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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Signal chain for the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

The AVIRIS instrument has a separate dedicated analog signal processing chain for each of its four spectrometers. The signal chains amplify low-level focal-plane line array signals (5 to 10 mV full-scale span) in the presence of larger multiplexing signals (approx 150 mV) providing the data handling system a ten-bit digital word (for each spectrometer) each 1.3 microns. This signal chain provides automatic correction for the line array dark signal nonuniformity (which can approach the full-scale signal span).

Bunn, James S., Jr.↗
NASA NTRS1997

Visual signal detection in structured backgrounds. II. Effects of contrast gain control, background variations, and white noise

Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal. To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to inhibit (divisively) the response of the receptor sensitive to the signal. In tasks in which the observer has to detect a known signal added to one of M different backgrounds grounds due to added visual noise, the main sources of degradation are the stochastic noise in the image and the suboptimal visual processing. We investigate how these two sources of degradation (contrast gain control and variations in the background) interact in a task in which the signal is embedded in one of M locations in a complex spatially varying background (structured background). We use backgrounds extracted from patient digital medical images. To isolate effects of the fixed deterministic background (the contrast gain control) from the effects of the background variations, we conduct detection experiments with three different background conditions: (1) uniform background, (2) a repeated sample of structured background, and (3) different samples of structured background. Results show that human visual detection degrades from the uniform background condition to the repeated background condition and degrades even further in the different backgrounds condition. These results suggest that both the contrast gain control mechanism and the background random variations degrade human performance in detection of a signal in a complex, spatially varying background. A filter model and added white noise are used to generate estimates of sampling efficiencies, an equivalent internal noise, an equivalent contrast-gain-control-induced noise, and an equivalent noise due to the variations in the structured background.

NASA Discipline Space Human Factors↗
NASA NTRS2015

Processing and Prolonged 500 C Testing of 4H-SiC JFET Integrated Circuits with Two Levels of Metal Interconnect

Complex integrated circuit (IC) chips rely on more than one level of interconnect metallization for routing of electrical power and signals. This work reports the processing and testing of 4H-SiC junction field effect transistor (JFET) prototype IC's with two levels of metal interconnect capable of prolonged operation at 500 C. Packaged functional circuits including 3- and 11-stage ring oscillators, a 4-bit digital to analog converter, and a 4-bit address decoder and random access memory cell have been demonstrated at 500 C. A 3-stage oscillator functioned for over 3000 hours at 500 C in air ambient. Improved reproducibility remains to be accomplished.

JFET↗
NASA NTRS1982

Modeling and a correlation algorithm for spaceborne SAR signals

A mathematical model of a spaceborne synthetic aperture radar (SAR) response is presented. Thhe associated SAR system performance, in terms of the resolution capability, is also discussed. The analysis of spaceborne SAR target response indicates that the SAR correlation problem is a two-dimensional one with a linear shift-variant response function. A new digital processing algorithm is proposed here in order to realize an economical digital SAR correlation system. The proposed algorithm treats the two-dimensional correlation by a combination of frequency domain fast correlation in the azimuth dimension and a time-domain convolver type of operation in the range dimension. Finally, digitally correlated SEASAT satellite SAR imagery is used in an exemplary sense to validate the SAR response model and the new digital processing technique developed.

Wu, C.↗
NASA NTRS1983

Diagnostic analysis of vibration signals using adaptive digital filtering techniques

Signal enhancement techniques are described using recently developed digital adaptive filtering equipment. Adaptive filtering concepts are not new; however, as a result of recent advances in microprocessor-based electronics, hardware has been developed that has stable characteristics and of a size exceeding 1000th order. Selected data processing examples are presented illustrating spectral line enhancement, adaptive noise cancellation, and transfer function estimation in the presence of corrupting noise.

Jewell, R. E.↗
NASA NTRS1985

Development and flight test of a helicopter, X-band, portable precision landing system concept

A beacon landing system (BLS) is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. The system is based on state-of-of-the-art X-band radar technology and digital processing techniques. The bLS airborne hardware consists of an X-band receiver and a small micropreocessor, installed in conjunction wht the aircraft instrument landing system (ILS) receiver. The microprocessor analyzes the X-band, BLS pulses and outputs ILS-compatible localizer and glide slope signals. Range information is obtained using an on-board weather/mapping radar in conjunction with the BLS. The ground station is an inexpensive, portable unit; it weighs less than 70 lb and can be quickly deployed at a landing site. Results from the flight-test program show that the BLS has a significant potential for providing rotorcaraft with low-cost, precision instrument approach capability in remote areas.

