The instrument consisted of dual 90-deg quadrispherical electrostatic analyzers, one with 26 individual particle detectors and the other with 5 current collectors. The system was capable of measuring incident plasma distribution parameters over the energy range 0.1 to 18 keV for protons and approximately 1 to 500 eV for electrons. The high-resolution analyzer with a constant of 9 keV/Q per kV applied to the plates, had a mean plate radius of 9 cm and separation of 0.5 cm. This analyzer was used to measure ions only, and had 26 channeltrons mounted on the semicircular exit to the analyzer. The aperture pointed through a wide slit in the back of the spacecraft high-gain antenna reflector and pointed along the spin axis toward the earth (and therefore the sun). The edges of the antenna reflector limited the viewing of the instrument to 73 deg with respect to the spin axis. The channeltrons covered a range of plus or minus 51 deg. Each channeltron near the center covered 3 deg and approximately 8 deg near the edges of the analyzer. The angular width perpendicular to the long angular width was about 2 deg. In half the spin period the whole cone of half-angle 51 deg centered on the sun was swept out. A medium-energy analyzer with a mean radius of 12 cm and a 1-cm plate separation (constant of 6 keV/Q per kV applied) was used to detect both ions and electrons. The detectors were five flat-surface current collectors. The three center collectors each covered 15 deg and covered the angular range of plus or minus 22.5 deg from the spin axis. The two outside collectors had an angular width of 47.5 deg and were located at plus or minus 46.25 deg from the center of the analyzer. There was a variety of possible operating modes for the experiment; however, the principal mode utilized during the encounter phase was one in which the analyzer plate potential was stepped through its range every one-half revolution of the spacecraft, and all current collectors or channeltrons were read out at the peak flux roll angle. The high and medium resolution analyzers operated independently, so a cross check between these analyzers was possible. The dynamic range for the particle fluxes was from 1.0E+2 to 3.0E+9/(sq cm-s) and the proton temperature down to 2.0E+3 deg K could be ascertained. Data include the interplanetary region. Detector A was turned off on September 16, 1987.

Instrument Overview
  ===================
    The plasma analyzer instrument carried by the Pioneer 11 spacecraft
    looked toward the Sun through a hole in the spacecraft's large
    dish-shaped antenna. The solar wind entered the plasma analyzer
    apertures between 2 quadraspherical plates where the direction of
    arrival, the energy, and the number of ions and electrons making up
    the solar wind were measured.
 
    The instrument had a high resolution and a medium resolution
    analyzer to detect particles of different energy levels. Energies of
    these particles were described in terms of electron volts (eV).
 
    A voltage was applied across the quadraspherical plates in a maximum
    of 64 steps, at a rate of one step per spacecraft revolution, to
    count particles in discrete energy ranges. Direction of particle
    travel was found from the way the instrument was pointed and from
    the particular target within the instrument that detected it.
 
    The high resolution analyzer had 26 continuous-channel multipliers
    (CCM) to measure the number of ions per second between 100 and 8,000
    electron volts. The medium resolution analyzer had five
    electrometers to count ions of 100 to 18,000 electron volts and
    electrons of 1 to 500 electron volts.
 
  ['Instrument Overview' was adapted from FIMMELETAL p. 50-51.]

extracted metadata from PDS3 catalog and
                    modified to comply with PDS4 Information Model

Pioneer 11 Quadrispherical Plasma Analyzer

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