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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 217 records · Page 12
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NASA NTRS1989

Determining experimentally induced variation in coniferous canopy chemistry with Airborne Imaging Spectrometer data

Experimental treatments in a Douglas-fir forest in NE New Mexico were carried out to determine whether differences in forest canopy chemistry could be detected using data from the Airborne Imaging Spectrometer (AIS-2). Experimental treatments consisted of nitrogen fertilizer additions, sawdust additions, and control plots. After AIS-2 data were collected, the digital number of a given pixel was extracted from each channel, yielding 128 values that were used to form a spectrum. Four spectra were extracted from each treatment plot. Multiple stepwise linear regressions between first and second difference transformations of AIS-2 spectra and the canopy characteristics of biomass, nitrogen concentration, and nitrogen content were performed. The results showed a coefficient of multiple determination of 0.71 between first-difference AIS-2 spectra and measured nitrogen concentration in foliage, indicating that it may be possible to predict nitrogen concentration in Douglas fir using AIS-2 spectra.

Swanberg, N. A.↗
NASA NTRS1991

Far-infrared lines from G45.13 + 0.14 A and K3-50 A - Density fluctuations in compact H II regions

Properties of two compact H II regions, K3-50 A and G45.13 + 0.14 A, were investigated by measuring FIR fluxes from forbidden O III 51.8 and 88.4 micron lines, forbidden N III 57.3 micron line, forbidden S III 33.5 micron line, and forbidden Ne III 36.0 micron line of these regions, using a cooled grating spectrometer on NASA's Kuiper Airborne Observatory. For both H II regions, the ratio of the two FIR O(2+) lines indicates an electron density of about 1000/cu cm, which for K3-50 A is a factor of 10 to 100 lower than the density determined from optical line observations of the lower excitation species S(+) and N(+) and than the peak rms density deduced from radio continuum measurements by Turner and Matthews (1984). Detailed spherically symmetric models of the two sources were constructed using all available measurements.

Colgan, Sean W. J.↗
NASA NTRS1990

Comparison between two vegetation indices for measuring different types of forest damage in the north-eastern United States

The relative effectiveness of the Landsat TM-derived normalized difference vegetative index (NDVI) and the short-wave IR to NIR ratio (SWIR/NIR) index was examined in measurements of different types of damage in several forest communities. The forests examined included a site with well-defined fir waves in New Hampshire, a site undergoing well-documented coniferous forest decline in Vermont, and predominantly deciduous regions in Vermont and northwestern Massachusetts seriously impacted by pear thrips. Both NDVI and SWIR/NIR images were produced for each area. Results demonstrated that the SWIR/NIR index was superior to NDVI in distinguishing between high and low conifer damage at both fir-wave and forest decline sites; high and low deciduous-forest damage sites were easily separable using either NDVI or SWIR/NIR, but the NDVI was superior in separation between medium and low deciduous damage.

Vogelmann, J. E.↗
NASA NTRS1991

The joint far-infrared-optical luminosity function for spiral galaxies and data for the Abell 400 and Cancer clusters

Visual and IRAS data for an optically selected sample of 183 late-type galaxies are compiled in tables and graphs and analyzed in detail to determine the joint FIR-optical luminosity function Psi from the FIR/blue luminosity ratio, r = L(FIR)/L(B). It is found that Psi can be approximated by a function of a single variable psi(r-prime), where r-prime is defined as r times L(B)/L(asterisk) exp -delta, with L(asterisk) a constant and delta = about 0.08. A lognormal curve peaking at r-prime = 0.35 and with dispersion of 0.28 is shown to give a good fit to psi(r-prime). From a lack of galaxies with very low r-prime in the present sample it is inferred that there are few spiral galaxies with low interstellar-dust abundances. Also included are data on the distribution function of r-prime for the more distant clusters Abell 400 and Cancer.

