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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Distribution and directional fabric of ash-flow sheets in the northwestern Mogollon Plateau, New Mexico.

Individual ash-flow sheets distributed over wide areas in the Mogollon-Datil volcanic province can be delineated and related by flow direction techniques to specific source cauldrons. Two major mid-Tertiary ash flows in the Mogollon Plateau have measurable microscopic directional fabric indicative of primary flow direction imprinted in the ash-flow sheets during late-stage laminar flow. Regional stratigraphic relationships and flow patterns of the ash-flow sheets indicate a late Tertiary origin of the Mogollon Plateau depression. They also show that Basin-Range faulting in southwestern New Mexico was not initiated until after emplacement of the younger ash flow (23 m.y. B.P.). Directional fabric is an inherent property of many calc-alkalic ash-flow sheets and measurement of preferred orientation provides a powerful tool in unravelling the geologic history of complex volcanic terrane.

Rhodes, R. C.↗
NASA NTRS1972

On the nature of some faint infrared stars.

Results of photometric observations of additional Haro-Chavira (H-C) infrared stars, which yield information regarding the nature of these objects. The observations, extending from 0.7 to 3.4 micrometers, were obtained with the 60-in. NASA telescope located at the Catalina Observatory of the University of Arizona. The late M-type spectra of these objects suggests that many of them may be variable. Their apparent concentration to the galactic plane notwithstanding, the fainter late M-type H-C stars must be distinctly less luminous (of luminosity class II or III).

Lee, T. A.↗
NASA NTRS1973

Detection, mapping and estimation of rate of spread of grass fires from southern African ERTS-1 imagery

Sequential band-6 imagery of the Zambesi Basin of southern Africa recorded substantial changes in burn patterns resulting from late dry season grass fires. One example from northern Botswana, indicates that a fire consumed approximately 70 square miles of grassland over a 24-hour period. Another example from western Zambia indicates increased fire activity over a 19-day period. Other examples clearly define the area of widespread grass fires in Angola, Botswana, Rhodesia and Zambia. From the fire patterns visible on the sequential portions of the imagery, and the time intervals involved, the rates of spread of the fires are estimated and compared with estimates derived from experimental burning plots in Zambia and Canada. It is concluded that sequential ERTS-1 imagery, of the quality studied, clearly provides the information needed to detect and map grass fires and to monitor their rates of spread in this region during the late dry season.

Wightman, J. M.↗
NASA NTRS1973

Application of ERTS-1 Imagery to Flood Inundation Mapping

Ground data and a variety of low-altitude multispectral imagery were acquired for the East Nishnabotna River on September 14 and 15. This successful effort concluded that a near-visible infrared sensor could map inundated areas in late summer for at least three days after flood recession. ERTS-1 multispectral scanner subsystem (MSS) imagery of the area was obtained on September 18 and 19. Analysis of MSS imagery by IGSRSL, USGS, and NASA reinforced the conclusions of the low-altitude study while increasing the time period critical for imagery acquisition to at least 7 days following flood recession. The capability of satellite imagery to map late summer flooding at a scale of 1:250,000 is exhibited by the agreement of interpreted flood boundaries obtained from ERTS-1 imagery to boundaries mapped by low-altitude imagery and ground methods.

Hallberg, G. R.↗
NASA NTRS1973

Propagation anisotropies of solar flare protons and electrons at low energies in interplanetary space.

Flux anisotropies in interplanetary space were investigated for protons with E greater than 0.66 MeV and electrons with E greater than 400 keV. Data were taken from the University of Chicago charged-particle telescope aboard the deep-space probe Pioneer 7 and from the Goddard Space Flight Center magnetometer aboard the same spacecraft. Flux anisotropies lying to the east of the average interplanetary magnetic field direction were first reported by McCracken et al. (1971), late in a solar particle event, for proton energies greater than 7.5 MeV. This work extends this investigation to much lower proton energies, studies the proton and electron anisotropies during both early and late phases of a particle event, and makes use of detailed magnetic field data. The investigation consists of two parts, a study of many periods taken at random during solar events, for both protons and electrons, and a detailed analysis of one period, early in an event, during which the magnetic field was near the solar direction.

Pyle, K. R.↗
NASA NTRS1973

A study of B 6 stars.

Because detailed information about the spectra of normal late B type stars is deficient, a study of the spectrum of zeta-Draconis, beta-Sextantis, and alpha-Leonis was undertaken to fill this lack and to provide data for comparison with observations of Bp stars, many of which are of late B spectral type. The study was made from high dispersion spectrograms which cover the spectral region 3100 to 6700 A, and from OAO-II spectral scans covering the spectral region 1100 to 3600 A. Profiles, equivalent widths, and central intensities of many lines in the spectrum of zeta-Draconis and of the major lines of beta-Sextantis are presented. The star alpha-Leonis rotates too rapidly for these measurements to be made from high resolution spectrograms. The star beta-Sextantis is the most massive and hottest of the three stars studied.

