Abstract: A system for controlling attitude about pitch, yaw, and roll axes and axial thrust of a body. The system comprises a main thrust generator located on an aft portion of the body and at least one reaction control system (RCS) located on a forward portion of the body. A thrust vector controller (TVC) is connectable to the main thrust generator and at least one RCS controller is connectable to the RCS. The RCS controller and the TVC are synchronized to adjust the direction of the principal line of thrust through the body center of gravity.

Abstract: Multi-directional (reversible and parallel) loop heat pipe thermal systems for use on a spacecraft. The multi-directional loop heat pipe thermal systems may comprise reversible or parallel loop heat pipes that provide efficient thermal pathways that are directionally independent between any combination of equipment mounting panels and radiator panels. Loop heat pipes of the reversible loop heat pipe thermal system are coupled between opposite ends of respective evaporator/condenser flanges. The evaporator/condenser flanges each comprise a condenser and an evaporator. The parallel loop heat pipe thermal system comprises pairs or sets of parallel heat pipes that are respectively coupled between a condenser flange and an evaporator flange. The reversible or parallel loop heat pipes may be routed to a multiple number of radiator panels in order to optimize the use of a radiator panel by always transporting heat to the coolest radiator panel.

Abstract: A filter that produces a multiple passband response as a single device. The multiple passband filter has a plurality of poles concentrated in a desired passband of the filter. A plurality of zeroes are located outside of the desired passband to form passband edges. One or more zeroes are located in a central portion of the passband to form multiple passbands within the passband edges.

Abstract: An electric propulsion (EP) device is used to enable, a stationkeeping satellite to track a prescribed stationkeeping Earth orbit. EP propellant and electric power are throttled to vary the thrust and specific impulse of the EP device. A solar array provides electrical power during each Earth day cycle with excess power above that needed by the spacecraft stored by a battery. Software control manages the voltage, current and burn time to minimize propellant usage and impact to the system.

Abstract: A system and method for RF autotracking multiple antennas (preferably located on a spacecraft) to compensate for disturbances experienced by the antennas. The system and method estimate high frequency errors associated with all of the antennas. The high frequency errors may be estimated using a currently selected antenna and a high-pass filter. The high frequency errors may be estimated using a sensor mounted on the spacecraft, such as a gyro or star tracker, or may be estimated using information, such as planned thruster firings, for example, from a spacecraft attitude control system. Alternatively, the high frequency information may be estimated using any combination of data from these sources. Low frequency errors are estimated using measurements from each selected antenna. The algorithm implemented in the present invention explicitly accounts for the frequency content of each disturbance source.

Abstract: A patch filter element has an electrically-insulating substrate with an electrically conductive region on a first surface of said substrate, and a slot such as a crossed slot dividing the conductive region into a plurality of triangular sections. A mode coupling device, such as a cutout corner of a triangular section, induces orthogonal modes of vibration of an electromagnetic field about the plurality of sections. The ferroelectric oxide is disposed in the slot for adjusting a dielectric constant of the oxide in accordance with a bias voltage applied across the slot between adjacent ones of the sections for turning the patch filter element. Metallic walls may be constructed along edges of the slot for increased capacitance.

Abstract: A flexible waveguide has a flexible wall enclosing an elongated cylindrical passage for transmission of an electromagnetic wave along the passage. A succession of corrugations is disposed along an interior surface of the wall facing the passage. The corrugations are spaced apart by a distance less than approximately 0.2 wavelength of the electromagnetic wave, each of the corrugations having a height greater than the distance but less than approximately 0.5 wavelength of the electromagnetic wave, and each corrugation having a curved surface to minimize loss in the transmission of the electromagnetic wave.

Abstract: A method for controlling a spacecraft comprising the steps of providing a first spacecraft in a known first predetermined orbit, and a second spacecraft in a second predetermined orbit. The distance between the first and second spacecraft is measured. The measured distance and data describing the known first predetermined orbit are used for determining an orbital error bias of the second spacecraft relative to the second predetermined orbit. The second spacecraft is maneuvered to compensate for the orbital error bias, and to maintain the second spacecraft in the second predetermined orbit.

Abstract: Systems and methods for launching a satellite into orbit that optimize the mass of the satellite delivered into orbit. A satellite carrying one or more chemical propulsion devices and one or more electric propulsion devices is launched into a transfer orbit using a launch vehicle. In one embodiment, a selected chemical propulsion device is fired to raise the orbit of the satellite from the transfer orbit to an intermediate orbit. One or more electric propulsion device is fired to raise the orbit of the satellite from the intermediate orbit to final geosynchronous orbit and the one or more electric propulsion device is throttled to produce variable thrust levels so as to operate at all optimum specific impulse level to optimize the mass of the satellite delivered into orbit. In another embodiment, the electric propulsion device may deliver the satellite into a near-geosynchronous orbit instead of final geosynchronous orbit.

Abstract: A method for controlling a spacecraft comprising the steps of providing a first spacecraft in a known first predetermined orbit, and a second spacecraft in a second predetermined orbit. The distance between the first and second spacecraft is measured. The measured distance and data describing the known first predetermined orbit are used for determining an orbital error bias of the second spacecraft relative to the second predetermined orbit. The second spacecraft is maneuvered to compensate for the orbital error bias, and to maintain the second spacecraft in the second predetermined orbit.

