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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 109 records · Page 6
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NASA NTRS1984

Spatial variation analyses of Thematic Mapper data for the identification of linear features in agricultural landscapes

A need exists for digitized information pertaining to linear features such as roads, streams, water bodies and agricultural field boundaries as component parts of a data base. For many areas where this data may not yet exist or is in need of updating, these features may be extracted from remotely sensed digital data. This paper examines two approaches for identifying linear features, one utilizing raw data and the other classified data. Each approach uses a series of data enhancement procedures including derivation of standard deviation values, principal component analysis and filtering procedures using a high-pass window matrix. Just as certain bands better classify different land covers, so too do these bands exhibit high spectral contrast by which boundaries between land covers can be delineated. A few applications for this kind of data are briefly discussed, including its potential in a Universal Soil Loss Equation Model.

Pelletier, R. E.↗
NASA NTRS1986

Spatial variation of the thermal structure of Jupiter's atmosphere

The radiative seasonal model described by Bezard and Gautier for the case of Saturn was adapted to Jupiter. That the atmosphere is radiatively controlled above the 500 mb pressure level and that the temperature at the radiative-convective boundary level is constant for all latitudes is assumed. An internal heat source and absorption by methane and aerosols contribute to atmospheric heating. Absorption by aerosols was adjusted to give a planetary Bond albedo equal to 0.343. Despite Jupiter's low obliquity, the model predicts seasonal variations of temperature of several degrees for the 1 mb pressure level at mid-latitude regions.

Bezanger, C.↗
NASA NTRS1989

Spatial variation and evolution of heliospheric sector structure

The magnetic sector polarity at the sun and in the IMF was surveyed during about three quarters of sunspot cycle 21 using ground-based photospheric magnetic field observations and spacecraft observations, including Voyagers 1 and 2 and Pioneer Venus Orbiter data. The location of the heliospheric current sheet near the sun throughout the period 1977-1985 is calculated. The large-scale magnetic polarity structure was in almost continuous evolution throught this period. IMF polarity patterns derived from spacecraft data are compared with the pattern observed at the sun, showing that sector pattern stability decreases with increasing heliocentric distance.

Behannon, K. W.↗
NASA NTRS1990

Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex

An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator.

Yung, Yuk L.↗
NASA NTRS1990

Spatial variation of the physical conditions of molecular gas in galaxies

Multi-line studies of CO-12, CO-13, C-18O, HCN, and HCO(+) at 3 mm, 1.3 mm, and 0.8 mm using the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope, with the IRAM superconductor insulator superconductor (SIS) receivers and the Max Planck Institute for External Physics (MPE) 350 GHz SIS receiver, show that the densities and temperatures of molecular gas in external galaxies change significantly with position. CO-12 measures the densities and temperature of diffuse interclump molecular gas, but not the bulk of the molecular gas. Simple one-component models, with or without external heating, cannot account for the weakness of the CO-12 J = 3 to 2 line relative to J = 2 to 1 and J = 1 to 0. CO-12 does not trace the bulk of the molecular gas, and optical depth effects obviate a straightforward interpretation of CO-12 data. Instead, researchers turned to the optically thin CO isotopes and other molecular species. Isotopic CO lines measure the bulk of the molecular gas, and HCN and HCO(+) pick out denser regions. Researchers find a warm ridge of gas in IC 342 (Eckart et al. 1989), denser gas in the starburst nucleus of IC 342, and a possible hot-spot in NGC 2903. In IC 342, NGC 2146, and NGC 6764, the CO-13 J = 2 to 1 line is subthermally populated, implying gas densities less than or equal to 10(exp 4) cm(-3).

Jackson, James M.↗
NASA NTRS1989

Spatial variations of the 3 micron emission features within nebulae

The 3 micron spectra is presented for the Orion bar region and the Red Rectangle. In both objects spectra were obtained at more than one location, corresponding to different distances from the excitation source. The well known 3.3 and 3.4 micron emission bands are seen in both objects as well as the recently discovered features at 3.46, 3.51, and 3.57 microns in the Orion bar spectra. The spectra show that the relative strengths of the 3 micron emission features vary within the Orion bar. As distance from the exciting star increases, the 3.4 and 3.51 micron features increase, and the 3.46 micron feature decreases in strength, relative to the strong 3.3 micron feature. These are two possible interpretations which are postulated, each of which involves the breaking of bonds by UV radiation, which removes the modes responsible for the 3.4 micron emission near the star. The two possible bond ruptures are the CH bond in small polycyclic aromatic hydrocarbons (PAHs), or the bond to an aliphatic subgroup. It has to be pointed out that neither interpretation appears entirely satisfactory. The vibrational overtone interpretation cannot explain the presence or behavior of the 3.46 micron feature, whereas the laboratory spectra of aliphatic sidegroups contain many more features in the 3 micron region than are observed in the astronomical sources.

Moorhouse, Alan↗
NASA NTRS1991

The spatial variations of lightning during small Florida thunderstorms

Networks of field mills (FM's) and lightning direction finders (LDF's) were used to locate lightning over the NASA KSC on three storm days. Over 90 percent of all cloud-to-ground (CG) flashes that were detected by the LDF's in the study area were also detected by the LDF's. About 17 percent of the FM CG events could be fitted to either a monopole or a dipole charge model. These projected FM charge locations are compared to LDF locations, i.e., the ground strike points. It was found that 95 percent of the LDF points are within 12 km of the FM charge, 75 percent are within 8 km, and 50 percent are within 4 km. For a storm on 22 Jul. 1988, there was a systematic 5.6 km shift between the FM charge centers and the LDF strike points that might have been caused by the meteorological structure of the storm.

