Abstract: An unfurlable reflector antenna system having one or more unfurlable arms that are each shaped in the form of a parabolic right cylinder when it is unfurled. Each arm comprises an RF reflecting membrane or a thin shell as the reflector structure. Each arm is coupled by way of a line feed to a receiver. The system is specifically designed for use on a spacecraft. Each arm may be stowed by flattening the parabolic membrane or shell, and then rolling up the arm, which is accomplished without stretching. The sparse reflector antenna array system is thus stowable in a compact configuration, yet easily unfurls to provide a very large diameter lightweight reflector.

Abstract: A practical stationkeeping method and apparatus wherein an electric propulsion system on a satellite is used to correct north-south drift and the majority of east-west drift which is caused by orbital eccentricity growth. A chemical propulsion system on the satellite is used to correct the remainder of east-west drift due to the growth of orbital semimajor axis. The method and apparatus eliminate the need for additional electric thruster burns in case of an electric thruster failure and therefore eliminates associated power and mass penalties.

Abstract: A system that precisely controls the gain of an RF amplifier over varying temperatures. The system monitors the temperature of the RF amplifier and precisely controls the diode current in PIN diodes to precisely control the gain of the RF amplifier.

Abstract: Communication apparatus comprising a vector division multiple access communications system that uniquely extracts a selected communications link from a communications channel containing many simultaneous links. Each link is assigned a unique vector modulation coefficient using the transmit coefficient generator as its link connection address. The vector modulation coefficient establishes the phase and amplitude states of transmit and receive vector modulators employed in the transmitter and receiver, respectively. The receive vector modulator performs antipodal modulation of the link coefficient and remodulates the received modulated transmit waveform by removing the modulation that was applied by the transmit modulator. When a perfect match occurs, the receive modulator completely removes the modulation applied by the transmit modulator. Thus, a data demodulator following the receive vector modulator has no signal to demodulate and its output is therefore zero.

Abstract: A 12 bit to 8 bit dynamic range compression processor for compressing video data. The dynamic range compression processor uses a lookup RAM, or dynamic range compression RAM, to update offset and compression terms of each field of video in real time. During the active video period of each field, a 12 bit histogram of video pixel values is collected using a histogram RAM for a specific software defined local area of interest. During the video scan retrace time, the histogram is evaluated and offset and compression terms are computed based on upper and lower breakpoints of the histogram. An algorithm is employed to generate one of 3840 (15 integer and 3825 non-integer) compression slopes. Each compression slope is written into the dynamic range compression RAM starting at the computed offset value and is applied to the next field of video.

Abstract: A system and method for determining offset errors between line and pixel coordinates of landmarks in a digitized image generated by an imaging system disposed on a spacecraft and line and pixel coordinates predicted by a mathematical model of the imaging system using landmark geodetic coordinates on the Earth. The system and method use landmarks in symbolic form, such as perimeters of lakes and islands that are stored in a database. A digitized image generated by the satellite-based imaging system is processed to extract a patch of the image containing a landmark. The image patch is then upsampled (magnified). The landmark boundary is processed using a mathematical model of the imaging system to generate absolute coordinates of the boundary pixels, which are upsampled and rasterized to produce a landmark mask.

Abstract: A digital communication system having a paired power amplifier circuit with two closely matched parallel paths including paired power amplifiers, and drift compensation feedback control loops that control the phase and amplitude characteristics of the paired parallel paths. The phase and amplitude characteristics of the paired parallel paths are monitored and matched to each other in real time. Outputs of the paired power amplifiers are summed together in a power combiner having difference and the sum ports. A transmit conditioner includes a lookup table receives a digital input and generates phase angles for each of the parallel paths. The drift compensation feedback control loops correlate signals derived from the difference and the sum ports of the power combiner to control the phase and the amplitude of carriers in the two parallel paths. Statistical and dynamic compensation may be employed to implement the phase compensation.

