Characterization of Dust Particles Using Photopolarimetric Data: Example of Cometary Dust

We present an approach to constrain characteristics of an ensemble of dust/aerosol particles using integrated photopolarimetric data. We test the approach with one of the best-studied and most intriguing ensembles - cometary dust. We analyze available cometary photopolarimetric data to identify characteristic light-scattering properties typical for cometary dust. We review attempts to interpret these properties using theoretical and laboratory simulations of light scattering by cometary dust. Particular attention is given to the most successful models: (1) aggregates of submicron particles and (2) ensembles of multishaped polydisperse particles. We explore the capabilities of these two models to describe the light scattering by cometary dust. We demonstrate that the model of multishaped polydisperse particles cannot reproduce cometary photopolarimetric data by using a single set of dust characteristics; whereas, the aggregate model can. Our calculations allow for further constraint of the cometary dust properties as large aggregates of absorbing material that is consistent with general ideas about the origin of comets.