Observations of the JUICE PEP JEI plasma spectrometer during theMoon and Earth flyby in August 2024

The plasma spectrometer JEI is an ion and electron spectrometer designed to observe the thermal and medium energy charged particle environement  of Jupiter. It is part of the PEP instrument onboard JUICE. The flyby through the Earth-Moon system in August 2024 was the first test of the instrument in a magnetospheric plasma and under higher radiation. We will report on the instrument performance and on observations of charged particles in the lunar environment and during the crossing of the Earth magnetosphere. JEI was turned on during four short time periods near the moon, in the plasma sphere, and during magnetopause and bow shock crossings in the magnetosheath and back into the solar wind. During the lunar flyby JEi recorded photo electrons accelerated by a highly positive spacecraft potential and effects of spacecraft outgassing. The crossing of the Earth plasmasphere allowed a rare observation of the plasmasphere cold ion composition. This measurement was made possible by the combination of a negative spacecraft potential and a high spacecraft velocity.