Thermal properties of comet 67P derived from Rosetta/VIRTIS, and orbital observations of Philae landing site

Abstract

The Rosetta spacecraft has reached its final target, comet 67P/Churyumov-Gerasimenko, in early August 2014. The VIRTIS imaging spectrometer onboard the Rosetta orbiter has intensively observed both the nucleus and the coma environment in the 0.25-5 microns wavelength range. Nucleus observations are performed with both channels: VIRTIS-M for spectral mapping and VIRTIS-H for high spectral resolution. Dayside surface temperatures in various illumination conditions can be retrieved from the long wavelength range. This allows us to infer local thermal properties. The very irregular shape of 67P results in unusual patterns in the heating / cooling regime of the object, e.g. sudden transitions from day to night. We will present thermal analyses of observations performed during the first mapping phase of the pre-landing activity (August 2014), with a focus on thermo-physical modeling of comet 67P on both regional and local scales, and a special emphasis on the expected landing site. These observations document the state of the comet surface at a time of large heliocentric distance and low activity.