MICROWAVE SPECTRUM OF SATURN

Two atmospheric models which may account for Saturn's microwave spectrum are discussed. The two models considered are (1) thermal emission by a deep atmosphere with a temperature gradient, and (2) free-free emission by an ionosphere. The deep atmosphere model is found to be in agreement with the present measurements of the spectrum. If ammonia is assumed to be the only source of opacity in the radio frequency range, then the required ammonia abundance is consistent with that expected from an atmosphere containing a cosmic abundance of elements. The required ammonia abundance suggests that the observed clouds are not ammonia clouds. Free-free emission cannot explain the microwave spectrum if the ionosphere is primarily formed by photoionization by solar ultraviolet radiation. An attempt was made to detect radio emission from Saturn at 70 cm. Saturn was not detected. The upper limit we place on the equivalent brightness temperature at 70 cm is 1250°K. © 1969.