Three-Years of RADEM aboard the JUICE mission: Observations, Updates and Future Perspectives

The JUpiter ICy moons Explorer (JUICE) mission, launched on 14 April 2023, is currently in its interplanetary cruise phase and is expected to arrive at Jupiter in July 2031. Throughout its eight-year journey to the Jovian system, the spacecraft is exposed to a highly variable radiation environment dominated by galactic cosmic rays (GCRs) and episodic solar energetic particle (SEP) events. Upon arrival at Jupiter, JUICE will encounter one of the most intense radiation environments in the Solar System, characterized by powerful radiation belts populated primarily by highly energetic electrons. Monitoring and characterizing this radiation environment is therefore essential both for scientific return and for spacecraft and instrument safety.

To address these challenges, JUICE carries the RADiation-hard Electron Monitor (RADEM). RADEM was designed to measure high-energy protons (5-250 MeV), electrons (0.3-40 MeV), and to some extent ions (Z>=2). Since launch, RADEM has been operating continuously during the cruise phase, providing uninterrupted measurements of the energetic particle environment in interplanetary space.

After nearly three years of operations, RADEM has already recorded tens of SEP events associated with solar activity. These observations provide valuable insight into the spatiotemporal evolution, intensity, and spectral characteristics of energetic particles. In this work, we present an overview of RADEM’s in-flight performance and scientific observations to date. We also discuss updates and optimizations to the instrument’s operational settings implemented during cruise, aimed at improving the quality of its measurements.