Spin and activity of comet 67P/Churyumov-Gerasimenko

Aims. In 2014 ESA's spacecraft Rosetta will reach its final target: comet 67P/Churyumov-Gerasimenko (67P). Although this comet has been studied in great detail over the past decade, there are still some uncertainties regarding the actual spin orientation and the distribution of active regions on the surface. We here give an overview of our current knowledge of these critical parameters based mainly on data acquired during the last orbit of the comet aims to deliver a review of what is our current knowledge of these critical parameters. Methods. We based our analysis on the modeling and interpretation of dust jets seen in the coma of 67P during the 2009 apparition. Results. The inversion of ground-based images leads to an estimate of the spin axis orientation (RA = 40 degrees +/- 10 degrees, Dec = 70 degrees +/- 10 degrees) and to the localization of the most prominent active areas on the surface of the nucleus. We can reproduce the activity with three active regions localized at -45 degrees, 0 degrees, and +60 degrees of latitude. We use these results to revisit the observations taken during the 2003 apparition and examine the changes in activity between then and now. Our model from 2009 is also valid for the 2003 data, which suggests that no significant change in spin orientation and active areas occurred from one perihelion passage to the next. Finally, we combine all the results to propose some predictions on the activity to be expected in 2015 during the comet exploration phase of the Rosetta mission.