This short animation explains the relative sizes of the Rosetta spacecraft and comet 67P/Churyumov–Gerasimenko.
Rosetta is 32 m from tip to tip of the solar wings. Assuming the comet measures about 4 km across, that’s 125 times the width of Rosetta.
Unlike typical artist’s impressions, this image is scaled to convey the vast difference in size between Rosetta and the comet, even when the spacecraft is in a close 10 km orbit, as depicted here.
Rosetta arrives at the comet at an altitude of 100 km in the first week of August and will move progressively closer over the following two months, with the intention to orbit at an altitude of just 10 km, depending on the comet’s activity. For Philae’s deployment in November, Rosetta will come to within a few kilometers of the surface.