Dust Evolution of Comet 9P/Tempel 1

We present wide-field g, r, and i-band images of comet 9P/Tempel 1, target of the Deep Impact mission, taken with the MegaCam CCD (FOV 1° ×1°) on the {3.6-m} Canada-France-Hawaii Telescope on Mauna Kea. Our observations on UT July 3-6, 2005, covered the night prior to impact to ensure that we have data for the pre-impact dust environment. The two nights following impact allowed us to monitor the inner coma for changes in grain size properties as a result of the impact. We created a deep composite image (from three hours of observing time) for each night. Our morphological studies can establish the pattern of dust emission from the nucleus, which is determined by the surface distribution of discrete sources of dust on the rotating nucleus and their temporal evolution. The scientific questions we address are: How does post-impact dust differ from pre-impact dust? Is there any compositional difference between surface and subsurface grains? Does surface mantling change this? From the relative photometry we observed that some of the impact ejecta leaves our smallest aperture within the first hour after the impact. The light curves through different apertures implies that the ejecta was traveling roughly 200 ms^-1 projected on the sky. Fifty hours after the impact, the core of the comet was within a few tenths of a magnitude back to its pre-impact brightness. Also by our last night the morphology of the coma had begun to return to its pre-impact shape.