Attitude stability of satellites subjected to gravity gradient and aerodynamic torques

Abstract

The effect of aerodynamic and gravitational torques on the attitude stability of orbiting satellites is investigated. The satellite is assumed to be a rigid body on a circular orbit. No restrictions are made relative to mass and shape properties. Liapunov's direct method is applied in case of conservative aerodynamic torques to investigate the stability of the satellite's equilibrium orientations relative to an orbiting reference frame. At least one stable equilibrium exists if the aerodynamic torque is conservative not only in the vicinity of the equilibrium but also for arbitrary orientations of the satellite. This property is determined by the shape of the satellite and the location of the center of mass. The stability investigation by linearized analysis shows that the equilibrium orientations are in general unstable if the aerodynamic torque is nonconservative.