Relative attitude and position estimation for a tumbling spacecraft

This paper presents a novel relative attitude and position estimation approach for a tumbling spacecraft. It is assumed that the tumbling chief spacecraft is in failure or out of control and there is no a priori rotation rate information. The Eulerʹs rotational dynamics is used to propagate the chief angular velocity, and the unknown inertia parameter circumstance is also considered. The integrated sensor suit comprises a rate-integrating gyro and a vision-based navigation system on the deputy spacecraft. Two relative quaternions that map the chief Local Vertical Local Horizontal (LVLH) frame to the deputy and chief body frames are involved to construct the line-of-sight observations. Therefore, the assumption that the chief body frame coincides with its LVLH frame in the traditional algorithm can be released. The general relative equations of motion for eccentric orbits are used to describe the positional dynamics. An extended Kalman filter is derived to estimate the relative quaternions, relative position and velocity, deputy gyro bias, as well as chief angular velocity and inertia ratios. Simulation results verify the validity and feasibility of the proposed algorithm.