Abstract: An improved very small antenna terminal (VSAT) dual-beam antenna system for use with user subscriber terminals that communicate with low-earth orbiting and other satellites. In one embodiment, the dual-beam antenna system has two offset Gregorian dual-reflector antennas that each has an ellipsoidal subreflector and a rotatable paraboloidal reflector having a focus in common with a focus of the ellipsoidal subreflector. The rotatable paraboloidal reflector couples energy to and from the ellipsoidal subreflector. An RF feed system couples RF energy to and from the ellipsoidal subreflector. Rotating apparatus rotates the paraboloidal reflector and ellipsoidal subreflector together around an azimuth axis of the antenna. The rotating apparatus independently and simultaneously rotates the paraboloidal reflector about an axis between the paraboloidal reflector and ellipsoidal subreflector which points the antenna at an orbiting satellite.

Abstract: A system equipped with elastic vibration absorbers whose elastic elements, capable of absorbing engine rotational vibrations, are placed and affixed between the supports of the engine main body along the same axis as that of the output axle and the structure for fastening the engine main body to the airframe, and with a vibration absorber-damper equipped with an arm affixed on the support of the engine main body and another arm coupled to the structure for fastening one of the aforementioned elastic vibration absorbers in such a way that these arms, separable and opposing, are positioned and pivoted at the axis of the output axle in a plane perpendicular to this axis, and with a damping member, installed between these arms, for absorbing engine vibrations and recoils occurring in the elastic bodies.

Abstract: Low-cost, high performance access is provided to a group of Internet service providers (ISPs) not convenient to a high volume Internet exchange point through a flexible hybrid terrestrial-satellite Internet communication system. Asymmetric hybrid circuits, that combine satellite and terrestrial backbone technologies, are used to handle asymmetry resulting from low volume requests and high volume responses. A user request is coupled via routers and servers to a point of presence (POP) on a group ISP backbone network. The ISP's backbone couples ISP's POPs to a terrestrial gateway location, which is coupled to a high volume ISP peered with other high volume ISPs. Requests are directed to the high volume ISP through a POP on the backbone of the high volume ISP. Responses from the high volume ISP are routed to a hybrid network provider. Responses packets are translated into permanent virtual circuits (PVC) by a router.

Abstract: A charge control circuit for use with lithium ion satellite batteries that provides for both charge control and cell bypass features. The charge control circuit reconfigures the battery from a series array of cells to a parallel array of cells using switches (that are part of the battery) in order to implement the cell bypass function. The switches are preferably implemented using low resistance mechanical relays to lessen the thermal dissipation of the circuit. The charge control circuit minimizes the amount of current passing through the parallel battery circuit by breaking the battery down into sub-modules for purposes of charging, and using distributed low voltage power supplies for charging. The charge control circuit may also implement sequential charging of the battery along with bus cross strapping to ensure that the satellite electrical bus is always supported by one battery during battery recharging.

Abstract: Two helical resonator filters for applications in wireless and satellite communication systems. The present invention provides for single mode and dual mode microwave filters that employ evanescent waveguide cavities loaded with helical resonators. The structure of the present invention provides for a high Q factor in a miniature package. Two helical resonator filters are well adapted for use in wireless and satellite communication systems. The present invention provides for miniature filters utilizing single mode, high dielectric constant material loaded helical resonators, as well as higher order dual mode helical resonator loaded cavities. Both configurations can be used to realize advanced filters with non-adjacent coupling. The helical resonators may be loaded with high dielectric constant materials or ferrite materials for additional miniaturization and tunability. Either voltage or current tuning may be provided by the single mode and dual mode microwave filters.

Abstract: A software-controlled select and test system for use with a spacecraft. The system reduces the assembly, integration, test time and improves performance of the payload and spacecraft by optimizing the performance using standardized algorithms. The system also reduces the DC power required by the spacecraft, and the thermal dissipation, battery size, solar array size and mass of the spacecraft. This is achieved by optimizing traveling wave tube amplifiers for each channel instead of meeting minimum power requirement over the entire range, wherein most channels have excess power. A serial interface adapter performs the optimization functions via software.

Abstract: A broadband multimedia data distribution system that integrates satellite broadband data derived from a satellite feed that is distributed over a cable TV network with a legacy corporate local area network. The system provides a broadband network overlay with satellite data delivery that integrates with currently available cable television transmission media. The system thus integrates broadband multimedia data distribution, cable TV network distribution, and the legacy network to expand corporate information services. The system thus expands existing network capabilities and avoids replacement or upgrade costs.