Underhill, A. B.↗
NASA NTRS1974

Tectonic analysis of Baja California and Parras shear belt in Mexico

The author has identified the following significant results. Geological correlation of terrain across the Gulf of California using ERTS-1 imagery revealed significant similarities between Isla Tiburon, Isla Angel de la Guarda, and the San Carlos Range in mainland Mexico. ERTS-1 imagery was used to check the validity of the existence of major trans-Baja fault zones. ERTS-1 imagery also shows that high albedo sediments similar to known late Tertiary marine sediments are widespread in southern and middle Baja and extend in places to the eastern side of the Peninsula. Major faults in northern Mexico and across the border in the United States were mapped, and ample evidence was found that the Parras and parts of the Texas lineament are belts of major transverse shear faults in areas outside the supposed limit of the Texas and Parras lineaments. A fundamental concept which may help explain many complexities in the tectonic development is beginning to emerge: The southwestern part of North America was torn by massive left-lateral shear of transverse trend (east-west) during the compressive stage of the late Mesozoic and early Cenozoic. This tectonic style has changed into tensional rifting (Basin and Range) and right-lateral shear later in the Cenozoic and Quaternary.

Abdel-Gawad, M.↗
NASA NTRS1973

Vertex potentials evoked during auditory signal detection - Relation to decision criteria

Vertex potentials were recorded from eight subjects performing in an auditory threshold detection task with rating scale responses. The amplitudes and latencies of both the N1 and the late positive (P3) components were found to vary systematically with the criterion level of the decision. These changes in the waveshape of the N1 component were comparable to those produced by varying the signal intensity in a passive condition, but the late positive component in the active task was not similarly related to the passively evoked P2 component. It was suggested that the N1 and P3 components represent distinctive aspects of the decision process, with N1 signifying the quantity of signal information received and P3 reflecting the certainty of the decision based upon that information.

Squires, K. C.↗
NASA NTRS1975

Detecting Disturbances in a Forest Environment

The interchange between forest and nonforest land and most man-made and natural forest disturbances can be detected on 1:120,000-scale color-infrared film. Bulk multispectral scanner imagery from the Earth Resources Technology Satellite combined and enhanced at a scale of 1:1,000,000 shows major changes in forest and nonforest land-use categories, many timber harvested areas, and some natural disturbances. Late fall to late spring is the best period of the year for detecting forest disturbances. In a study in Georgia, 79 percent of the disturbances in one county were detected on an ERTS color composite for April 1973 with only 12 percent commission error.

Aldrich, R. C.↗
NASA NTRS1975

Metabolic studies of transient tyrosinemia in premature infants

The recently developed technique of gas chromatography-mass spectrometry supported by computer has considerably improved the analysis of physiologic fluids. This study attempted to demonstrate the value of this system in the investigation of metabolite patterns in urine in two metabolic problems of prematurity, transient tyrosinemia and late metabolic acidosis. Serial 24-hr urine specimens were analyzed in 9 infants. Transient tyrosinemia, characterized by 5- 10-fold increases over basal excretion of tyrosine, p-hydroxyphenyllactate, and p-hydroxyphenylpyruvate in urine, was noted in five of the infants. Late metabolic acidosis was seen in four infants, but bore no relation to transient tyrosinemia.

Fernbach, S. A.↗
NASA NTRS1975

Thirteenth-order orbital resonance on a Diademe 2 fragment

A strong thirteenth-order resonance has been observed in an analysis which is based on U.S. Navy tracking data regarding the slowly decaying orbit of a Diademe 2 fragment. The exact commensurability for the orbit occurred in late 1973. The major changes due to the resonance were over by late 1974. Approaches for a significant improvement of thirteenth-order geopotential terms are discussed.

Wagner, C. A.↗
NASA NTRS1975

An algorithm for the space shuttle scheduling problem

The problem of determining launch times for a set of missions is considered. Launch times must satisfy early start time and resource constraints. The investigation reported is concerned with the minimization of the number of missions which are launched after specified late start times. An algorithm is presented which, under certain restrictive assumptions, provides an optimal solution. If the restrictive assumptions are not satisfied, the algorithm may be used to obtain a lower bound on the number of missions flown late.

Fisher, M. L.↗
NASA NTRS1976

Accretion of the terrestrial planets. II

The theory of gravitational accretion of the terrestrial planets is examined. The concept of a 'closed feeding zone' is somewhat unrealistic, but provides a lower bound on the accretion time. A velocity relation for planetesimals which includes an initial velocity component is suggested. The orbital parameters of the planetesimals and the dimensions of the feeding zone are related to their relative velocities. The assumption of an initial velocity does not seriously change the accretion time. Mercury, Venus, and the earth have accretion times on the order of 100 million years. Mars requires well over one billion years to accrete by the same assumptions. The lunar cratering history makes a late formation of Mars unlikely. If Mars is as old as the earth, nongravitational forces or a violation of the feeding zone concept is required. One such possibility is the removal of matter from the zone of Mars by Jupiter's influence. The final sweeping up by Mars would result in the scattering of a considerable mass among the other terrestrial planets. The late postaccretional bombardments inferred for the moon and Mercury may have had this source.

