Abstract: A series of tuning brackets are mounted on the microwave waveguide manifold at positions between the input waveguide/filter couplings. These brackets constrain the manifold and are constructed with adjustment screws extending through the brackets and mechanically connected to the manifold. The movement of the adjustment screw will tend to deform the manifold dimensions resulting in a fine adjustment of the wavelength (&lgr;) of the multiplexer.

Abstract: A method for operating a spacecraft comprising the steps of placing the spacecraft in a first orbit, changing orbital altitude of the spacecraft to transfer the spacecraft from the first orbit to a second orbit, changing an orbital plane of the spacecraft from an initial orbital plane to a different orbital plane, and changing orbital altitudes of the spacecraft to return to the spacecraft from the second orbit to the first orbit. The second orbit is at a different altitude than the first orbit of the spacecraft. The orbital altitude change placing the spacecraft in the second orbit and the orbital plane change are performed at substantially the same time.

Abstract: Systems and methods that limit the effects of actuator saturation to certain body axes of a spacecraft. A plurality of actuators, or momentum wheels, disposed on the spacecraft are oriented non-parallel to x, y, and z axes of the spacecraft. The plurality of actuators each produce torque that is applied to the spacecraft. Outputs of the plurality of actuators or momentum wheels are processed to control the respective actuators or momentum wheels to manage actuator saturation so that saturation does not produce attitude errors about one or more predetermined axes of the spacecraft.

Abstract: A satellite communication system includes at least one spacecraft in geosynchronous orbit for providing a plurality of beams on the surface of the earth, and a plurality of ground stations individual ones of which are located in one of the beams for transmitting uplink signals to the spacecraft. The spacecraft has a plurality of receivers for receiving a plurality of the uplinked signals from ground stations, a frequency translator for translating the received uplink signals to a transmission frequency of a plurality of downlink signals, and a plurality of transmitters for transmitting the plurality of downlink signals within the same beams as the corresponding uplink signals. Each transmitter includes a combiner for combining together a plurality of frequency translated signals and a power amplifier, such as a TWTA, for amplifying the combined plurality of frequency translated signals.

Abstract: A control system for providing attitude control in spacecraft. The control system comprising a primary attitude reference system, a secondary attitude reference system, and a hyper-complex number differencing system. The hyper-complex number differencing system is connectable to the primary attitude reference system and the secondary attitude reference system.

Abstract: Apparatus and methods for pointing a non-deployable or deployable appendage disposed on a spacecraft. The appendage is secured to a backup structure comprising a plurality of beams. A plurality of control beams are secured to the backup structure. A plurality of deformation control elements, such as piezoelectric elements, for example, are secured to selected surfaces of the plurality of control beams. The deformation control elements are connected to a control source, such as a voltage control source, for example. Selected deformation control elements are activated to deform the associated control beams to point the deployable appendage in a desired direction.

Abstract: A space vehicle includes an attachment system for attaching the vehicle to another space vehicle, a memory for storing data concerning the status of the other space vehicle and threats experienced by the other space vehicle, and a transmission system for transmitting data stored in the memory to a planet or a different space vehicle. An ejection system enables the secondary vehicle to be ejected from the primary vehicle when predetermined criteria concerning the status data or the threat data are met. A spin system causes the secondary vehicle to be spin stabilized when ejected from the primary vehicle. When the secondary vehicle is ejected, the nature of the threat or status of the primary vehicle can be determined.

Abstract: An easily implementable satellite constellation stationkeeping algorithm for maintaining the relative positioning among satellites of a low earth orbit constellation with minimal maneuvering while maintaining the constellation altitude over the effects of atmospheric drag. The satellite constellation stationkeeping algorithm may be implemented as a system or method that uses atmospheric drag perturbations to extend the stationkeeping cycle of the satellites in the low earth orbit constellation while simplifying the implementation algorithm and performing minimal maneuvers. In an exemplary satellite constellation stationkeeping algorithm, a plurality of satellites or a ground station are configured with a controller that implements an absolute altitude control algorithm. The plurality of satellites are launched into a respective plurality of slots of a low earth orbit.

Abstract: An antenna system and improved antenna support structure that is preferably used on a spacecraft. An exemplary antenna system comprises an antenna dish, an antenna positioning mechanism, and the present antenna support structure coupled between the antenna dish and antenna positioning mechanism. The antenna support structure comprises a composite ring attached to a rear surface of the antenna dish and a boom structure coupled to the composite ring and to the antenna positioning mechanism that comprises a plurality of tubular fingers that interconnect the composite ring and the antenna positioning mechanism. The boom structure may further comprise one or more lateral supports that interconnect the plurality of tubular fingers. The composite ring is preferably disposed in a plane containing the center of gravity of the antenna dish. The composite ring, tubular fingers, and lateral supports preferably comprise graphite fibers.

