Estimating spectral photometric properties of the 67P/Churyumov-Gerasimenko comet nucleus

The Rosetta spacecraft successfully studied the 67P/Churyumov-Gerasimenko comet from 2014 to 2016, when the mission ended with an attempt to land the satellite on the comet nucleus. Despite the presence of the scientific camera OSIRIS on board the spacecraft, several researchers used images of the navigational camera (NavCam) for supporting their analysis of the target. The radiometric calibration of the NavCam allowed the construction of an extended catalogue of NavCam images for which the average radiance and reflectance of the comet nucleus was calculated. Here, that data set is used to fit Hapke’s model for the reflectance to deliver a set of parameters that describe the photometric properties of the comet nucleus. The results allowed for the calculation of the geometric and bond albedo of the target, as well as information on the single scattering albedo, average roughness angle, asymmetric factor and shadow-hiding opposition effect as a function of the phase angle.