Abstract: A thermal control surface for a spacecraft includes flexible OSR tiles (310) 0.0015 inches thick. Each tile includes a transparent substrate (312) with a reflective second surface (314), such as a coating of silver. The front or space-facing side is coated with a transparent, electrically conductive layer (316) of indium oxide (IO) or indium-tin oxide (ITO), which laps over the edges of the OSR tile, and is in electrical contact with the reflective coating.The IO or ITO coating, or a separate electrically conductive coating (610) such as nichrome, forms a protective coating for the reflective surface, and maintains contact with the front surface of the tile. The IO or ITO layer (316) in conjunction with the back side coating provides front-to-back electrical conduction. The OSR is mounted to an electrically conductive surface (110) of the spacecraft, such as an aluminum or graphite-fiber-reinforced epoxy resin, by a sheet of transfer adhesive (410).

Abstract: In a monopulse radar processor, the usual sum (s) and difference (d) signals are manipulated to produce two other signals (s+ad and s+bd, in which a and b are constants). The phase of each of these derived signals with respect to the sum signal is then determined. The real part of d/s and, if desired, the imaginary part of d/s are calculated from these measured phase angles. The real part of d/s is the conventional output from a monopulse processor.

Abstract: A spacecraft uses monopropellant arcjets for velocity change such as for north-south stationkeeping. It has been discovered that, while an arcjet cannot be modulated by pulsing the fuel supply, the amount of thrust can be varied by modulating the power applied to the arc, without extinguishing the arc. While the specific impulse (I.sub.SP) of the arcjet is thereby reduced from the maximum I.sub.SP of which the arcjet is capable, the resulting I.sub.SP may still be larger than the combined I.sub.SP of an unmodulated arcjet in conjunction with a modulated chemical thruster in a typical scenario. According to the invention, attitude control is provided in conjunction with north-south stationkeeping or other velocity change by, in response to an error signal generated by an attitude control system, modulating the arc power(s) of an arcjet thruster(s), which provides the velocity change. The arc is not extinguished during the stationkeeping maneuver, but is varied in magnitude.

Abstract: A communications system (FIG. 7) couples together a number of entities or communications devices 710 by means of alternating stages (722, 726) of crossbar switches (712, 716) and stages (724, 728) of stride extender coupler circuits, which are preferably in the form of modules (714, 718), together with a final stage (730) of cross-connecting "termination" circuits or modules (720). The system can be expanded in performance capability (FIG. 8) by adding further stages (822, 828) of crossbar switches and stride extender coupling circuits or modules.

Abstract: A sigma-delta (.SIGMA..DELTA.) analog-to-digital converter (ADC) accepts band-limited analog signals, and subtracts an analog replica of an output pulse- or amplitude-density modulated (ADM) signal therefrom to produce an error signal. The error signal is processed by an analog filter or resonator with a nondelayed forward path and a tapped nonaccumulating delay line, and summed feedback and feedforward weights coupled to the taps, to thereby produce a resonated signal. An ADC processes the resonated signal, and produces the ADM signal. The ADC undesirably produces quantization noise. A digital-to-analog converter (DAC) noiselessly converts the PDM signal into the analog replica, to aid in forming the error signal. In a particular embodiment of the invention, the resonator includes a recursive analog transversal filter with delays and linear weighting elements for linearity and high operating speed. The ADC may be in a high-speed system such as a radar.

Abstract: A radar system simultaneously transmits first and second signals toward a target at higher and lower carrier frequencies, respectively. Each carrier is phase-modulated by a set of pulses. The first set of pulses is dispersed in time, and the second set of pulses is mutually complementary thereto. The transmitted pulses are reflected by the target and received simultaneously. The received signals are processed separately by Doppler filtering. Each Doppler-filtered return is code-matched filtered, and the filtered signals in each Doppler channel are summed with the corresponding Doppler-and-code-matched-filtered signals originating from the other transmitted frequency, to form range signals. Each range signal has its main lobe enhanced and its sidelobes suppressed by the summing of the code-matched-filtered mutually complementary echoes.

Abstract: An improvement in monopulse radar achieves nulling of multiple mainlobe jammers while maintaining the angle measurement accuracy of the monopulse ratio by using multiple simultaneous beams, thereby obtaining the additional degrees of freedom necessary for cancelling more than one mainlobe jammer (MLJ). The beams are placed one null beamwidth apart in order to maintain orthogonality. The MLJs are nulled in the orthogonal direction of the angle estimate giving undistorted monopulse ratios.

