Properties of the dust cloud caused by the Deep Impact experiment

Byline: L. Jorda (a), P. Lamy (a), G. Faury (a), H.U. Keller (b), S. Hviid (b), M. Kuppers (b), D. Koschny (c), J. Lecacheux (d), P. Gutierrez (e), L.M. Lara (e) Keywords: Comets; Comets; dust; Comet Tempel-1; Comets, composition; Image processing Abstract: We present an analysis of the observations of the Deep Impact event performed by the OSIRIS narrow angle camera aboard the Rosetta spacecraft over two weeks, in an effort to characterize the cometary dust grains ejected from the nucleus of Comet 9P/Tempel 1. We adopt a Monte Carlo approach to generate calibrated synthetic images, and a linear combination of them is fitted to the calibrated images so as to determine the physical parameters of the dust cloud. Our model considers spherical olivine particles with a density of 3780 kgam.sup.-3. It incorporates constraints on the direction of the cone of emission coming from additional images obtained at Pic du Midi observatory, and constraints on the dust terminal velocities coming from the physics of the impact. We find that the slope of the differential dust size distribution of grains with radii Author Affiliation: (a) Laboratoire d'Astrophysique de Marseille, BP 8, 13376 Marseille Cedex 12, France (b) Max-Planck Institut fur Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany (c) Research and Scientific Support Department, ESTEC, 2200 AG Noordwijk, The Netherlands (d) Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon, France (e) Instituto de Astrofisica de Andalucia, CSIC, 18080 Granada, Spain Article History: Received 31 March 2006; Revised 19 September 2006