Modeling of Morphology, Composition and Light Scattering Properties of Microscopic Individual Particles in Cometary Coma

Cometary dust environment modeling is an essential tool for the planning of the future operations and the data evaluation of Rosetta and other missions towards comets. Observational and laboratory data indicate that dust particles from comets have an irregular structure and are composed mainly by fine mixtures of organic and silicate components, but the real nature of cometary dust is still elusive. Here we present our investigation about the morphology , composition and light-scattering properties of individual dust particles in the comets coma. Fractal microscopic aggregates to simulate irregular particles and the Discrete-Dipole-Approximation theory to derive their scattering properties have been used. For the first time the behavior of extremely elongated particles (that form in microgravity aggregation experiments) has been investigated and compared with the scattering properties of more compact aggregates. Moreover, the results of the model can be applied to the Rosetta two cameras Osiris instrument to define an optimal observing strategy to investigate the nature of dust. A preliminary study of S/C optimal trajectories around the comet nucleus is here presented.