Dynamical effects of comet P/Halley gas production

We revisit tile rotation of P/Halley taking into account the most essential observational constraints. as well as the external torques affecting the n ucleus, in particular the outgassing torque. We solve tile dirty ice sublim ation equations at each point of the sunlit surface, using, for tile first time, the surface shape derived from the 1986 flybys imaging data. We assum e that the nuclear surface is homogeneous in composition, thus reducing the number of model free parameters to one only: the dust-to-ice ratio on the surface. Our derived rotation model is a short-axis model it is consistent both with the 1986 nucleus imaging data. with tile estimated non gravitatio nal force, and with the observed time variations of the nucleus production rates. The outgassing torque results in a significant variation of the angu lar momentum vector - for the assumed nucleus density of 0.5 g/cm(3).