Launched in March 2004 Rosetta's main objective is to orbit the Comet 67 P/Churyumov-Gerasimenko and even send a lander on its surface in 2014. On its way Rosetta has already passed asteroid Steins in 2008. These rendez-vous with asteroids are always very interesting for the scientific communauty who has the possibility to cross check theories with real data sent from space.
The close pass with Lutetia - within 3200 kms of the space rock - will allow around two hours of good imaging with first pictures expected later Saturday.