Post-Capture Tethered-Debris Principal Moment of Inertia Estimation via Pinhole Camera Model with Occlusion

The post-capture control of tethered debris can be challenging due to its unresponsive and uncooperative nature. Often, control of debris may require knowledge of the moments of inertia, which are usually unknown. This study applies an Unscented Kalman Filter to estimate the attitude, angular rates, and principal moments of inertia of debris captured via a tether. The filter utilizes tension and pixel-coordinate measurements of various landmarks on the debris to achieve estimation. Due to the translational and rotational motion of the debris, landmarks can be occluded or exit the field of view of the camera. Different control profiles are applied to the chaser to investigate the effects of the tension in the tether and of the visibility of chosen landmarks. It is found that large tension in the tether does not provide more accurate estimates, but that prolonging transient tether behavior improves the accuracy and precision of moment of inertia estimates. It is further observed that lower tension magnitudes with longer visibility times of landmarks make estimation of the inertia parameters possible with fewer tracked landmarks.