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At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Improved charge injection device and a focal plane interface electronics board for stellar tracking

An improved Charge Injection Device (CID) stellar tracking sensor and an operating sensor in a control/readout electronics board were developed. The sensor consists of a shift register scanned, 256x256 CID array organized for readout of 4x4 subarrays. The 4x4 subarrays can be positioned anywhere within the 256x256 array with a 2 pixel resolution. This allows continuous tracking of a number of stars simultaneously since nine pixels (3x3) centered on any star can always be read out. Organization and operation of this sensor and the improvements in design and semiconductor processing are described. A hermetic package incorporating an internal thermoelectric cooler assembled using low temperature solders was developed. The electronics board, which contains the sensor drivers, amplifiers, sample hold circuits, multiplexer, analog to digital converter, and the sensor temperature control circuits, is also described. Packaged sensors were evaluated for readout efficiency, spectral quantum efficiency, temporal noise, fixed pattern noise, and dark current. Eight sensors along with two tracker electronics boards were completed, evaluated, and delivered.

Michon, G. J.↗
NASA NTRS1984

Definition, analysis and development of an optical data distribution network for integrated avionics and control systems. Part 2: Component development and system integration

Fiber optic transmission is emerging as an attractive concept in data distribution onboard civil aircraft. Development of an Optical Data Distribution Network for Integrated Avionics and Control Systems for commercial aircraft will provide a data distribution network that gives freedom from EMI-RFI and ground loop problems, eliminates crosstalk and short circuits, provides protection and immunity from lightning induced transients and give a large bandwidth data transmission capability. In addition there is a potential for significantly reducing the weight and increasing the reliability over conventional data distribution networks. Wavelength Division Multiplexing (WDM) is a candidate method for data communication between the various avionic subsystems. With WDM all systems could conceptually communicate with each other without time sharing and requiring complicated coding schemes for each computer and subsystem to recognize a message. However, the state of the art of optical technology limits the application of fiber optics in advanced integrated avionics and control systems. Therefore, it is necessary to address the architecture for a fiber optics data distribution system for integrated avionics and control systems as well as develop prototype components and systems.

Yen, H. W.↗
NASA NTRS1984

Conceptual design of a hybrid Ge:Ga detector array

For potential applications in space infrared astronomy missions such as the Space Infrared Telescope Facility and the Large Deployable Reflector, integrated arrays of long-wavelength detectors are desired. The results of a feasibility study which developed a design for applying integrated array techniques to a long-wavelength (gallium-doped germanium) material to achieve spectral coverage between 30 and 200 microns are presented. An approach which builds up a two-dimensional array by stacking linear detector modules is presented. The spectral response of the Ge:Ga detectors is extended to 200 microns by application of uniaxial stress to the stack of modules. The detectors are assembled with 1 mm spacing between the elements. Multiplexed readout of each module is accomplished with integration sampling of a metal-oxide-semiconductor (MOS) switch chip. Aspects of the overall design, including the anticipated level of particle effects on the array in the space environment, a transparent electrode design for 200 microns response, estimates of optical crosstalk, and mechanical stress design calculations are included.

Parry, C. M.↗
NASA NTRS1983

Image plane detector for the dynamics explorer Fabry-Perot interferometer

A compact twelve-channel photon-counting device based on existing Generation II imaging technology has been developed for use as the image-plane detector of the Dynamics Explorer Fabry-Perot interferometer. The device has an S-20 photocathode, three-microchannel plate electron multiplication stages, and an equal-area concentric-ring segmented anode whose geometry mimics that of the interference ring pattern produced by a plane etalon. The twelve channels sample equal and contiguous intervals in the spectrum. The purpose of the delopment has been to utilize the signal multiplex advantage of a multichannel detector in the measurement of Doppler shifts and line-broadening effects for naturally occurring atmospheric emission features of low intensity. The design, testing, calibration, and flight performance of the novel detector system are presented. In addition, measured emission line profiles at high resolution from the satellite instrument are presented to illustrate the operation of the device.

Killeen, T. L.↗
NASA NTRS1982

TDM/FM/FDMA - A modulation technique for multiple-beam satellites which precludes cochannel interference and allows non-uniform geographic distribution of user channels

The technique outlined in this paper is intended to eliminate the problems of cochannel interference and uniform geographic distribution of user channels which arise in conventional designs for a multiple spot beam communication satellite to serve mobile telephony users across the CONUS. By time multiplexing FM/FDMA signal ensembles so that only those beams operating on distinct frequency subbands are allowed to transmit concurrently, cochannel interference arising from simultaneous frequency subband reuse is precluded. Thus, time disjoint frequency reuse is accomplished over a repetitive sequence of fixed time slots. By assigning different size subbands to each time slot, a market of nonuniform users can be accommodated. The technique results in a greatly simplified antenna feed system design for the satellite, at a cost of imposing the need for time slot synchronization on the mobile FM receivers whose ability for rejecting adjacent channel interference is somewhat diminished.

