One of my main scientific goals is to understand the formation and evolution of dust coma structures at all scales: from tiny filaments only visible close to the surface of the nucleus, to large structures extending tens of thousands of kilometers in the coma.
For this pupose I am developping a numerical model that can be used to :
invert physical parameters from observations of dust jets (from ground based observations or images acquired with the OSIRIS camera system),
simulate the evolution of dust coma structures and predict activity patterns during the Rosetta mission.
Movie generated by COSSIM (version 2.5.0): dust jets of comet 67P/C-G as they would be observed by the OSIRIS WAC camera on board Rosetta.
The software package is divided in three parts:
a set of MATLAB scripts perform the geometric inversion, linking a jet to a specific spot on the surface;
Pi-DSMC-MPS: a direct Monte-Carlo simulation of the gas expansion above the active areas, developped by M. Rose;
COSSIM (COma Structures SIMulator): the final tool that inserts dust grains in the gas flow, propagate their trajectories, and converts the simulated jets to images which can be compared with ground-based or in-situ observations (see movie above for an example).
COSSIM tries to be as complete as possible and takes into account the real topography, outgassing rate, temperature of the surface, illumination conditions, presence of different ices and dust. We are working now on adding dust fragmentation and grain sublimation to the model.
Typical small jets seen close to a nucleus surface (left: 9P/Tempel 1 image; right: Pi-DSMC-MPS model)
Medium scale jets of 9P/Tempel 1 (left: real image; right: COSSIM model for a generic comet)
Large scale jets seen in enhanced ground based observations (left: 81P/Wild 2 image; right: COSSIM model)
Large scale jets seen in enhanced ground based observations (left: 9P/C-G image; right: COSSIM model)