Corbelli, Edvige↗
NASA NTRS1991

The 158 micron forbidden C II line - A measure of global star formation activity in galaxies

Some 158 micron forbidden C II fine structure line observations from a sample of fourteen gas rich galaxies are reported. These measurements confirm and generalize previous basic results that the C II line is bright amounting to approximately 0.1 to 1 percent of the FIR luminosity of the nuclear regions of galaxies; the C II line is formed in the warm (temperature of the gas is greater than 200 K), dense (n sub H greater than 1000/cu cm) photodissociated gas at the interfaces between giant molecular clouds and ionized gas regions and is therefore associated with the molecular gas component in spiral galaxies; the C II line tracks the FIR continuum in a manner consistent with the PDR models; the integrated C II to isotope (C-12)D (transition 1 to 0) line ratio is large (greater than or equal to 1000) in all galaxies studied, and is similarly large for galactic molecular clouds; the C II line is therefore energetically very important for the study of giant molecular clouds. Conclusions obtained from these results are given.

Stacey, G. J.↗
NASA NTRS1991

Correlations between the far-infrared, radio, and blue luminosities of spiral galaxies

FIR-radio luminosity correlations are presently derived for two statistically complete samples spanning a wide luminosity range. While observed correlations are tight, they are not linear; the observed scattering is mostly intrinsic. An empirical correction to the radio luminosities, based on observed blue luminosities, makes the corrected FIR-radio correlation linear and eliminates most of the residual variance. A two-component model that is consistent with the improved correlation is proposed for the heating luminosity within galaxies. The first, radio-loud component contains young massive stars that heat the dust, while contributing to the cool cirrus dust-heating interstellar radiation field. The second, radio-quiet component is made up of less massive older stars.

Condon, J. J.↗
NASA NTRS1991

Windows in the Milky Way

The objectives were twofold: (1) to study the IRAS emission levels in the vicinity of Baade's Window and in other optically transparent regions near the Galactic Center; and (2) to study the IRAS emission levels along sightlines in the Milky Way that exhibit very little CO emission. Tests were attempted to see whether the optically transparent 'windows' near the Galactic center can be identified (as FIR-weak regions) in the IRAS data base; and if so, whether the CO weak regions found elsewhere in the Milky Way represent similarly FIR weak and thus optically transparent sightlines through the Galaxy. The CO weak regions were also targeted in an effort to study the diffuse intercloud dust and its warming by the interstellar radiation field.

Waller, William H.↗
NASA NTRS1991

Preliminary spectral observations of the Galaxy with a 7 deg beam by the Cosmic Background Explorer (COBE)

The FIR absolute spectrophotometer (FIRAS) on the Cosmic Background Explorer (COBE) has carried out the first all-sky spectral line survey in the FIR region, as well as mapping spectra of the Galactic dust distribution at below 100 microns. Lines of forbidden C I, C II, and N II, as well as of CO are all clearly detected. The mean line intensities are interpreted in terms of the heating and cooling of the multiple phases of the interstellar gas. In addition, an average spectrum of the galaxy is constructed and searched for weak lines. The spectrum of the galaxy observed by FIRAS has two major components: a continuous spectrum due to interstellar dust heated by starlight, and a line spectrum dominated by the strong 158-micron line from singly ionized carbon, with a spatial distribution similar to the dust distribution, and a luminosity of 0.3 percent of the dust luminosity. There are in addition moderately strong 122- and 205.3-micron lines, identified as coming from singly-ionized nitrogen. Maps of the emission by dust and forbidden C II and N II are presented.

Wright, E. L.↗
NASA NTRS1992

High angular resolution far-infrared observations of Sagittarius B2

High-angular-resolution FIR observations of the continuum emission from the Sagittarius B2 molecular cloud core are reported. Evidence is found for a significantly spatially extended component of the FIR emission at 50- and 100-micron wavelength, which has an angular extent of 1 x 2 arcmin. Its approximate spatial coincidence with a low-level extended component of the radio free-free emission and with the portion of the SGR B2 core having densities not less than 10 exp 5 cu cm derived from molecular observations suggests that the ionizing radiation from the massive stars in the compact sources is diffusing through a region with a beam-averaged visual extinction not less than a few hundred mag. It is inferred that the gas and the dust in the central portion of the cloud surrounding the compact radio free-free/FIR sources are highly clumped.

