Hubble measured the size, shape and rotational period of the Rosetta mission's backup target, comet 67P/Churyumov-Gerasimenko (67P/C-G). The telescope’s observations from March 2003 revealed that the comet is approximately five-by-three kilometres, and shaped like a rugby ball on which it is possible to land. ESA Mission scientists needed to know the exact size of the solid nucleus to adapt the mission to the comet’s gravity.
This photo shows 3D models of comet 67P/C-G's nucleus: pole (top right), side (bottom left), and end view (bottom right).