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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A deep PSPC obervation of the Cyg OB2 association

The Cyg OB2 Association contains six of the fifteen most luminous stars in the Galaxy as well as the most luminous and most heavily reddened Galactic star, Cyg OB2 #12. In addition, the association contains a number of Wolf-Rayet stars, at least one early-type binary (Cyg OB2 #5), and a trapezium-like system (Cyg OB2 #8). Though not physically associated with the association, the X-ray source Cyg X-3 lies within a half degree of the center of the association. The association is a known source of X-rays. The X-ray emission from this region includes a contribution from Cyg X-3, as well as coronal emission from OB stars and hot diffuse gas. The region was extensively sampled by the HEAO-2 IPC (136 ks, which includes a single pointing of 57 ks on the central region of the association). A 3.6 ks PSPC observation of this region was obtained in the AO1 pointing phase. In addition, the four brightest OB stars (Cyg OB2 #5, #8A, #9, and #12) have been extensively monitored with the VLA. These stars show evidence of strong radio variability, and nonthermal radio emission characteristics. Several of these radio observations were taken within about a month of an IPC observation, and the two PSPC observations. We obtained a 19.5 ks exposure of the Cyg OB2 Association using the ROSAT PSPC instrument. Scientific tasks included: (1) extracting the PSPC spectral distributions of the brightest OB stars; (2) comparing the 19.5 ks spectral data with the 3.6 ks spectral data; (3) investigating the long term X-ray variability (15 years); and (4) comparing the X-ray and radio variability.

Waldron, Wayne↗
NASA NTRS1972

New format presentation for infrared spectral emittance data. Infrared spectrometry studies, phase 5

Methods for infrared radiance measurements from geological materials were studied for airborne use over terrains with minimal vegetation. The tasks of the investigation were: (1) calculation of emittance ratios, (2) comparison of IR spectral emittance data with K-band scatterometer data over Pisgah Crater, and (3) standard infrared spectral file. Published papers reporting the research are included.

Lyon, R. J. P.↗
NASA NTRS2009

Visible and Near-IR Reflectance Spectra for Smectite, Sulfate And Perchlorate under Dry Conditions for Interpretation of Martian Surface Mineralogy

Visible and near-IR (VNIR) spectral data for the martian surface obtained from orbit by the MRO-CRISM and OMEGA instruments are interpreted as having spectral signatures of H2O/OH-bearing phases, including smectites and other phyllosilicates, sulfates, and high-SiO2 phases [e.g., 1-4]. Interpretations of martian spectral signatures are based on and constrained by spectra that are obtained in the laboratory on samples with known mineralogical compositions and other physicochemical characteristics under, as appropriate, Mars-like environmental conditions (e.g., temperature, pressure, and humidity). With respect to environmental conditions, differences in the absolute concentration of atmospheric H2O can effect the hydration state and therefore the spectra signatures of smectite phyllosilicates (solvation H2O) and certain sulfates (hydration H2O) [e.g., 5-7]. We report VNIR spectral data acquired under humid (laboratory air) and dry (dry N2 gas) environments for two natural smectites (nontronite API-33A and saponite SapCa-1) to characterize the effect of solvation H2O on spectral properties. We also report spectral data for the thermal dehydration products of (1) melanterite (FeSO4.7H2O) in both air and dry N2 gas and (2) Mg-perchlorate (Mg(ClO4)2.6H2O) in dry N2 environments. Spectral measurements for samples dehydrated in dry N2 were made without exposing them to humid laboratory air.

Morris, R.V.↗
NASA NTRS1990

Iron mineralogy of a Hawaiian palagonitic soil with Mars-like spectral and magnetic properties

Visible and near-IR spectral data for some palagonitic soils from Mauna Kea, Hawaii, are similar to corresponding spectral data for Mars. It is important to understand the composition, distribution, and mineralogy of the ferric-bearing phases for the best spectral analogues because the correspondence in spectral properties implies that the nature of their ferric-bearing phases may be similar to those on Mars. In order to constrain interpretations of the Martian data, a variety of palagonitic soils should be studied in order to establish to what extent differences in their spectral data correspond to differences in the mineralogy of their ferric-bearing phases. Spectral (350-2100 nm), Mossbauer, magnetic, and some compositional data for one of a suite of Hawaiian palagonitic soils are presented. The soil (HWMK1) was collected below the biologically active zone from the sides of a gully cut at 9000 ft elevation on Mauna Kea. The soil was wet sieved with freon into seven size fractions less than 1 mm.

