Abstract: A method and system for controlling a movable appendage on an aerospace vehicle independent from the position of the aerospace vehicle. First and second beacons containing actual position information for the movable appendage are tracked and acquired by first and second beacon tracking sites. The beacon tracking sites report the azimuth and elevation data relating to the position of the movable appendage to a processor where a correction command is determined based on an error calculated from the position data and a desired position. The correction command is communicated to the movable appendage so that appropriate correction to the desired position can be made.

Abstract: A spacecraft control electronics system provides multi-functionality to a spacecraft in a single electronics box. The system is subdivided into a plurality of modular electronic subunits. Each of the modular subunits plugs into a backplane in the electronics box and is positioned side-by-side. A serial data bus in the backplane of the box interconnects the modular subunits to each other. The data bus provides fully redundant, standard interfacing for the modular subunits. The plurality of electronic subunits provides spacecraft attitude determination, control, telemetry and command and data processing functions to the spacecraft as one unit. The electronics box connects to the spacecraft harness via external connectors. The spacecraft has a minimum number of harness connections as a result of the integrated functions in the spacecraft control electronics system. The control system applies selective internal redundancy in its subunits.

Abstract: A wireless intrasatellite communication system is disclosed. Satellite telemetry signals are multiplexed, converted into a digital data stream, and processed by an ASIC to form a multiplexed telemetry data stream. An infrared transceiver transmits the multiplexed telemetry data stream along an optical path to a designated interface that is associated with a remote command and telemetry unit. Telemetry signals are aggregated within a plurality of remote command and telemetry units and transmitted to a central command and telemetry unit via a high-speed digital bus. Command data issued from the central command and telemetry unit is distributed to a designated remote command and telemetry unit, and is routed to the appropriate user unit via the optical path. The user unit processes the command data and generates a responsive command signal output.

Abstract: Testing digital circuits presents problems because in operation not every "stuck at" fault is detected. The present invention provides linking circuits (12, 13, 14) and functional logic circuits (10, 11) which can be used together to provide a system which ceases operation when a "stuck at" fault occurs. Each linking circuit (12) receives a first input (16) from the output of a previous circuit (10) and a second input (15) from the output of a succeeding circuit (20), both in the vicinity of that linking circuit. The signal coding used is such that in normal operation both these inputs will be different in a predetermined way and if not it is an indication that a fault has occurred. Thus if the inputs do not exhibit the predetermined difference, the linking circuit does not pass its first input to its output. The effect is to stop the system from operating and leave it in a condition from which the location of the fault can be detected.