Abstract: Autonomous slewing of a spacecraft about a desired axis using reaction wheels permits a maximum slew rate without wheel saturation even with one wheel failure. The slew is carried out if the total angular momentum of the spacecraft is less than a momentum storage threshold determined from reaction wheel availability. The momentum threshold may be found as the radius of a sphere inscribed in a polyhedron in momentum space, the polyhedron based on the maximum single wheel capacity and the geometry of the reaction wheel system as well as the reaction wheel availability. The momentum available for the slew is determined from the total angular momentum and the availability of each reaction wheel. The slew rate magnitude and slew direction are based on the available momentum.

Abstract: A rocket engine is prepared by fabricating a combustion chamber having an annular wall as a single piece of material. The wall has a first axial region with a first inner diameter, a second axial region with a second inner diameter greater than the first inner diameter, and an inner wall step transition between the first axial region and the second axial region. The combustion chamber is attached to an injector by bonding an annular metallic deposit to the first axial region of the combustion chamber, providing an annular adaptor ring, first welding the adaptor ring to the metallic deposit, and second welding the adaptor ring to the injector.

Abstract: A method for steering the payload beam of a satellite in a non-geostationary orbit toward an intended service area having known geographical dimensions in order to obtain improved pointing performance with a corresponding reduction in the demand on onboard hardware and software systems. The method comprises the steps of determining a subterranean target point and a direction fixed in the payload beam, calculating the orientation that points the payload beam direction through the subterranean target point, and maintaining this payload beam orientation using an on-board attitude control system.

Abstract: An apparatus and method for synchronizing a derived bit clock with a transmit bit clock of a transmitted data signal is disclosed. The present invention uses a divide-only direct digital synthesizer and a fixed local oscillator. The synthesizer generates a derived bit clock by dividing the fixed, high frequency local oscillator. A transition detector identifies valid bit transitions in the unsynchronized data signal. At each valid transition, a control algorithm determines whether to adjust the frequency and/or phase of the derived data clock in order to maintain synchronization between the derived bit clock and the transmit bit clock. The unsynchronized data signal and the derived bit clock are processed by a reclock latch to generate a synchronized data signal.

Abstract: A dual-linearly polarized multi-mode rectangular horn includes a step junction in each of the two orthogonal planes for producing a desired amount of the higher order TE.sub.30 mode signal along with the dominant order TE.sub.10 mode signal for both of the vertical and horizontal polarization signals. The rectangular horn further includes a phasing section in each of the two orthogonal planes for causing the TE.sub.30 mode signal to be a desired amount of degrees out of phase with the TE.sub.10 mode signal at the aperture plane of the rectangular horn for both of the vertical and horizontal polarization signals. The rectangular horn is for use in a reconfigurable satellite array antenna.

Abstract: Methods are provided for accurate insertion of a constellation of satellites into a common orbit plane with a mean inclination .theta.. In an embodiment of the invention, an initial satellite is inserted on an initial insertion date and, for each of subsequent satellites, a respective orbit insertion date is selected. With reference to the latter date, the initial insertion RAAN is updated to find a current RAAN. This updating is accomplished with knowledge of a regression rate of the initial satellite's orbit normal about a Q vector. With reference to the Q vector's inertial position, an instantaneous inclination that corresponds to the mean inclination .theta. and the updated RAAN is then derived. Finally, the subsequent satellite is injected into an orbit having the instantaneous inclination and the current RAAN.

Abstract: A plurality of end caps engagable with a microwave cavity each have an underside configured differently to cause the microwave cavity to have different electrical responses depending on which end cap engages the microwave cavity. A microwave device includes a cylindrical cavity and an end cap movable within the cavity to change its axial position within the cavity thereby varying the volume and the electrical response of the cavity.

Abstract: A power divider/combiner for dividing received powers at 4 input ports, transmitting the divided powers to each of 4 output ports and combining the transmitted powers at each of the output ports. The power divider combiner has through transmission lines flanked on either side by secondary through transmission lines that interconnect corresponding input and output ports. The through transmission lines are likewise interconnected at a center node by a plurality of branch transmission lines. A method for making a power divider/combiner includes merging two 0 dB couplers by joining the center points of each of the branch transmission lines.

Abstract: A method and apparatus for estimating attitude sensor bias in a satellite system uses attitude sensors and a spacecraft control processor. Attitude sensors provide output signals, which may contain bias. The present invention interprets the signals, determines the bias present in the signals, and generates an output signal to offset the bias in the signals from the attitude sensors, thereby leading to more accurate positioning of the satellite employing the present invention.

Abstract: A method and apparatus for autonomous acquisition of attitude in a stellar inertial spacecraft attitude system is disclosed. The present invention uses star trackers, an on-board star catalog, spacecraft steering and inertial sensors to determine spacecraft attitude. The present invention utilizes pattern match and pattern rejection methods and uses multiple stellar snap-shots in conjunction with spacecraft steering and spacecraft inertial measurements to acquire spacecraft attitude. Spacecraft inertial measurements are used to connect multiple stellar snap-shots to provide adequate star information that can be used to acquire spacecraft attitude. In an attitude determination system using star trackers, the star trackers may have a narrow field-of-view or few stars may be available for viewing. The present invention uses pattern matching and pattern rejection on different sets of stars, thereby allowing attitude acquisition when the number of stars in view is small.

