First Results from ESA’s JUICE Lunar-Earth Flyby: Emphasis on Imaging Earth’s Ring Current and In-Situ Measurements of the Van Allen Radiation Belts

ESA’s JUpiter ICy moons Explorer (JUICE) mission performed the world’s first Lunar-Earth flyby on the 19-20 of August 2024, successfully rerouting the spacecraft toward Venus for another gravity assist. The Lunar-Earth Gravity Assist (LEGA) was not only critical for JUICE’s route to Jupiter, but it provided an invaluable opportunity for the science payload to gather measurements of Earth’s space environment. In this presentation, we focus on observations obtained from the Jupiter Energetic Neutrals and Ions (JENI) camera and the Jovian Energetic Electron (JoEE) magnetic spectrometer, which are a part of the comprehensive JUICE Particle Environment Package (PEP).          

The Lunar-Earth flyby brought JUICE to within ~750 km of the Moon’s surface and ~6,840 km over Earth. JUICE flew through Earth’s magnetotail visiting the plasma sheet, ring current, and radiation belt regions, before exiting the magnetosphere along the flank bringing the spacecraft back into the solar wind. The JENI and JoEE instruments were on and collecting science data for most of the excursion, except for critical spacecraft maneuvers. Therefore, JENI and JoEE made direct measurements of the energetic ions (~1 keV to several MeV) and electrons (~30 keV to 2 MeV) in those magnetospheric regions. During its outbound leg of the trajectory, the spacecraft performed a roll that placed Earth within JENI’s FoV allowing the camera to capture high-resolution images of Earth’s dynamical ring current. Several injections of hot plasma were observed in Earth’s nightside magnetosphere and appear to be linked to substorms. In this presentation, we summarize these exciting observations captured by JUICE during its LEGA and discuss the instrument performance of JENI and JoEE.