Periodic intensity variations in global ENA images of Saturn

During select time periods in orbit about Saturn, Cassini's Ion and Neutral Camera (INCA) has detected a periodic global ENA signal. Images taken during such periods reveal the presence of a rotating source component in addition to a steady-state component; both components have peak brightness in the midnight sector, when viewed from near dawn. We present a model that synthesizes some of the basic features of the data and gives good agreement with the integrated signal. Both components, as well as the Compton-Getting effect whose importance was previously unrecognized in ENA imaging, are needed to explain some aspects of the data.