Weidenschilling, S. J.↗
NASA NTRS1976

Martian atmospheric lee waves

Areas of extensive mountain lee wave phenomenon in the northern midlatitudes during late winter are observed in Mariner 9 television pictures of Mars. The lee wave pattern is due to the discrete spectrum of waves generated by a crater ridge in an airstream. The cloud patterns resulting from the waves generated by the flow across a mountain or crater are dependent on the velocity profile of the airstream and the vertical stability of the atmosphere. A two-layer velocity model of the airstream is used in calculations based on the theory of mountain lee waves. Regardless of the simple model used for the airstream, the calculations appear to be capable of reproducing the observed wave patterns. The many observations of lee waves suggest that the near surface wind speeds as implied by the lower stream velocities do not greatly exceed, and most of the time are less than, 40 m/sec in the northern midlatitudes during late winter except possibly on a very localized scale. Results are in agreement with circulation models, especially the Leovy and Mintz (1969) two-layer numerical model.

Pirraglia, J. A.↗
NASA NTRS1976

Five-color photoelectric photometry of asteroid 433 Eros

Five-color (UVBGR) photoelectric light curves of Eros are presented which were obtained on nine nights during the asteroid's 1974/75 close apparition. Indications that three reversals occurred in the relative depths of the two minima between late December 1974 and late January 1975 are noted along with definite evidence of phase reddening. The maximum amplitude observed was 1.44 magnitudes, and the absolute visual magnitude at primary maximum (corrected to zero phase and to 1 AU from the earth and the sun) was about 10.8 magnitudes. Since the observations indicate that Eros has no significant rotational color variations, it is suggested that the light-curve amplitudes are due primarily to the asteroid's shape and to shadowing effects. Based on its colors relative to the sun, it is concluded that Eros appears to be an S-type asteroid.

Miner, E.↗
NASA NTRS1976

A survey of mass-loss effects in early-type stars

Intermediate-resolution data obtained with the Copernicus satellite are surveyed in order to define the region in the H-R diagram where mass loss occurs. The survey includes 40 stars, providing good coverage of supergiants from O4 to A2 and main-sequence stars from O4 to B7 as well as spotty coverage of late O giants and intermediate to late B stars. The spectral transitions examined are primarily resonance lines of ions of abundant elements plus some lines arising from excited states (e.g., C III at 1175.7 A and Si IV at 1122.5 A). Observed P Cygni profiles are discussed along with interesting features of some individual profiles. The data are shown to indicate that mass-loss effects occur over a wide portion of the H-R diagram, that mass ejection generally occurs when the holometric magnitude is greater than -6.0, and that the mass-ejection rate is usually high enough to produce P Cygni profile whenever the N V feature at 1240 A is present in a spectrum.

Snow, T. P., Jr.↗
NASA NTRS1977

Airborne far-infrared observations of the galactic center region

Maps of a region 10 arcmin in diameter around the galactic center made simultaneously in three wavelength bands at 30, 50, and 100 microns with about 1 arcmin resolution are presented, and the distribution of far-IR luminosity and color temperature across this region is derived. The position of highest far-IR surface brightness coincides with the peak of the late-type stellar distribution and with the H II region Sgr A West. The high spatial and temperature resolution of the data is used to identify features of the far-IR maps with known sources of near-IR, radio continuum, and molecular emission. The emission mechanism and energy sources for the far-IR radiation are analyzed qualitatively, and it is concluded that all of the observed far-IR radiation from the galactic-center region can be attributed to thermal emission from dust heated both by the late-type stars and by the ultraviolet sources which ionize the H II regions. A self-consistent model for the far-IR emission from the galactic-center region is presented. It is found that the visual extinction across the central 10 pc of the Galaxy is only about 3 mag and that the dust density is fairly uniform in this region. An upper limit of 10 million suns is set on the luminosity of any still unidentified source of 0.1- to 1-micron radiation at the galactic center.

Gatley, I.↗
NASA NTRS1977

Extension of atomic nitrogen measurements into the lower thermosphere

Special operating modes of the open source neutral mass spectrometer (OSS) on the Atmosphere Explorer C permit the measurement of odd nitrogen (N + NO) number densities between 180 and 450 km. By using optical measurements of NO concentrations from the ultraviolet nitric oxide experiment on AE-C, number densities of N are obtained. Altitude profiles for the midlatitude legs of three orbits in the late spring of 1974 are presented and compared with densities predicted by the AE-C (OSS) empirical N model at 375 km. Atomic nitrogen appeared to be in diffusive equilibrium at least above 200 km in each of the orbits studied. A typical number density of N at 200 km, 0900 LST, and 40 deg N latitude in late May 1974 is 30 million per cu cm.

Engebretson, M. J.↗