Abstract: A solar cell array utilizing geometrically alternating, laterally disposed N-on-P and P-on-N gallium arsenide solar cells is disclosed. Improved array efficiency is achieved by placing adjacent solar cells in substantial contact with each other and eliminating bus connections on the top surfaces. This is accomplished by providing the solar cells with a lateral cross-sectional configuration of a parallelogram with the N-on-P solar cells slanted in one lateral direction and the P-on-N solar cells slanted in the opposite direction. The top surfaces of adjacent, contacting solar cells are electrically connected by extending a connector grid across the top surfaces. Strip connectors are used to join the bases of adjacent solar cells.

Abstract: An improved optical rotary joint is achieved by transmitting information in the form of an optical signal from a part of the de-spun portion outside the rotational axis to create on the spun portion, or vice versa, 360.degree. about the rotational axis, a continuous communication path having a configuration described by a series of overlapping elliptical areas. The detection area on the spun portion is less than that of the detection path thereby providing continuous optical communication with the transmitted optical signal.

Abstract: A pointing apparatus for a dual-spin spacecraft utilizing a first sensor for sensing the time of arrival of an inertial attitude reference as the spinning portion of the spacecraft rotates, and a second sensor for sensing the time of arrival of an index reference which relates the position of the despun portion with the spinning portion. A digital processor estimates the spin rate and phase of the spinning portion from the inertial attitude reference time of arrival, estimates the relative spin rate and phase between the spinning portion and the despun portion from the index reference time of arrival, and estimates the bearing friction bias torque on the motor means which controls the pointing direction of the despun portion of the spacecraft.

Abstract: A spin-stabilized spacecraft has a pair of three-axis accelerometers (A, C) mounted on the spacecraft rotor (10) to provide for self-aligning, enduring and sophisticated navigational capability. A second pair of accelerometers (B, D) is added for redundancy and added sensitivity. Each pair of accelerometers are disposed at diametrically opposed positions on the rotor and respective axes are co-aligned. The orientation of spacecraft angular momentum h is determined by star and planet sensors.Radial alignment of each accelerometer relative to the spacecraft angular momentum is attained by zeroing non-radial accelerometer readings during spacecraft quiescence. Axial alignment is attained during periods of substantially axial thrust by isolating axial translational acceleration by summing readings across an accelerometer pair to cancel rotational, spin-periodic contributions to the readings and time-averaging or otherwise filtering to cancel other non-axial periodic contributions to the readings.

Abstract: An analog surface acoustic wave demodulator includes a calibration section (10) for compensating for distortions, a calibrated frequency sweep (20), a pair of dispersion sections formed by reflective array compressors (24, 26 and 36, 38), a synchronizer (18, 22, 28, 118), a timing signal generator (42) and a temperature compensating readout circuit (40). Frequency domain compensations introduced at the signal input by the calibration section and by the frequency sweep compensate for distortions in time domain at the output of the demodulator. The calibration function applied to the input signal and to the sweep is stored in ROM's (14, 44) in the form of complex digital words. Timing and address generators (12, 42) read the words from the Rom's to complex multipliers (16, 52) such that each symbol period is multiplied by the sequence of words. Each complex digital word corresponds to an amplitude and phase modulation on the incoming signal over a fraction of a symbol period.

Abstract: A suspension system for rigidly mounting an object such as a microwave cavity on a support surface subject to limited expansion and contraction. The object is secured in place by three or more support legs radially spaced from a central reference point and angularly spaced from each other, each leg being specially configured to permit limited radial movement of the underlying surface relative to the object, but to resist relative movement in all other directions. The forces applied to the mounted object, therefore, remain fixed regardless of expansion or contraction of the underlying support surface.

Abstract: A frequency selective surface having a fibrous ceramic material body and a metallic grid on a reflecting face thereof. The body is formed by bonding a mass of silicon dioxide fibers together at their intersection points, as with a fusing agent such as boron nitride in a sintering process, resulting in an array of fibers with cellular porosity intentionally distributed through the body to reduce its density. Other types of ceramic fibers can be used either alone or in combination with the silicon dioxide fibers. The grid is attached to the reflecting surface or deposited thereon. The frequency selective surface finds particular utility in satellite microwave communications satellites.