Morris, Richard V.↗
DOE OSTI2015

Geometric properties of commutative subalgebras of partial differential operators

We investigate further algebro-geometric properties of commutative rings of partial differential operators, continuing our research started in previous articles. In particular, we start to explore the simplest and also certain known examples of quantum algebraically completely integrable systems from the point of view of a recent generalization of Sato's theory, developed by the first author. We give a complete characterization of the spectral data for a class of 'trivial' commutative algebras and strengthen geometric properties known earlier for a class of known examples. We also define a kind of restriction map from the moduli space of coherent sheaves with fixed Hilbert polynomial on a surface to an analogous moduli space on a divisor (both the surface and the divisor are part of the spectral data). We give several explicit examples of spectral data and corresponding algebras of commuting (completed) operators, producing as a by-product interesting examples of surfaces that are not isomorphic to spectral surfaces of any (maximal) commutative ring of partial differential operators of rank one. Finally, we prove that any commutative ring of partial differential operators whose normalization is isomorphic to the ring of polynomials k[u,t] is a Darboux transformation of a ring of operators with constant coefficients. Bibliography: 39 titles.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1982

JPL airborne instruments activities

Two instruments intended for flight aboard aircraft for research in advanced remote sensing of the earth are under development: the airborne imaging spectrometer (AIS) and the airborne visible-infrared imaging spectrometer (AVIRIS). The AIS utilizes a 32 x 32 element HgCdTe CCD array to gather 10nm spectral data, initially in the 1.2 to 2.4 micron range, with 32 pixels of cross-track spatial data. The instrument acquires 128 channels of spectral data by using a grating spectrometer whose grating is stepped through four positions during a fraction of an IFOV time on the ground. With an IFOV of 2 mrad, the GIFOV at the design altitude of 3 km is 6m. The instrument has several on-board processing capabilities including ax+b corrections for detector calibration, cross-track and down-track pixel summing, spectral band summing, and variable integration time to allow flight at various altitudes and velocities. The AVIRIS uses a proven scanning mechanism to acquire the spatial data in a whisk broom mode. The spectral coverage is from 0.35 to 2.5 microns at bandwidths ranging from 10 to 20 nm.

Vane, G.↗
NASA NTRS2008

Atomic Data and Spectral Line Intensities for Be-like Ions

Atomic data and collision rates are needed to model the spectrum of optically thin astrophysical sources. Recent observations from solar instrumentation such as SOH0 and Hinode have revealed the presence of hosts of lines emitted by high-energy configurations from ions belonging to the Be-like to the 0-like isoelectronic sequences. Data for such configurations are often unavailable in the literature. We have started a program to calculate the atomic parameters and rates for the high-energy configurations of Be-like ions of the type ls2.21.nl' where n=3,4,5. We report on the results of this project and on the diagnostic application of the predicted spectral lines.

Bhatia, Anand↗
NASA NTRS1988

Effects of solar angle on reflectance from wetland vegetation

A hand-held radiometer was used to gather spectral data from wetland vegetation canopies to determine the effects of solar angle on reflectance. The reflectance of leafless and gramineous canopies was highly dependent on solar angle, while broadleaf canopy reflectance was not. The solar angle effects are quantified, and a method to compensate for differences in solar angle at the time of collection of spectral data is described. It was found that adjusting spectral data for solar angle effects substantially improved remote sensing estimates of biomass.

