Creating a Generalized Empirical Model of the H2O Coma Distribution in Comets Based on ROSINA/DFMS Measurements and AMPS-DSMC Simulations for comet 67P/Churyumov-Gerasimenko

Rosetta's observations of comet 67P/Churyumov-Gerasimenko have given us an unprecedented, up close view of the water coma as it evolves during the 67P's passage through the inner solar system. Using both AMPS DSMC (Adaptive Mesh Particle Simulator Direct Simulation Monte Carlo) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) data, we have created empirical models of the H2O, CO2, CO, and O2 coma distributions specifically for 67P. These empirical models are functions of the position in the coma as well as the heliocentric distance of the comet and are high enough quality to be used for de-trending spacecraft motion from the observed Rosetta data. In this work, we will extend the water coma empirical model to other comets. This is possible for the water distribution because the behavior of water at 67P is mostly governed by solar illumination and is not largely driven by North-South or dual-lobe compositional asymmetries. CO2 and CO, on the other hand, have distributions that are clearly specific to the shape and orientation of 67P specifically and therefore it is not clear how to implement a general empirical model for those two species. The empirical model we present will include parameterizations that take into account the longitudinal spreading of the distribution due to collisions, or the lack thereof, as a function of production rate.