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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Computer Mapping of Water Quality in Saginaw Bay with LANDSAT Digital Data

The author has identified the following significant results. LANDSAT digital data and ground truth measurements for Saginaw Bay (Lake Huron), Michigan, for 31 July 1975 were correlated by stepwise linear regression and the resulting equations used to estimate invisible water quality parameters in nonsampled areas. Chloride, conductivity, total Kjeldahl nitrogen, total phosphorus, and chlorophyll a were best correlated with the ratio of LANDSAT Band 4 to Band 5. Temperature and Secchi depth correlate best with Band 5.

Rogers, R. H.↗
NASA NTRS1976

The neutral coma of comets: A review

The hypothesis that water snow controls the vaporization of the nucleus of some comets seems verified from the general order of magnitude of the size of their nucleus and of their nuclear albedo; the largest observed production rates are H and OH which both seem to originate from the photodissociation of H2O, as also confirmed by the scale length of the invisible parent molecule producing OH. However, comet Encke is not uniformly covered by water snow, as it produces only one tenth of the expected vaporization. Early results on comet Kohoutek suggest that the conclusions could be slightly different for some of the new comets in Oort's sense. If the far ultraviolet observations confirm the early assessments of the production rates of C, O and H, then at least another major constituent competing with water has not yet been detected. Such a major constituent is suggested by the ratios C/O = 0.24 and H/O = 2.5.

Delsemme, A. H.↗
NASA NTRS1975

High temperature plasma in beta Lyrae, observed from Copernicus

High-resolution UV spectrophotometry of the complex close binary system beta Lyrae was performed with a telescope spectrometer on board Copernicus. Observations were made at phases 0.0, 0.25, 0.5, and 0.75 with resolutions of 0.2 A (far-UV) and 0.4 A (mid-UV). The far-UV spectrum is completely dominated by emission lines indicating the existence of a high-temperature plasma in this binary. The spectrum of this object is unlike that of any other object observed from Copernicus. It is believed that this high-temperature plasma results from dynamic mass transfer taking place in the binary. The current results are compared with OAO-2 observations and other observational results. The possibility that the secondary component is a collapsed object is also discussed; the Copernicus observations are consistent with the hypothesis that the spectroscopically invisible secondary component is a black hole.

Kondo, Y.↗
NASA NTRS1976

Imaging air pollutants in the near ultraviolet

This paper discusses a program for remote sensing of air pollutants called Multispectral Observation of Pollutants System (MOPS). The broad objective of the program is to photograph 'invisible' gaseous pollutants by combining ultraviolet imaging in several spectral bands with portable data processing equipment. Electronic cameras using solid state imaging arrays of large dynamic range will permit very low contrast images to be electronically ratioed and contrast enhanced, thus bringing out pollutant images which are below the contrast threshold of film. Such photographs will allow synoptic coverage of geographic areas providing source, sink, and flow data on pollutants, and will provide reconnaissance and pointing information for other remote sensors. The principle gases to be mapped by MOPS will be ozone, sulfur dioxide, and nitrogen dioxide.

Norris, D.↗
NASA NTRS1978

Helicopter position stabilizing system

System utilizes vertical gyroscope mounted on telescope handled by onboard observer, to help helicopter pilot fly precise circles over ground target without use of ground observer. Other possible uses include cargo discharge or pickup without ground controller, and hovering over invisible target with known coordinates.

Jenkin, K. R.↗
NASA NTRS1978

Radiative shock dynamics. II - Hydrogen continua

The interaction between radiation and a shock wave propagating through a stellar atmosphere is investigated. Departures from local thermodynamic equilibrium (LTE) are permitted in the first two levels of a 10-level hydrogen atom; levels 3-10 are in LTE. A piston moving at constant velocity into the bottom of the atmosphere drives a shock wave. This shock produces precursor radiation that diffuses through the gas well ahead of the shock and causes a mild luminosity flash in the emergent Balmer and free-free radiation when it reaches the surface. The precursor wave deposits a large amount of radiative energy in the outer layers of the atmosphere, initiating a radiation-induced pressure wave. The process of energy transfer from the radiation field to the compression wave is similar to the Eddington valve mechanism which drives stellar pulsations. Material is accelerated outward by the radiation-induced wave; eventually it free-falls inward, hits the quasistationary atmosphere, and forms an accretion shock. The piston driven shock is weakened by radiative energy losses. When it reaches the surface, the shock is invisible in the continuum radiation.

