Images of Jupiter from the Pioneer 10 and Pioneer 11 Infrared Radiometers: A Comparison with Visible and 5-μm Images

All of the data acquired at Jupiter by the Infrared Radiometers on board Pioneers 10 and 11 are presented in the form of images with geometric control. The images are compared with 5-μm and visible images taken in the same time frame. The association of dark (blue or brown) and light (white or red) areas with warm and cool areas (at 5, 20, and 45 μm) respectively, extends to nearly all features observed on the planet. Where the normal association of light and dark visible markings with the zonal velocity breaks down (e.g., at the latitude of the South Equatorial Belt during the Pioneer encounters), the infrared emission seems to follow the visible cloud structure rather than the zonal velocity structure. Exceptions to the general rule involve 20-μm radiation, which reflects conditions in the altitude range 0.1–0.3 bar. For example, a comparison between Pioneer 10 and 11 images suggests that the South Equatorial Belt became brighter at 20 μm, but remained constant at other wavelengths between the two encounters