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Results for “DIGITAL TECHNIQUE”

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 469 records · Page 26
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NASA NTRS1975

Twenty and thirty GHz millimeter wave experiments with the ATS-6 satellite

The ATS-6 millimeter wave experiment, provided the first direct measurements of 20 and 30 GHz earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques. In addition to direct measurements on the 20 and 30 GHz links, methods of attenuation prediction with radars, rain gages, and radiometers were developed and compared with the directly measured attenuation. Initial data results of the ATS-6 millimeter wave experiment from the major participating organizations are presented.

Ippolito, L. J.↗
NASA NTRS1975

Remote sensing impact on corridor selection and placement

Computer-aided corridor selection techniques, utilizing digitized data bases of socio-economic, census, and cadastral data, and developed for highway corridor routing are considered. Land resource data generated from various remote sensing data sources were successfully merged with the ancillary data files of a corridor selection model and prototype highway corridors were designed using the combined data set. Remote sensing derived information considered useful for highway corridor location, special considerations in geometric correction of remote sensing data to facilitate merging it with ancillary data files, and special interface requirements are briefly discussed.

Thomson, F. J.↗
NASA NTRS1976

Twenty and thirty GHz millimeter wave experiments with the ATS-6 satellite

Studies at 11 locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques using the Applications Technology Satellite-6(ATS-6). In addition to direct measurements on the 20- and 30-GHz links, methods of attenuation prediction with radars, rain gages, and radiometers were developed and compared with the directly measured attenuation. Initial data results of the ATS-6 millimeter wave experiment were presented. The first section describes the experiment objectives, flight hardware, and modes of operation. The remaining six sections present papers prepared by the major participating organizations in the experiment. The papers present a comprehensive summary of the significant results of the initial 11 months of ATS-6 experiment measurements and related radiometric, radar, and radio-meteorology studies.

Ippolito, L. J.↗
NASA NTRS1975

Remote sensing and applications

A brief review of application of remote sensing technology is given. The effectiveness of the multispectral band scanner, color analysis of imagery, and resolution are among the factor's discussed. The users' need for repetitive data, rapid data delivery, and developing digital data techniques are also considered.

Stoney, W.↗
NASA NTRS1975

ATS-6 - Millimeter Wave Propagation and Communications Experiments at 20 and 30 GHz

The Applications Technology Satellite (ATS-6) Millimeter Wave Experiment, developed and implemented by the NASA Goddard Space Flight Center, has provided the first direct measurements of 20- and 30-GHz earth-space links from an orbiting satellite. Studies at eleven locations in the continental United States were directed at an evaluation of rain attenuation effects, scintillations, depolarization, site diversity, coherence bandwidth, and analog and digital communications techniques. In addition to direct measurements on the 20- and 30-GHz links, methods of attenuation prediction with radars, rain gauges, and radiometers were developed and compared with the directly measured attenuation. This paper presents a review of the major results of the first year of measurements with ATS-6, with emphasis on the impact of the measurements on millimeter wave space systems design.

Ippolito, L. J.↗
NASA NTRS1976

Digital image processing of earth observation sensor data

This paper describes digital image processing techniques that were developed to precisely correct Landsat multispectral earth observation data and gives illustrations of the results achieved, e.g., geometric corrections with an error of less than one picture element, a relative error of one-fourth picture element, and no radiometric error effect. Techniques for enhancing the sensor data, digitally mosaicking multiple scenes, and extracting information are also illustrated.

Bernstein, R.↗
NASA NTRS1976

A vortex model of cavity flow

The paper presents a model of two-dimensional cavity flow in which the shear layer over the cavity is represented by discrete rectilinear vortices which are free to move as the flow progresses. Although the model is initially started impulsively, the computation is continued until a statistically steady flow is attained. The broadband noise generation of the cavity is calculated by first running the model until the steady state is reached and then computing a stationary record of far-field density fluctuation through an equation that is suitable for calculating the quadrupole noise generation by the model. The discrete time series obtained can be analyzed by ordinary digital spectral techniques to determine the spectra and overall levels of the noise in airframe noise testing of real aircraft.

Hardin, J. C.↗
NASA NTRS1977

Mu-2 ranging

The Mu-II Dual-Channel Sequential Ranging System designed as a model for future Deep Space Network ranging equipment is described. A list of design objectives is followed by a theoretical explanation of the digital demodulation techniques first employed in this machine. Hardware and software implementation are discussed, together with the details relating to the construction of the device. Two appendixes are included relating to the programming and operation of this equipment to yield the maximum scientific data.

Martin, W. L.↗
NASA NTRS1977

Aircraft cybernetics

The use of computers for aircraft control, flight simulation, and inertial navigation is explored. The man-machine relation problem in aviation is addressed. Simple and self-adapting autopilots are described and the assets and liabilities of digital navigation techniques are assessed.

