Surface charging of the JUICE spacecraft during the 2024 Earth gravity assist

Abstract. The JUICE spacecraft performed an Earth gravity assist during the 20-21st August 2024 encountering a range of different plasma environments. An understanding of the surface charging of the spacecraft is important in increasing the scientific output of the instruments, allowing for the development of correction techniques. The surface charging in two of these environments, in the plasmasphere at closest approach (2.07 RE) and in the magnetosheath, was explored through simulations using the SPIS software. The average surface charging of the conductive surface was found to charge negatively in the plasmasphere to -2 V and positively in the magnetosheath to 2.5 V. Differential charging was observed in both environments due to different materials covering the spacecraft, with the dielectric materials charging from -0.8 to -6 V in the plasmasphere and 7 to -70 V in the magnetosheath. The effect of the spacecraft on the particle environment was also studied, looking at the formation of ion wakes and the photoelectron cloud. In the plasmasphere, the impact of exposed potentials on the solar array was also studied and found not to have any significant effect on the overall charging of the spacecraft. The results obtained here during the Earth swing-by can also be applied when JUICE performs later gravity-assists again at the Earth and the results will be relevant when encountering similar environments at Jupiter and its moons.