Goldsmith, Paul F.↗
NASA NTRS1992

The structure of NGC at 100, 160, and 200 microns - Continuum dust emission in a quiescent Sb galaxy

Observations of NGC 4565 at 100, 160, and 200 microns with the University of Chicago Far-Infrared Camera and the NASA-Kuiper Airborne Observatory are reported. In order to examine the dependence of FIR emission on spiral structure and star formation activity, these observations of NGC 4565, a quiescent Sb galaxy, are compared with observations of NGC 6946, an active Sc galaxy, made by Engargiola (1991) using the same instruments. Warm dust (30 K) in a bisymmetric spiral pattern superposed on an exponential disk of cool dust (20 K) can account for the FIR morphology of NGC 4565. Optical and IR data suggest that there are more embedded sources heating dust locally in the southeast arm region and more UV radiation from unobscured young stellar associations heating the cool, neutral medium in the northeast arm region.

Engargiola, G.↗
NASA NTRS1992

The compactness of far-infrared bright galaxies

The linear size distribution of 218 galaxies in the IRAS infrared bright galaxy sample is studied by examining new measurements of the 1.49 Hz radio continuum emitting regions. We find that the radio surface brightness varies over a wide range at a given luminosity, but its median scales approximately as luminosity to the power of 6/5. Consequently, the median effective radio size of galaxies in a given luminosity range actually decreases with increasing luminosity, especially among galaxies with LFIR greater than 10 exp 11 solar luminosities. The close correlation between FIR and radio fluxes of these star-forming galaxies then leads to a picture contrary to earlier theoretical predictions that the sizes of FIR emitting regions should increase with luminosity. We propose that such a steep increase of surface brightness in luminous galaxies is a direct result of a high interstellar medium density and an enhanced radiation density of the heating photons driven by more active star formation.

Wang, Zhong↗
NASA NTRS1992

Far-infrared spectral studies of phase changes in water ice induced by proton irradiation

Changes in the FIR spectrum of crystalline and amorphous water ice as a function of temperature are reported. The dramatic differences between the spectra of these ices in the FIR are used to examine the effect of proton irradiation on the stability of the crystalline and amorphous ice phases from 13 to 77 K. In particular, the spectra near 13 K show interconversion between the amorphous and crystalline ice phases beginning at doses near 2 eV/molecule and continuing cyclically with increased dose. The results are used to estimate the stability of irradiated ices in astronomical environments.

Moore, Marla H.↗
NASA NTRS1993

Effect of Malmquist bias on correlation studies with IRAS data base

The relationships between galaxy properties in the sample of Trinchieri et al. (1989) are reexamined with corrections for Malmquist bias. The linear correlations are tested and linear regressions are fit for log-log plots of L(FIR), L(H-alpha), and L(B) as well as ratios of these quantities. The linear correlations for Malmquist bias are corrected using the method of Verter (1988), in which each galaxy observation is weighted by the inverse of its sampling volume. The linear regressions are corrected for Malmquist bias by a new method invented here in which each galaxy observation is weighted by its sampling volume. The results of correlation and regressions among the sample are significantly changed in the anticipated sense that the corrected correlation confidences are lower and the corrected slopes of the linear regressions are lower. The elimination of Malmquist bias eliminates the nonlinear rise in luminosity that has caused some authors to hypothesize additional components of FIR emission.

Verter, Frances↗
NASA NTRS1993

Dust temperature distributions in star-forming condensations

The FIR spectra of the central IR condensations in the dense cores of molecular clouds AFGL 2591. B335, L1551, Mon R2, and Sgr B2 are reanalyzed here in terms of the distribution of dust mass as a function of temperature. FIR spectra of these objects can be characterized reasonably well by a given functional form. The general shapes of the dust temperature distributions of these objects are similar and closely resemble the theoretical computations of de Muizon and Rouan (1985) for a sample of 'hot centered' clouds with active star formation. Specifically, the model yields a 'cutoff' temperature below which essentially no dust is needed to interpret the dust emission spectra, and most of the dust mass is distributed in a broad temperature range of a few tens of degrees above the cutoff temperature. Mass, luminosity, average temperature, and column density are obtained, and it is found that the physical quantities differ considerably from source to source in a meaningful way.