Abstract: An apparatus and method for launching a spacecraft including a payload and a delivery stage having a rocket engine powered by fluid bipropellant from the earth into a high energy orbit and for recovering the delivery stage are disclosed. By reducing the delivery stage mass, it becomes feasible and cost effective to recover the delivery stage for reuse. Delivery stage mass is reduced by several techniques including transporting the spacecraft and the fluid bipropellant to a parking orbit with the fluid bipropellant in tanks external to the spacecraft; transferring the fluid bipropellant to light weight tanks integral to the spacecraft; controlling the relative flow rates of the fluid bipropellant constituents to the rocket engine during firing of the rocket engine to ensure complete use of both bipropellant constituents; and controlling ascent and descent maneuvers from remote tracking stations.

Abstract: A digital phase frequency discriminator is disclosed that eliminates crossover distortion problem inherent in previous discriminator without a corresponding increase in complexity in the circuit. The discriminator includes four cross-coupled RS latches and a reset gate. The reset gate is coupled to the latches such that additional gate delays are provided to ensure that the output signals of the discriminator reach these full logic amplitude and thereby allow for accurate phase frequency discrimination to occur.

Abstract: A system for generating a sequence of pulses of carrier having individually selectable frequencies employs a pulsed oscillator for providing a single pulse of a carrier signal having a predetermined frequency. The single pulse is applied to a dispersive filter imparting a delay to signals dependent of their spectral content. The relatively broad spectrum of the single pulse is converted by the dispersive filter into a swept frequency pulse of much longer duration than the input pulse to the filter. The expanded signal is mixed with a set of mixing frequencies to provide a set of expanded signals, each of which is then gated to attain spectral portions having desired average values of frequency. The expanded signals are then summed together and applied to a compressive filter which operates in the mirror-image format to the dispersive filter.

Abstract: A fanbeam inversion radar system (100) includes a frequency synthesizer (102) or other transmission means, a fanbeam antenna (104), an orientation sensor/controller (106) and a computer (110). The antenna is adapted for frequency scanning so that fanbeam position data is determined by the computer which controls the variable frequency synthesizer. By scanning a scene with fanbeams for each of a series of fanbeam orientations spanning 180.degree., a two-dimensional image reconstruction can be performed by algorithms well known in image processing fields.By presorting radar returns by delay time (at 112), multiple reconstructed images can be obtained corresponding to different ranges. By mixing (at 122) the synthesizer output with a reference from a local oscillator (120) and "beating" the return against the same reference by means of synchronous demodulators (132), Doppler sorting can provide multiple images with respective relative velocities.The radar system (100) uses serial frequency scanning.

Abstract: A time base converter employs a two position, phase lock loop (40) to write twice orthogonally spaced signals into a split phase memory (34), which in turn can be read out at the timing rate of an incorporating communications system. The converter effectively converts the time base of signals read out of a demodulator (14) to the system time base, thus permitting use of the demodulator in computer based, digital processing systems. Readout of the signals is facilitated by a pair of marker tones f.sub.H, f.sub.L which are introduced into the signal on the upper and lower sides of the input bandwidth. The signal is digitized by A/D converters (28, 30) and the resulting data is employed to drive the phase lock loop. The phase lock loop includes a counter (44) driven by a voltage controlled oscillator (46) which time shares a pair of loop filters (52, 54) that respectively pass the marker tones f.sub.H, f.sub.L.

Abstract: A launcher of cross-polarized electromagnetic radiation is provided with increased bandwidth by inserting a set of axially directed ridges on the interior surfaces of waveguide walls of the launcher for concentrating electric fields of radiations of the different polarizations. A first radiation radiated by a probe in a back section of the launcher waveguide propagates forward into a front section of the launcher waveguide. A second radiation is radiated into the front section by a probe therein, there being a vane disposed in the front section for inhibiting the propagation of the second radiation into the back section. The front section is flared to provide a larger exit aperture at a front end of the front section. A second and a fourth of the ridges are tapered towards the back section to permit a smooth transition in the propagation of the first radiation into the front section.

Abstract: A voltage controlled oscillator is tuned with a network comprising two varactor diodes and two transmission lines. By selecting appropriate values of varactor capacitance and transmission line length and width the overall reactance of the network is such that, when a varactor tuning voltage is varied, the output frequency of the voltage controlled oscillator will vary in an fashion with respect to the tuning voltage. Such a voltage controlled oscillator is gain compensated and exhibits a controlled modulation sensitivity over a range of frequencies. If the required frequency range of the oscillator is known beforehand, an alternate embodiment of the invention may be employed in which one of the varactor diodes is replaced with a fixed capacitor having a suitable value for the desired frequency range.

