Gravitational and Non-Gravitational Perturbation of the Rosetta Orbiter Near Comet Wirtanen

Based on simple analytical models, the gravitational and non- gravitational forces acting on the Rosetta spacecraft in the vicinity of a cometary nucleus are examined. Estimates of zonal, tesseral, and sectorial gravity field coefficients are derived from the analysis of an irregularly shaped sample body of con- stant density. The results are used to assess the capability for a determination of the cometary gravity field and cometary activity from radiometric tracking of the Rosetta orbiter. Out- flow of gas resulting from sublimation at the cometary surface is considered to be a major source of orbital perturbations even at large heliocentric distances