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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
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NASA NTRS1981

Longwave infrared observation of urban landscapes

An investigation is conducted regarding the feasibility to develop improved methods for the identification and analysis of urban landscapes on the basis of a utilization of longwave infrared observations. Attention is given to landscape thermal behavior, urban thermal properties, modeled thermal behavior of pavements and buildings, and observed urban landscape thermal emissions. The differential thermal behavior of buildings, pavements, and natural areas within urban landscapes is found to suggest that integrated multispectral solar radiant reflectance and terrestrial radiant emissions data will significantly increase potentials for analyzing urban landscapes. In particular, daytime satellite observations of the considered type should permit better identification of urban areas and an analysis of the density of buildings and pavements within urban areas. This capability should enhance the utility of satellite remote sensor data in urban applications.

Goward, S. N.↗
NASA NTRS1976

The infrared spectrum of Jupiter

The principal characteristics of Jupiter's infrared spectrum are reviewed with emphasis on their significance for our understanding of the composition and temperature structure of the Jovian upper atmosphere. The spectral region from 1 to 40 microns divides naturally into three regimes: the reflecting region, thermal emission from below the cloud deck (5-micron hot spots), and thermal emission from above the clouds. Opaque parts of the Jovian atmosphere further subdivide these regions into windows, and each is discussed in the context of its past or potential contributions to our knowledge of the planet. Recent results are incorporated into a table of atmospheric composition and abundance which includes positively identified constituents as well as several which require verification. The limited available information about spatial variations of the infrared spectrum is presented

Ridgway, S. T.↗
NASA NTRS2015

Late-Time Evolution of Composite Supernova Remnants: Deep Chandra Observations and Hydrodynamical Modeling of a Crushed Pulsar Wind Nebula in SNR G327.1-1.1

In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock(RS) that can occur as a result of a density gradient in the ambient medium and or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a approx. 17,000 yr old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar's motion. We also show that the RSPWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to gamma-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

Evolution↗
NASA NTRS1983

Determination of the Io heat flow. 1: Eclipse observations

The thermal emission from Io during eclipse by Jupiter yields data from which the total thermal flux from the volcanoes on the satellite surface can be estimated. Thermal infrared observations in spectral bands between 3.5 and 30 microns of five Io eclipse reappearances and one eclipse disappearance are reported and discussed. The thermal emission of the volcanoes which occurs almost all of the time was determined from the Io heat flux data. The thermal observations of Io are discussed with respect to previous thermophysical theories.

Sinton, W. M.↗
NASA NTRS1988

Infrared processes in the Jovian auroral zone

In the present theoretical model of the Jovian auroral zone's CH4 and H2 vibrational excitation and deexitation processes, the calculation of the emission intensities of nu3 and nu4 bands of CH3 assume that electrons are the bombarding particles. The most uncertain part of the model calculation involves the energy flux spectrum of incident electrons on the auroral zone. Comparisons with Voyager 1 IRIS observations indicate a domination of the nonthermal, directly or indirectly particle bombardment-derived emission by the thermal emission of the CH4 band.

Kim, Sang J.↗
NASA NTRS1995

ASCA solid state imaging spectrometer observations of O stars

We report ASCA Solid State Imaging Spectrometer (SIS) x-ray observations of the O stars delta Ori and lambda Ori. The energy resolution of the SIS allows us to resolve features in the O star x-ray spectra which are not apparent in spectra obtained by x-ray spectrometers with lower energy resolution. SIS spectra from both stars show evidence of line emission, suggesting the thermal nature of the x-ray source. However, the observed line strengths are different for the two stars. The observed stellar x-ray spectra are not well described by isothermal models although absorbed thermal emission models with two or more temperatures can provide an adequate fit to the data. For both stars we present evidence of absorbing columns significantly larger than the known ISM columns, indicative of absorption by a circumstellar medium, presumably the stellar winds. In addition, the lambda Ori spectrum shows the presence of emission at energies greater than 3 keV which is not seen in the delta Ori spectrum.

Corcoran, M. F.↗
NASA NTRS1994

ASCA solid state imaging spectrometer observations of O stars

We report ASCA Solid State Imaging Spectrometer (SIS) X-ray observations of the O stars delta Ori and lambda Ori. The energy resolution of the SIS allows us to resolve features in the O star X-ray spectra which are not apparent in spectra obtained by X-ray spectrometers with lower energy resolution. SIS spectra from both stars show evidence of line emission, suggesting the thermal nature of the X-ray source. However, the observed line strengths are different for the two stars. The observed stellar X-ray spectra are not well described by isothermal models although absorbed thermal emission models with two or more temperatures can provide an adequate fit to the data. For both stars we present evidence of absorbing columns significantly larger than the known Interstellar Medium (ISM) columns, indicative of absorption by a circumstellar medium, presumably the stellar winds. In addition, the lambda Ori spectrum shows the presence of emission at energies greater than 3 keV which is not seen in the delta Ori spectrum.

