Identification of parameters for tethered satellite system to emulate net-captured debris towing

Net-based debris capture systems have a high potential for success in Active Debris Removal (ADR) missions. Simulation is an important tool in the analysis of the dynamics of nets, before experiments and actual missions are put in place. However, due to the large number of degrees of freedom required to model the dynamics of a net, in addition to nonlinearities, high-fidelity net-based ADR simulations are typically very computationally costly. This work focuses on the post-capture phase of a net-based ADR mission and aims to identify parameters of a lower-order model of the towed debris system such that it best matches the high-fidelity simulations with a full net. A model of a tethered satellite system with four sub-tethers is developed, and two optimization problems are formulated – minimizing the difference in dynamical quantities of interest – to perform the parameter identification task. The proposed system identification framework is first validated on a benchmark sub-tether model with known parameters, and then employed to minimize the difference in dynamics between the full-net and sub-tether debris towing simulations. The performances of the optimized solutions obtained from two proposed cost functions are compared both qualitatively and quantitatively. Overall, the proposed lower-order modeling and parameter identification framework demonstrate satisfactory performance in approximating the dynamics of the high-fidelity system.