Abstract: A spacecraft control system having a spacecraft with a gimbaled thruster attached thereto. An actuator is operationally attached to the gimbaled thruster to control the angled position of the gimbaled thruster in two orthogonal directions. A position control system is provided which sends a control signal to the actuator which moves the gimbaled thruster to an angled position in response to the control signal, wherein the angled position of the gimbaled thruster controls the attitude and orbital velocity of the spacecraft.

Abstract: A dual band omni directional antenna is disclosed. A dielectric cylinder supports a cone shaped reflector over a corrugated radio frequency horn. Orthogonal mode transducers produce and conduct circularly polarized radio frequency waves within the horn. The reflector, the horn, and the transducers are all coaxially disposed. The antenna produces a torodial radiation pattern in a plane that is substantially orthogonal to the axis of the antenna. Transmit and receive functions may be performed simultaneously using a single reflector and two orthogonal mode transducers.

Abstract: A structure includes an electronic device support, an electronic device, and a fastener for the electronic device support and the electronic device. There is a first dovetail slot in the electronic device support and a second dovetail slot in the electronic device. The first dovetail slot and the second dovetail slot are in a facing relationship. A bar of a shape-memory alloy in the recovered state is received into the first slot and the second slot and has a cross sectional shape with V-shaped grooves on its opposing lateral sides engaging the first dovetail slot and the second dovetail slot.

Abstract: A spacecraft with a reaction wheel system can be autonomously safed by setting the solar wings to continuous tracking, determining a slew rate vector based on the total angular momentum, and slewing the spacecraft using the slew rate vector until commanded to stop autonomous safing. In a typical application, the spacecraft has a reaction wheel assembly with four wheels arranged to form a right regular pyramid. Two reaction wheels on opposite edges of the pyramid form a first pair and the two remaining reaction wheels forming a second pair. The slew axis of rotation is found by determining as a selected pair the first pair if either reaction wheel in the second pair is inoperative, otherwise determining as the selected pair the second pair and determining as the slew axis of rotation the normalized projection of the axes of rotation of the selected pair onto the base. The slew direction is determined by the sign of the total angular momentum component along the slew axis of rotation.

Abstract: Methods are provided for sensing radiation direction over a wide field-of-view. In one process step, radiation is received over a first solid angle and, in response, the direction of that radiation is sensed along a first sensor axis. In a similar process step, radiation is received over a second solid angle and, in response, the direction of that radiation is sensed along a second sensor axis. The first and second solid angles are arranged to spatially intersect over a third solid angle that is a subset of the first solid angle and a subset of the second solid angle. These methods facilitate the determination of inertial planes over a wide field-of-view and the third solid angle facilitates the determination of inertial vectors. Radiation sensor structures in accordance with the methods are also provided.

Abstract: A battery system includes an electrical storage cell having a positive terminal and a negative terminal. The electrical storage cell is provided with a normally open bypass circuit path that is closed in the event of an open-circuit failure of the electrical storage cell. The bypass circuit path includes a normally open bypass circuit path comprising a diode having a cathode and an anode. The cathode of the diode is electrically connected to the positive terminal of the electrical storage cell and the anode of the diode is electrically connected to the negative terminal of the electrical storage cell. The diode fails to a shorted current path at an imposed current less than a cell failure current, providing a low-resistance, low-voltage-drop bypass of the electrical storage cell.

Abstract: A structure is formed of at least two structural elements that are bonded together with an electrically conductive organic adhesive system. The adhesive system is a mixture of an organic adhesive such as a thermosetting epoxy and a filler of electrically conductive carbon particles having a porous, sponge-like structure. In one application, the structural elements are exterior panels of a spacecraft coated with an electrically conductive paint, and in other applications the structural elements are not coated. The adhesive system permits static electrical charge to flow through otherwise insulated joints to equalize the static potential throughout the structure and eventually to dissipate the charge.

Abstract: A method and system for reserving channel resources in a random-access, multiple-path communication system utilizes a transmit group addressing arrangement for a reservation packet. A transceiver terminal wanting to transmit a signal must first send a reservation request packet to a packet router. Each reservation request packet includes an address header identifying the entire group of terminals to which the transmitting terminal belongs as the destination for the reservation request packet, and a data segment identifying the terminal and the channel resources to be reserved. After the reservation request packet is transmitted to the packet router, each terminal in the transmit group will determine the order of transmission depending on the sequence in which all reservation packets are received from the router. When a terminal begins transmission, a synchronization packet is sent as an indicator for allowing the remaining terminals to predict the end of transmission.

Abstract: An algorithm (20) or method (20) for verifying that a system hierarchically built from smaller components implements a desired equation that represents the system. Symbolic data is clocked (24) through the system by processing a symbolic test vector using linked equations (22) written (21) for each component of the system. A resulting symbolic equation generated at the output of the system is recorded (25). The symbolic equation is then compared (26) with the desired equation for the system using a symbolic manipulation tool. If the comparison generates a zero difference, the system correctly implements the desired equation representative of the system, and vice-versa.

Abstract: Solar wing positioning methods are provided which favorably reduce seasonal variation of generated power in a satellite while simultaneously managing the composite system influence that off-pointed solar wing operation imposes on the satellite. The composite system influence includes environmental torques and may also include other system influences such as wing-to-body thermal radiation, thruster plume impingement and antenna/sensor field of view encroachment. In the simplest method embodiment, the solar wings are tilted asymmetrically from a nominal position to reduce seasonal power variations and are further tilted symmetrically to generate a solar pressure torque component which, on a diurnal average basis, compensates a gravity gradient torque component that is substantially generated by the net, off-pointed configuration of the wings.