Pioneer Saturn Infrared Radiometer: Preliminary Results

The effective temperature of Saturn, 94.4 + 3 K, implies a total emission greater than two times the absorbed sunlight. The infrared data alone give an atmospheric abundance of H_2 relative to H_2 + He of 0.85 ± 0.15. Comparison of infrared and radio occultation data will give a more precise estimate. Temperature at the 1-bar level is 137 to 140 K, and 2.5 K differences exist between belts and zones up to the 0.06-bar level. Ring temperatures range from 60 to 70 K on the south (illuminated) side and from < 60 to 67 K in the planet's shadow. The average temperature of the north (unilluminated) side is ~ 55 K. Titan's 45-micrometer brightness temperature is 80 ± 10 K