Abstract: For an antenna on a satellite in an inclined orbit about the Earth, cross-track motion resulting from the rotation of the Earth can be reduced in antenna coordinates by yawing and/or rolling the antenna (preferably by yawing and/or rolling the entire satellite, for example, by using a reaction wheel system) by an appropriate angle, which varies throughout the orbit.

Abstract: Spacecraft maneuvers (e.g., orbit transferring, stationkeeping and attitude controlling) of a first spacecraft are realized with conventional force and torque generators (e.g., thrusters and momentum wheels). Spacecraft maneuvers of a second spacecraft are realized through magnetic interaction between the first and second spacecraft. In particular, a magnetic moment vector m.sub.1 of a magnetic system of the first spacecraft and a magnetic moment vector m.sub.2 of a magnetic system of the second spacecraft are adjusted to apply selected force vectors and torque vectors to the first and second spacecraft.

Abstract: An improved encoder alignment system is disclosed which provides an indication of the extent of misalignment and a measure of the rate at which the misalignment may be changing. The invention is adapted for use with a conventional encoder which provides a digital coarse word having at least significant bit and a digital fine word having a least significant bit and a most significant bit. The invention generates the exclusive or of the least significant bit of the coarse digital signal and the least significant bit of the fine digital signal to provide a first signal. The invention then generates the exclusive or of the first signal and the complement of the most significant bit of the fine digital signal to provide an output signal which represents the misalignment of the encoder.