Impact-Rebound Momentum Excitation Based Inertial Parameters and State Estimation of Defunct Space Object

Abstract

Obtaining the inertia tensors of defunct space objects is essential in on-orbit missions. When the inertia tensor of the space object is non-diagonal, the problem becomes challenging. In this case, the system does not have enough information to estimate the six independent parameters of the inertia tensor. In this paper, the problem of estimating the inertial parameters of a defunct space object with non-diagonal inertia tensor is studied. An excitation method of ejecting an impact ball from the tracking spacecraft to the object is proposed to estimate the complete inertial parameters of the object. The impact ball rebounds after colliding with the object and crashes into the atmosphere finally. After the collision, the angular momentum of the space object changes. The change is used to construct the estimation model. This paper designs an estimation model which consists of two Unscented Kalman-based estimators to estimate the inertial parameters and the motion states of the object. The observability of the estimators is proved through the observability theorem of nonlinear systems. Numerical simulations show that the estimation model is effective in estimating the complete inertial parameters of defunct objects, as well as reducing the measurement errors of the position and attitude of the object.