Abstract: A navigation and mobile communication satellite system including a Geo-Mobile (GEM) satellite (14) and a plurality of Global Position System (GPS) satellites (50). The GEM satellite (14) is in operative communication with at least one ground segment (12) and at least one user segment (16), and includes a GEM processor for providing communication services to the user segments (16). The GPS network is also in operative communication with at least one of the user segments (16) and at least one of the ground segments (12). The GPS network provides navigation data to the user segment (16). Each of the ground segments (12) include a gateway station (28) for receiving the navigation data and uplinking the navigation data to the GEM satellite (14) such that the navigation data is rebroadcast to the user segments (16) at a higher power than from the GPS network alone. In this manner, the GEM system provides a navigation signal at a much higher power than the present GPS system.

Abstract: A resonator tuning system includes an apparatus coupled to a resonator for changing the resonator's resonance frequency. Tuning of the resonator is accomplished by varying the coupling to a capacitor or varactor, rather than by varying the capacitor. An interferometer, such as a Mach-Zender interferometer is coupled to the resonator and changes the resonance of the resonator by applying an actuation voltage to vary the coupling to the resonator. In this way, a resonator may be tuned and maintain high unloaded Q properties while being coupled to a varactor or other load.

Abstract: A cavity-coupled microwave filter that uses TE011 and TE01&dgr; mode resonators. The cavity-coupled microwave filter includes an input port, a first resonator having a first opening, wherein the first opening receives electromagnetic energy from the input port, a second resonator having a second opening, wherein the second opening receives electromagnetic energy from the input port and wherein the first resonator and the second resonator are electromagnetically coupled. The cavity-coupled microwave filter further includes an output port, a third resonator having a third opening, wherein the third opening transfers electromagnetic energy to the output port and wherein the second resonator and the third resonator are electromagnetically coupled and a fourth resonator having a fourth opening, wherein the fourth opening transfers electromagnetic energy to the output port and wherein the third resonator and the fourth resonator are electromagnetically coupled.

Abstract: A starter circuit particularly suitable for a plasma of an ion engine for a spacecraft includes a power supply having an output inductor with a tap. A switch is coupled to the tap. The switch has a control input. A pulse control logic circuit is coupled to said control input, said pulse control logic circuit controlling said switch to an off state to generate a high voltage discharge.

Abstract: A system and method of estimating the attitude of a spacecraft is disclosed. A three-axis inertial-based estimate of spacecraft attitude is produced and is compared to a stellar-based estimate of spacecraft attitude. A Kalman filter having states associated with gyro scale factor and/or misalignment errors compares the stellar-based attitude estimate to the inertial-based estimate of attitude and apportions the total error into three time varying matrices. A first time varying matrix is associated with gyro scale factor and misalignment errors, a second time varying matrix is associated with gyro bias errors, and a third time varying matrix is associated with attitude errors. The time varying matrices are applied as corrective feedbacks to the inertial-based estimate of spacecraft attitude and are adaptively adjusted to minimize the error therein.

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 bistable micro-electromechanical switch (10) having two parallel plate capacitors (17, 19) spaced a distance from each other on a substrate (12). A transmission line (30), having a detached segment (22), that is movable or the substrate (12), is located on the substrate (12) between the parallel plate capacitors (17, 19). A dielectric beam (24) is attached to the movable transmission line segment (22) and the ends of the dielectric beam (24) protrude into each of the parallel plate capacitors (17, 19). When a voltage (26, 28) is applied to one of the capacitors (17 or 19), the dielectric beam (24) is pulled into the capacitor (17 or 19) and brings the movable transmission line segment (22) with it. As the transmission line segment (22) is moved either into, or out of, alignment with the transmission line (30), a path through the transmission line is either closed, or opened.

Abstract: Planar vibratory gyroscope structures are provided which are inherently symmetric, which facilitate the use of simple monolithic fabrication processes and which enable the use of sensitive control and sense systems. A planar vibratory member of these structures has a hollow frame, a plate that has a plate perimeter and is positioned within the frame and a plurality of elongate beams which couple the plate to the frame wherein each of the beams is proximate to and substantially parallel to a respective portion of the plate perimeter. The exterior rim of the planar member can be supported by a substrate which provides room for easy access to the plate with mode control and sense systems.

Abstract: A star tracker coupled to the spacecraft having a star catalog associated therewith. A sun sensor is coupled to the spacecraft. A control processor is coupled to the star tracker and the sun sensor. The processor obtains star data using a star tracker and an on-board star catalog. The processor generates a coarse attitude of the spacecraft as a function of the star data, and establishes a track on at least one star in the on-board star catalog. The processor calculates a sun tracking rate, and obtains a normal phase attitude as a function of the star data and the coarse attitude. The information is used to slew the spacecraft to a desired attitude.

