Abstract: A cascadable seventeen-bit self-testing comparator (20) is produced on a twenty-four pin GAL.RTM. 39V18 generic array logic chip by so interconnecting the data pins (1-17) with the logic macro cells (24a-h, 26a-i), and configuring the macro cells, that any data applied to the pins is registered in the macro cells (24a-h, 26a-i) upon pulsing the clock (35), and any exact coincidence of subsequent data with the registered data causes one of the macro cells (26j) to generate a match-indicating output (61).

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: The efficiency of a metal silicide infrared detector (10) in greatly enhanced by depositing on the substrate (14) a stack (30) of alternating metal silicide (12,24) and silicon layers (22). The metal silicide layers (12,24) are connected to each other and to a contact pad (20) in the substrate (14) by a metal silicide deposit (32) on one side of the stack (30) and the silicon layers (22) are connected to each other and to the substrate (14) by a silicon deposit (34) on another side of the stack (30). The stacking of layers is made possible by depositing the silicon layers (22) at a rate of 1 .ANG./sec or less in a vacuum of 10.sup.-9 torr or better at a temperature of about 250.degree. C.

Abstract: Information-theoretic notions are employed to establish the predictability of a random number generated from a circuit exhibiting chaos in order to obtain a number from a sequence of numbers with a known level of randomness and security. The method provides a measure of information loss whereby one may select the number of iterations before or between bit sampling in order to extract a secure pseudo-random number. A chaotic output is obtained by use of a sample and hold circuit coupled in a feedback loop to a variable frequency oscillator, such as a voltage controlled oscillator circuit, and operated with a positive Lyapunov exponent. A source signal generator, such as a periodic wave generator, provides a driving signal to the sample and hold circuit.

Abstract: Process for increasing the density of an article. A coating containing boron nitride and carbon is applied to the article to form a coated article. The coated article is encapsulated. The encapsulated article is subjected to hot isostatic pressing. The coating reduces interaction between the article and the encapsulant during the hot isostatic pressing. The carbon is present in the coating in an amount up to about 30% by weight of the total boron nitride and carbon in said coating.

Abstract: One-dimensional sun sensing and angle measurement assemblies are deployed with substantially totally overlapping fields of view on a plane of a spacecraft body to protect sensors within a protected angular area of the plane, each of the analog sun sensors generating a signal indicative of incident sun along one axis and the presence of sunlight along an orthogonal axis thereto in the common plane. The sensors together generate an indication of the orientation of the sun relative to a target field of view which is a protected area. In an alternative embodiment, a digital sun sensor assembly is provided consisting of two or more independent digital channels and employing a slit aperture cooperating with a plurality of photocells laid out in a gray coded pattern. The digital device produces digital signals indicating relative position relative to axes in a plane.

Abstract: A superior release coating for glass-encapsulated ceramic or ceramic composite bodies in hot isostatic pressing processes is obtained by mixing boron nitride with up to about 30% by weight of carbon.

Abstract: The angle of divergence of a laser beam (29) is controlled without significant variation of beam power by using a movable corner cube (18) to vary the length of the optical path of a noncollimated beam (12) so as to present a beam of varying diameter to a telescope lens (26). In a second aspect of the invention, the beam is made insensitive to vibration of the corner cube (18) by covering a portion of its beam-receiving face with a second reflector (32) which causes the beam to make a second pass through the corner cube (18) in a parallel but opposite direction therey cancelling any beam displacement caused by the vibration of the corner cube (18).

Abstract: A heater for a composite structure (2) is integrally formed as part of the structure (2) itself. The structure (2) comprises a layer of conductive fibers (30), such as a carbon felt mat, embedded in a nonconductive matrix (31). Electrodes (11, 12) inject an electrical current through multiple paths (15) through the conductive fibers (30), whereby the fibers (30) convert the electrical current to heat energy. Thus, the fibers (30) serve the dual roles of structural support to the composite structure (2) and heat converters. The composite structure (2) can be a portion of or an entire paraboloidal antenna reflector (6), in which case the heater of the present invention prevents and removes ice and snow build-up thereon. Cutting slits (8) into the composite structure (2) is a technique which can be used to vary the heat distribution within the structure (2). The slits (8) are positioned according to the shape of the structure (2) and the location of the current injecting electrodes (11, 12).

Abstract: The electronic simplicity of a rotating-telescope target acquisition device and the noise immunity and wide field of view of a non-rotating array device are combined in an assembly (10) using a rotating refractory telescope (21) on a gimbaled platform (28), and a combination reticle (38) and detector (34) on the same platform (28). The detector (34) is segmented (50) to detect the direction in which a target is substantially off the telescope's optical axis (32), and the detector (34) is also shielded (35) against any radiation coming from outside the optical path of the telescope (21). The reticle (38) also serves as the electrical connection (42,62) between the detector segments (40,50) and the contact pads (44,64) on the detector plate (36).

