System and method for controlling the attitude of a space craft

Abstract

A system ( ) for adjusting the orientation of a spacecraft adapted for use with a satellite ( ). The system ( ) includes a first control circuit ( ) for canceling any momentum of the spacecraft via a counter-rotating spacecraft bus ( ). A second controller ( ) orients the spacecraft via the application of internal spacecraft forces. In a specific embodiment, the spacecraft bus ( ) serves a dual use as storage section and includes a mass ( ) having a moment of inertia on the same order as the moment of inertia of the satellite ( ). The satellite ( ) includes a bus section ( ) and a payload section ( ). The mass ( ) includes the bus section ( ). The first control circuit ( ) runs software to selectively spin the mass ( ) to cancel the momentum of the satellite ( ). The software computes an actuator control signal, via a computer ( ), that drives a first actuator ( ) that spins the mass ( ). The first control circuit ( ) further includes a circuit for determining the inertial angular rate of the satellite ( ) that includes a gyroscope sensor package ( ) in communication with the computer ( ). The gyroscope sensor package ( ) provides a rate signal to the computer ( ) that is representative of the momentum of the satellite ( ). The computer ( ) runs software for generating the actuator control signal in response to the receipt of the rate signal from the gyroscope sensor package ( ). The second controller ( ) includes a first reaction wheel ( ) having an axis of rotation ( ) approximately perpendicular to an axis of rotation ( ) of a second reaction wheel ( ). The first and second reaction wheels ( ) are rigidly mounted to the spacecraft bus ( ) and are free to spin about their respective axis. The first and second reaction wheels ( ) are selectively spun via first and second actuators ( ), respectively, in response to the receipt of first and second steering control signals, respectively.