Attitude acquisition maneuver for a bias momentum spacecraft

Abstract

An orientation maneuver for a bias momentum stabilized spacecraft is carried out on a spacecraft initially spinning about a minimum moment of inertia axis. With the spacecraft spinning about that axis, it is precessed until the angular momentum vector points to the south along the orbit normal. The spin rate is then reduced until the angular momentum remaining in the spacecraft is substantially equal to the nominal angular momentum of the momentum wheel in an in-orbit operation. The momentum wheel is then energized and gradually spun up until it contains its nominal angular momentum. As the wheel accelerates, the angular momentum will be redistributed between the wheel and the body, with the total system angular momentum remaining constant. When the wheel has reached its final speed, the spacecraft will have re-oriented itself such that the body of the spacecraft is spinning about the positive pitch axis, coning about the angular momentum vector in a nutational motion. Using thrustors on-board the spacecraft, the pitch rate of the body is then reduced to a value sufficiently low to permit earth capture in the earth sensor's field of view. As a result of pitch rate reduction, the total system angular momentum becomes substantially equal to the wheel momentum vector. Nutation is damped by either passive or active damper on the spacecraft.

Dependencies are inferred from the claim text.