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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Observational Evidence for Mixing and Dust Condensation in Core-Collapse Supernovae

Recent findings of isotopic anomalies of Ca-44 (the decay product of Ti-44) and the enhanced ratio of Si-28/Si-30 in SiC grains X, TiC subgrains, and graphite dust grains within primitive meteorites provides strong evidence that these presolar grains came from core-collapse supernovae. The chemical composition of the presolar grains requires macroscopic mixing of newly nucleo-synthesized elements from explosive silicon burning at the innermost zone of the ejects to higher velocities where C exists and where C/O > 1 in either the outer edge of the oxygen zone or in the He-C zone. To date, the only core-collapse supernova observed to form dust is the brightest supernova of the past four centuries, SN1987A in the Large Magellanic Cloud. Observations of SN1987A confirm large scale macroscopic mixing occurs in the explosions of massive stars. Rayleigh-Taylor instabilities macroscopically mix most of the ejects into regions which are still chemically homogeneous and which cool with different time scales. Only small clumps in the ejects are microscopically mixed. Observations show that dust condensed in the ejects of SN1987A after approx.500 days in the Fe-rich gas. Neither silicates nor SiC grains were seen in the dust emission spectrum of SN1987A. SN1987A, the Rosetta Stone of core-collapse supernovae, shows that while the mixing required to explain presolar grains occurs, the rapid cooling of the Fe zone and the sustained high temperatures of the O-Si, O-C, and He-C zones favor the formation of iron-rich rather than oxygen- or carbon-rich grains.

Wooden, Diane↗
NASA NTRSDate not supplied

Long Term Performance Stability of TES Detectors

We are developing superconducting transition-edge sensor (TES) microcalorimeter arrays for a variety of applications such as ground-based laboratory astrophysics experiments and next generation space-based X-ray missions. These detectors can provide X-ray spectral information with an unprecedent resolution of ~2 eV at 6 keV and have been selected for the X-ray Integral Field Unit (X-IFU) instrument of ESA’s large flagship mission Athena. To maintain detector performance over the lifetime of the mission, it is important to understand whether environmental conditions that the detector may be exposed to will affect its properties over time. This “aging” begins right after the array leaves the fabrication environment, with potential exposure to humidity, oxygen, or elevated temperatures which may affect the detector performance. In a few prior arrays we have observed increased fall times in the pulse shape and/or the introduction of anomalous low energy tails on the X-ray spectrum. This is thought to be an indication of “aging” on chips exposed to such conditions, causing e.g. changes in the absorber properties. In this contribution, we report on a systematic characterization of TES properties, before and after exposing the chip to various controlled temperature and humidity levels and assess the changes in the measured transition and pulse shapes, energy resolution, and spectral redistribution.

S Beaumont↗
DOE OSTI2023

Compact single-shot soft X-ray photon spectrometer for free-electron laser diagnostics

The photon spectrum from free-electron laser (FEL) light sources offers valuable information in time-resolved experiments and machine optimization in the spectral and temporal domains. We have developed a compact single-shot photon spectrometer to diagnose soft X-ray spectra. The spectrometer consists of an array of off-axis Fresnel zone plates (FZP) that act as transmission-imaging gratings, a Ce:YAG scintillator, and a microscope objective to image the scintillation target onto a two-dimensional imaging detector. This spectrometer operates in segmented energy ranges which covers tens of electronvolts for each absorption edge associated with several atomic constituents: carbon, nitrogen, oxygen, and neon. The spectrometer’s performance is demonstrated at a repetition rate of 120 Hz, but our detection scheme can be easily extended to 200 kHz spectral collection by employing a fast complementary metal oxide semiconductor (CMOS) line-scan camera to detect the light from the scintillator. This compact photon spectrometer provides an opportunity for monitoring the spectrum downstream of an endstation in a limited space environment with sub-electronvolt energy resolution.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1994

The complex optical to soft x-ray spectrum of the low-redshift radio-quiet quasars

