Abstract: A miniature multi-temperature radiometric reference is placed in an intermediate image plane (20) of a thermal imaging optical system in order to correct, in a real-time manner, non-uniformities among detectors (30). The radiometric reference comprises at least two reference elements (10) mounted on a thermolelectric cooler (TEC) (1) which may have several stages (6). The reference elements (10) are mounted on the same platform (3) of the TEC (1). Each element (10) has a surface (11), having a substantially uniform temperature, within the depth of focus at the intermediate image plane (20). All of the radiometric reference surfaces (11) are maintained at different temperatures, which can be simultaneously above and below the ambient temperature. This enables determination of a normalized detector response, and subsequent correction of the response of each detector (30) as a function of temperature throughout the range characterized by the temperatures of the reference surfaces (11).

Abstract: A three-axis accelerometer (4) mounted on board a spacecraft (10) proximate a fuel tank (3) is used to derive an estimate of the amount of fuel (2) remaining within the tank (3). The output of the accelerometer (4) is converted (at 7) to a signal representing the rate of change of the polarity of the acceleration; amplitude information is ignored. This signal is then filtered by bandpass filter (8) or Fourier transform means and applied against an empirically derived function (stored within storage medium 9) relating frequency of oscillation to fuel (2) remaining in the tank (3). The function is stored for three axes; information from one axis is accessed, corresponding to the vector of a perturbing force such as caused by a thruster (11) firing. Some or all of the above described items can be located on board the spacecraft (10) itself. The accelerometer (4) can also be used directly to estimate the force imparted by the thruster, from the expression F=MA.

Abstract: A microwave signal linearizer for a travelling wave tube amplifier (TWTA) provides for simple and flexible adjustment of a predistortion network suitable for independently compensating for a wide range of travelling wave tube amplifier-induced distortions. The linearizer or predistortion network is formed by three divided parallel passive microwave signal channels, the first channel having a coaxial microwave limiter diode network, the second channel having a variable attenuator for adjusting amplitude modulation (AM/AM) non-linearity, and a third channel for adjusting amplitude modulation to phase modulation (AM/PM) non-linearity. Signals directed to the first and second channels are combined in a 180.degree. hybrid network to produce a difference signal which is directed through a difference channel to a 90.degree. hybrid network. The signals through the third channel are directed to the 90.degree.

Abstract: An electromagnetic gun assembly includes a gun barrel, a projectile structure disposed within the gun barrel, and a plurality of bore rider members disposed between the projectile structure and the gun barrel. The bore rider members are dimensioned and arranged to maintain the projectile structure spaced-apart from the gun barrel, restrict lateral movement of the projectile structure relative to the gun barrel, accommodate ablative mass loss, and accommodate static and dynamic gun barrel expansion. Each bore rider member has a tapered shape that includes converging first and second surfaces, the first surface facing the gun barrel, the second surface facing the projectile structure, and the first and second surfaces converging in a direction opposite to a direction of acceleration in which the projectile structure is to be accelerated along the gun barrel.

Abstract: The fill factor in a Pt:Si imager is greatly improved by (1) biasing the reflector plate as a field plate to eliminate the need for an N.sup.- guard ring along the edges of the imaging diodes; (2) reconfiguring the meander channel to use a single meander channel for two columns of diodes; and (3) using a self-demultiplexing output bus structure which requires no separate array space for clocking buses. Two different types of dual-sided meander channel are described.

Abstract: A novel packaging system for VLSI circuits allows low-cost construction and maintenance of complex high density high-performance devices with low power requirements. The devices can be individually created by software means from a small selection of standardizable IC chips by disposing a plurality of chips in leadless chip carriers in a mosaic on a substrate, and configuring them by software to selectively communicate with other chips of the mosaic or even to individually change their operating function. The immediate juxtaposition of the chip carries in the mosaic eliminates transmission line data skew, and also allows considerable savings in chip space and power requirements by dispensing with interconnection drivers, receivers and bonding pads.

Abstract: A programmable voltage offset circuit (PVOC) (1) comprises a temporary latch memory (7); a latch disable circuit (5) which selects that PVOC (1) among several such circuits which may be simultaneously present on the same semiconductor chip; a resistor array (3); and a programmable nonvolatile memory (37). The desired voltage offsets V(OFFSET)s are temporarily produced in an iterative manner using the latch memory (7). Quasi-permanent voltage offsets V(OFFSET)s are then programmed using the nonvolatile memories (37), each of which typically comprises an EPROM (39). Application of an avalanche voltage V(STORE) to a PFET (43) portion of the EPROM (39) causes the PFET (43) to avalanche, thereby selectively programming the nonvolatile memory (37), depending upon the status of a signal supplied from the latch memory (7).