Gross, M. F.↗
DOE OSTI2020

Fundamental Parameters of ∼30,000 M dwarfs in LAMOST DR1 Using Data-driven Spectral Modeling

M dwarfs are the most common type of star in the Galaxy, and because of their small size are favored targets for searches of Earth-sized transiting exoplanets. Current and upcoming all-sky spectroscopic surveys, such as the Large Sky Area Multi Fiber Spectroscopic Telescope (LAMOST), offer an opportunity to systematically determine physical properties of many more M dwarfs than has been previously possible. Here, we present new effective temperatures, radii, masses, and luminosities for 29,678 M dwarfs with spectral types M0–M6 in the first data release (DR1) of LAMOST. We derived these parameters from the supervised machine-learning code, The Cannon, trained with 1388 M dwarfs in the Transiting Exoplanet Survey Satellite Cool Dwarf Catalog that were also present in LAMOST with high signal-to-noise ratio (>250) spectra. Our validation tests show that the output parameter uncertainties are strongly correlated with the signal-to-noise of the LAMOST spectra, and we achieve typical uncertainties of 110 K in T{sub eff} (∼3%), 0.065 R{sub ⊙} (∼14%) in radius, 0.054 M{sub ⊙} (∼12%) in mass, and 0.012 L{sub ⊙} (∼20%) in luminosity. The model presented here can be rapidly applied to future LAMOST data releases, significantly extending the samples of well-characterized M dwarfs across the sky using new and exclusively data-based modeling methods.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1980

Development of a digital data base for reflectance-related soil information

A digital soils data base established for inclusion of soil reflectance data, physical, chemical, and engineering measurements, and site information is discussed. Initial data are taken from 500 soil samples covering the spectral range of 0.5 to 2.3 microns. Information obtained from each observation includes spectral data, and identification records with the soil and spectral observation parameters. The LARSPEC software system is available to retrieve and manipulate information, and scattergrams of identification and spectral data allow the initiation of statistical analyses of soil data. In addition, soil characteristics, graphical displays of reflectance spectra, and identification information examples are given.

Stoner, E. R.↗
DOE OSTI2016

Atmospheric {sup 41}Ar Plume Tracking of the UF Training Reactor Using a Large-Volume NaI Detector

The ability to track and monitor gaseous radioactive materials is important in the event of a radioactive release such as from a nuclear power plant accident, weapons testing, or other unintended release scenarios. The International Monitoring System (IMS) is currently in place to monitor for weapons testing and has been used to monitor nuclear power plant accidents. However, only 80 radionuclide stations for the IMS exist in the world and are stationary, limiting the resolution of any radioactive plumes detected. Furthermore, the IMS radionuclide stations are designed to be sensitive specifically to atmospheric radio-xenon and no other radionuclides. Historically, monitoring radioactive releases has been limited to the detection of radio-xenon and radio-krypton, both arising as fission products from nuclear fuel. After the accident at Three Mile Island Unit 2, scientists were interested in finding the dose the public received from released radioactive material. This was achieved by analyzing radiation monitors in the exhaust stack and filters within the reactor building. furthermore, a series of 20 thermoluminescent dosimeters (TLD's), 8 air sampling station positioned around Three Mile Island, and a helicopter survey which used a NaI(Tl) detector array provided data on radionuclides, specifically {sup 137}Cs, that escaped the confines of the reactor building. The TLD's and air sampling stations were stationary, and therefore limited the resolution of the radioactive release plume. The helicopter survey using the NaI detectors was limited by the technology available at the time. The NaI detector array output was compressed from 1024 channels to 256 channels, limiting the energy resolution of the spectral data. The helicopter used a microwave ranging system to establish position. Since this survey was taken in October of 1982, advancements in technology allow spectral data to be saved in its full 1024 channel format and the advent of GPS can give a more accurate account of the detector position. An updated mobile system for tracking a radioactive release would help to alleviate these issues as well as gain the ability to track a radioactive release in real-time. We investigate the feasibility of mobile tracking through study and measurement of the {sup 41}Ar plume released from the University of Florida Training Reactor (UFTR) research reactor. We use a large-volume NaI(Tl) detector placed on the roof near the reactor. This detector may also be placed and moved on a cart to survey the area surrounding the reactor. We compare the spectral data taken when the reactor is running at full power to the background to analyze the effectiveness of the detector at identifying atmospheric {sup 41}Ar. Finally we discuss the implications of these measurements with regards to validation of plume models and the capability to track releases over a localized area from the source. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2015

