Assessing the Jovian Radiation Environment and its Impact on ESAs JUpiter ICy moons Explorer mission

Planetary missions to Jupiter face extreme challenges due to its intense radiation environment, one of the harshest in the Solar System. High-energy particles trapped in Jupiter’s magnetosphere can severely impact spacecraft systems and scientific instruments, requiring careful mitigation in trajectory planning and operations. The ESA JUICE (JUpiter ICy moons Explorer) mission addresses these hazards through optimized shielding, radiation-aware trajectory selection, and adaptive payload operations. A dedicated Radiation Working Group supports the mission through a variety of analyses aimed at assessing the harsh Jovian radiation environment and ensuring mission success. The activities of the working group can be divided into categories of modelling advancements and analysis which aims to support the mission operations to make the best possible decisions regarding the trajectory of JUICE by the end of 2026. We highlight in this presentation three of its activities: 1) refinement of the Jovian radiation environment estimations 2) Re‑evaluation of Ganymede’s magnetospheric shielding and its possible influence on the total ionizing dose experienced by JUICE across different trajectory and orbital configurations, and 3) radiation environment monitoring.

The “high latitude” phase up to 35 degrees inclination above the Jupiter equator during the Jupiter tour requires an update of the radiation model. In this context, the JOvian Specification Environment (JOSE) radiation model [SPENVIS] is being updated by ONERA. The Radiation Working Group is responsible for assessing the performance of existing radiation models and for testing the updated model (JOSE‑2) once it becomes available.

The Ganymede phase of JUICE’s mission is the largest contributor 58% of the total ionizing dose (TID) during the mission due to its extensive residence and position in Jupiter’s radiation belt. Ganymede possesses its own magnetosphere which is of high scientific interest and can act as a partial shield by deflecting energetic particles, potentially reducing the flux of incident Jovian particles at lower altitudes. at lower altitudes. Therefore, the estimation of shielding effect is crucial to calculate the TID JUICE will experience. Different models have been developed to compute the reduction in TID due to shielding. The Ganymede Radiation Environment Engineering Tool (GREET) developed by Kallisto Consultancy Ltd, which calculates electron flux spectra at different orbits depending on relative position to Ganymede, was originally used to generate environmental specification data. However, ongoing work by Liuzzo et al. [e.g. Liuzzo et al. 2020] since 2016 has introduced new advanced approach to shielding by as an example considering the plasma interaction with the current sheet of Jupiter. The results will show how the different approaches modified the flux predictions for the JUICE trajectory.

To monitor the harsh Jovian environment, JUICE carries an advanced radiation monitoring system, RADEM [Hajdas et al 2025], capable of measuring high-energy electrons, protons and ions. The mission also has a Juice Monitoring Unit (JMU) inside its electronics vault which will be used to compare the flux measured outside the spacecraft with RADEM with the TID inside the vault. In addition, instrument background (e. g. CCD noise) and radiation effects such as Single Event Upsets to on-board memories, will be correlated with various sources of energetic particles, providing unique information about the radiation environment.

References:

[SPENVIS] European Space Agency. (n.d.). TREP/JOREM model. SPENVIS. Retrieved May 11, 2026, from SPENVIS TREP/JOREM page

[Liuzzo et al. 2020] Liuzzo, L., Poppe, A. R., Paranicas, C., Nénon, Q., Fatemi, S., & Simon, S. (2020). Variability in the energetic electron bombardment of Ganymede. Journal of Geophysical Research: Space Physics, 125, e2020JA028347. https://doi.org/10.1029/2020JA028347

[Hajdas et al, (2025)]  Hajdas, W., Gonçalves, P., Pinto, M. et al. The JUICE Radiation Environment Monitor, RADEM. Space Sci Rev 221, 43 (2025). https://doi.org/10.1007/s11214-025-01163-9