Book Description

The report investigates a means of controlling the attitude of a satellite in a circular orbit about the earth by the torque due to the interaction between the earth's magnetic field and the magnetic moments produced by currents in three orthogonal coils aboard the satellite. This system has the advantage over more conventional ones in that no mass is expended in the control process. It is designed to rotate the satellite about its longitudinal axis in a minimum amount of time while limiting the deviation of this axis from the local normal to the earth. The analysis is limited to the period during which the satellite's attitude is being changed by magnetically produced torques. When these torques are not applied, gravity gradient effects act as a restoring force to align the longitudinal axis with the local normal to the earth. The method is applicable to a satellite with symmetry such that the moment of inertia about its longitudinal axis is much smaller than those about body-fixed axes lying in a plane perpendicular to it and whose moments of inertia about axes in this plane are approximately equal. The model of the earth's magnetic field that is used is a dipole with its poles located at the observed geographical positions. The control system is developed to be applicable to the general type of satellite indicated above and to all orbits except those passing close to the magnetic poles. It is then applied to a particular satellite and type of orbit of interest to RADC. (Author).