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

We demonstrate the possibility to stabilize the heavy spacecraft like Foton in the gravity gradient orientation mode by the electromagnetic attitude control system that uses three current-carrying coils as its actuators. The coils have mutually perpendicular axes. Electric currents in the coils produce the magnetic moment, which interacts with the Earth magnetic field and produce a torque acting upon the spacecraft. The spacecraft attitude control is implemented by change of the currents in the coils. We investigate a few control laws that reduce the spacecraft angular rate and stabilize the spacecraft gravity gradient orientation. Measurements of a triaxial magnetometer 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 results of modeling show, the investigated orientation mode provides very small residual accelerations onboard the spacecraft Foton.