Springett, J. C.↗
NASA NTRS1983

A four channel 10-nanometer spacing wavelength demultiplexer

Results on the development of an experimental four-channel fiber optics Wavelength Division Multiplexing (WDM) system with 10-nanometer channel spacing are presented. Data on WDM demultiplexers utilizing narrow band interference filters are reviewed. Results on studies of wavelength stability of semiconductor lasers for WDM are also presented.

Hendricks, H. D.↗
NASA NTRS1984

State estimation Kalman filter using optical processings Noise statistics known

Reference is made to a study by Casasent et al. (1983), which gave a description of a frequency-multiplexed acoustooptic processor and showed how it was capable of performing all the individual operations required in Kalman filtering. The data flow and organization of all required operations however, were not detailed in that study. Consideration is given here to a simpler Kalman filter state estimation problem. Equally spaced time-sampled intervals (k times T sub s, with k the iterative time index) are assumed. It is further assumed that the system noise vector w and the measurement noise vector v are uncorrelated and Gaussian distributed and that the noise statistics (Q and R) and the system model (Phi, Gamma, H) are known. The error covariance matrix P and the extrapolated error covariance matrix M can thus be precomputed and the Kalman gain matrix K sub k can be precomputed and stored for each input time sample.

Jackson, J.↗
NASA NTRS1982

Integrating 128 element InSb array - Recent results

There has been a continuing evolution toward larger arrays of infrared detectors, and the technology base derived from the Galileo Near Infrared Mapping Spectrometer (NIMS) has been expanded to linear arrays including from 128 to 512 elements. This advance is based on the commercial availability of high-quality InSb photodiodes and 128/256 element FET switch MUX's (multiplexing elements). The present investigation is concerned with an experimental 128-element linear imager using InSb detectors and silicon MUX for readout. Attention is given to detector array electrical characteristics, the detector readout architecture, noise, and special effects.

Bailey, G.↗
NASA NTRS1983

Lead sulfide - Silicon MOSFET infrared focal plane development

A process for directly integrating photoconductive lead sulfide (PbS) infrared detector material with silicon MOS integrated circuits has been developed primarily for application in long (greater than 10,000 detector elements) linear arrays for pushbroom scanning applications. The processing technology is based on the conventional PMOS and CMOS technologies with a variation in the metallization. Results and measurements on a fully integrated eight-element multiplexer are shown.

Barrett, J. R.↗
NASA NTRS1985

Infrared Linear Imaging Array

Photodiodes, multiplexer, and preamp reside in hybrid ceramic package. Hybrid microcircuit produces 128-element line images of infrared scenes. Each picture element is 0.008-in. (0.2-mm) square. Even without image data processing, microcircuit resolves temperature differences as small as 0.05 degrees C in infrared images.

Bailey, G. C.↗
NASA NTRS1985

Fast Control Sequencer

Unit faster than conventional circuits and contains fewer integrated circuits. Fast logic controller accommodates three delays before second half cycle of clock signal strobes status latch: Outputs of pipeline register must settle; selected input status line signal must propagate through status multiplexer and arrive at status latch; and it takes 3 nanoseconds for status latch set up before strobed. During second half cycle, output-enable line produces next instruction and applies it to pipeline register.

Lahmeyer, C. R.↗
NASA NTRS1986

Molecular-Beam Chopper and Four-Channel Amplifier

Molecular-beam chopper phase controller and timing interface is subsystem of four-stage, differentially pumped, modulated molecular-beam/mass spectrometer. Subsystem maintains accurate phase control and timing for repetitive signal averaging over several hours of operation. Chopper phase controller/ timing interface and four-channel programable time-multiplexed amplifier provide substantial improvements in attainable signal-to-noise ratio, detection limit, and accuracy of molecular-beam/mass-spectrometer system.

Adams, B. R.↗
NASA NTRS1984

Avionics/crew station integration

The U.S. Navy has been encouraging advanced development concepts aimed at increasing the aircraft instrumentation performance for multi-platform applications of 1990's weapons systems. The three areas covered by the Navy's research and development effort are: System Integration, Technology, and Human Factors. The System Integration objectives are to produce a system architecture easily adaptable to many platforms. Technology objectives are to determine the state of the art for displays, electronics, and controls. The Human Factors objectives are to determine the proper human-machine interfaces so that the ultimate crew station will be capable of providing the pilot with the proper display and controls performance to satisfy the diverse requirements of a fighter, attack, ASW, fixed-wing, rotary-wing, and V/STOL platforms in both a one-man crew or two-man crew matrix. All data/control interface among units of this crew station and other platform subsystems will be via digital data buses and video multiplex buses. No individual discrete signal, data, or control lines will be needed. This paper discusses the six interfaces necessary to ensure the optimum development of this crew station, the predicted platform mission improvements, and the requisite life-cycle cost considerations. This concept will serve as a basis for planning the integration of the necessary hardware and software features in current and future weapons systems.