Davis, T. J.↗
NASA NTRS1985

Development and flight test of a helicopter, X-band, portable precision landing system concept

A beacon landing system (BLS) is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. The system is based on state-of-the-art X-band radar technology and digital processing techniques. The BLS airborne hardware consists of an X-band receiver and a small microprocessor, installed in conjunction with the aircraft instrument landing system (ILS) receiver. The microprocessor analyzes the X-band, BLS pulses and outputs ILS-compatible localizer and glide slope signals. Range information is obtained using an on-board weather/mapping radar in conjunction with the BLS. The ground station is an inexpensive, portable unit; it weighs less than 70 lb and can be quickly deployed at a landing site. Results from the flight-test program show that the BLS has a significant potential for providing rotorcraft with low-cost, precision instrument approach capability in remote areas.

Davis, T. J.↗
NASA NTRS1998

LITE data processing

The Lidar In-space Technology Experiment (LITE) was a payload onboard the Space Shuttle Discovery as part of the September 1994 STS-64 mission. LITE successfully made both atmospheric and surface measurements at the 355 nm, 532 nm, and 1064 nm wavelengths [Winker et al., 1996]. At mission completion, nearly 45 Gbytes of data had been obtained. As the data were collected they were organized into three data sets. The largest of these data sets contained the single-shot full resolution digitized lidar signals for all three wavelengths. The other two data sets contained the instrument status data block (ISDB) and the quick look science data (QLSD). ISDB information was generated once per second and contained timing parameters and engineering data related to the health, status, and configuration of the instrument. The QLSD are 100shot averages of the 355 nm and 532 nm lidar signals and were generated at ten second intervals. As the LITE data were generated, they were output to low-rate and high-rate telemetry streams. The low-rate data contained the ISDB and QLSD. The lowrate data were transmitted to the ground by the Shuttle S-band system through the Tracking and Data Relay Satellite System (TDRSS). The high-rate data contained the full resolution digitized lidar signals for all three wavelengths, the ISDB, and QLSD. The high-rate data were transmitted in real time by the Ku-band system through TDRSS downlink to the LITE operations center at the Johnson Space Center (JSC). High-rate data were only obtained when the orbiter and TDRSS telemetry link coincided with the real-time operations of LITE. The low-rate data were backed up by a Shuttle recorder during periods when the telemetry link was unavailable, and the entire lowrate data stream was transferred to the ground over the course of the mission. A total of 53 hours of lowrate data and 45.5 hours of high-rate data were acquired. All of the LITE raw telemetry data have been archived at the NASA Langley Research Center (LaRC), and the LITE high-rate data have been processed to the level 1 data product. This paper describes the data processing steps required to convert the LITE raw, high-rate telemetry data to the LITE level 1 data product.

Powell, Kathleen A.↗
NASA NTRS1976

Digital image correlation techniques applied to LANDSAT multispectral imagery

The author has identified the following significant results. Automatic image registration and resampling techniques applied to LANDSAT data achieved accuracies, resulting in mean radial displacement errors of less than 0.2 pixel. The process method utilized recursive computational techniques and line-by-line updating on the basis of feedback error signals. Goodness of local feature matching was evaluated through the implementation of a correlation algorithm. An automatic restart allowed the system to derive control point coordinates over a portion of the image and to restart the process, utilizing this new control point information as initial estimates.

