Patent ID: 6285928
Filing Date: 2001-09-04
Classification: B64G

Abstract:
A control system for maintaining the attitude of a satellite in alignment with its mission attitude comprising:a ground station control computer constructed to transmit satellite orbital data and mission attitude data to a satellite onboard computer;an earth sensor array on said satellite for sensing satellite position data relative to the earth;a sun sensor array on said satellite for sensing satellite position data relative to the sun;a three axis gyroscope system on said satellite for sensing satellite orbital position about a three axis coordinate system;a reaction wheel assembly having a reference axis, said wheel assembly including four wheels, each of said wheels being mounted for rotation on a spin axis, said spin axes arranged in a configuration, wherein at least three of said spin axes are oblique to said reference axis;an onboard satellite control computer constructed to receive and store input data comprising said orbital data and mission attitude data from the ground station computer and said sensed data from said onboard sensors, said onboard computer further comprising:an estimator module constructed to store orbital attitude modeling algorithms and to process the orbital data and mission attitude data, the sensed earth and sun position data, and the gyroscope attitude data and is further constructed to estimate the current satellite attitude based on said data inputs;an adjustment module constructed to compare the mission attitude to the estimated current attitude and to calculate an attitude error; said adjustment module further calculating an attitude adjustment capable of reducing the error to substantially zero; anda transformation module having algorithms stored therein for converting said attitude adjustment to an attitude command for actuating said reaction wheel assembly to adjust the attitude of the satellite according to the attitude adjustment.