Light curve in the R band. Black diamonds indicate the light curve as measured by the OSIRIS camera onboard Rosetta (Mottola et al. 2014), arbitrarily shifted to match the rotational phase of VIRTIS observations. We assumed a comet rotational period of 12.4043 ± 0.0007 h (Sierks et al. 2015). The rotational phase is set to 0 at the time of the first VIRTIS acquisition T₀ = 56 850.0 MJD (Modified Julian Date). The color bar provides the phase angle scale in degrees for VIRTIS observations.