In this work the extent to which orbit and attitude sensors may cross-support each other in a joint processing to reduce estimation errors of the relative orbital and attitude dynamics is investigated. In order to do this, an engineering dynamic model taking into account the coupling effects between orbit and attitude dynamics is exploited for estimation purposes. A simple yet common configuration of two spacecraft in an along-track formation flying in low Earth Orbit (LEO) is used as case study, where the atmospheric drag perturbation constitutes the source of coupling. An extended Kalman Filter considering the dynamic coupling between orbital and attitude dynamics is used to estimate the absolute and relative dynamics of the system. It is shown that the coupling leads to higher accuracy estimation results.