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: The new signal amplifiers dynamically adjust based on the signal's power level. When used on multi-beam satellites, increased signal power indicates an increase in traffic on the channel. The power level of the input signal is sensed and converted to a DC signal, which is applied to a control terminal of a power supply that regulates DC power supplied to the amplifier. During periods of increased traffic, an increase in system power is allocated to the channel. By monitoring traffic on a plurality of channels, available onboard power is allocated based upon the relative channel requirements. The sensed power of multiple channels is summed and scaled to determine the power requirement of the channel relative to the other channels. A command voltage received from a ground station may be switched in place of the summed voltage to allow amplification levels to be controlled from the ground station.

Abstract: A contactless system for imaging an acoustic source within a workpiece directs a preferably annular optical probe beam pattern onto the vibrating workpiece surface, with the vibrationally modulated beam then detected by an array of preferably non-steady-state photo-emf detectors arranged in a similar pattern. The probe beam is scanned over the vibrating surface, either mechanically or through an electronically simulated phased array scheme. Time gating is used to suppress unwanted side-lobes when the individual detector outputs are summed over an appreciable waveband. A self-calibration scheme is also preferably used that provides a quantitative as well as qualitative output. A calibration modulation is imposed on at least one of the probe and reference beams, with the calibration modulation later removed at a post-detector stage and used to normalize the acoustic modulation output.

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: 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 micro-dimensional coupling conductor with a shape that is customized for a particular electronic device. A fabrication method is used in which the physical dimensions of the conductor are precisely controlled with photolithographic techniques, resulting in a conductor that is more precisely tuned to the operating frequency of the device. The conductor is fabricated on an SiO.sub.2 substrate using vacuum deposition techniques. After fabrication, the conductor is separated from the SiO.sub.2 substrate by dissolving the SiO.sub.2. Alternatively, the conductor may be fabricated on a Teflon.TM. substrate. The use of a Teflon substrate allows a user to remove the conductor from the substrate by applying a small mechanical force to the conductor.

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: A beam-forming network having a network of phase shifting devices that is independent from other parts of the beam-forming network. In one embodiment, the network of phase shifting devices has multiple layers between the power divider and power combiner layers. The multiple layers provide a selectable phase shift for each feed independent from the other feeds. In another embodiment, the network of phase shifting devices is one layer of commendable phase shifters. In any embodiment, the resulting composite beam has higher directivity and lower side lobes as compared to conventional beam-forming networks.

Abstract: Attitude-control methods are provided which eliminate or reduce structural resonances in spacecraft that are excited by momentum wheel imperfections. The methods are preferably practiced with an over-determined attitude-control system which is typically available because spacecraft often carry backup momentum wheels to insure against failure of primary momentum wheels. In a method embodiment, a set of angular-velocity waveforms is selected that substantially realizes a commanded momentum vector when applied to a corresponding set of momentum wheels wherein none of the selected angular-velocity waveforms dwells at a resonant frequency of the spacecraft. The angular velocity of the corresponding set of momentum wheels is then conformed to the selected set of angular-velocity waveforms to realize a spacecraft attitude that corresponds to the commanded momentum vector without exciting the resonance.

Abstract: An apparatus for providing uniform light intensity is disclosed. The apparatus consists of a number of wires arranged diagonally and horizontally on a frame. The horizontal wires are arranged with variable vertical spacing to create eight different zones of light attenuation transmission. The apparatus is designed such that the zones having the highest light attenuation are placed in front of the most intense light from a source and the zones having the lowest light attenuation are placed in front of the least intense light from the source. By matching the zones of the apparatus to the intensity pattern of the light source a uniform light source is created.

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: A system and method for acquiring the Earth by a three-axis stabilized spacecraft in the presence of a significantly time-varying Sun-Earth angle including obtaining an Earth cone described by rotating the nadir vector about the Sun vector, slewing the spacecraft about an axis until the Earth sensor boresight touches an edge of the Earth cone, updating the Earth cone due to the changing Sun-Earth separation angle, performing a spiral coning maneuver about the updated Earth cone until the Earth sensor detects the Earth, and locking onto the Earth so as to hold the Earth sensor boresight coincident with the nadir vector. Additionally, the spacecraft may be rotated about the nadir vector so as to bring the spacecraft into a desired final attitude.

Abstract: A contactless system for imaging an acoustic source within a workpiece directs a preferably annular optical probe beam pattern onto the vibrating workpiece surface, with the vibrationally modulated beam then detected by an array of preferably non-steady-state photo-emf detectors arranged in a similar pattern. The probe beam is scanned over the vibrating surface, either mechanically or through an electronically simulated phased array scheme. Time gating is used to suppress unwanted side-lobes when the individual detector outputs are summed over an appreciable waveband. A self-calibration scheme is also preferably used that provides a quantitative as well as qualitative output. A calibration modulation is imposed on at least one of the probe and reference beams, with the calibration modulation later removed at a post-detector stage and used to normalize the acoustic modulation output.

Abstract: An electronic structure includes an electronic device, and a heat sink assembly in thermal contact with the electronic device. The heat sink assembly is formed of a piece of pyrolytic graphite embedded within a metallic casing and intimately contacting an interior wall of the metallic casing. The heat sink assembly is substantially fully dense. The heat sink assembly is fabricated by assembling the piece of pyrolytic graphite within the disassembled elements of the metallic casing, and then simultaneously heating and pressing the initial assembly until it is substantially fully dense.

Abstract: A method for stripping photoresist used as an etch mask in carbon based reactive ion etching includes flood exposing a patterned photoresist with a light and cyclically exposing the photoresist with an oxygen plasma in between the carbon based plasma. The step of cyclically exposing occurs after the step of flood exposing. The step of flood exposing includes the step of decomposing photosensitive compounds in the photoresist, while the step of cyclically exposing includes the step of cyclically removing layers of the photoresist.

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.

Abstract: A reflectarray antenna for achieving increased dynamic phase range has a plurality of dipole elements positioned across the antenna surface. The elements include a single dipole element having a predetermined length that is approximately proportional to the dynamic phase range through which the first dipole element can reflect. The elements also include a coupled dipole element which comprises a longer dipole and a shorter dipole. The longer dipole and the shorter dipole are positioned on the reflectarray surface such that they are spaced a predetermined distance apart.

Abstract: An agile, spinning spacecraft has a first body portion and a second body portion which is rotatably coupled about a first rotational axis to the first body portion. A pair of planar solar cell arrays are rotatably coupled to the second body portion along a second rotational axis that is preferably orthogonal to the first rotational axis. The first body portion can be spun if desired and the first rotational axis can be directed by an attitude control system to have selected orientations. The solar cell arrays are rotated about the first and second rotational axes in accordance with steering laws which maintain the arrays in an orthogonal relationship with a Sun line.

Abstract: A variable absorptive/reflective high power attenuator for attenuating microwave signals in a communication system is formed from a circulator connected to a section transmission line such as a waveguide, having at least one adjustable tuning element connected thereto. The transmission line itself is terminated with a microwave energy absorbing load. A signal injected into the circulator is partially reflected by the tuning element(s), and partially absorbed in the load. The reflected portion is routed to an output port of the circulator. The non-reflected portion is dissipated as heat by the load. The amount of output of signal attenuation is selectively controlled by the location and penetration of the tuning elements. In another embodiment, a latching type circulator is utilized to allow selective switching of the attenuation level insitu. More than one such switching type attenuator can be cascade connected to form a single customizable and variable attenuator design.