Photometry of Io and Europa at the Crimean Astrophysical Observatory and reasons for differences between ground-based and space observations

Photometric observations of Jupiter’s moons Io and Europa in the spectral band V have been made at the Crimean Astrophysical Observatory for four years in order to construct their light curves reduced to a Solar phase angle of 6°. Comparison of these data with other ground-based observations shows good agreement. This study confirms why the moons that are close to Jupiter have a brighter leading hemisphere. The trailing hemispheres of Io and Europa, which are located in the rapidly rotating magnetic field of Jupiter, are exposed to bombardment by charged particles of the magnetic field. Leaving out of consideration the differences in brightness between the two hemispheres results in serious discrepancies between the space and ground-based photometry data.