Xie, Taoling↗
NASA NTRS1991

Remote sensing of atmospheric chemistry; Proceedings of the Meeting, Orlando, FL, Apr. 1-3, 1991

The present volume on remote sensing of atmospheric chemistry discusses special remote sensing space observations and field experiments to study chemical change in the atmosphere, network monitoring for detection of stratospheric chemical change, stratospheric chemistry studies, and the combining of model, in situ, and remote sensing in atmospheric chemistry. Attention is given to the measurement of tropospheric carbon monoxide using gas filter radiometers, long-path differential absorption measurements of tropospheric molecules, air quality monitoring with the differential optical absorption spectrometer, and a characterization of tropospheric methane through space-based remote sensing. Topics addressed include microwave limb sounder experiments for UARS and EOS, an overview of the spectroscopy of the atmosphere using an FIR emission experiment, the detection of stratospheric ozone trends by ground-based microwave observations, and a FIR Fabry-Perot spectrometer for OH measurements.

Mcelroy, James L.↗
NASA NTRS1994

Balloon measurements of stratospheric HCl and HF by far infrared emission spectroscopy

We have analyzed atmospheric thermal emission spectra obtained with the balloon-borne FIRS-2 far infrared Fourier transform spectrometer during balloon flights from Palestine, Texas on May 12-13, 1988 and from Fort Sumner, New Mexico on September 26-27, 1989 and on July 4-5, 1990. Seven and two pure rotational transition lines in 100-205 cm(exp -1) range are analyzed for deriving vertical profiles of stratospheric HCl and HF, respectively. We obtain both the daytime and nighttime average vertical profiles from 15 to 50 km. We compare these profiles with the ones obtained in June, 1983 with the first version of FIRS spectrometer during the Balloon Intercomparison Campaign (BIC-2). BIC-2 results were revised to be consistent with the present analysis which uses the latest spectral parameters. According to our comparison results no increase is recognized for HCl but about 3 percent per year increase for HF from 1983 to 1990, assuming a linear trend. These annual increase rates are smaller than those reported by other groups. Recently Rinsland et al. (1991) and Wallace and Livingston (1991) reported long term behavior of total HCl and HF observed on Kit Peak between 1977 and 1990. As Kit Peak is located near both balloon launching sites, Palestine and Fort Sumner, we think our results are favorably comparable with theirs. Comparison results with ours and ground-based measurements will be presented and discussed.

Shibasaki, Kazuo↗
NASA NTRS1994

Low-complexity wavelet filter design for image compression

Image compression algorithms based on the wavelet transform are an increasingly attractive and flexible alternative to other algorithms based on block orthogonal transforms. While the design of orthogonal wavelet filters has been studied in significant depth, the design of nonorthogonal wavelet filters, such as linear-phase (LP) filters, has not yet reached that point. Of particular interest are wavelet transforms with low complexity at the encoder. In this article, we present known and new parameterizations of the two families of LP perfect reconstruction (PR) filters. The first family is that of all PR LP filters with finite impulse response (FIR), with equal complexity at the encoder and decoder. The second family is one of LP PR filters, which are FIR at the encoder and infinite impulse response (IIR) at the decoder, i.e., with controllable encoder complexity. These parameterizations are used to optimize the subband/wavelet transform coding gain, as defined for nonorthogonal wavelet transforms. Optimal LP wavelet filters are given for low levels of encoder complexity, as well as their corresponding integer approximations, to allow for applications limited to using integer arithmetic. These optimal LP filters yield larger coding gains than orthogonal filters with an equivalent complexity. The parameterizations described in this article can be used for the optimization of any other appropriate objective function.

Majani, E.↗
NASA NTRS1994

VV 114, a high infrared luminosity interacting galaxy system

VV 114 is a nearby example of a far-infrared (FIR) bright, high luminosity (L(sub FIR) greater than 10(exp 11) solar luminosity) interacting galaxy pair. At a redshift of z = 0.02 it provides an opportunity to study such interacting galaxies at a favorable spatial scale (390 pc/arcsec). This paper presents new high resolution near-infrared (1.25 to 3.7 micrometer) and visible images, and visible spectra of VV 114. A picture emerges of a system with widespread massive star formation throughout both interacting galaxies. The brighter visible galaxy (VV 114W) shows H II region-like emission in both visual spectra and near-infrared colors, with no more than two magnitudes of visual extinction. The brightest peak of infrared and radio emission (VV 114E) has extreme near-infrared colors and is located at a minimum of visible emission. This indicates a large concentration of dust in the nucleus of VV 114E that is nearly entirely obscuring a major luminosity source in this system.

Knop, R. A.↗