In this paper, the problem of estimating a contactwrench at the end-effector for a space robot is addressed. Tothis aim, a generalized force observer based on a base-jointsdynamics is first reviewed. Then, a different formulation isproposed, which is based on a centroidal-joints dynamics. Theproposed observer features interesting decoupling propertiesfrom the base linear velocity that lead to a more practicaland better-performing estimation when limitations in real spacescenarios are considered. The two observers are comparedand the advantage of the proposed one is shown through asimulation example featuring a free-floating robot composed ofa 7 degrees-of-freedom (DOF) arm mounted on a 6DOF movingbase
