Saturn's emitted power

Long-term (2004-2009) on-orbit observations by Cassini Composite Infrared Spectrometer are analyzed to precisely measure Saturn's emitted power and its meridional distribution. Our evaluations suggest that the average global emitted power is 4.952 +/- 0.035 W m(-2) during the period of 2004-2009. The corresponding effective temperature is 96.67 +/- 0.17 K. The emitted power is 16.6% higher in the Southern Hemisphere than in the Northern Hemisphere. From 2005 to 2009, the global mean emitted power and effective temperature decreased by similar to 2% and similar to 0.5%, respectively. Our study further reveals the interannual variability of emitted power and effective temperature between the epoch of Voyager (similar to 1 Saturn year ago) and the current epoch of Cassini, suggesting changes in the cloud opacity from year to year on Saturn. The seasonal and interannual variability of emitted power implies that the energy balance and internal heat are also varying.