The objective of the Comprehensive Plasma Instrumentation (CPI) investigation is to make comprehensive observations of the three-dimensional velocity distribution functions of electrons and positive ions, with identification of ion species. The instrument contains three sets of quadrispherical analyzers with channel electron multipliers. These three obtain three-dimensional measurements for hot plasma and solar wind electrons, for solar wind ions, and for positive-ion composition measurements. The positive-ion composition measurement of the Ion Composition (IC) analyzer includes five miniature imaging mass spectrometers at the exit aperture of the analyzer, and covers masses from 1 to 550 u/Q at 100 eV, and 1 to 55 u/Q at 10 keV. The Hot Plasma (HP) analyzer measures electrons and ions in the range 1-50,000 eV/Q. The Solar Wind (SW) analyzer measures ions from 150 to 7,000 eV/Q. Sequencing of the energy analyzers and mass spectrometers, and other control functions, are provided by two microprocessors.