Abstract: The relative intensity of the transmit beam and the local oscillator beam in a ladar diplexer can be continuously adjusted during operation by using a rotatable retardation plate with a slightly inclined "C" axis to turn a polarized laser beam into a composite beam having two components polarized in mutually perpendicular directions. The relative intensity of the components is adjustable by varying the inclination of the "C" axis. The composite beam is applied to the same polarizer element normally used to separate the return signal from the transmit beam. The polarizer acts as the beam splitter which separates the local oscillator beam from the transmit beam. The described configuration also saves one beam splitter and allows improved packaging and alignment of the diplexer.

Abstract: A layer of HgCdTe (15) epitaxially grown on a crystalline support (10). A single crystal CdTe substrate (5) is first epitaxially grown to a thickness of between 1 micron and 5 microns onto the support (10). Then a HgTe source (3) is spaced from the CdTe substrated (5) a distance of between 0.1 mm and 10 mm. The substrate (5) and source (3) are heated together in a thermally insulating, reusable ampoule (17) within a growth temperature range of between 500.degree. C. and 625.degree. C. for a growth time of between 5 minutes and 13 hours. In a first growth step embodiment, the source (3) and substrate (5) are isothermal. In a second growth step embodiment, the source (3) and substrate (5) are non-isothermal. Then an optional interdiffusion step is performed, in which the source (3) and substrate (5) are cooled within a temperature range of between 400.degree. C. and 500.degree. C. for a time of between 1 hour and 16 hours.

Abstract: A method for determining whether a perceived target is acceptably close to a model target. The perceived target is first segmented using a relaxation based procedure. Structural features from the perceived target are extracted by producing a compact one-dimensional description of the perceived target's boundary. Said structural features are classified by using string-to-string matching, wherein one of two symbolic strings is a representation of the compact one-dimensional description of the boundary of the perceived target, and the other of said two symbolic strings is a pre-stored representation of the model target. The string-to-string matching entails measuring the distance between the two strings based upon deletion, insertion, and substitution of symbols from one string to the other. Performing the string-to-string matching measures how closely local structural features of the perceived target resemble local structural features of the model target.

Abstract: Mechanical oscillations of a mechanism containing a stepper motor, such as a solar-array powered spacecraft, are reduced and minimized by the execution of step movements in pairs of steps, the period between steps being equal to one-half of the period of torsional oscillation of the mechanism. Each pair of steps is repeated at needed intervals to maintain desired continuous movement of the portion of elements to be moved, such as the solar array of a spacecraft. In order to account for uncertainty as well as slow change in the period of torsional oscillation, a command unit may be provided for varying the interval between steps in a pair.

Abstract: A repeater for local area networks of the MIL-STD-1553B type allows extension of the LAN to remote terminals. The repeater terminates the dual LAN buses and interfaces them with a single remote bus. Normally, the repeater is transparent to all traffic in the receive direction from both buses of the LAN to the remote terminal. In response to appropriate command words from the LAN, however, the repeater automatically switches direction at the correct time to transmit traffic from the remote terminal to the active bus of the LAN as called for by the LAN protocol, and then switches back. Safeguards are provided to reinitialize the repeater if a message failure occurs or the remote terminal fails to respond to a command word.

Abstract: A telemetry data processor for processing extremely high bandwidth data such as that associated with telemetry from spacecraft. A demultiplexer (1) distributes the data onto several channels (CHl through CHn), each comprising a (preferably split-cycle synchronous) processing bus (BUSl through BUSn). Processing can occur on each of the n buses simultaneously. Several processor modules (P boards) are directly coupled to each processing bus, with each P board directly coupled to two buses. Several memory modules (M boards) are directly coupled to each processing bus, with each M board directly coupled to two buses. The functions and architectures of the P boards and M boards are described, along with those of D boards (disk controller modules) and I boards (modules for interfacing the telemetry data processor with its outside environment, which may comprise local area networks, peripherals, gateways, etc.).

