Observation of Helium in Mercury's Exosphere by PHEBUS on Bepi-Colombo

International audienceThe Bepi-Colombo mission is an international cooperation between the European Space Agency, ESA, and the Japan Aerospace Exploration Agency, JAXA. Its aim is to study Mercury and its environment. It has been launched in October 2018 and is composed of two satellites that will be put in orbit at the end of 2025. PHEBUS, an acronym for Probing the Hermean Exosphere By Ultraviolet Spectroscopy, is an ultraviolet spectrograph on board ESA's Mercury Planetary Orbiter (MPO). The main objective of this instrument is to study the Hermean exosphere and its interactions with the surface and the solar wind. The primary objectives and design of PHEBUS are described by Chassefière et al. (2010). Quémerais et al. (2020) gave an early report on the status of PHEBUS based on ground calibration activities. Since the post-launch commissioning activities of 2019, PHEBUS has performed observations of stars, planetary objects (Moon and Venus) and the interplanetary background. O