Bonrud, L. O.↗
NASA NTRS1991

HYMOSS signal processing for pushbroom spectral imaging

The objective of the Pushbroom Spectral Imaging Program was to develop on-focal plane electronics which compensate for detector array non-uniformities. The approach taken was to implement a simple two point calibration algorithm on focal plane which allows for offset and linear gain correction. The key on focal plane features which made this technique feasible was the use of a high quality transimpedance amplifier (TIA) and an analog-to-digital converter for each detector channel. Gain compensation is accomplished by varying the feedback capacitance of the integrate and dump TIA. Offset correction is performed by storing offsets in a special on focal plane offset register and digitally subtracting the offsets from the readout data during the multiplexing operation. A custom integrated circuit was designed, fabricated, and tested on this program which proved that nonuniformity compensated, analog-to-digital converting circuits may be used to read out infrared detectors. Irvine Sensors Corporation (ISC) successfully demonstrated the following innovative on-focal-plane functions that allow for correction of detector non-uniformities. Most of the circuit functions demonstrated on this program are finding their way onto future IC's because of their impact on reduced downstream processing, increased focal plane performance, simplified focal plane control, reduced number of dewar connections, as well as the noise immunity of a digital interface dewar. The potential commercial applications for this integrated circuit are primarily in imaging systems. These imaging systems may be used for: security monitoring systems, manufacturing process monitoring, robotics, and for spectral imaging when used in analytical instrumentation.

Ludwig, David E.↗
NASA NTRS1977

Hybrid receiver study

The results are presented of a 4 month study to design a hybrid analog/digital receiver for outer planet mission probe communication links. The scope of this study includes functional design of the receiver; comparisons between analog and digital processing; hardware tradeoffs for key components including frequency generators, A/D converters, and digital processors; development and simulation of the processing algorithms for acquisition, tracking, and demodulation; and detailed design of the receiver in order to determine its size, weight, power, reliability, and radiation hardness. In addition, an evaluation was made of the receiver's capabilities to perform accurate measurement of signal strength and frequency for radio science missions.

Stone, M. S.↗
NASA NTRS1989

Digital 8-DPSK Modem For Trellis-Coded Communication

Digital real-time modem processes octuple differential-phase-shift-keyed trellis-coded modulation. Intended for use in communicating data at rate up to 4.8 kb/s in land-mobile satellite channel (Rician fading) of 5-kHz bandwidth at carrier frequency of 1 to 2 GHz. Modulator and demodulator contain digital signal processors performing modem functions. Design flexible in that functions altered via software. Modem successfully tested and evaluated in both laboratory and field experiments, including recent full-scale satellite experiment. In all cases, modem performed within 1 dB of theory. Other communication systems benefitting from this type of modem include land mobile (without satellites), paging, digitized voice, and frequency-modulation subcarrier data broadcasting.

Jedrey, T. C.↗
NASA NTRS1989

Improved defect analysis of Gallium Arsenide solar cells using image enhancement

A new technique has been developed to capture, digitize, and enhance the image of light emission from a forward biased direct bandgap solar cell. Since the forward biased light emission from a direct bandgap solar cell has been shown to display both qualitative and quantitative information about the solar cell's performance and its defects, signal processing techniques can be applied to the light emission images to identify and analyze shunt diodes. Shunt diodes are of particular importance because they have been found to be the type of defect which is likely to cause failure in a GaAs solar cell. The presence of a shunt diode can be detected from the light emission by using a photodetector to measure the quantity of light emitted at various current densities. However, to analyze how the shunt diodes affect the quality of the solar cell the pattern of the light emission must be studied. With the use of image enhancement routines, the light emission can be studied at low light emission levels where shunt diode effects are dominant.

Kilmer, Louis C.↗
NASA NTRS1990

Annual Health Monitoring Conference for Space Propulsion Systems, 2nd, Cincinnati, OH, Nov. 14, 15, 1990, Proceedings

This conference discusses health management systems for liquid rocket engines, signal processing of spectroscopic data for engine diagnostic applications, real-time diagnostics of the reusable rocket engine using on-line system identification, and nonlinear parameter estimation for rocket engine health monitoring. Plume diagnostics are considered including discussion on preliminary plume diagnostics on the SSME using video digitization techniques and baseline plume emmissions. The development of a Fabry-Perot Interferometer for rocket engine plumes is also considered. The topic of computational modeling is also discussed, addressing such topics as probabalistic dynamics of material loss in the SSME turbomachinery, state-variable modelling of fluid-dynamics processes, and a model for the SSME high pressure oxidizer turbopump shaft seal system. A discussion of sensor development includes the topics of sensor development for the rocket engine condition monitoring system and the heat flux measurements in SSME turbine blade tester.

