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Quadrispherical Plasma Analyzer

NSSDCA ID: 1973-019A-13

Mission Name: Pioneer 11
Principal Investigator:Dr. Aaron Barnes


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.

Alternate Names

  • Pioneer11/QuadrisphericalPlasmaAnalyzer
  • urn:nasa:pds:context:instrument:pa.p11

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science: Fields and Particles
  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. John F. Cooper



NameRoleOriginal AffiliationE-mail
Dr. Frederick L. ScarfOther InvestigatorTRW Systems Group
Prof. Devrie S. IntriligatorOther InvestigatorCarmel Research
Prof. Louis A. FrankOther InvestigatorUniversity of
Prof. Reimar LuestOther InvestigatorEuropean Space Agency
Mr. Harold R. CollardOther InvestigatorNASA Ames Research Center
Mr. Darrell D. McKibbinOther InvestigatorNASA Ames Research Center
Mr. V. T. ZavientseffOther InvestigatorNASA Ames Research Center
Dr. Zdenka K. SmithOther InvestigatorNOAA Space Environment
Dr. William C. FeldmanOther InvestigatorLos Alamos National
Dr. Aaron BarnesPrincipal InvestigatorNASA Ames Research Center

Selected References

  • Wolfe, J. H., et al., Pioneer 10 observations of the solar wind interaction with Jupiter, J. Geophys. Res., 79, No. 25, 3489-3500, doi:10.1029/JA079i025p03489, 1974.
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