Abstract: A method of simultaneously controlling East/West and North/South positioning and unloading momentum of a spacecraft while orbiting an object. The spacecraft has a thruster array and a momentum accumulator. The method entails moving said spacecraft towards a node of the orbit. At a predetermined position on the orbit, separate from the node, a thruster of the thruster array is fired so as to control the orbital position of the spacecraft. While the thruster is being fired, momentum is dumped from the momentum accumulator at the predetermined position so that any loss in control in the attitude of the spacecraft is reduced.

Abstract: A spacecraft traveling in a volume of space receiving radiation from a radiation source and having a spacecraft body having a first axis of symmetry, X, a second axis of symmetry, Y, and a third axis of symmetry, Z. The spacecraft body rotates about a rotation axis, T, which defines a nonzero angle of inclination .lambda. relative to the Z axis. A radiation receiving element is rotatably attached to the spacecraft body along an axis, S. A control system is employed on the spacecraft for rotating the spacecraft body about the rotation axis T by an angular amount .gamma. and rotating the radiation receiving element by an amount so that the radiation receiving element is normal to the radiation source.

Abstract: A spacecraft with a spacecraft body having a first axis of symmetry, X, a second axis of symmetry, Y, and a third axis of symmetry, Z. The spacecraft has four thrusters. A control system is provided on the spacecraft which is in electrical contact with the first, second, third and fourth thrusters and which controls the activation and deactivation of the first, second, third and fourth thrusters so that the attitude and orbital velocity of the spacecraft can be controlled only by the first, second, third and fourth thrusters.