Abstract: In a microwave resonator, a variable cavity-wall segmentation along the location of a propagational current null is employed for thermal-compensation purposes by utilizing it in conjunction with supplemental mechanisms which operate to counteract thermally-induced variations in the resonator's characteristic geometry. Because dimensional variations at a current null will have minimum impact on resonator coupling parameters, a variably-configured current-null segmentation serves in a minimal-impact fashion to absorb those thermally-induced dimensional variations which occur transverse to the null. Of the three specific mechanisms disclosed for variational counteraction in the typical context of a resonator having both longitudinal and transverse extent with respect to a propagational axis, the first is a thermally-invariant assembly which provides thermal stabilization by inhibiting variations in the resonator's characteristic longitudinal extent.

Abstract: A foam-encapsulated electronic assembly particularly suitable for reworking and repair operations, wherein some of the electronic subassemblies must be removed without damaging them, including a plurality of electronic subassemblies removably inserted into a frame, a release agent interposed between the subassemblies and the frame, and subassembly extraction means attached to the subassemblies prior to encapsulation. Preferably, each subassembly has structural holes such as alignment holes, and a loop of flexible line can be secured through the structural holes and encapsulated within the foam, with a part of the line positioned near or at the surface of the foam so that the line may be located when extraction is desired. The release agent can be a tape or film which prevents the foam from bonding the subassembly to the frame. The assembly also preferably includes foam cutting means between laterally adjacent subassemblies.

Abstract: A probe apparatus is provided for on-wafer testing of an electrical circuit, the probe apparatus comprising a base plate formed from an electrically conductive material, the base plate including top and bottom surfaces; a substrate formed from a dielectric material, the substrate including top and bottom surfaces, the top surface of the substrate being electrically connected to the bottom surface of the base plate; at least one microstrip transmission line secured to the bottom surface of the substrate, the microstrip line including a first end and a second end; a coaxial connector including a center conductor in electrical contact with the first end of the microstrip transmission line; and a needle probe electrically connected to the second end of the microstrip transmission line, the needle probe extending in a direction substantially away from the base plate.

Abstract: Circularly polarized radiation is tapped off from an input waveguide through a input iris into an entry cavity, where it is resolved into two orthogonal linearly polarized components. These respectively proceed along two discrete paths to an exit cavity. In each path six independently tunable resonances--traversed by both direct and bridge couplings--provides enough degrees of freedom for quasi-elliptic filter functions. In the exit cavity the resultants from the two paths are combined to resynthesize circularly-polarized radiation, which traverses another iris to the output waveguide. In one layout, four resonant tri-mode cavities form a rectangular array--with entry and exit cavities at diagonally opposite corners and intermediate cavities for the two discrete paths in the two remaining corners.

Abstract: A method is provided for controlling the utilization of a fluid bipropellant including two respective constituents separately in respective tanks aboard a spacecraft for consumption by a spacecraft rocket engine, comprising the steps of actuating the rocket engine; during the actuation of the rocket engine, providing a flow of bipropellant constituents to the rocket engine in a first proportion; after the actuation of the rocket engine, measuring the amount of at least one bipropellant constituent in a bipropellant tank containing the constituent; adjusting a pressure level within at least one bipropellant tank relative to a pressure level within another bipropellant tank based upon the amount of said at least one bipropellant constituent in a bipropellant tank containing said at least one constituent; after the measuring step, actuating the rocket engine; during the actuation of the rocket engine after the measuring step, providing a flow of bipropellant constituents to the rocket engine in a second proporti

Abstract: A dual mode circular-type waveguide filter (10) has a cylindrical waveguide body (12) separated by septums (16, 18) into a plurality of resonant waveguide cavities (22, 24, 26). Mutually orthogonal electromagnetic fields (37, 81) in adjacent cavities (24, 26) are electromagnetically coupled with each other by an internal coupling element (60) which is mounted on one of the septums (18) and extends into the adjacent cavities. The coupling element comprises an elongate, conductive wire which includes a first portion (62) extending into one of the cavities and forming a magnetic loop, and a second portion (64) extending into the adjacent cavity and forming an electric probe. The coupling element provides an asymmetrical stopband pole (72a) in the frequency response (70) of the filter.