EUV reflectance of Mercury measured by BepiColombo/PHEBUS
Résumé
BepiColombo will be inserted around Mercury in December 2025, but during the cruise phase, several opportunities to perform disk-integrated observations of Mercury are possible. The first observations of the illuminated surface of Mercury by PHEBUS (Probing of Hermean Environment by Ultraviolet Spectroscopy) with the EUV channel ( ∼ 55-160 nm) were done on 9 and 10 Oct 2021, few days after the first flyby, from a distance of ∼.03 AU at a phase angle of 72°. The solar reflected spectrum is detected from 80 nm to 160 nm. We present the EUV reflectance of Mercury derived from these observations and compare its spectral variations to the measurements by Mariner 10 done at few wavelengths in this spectral range and to the MESSENGER observations done at longer wavelengths.