On-line mass estimation for a tethered space debris during post-capture and retrieval

This paper presents a new methodology for on-line mass estimation for massive space debris captured by a tethered system. Mass estimation of unknown debris is critical for subsequent tasks in the space debris remediation mission, in particular, for debris retrieval and deorbiting. In the proposed algorithm, the base satellite (chaser) and space debris (target) are modeled as point masses, the latter with unknown mass. Then, the mass estimation problem is formulated and solved in two phases. First, a coarse estimate of the target mass is obtained during the post-capture phase, while the tethered system is experiencing in-plane and out-of-plane oscillations. Then, with a proper tension control scheme and the coarse estimate used as an initial guess, the debris is retrieved smoothly and a precise mass estimate is achieved.