This paper is concerned with large angle precession of earth-pointing bias momentum satellites in circular orbits and small angle precession in eccentric orbits. In the first part, ideal torque requirements are determined for precessing a wheel momentum vector by a large yaw angle, maintaining the earth pointing. It is then shown that a quasi-quarter-orbit magnetic precession is more easily feasible if once-per-orbit rotation of the spacecraft for earth-pointing is halted before commencing the precession. General relationships are developed to size the pitch dipole for a specified precession angle in a given number of orbits, using a tilted dipole model of the rotating geomagnetic field. The formulae involve true anomalies, not necessarily quarter orbit apart, at which the pitch dipole reverses its signs. The second part of the paper considers elliptic orbits. A pitch dipole sizing equation is developed first for a small angle open-loop roll/yaw magnetic precession. A closed-loop bang-bang precession scheme is presented next, working in concert with nutation damping via a roll/pitch product-of-inertia. The sizing equations and the quasi-quarter-orbit apart true anomalies for sign reversals of the pitch dipole apply to spin-stabilized satellites as well, for they are generalization of the related existing results. The literal relationship between the desired nutation damping coefficient (or time constant), roll/pitch product-of-inertia, and rate gain of the proportional-plus-integral-plus-derivative pitch wheel controller is helpful in determining the required mass distribution of the spacecraft and the pitch controller bandwidth.
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