GALILEO PHOTOPOLARIMETER-RADIOMETER OBSERVATIONS OF JUPITER AND THE GALILEAN SATELLITES

Photopolarimeter-Radiometer (PPR) maps of daytime temperatures on Gany mede at a resolution of 220 kilometers show the expected anticorrelati on with albedo, but morning temperatures were about 10 kelvin warmer t han expected. Europa had a subsolar temperature of 128 kelvin and a lo wer effective thermal inertia than either Ganymede or Callisto, and Io 's night side was cooler than predicted by recent models, perhaps requ iring revision of heat-flow estimates. The lowest 250-millibar tempera tures in the Great Red Spot (GRS) generally corresponded to the visual ly darkest regions, Temperatures remained cold north of the GRS, but t hey rose by as much as 6 kelvin to the south over the 2800-kilometer P PR resolution. A visually bright region northwest of the GRS was also relatively cold. It is likely that NH3 clouds affected the determinati on of the 500-millibar temperature field, which appears qualitatively different.