Stabilization of the spacecraft in the solar orientation mode by electromagnetic attitude control system

We investigate solar orientation mode of an Earth artificial satellite. Satellite parameters are close to parameters of the spacecraft Bion M and Foton M-4. In this mode, the normal to the plane of satellite solar batteries is permanently directed on the Sun, the satellite longitudinal axis lies in the orbital plane, absolute angular rate of the satellite is practically equal to zero. The mode is stabilized by electromagnets interacting with the Earth magnetic field and the flywheel with constant gyrostatic moment directed along the satellite longitudinal axis. Such a moment can be created also by a system of reaction wheels. Constancy of gyrostatic moment means that such a system will be operated without saturation. The satellite attitude control is implemented by change of currents in the electromagnets. We investigate two control laws that reduce the satellite angular rate and stabilize the solar orientation mode. Measurements of a triaxial magnetometer and solar sensor need only to form these laws. Realization of the laws requires a few watts of electric power. We test the laws by the mathematical modeling the spacecraft attitude motion taking into account the gravitational and the aerodynamic torques acted upon the spacecraft, as well as the control torques produced by the electromagnetic system. As the results of modeling show, the investigated orientation mode provides very small residual accelerations onboard the satellite.