Abstract: With the unknown angular velocity and angular acceleration of the noncooperative target, it is challenging to design the attitude control of onorbit autonomous servicing (OOAS) for noncooperative target tracking. The nonlinear observer is designed to obtain the states of the noncooperative target. Based on the nonlinear observer, the attitude tracking controller is designed. Moreover, the stability of the closedloop system is proved. The methods are verified by using computer simulations.

Key words: noncooperative target, attitude tracking control, nonlinear observer, closedloop stability