Rosetta, the ESA-NASA Comet Nucleus Sample Return (CNSR) mission, which will bring cometary material to Earth could be the key to understanding the chemical and physical process that marked the beginning of the Solar System. A major mission requirement is to keep the material samples on the in-situ temperature level to prevent any phase changes or alteration of its chemical composition. Since the a-priori knowledge of the extraterrestrial cometary surface is not very detailed before the implementation of the mission, and the implications on the spacecraft design as well as onto the mission scenario itself are mandatory, an engineering database for the expected thermal environment has been established. For that purpose a simplified thermal comet model has been created, applying the ESATAN software package. The model comprises thirteen material and comet parameters governing die cometary superficial heat balance as well as the cometary shape and mechanics. As an outcome of these simulations a landing site selection strategy was developed offering appropriate landing sites which meet the temperature requirements and provide a sufficient period for telecommands from Earth during each comet revolution. Subsequently a reference scenario was defined and analysed based on a typical set of parameters.