Inertia parameter estimation for an noncooperative target captured by a space tethered system

A new method of on-line inertia parameter estimation is proposed for the retrieval/de-orbit of rigid noncooperative space debris which is captured by a tethered system. First, the non-dimensional equations of motion of the system are derived according to new dynamics model of the system where the base satellite and the noncooperative target satellite are modeled as two rigid bodies and the arbitrary attachment points of the tether system are offset from the centers of mass of the two bodies. Then, the attitude motions of target satellite and tether system during the post-capture phase are analyzed. Finally, the inertia parameters of noncooperative target satellite are eatimated by using a robust variable forgetting factor recursive least-squares algorithm under the condition that all the information of target is not communicated to the base spacecraft.