This thesis studies the dynamics of Phobos, Mars’ bigger moon, as part of the preparation for coming Phobos-bound missions. Existing observations have not been able to properly constrain the interior of the two Martian moons in general and Phobos in particular, being therefore inconclusive about their origin and formation. Thus, on-site measurements with the aid of Phobos landers is planned for the near future. In particular, this thesis focuses on the couplings between Phobos’ translational and rotational dynamics. Their effect in state propagation is quantitatively described and their impact on parameter estimation is assessed. For this, the trajectory of Phobos has been computed by propagating a given initial state in two ways. A first manner integrates Phobos’ translational and rotational equations of motion simultaneously; a second manner integrates Phobos’ translational equations of motion alone, and assumes that Phobos is in a fully-locked configuration with a once-per-orbit longitudinal libration. A first part of the results is an analysis of the differences between these two solutions, in terms of position and orientation. A second part of the solution is the analysis of least-squares estimations, by which the uncoupled model is fit to observations taken from the coupled trajectory. In doing so, the best way in which the uncoupled model can imitate the coupled model by changing some dynamical parameters is found.
The results are analyzed in terms of estimation post-fit residuals - the final differences between the coupled and uncoupled solutions - and differences between the parameter estimates and the true parameters. These parameters comprise mostly the once-per-orbit libration amplitude and the quadrupole gravity field, all of which provide information of Phobos’ interior. The outcome of this thesis is a detailed and quantitative study of the extent to which an uncoupled model can imitate a coupled model and how the differences generated by couplings are absorbed into modifications of estimated parameters to keep the to trajectories as similar as possible. This provides a preliminary approximation of the type of true errors that state-of-the-art estimations contained in their fitted solutions.