Abstract: A fault tolerant communication arrangement, for switching parallel N-bit information among a plurality of stations, includes an M-bit crossbar switch, where M is greater than N by a number S of supernumerary or spare bit paths. At each station, an interface unit monitors for errors, and when an error is identified to a bit in the transmission path, routes the defective bit to one of the spare bit paths. All stations reroute data from the defective bit path to the same spare bit path. Error coding information is generated at the transmitting interface unit, and transmitted over some of the supernumerary bit paths, and when the number of defective bit paths reduces the number of available supernumerary bit paths to zero, the bit intensity of the error coding is reduced, to free additional supernumerary paths. In a system in which some of the stations include memory, a failure of a memory bit at a particular address is, in effect, a failure of that bit in an overall transmission path.

Abstract: A power supply system for thrusters (e.g., arcjet thrusters) in a spacecraft system comprises lightweight, redundant power supplies that share the power distribution function to the thrusters. Each power supply comprises a plurality of parallel-connected power supply subunits of which the combined power output capability exceeds the required maximum power demand by at least one subunit capacity for each arcjet thruster in the system. Each power supply subunit comprises a lightweight, high-frequency, soft-switching power supply. For arcjet systems comprising arcjet thrusters that do not operate simultaneously, relays are employed to switch between thrusters.

Abstract: A satellite communications system includes a feed array and reflector receiving antenna coupled to a dual-mode network, for generating two channels, with independent signals representing two beams, one for each channel. Each output channel of the dual-mode network contains redundant information relating to a plurality of information channels. In the absence of an interfering signal or intrusion, the combined signals are amplified and block frequency-converted, then de-multiplexed into separate channels, which are each applied through selection switches to a transmitter multiplexer for retransmission. An alternate signal is tapped from each of the two received signal channels, phase controlled, and combined, to produce a combined signal representing a receive antenna beam with a null controllable in position in response to phase. The combined signal is demultiplexed into separate information channels.

Abstract: A 3-axis stabilized spacecraft includes roll and yaw magnetic torquers, and a momentum wheel oriented with its spin axis orthogonal to, and pivotable about, the roll axis. Roll control may be applied by pivoting the wheel. Secular increases in pivot angle may result in loss of control authority when the mechanical limits of the pivot are reached. The pivot angle is sensed, and an unloading control loop is closed, by which magnetic torquers are energized to torque the spacecraft, to return the pivot angle toward zero. The unloading control loop includes a bandpass filter, which eliminates constant components of pivot angle offset. This prevents the unload control loop from attempting to maintain the pivot at a position in which the wheel axis is offset from the desired normal to the orbit plane. Consequently, the magnetic torquers do not expend system energy attempting to maintain an undesirable attitude.

Abstract: Equipment support and thermal radiation panels for a spacecraft include a transverse header heat pipe and a set of a plurality of "spreader" heat pipes each including an elongated longitudinal portion and an "L" portion lying in thermal contact with the header heat pipe. The elongated longitudinal portions of the spreader heat pipes are spaced apart and mutually parallel. A further set of spreader heat pipes, similar to the first set, is provided. At least part of the elongated longitudinal portion of each further heat pipe is physically parallel, and in thermal contact, with a heat pipe of the first set, and the "L" portions of the further heat pipes are in thermal contact with a second header heat pipe. A make-break thermal joint juxtaposes a header heat pipe of each of two panels lying in different planes.

Abstract: To reduce the time required to build spacecraft, and to reduce costs, the spacecraft are members of a set of spacecraft. Each member has the same structural members, such as panels, but different members of the set are elongated by multiples of an increment such as five inches. The structural panels of larger members of the set are elongated in the longitudinal direction, to provide more surface area for mounting payload, and to provide more heat rejection surface. The propellant tank(s), which may be fuel and oxidizer tanks, are spherical in the shortest members of the set, and are increased in length by addition of cylindrical sections, to provide greater volume in larger members to thereby provide longer operating life. Similarly, the solar panels, heat pipes and the like may be elongated.