Mulley, W. G.↗
NASA NTRS1984

Attack helicopter (AH-1T) cockpit systems integration

This discussion summarizes the effort conducted by the BHTI Human Factors and Cockpit Arrangement group for a study and design of the integration of a cockpit control system for the AH 1T (TOW). The resulting design is a culmination of studies that were conducted using the existing configuration as a baseline and complementing it with new equipment and subsystems that fulfill the attack helicopter requirements for the foreseeable future. Of primary concern was the requirement to add a missile control system, with secondary considerations for improved NOE and night operations. In addition, growth capabilities for improved target acquisition, weapons delivery, and precise navigation was considered. Along with the addition of new equipment, the aircraft was assumed to have a central multiplex data bus system for information transfer throughout the aircraft and its subsystems.

Graf, V. A.↗
NASA NTRS1985

Development and implementation of the verification process for the shuttle avionics system

The background of the shuttle avionics system design and the unique drivers associated with the redundant digital multiplexed data processing system are examined. With flight software pervading to the lowest elements of the flight critical subsystems, it was necessary to identify a unique and orderly approach of verifying the system as flight ready for STS-1. The approach and implementation plan is discussed, and both technical problems and management issues are dealt with.

Smith, H. E.↗
NASA NTRS1985

Shuttle S-band communications technical concepts

Using the S-band communications system, shuttle orbiter can communicate directly with the Earth via the Ground Spaceflight Tracking and Data Network (GSTDN) or via the Tracking and Data Relay Satellite System (TDRSS). The S-band frequencies provide the primary links for direct Earth and TDRSS communications during all launch and entry/landing phases of shuttle missions. On orbit, S-band links are used when TDRSS Ku-band is not available, when conditions require orbiter attitudes unfavorable to Ku-band communications, or when the payload bay doors are closed. the S-band communications functional requirements, the orbiter hardware configuration, and the NASA S-band communications network are described. The requirements and implementation concepts which resulted in techniques for shuttle S-band hardware development discussed include: (1) digital voice delta modulation; (2) convolutional coding/Viterbi decoding; (3) critical modulation index for phase modulation using a Costas loop (phase-shift keying) receiver; (4) optimum digital data modulation parameters for continuous-wave frequency modulation; (5) intermodulation effects of subcarrier ranging and time-division multiplexing data channels; (6) radiofrequency coverage; and (7) despreading techniques under poor signal-to-noise conditions. Channel performance is reviewed.

Seyl, J. W.↗
NASA NTRS1985

Gas chromatography: Possible application of advanced instrumentation developed for solar system exploration to space station cabin atmospheres

Gas chromatography (GC) technology was developed for flight experiments in solar system exploration. The GC is a powerful analytical technique with simple devices separating individual components from complex mixtures to make very sensitive quantitative and qualitative measurements. It monitors samples containing mixtures of fixed gases and volatile organic molecules. The GC was used on the Viking mission in support of life detection experiments and on the Pioneer Venus Large Probe to determine the composition of the venusian atmosphere. A flight GC is under development to study the progress and extent of STS astronaut denitrogenation prior to extravehicular activity. Advanced flight GC concepts and systems for future solar system exploration are also studied. Studies include miniature ionization detectors and associated control systems capable of detecting from ppb up to 100% concentration levels. Further miniaturization is investigated using photolithography and controlled chemical etching in silicon wafers. Novel concepts such as ion mobility drift spectroscopy and multiplex gas chromatography are also developed for future flight experiments. These powerful analytical concepts and associated hardware are ideal for the monitoring of cabin atmospheres containing potentially dangerous volatile compounds.

Carle, G. C.↗
NASA NTRS1984

Recent advances in electroluminescent displays applicable to future crew-station interfaces

The operative principles and progress to date on producing thin-film electroluminescent displays (TFEL) are discussed. TFEL displays consist of conductive, insulating and phosphor film layers deposited on a glass substrate. Applying a 200 V potential between the rows and columns in a multiplexed mode causes light to be emitted. Varying the voltage varies the grey level. The panels provide adequate contrast in full sunlight, and have demanded only 4-6 W for 15 sq in. displays. Alphanumeric, graphics, and video images have been generated with a 51 line by 80 character display. The upper limit on the panel size has not yet been defined. Efforts are under way to produce multicolor displays using red and blue phosphors. Trial units are being studied for avionics displays for, e.g., navigation, multipurpose displays, and attitude/direction indicators.

Miller, M. R.↗