Source record↗
NASA NTRS1992

The design, fabrication, and test of a new VLSI hybrid analog-digital neural processing element

A hybrid analog-digital neural processing element with the time-dependent behavior of biological neurons has been developed. The hybrid processing element is designed for VLSI implementation and offers the best attributes of both analog and digital computation. Custom VLSI layout reduces the layout area of the processing element, which in turn increases the expected network density. The hybrid processing element operates at the nanosecond time scale, which enables it to produce real-time solutions to complex spatiotemporal problems found in high-speed signal processing applications. VLSI prototype chips have been designed, fabricated, and tested with encouraging results. Systems utilizing the time-dependent behavior of the hybrid processing element have been simulated and are currently in the fabrication process. Future applications are also discussed.

Deyong, Mark R.↗
DOE OSTI2025

2025 Intern Poster

The Hot Fuel Examination Facility (HFEF) at the Materials and Fuels Complex (MFC) houses the largest U.S. inert atmosphere hot cell for nuclear material research. Key features include the precision gamma scanning (PGS), Fuel Accident Condition Simulator (FACS), Neutron Radiography Reactor (NRAD), and the focus of this project, the Metallograph Loading Cell (MET Cell). The MET Cell performs tests on spent nuclear fuel, such as microhardness testing, microscopy, and neutron radiography. However, the MET Cell’s existing pressure and lighting control systems are outdated and inefficient, with inadequate documentation for system changes over time. This project aims to design a new automated control system for the MET Cell, ensuring longevity (minimum ten years), ease of troubleshooting/repair, and integration into the building monitoring system. The design process addressed challenges such as space restrictions, varied voltages within enclosures, sourcing new components, and security limitations. Compliance with NFPA 70, UL508A, MFC Physical Security, and INL Engineering standards was essential. The project involves repurposing an existing PLC to manage lighting and pressure control using digital and analog signals, simplifying wiring, and ensuring thorough documentation for future reference.

42 - ENGINEERING↗
NASA NTRS1981

Method and apparatus for holographic processing

A method and apparatus for holographically processing optical signals in a fiber-optic sensor system. In the present invention, holographic processors are utilized in various combinations with light sources, fiber-optic transmission means, sensors and detectors to provide low cost, compact, sensitive and accurate sensor systems. By means of the holographic processors of the present invention, the aforementioned sensor systems are used to monitor such physical parameters as temperature, pressure, flow-rate, and the like, and to provide output signal indications thereof that are compatible with digital receiving stations and immune to electro-magnetic interference, hazardous atmosphere, and the inimical effects of inadvertent intensity variation due to equipment vibration and the like. In one typical embodiment, a pair of holographic processors are employed in a color multiplex-demultiplex sensor system in which a first holographic processor is employed to color multiplex a sensor signal and a second holographic processor is employed to decode the color-multiplexed signal into a binary pattern that is then transmitted onto a set of photodetectors. In each of the embodiments of the invention disclosed, a unique geometrical orientation of a hologram is utilized to minimize spurious signal interference that would otherwise hamper or totally preclude the holographic processing.

Quick, William H.↗
NASA NTRS1985

ICIASF '85 - International Congress on Instrumentation in Aerospace Simulation Facilities, 11th, Stanford University, CA, August 26-28, 1985, Record

Developments related to laser Doppler velocimetry are discussed, taking into account a three-component dual beam laser-Doppler-anemometer to be operated in large wind tunnels, a new optical system for three-dimensional laser-Doppler-anemometry using an argon-ion and a dye laser, and a two-component laser Doppler velocimeter by switching fringe orientation. Other topics studied are concerned with facilities, instrumentation, control, hot wire/thin film measurements, optical diagnostic techniques, signal and data processing, facilities and adaptive wall test sections, data acquisition and processing, ballistic instrument systems, dynamic testing and material deformation measurements, optical flow measurements, test techniques, force measurement systems, and holography. Attention is given to nonlinear calibration of integral wind tunnel balances, a microcomputer system for real time digitized image compression, and two phase flow diagnostics in propulsion systems.

Source record↗