On the Cause of Discrepancy Between Ground-based and Spaceborne Light Curves of the Galilean Satellites of Jupiter

Photometric observations of Jupiter's satellites in the spectral band V were carried out at the Scientific Research Institute “CrAO”. Their light curves were brought to a phase angle of the Sun equal to 6°. Comparison of these data with other ground-based observations showed good agreement. The cause of discrepancy between data obtained by spacecrafts is a backscattering effect of sunlight, which depends on the phase angle of the Sun. The satellite Callisto has a dark leading hemisphere due to the fact that at this distance the magnetic field of Jupiter appears to be significantly weakened, and bodies of the interplanetary medium bomb it out.