Eight high signal-to-noise ROSAT Position Sensitive Proportional Counter (PSPC) observations of six low-redshift (o.048 less than z less than 0.155) radio-quiet quasars have been analyzed to study ant soft excess. All the spectra can, at least roughly, be described int eh 0.1-2.5 keV band by simple power laws reduced at low energies by Galactic absorption. The strong oxygen edges seen in the PSPC spectra of several Seyfert galaxies and quasars are not observed in this sample. The limits implied for the abount of absorbing gas intrinsic to the quasars are particularly tight: of the order of approximately 10(exp 20)/sq cm. THe range of energy indices is broad: 1.3 less than alpha(sub E) less than 2.3. The energy indices are systematically steeper than those found in the same sources at higher energies (by DELTA alpha(sub E) approximately 0.5-1 with respect to Ginga or EXOSAT (2-10 keV) measurements, and by DELTA alpha(sub E) approximately 0.5 with respect to IPC (0.2-3.5 keV) measurements). This suggests a break between the hard and soft components in the keV region and, therefore, that the PSPC spectra are strongly dominated by the soft compnents. In fact, a fit tot he composite, high signal-to-noise spectrum reveals a significant excess above approximately 1 keV withrespect to the simple power-law model. No evidence for strong emission lines is found in any of the quasars. This argues against emission from an ionized plasma as the main contributor to the soft X-ray compnentunless there is a distribution of te mperatures. If the soft X-ray spectrum of thee quasars is dominated by radiation reflected by the photoinonized surface of an accretion disk, the absence of strong emissionlines suggests high ionization parameters and therefore high accretion rates. We include in two Appendices a comarison of the two official PSPC resolution matrices, those released on1992 March and on 1993 January, a discussion of the amplitude of the residual systematic uncertainties in 1993 January matrix, and a compaison between the PSPC and IPC spectra of a sample of sources.

Fiore, Fabrizio↗
DOE OSTI2021

The Hubble PanCET Program: A Metal-rich Atmosphere for the Inflated Hot Jupiter HAT-P-41b

We present a comprehensive analysis of the 0.3–5 μm transit spectrum for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with Hubble STIS and WFC3 as part of the Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program, and we combine those data with warm Spitzer transit observations. We extract transit depths from each of the data sets, presenting the STIS transit spectrum (0.29–0.93 μm) for the first time. We retrieve the transit spectrum both with a free-chemistry retrieval suite (AURA) and a complementary chemical equilibrium retrieval suite (PLATON) to constrain the atmospheric properties at the day–night terminator. Both methods provide an excellent fit to the observed spectrum. Both AURA and PLATON retrieve a metal-rich atmosphere for almost all model assumptions (most likely O/H ratio of log{sub 10}Z/Z{sub ⊙}=1.46{sub −0.68}{sup +0.53} and log{sub 10}Z/Z{sub ⊙}=2.33{sub −0.25}{sup +0.23}, respectively); this is driven by a 4.9σ detection of H{sub 2}O as well as evidence of gas absorption in the optical (>2.7σ detection) due to Na, AlO, and/or VO/TiO, though no individual species is strongly detected. Both retrievals determine the transit spectrum to be consistent with a clear atmosphere, with no evidence of haze or high-altitude clouds. Interior modeling constraints on the maximum atmospheric metallicity (log{sub 10}Z/Z{sub ⊙}<1.7) favor the AURA results. The inferred elemental oxygen abundance suggests that HAT-P-41b has one of the most metal-rich atmospheres of any hot Jupiters known to date. Overall, the inferred high metallicity and high inflation make HAT-P-41b an interesting test case for planet formation theories.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

Laboratory infrared studies relevant to Io: A satellite to the planet Jupiter

To explain the unidentified spectral features of Io, as obtained by the Voyager infrared spectrometer experiment, the infrared absorption spectra of a number of stable sulfur and oxygen compounds was measured and compared to the Voyager data. Based on the reference absorption bands of Na2SO4 and possibly SO2, the infrared data on Io in the region 700 to 200 per cm appear to represent an emission spectrum. Given the strong evidence for an oxidized crustal environment and the presence of sodium in the Io torus, the absorption spectra of the tested materials support the probability of Na2SO4 occurrence on Io.

