Abstract: A method for passively stabilizing the attitude of a spinning orbiting body subject to orbital precession to maintain the spin axis orientation of the body essentially fixed and stable relative to the orbital plane. The preferred embodiment comprises selecting a body mass geometry and orbital parameters, including an orbit inclination, an orbital rate and a rate of regression of orbit line of nodes, so that the precessional motion of the body and the orbit are equal and opposite in direction and locating the spin axis of the body in a plane containing the north axis of the body and the orbit normal and between the north axis and the orbit normal, so that the gravity gradient precession of the spin axis equals the regressional motion of the orbit normal to produce a planar equilibrium configuration.

Abstract: An improved method for designing sector beam antennas. The method is used to provide a sector beam antenna having a feed horn with a cross sectional azimuth dimension and a cross sectional elevational dimension which are optimized to irradiate a reflector to transmit a signal over a coverage area such that the gain-area-product of the transmitted signal is maximized.

Abstract: A low noise coaxial microwave window of particular utility in hermetic and high power applications, having a metallic center conductor, a metallic outer support, and a ceramic support brazed between the two conductors. The brazed joints are specially prepared to have a series of layers and sublayers extending from the ceramic to the metal, as follows: ceramic, cermet, cermet-nickel alloy, copper-nickel alloy, copper, braze metal, and metallic piece. The nickel content of the cermet-nickel and copper-nickel alloys is limited so that the alloys are non-magnetic. The nickel-containing alloys assist in bonding the copper layer to the cermet in a reliable, reproducible fashion, but control of the nickel content avoids microwave intermodulation effects. Where the window separates a vacuum from another medium, the surface of the support contacting the vacuum is formed from at least two noncoplanar segments to eliminate the possibility of multipacting. The same techniques are used in waveguide microwave windows.

Abstract: A test and measurement system for space satellite antennas which includes frequency synthesizers which are capable of shifting from frequency to frequency at high speeds with precision accuracy to provide source and reference frequencies with which the antennas may be tested; a transmitter utilizing one of the frequency synthesizers to generate test signals; an optional power monitor receiving antenna; a non coherent receiver utilizing the other of the frequency synthesizers to generate local reference frequency signals; high speed electronic switching networks connecting the various antennas to be tested with the receiver at the receiving antenna; a network for converting received signals to digital signals and storing those signals; and a computer system for controlling the transmitter, the receiver, and the switching systems, and the data converting and storage network.

Abstract: A device for transforming N-Frequency Division Multiplexed (FDM) channels (21) of modulated signals into individually accessible streams (46) of demodulated data employs a Fourier transform processor (10) to transform the N-FDM channels into a single, TDM (Time Division Multiplex) channel of data, a single demodulator (12) for demodulating the single TDM channel and a demultiplexer (14) for demultiplexing the single channel of TDM data. The symbol segments of the N-FDM channels are synchronized with each other using an error signal generator (78) and a dither technique in which a symbol window is shifted back and forth to determine whether the symbol segments are early, on time or late. In a preferred form, the demodulator and error signal generator are implemented using digital techniques.

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 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: 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: 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: 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 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 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 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 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.