A state estimation scheme with minimal sensor configuration for three-body tethered satellite formations

Tethered satellite formations in space have attracted widespread attention in recent years, as they can provide an excellent large-scale, self-stabilized space platform. At present, most studies on tethered satellite formation systems focus on dynamics, control deployment and stability analysis, and they all assume that the state information of the system is given or easily measured. However, it is not trivial to obtain accurate state measurements of tethered satellite formations in space, especially without using high-cost sensors. In this paper, we present a filter-based state estimation scheme with minimum sensor configuration for three-body tethered satellite formation. The satellite-to-satellite ranges and absolute attitude angles of tethered formation can be accurately estimated by fusing only the measurements of three gyroscopes and three tether releasing mechanisms. Particularly, the absolute attitude angles are obtained even without using any sensors that can measure absolute information. The feasibility of the proposed scheme is theoretically proven via the observability analysis of nonlinear systems, and the performance of the scheme is demonstrated through extensive simulations. This method can be readily extended to the state estimation process of other tethered formations in space.