Galactic Cosmic Ray Intensity 0.99 to 5.26 A.U. from the Sun.
IOWA UNIV IOWA CITY DEPT OF PHYSICS AND ASTRONOMY
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The intensity of galactic cosmic radiation in interplanetary space has been observed over the heliocentric radial range 0.99 less than r less than 5.26 a.u. with five Geiger-Mueller tubes on the Jupiter-bound spacecraft Pioneer 10 and over the range 1.00 less than r less than 3.59 a.u. with three similar tubes on Pioneer 11, also bound for Jupiter. The observations span the time period 1972 March 3 to 1974 April 29, near the epoch of minimum solar activity. The contributions of solar energetic particles are eliminated.