Spotlight

Our knowledge of Mercury's plasma environment has significantly improved in the past decade thanks to new observations made by the Mercury orbiter MESSENGER. However, many questions remain unanswered. To provide more detail on this plasma environment, BepiColombo Mio was successfully launched by Ariane 5 from Kourou, French Guiana, on October 20, 2018, as part of a joint mission between the European Space Agency (ESA) and the Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency (ISAS/JAXA). The Mercury Plasma/Particle Experiment (MPPE) onboard Mio is a comprehensive instrument package used for plasma, high-energy particle, and energetic neutral atom measurements. It comprises seven sensors, including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High-Energy Particle instrument for the electron (HEP-ele), High-Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020, following the completion of the low voltage commissioning in November 2018. Although all the MPPE analyzers are now ready to begin conduct observations, the full-service performance has been delayed until Mio's landing on Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio—including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters—MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury, once BepiColombo/Mio will start conducting observations upon arrival at the planet Mercury in December 2025.