Dust and spacecraft charging in Saturn's E ring

Abstract

The electrostatic potential of a spacecraft reflects the local physical conditions and also affects the in situ thermal plasma measurements. In this work we focus on the spacecraft charging in the high dust density region near Enceladus in Saturn's E ring. In a dust-rich environment, the spacecraft charging is modified by the complex (dusty) plasma conditions as well as by the additional dust-associated charging currents (dust ram current and the dust impact plasma current). Adopting the Cassini plasma electron and dust profiles, we explore the longitudinal and latitudinal spacecraft potential variations in the E ring. Our results show that, under dust-rich condition, the spacecraft potential is neutralized due to the collection of the dust impact plasma ions. We suggest a systematic verification of our model calculation with the Cassini in situ measurements and also a search for signatures of dust-spacecraft impact plasma in the Cassini thermal plasma measurements.