SPACECRAFT REORIENTATION CONTROL ANALYSIS FOR TOUCH-AND-GO COMET SAMPLE RETURN

This article revisits the large-angle spacecraft reorientation attitude control problem from the perspective of maximizing the disturbance rejection capacity with respect to the maneuver time. To ensure stable reorientation, a smooth attitude trajectory command is profiled to match the estimated initial state and the desired final state of the spacecraft; with command following provided by state-feedback control. In this setting, the closed-loop tracking error dynamics are shown to belong to a class of nonlinear systems consisting of nominal linear time-varying system plus a set of structured time-varying nonlinearities which can be constructed to vanish at the origin under certain conditions. This property allows the concept of eigenvalue extension of linear time-varying systems to be applied in the interpretation of the results. An example problem, motivated by a comet sample return mission prototype, is given to demonstrate the sensitivity of the disturbance rejection capacity to maneuver time. The results reinforce the notion that large-angle spacecraft reorientation should place a premium on finesse (i.e., smooth, bounded motion), rather than speed (i.e., minimum time control).