Spinning spacecraft attitude control via the environmental magnetic field.

This paper presents a study of the attitude control of spinning satellites in circular earth orbits by means of a single, onboard, current-carrying coil. The interaction between the controlled current and the earth's magnetic field produces the control torques required to precess the spin axis. A new feedback control law, including provisions for active magnetic nutation damping, is presented; the general feasibility of magnetic control for spinning vehicles is demonstrated by verifying that the control law is applicable (i.e., produces asymptotic stability in-the-large) for any desired spin-axis orientation. Accurate estimates of the performance of this control system are obtained by using a combination of Krylov-Bogoli ubov averaging and other heuristic techniques. These estimates place in evidence the influence of control system parameters, orbital parameters, and the desired spin-axis orientation upon system performance. The usefulness of this magnetic control law is indicated by general discussions of its mechanization.