Klein, R. I.↗
NASA NTRS1978

On the nature of the sources of hard pulse X-ray radiation

Besides the identified sources of cosmic pulse X-ray radiation with globular clusters NGC 6624, NGC 1851 and MXB 1730-335 several new identifications were made. The source in Norma was probably identified with globular cluster NGC 5927, the source in Aquila with globular cluster NGC 6838 (M71), and the source in Puppis with globular cluster NGC 2298. Gamma pulses discovered by the Vela satellites and X-ray pulses thoroughly measured by the SAS-3, Ariel-5, and ANS satellites are thought to be the same phenomenon. The sources of such a radiation must be some kind of peculiarity at the central part of globular clusters; it is most probably a massive black hole. The sources of hard pulse radiation which cannot be identified with globular clusters are considered to be a new kind of galactic object, invisible globular clusters, which are naked nuclei of globular clusters.

Shklovskiy, I. S.↗
NASA NTRS1978

Iodine imaging using spectral analysis

Existing radiographic imaging systems provide images which represent an integration or averaging over the energy spectrum. In order to provide noninvasive angiography it is necessary to image the relatively small amounts of iodine which are available following an intravenous administration. This is accomplished by making use of the special spectral characteristics of iodine. Two methods will be presented. One involves a special grating for encoding the iodine information in the form of a fine line pattern. This is subsequently decoded to provide images of iodinated structures which are otherwise almost invisible. The second method utilizes a scanned X-ray beam which is rapidly switched in the high energy region. In this region, iodine experiences significant variations in the attenuation coefficient while bone and soft tissue do not. An efficient and accurate X-ray detector can be used with scanned X-ray beams. This provides a high degree of sensitivity enabling the visualization of small vessels containing relatively dilute iodine.

Macovski, A.↗
NASA NTRS1979

Signature evaluation of natural targets using high spectral resolution techniques

The concept of 'spectral signature' identification has been applied to LANDSAT and other broad-band multi-spectral scanner data to classify various materials on the earth's surface. A large amount of the spectral information available is invisible, however, to the broad-band sensors. Although the natural targets of interest in remote sensing do not exhibit fine line features such as those associated with gaseous media, there is significant information to be extracted from smoothly varying spectral reflection functions of most natural targets. Subtle variations observed recently in the high resolution 'spectral signatures' of vegetation targets, in particular, promise to open new avenues of application using higher spectral and radiometric resolution techniques. This research was accomplished using a 500-band spectroradiometer system specially adapted to rapid airborne operations

Collins, W.↗
NASA NTRS1980

The unique cosmic event of 1979 March 5

The transient gamma-ray burst observed on March 5, 1979 by the nine spacecraft forming the interplanetary gamma-ray burst network is discussed. Measurements reveal the event to be unlike any previously observed gamma-ray burst or X-ray burster, with a maximum intensity greater than several thousandths erg/sq cm per sec, a rise time of less than 200 microsec, a narrow and featureless initial spike and a regular 8-sec oscillation with a compound pulse shape. The source of the transient has been localized to a region including the supernova remnant N 49 in the Large Magellanic Cloud, at a distance of 55 pc, and a ratio of X-ray point-source steady state to transient emission of less than 10 to the -9th was obtained. The identification of the burst source with the supernova remnant at that distance would require an enormous source output if it was radiated isotropically, and substantially less if beaming is present. Alternatively, the event could be explained by a nearby, invisible neutron star.

Cline, T. L.↗
NASA NTRS1980

Interactive display of molecular models using a microcomputer system

A simple, microcomputer-based, interactive graphics display system has been developed for the presentation of perspective views of wire frame molecular models. The display system is based on a TERAK 8510a graphics computer system with a display unit consisting of microprocessor, television display and keyboard subsystems. The operating system includes a screen editor, file manager, PASCAL and BASIC compilers and command options for linking and executing programs. The graphics program, written in USCD PASCAL, involves the centering of the coordinate system, the transformation of centered model coordinates into homogeneous coordinates, the construction of a viewing transformation matrix to operate on the coordinates, clipping invisible points, perspective transformation and scaling to screen coordinates; commands available include ZOOM, ROTATE, RESET, and CHANGEVIEW. Data file structure was chosen to minimize the amount of disk storage space. Despite the inherent slowness of the system, its low cost and flexibility suggests general applicability.

Egan, J. T.↗
NASA NTRS1982

Observations of B-type supergiants

Methods are presented for determining the effective temperatures, radii and bolometric corrections for B-type supergiants. Absorption lines from hydrogen and from other elements, the H alpha, Balmer progression, and evidence for outflow from the invisible spectrum of these supergiants are considered. Luminosity effects, outflow velocities, and variability in the UV spectrum at high resolution are examined as well as the infrared and radio spectra. Spectroscopic characteristics of the peculiar supergiant P Cyg and superluminous supergiants; X-ray binaries; the properties of the photosphere and mantle; and mass loss are elaborated. A general model for the mantle of B stars is included and the properties of B type stars in the main sequence are compared with those of the B-type supergiants.

