Relative position and attitude estimation for Inner-Formation Gravity Measurement Satellite System

Inner-Formation Gravity Measurement Satellite System (IFGMSS) is used to map the gravity field of the Earth. The IFGMSS consists of two satellites, in which one is the inner satellite; the other is the outer satellite. The inner satellite flies in the cavity of the outer satellite and is affected only by the Earth gravitational force. To detect the relative position of the inner satellite in real time, it has suggested an optical scheme to observe the mass center of the inner satellite. This paper describes a modified Unscented Kalman Filter (UKF) algorithm to estimate the relative motion between inner satellite and outer satellite. An integrated relative rotational and translational dynamics is constructed when the outer satellite tracking the inner satellite. Particular attention is given to the nonlinearity due to the coupled dynamics between the translational and rotational motion equations. Simulation results are presented in order to validate the proposed estimation scheme with and without control. Three different scenarios are simulated to validate the effectiveness of this approach. And the results showed that the estimation accuracy is affected by the nonlinearity of the dynamics. Through analysis, the proposed estimation algorithm is able to provide high accurate relative attitude and position estimation for the IFGMSS.