Measuring thermo-mechanical properties of cometary surfaces - In situ methods

Thermal and mechanical properties of cometary ices are closely associated with each other. Both are largely determined by the texture (porosity, grain size distribution, grade of sintering) of the material. The surface probe of the Rosetta mission to Comet 46P/Wirtanen (Rosetta Lander) will for the first time measure these thermomechanical key parameters in situ, using a hammering device, a drill, and anchors to be shot into the ground by pyrotechnical means. Several of these components are associated with the experiment MUPUS (MUlti-PUrpose-Sensors for surface and subsurface science). The development of this instrument has now reached a mature state, as the flight model is already delivered and integrated with the spacecraft. We describe the main aspects of the experiment, outline the evaluation methods, and show representative results from test measurements. (Author)