Oram, Timothy D.↗
NASA NTRS1990

Spatial variations in the suprathermal ion distributions during substorms in the plasma sheet

The preinjection and postinjection suprathermal energy spectra of the ion species H(+), O(+), He(+), and He(++) in two events in which substorm-associated particle injections were observed in both the near-earth plasma sheet and farther down the tail were determined using data obtained by the Suprathermal Energetic Ion Charge Analyzer on AMPTE IRM and the Charge Energy Mass Spectrometer on AMPTE CCE. Similar spectral changes were observed in both locations. In both cases, the spectra became harder with injection. Postinjection, the flux decreased exponentially with radial distance. The gradients observed for all ion species were very similar.

Kistler, L. M.↗
NASA NTRS1991

Temporal versus spatial variation in leaf reflectance under changing water stress conditions

Leaf reflectance changes associated with changes in water stress were analyzed in two separate experiments. Results indicate that the variation in reflectance among collections of leaves of a given species all at the same level of water stress is at least as great as the variation in reflectance associated with changes in water stress for a given leaf collection of that species. The implications is that results from leaf reflectance-water stress studies have only limited applicability to the remote sensing of plant canopy water stress.

Cohen, Warren B.↗
NASA NTRS1994

Spatial variation of primordial 3-He in crustal fluids along the East-African Rift system (the Ethiopian and the Kenya Rift section)

(3)He/(4)He compositions are presented for groundwater samples from the Ethiopian segment of the East-Afrikan Rift and from its northern extension, the adjacent Afar region (Djibuti). Helium isotope data are compared to those obtained previously from the Gregory Rift, south of Ethiopia. The distribution pattern of mantle-derived volatiles along the entire East-African-Rift (-from south Kenya to Djibuti-) is discussed and their sources are identified. Helium isotope ratios (R) for samples from the Ethiopian part of the Rift range from 6.3 to 16.0 times the atmospheric ratio (Ra=1.4 x 10(exp -6) and thus show together with a MOR component a considerable hotspot helium component. These mantle helium concentrations are comparable to those observed in groundwaters and volcanic rocks from the Afar plume region in Djibuti. Here R/Ra values range from 9 to 13 times the atmospheric composition, with mantle-derived helium concentrations being higher than at spreading ocean ridges. R/Ra values from Ethiopia and Djibuti are entirely different from those observed in groundwaters at the southerly extending Gregory Rift in Kenya, where R/Ra values scatter between 0.5 and 6. At the northernmost part of the Gregory Rift, close to Ethiopia mantle helium contents are slightly higher, with R/Ra-values varying between 6.5 and 8.0.

Griesshaber, E.↗
NASA NTRS1998

Deuterium Abundance in the Local ISM and Possible Spatial Variations

Excellent HST/GHRS spectra of interstellar hydrogen and deuterium Lyman-(alpha) absorption toward nearby stars allow us to identify systematic errors that have plagued earlier work and to measure accurate values of the D/H ratio in local interstellar gas. Analysis of 12 sightlines through the Local Interstellar Cloud leads to a mean value of D/H = (1.50 +/- 0.10) x 10(exp -5) with all data points lying within +/- l(delta) of the mean. Whether or not the D/H ratio has different values elsewhere in the Galaxy and beyond is a very important open question that will be one of the major objectives of the Far Ultraviolet Spectroscopic Explorer (FUSE) mission.

Linsky, Jeffrey L.↗
NASA NTRS1996

Spatial Variation of the 3.29 and 3.40 Micron Emission Bands Within Reflection Nebulae and The Photochemical Evolution of Methylated Polycyclic Aromatic Hydrocarbons

Spectra of 3 microns emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 microns feature and its most prominent satellite band at 3.40 microns are found. It is shown that: (1) the 3.40 microns band is too intense with respect to the 3.29 microns band at certain positions to arise from hot band emission alone, (2) the 3.40 microns band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (3) the variations in the 3.40 microns to 3.29 microns band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 microns emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 microns emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 microns spectrum of the proto-planetary nebula IRAS 05341 + 0852 with the spectrum of the planetary nebula IRAS 21282 + 5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 microns emission spectra of these objects.

Joblin, C.↗
NASA NTRS2001

Hurricane Directional Wave Spectrum Spatial Variation at Landfall

On 26 August 1998, the SRA at 2.2 km height documented the directional wave spectrum in the region between Charleston, SC, and Cape Hatteras, NC, as Hurricane Bonnie was making landfall near Wilmington, NC. The storm was similar in size during the two flights, but the maximum speed in the NOAA Hurricane Research Division surface wind analysis was 15% lower prior to landfall (39 m/s) than it had been in the open ocean (46 m/s). This was compensated for by its faster movement prior to landfall (9.5 m/s) than when it was encountered in the open ocean (5 m/s), significantly increasing the effective fetch and duration of waves near the peak of the spectrum which propagated in the direction of the storm track. The open ocean wave height variation indicated that Hurricane Bonnie would have produced waves of 11 m significant wave height on the shore northeast of Wilmington had it not been for the continental shelf. The bathymetry distributed the steepening and breaking process across the shelf so that the wavelength and wave height were reduced gradually as the shore was approached. The wave height 5 km from shore was about 4 in.

Walsh, E. J.↗
NASA NTRS1996

Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons

Spectra of 3 micrometers emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 micrometers feature and its most prominent satellite band at 3.40 micrometers are found. It is shown that (i) the 3.40 micrometers band is too intense with respect to the 3.29 micrometers band at certain positions to arise from hot band emission alone, (ii) the 3.40 micrometers band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (iii) the variations in the 3.40 micrometers to 3.29 micrometers band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 micrometers emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 micrometers emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 micrometers spectrum of the proto-planetary nebula IRAS 05341+0852 with the spectrum of the planetary nebula IRAS 21282+5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 micrometers emission spectra of these objects.

NASA Center ARC↗