is used to extend
    the dynamic range.  Ions are detected between 255 eV/q and 34.4
    keV/q using appropriate subsets of 16 CEMs at spin angles
    designed to provide matrices of counts as a function of energy
    per charge, azimuth angle, and polar angle centered on the
    average direction of solar-wind flow.  Data matrices are
    obtained every 4 min when the spacecraft is actively
    transmitting and every 8 min during data store periods.  These
    matrices contain sufficient energy and angle resolution to
    permit a detailed characterization of the ion velocity
    distributions, from which ion bulk parameters are derived.  As
    the average ion flux intensity changes with heliocentric
    distance, the entrance aperture size is periodically optimized
    by command selection from a set of seven apertures on a disk
    driven by a stepping motor.  Changes in the average solar wind
    flow direction relative to the Earth-pointing spacecraft spin
    axis are accommodated by command selection of the proper
    measurement matrix from a set of 11 matrices.  In a separate
    mode of operation and under favorable conditions, heavy ions of
    oxygen, silicon, and iron at various charge levels are
    resolved.