Abstract: An antenna deployment system for use in storing and deploying three antennas that are located on the same side of a spacecraft or other fixed body. The three antennas are nested and are stacked in a stowed condition and are individually and sequentially deployed to their respective deployed positions. One or more feed horns are attached to the spacecraft or fixed body that illuminate the respective antennas. A dual axis deployment mechanism is used to deploy each antenna. The dual axis deployment mechanism is also used to steer the beam produced by the antenna. The dual axis deployment mechanism comprises a dual-axis rotatable hinge structure affixed to the spacecraft or fixed body that is coupled to the antenna by way of a substantially rigid reflector support structure. The dual axis deployment mechanism is actuated and controlled to deploy the antenna and steer the antenna beam.

Abstract: A controller and control method that perform satellite orbit-keeping maneuvers and proportionally scale orbit-keeping pulses to automatically minimize disturbance torques on-board a satellite. The controller and control method may also be used to remove residual momentum stored in spinning momentum wheels.

Abstract: A satellite-based antenna system that employs an improved dual function subreflector. An exemplary antenna system comprises a flat plate dual function subreflector and a subreflector positioning mechanism that selectively positions the subreflector at predetermined positions corresponding to two or more operational positions of the satellite. A plurality of feed arrays couple energy to and from the subreflector, and a main reflector generates beams for desired coverage areas. The present invention provides optimum performance from a dual reflector antenna when operating in two or more different satellite positions, with no compromise to the performance for either mode of operation.

Abstract: An automatic, on-board system for orbiting spacecraft that controls and reduces short-term transients caused by roll momentum unloads by manipulating the states of the nutation damper through resetting one of the states in the polynomial transfer function to a value in proportion to the magnitude of the expected roll momentum unload and creating a transient equal and opposite in magnitude to that expected by the roll unload. The compensator will, of its own accord, automatically damp out the resulting transient. Thus the short-term transient is reduced without biasing the spacecraft in roll. No angle bias need be changed or removed.

Abstract: A spacecraft orbit control system and method that provides orbit control of a spacecraft. The system comprises the spacecraft, one or more electric and/or chemical thrusters disposed on the spacecraft, and a control processor having control outputs coupled to the plurality of thrusters. An orbit control algorithm is implemented that determines the current orbit of the spacecraft, determines whether or not to perform stationkeeping, determines desired changes in certain orbit parameters if stationkeeping is to be performed, determines thruster firings that accomplish the desired orbit parameter changes, and fires the thrusters to perform spacecraft stationkeeping and provide spacecraft longitude control. The present invention may be used with any type of orbit determination procedure (such as GPS or ranging, with or without orbit propagation) and any type of stationkeeping algorithm that calculates thruster firings from desired orbit-parameter corrections.

Abstract: An automatic network analyzer that measures continuous wave radio microwave driven transfer characteristics of nonlinear devices and simultaneously calculates and displays corresponding noise driven transfer characteristics and noise power ratio data. This automatic network analyzer employs software or firmware that uses closed-form equations to exactly calculate noise parameters. This is done in real-time as CW measurements are taken.

Abstract: A support for a deployable reflector for use on a modular satellite antenna assembly is constructed of an elongated boom supported at both ends by a pair of two axis actuators. The boom is attached at its inboard end to the satellite structure in close proximity to the point of attachment of the associated signal feed assembly to minimize the differential thermal stress throughout the antenna assembly.

Abstract: Variable beamwidth antenna systems for use on spacecraft that is capable of changing their beamwidths while the spacecraft in on orbit. The variable beamwidth antenna systems include a main reflector, a subreflector, a feed horn, a main reflector displacement mechanism and a feed horn (or subreflector) displacement mechanism. For broaden the beamwidth, the RF feed horn and the subreflector are moved close together by proper distance. The main reflector is moved away from the subreflector along a line through centers of their respective surface by a distance given by a predetermined equation. Another embodiment of the present invention provides for a zoom contour beam antenna system that radiates a contour beam and whose beam is variable or zoomable.

Abstract: A shaped reflector antenna system for use on a communication satellite that comprises a plurality of shaped reflector antenna configurations. In an exemplary system, a first one of the antenna configurations is a diverged shaped reflector antenna and a second one of the antenna configurations is a converged shaped reflector antenna. Each of the shaped reflector antennas comprise a main reflector, a subreflector, and a feed horn. The feed horn illuminates the subreflector with RF energy in the shape of a feed cone that is reflected to the main reflector. The direction of RF energy propagation emitted by each of the shaped reflector antennas is in a direction that is different from a direction defined by a vector between a predetermined vertex and focal point associated with the respective shaped reflector antenna.

Abstract: A broad-band digital satellite communications system for providing broad-band data services. The system comprises a first spacecraft, generally a geo-stationary earth orbit communications device, and at least one controller having broadband communications capability with the first spacecraft. The system also includes at least one second spacecraft, generally a low earth orbit (LEO) communications device. The second spacecraft comprises ; communications capability with the at least one first spacecraft; low data rate communications capability with a land based system, generally a mobile communications service provider; and broadband communications capability with a mobile user subscriber to the mobile communications service provider.

Abstract: A tool and related method uses an insert for lap splicing two end to end connected tubes to one another. The insert is formed from plurality of members which together are receivable into the internal size and shape of the internal tubular member. The insert can be pulled out of the tubular members once the lap joint is formed. The invention also resides in a tool which locates a flange onto the outside surface at the end of the tubular member to effect registration of it in a flush and perpendicular manner.