Abstract: An application-specific rf optoelectronic integrated circuit having a generic chip member and a defining substrate in communication with at least one generic chip member. The generic chip member contains passive building block components that are independent from each other and being connected by paths external to the generic chip member. The external connection paths are defined by a defining substrate member having passive components for providing optical and electrical interconnection between selected building block components on the generic chip member to define the specific function of the integrated circuit. It is possible to use the same design of the generic chip for several applications merely by altering the interconnect paths on a defining substrate.

Abstract: A system and method for determining the attitude in an inertial frame of a spacecraft spinning about an axis in a body frame including determining momentum vector direction in the inertial frame; determining momentum vector direction in the body frame; acquiring information from an at least single-axis sensor; obtaining reference information on the at least single-axis sensor; updating the attitude in the inertial reference frame using the momentum vector direction in the inertial frame, the momentum vector direction in the body frame, the output of the at least single-axis sensor, and the reference information on the at least single-axis sensor; and propagating the attitude using data from one or more inertial sensors.

Abstract: A traveling-wave photodetector (10, 22, 30) having a waveguide layer (12) separated, such as by an intermediate layer (24), from an absorbing layer (14). Absorbed power is spread out, minimizing thermal heating of the photodetector (10, 22, 30). Light travels through a weakly absorbing optical waveguide (12) and the electrical current generated by the absorbed light is collected by electrodes (18, 36). The juxtaposition of the waveguide layer (12) and the absorbing layer (14) eliminates electron and hole trapping allowing high-power and large bandwidth operation of the traveling-wave photodetector (10, 22, 30).

Abstract: A method is provided for controlling the attitude of a momentum biased spacecraft about all three mutually orthogonal axes during a thruster firing maneuver without separately sensing angular displacement, angular rate, or angular acceleration about the spacecraft yaw axis. The method includes a transient phase during which a yaw feedforward torque is computed based on the known pitch/yaw coupling due to thruster geometry, and a steady state phase, during which feedback gains are adjusted to estimate yaw attitude based on coupling of a steady state disturbance torque about the roll axis of the spacecraft and a steady state disturbance torque about the yaw axis of the spacecraft.

Abstract: A millimeter wave multilayer phased array assembly has a multilayer board consisting of several laminated printed wiring boards (PWBs) and a frame having a waveguide input and waveguide output. The PWBs are made of a high frequency laminate material and have a pattern of metalization to perform varying electronic tasks. These tasks include electrical interconnection, RF signal transmission, DC current routing and DC signal routing.

Abstract: An analog to digital converter has an optical pulse source generating an optical pulse chain having a plurality of optical pulses. An optoelectronic digitizer has a first input receiving the optical pulse chain. The digitizer has a second input for receiving the analog signal to be converted. The digitizer has a plurality of digital outputs. Each of the digital outputs corresponds to a range value. An electronic encoder receives the plurality of digital outputs. The encoder has an output in a predetermined digital format.

Abstract: A multiplexer/demultiplexer structure is provided which multiplexes multiple channel signals through a common tee of a tee/manifold mulitplexer arrangement. This multiplexing significantly reduces the number of tees required for a given number of multiplexed channels. Accordingly, mulitplexer/demulitplexer design time is reduced and fabricated multiplexers/demultiplexers are lighter, smaller and less expensive. The tee multiplexing is facilitated with multiple access apertures that are isolated by a septum. The septum forms reduced-height waveguides which define a path length between apertures that is sufficient to significantly reduce higher-order modes and, therefore, apeture interactions.

Abstract: The attitude of a spinning spacecraft whose spin axis is substantially in the plane of the orbit is controlled without the use of reaction control thrusters. A two-axis gimbal on which a momentum wheel is mounted is secured to a despun platform. The despun platform is in rotational communication with the central body. Two actuators are used to selectively pivot the gimbaled momentum wheel about each gimbal axis in order to apply a control moment to change the attitude of the spacecraft.

Abstract: Methods are provided for accurate insertion of a constellation of satellites into a common orbit plane with a mean inclination &thgr;. 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 &thgr; 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 spacecraft having a pair of asymmetrical side-mounted antennas that are designed to control the net angular momentum of the spacecraft over a twenty-four hour period. One of the side-mounted antennas is a dual surface antenna having a front surface that has a reflective sunshield overlay thereon and a rear surface. The rear surface of this side mounted antenna has a reflective blanket attached directly to the rear surface of the antenna that has low-&agr; properties to control the solar or radiation force acting on the spacecraft.

Abstract: A heat pipe comprising a wick, working fluid, a chamber housing the wick and working fluid, and a plurality of wraps of a graphite composite fiber, preferably THORNEL graphite fiber, number P-120 2K. For maximum strength, the wraps are in different directions. The heat pipe can be integrally incorporated and bound to a printed wiring board, thereby eliminating the need for additional inefficient thermal interfaces.