Abstract: Systems, apparatuses, methods, and software are described herein that provide enhanced logistical control over spacecraft. This logistical control can include attitude adjustment and desaturation of reaction wheels. In one example, a method of operating a spacecraft includes providing propellant in two or more propellant tanks for use by at least a thruster of the spacecraft. During application of a force on the spacecraft, the method includes transferring propellant from at least a first propellant tank to at least a second propellant tank to alter a center of mass of the spacecraft.

Abstract: The satellite communication system has a ground station and multiple remote terminal units (RTUs). The RTUs are designed to infrequently transmit relatively short duration messages, and to repeatedly transmit the same message, so that it is received by a sweeping high gain satellite antenna. To minimize costs, the system is designed to allow the use of RTUs that use a fixed modulation scheme. Because the transmissions are infrequent and short, the loss of messages due to collisions is unlikely. As a further optimization, the RTUs have CDMA transmitters that each use the same CDMA code, and the ground station has multiple CDMA correlators using the same CDMA code. By using the same CDMA code, the loss of messages due to collisions is further reduced. For transmitting to the RTUs, the ground station has multiple CDMA modulators, each using a second CDMA code that is preferrably orthogonal to the first CDMA code.

Abstract: The satellite communications system of this invention provides high-gain coverage to a wide geographic area with a minimum number of satellites. The satellites each include a high-gain antenna that periodically sweeps the satellite's service area to receive the messages from remote terminal units within the entire service area. In order to provide high gain, the antenna is designed to have a narrow beamwidth in at least one dimension. To cover the entire area, the antenna's field of view is swept across the entire service area. In the preferred embodiment, the antenna's field of view is essentially rectilinear, having a narrow beamwidth in one dimension and a beamwidth that extends across the entire service area in the other dimension, such that the sweeping effect is akin to that of a common push-broom. Because of the high gain of the satellite antenna, communications via the satellite can be accomplished using a low-gain wide-beamwidth antenna at the remote terminal unit.