The Philae lander, part of the Rosetta mission to investigate comet 67P/Churyumov-Gerasimenko, was delivered to the cometary surface in November 2014. Here we report the precise circumstances of the multiple landings of Philae, including the bouncing trajectory and rebound parameters, based on engineering data in conjunction with operational instrument data. These data also provide information on the mechanical properties (strength and layering) of the comet surface. The first touchdown site, Agilkia, appears to have a granular soft surface (with a compressive strength of 1 kilopascal) at least ~20 cm thick, possibly on top of a more rigid layer. The final landing site, Abydos, has a hard surface.

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We report an analysis of the Comet Acoustic Surface Sounding Experiment (CASSE) acceleration signals at Philae's first touchdown site Agilkia on comet 67P/Churyumov-Gerasimenko. The signals yield the forces in the contact zone foot-sole and comet surface, and from these forces a compression strength of approximately 10 kPa can be derived. The sole's contact-resonances provide an elastic modulus of the order of 10 MPa. Our results are partially based on calibration experiments, which are described in the appendix of the current paper. Relations known in material science, linking porosity to elasticity and fracture energy, allow one to check the interdependence between compression strength and elasticity