Abstract: An extended band, multiple channel multiplexer 10 well-suited for use with satellite communications systems. The multiplexer utilizes a low attenuation, contiguous diplexer 18 containing contiguous diplexer filters 18a to combine two sections 11a, 11b of the multiplexer respectively containing contiguous channel filters 14a, 14b. The multiplexer comprises low attenuation, contiguous diplexer filters 18a tuned in tandem with channel filters 14a, 14b to provide contiguous multiplexing. This approach takes advantage of the constructive interaction between these filters to realize an equivalent contiguous multiplexer. This enables realization of a wide band contiguous multiplexer, which heretofore was impossible to tune. The contiguous diplexer eliminates spurious modes of the channel and diplexer filters, spurious waveguide modes, and out of band interaction between the two portions of the multiplexer. Therefore, tuning of the multiplexer is possible.

Abstract: A programmable digital baseband receiver that processes a large number of signal waveforms and data rates. Programmable elements of the receiver implement coherent signal detection, automatic gain control and decision processing that permits processing of a large number of signal bandwidth efficient QAM and similar signal formats. The receiver comprises a threshold array having a plurality of programmable complex threshold detectors, and selectable decoder tree logic structures embodied in threshold interpreters. Each programmable complex threshold detector is a fully programmable I, Q threshold detector employing programmable I, Q sign threshold detectors that is adapted to the received complex baseband signal constellation.

Abstract: A pre-distortion type linearizer circuit for use in linearizing the performance of power amplifiers such as traveling wave tube and solid state power amplifiers. The linearizer circuit comprises linearizer bridge that includes a phase shifter and a fixed delay in a linear arm, and a distortion generator and an attenuator in a nonlinear arm. The output of the linearizer bridge is coupled through an output amplifier and an output attenuator. The RF output signal from the linearizer circuit is coupled to the power amplifier. A control circuit receives on and off input command signals, and outputs a bilevel telemetry signal that is used as a mode indicator for ground command control. The control circuit adjusts settings of the linearizer bridge, and adjusts gain and attenuation settings of the output amplifier and output attenuator. All circuits of the linearizer circuit may be integrated onto a single alumina substrate, for example.

Abstract: An optical technique (apparatus and method based on the use of power spectral density analysis of spectroscopic multiple angle reflection and transmission data is disclosed. The apparatus and methods measure optical constants (n, k) and thicknesses of single and multilayer films. The apparatus and method provide for index determination with high accuracy (0.00001).

Abstract: A broadband linearizer for use with a power amplifier. The broadband linearizer includes a broadband linearizer bridge, a preamplifier/attenuator, a post amplifier/attenuator, and a control circuit. The broadband linearizer bridge includes a power divider and a power combiner interconnected by linear and nonlinear arms. The linear arm has a phase shifter, a passive equalizer, and a first delay line that are serially coupled together. The nonlinear arm has a distortion generator, an attenuator and a second delay line that are serially coupled together. The control circuit controls respective settings of the broadband linearizer bridge, preamplifier/attenuator and post amplifier/attenuator. The control circuit provides bias circuitry and sends command and telemetry signals to control operation of the broadband linearizer. The broadband linearizer provides for independent, flexible gain and phase control that can mate with different kinds of power amplifiers having various gain and phase performance.

Abstract: A precise, spacecraft camera image navigation and registration system and method wherein a computer 36 on-board the spacecraft and a ground system comprising at least two ground stations precisely compute image navigation and registration data from precise data measurements. The computer on-board the spacecraft (spacecraft control system) uses precise star tracker, gyro, and earth sensor attitude data to precisely point the spacecraft and the camera. The ground system utilizes precise star measurement data from the camera and range data from the ground stations time tagged with GPS precise clock data. The ground system uses these precise measurements to determine precise orbit and attitude coefficients and uploads these coefficient to the spacecraft. The computer on-board the spacecraft uses these precise coefficients to generate and apply precise signals to compensate for slow orbit and attitude variations and register camera images in real time.