Abstract: The number of space debris is increasing rapidly which poses severe safety threats to the development of human space activities and in-orbit assets. Among the various proposed active debris removal techniques, tethered spacetug (TST) system has received increasing attention in recent years for its promising application prospects. Some defunct satellites keep specific orientations due to the damage of on-board components and attitude control systems. A dynamics and control study of tethered satellite system during the deorbiting phase was carried out for this special type of large space debris with non-cooperative characteristics. A mathematical model of TST system including two satellites modeled as rigid bodies was developed using Newton laws. According to the different attitude stabilization methods, the emphasis was the spin stabilized satellites and threeaxis stabilized satellites. The control laws of the tug and debris were designed respectively and the influence of the positions of attachment points on debris was also studied. The simulation results indicate that the system will stabilize near an equilibrium state after the countermeasure between the tug and debris.

Key words: space debris, tethered space-tug, quaternion, spin stabilized satellites, three-axis stabilized satellites