Abstract: In an ammunition fuzing system, a fuze setter is inductively coupled with an electronic fuze incorporated in the projectile of an ammunition round being fed to a rapid-fire cannon to transmit power supply charging energy and fuze-setting data thereto. A detonation counter is incremented at a high counting rate to accumulate a projectile flight time count indicative of the fuze-setting data. A conformation signal is transmitted to the fuze setter for determination that the flight time count acceptably corresponds to the setting data. Upon projectile launch, the detonation counter is decremented at a low counting rate and functions the projectile warhead when decremented to zero.

Abstract: An FFT-like array architecture (500), for use on the Doppler filters of a radar system, includes a plurality of stages (505, 506) of weighted butterflies (501, 502, 503, 504), in which each butterfly is provided with four weighting multipliers (410-416). The weights (W1, W2, W3, W4) of the multipliers of the array are determined by an iterative process in which the input and output signals are selected, the input signals are applied to the array, and the actual output signals are compared with the desired output signals to produce error signals. The error signals are backpropagated through the array, to correct the weights. The input signals are again applied, and the corrected output signals are again compared with the desired output signals to produce new error signals, which are again backpropagated to correct the weights. This procedure is used iteratively until the array "learns" the weights which give the desired output signals.

Abstract: An antenna subject to standoff sidelobe barrage jamming exhibits a null in its sidelobe structure at a selectable elevation angle for all azimuth angles of interest. The null can be set to the elevation angles corresponding to the angle of the standoff jammers. The null is generated with the aid of an interferometer associated with each column of the antenna array. The interferometer produces a pattern having a plurality of lobes. The interferometer pattern is phased and amplitude adjusted relative to the antenna pattern of its associated column line array so that subtraction of the patterns causes one or more sidelobe of the antenna pattern to be at least partially canceled. An azimuth beamformer combines the elevation patterns of a plurality of column arrays, each connected to its own interferometer, to produce a pencil beam with a sidelobe structure exhibiting a null at the particular elevation angle.

Abstract: A pitch momentum stabilized spacecraft includes an earth sensor for generating roll signals. The roll signals are applied to torquers for proportional (P) or proportional-integral PI control of roll and yaw. According to the invention, the sensed roll signals are bandpass filtered at the orbit rate, phase adjusted and applied to the roll and yaw torquers for closing a high gain degenerative feedback loop at the orbit rate, which reduces orbit-rate components of roll and yaw. A second bandpass filter at the second harmonic of the orbit rate is also connected to the earth sensor, for producing second harmonic signals, which are phase controlled and summed with the fundamental orbit rate signals, for degeneration of attitude perturbations occurring at twice the orbit frequency.

Abstract: An antenna array (10) includes a plurality of antenna elements (12), each of which is associated with a transmit-receive TR module (14). The antenna elements and their associated TR modules are grouped into sets, which in the illustrated embodiment are sets of four. Each set of four TR module/antenna elements is associated with one phase and gain controller (18.sub.X), which is part of a distributed phase and gain controller. The beam direction is commanded by a central radar control computer (RCC) (22), which transmits beam direction and other information to all the separate phase/gain controllers. Each separate phase/gain controller accesses local memory to obtain data relating to the location within the array of those antenna elements which it controls. Each phase/gain controller then calculates the necessary phase shift for each antenna element it controls, taking into account the phase and gain errors associated with the TR module associated therewith.

Abstract: The invention lies in a support transition which is affixed to a spacecraft for supporting the spacecraft on a support ring of a booster or launch vehicle. The transition is in the general form of a ring defining a longitudinal axis parallel to the axis of the spacecraft and the booster. The transition has a circular end adapted to mate with the booster support ring, and a polygonal end adapted to mate with the spacecraft, and makes a smooth transition between ends. The circumference of the transition, at any cross-section transverse to the longitudinal axis, is constant. The transition is advantageously made of a composite material such as fiber-reinforced solidified liquid or carbon-fiber reinforced resin. In a particular embodiment, the polygonal end is a square rectangle, with four straight sides and rounded corners. In a set of spacecraft, the transition remains the same size.

Abstract: A vibration suppression system senses undesired mechanical motion of a body, and continuously drives a proof mass actuator system to reduce disturbances. An inertial or relative displacement sensor is processed to determine the energy content of the motion, and a correction signal is generated which is summed with the actuator drive signal to minimize the sensed motion energy. The position of the proof mass is sensed, and processed by differentiating and scaling, and the processed proof mass position signal is also summed with the actuator drive signal. The system causes the proof mass actuator loop natural frequency to tend to track the frequency associated with the maximum vibrational energy.