Source record↗
NASA NTRS1981

Intergalactic shells at large redshift

The intergalactic shells produced by galactic explosions at large redshift, whose interiors cool by inverse Compton scattering off the cosmic background radiation, have a characteristic angular size of about 1 arcmin at peak brightness. At z values lower than 2, the shells typically have a radius of 0.5 Mpc, a velocity of about 50 km/sec, a metal abundance of about 0.0001 of cosmic values, and strong radiation in H I(Lyman-alpha), He II 304 A, and the IR fine-structure lines of C II and Si II. The predicted extragalactic background emission from many shells, strongly peaked toward the UV, sets an upper limit to the number of exploding sources at z values of about 10. Shell absorption lines of H I, C II, Si II, and Fe II, which may be seen at more recent epochs in quasar spectra, may probe otherwise invisible explosions in the early universe.

Shull, J. M.↗
NASA NTRS1982

The effects of sunspots on solar irradiance

It is pointed out that the darkness of a sunspot on the visible hemisphere of the sun will reduce the solar irradiance on the earth. Approaches are discussed for obtaining a crude estimate of the irradiance deficit produced by sunspots and of the total luminosity reduction for the whole global population of sunspots. Attention is given to a photometric sunspot index, a global measure of spot flux deficit, and models for the compensating flux excess. A model is shown for extrapolating visible-hemisphere spot areas to the invisible hemisphere. As an illustration, this extrapolation is used to calculate a very simple model for the reradiation necessary to balance the flux deficit.

Hudson, H. S.↗
NASA NTRS1981

Hot relativistic winds and the Crab Nebula

Efforts to formulate a self-consistent model of pulsar magnetospheres which links the particle source near the pulsar to the outflowing relativistic wind and couples the wind to the surrounding nebula are reviewed. The use of a relativistic MHD wind is recommended to account for global photon emission and the invisibility of the method of plasma transport. Consideration of a magnetic monopole relativistic wind due to an axially symmetric aligned rotator is combined with calculations of the initial velocity of the wind to show that the flow velocity in such a model will never exceed Mach 1. Extending the solution to the case of a hot relativistic wind at supersonic speeds is noted to yield results consistent with observations of the Crab Nebula

Fujimura, F. S.↗
NASA NTRS1982

A system for measuring thermal activation energy levels in silicon by thermally stimulated capacitance

One method being used to determine energy level(s) and electrical activity of impurities in silicon is described. The method is called capacitance transient spectroscopy (CTS). It can be classified into three basic categories: the thermally stimulated capacitance method, the voltage-stimulated capacitance method, and the light-stimulated capacitance method; the first two categories are discussed. From the total change in capacitance and the time constant of the capacitance response, emission rates, energy levels, and trap concentrations can be determined. A major advantage of using CTS is its ability to detect the presence of electrically active impurities that are invisible to other techniques, such as Zeeman effect atomic absorption, and the ability to detect more than one electrically active impurity in a sample. Examples of detection of majority and minority carrier traps from gold donor and acceptor centers in silicon using the capacitance transient spectrometer are given to illustrate the method and its sensitivity.

Cockrum, R. H.↗
NASA NTRS1982

Wind shear and vortex wake research in UK, 1982

A wind shear and vortex wake and their impact on aircraft were investigated. The systems and advice to help pilots, and rational scientific methods to assist in advising certification authorities and those interested in improving flight safety were developed. Wind Shear and Vortex Wakes are related, they are both invisible enemies of aircraft in the form of large disturbances in the atmosphere, both cause major accidents. Problems of building wakes at airports are is considered. Research on wind shear was initiated by the American FAA following the Boston, New York and Denver accidents to civil airliners. This resulted in: useful advice to pilots about wind shear; better attempts by the meteorologists at forecasting wind shear conditions; and useful ideas for wind shear measurement and warning systems. Three major research tasks are outstanding: (1) Worldwide measurements to give reliable estimates of probability and details of the forms of large wind shears; (2) Developments of real time wind shear measuring systems for ground or airborne use; and (3) Establishing relationships between measured wind shear and the potential hazard to an aircraft, or class of aircraft.

Alan A. Woodfield↗
NASA NTRS1982

A review of the 1979 March 5 transient

Existing observational data and analyses are reviewed for the gamma-ray transient event of Mar. 5, 1979. Differences between the event and classical gamma-ray bursts are summarized, and unusual features of the March 5 event are described. They include the oscillations, time history, intensity, spectrum, and recurrent events. The possible association of the event with a neutron star in the N49 supernova remnant in the Large Magellanic Cloud is examined in detail. The alternative possibility of an invisible source within the Galaxy is also considered.

Cline, T. L.↗