From BBC News:
Nasa’s Deep Impact spacecraft may have missed its chance to see the crater made in Comet Tempel 1 because of the large plume of material kicked out. Seeing the crater was a key objective of the mission – scientists hoped the impact depression would tell them more about the structure of the comet. But the team can use indirect methods to estimate the crater’s dimensions. A 370kg “impactor” released into Tempel 1’s path by the flyby spacecraft crashed into the comet on Monday.
More here.