Corcoran, M. F.↗
NASA NTRS2001

A Broad-Band X-Ray Study of the Geminga Pulsar

We present a comprehensive study of the Geminga pulsar at energies 0.1-10 keV using data from the ASCA, ROSAT, and EUVE satellites. The bulk of the soft X-ray flux can be parameterized as a blackbody of T = (5.6 +/- 0.6) x 10(exp 5) K, occupying a fraction 0. 10 - 0.64 of the surface area of the neutron star at the parallax distance of 160 pc. The ASCA detection of Geminga resolves the nature of the harder X-ray component previously discovered by ROSAT in favor of nonthermal emission, rather than thermal emission from a heated polar cap. The hard X-ray spectrum can be fitted by a power-law of energy index 1.0 +/- 0.5. The hard X-ray light curve has a strong main peak and a weak secondary peak; its total pulsed fraction is = 55%. Three ROSAT PSPC observations show significant variability of Geminga's light curve. In particular, a peculiar energy dependence of the modulation in the soft X-ray component, dubbed the "Geminga effect" in the original PSPC data, is not present in later observations. In addition, fine structure in the soft X-ray light curve, interpreted as eclipses due to cyclotron resonance scattering by a plasma screen on the closed magnetic field lines, almost disappeared in the most recent observations. All of the variable properties of Geminga can probably be associated with the nonthermal process that supplies e(sup +, sup -) pairs to its inner magnetosphere.

Halpern, Jules P.↗
NASA NTRS2002

Polymer-Single Wall Carbon Nanotube Composites for Potential Spacecraft Applications

Polymer-single wall carbon nanotube (SWNT) composite films were prepared and characterized as part of an effort to develop polymeric materials with improved combinations of properties for potential use on future spacecraft. Next generation spacecraft will require ultra-lightweight materials that possess specific and unique combinations of properties such as radiation and atomic oxygen resistance, low solar absorptivity, high thermal emissitivity, electrical conductivity, tear resistance, ability to be folded and seamed, and good mechanical properties. The objective of this work is to incorporate sufficient electrical conductivity into space durable polyimides to mitigate static charge build-up. The challenge is to obtain this level of conductivity (10(exp -8) S/cm) without degrading other properties of importance, particularly optical transparency. Several different approaches were attempted to fully disperse the SWNTs into the polymer matrix. These included high shear mixing, sonication, and synthesizing the polymers in the presence of pre-dispersed SWNTs. Acceptable levels of conductivity were obtained at loading levels less than one tenth weight percent SWNT without significantly sacrificing optical properties. Characterization of the nanocomposite films and the effect of SWNT concentration and dispersion on the conductivity, solar absorptivity, thermal emissivity, mechanical and thermal properties were discussed. Fibers and non-woven porous mats of SWNT reinforced polymer nanocomposite were produced using electrospinning.

Park, C.↗
NASA NTRS2005

Martian Radiative Transfer Modeling Using the Optimal Spectral Sampling Method

The large volume of existing and planned infrared observations of Mars have prompted the development of a new martian radiative transfer model that could be used in the retrievals of atmospheric and surface properties. The model is based on the Optimal Spectral Sampling (OSS) method [1]. The method is a fast and accurate monochromatic technique applicable to a wide range of remote sensing platforms (from microwave to UV) and was originally developed for the real-time processing of infrared and microwave data acquired by instruments aboard the satellites forming part of the next-generation global weather satellite system NPOESS (National Polarorbiting Operational Satellite System) [2]. As part of our on-going research related to the radiative properties of the martian polar caps, we have begun the development of a martian OSS model with the goal of using it to perform self-consistent atmospheric corrections necessary to retrieve caps emissivity from the Thermal Emission Spectrometer (TES) spectra. While the caps will provide the initial focus area for applying the new model, it is hoped that the model will be of interest to the wider Mars remote sensing community.