Khanna, R. K.↗
NASA NTRS1984

Interstellar O2. II - VUV oscillator strengths of Schumann-Runge lines and prospects for Space Telescope observations

Interstellar molecular oxygen should be detectable in interstellar clouds through observation of its absorption lines in the spectra of background stars. This paper describes and presents the results of measurements of oscillator strengths for some lines in the vacuum ultraviolet (VUV) spectrum of O2. Lines of the (13, 0) through (16, 0) bands of the B 3Sigma(-)u - X 3Sigma(-)g, Schumann-Runge system between 1760 A and 1790 A will be the most suitable for searches for absorption by interstellar O2 with the High Resolution Spectrograph on Space Telescope. The strongest lines in these bands have oscillator strengths of about 3 x 10 to the -5th.

Smith, P. L.↗
NASA NTRS2004

Tissue oxygen measurement system

A device and method in accordance with the invention for determining the oxygen partial pressure (PO.sub.2) of a tissue by irradiating the tissue with optical radiation such that the light is emitted from the tissue, and by collecting the reflected or transmitted light from the tissue to form an optical spectrum. A spectral processor determines the PO.sub.2 level in tissue by processing this spectrum with a previously-constructed spectral calibration model. The tissue may, for example, be disposed underneath a covering tissue, such as skin, of a patient, and the tissue illuminated and light collected through the skin. Alternatively, direct tissue illumination and collection may be effected with a hand-held or endoscopic probe. A preferred system also determines pH from the same spectrum, and the processor may determine critical conditions and issue warnings based on parameter values.

Soller, Babs R.↗
DOE OSTI2025

Computational Study of Indium Oxide Photoelectrodes

Using a combination of first-principles molecular dynamics simulations and electronic structure calculations, we characterize the atomistic structure and vibrational properties of a photocatalytic surface of In 2 O 3 , a promising photoelectrode for the production of hydrogen peroxide. We then investigate the surface in contact with water and show that the electronic states of In 2 O 3 are appropriately positioned in energy to facilitate the two-electron water oxidation reaction (WOR) over the competing four-electron oxygen evolution reaction. In conclusion, we further propose that the use of strained thin films interfaced with water is beneficial in decreasing the optical gap of In 2 O 3 and thus in utilizing a wider portion of the solar spectrum for the WOR.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1979

Ultraviolet spectrum of the Aurora /2000-2800 A/

Ultraviolet spectra between 2000 and 2800 delta-v of an IBC II(+) aurora were obtained by a rocket-borne Ebert-Fastie monochromator at 15-A resolution over Fort Churchill, Manitoba. The v-prime = 0-8 progressions of the N2 Vegard-Kaplan system, the delta-v = 8 sequence of the Lyman-Birge-Hopfield system, and a progression attributed to the Herman-Kaplan system were identified by a synthetic spectrum analysis. Relative populations of the first eight vibrational levels of the A3 Sigma u(+) state at high altitude were obtained from the theoretically generated spectra, and quenching rate coefficients were derived for these eight levels by using an atomic oxygen concentration derived from data from another experiment on board. For v = 0 the quenching rate coefficient was found to be 2.0 times 10 the minus 10th cu cm/sec and was not found to increase for higher vibrational levels. The intensity of the (0,2) band of the Herman-Kaplan system was found to be about 5 times the theoretically predicted value, but even so, the cascade from E3 Sigma g(+) provides less than 2% of the A3 Sigma u(+) state population.

