Results of the infrared radiometer experiment on Pioneers 10 and 11

Abstract

The infrared radiometers on the Pioneer 10 and 11 spacecraft have mapped Jupiter in two broad spectral channels centered at wavelengths of 20 and 45 µm. Comparison of Pioneer 10 and 11 data and the results of in-flight and laboratory calibrations indicate an absolute accuracy of ± 8% in the measured intensities. Relative accuracy, for comparing different regions on the planet, is ± 2%. Within the precision of observations, the derived value of effective temperature is independent of assumptions about the Jovian emission spectrum. The global effective temperature is 125 ± 3°K, implying a value of 1.9 ± 0.2 for the ratio of planetary thermal emission to solar energy absorbed. The effective temperatures of belts are greater than those of zones by as much as 3°.5 K. On a global scale, the poles and equator have the same effective temperature.