Atomic data and spectral model for Fe II

We present extensive calculations of radiative transition rates and electron impact collision strengths for Fe ii. The data sets involve 52 levels from the 3d{sup 7}, 3d{sup 6}4s, and 3d{sup 5}4s{sup 2} configurations. Computations of A-values are carried out with a combination of state-of-the-art multiconfiguration approaches, namely the relativistic Hartree–Fock, Thomas–Fermi–Dirac potential, and Dirac–Fock methods, while the R-matrix plus intermediate coupling frame transformation, Breit–Pauli R-matrix, and Dirac R-matrix packages are used to obtain collision strengths. We examine the advantages and shortcomings of each of these methods, and estimate rate uncertainties from the resulting data dispersion. We proceed to construct excitation balance spectral models, and compare the predictions from each data set with observed spectra from various astronomical objects. We are thus able to establish benchmarks in the spectral modeling of [Fe ii] emission in the IR and optical regions as well as in the UV Fe ii absorption spectra. Finally, we provide diagnostic line ratios and line emissivities for emission spectroscopy as well as column densities for absorption spectroscopy. All atomic data and models are available online and through the AtomPy atomic data curation environment.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

An interdisciplinary analysis of multispectral satellite data for selected cover types in the Colorado Mountains, using automatic data processing techniques

The author has reported the following significant results. A data set containing SKYLAB, LANDSAT, and topographic data has been overlayed, registered, and geometrically corrected to a scale of 1:24,000. After geometrically correcting both sets of data, the SKYLAB data were overlayed on the LANDSAT data. Digital topographic data were then obtained, reformatted, and a data channel containing elevation information was then digitally overlayed onto the LANDSAT and SKYLAB spectral data. The 14,039 square kilometers involving 2,113, 776 LANDSAT pixels represents a relatively large data set available for digital analysis. The overlayed data set enables investigators to numerically analyze and compare two sources of spectral data and topographic data from any point in the scene. This capability is new and it will permit a numerical comparison of spectral response with elevation, slope, and aspect. Utilization of the spectral and topographic data together to obtain more accurate classifications of the various cover types present is feasible.

Hoffer, R. M.↗
NASA NTRS1992

Emission spectra of selected SSME elements and materials

Stennis Space Center (SSC) is pursuing the advancement of experimental techniques and theoretical developments in the field of plume spectroscopy for application to rocket development testing programs and engine health monitoring. Exhaust plume spectral data for the Space Shuttle Main Engine (SSME) are routinely acquired. The usefulness of this data depends upon qualitative and quantitative interpretation of spectral features and their correlation with the engine performance. A knowledge of the emission spectral characteristics of effluent materials in the exhaust plume is essential. A study of SSME critical components and their materials identified 30 elements and 53 materials whose engine exhaust plume spectral might be required. The most important were evaluated using SSC's Diagnostic Testbed Facility Thruster (DTFT), a 1200-lbf, liquid oxygen/gaseous hydrogen rocket engine which very nearly replicates the temperature and pressure conditions of the SSME exhaust plume in the first Mach diamond. This report presents the spectral data for the 10 most important elements and 27 most important materials which are strongly to moderately emitting in the DTFT exhaust plume. The covered spectral range is 300 to 426 nm and the spectral resolution is 0.25 nm. Spectral line identification information is provided and line interference effects are considered.