Abstract: A Ka-band horn for transmitting and receiving information between a ground station and a satelitte includes three sections. The throat segment of the horn is adapted for coupling to a feed and includes circular, alternating grooves and webs that are of a widening type created by linearly increasing the width of the grooves in the direction of the horn's aperture. The throat corrugations are for matching the impedance of adjacent sections of the horn. A middle segment includes an up-angle flare section and a down-angle flare section each having dual depth corrugations that enable the horn to achieve a near-HE11 mode at the aperture of the horn. The final segment of the horn is a truncated, smooth-walled, cone.

Abstract: A spacecraft attitude control system that enables friction and stiction compensation for attitude control of a spacecraft using at least one reaction wheels that can spin through zero rpm without degradation in pointing. The system removes nuisance disturbances relating to friction or stiction that detract from the ability of the system to maintain or change spacecraft attitude. It can remove these effects before they are sensed by the systems attitude control sensors. A friction or stiction compensation buffer is arranged between the spacecraft attitude control subsystem and the torque actuators for the at least one reaction wheel. Since the compensation is localized to each wheel, it is possible to optionally: control wheel operating speeds to safe levels, provide wheel failure flags, provide accurate wheel tracking at slow or zero wheel speeds and provide full access to the wheel torques.

Abstract: Active switch matrix apparatus that is used in a satellite communications system that provides for reconfigurability of the communication channels of the communications system. The active switch matrix apparatus has redundan channels and components that provides for a high probability of success during the lifetime of the satellite. The active switch matrix apparatus is comprised of two switch matrices, one for each polarization (horizontal and vertical). Each of the switch matrices contains redundancy, including redundant paths through power dividers, power combiners and amplifiers to outputs of the apparatus. This is accomplished using a plurality of controllable switches 16 in the power dividers and a plurality of controllable output switches coupled to outputs of the amplifiers. Each of the switch matrices are coupled to redundant DC/DC converters and switch matrix controllers.

Abstract: Feed horn apparatus for use in a multiple-feed antenna system. The present invention comprises a corrugated feed horn and an antenna array or cluster of feed horns arranged in a hexagonal lattice pattern. The feed horn comprises a hexagonal aperture formed by a circular-to-hexagonal transition section a corrugated section disposed adjacent to the circular-to-hexagonal transition section, a tapered section disposed adjacent to the corrugated section, and an input section having an input/output port disposed adjacent to the tapered section. The corrugated feed horn has good beam pattern symmetry, low cross-polarization, and sidelobe levels, along with an increased horn aperture area. As a result, the efficiency of the corrugated feed horn is improved by transitioning from a circular to the hexagonal aperture.

Abstract: A satellite communication system includes a plurality of spacecraft in geosynchronous orbit, where each spacecraft provides 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 one of the spacecraft. Each 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. In accordance with the invention the beams have at least one of different sizes and shapes, including circular and elliptical, and are non-contiguous over a least a portion of the surface of the earth.

Abstract: Systems and methods that employ a phase change material to provide thermal control of electric propulsion devices (thrusters). A spacecraft is configured to have an electric propulsion thruster. The electric propulsion thruster is surrounded with a phase change material. Suitable phase change materials include high-density polyethylene (HDPE), waxes, paraffin materials, and eutectic salts. The spacecraft is launched into orbit. The electric propulsion thruster is fired for a predetermined period of time. Heat generated by the electric propulsion thruster is absorbed and stored in the phase change material while the thruster is firing. The stored heat is dissipated into space after the thruster has stopped firing.

Abstract: A loop heat pipe cooling system for use on a spacecraft. The loop heat pipe cooling system has loop heat pipes routed from internally facing surfaces of one or more internally located equipment panels to externally located radiator panels. Heat is collected at evaporator ends of each loop heat pipe and transported to condenser ends of the respective loop heat pipe. The condenser ends of the loop heat pipes may either be embedded within the radiator panel or externally mounted and coupled to the radiator panel using a loop heat pipe condensing flange. Fixed conductance heat pipes may also be used in any or all of the internal panels and radiator panels in order to collect and distribute heat loads to and from the loop heat pipes.

Abstract: An attitude control system comprising a controller and a noise screen device coupled to the controller. The controller is adapted to control an attitude of a vehicle carrying an actuator system that is adapted to pulse in metered bursts in order to generate a control torque to control the attitude of the vehicle in response to a control pulse. The noise screen device is adapted to generate a noise screen signal in response to the control pulse that is generated when an input attitude error signal exceeds a predetermined deadband attitude level. The noise screen signal comprises a decaying offset signal that when combined with the attitude error input signal results in a net attitude error input signal away from the predetermined deadband level to reduce further control pulse generation.

Abstract: A waveguide slot array antenna system, for use with a communications system 30 disposed on a satellite. The waveguide slot array antenna system comprises a feed waveguide having an input port and multiple output ports, a waveguide slot array having a plurality of slots formed therein that is coupled to the feed waveguide, and a waveguide lens disposed adjacent to the waveguide slot array. The phase of each contributing radiating waveguide is controlled to achieve radiation pattern shaping. Inner dimensions of the rectangular waveguides are designed to provide a phase velocity inside each waveguide that results in the appropriate radiated phase at the output of the waveguides. The phase radiated by each rectangular waveguide is determined by design, and the radiation pattern that results from the combined contributions of the array can be shaped to produce a complex radiation contour.

Abstract: An equalizer that couples a dual-mode dielectric resonator to a planar transmission line, creating an all-pass network. Coupling is achieved using circular polarization of the electromagnetic field in the dielectric resonator. The all-pass, non-reciprocal network is realized by the use of circular polarized energy and an offset cross shaped, through transmission line.