Abstract: The manufacture of monolithic HgCdTe detectors and Si circuitry in an IR focal plane array is achieved by forming a protective layer of SiO.sub.2 or SiN.sub.x on a silicon wafer containing silicon circuits, etching steep-wall recesses into the wafer, selectively depositing epitaxial single-crystal layers of GaAs, CdTe, and HgCdTe in the recesses fabricating HgCdTe IR arrays, and depositing appropriate insulating and conductive interconnection patterns to interconnect the Si devices with one another and the HgCdTe devices with the Si devices. Little or no GaAs, CdTe, and HgCdTe grows on the SiO.sub.2 or SiN.sub.x outside the recesses. Since material grown outside the recess is polycrystalline, it is easily chemomechanically removed.

Abstract: The encapsulation of ceramic preforms (10) for HIP processing is considerably simplified, and the use of standard laboratory glassware as encapsulation material is made possible, by placing non-sealed glass capsule parts (12, 14) around the preform (10) in the HIP pressure vessel (18), evacuating the vessel (18), heating the vessel (18) to a temperature at which the glass parts (12, 14) fuse together but do not collapse, and then pressurizing the vessel (18) and increasing the temperature therein as required for conventional HIP processing.

Abstract: An antenna for transmitting and/or receiving circularly polarized (CP) electromagnetic radiation throughout a substantial portion of a sphere. A cylindrical waveguide (3,5) is associated with a transmit portion and a receive portion of the antenna, respectively. The outer surface of each waveguide (3,5) is covered with several conductive radiating patches (30,50) equidistant axially and circumferentially arranged. The patches (30,50) may be fed by elongated apertures (51,52) or by coaxial transmission line (41,42). In the former embodiment, CP is present within the waveguide (3,5), while in the latter embodiment, linear polarization is present within the coaxial transmission line (41,42). The individual patches (30,50) radiate CP in a direction normal to the patch (30,50) to produce CP in the broadside direction.

Abstract: A heater for a composite structure (2) is integrally formed as part of the structure (2) itself. The structure (2) comprises a layer of conductive fibers (30), such as a carbon felt mat, embedded in a nonconductive matrix (31). Electrodes (11, 12) inject an electrical current through multiple paths (15) through the conductive fibers (30), whereby the fibers (30) convert the electrical current to heat energy. Thus, the fibers (30) serve the dual roles of structural support to the composite structure (2) and heat converters. The composite structure (2) can be a portion of or an entire paraboloidal antenna reflector (6), in which case the heater of the present invention prevents and removes ice and snow build-up thereon. Cutting slits (8) into the composite structure (2) is a technique which can be used to vary the heat distribution within the structure (2). The slits (8) are positioned according to the shape of the structure (2) and the location of the current injecting electrodes (11, 12).

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 carriers 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: An efficient method for time-division multiplexing multiple digital signals into a single data stream for switching and/or transmission of information to a remote location. The apparatus according to the invention receives as input, to a multiplexer, a plurality of digital data streams of arbitrary word size and data rate, any one of the data rates being changeable with time such that the total data rate of all streams combined will, in general, greatly exceed the capacity of the multiplexer. Input digital signals are assumed to have an arbitrary word size and word rate subject to the constraint that the bit rate, that is, the word rate times the word size for each signal, is an integer multiple of a predetermined integer such that any time-varying mix of digital signals, regardless of word size, can be combined into a single time-division multiplexed bit stream in such a way that no individual signal, once placed in the format, will be moved to another place in the format.

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 carriers 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 method for controlling transition from thruster control to momentum wheel control to minimize nutation angle and transition time in a three-axis stabilized spacecraft employing an internal body fixed-momentum wheel as an attitude stabilizer. The method employs direct, substantially real-time measurement of momentum components and angular rates and generates paired roll thrust impluses and paired yaw thrust impulses in synchronization with the nutation period of the spacecraft to drive the spacecraft to a state of substantially zero nutation. The controller employs a deadbeat principle in a closed-loop real-time feedback system. In a preferred embodiment, the impulsive thruster firing commands in roll and yaw are simultaneous, spaced one-half nutation period apart in time with the effect that the target momentum is achieved in one to three pairs of impulse firings.

Abstract: A time delay shifter imparts a constant time delay to an electromagnetic signal, preferably a signal at a microwave frequency, over a band of frequencies. The phase shift imparted to the signal is a linear function of frequency. The shifter comprises a finite number of delay units (1) each having four single-pole single-throw switches (11-14). Closure of the first and third switches (11, 13) causes the signal to traverse a first path (2) containing a preselected length of transmission line that imparts a fixed time delay to the signal. Closure of the second and fourth switches (12,14) causes the signal to traverse a minimum-delay path (3) which is shorter than the delay path (2). The paths (2,3) are fabricated of coplanar waveguide. Each switch (11-14) is resonated by an inductor (21-24) for purposes of increasing isolation. An attenuator (70) is inserted in each minimum-delay path (3).

Abstract: A telescope body is disclosed. The telescope body generally includes a primary structure for holding a mirror, a secondary structure for holding a means for receiving a reflection from the mirror, and a mounting section connecting the primary and secondary structure. The primary and secondary structures include four-bar linkages which have linkage action planes intersecting at the focal point of the mirror. Apparatus for preventing the secondary structure from intruding in a raypath of light to the means for receiving a reflection is also disclosed.