2024 Earth Gravity Assist: Finding the Surface Charging of the Juice Spacecraft

We use the Spacecraft Plasma Interaction Software (SPIS) to simulate the interaction between the JUICE spacecraft and its environment during the Earth gravity assist performed on the 20th August 2024. A world first was achieved by the JUICE spacecraft through its execution of a double gravity assist with both the Moon and the Earth. During this encounter, JUICE crossed various regions of the magnetosphere, approaching from the magnetotail after the lunar assist, before exiting into the magnetosheath and then the solar wind.
We focus on the plasmasphere and magnetosheath regions, looking at how the interaction between JUICE and these environments affects the surface charging on the spacecraft and the effect on the local particle environment. This work is essential in understanding the effect on the particle and field measurements made by JUICE, so is crucial for the data analysis.
Here we present surface potentials and local electron, photoelectron and ion populations for two plasma regimes in the plasmasphere and magnetosheath. The effect of the fixed positive potentials of the solar array busbars on the final surface potential in the dense plasmasphere environment is also simulated. These fixed potentials are likely to play a critical role in future measurements of the ionospheres of Jupiter’s icy moons, as they are cold plasma environments where spacecraft surface charging can substantially impact observations. The impact of the spacecraft-environment interactions on the JUICE RPWI and PEP particle and field measurements is then discussed. Large differential charging was observed on the spacecraft due to the presence of dielectric material on the high-gain antenna and covering the radiators.