The Pioneer 8 and 9 Cosmic Ray Detector System

An instrument designed to measure the directional properties of cosmic ray propagation in the energy range 1-63 MeV per nucleon during solar active years is described. This instrument has been flown on the interplanetary space vehicles Pioneers 8 and 9. The detector package is discussed with regard to its mechanical, electrical, and data conditioning properties. In-flight calibration procedures are briefly discussed.