Beiting, E. J., III↗
NASA NTRS1984

Detection of forbidden O I 1S-1D in comet IRAS-Araki-Alcock

Spectra of the forbidden O I 1D-3P 'red' doublet and the 1S-1D 'green' line in Comet IRAS-Araki-Alcock (1983d) were obtained during its close approach to the earth. This is the first unequivocal photoelectric detection of the green line in a cometary spectrum. The population ratio of the O (1S) state to the O (1D) state in the inner coma is not greater than 0.03. This ratio eliminates CO or CO2 and points strongly to H2O as the primary parent for excited oxygen atoms.

Cochran, W. D.↗
NASA NTRS2023

Aurora Detection From Nighttime Lights for Earth and Space Science Applications

This research leverages data from the Day/Night Band (DNB) of the Visible Infrared Imaging Radiometer (VIIRS) instrument onboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite. We demonstrate the value of mining the VIIRS DNB for aurora and describe our use of unsupervised machine learning to create a binary mask for aurora occurrence. This mask can be used to flag aurora-contaminated observations for NASA's nighttime lights products for Earth science applications. The identification of auroral regions can also be used for Space Weather applications, for example, for comparison with aurora forecast model and with other satellite- or ground-based aurora observations. The DNB is a broadband channel that is sensitive to wavelengths from 500 to 900 nm, which covers most of the visible light spectrum, and as the name implies, captures light even at night with a sensitivity at the nanowatt level. This band is suitable for aurora observations since the light emitted by the aurora tends to be dominated by emissions from atomic oxygen, resulting in a greenish glow at a wavelength of 557.7 nm, especially at an altitude of 110 km. This study compares the global nighttime derived aurora regions for 17 and 18 March with the NOAA Space Weather Prediction Center's (SWPC) probability product for the St. Patrick's Day geomagnetic storm in 2015. VIIRS sensors are slated to be added to the next generation of polar-orbiting operational satellites. Our novel automated approach to aurora identification opens up an efficient way to leverage this unique data source.

Aurora↗
NASA NTRS1973

Sediment pattern correlation with inflow and tidal action

The author has identified the following significant results. At the time the two scenes of the Chesapeake Bay Study Area were taken, ground truth data were taken at a number of stations within each of the test areas. Where local conditions permitted, either all or a part of the following parameters were measured: water temperature, spectral transmittance, conductivity, turbidity, dissolved oxygen, current velocity, and pH. In addition, a sample of water was taken at each location and the concentration of suspended material in each sample was determined. In the analysis the relationship of each measured parameter and the corresponding radiance values (reflectance spectrum) detected by the ERTS-1 were evaluated. Thus far, the analysis has shown a good correlation with concentrations of suspended material contained in the water.

Grabau, W. E.↗
DOE OSTI2025

Soft X-ray Emission Spectroscopy of Phosphorus Compounds for Energy Conversion and Storage

Phosphorus (P) is a ubiquitous component of materials for energy conversion and storage. Despite the effectiveness of soft X-ray emission spectroscopy (XES) to characterize these complex materials, XES studies of P-containing compounds are still largely missing. In this investigation, the electronic structure and XES signatures from the P L 2,3 -edge are probed for nine solid-state P-containing compounds characterized by various oxidation states and chemical environments: GaP (3−) , InP (3−) , red-P (0) , H 3 P (3+) O 3 , Na 2 H 2 P 2 (4+) O 6 , H 3 P (5+) O 4 , KH 2 P (5+) O 4 , Na 2 HP (5+) O 4 , and InP (5+) O 4 . The XES spectrum of each material exhibits distinct spectral fingerprints, which provide a robust basis for the speciation of complex P-containing samples. Density functional theory calculations shed light on the electronic structure of selected materials and particularly on the effect of phosphorus-oxygen hybridization. This study provides a comprehensive understanding of P L 2,3 XES spectral fingerprints across a wide range of oxidation states and chemical environments. These data sets and insights pave the way for dedicated future work, such as in situ and operando investigations of P-containing compounds in energy-related applications, where speciation of P compounds is needed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

HD 50896 and the composition of Wolf-Rayet atmospheres

Measurements of the Pickering lines of He II in the spectrum of HD 50896 suggest that the upper limit to the H/He ratio is 0.05 by numbers. Spectral scans from OAO-2 show strong lines, nitrogen being observed most strongly as N IV, but also as N III and N V. Carbon and oxygen are observed dominantly in the triply ionized states. Thus, the degree of ionization of C, N and O are comparable. No indication of extensive selective excitation effects is observed. It is concluded that the differences between the WN and WC stars cannot be explained by selective excitation or ionization effects in the WN stars.