Tejwani, Gopal D.↗
NASA NTRS2006

Automated Classification of Thermal Infrared Spectra Using Self-organizing Maps

Existing and planned space missions to a variety of planetary and satellite surfaces produce an ever increasing volume of spectral data. Understanding the scientific informational content in this large data volume is a daunting task. Fortunately various statistical approaches are available to assess such data sets. Here we discuss an automated classification scheme based on Kohonen Self-organizing maps (SOM) we have developed. The SUM process produces an output layer were spectra having similar properties lie in close proximity to each other. One major effort is partitioning this output layer into appropriate regions. This is prefonned by defining dosed regions based upon the strength of the boundaries between adjacent cells in the SOM output layer. We use the Davies-Bouldin index as a measure of the inter-class similarities and intra-class dissimilarities that determines the optimum partition of the output layer, and hence number of SOM clusters. This allows us to identify the natural number of clusters formed from the spectral data. Mineral spectral libraries prepared at Arizona State University (ASU) and John Hopkins University (JHU) are used to test and evaluate the classification scheme. We label the library sample spectra in a hierarchical scheme with class, subclass, and mineral group names. We use a portion of the spectra to train the SOM, i.e. produce the output layer, while the remaining spectra are used to test the SOM. The test spectra are presented to the SOM output layer and assigned membership to the appropriate cluster. We then evaluate these assignments to assess the scientific meaning and accuracy of the derived SOM classes as they relate to the labels. We demonstrate that unsupervised classification by SOMs can be a useful component in autonomous systems designed to identify mineral species from reflectance and emissivity spectra in the therrnal IR.

Roush, Ted L.↗
NASA NTRS1973

Evidence from spectra of bright fireballs

Spectral data with dispersions from 11 to 94 A/mm on 4 fireballs of actual brightness of -4 to -12 magnitude and with velocities of about 30 km/s at 70 to 80 km heights are used for studies of meteor radiation problems. The radiation of fireballs is found to be strongly affected by self absorption. But if the emission curve of growth is used for correction of the self absorption of Fe I lines, a great discrepancy between spectral data and efficiency data for total Fe I light is found. If one assumes that the self absorption is superposed on another effect, a decrease of the dimensions of the radiating volume with increasing lower potential, the spectral data on Fe I lines will be in agreement with the luminous efficiency of total Fe I meteor radiation. Formulas for emission curve of growth and Boltzmann distribution including this effect are derived. This effect is important for fireballs brighter than about -1 or -2 magnitude, while self absorption seems to be important even for fainter meteors.

Ceplecha, Z.↗
DOE OSTI2020

Synergistic ground and orbital observations of iron oxides on Mt. Sharp and Vera Rubin ridge

Visible/short-wave infrared spectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions attributed to hematite at Vera Rubin ridge (VRR), a topographic feature on northwest Mt. Sharp. The goals of this study are to determine why absorptions caused by ferric iron are strongly visible from orbit at VRR, and to improve interpretation of CRISM data throughout lower Mt. Sharp. These goals are achieved by analyzing coordinated CRISM and in situ spectral data along the Curiosity Mars rover’s traverse. VRR bedrock within areas that have the deepest ferric absorptions in CRISM data also have the deepest ferric absorptions measured in situ. This suggests strong ferric absorptions are visible from orbit at VRR because of the unique spectral properties of VRR bedrock. Dust and mixing with basaltic sand additionally inhibit the ability to measure ferric absorptions in bedrock stratigraphically below VRR from orbit. There are two implications of these findings: (1) Ferric absorptions in CRISM data initially dismissed as noise could be real, and ferric phases are more widespread in lower Mt. Sharp than previously reported, (2) Patches with the deepest ferric absorptions in CRISM data are, like VRR, reflective of deeper absorptions in the bedrock. One model to explain this spectral variability is late-stage diagenetic fluids that changed the grain size of ferric phases, deepening absorptions. Curiosity’s experience highlights the strengths of using CRISM data for spectral absorptions and associated mineral detections, and the caveats in using these data for geologic interpretations and strategic path planning tools.

58 GEOSCIENCES↗
NASA NTRS1993

Olivine-rich asteroids, pallasitic olivine and olivine-metal mixtures: Comparisons of reflectance spectra

The recent acquisition of high resolution 0.3 - 2.6 micron reflectance spectra for a number of olivine-rich asteroids permits the analysis of their surface compositions to be made on the basis of new and existing laboratory spectral data for pallasitic olivines and olivine-metal mixtures. Analysis of the spectral data for the latter has revealed a number of spectral parameters which can be used to constrain olivine and metal abundances, grain sizes, and olivine compositions. The following topics are discussed in greater detail: pallasite olivine spectra, olivine-metal mixture spectra, and olivine-rich asteroid spectra.

Cloutis, E. A.↗