Outgassing-induced effects in the rotational state of comet 67P/Churyumov---Gerasimenko during the Rosetta mission
Résumé
The new target of the Rosetta mission is comet 67P/Churyumov Gerasimenko (hereafter 67P/C G). In order to support the planning of the mission, in particular the strategy during the mapping and landing phases, we have performed numerical simulations of the rotational evolution of a comet in the orbit of 67P/C G. In these simulations, the currently known observational constraints have been taken into account and a large set of initial conditions were considered. For most of the simulations, we observe that the sublimation-induced torques produce significant changes in the rotational parameters of a 67P/C G-like comet. Typical rates of change for the spin period from the rendezvous up to the end of the nominal mission range from 0.001 to 0.05hday depending on different circumstances as described in the text. At perihelion, rates of change of the orientation of the angular momentum vector amount to about 0.01 0.1degday. These simulations suggest that a specific strategy should be defined in order to monitor likely variations of the rotational parameters. As an example we show a possible optimized schedule for observations with the OSIRIS instrument to determine the rotational parameters of comet 67P/C G and their possible evolution.