Source record↗
NASA NTRS1979

Eliminating ambiguity in digital signals

Multiamplitude minimum shift keying (mamsk) transmission system, method of differential encoding overcomes problem of ambiguity associated with advanced digital-transmission techniques with little or no penalty in transmission rate, error rate, or system complexity. Principle of method states, if signal points are properly encoded and decoded, bits are detected correctly, regardless of phase ambiguities.

Weber, W. J., III↗
NASA NTRS1977

A survey of users of earth resources remote sensing data

The use of Landsat imagery and digital data, Skylab data and high-altitude aerial imagery by industry, government, academic and foreign analysts was surveyed. The study indicated that while most users are satisfied with current Landsat product quality and spectral coverage, there does exist a significant demand for extension of the spectral coverage to thermal and microwave regions, for resolutions in the 20 to 40 and 10 to 20 meter range, and for more rapid data delivery. Problems involving the acceptance of digital processing techniques by some users are also mentioned.

Wukelic, G. E.↗
NASA NTRS1977

A digitally implemented communications experiment utilizing the Hermes /CTS/ satellite

Attention is given to an investigation being conducted by NASA-Lewis and Comsat Laboratories which uses the Hermes (CTS) satellite to explain digital link implementation and the advantages it provides over conventional analog systems. The experiment concentrates on developing several video, audio, and data digital communications techniques.

Jackson, H. D.↗
NASA NTRS1977

Integration of socioeconomic data and remotely sensed imagery for land use applications

The Image Based Information System (IBIS) uses techniques of digital image processing to interface geocoded data sets, information management systems, thematic maps, and remotely sensed imagery. For two cases IBIS has been used to integrate remotely sensed imagery and socioeconomic data. In the first case thematically classified Landsat imagery covering Orange County, California is combined with census tracts and municipalities. In the second case, thematically classified Landsat imagery over Los Angeles, California is combined with census tracts.

Bryant, N. A.↗
NASA NTRS1979

A Study of Linear Approximation Techniques for SAR Azimuth Processing

The application of the step transform subarray processing techniques to synthetic aperture radar (SAR) was studied. The subarray technique permits the application of efficient digital transform computational techniques such as the fast Fourier transform to be applied while offering an effective tool for range migration compensation. Range migration compensation is applied at the subarray level, and with the subarray size based on worst case range migration conditions, a minimum control system is achieved. A baseline processor was designed for a four-look SAR system covering approximately 4096 by 4096 SAR sample field every 2.5 seconds. Implementation of the baseline system was projected using advanced low power technologies. A 20 swath is implemented with approximately 1000 circuits having a power dissipation of from 70 to 195 watts. The baseline batch step transform processor is compared to a continuous strip processor, and variations of the baseline are developed for a wide range of SAR parameters.

Martinson, L. W.↗
NASA NTRS1978

Performance of preproduction model cesium beam frequency standards for spacecraft applications

A cesium beam frequency standards for spaceflight application on Navigation Development Satellites was designed and fabricated and preliminary testing was completed. The cesium standard evolved from an earlier prototype model launched aboard NTS-2 and the engineering development model to be launched aboard NTS satellites during 1979. A number of design innovations, including a hybrid analog/digital integrator and the replacement of analog filters and phase detectors by clocked digital sampling techniques are discussed. Thermal and thermal-vacuum testing was concluded and test data are presented. Stability data for 10 to 10,000 seconds averaging interval, measured under laboratory conditions, are shown.

Levine, M. W.↗
NASA NTRS1978

Information extraction from digital images of the earth and the planets

An overview is presented of recent developments at the JPL Image Processing Laboratory which emphasize the utilization of a digital computer to automate the process of information extraction from digital imagery. Consideration is given to: (1) the analysis of Viking Orbiter stereo imagery to determine elevation profiles of the Mars surface, (2) the use of Viking Lander stereo imagery to determine nonhazardous surface sample acquisition strategies, (3) the correlation of Landsat imagery with geographically referenced cultural data to determine land use trends, and (4) the generation of mosaics using digital computer techniques.

Green, W. B.↗
NASA NTRS1980

Voyager image processing at the Image Processing Laboratory

This paper discusses new digital processing techniques as applied to the Voyager Imaging Subsystem and devised to explore atmospheric dynamics, spectral variations, and the morphology of Jupiter, Saturn and their satellites. Radiometric and geometric decalibration processes, the modulation transfer function, and processes to determine and remove photometric properties of the atmosphere and surface of Jupiter and its satellites are examined. It is exhibited that selected images can be processed into 'approach at constant longitude' time lapse movies which are useful in observing atmospheric changes of Jupiter. Photographs are included to illustrate various image processing techniques.

Jepsen, P. L.↗