Attitude control system for three-axis stabilized satellite in near-equatorial orbit

Claim 1

A roll/yaw attitude control system for a three-axis stabilized satellite in Equatorial or near-Equatorial orbit, said satellite having roll, yaw and pitch axes, said attitude control system comprising: a sensor device for sensing the attitude of said satellite in roll, yaw and pitch, said sensor device comprising a terrestrial sensor mounted on said satellite adapted to detect the Earth; and a stellar sensor mounted adjacent said terrestrial sensor and adapted to detect the Pole Star, said terrestrial sensor and said stellar sensor further sensing the roll and yaw positions of said satellite; an actuator device mounted to said satellite, said actuator device comprising; a kinetic moment system having a kinetic moment with a non-null value at all times, said kinetic moment having a dominant component along said pitch axis; a magnetic dipole generator system disposed at least approximately parallel to a roll/yaw plane defined by a plane containing said roll and yaw axes; and a set of backup actuators; a processor circuit connected between said attitude sensing device and said actuator device, said processor circuit comprising; a short-term roll/yaw control loop comprising a state estimator for estimating, on the basis of measurements by said terrestrial and stellar sensors, roll and yaw attitude angles and angular speed value; and a preselected gain controller for determining, from said estimated attitude angles and angular speed value, set point signals fed by distribution logic to at least one of said kinetic moment system, said magnetic dipole generator system, and said set of backup actuators; and a long-term roll/yaw control loop comprising a state estimator for estimating, on the basis of measurements by said terrestrial and stellar sensors, roll angles, yaw angles and components along the roll and yaw axes of exterior disturbing torques; a controller for determining, via distribution logic, a dipole signal to be applied to said magnetic dipole generator system; and a backup system in parallel with said controller adapted to send control signals to said set of backup actuators.