Abstract: Consolidation of active and passive detectors (26, 28, 34) on a single coldfinger (20) in a dewar (10) is made possible by interposing between the detectors (26, 28, 34) an electromagnetic interference shield (64, 68) which acts as a waveguide filter blocking any interfering frequencies. The waveguide is formed by a pair of spaced interleaved shields (64, 68) one of which (64) is associated with the dewar envelope and is externally grounded, and the other of which is associated with the coldfinger (20). Photons which penetrate through the waveguide (64, 68) are deflected to the outside of the dewar (10) by a flanged narcissus shield (40) surrounding the passive detector (34).

Abstract: The disclosed invention is a device and method for optimizing the weight and/or the heat transfer (conduction) capability of a heat transfer cylindrical sleeve. The sleeve is designed to fit around a cylindrical heat source. One particular application for this invention is where the heat source is a battery such as a metal gas battery in a satellite (where weight savings is important). Two sets of functional relationships are generated showing the relationship between the thickness of the sleeve at its top and bottom, an "area factor" (which is directly proportional to its heat transfer capability), the material thermal conductivity, and its volume per unit length (which is directly proportional to its weight). One can specify the desired heat transfer capability of the sleeve and optimize (minimize) its weight. Conversely, one can specify the desired weight for the sleeve and optimize (maximize) its heat transfer capability.

Abstract: A programmable voltage offset circuit (PVOC) (1) comprises a temporary latch memory (7); a latch disable circuit (5) which selects that PVOC (1) among several such circuits which may be simultaneously present on the same semiconductor chip; a resistor array (3); and a programmable nonvolatile memory (37). The desired voltage offsets V(OFFSET)s are temporarily produced in an iterative manner using the latch memory (7). Quasi-permanent voltage offsets V(OFFSET)s are then programmed using the nonvolatile memories (37), each of which typically comprises an EPROM (39). Application of an avalanche voltage V(STORE) to a PFET (43) portion of the EPROM (39) causes the PFET (43) to avalanche, thereby selectively programming the nonvolatile memory (37), depending upon the status of a signal supplied from the latch memory (7).

Abstract: There is provided a digitally controlled first order hold circuit and waveform synthesizer for digitally controlling the representation of a function over an approximation interval. In accordance with the operation of the invention, the first order hold circuit and waveform generator receives a digital data input signal which contains initial condition data, up/down data, and slope data for the approximation interval. The initial condition data is loaded into an up/down counter which is incremented using counting data at a rate depending on the value of the slope data and in a direction depending on the value of the up-down data. In order to minimize delays arising from data acquistion, two frequency synthesizer circuits are provided such that one frequency synthesizer provides counting data while the other frequency synthesizer receives slope data. During alternating intervals, the other frequency synthesizer circuit provides counting data while the other circuit receives slope data.

Abstract: The present invention is a demodulator for demodulating an unsymmetrical QPSK signal (1), i.e., one in which the amplitudes of the I and Q channels are different, and the I and Q channels have been modulated by signals having differnt bit rates. Analog versions of the I and Q modulating baseband signals are first extracted from the carrier. Each baseband signal is then subjected to a bit-rate-matched low pass filter (23, 13). The channel having the higher bit rate is subjected to a delay (32) to time-align the two baseband signals. The time-aligned filtered signals are then amplified by amplifiers (22, 12) having unequal gains that are preselected to substantially equalize the amplifier (22, 12) outputs. The amplified time-aligned filtered signals are then subjected to a phase error (E) generating means (15, 25, 16, 26, 34). The phase error (E) is passed through a loop integrator (38) and a VCO (30) and back to the baseband signal extracting means to complete a phase lock loop.

Abstract: Coolant gas pumped into the inner flask (3) of a cryostat dewar (2) causes an unwanted electrostatic charge on the inner surface (34) of the inner flask (3). This electrostatic charge can put an unwanted noise into the electrical output from an electromagnetic detector (16) cooled by the cryostat (2). The invention comprises a foraminous metallic screen (7) interposed between coolant coils (5) of the cryostat (2) and said inner surface (34). The screen (7) siphons off unwanted electrostatic charge from said surface (34) while allowing coolant to contact said surface (34) and thus allow cooling of the detector (16).

Abstract: A hot gas control system includes a pressure vessel defining a chamber in which is disposed a body of solid propellant material that has a leading portion and a trailing portion. A first layer of the body of solid propellant material extends between the leading portion and an intermediate region of the body of solid propellant material, and a second layer extends between the intermediate region and the trailing portion of the body of solid propellant material. The first layer is composed of a first propellant composition that produces a relatively clean gas, and the second layer is composed of a second propellant composition that produces a relatively less clean gas.