Smith, L. F.↗
NASA NTRS1985

An assessment of the impact of spacecraft glow on the Hubble space telescope. Summary of existing observations and theory

Visible spacecraft glow was first observed on the Atmospheric Explorer spacecraft (AE-E) and studied in some detail with the Visible Airglow Experiment (VAE). The AE-E was a spin-stabilized spacecraft without thrusters at an altitude of 140 to 280 km. The VAE contained six visible wavelength photometers that measured a glow spectrum which: (1) rose steeply in the red, (2) decreased with a cos cubed PH1 dependence from pointing into the ram direction of the spacecraft orbital motion, and (3) decreased in intensity with increasing altitude with the same dependence as the measured atomic oxygen number atmospheric density (O) and not with the measured molecular nitrogen density (N sub 2). It is proposed that the glow is produced by chemical reactions on the spacecraft surface as it sweeps through the atmospheric O, with roughly 5-8 eV per O atom available for excitation from the orbital motion of the spacecraft. This glow may in principal be produced by any of a number of species, including molecular band emission from OH, NO, and NO2. An attempt is made to scale the observed glow to the Hubble space telescope.

Clarke, J. T.↗
NASA NTRS1990

Optical and infrared spectrophotometry of the symbiotic system V1016 Cygni

Spectrophotometry from 0.46 to 1.3 micron of the peculiar emission-line object V1016 Cyg is presented. The optical region displays a weak continuum underlying the rich emission-line spectrum detailed in past studies. The infrared spectrum consists of prominent emission lines of H I, He I, He II, forbidden Ni, O I, and forbidden S III overlying a strong stellar continuum. The latter displays bands at 0.94 micron and 1.13 micron characteristic of a late-type, oxygen-rich giant as well as an absorption at 1.05 micron which is due to VO. The presence of these molecular features indicates a spectral class of M6 or later for the cool secondary. The reddening of the secondary does not appear to be much different from that of the emission lines. Among the infrared emission features is the rarely seen permitted transition of neutral oxygen at 1.1287 micron. Its presence at a strength comparable to O I 8446 A, together with the absence of O I 13164 A, confirms the result of Strafella that the strong O I lines arise primarily from fluorescent excitation by Ly-beta.

Rudy, Richard J.↗
NASA NTRS1993

Theory and observations of electromagnetic ion cyclotron waves in Saturn's inner magnetosphere

High-resolution Voyager 1 magnetic field observations of Saturn's inner magnetosphere are examined for the presence of ULF waves. Quasi-circular left-hand polarized transverse oscillations are found in the near-equatorial region of 5-7 Rs with a wave period about 10 s and peak amplitude of about 2 nT. The wave is identified as the electromagnetic oxygen cyclotron mode occurring at a frequency just below the O(+) ion cyclotron frequency. A theoretical model of wave excitation based on gyroresonant coupling through a temperature anisotropy of O(+) pickup ions is developed which accounts for the principal features of the wave spectrum. It is hypothesized that wave-particle interactions provide a level of scattering commensurate with the weak pitch angle diffusion regime but nonetheless one that regulates and maintains a constant thermal anisotropy of ions along the magnetic field. Arguments are also presented that O(+) was the dominant thermal ion of the Dione-Tethys plasma torus at the time of the Pioneer 11 encounter the year previous to the Voyager 1 measurements.

Barbosa, D. D.↗