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: 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 starting circuit for providing a high-voltage pulse for igniting an arc in an arcjet thruster includes a resonant capacitor for storage of the energy required to generate the high-voltage pulse. The capacitor is resonantly switched with a small resonant inductor which, in turn, resonates with a high-voltage cable capacitance, generating a high-voltage pulse via a step-up transformer to the arcjet thruster for igniting the arc. Advantageously, the transformer turns ratio is minimized, thus minimizing the required transformer size and weight; and the high-voltage pulse is isolated from the arcjet power supply semiconductor devices.

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: 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: 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 unified spacecraft attitude control system includes a memory aboard the spacecraft, in which a linear transformation matrix [.alpha.] is stored, which includes information identifying pseudo-complementary pairs of thrusters, and the characteristics of each pseudo-complementary pair. During each control cycle of the spacecraft attitude control system, the error signal is multiplied by a gain representing a desired slew rate to form pulse-width signals {pw} for the pseudo-complementary paired thrusters. An augmented pulse-width vector matrix {PW} is formed by transformations, to eliminate negative values of pulse width. The actual thruster pulse widths {.DELTA.t} are calculated as {.DELTA.t}=[.alpha.]{PW}. The thrusters are energized by limited values of {.DELTA.t}.

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.

Abstract: According to the invention, a two-dimensional active antenna array, operating at a number of different frequencies, is used to achieve directivity in two orthogonal planes, thereby providing a more constrained beam "footprint". The array includes a larger number of amplifiers than a line array, thereby increasing the total power which can be combined in space, to further increase the power in the footprint. For transmission, each of the information channels at a different frequency is applied, as in the prior art, to a different power divider array, each of which may be on a separate board. Power-divided signal from each of the information signal channels is applied to an N-input, M-output power combiner arrangement or board, which combines the signals. Each N.times.M power combiner arrangement includes N.times.M nodes. Each node represents the junction or crossing of one input and one output signal transmission path.

Abstract: An inductor uses high temperature superconductors in order to obtain high Q for high frequency operation. The superconductors are applied as thin films to substrates. In some embodiments, superconductor thin films are applied to opposite sides of the same substrate. Superconductive thin films are applied outside the magnetic field establishing superconductive thin films in order to shield against leakage of the magnetic field beyond the inductor. The inductor is connected to a capacitor to realize a resonant circuit used in a power conversion system.

Abstract: An apparatus and method for fastening together spacecraft panels includes the use of fastener pairs, one of which has preformed therein an aperture which is larger in diameter than the body of a tolerance takeup piece which is to pass therethrough. A washer which takes up the clearance is adhesively fastened to one of the fastener halves, and allowed to cure while the panels are in their desired position. Thus, a high-tolerance mating pair can be finalized in position at a late state in fabrication, without undesirable drilling or reaming. In a first particular embodiment, a flat washer, having an inside diameter which closely fits the corresponding bolt, is adhesively fastened over the preformed oversize aperture of a fitting.

Abstract: A local area network uses standard ANSI FDDI LAN concentrator stations and a first set of mutually reverse-direction data buses or loops, in conjunction with an additional set of mutually reverse-direction data paths. The standard FDDI protocols when applied in the context of the particular connections of the concentrator station operate in the event of a break in the data path terminating at an input or output port, to reconfigure the station to interconnect the buses in a manner which routes data around even multiple breaks in the buses, to thereby maintain communication integrity.

Abstract: An inorganic paint suitable for harsh environments, and particularly suitable as a thermal control coating for spacecraft, includes a mixture of 50% or more dry weight barium titanate (BaTiO.sub.3) pigment powder with a binder of an alkali metal silicate such as potassium silicate K.sub.2 SiO.sub.3 or sodium silicate Na.sub.2 SiO.sub.3. Instead of alkali metal silicate binder, a glass frit may be used, which when fused binds the pigment to the substrate. The coefficient of thermal expansion of the pigment is about 12.times.10.sup.-6 /.degree.C. The coefficient of thermal expansion of the paint is moved toward the coefficient of expansion of the substrate by addition of a filler consisting of magnesia to increase the paint's coefficient of expansion, or alumina and/or silica to decrease the paint's coefficient of expansion. The paint survives harsh environments, ultraviolet radiation and a fluence of charged particles, while maintaining a low solar absorptance and high thermal emittance.

Abstract: Cylindrical battery cell vessels are coupled together in plural sets by pairs of half-shell sleeves. The sleeves conduct heat preferentially in an axial direction. Each sleeve set is mounted onto a heat rejection plate for direct radiation to space. Each satellite of a set of spacecraft has a North and/or South-facing region for mounting the heat rejection plates of the requisite number of cells. Each plate may be fitted with an optical solar reflector (OSR) for reflecting insolation, and for radiating heat energy.

Abstract: A satellite attitude control system is usable in the absence of any inertial yaw attitude reference, such as a gyroscope, and in the absence of a pitch bias momentum. Both the roll-yaw rigid body dynamics and the roll-yaw orbit kinematics are modelled. Pitch and roll attitude control are conventional. The model receives inputs from a roll sensor, and roll and yaw torques from reaction wheel monitors. The model produces estimated yaw which controls the spacecraft yaw attitude. The model further produces estimates of the constant component of the disturbance torques for compensation thereof.

Abstract: A radar system includes a doppler/pulse compressor/range sidelobe suppressor filter bank (40), which separates received echo signals according to their frequency spectrum into doppler channels, and within each doppler channel performs pulse compression for reducing the duration of the received signals, and also performs range sidelobe suppression, for improving range resolution. It may be advantageous to perform certain types of processing in the time domain, such as determination of spectral moments for estimating velocity spread, mean closing velocity, and reflectivity of a diffuse target such as a weather phenomenon. An inverse (frequency-to-time) transform (50) is performed on the signals produced by the doppler/pulse compressor/range sidelobe suppressor filter bank (40), to produce a reconstructed version of the received signals. In these reconstructed signals, the pulses are compressed, and range sidelobes are reduced. The time-domain processing (62) is performed on the reconstructed signals.

Abstract: A recursive Radon video transform processor, for detecting signal responses from objects to be recognized, generates a special manifold of the response data for Radon transformation of the stored data before operation thereon by a subsequent enhancement process, prior to display or other utilization. Each Cartesian data point contributes to multiple Radon transforms, so that the recursive Radon transform video implementation only processes the newest and oldest lines of data to update the transform for a given sliding window in the data manifold. For a data line of fixed length .rho., and with each of a set of N separate angular subprocessors operating, the pixel X value of the first and the last data rows are offset by a window size (w=x* tan .theta..sub.i), where .theta..sub.i is the transform angle for a particular subprocessor, as determined by a desired resolution, so that window size variations are implemented by a programmable change in time delay.