On its way to Comet 67P/Churyumov-Gerasimenko, Rosetta is targeting two asteroids for study: (2867) Steins, on 5 September 2008, and (21) Lutetia on 10 June 2010.
The Rosetta orbiter - spacecraft design
Rosetta resembles a large aluminium box whose dimensions are 2.8 x 2.1 x 2.0 metres. The scientific instruments are mounted on the 'top' of the box – the Payload Support Module – while the subsystems are on the 'base' or Bus Support Module.