Tech Briefs

Optical Characterization of Molecular Contaminant Films

A theoretical model is correlated with measured spectral transmittances and VUV exposures of spacecraft optics. Lyndon B. Johnson Space Center, Houston, Texas A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thin-film radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Optics, Coatings, colorants, and finishes, Glass, Satellites, Spacecraft

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Coating MCPs With AlN and GaN

Emission of electrons is increased.A development effort underway at the time of reporting the information for this article is devoted to increasing the sensitivity of microchannel plates (MCPs) as detectors of photons and ions by coating the MCPs with nitrides of elements in period III of the periodic table. Conventional MCPs are relatively insensitive to slowly moving, large-mass ions — for example, ions of biomolecules under analysis in mass spectrometers. The idea underlying this development is to coat an MCP to reduce its work function (decrease its electron affinity) in order to increase both (1) the emission of electrons in response to impingement of low-energy, large-mass ions and (2) the multiplying effect of secondary electron emission.

Posted in: Briefs, Electronics & Computers

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Automatic Locking of Laser Frequency to an Absorption Peak

Initial manual tuning is ordinarily not necessary. An electronic system adjusts the frequency of a tunable laser, eventually locking the frequency to a peak in the optical absorption spectrum of a gas (or of a Fabry-Perot cavity that has an absorption peak like that of a gas). This system was developed to enable precise locking of the frequency of a laser used in differential absorption LIDAR measurements of trace atmospheric gases. This system also has great commercial potential as a prototype of means for precise control of frequencies of lasers in future dense wavelength-division-multiplexing optical communications systems.

Posted in: Briefs, Electronics & Computers

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Noise Source for Calibrating a Microwave

This compact unit can readily be integrated into an airborne microwave instrumentation. A correlated-noise source has been developed for use in calibrating an airborne or spaceborne Earth-observing correlation microwave polarimeter that operates in a pass band that includes a nominal frequency of 10.7 GHz. Deviations from ideal behavior of the hardware of correlation polarimeters are such as to decorrelate the signals measured by such an instrument. A correlated- noise source provides known input signals, measurements of which can be processed to estimate and correct for the decorrelation effect.

Posted in: Briefs, Electronics & Computers

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Self-Passivating Lithium/Solid Electrolyte/Iodine Cells

Passivating lithium iodide films of optimum or nearly optimum thickness form spontaneously. Robust lithium/solid electrolyte/iodine electrochemical cells that offer significant advantages over commercial lithium/ iodine cells have been developed. At room temperature, these cells can be discharged at current densities 10 to 30 times those of commercial lithium/iodine cells. Moreover, from room temperature up to 80 °C, the maximum discharge-current densities of these cells exceed those of all other solid-electrolyte-based cells.

Posted in: Briefs, TSP, Electronics & Computers

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Hybrid Deployable Foam Antennas and Reflectors

Compressed foam structures would be expanded to full size and shape.Hybrid deployable radio antennas and reflectors of a proposed type would feature rigid narrower apertures plus wider adjoining apertures comprising reflective surfaces supported by open-cell polymeric foam structures (see figure). The open-cell foam structure of such an antenna would be compressed for compact stowage during transport. To initiate deployment of the antenna, the foam structure would simply be released from its stowage mechanical restraint. The elasticity of the foam would drive the expansion of the foam structure to its full size and shape.

Posted in: Briefs, TSP, Electronics & Computers, Antennas, Storage, Foams

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Gesture-Controlled Interfaces for Self-Service Machines

Potential advantages include immunity to wear and increased safetyGesture-controlled interfaces are software-driven systems that facilitate device control by translating visual hand and body signals into commands. Such interfaces could be especially attractive for controlling self-service machines (SSMs) — for example, public information kiosks, ticket dispensers, gasoline pumps, and automated teller machines (see figure).

Posted in: Briefs, Electronics & Computers

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