Tether attachment point stabilization of noncooperative debris captured by a tethered space system

Before an active debris removal process is carried out, the attitude stabilization of the debris needs to be executed to ensure security. Fortunately, for the tethered system, a full despun is not always necessary; a stabilization of the motion of the tether attachment point is usually sufficient. This paper discusses the way to stabilize the motion of the tether attachment point of a captured noncooperative space debris without any auxiliary mechanisms. The debris possesses unknown inertia information and states after capture, while the tether tension is the only input to manipulate its attitude. The direction and value of the tension is regulated based on the continuous dissipation of the rotational energy of the debris. Moreover, the range of the tether direction is restricted to a small conical region, in order to reduce the tether libration motion and the orbit maneuver of the main satellite. The motion of the tether attachment point is desired to be observed instead of measuring the attitude motion of the debris in the feedback loop, which might be easier to attain in practical applications. Numerical simulations are carried out to validate the effectiveness of the control method and to check the performance of the controller with different parameters.]