Hughes Electronics Corporation

Salma Saeed

John F Yocum, Jr

John W Smay

A method, apparatus, article of manufacture, and a memory structure for controlling an attitude and a nutation of a spacecraft spinning about a first axis. The method comprises the steps of measuring a spacecraft attitude rate &ohgr; (t) about a second axis substantially orthogonal to the first axis; generating a rate correction value &agr;&ohgr; (t)/&lgr; , wherein &lgr; is an inertial nutation frequency of the spinning spacecraft, and &agr; is a proportionality factor; determining a spacecraft attitude angle &phgr; (t) about a third axis substantially orthogonal to the first axis and the second axis; generating an error signal e(t) as &phgr; (t)&plus;&agr;&ohgr; (t)/&lgr; ; and applying a torque to rotate the spacecraft along the second axis. The article of manufacture comprises a program storage device storing instructions implementing the instructions described above. The apparatus comprises an attitude rate sensor for measuring the spacecraft attitude rate &ohgr; (t) about a second axis substantially orthogonal to the first axis; means for measuring a spacecraft attitude angle &phgr; (t) about a third axis substantially orthogonal to the first axis; a processor, in communication with the attitude rate sensor, for generating an error signal e(t)&equals;&phgr; (t)&plus;&agr;&ohgr; (t)/&lgr; , wherein &lgr; is an inertial nutation frequency of the spinning spacecraft, and a is a proportionality factor; and a torquer for applying a torque to the spacecraft along the second axis in accordance with the generated error signal e(t).

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Santa Monica, CA, United States of America

Salma Saeed