Eluszkiewicz, J.↗
NASA NTRS2004

Exceptional Stars Origins, Companions, Masses and Planets

As SIM Interdisciplinary Scientist, we will study the formation, nature and planetary companions of the exotic endpoints of stellar evolution. Our science begins with stars evolving from asymptotic branch giants into white dwarfs. We will determine the parallax and orbital inclination of several iron-deficient post-AGB stars, who peculiar abundances and infrared excesses are evidence that they are accreting gas depleted of dust from a circumbinary disk. Measurement of the orbital inclination, companion mass arid parallax will provide critical constraints. One of these stars is a prime candidate for trying nulling observations, which should reveal light reflected from both the circumbinary and Roche disks. The circumbinary disks seem favorable sites for planet formation. Next, we will search for planets around white dwarfs, both survivors froni the main-sequence stage, and ones newly formed from the circumbinary disks of post-AGB binaries or in white dwarf mergers. Moving up in mass, we will measure the orbital reflex of OB/Be companions to pulsars, determine natal kicks and presupernova orbits, and expand the sample of well-determined neutron star masses. We will obtain the parallax of a transient X-ray binary, whose quiescent emission may be thermal emission from the neutron star, aiming for precise measurement of the neutron star radius. Finally, black holes. We will measure the reflex motions of the companion of what appear to be the most massive stellar black holes. The visual orbits will determine natal kicks, and test the assumptions underlying mass estimates made from the radial velocity curves, projected rotation, and ellipsoidal variations. In addition, we will attempt to observe the visual orbit of SS 433, as well as the proper motion of the emission line clumps in its relativistic jets. Additional information is included in the original document.

Kulkarni, Shrinivas R.↗
NASA NTRS2008

What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?

Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.

Snowden, S. L.↗
NASA NTRS1995

Detection of climate forcing using emission spectra

We discuss the use of thermal emission spectra recorded by satellites to construct climate indices that can detect the evolution of a specific climate forcing in a time series. The two important issues are selectivity against climate forcings other than one that is sought, and sensitivity to the required forcing. We show that indices with selectivity can be found, and that their sensitivity can be high.

Thermal Emission Spectra↗
NASA NTRS1987

Microwave emission above steady and moving sunspots

Two-dimensional maps of radio brightness temperature and polarization, computed assuming thermal emission with free-free and gyroresonance absorption, are compared with observations of active region 2502, performed at Westerbork at lambda = 6.16 cm during a period of 3 days in June 1980. The computation is done assuming a homogeneous model in the whole field of view and a force-free extrapolation of the photospheric magnetic field observed at MSFC with a resolution of 2.34 arcsec. The mean results are the following: (1) a very good agreement is found above the large leading sunspot of the group, assuming a potential extrapolation of the magnetic field and a constant conductive flux in the transition region ranging from .2 x 10 to the 6th to 10 to the 7th erg/sq cm 5; (2) a strong radio source, associated with a new-born moving sunspot, cannot be ascribed to thermal emission. It is suggested that this source may be due to synchrotron radiation by mildly relativistic electrons accelerated by resistive instabilities occurring in the evolving magnetic configuration. An order-of-magnitude computation of the expected number of accelerated particles seems to confirm this hypothesis.

Drago, F. Chiuderi↗
NASA NTRS1967

Mercury's microwave phase effect.

Incompatibility of microwave phase effects measurements in Mercury thermal emission with simple model for thermal behavior of planet surface

ASTRONOMICAL MODEL↗
NASA NTRS2011

Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku

X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant s rim are depleted to approx.0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to approx. 1 solar). The reason for these anomalous abundances is not understood. Here, we examine X-ray spectra in annular sectors covering nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance regions commonly show a strong emission feature at approx.0.7 keV. This feature is likely a complex of He-like O K(gamma + delta + epsilon), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O K(alpha) appears to be too high to be explained as thermal emission. This fact, as well as the spatial concentration of the anomalous abundances in the outermost rim, leads us to propose an origin from charge-exchange processes between neutrals and H-like O. We show that the presence of charge-exchange emission could lead to the inference of apparently "enhanced" metal abundances using pure thermal emission models. Accounting for charge-exchange emission, the actual abundances could be uniformly low throughout the rim. The overall abundance depletion remains an open question. Subject headings: ISM: abundances ISM: individual objects (Cygnus Loop) ISM: supernova remnants X-rays: ISM atomic processes

Katsuda, Satoru↗
NASA NTRS1993

Remote sensing of Earth terrain

Progress report on remote sensing of Earth terrain covering the period from Jan. to June 1993 is presented. Areas of research include: radiative transfer model for active and passive remote sensing of vegetation canopy; polarimetric thermal emission from rough ocean surfaces; polarimetric passive remote sensing of ocean wind vectors; polarimetric thermal emission from periodic water surfaces; layer model with tandom spheriodal scatterers for remote sensing of vegetation canopy; application of theoretical models to active and passive remote sensing of saline ice; radiative transfer theory for polarimetric remote sensing of pine forest; scattering of electromagnetic waves from a dense medium consisting of correlated mie scatterers with size distributions and applications to dry snow; variance of phase fluctuations of waves propagating through a random medium; polarimetric signatures of a canopy of dielectric cylinders based on first and second order vector radiative transfer theory; branching model for vegetation; polarimetric passive remote sensing of periodic surfaces; composite volume and surface scattering model; and radar image classification.

Kong, J. A.↗