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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Possible near-IR channels for remote sensing precipitable water vapor from geostationary satellite platforms

Remote sensing of troposheric water vapor profiles from current geostationary weather satellites is made using a few broadband infrared (IR) channels in the 6-13 micron region. Uncertainties greater than 20% exist in derived water vapor values just above the surface from the IR emission measurements. In this paper, we propose three near-IR channels, one within the 0.94-micron water vapor band absorption region, and the other two in nearby atmospheric windows, for remote sensing of precipitable water vapor over land areas, excluding lakes and rivers, during daytime from future geostationary satellite platforms. The physical principles are as follows. The reflectance of most surface targets varies approximately linearly with wavelength near 1 micron. The solar radiation on the sun-surface-sensor ray path is attenuated by atmospheric water vapor. The ratio of the radiance from the absorption channel with the radiances from the two window channels removes the surface reflectance effects and yields approximately the mean atmospheric water vapor transmittance of the absorption channel. The integrated water vapor amount from ground to space can be obtained with a precision of better than 5% from the mean transmittance. Because surface reflectances vary slowly with time, temporal variation of precipitable water vapor can be determined reliably. High spatial resolution, precipitable water vapor images are derived from spectral data collected by the Airborne Visable-Infrared Imaging Spectrometer, which measures solar radiation reflected by the surface in the 0.4-2.5 micron region in 10-nm channels and has a ground instantaneous field of view of 20 m from its platform on an ER-2 aircraft at 20 km. The proposed near-IR reflectance technique would complement the IR emission techniques for remote sensing of water vapor profiles from geostationary satellite platforms, especially in the boundary layer where most of the water vapor is located.

Gao, B.-C.↗
NASA NTRS2001

Detection of Soluble and Fixed NH4+ in Clay Minerals by DTA and IR Reflectance Spectroscopy : A Potential Tool for Planetary Surface Exploration

Nitrogen is an essential element for life. It is the only element among the six major biogenic elements, C, O, S, O, P, H, whose presence in the Martian soil has not been positively and directly established. We describe here a study assessing the ability to detect NH4 in soils by two methods: differential thermal analysis (DTA) and infrared (IR) reflectance spectroscopy. Four standard clay minerals (kaolinite, montmorillonite, illite and attapulgite) and an altered tephra sample from Mauna Kea were treated with NH4 in this study. Samples of the NH4-treated and leached clays were analyzed by DTA and infrared (IR) reflectance spectroscopy to quantify the delectability of soluble and sorbed/fixed NH4. An exotherm at 270-280 C was clearly detected in the DTA curves of NH4-treated (non-leached) samples. This feature is assigned to the thermal decomposition reaction of NH4. Spectral bands observed at 1.56, 2.05, 2.12, 3.06, 3.3, 3.5, 5.7 and 7.0 microns in the reflectance spectra of NH4-treated and leached samples are assigned to the sorbed/fixed ammonium in the clays. The montmorillonite has shown the most intense absorbance due to fixed ammonium among the leached samples in this study, as a result of its high cation sorption capacity. It is concluded that the presence of sorbed or fixed NH4 in clays may be detected by infrared (IR) reflectance or emission spectroscopy. Distinction between soluble and sorbed NH4 may be achieved through the presence or absence of several spectral features assigned to the sorbed NH4 moietyi and, specifically, by use of the 4.2 micrometer feature assigned to solution NH4. Thermal analyses furnish supporting evidence of ammonia in our study through detection of N released at temperatures of 270-330 C. Based on these results it is estimated that IR spectra measured from a rover should be able to detect ammonia if present above 20 mg NH4/g sample in the surface layers. Orbital IR spectra and thermal analyses measured on a rover may be able to detect ammonia in soils as well but at higher abundances. The spectral features at 3.06 and 7.0 microns due to bound NH4 in clays and altered Hawaiian tephra appear to be the most promising for detection by orbital spectrometers. If N species are present on Mars the sedimentary deposits may be the best regions to look for them.

Janice, Bishop↗
NASA NTRS1997

Mid-IR Spectra Herbig Ae/Be Stars

Herbig Ae/Be stars are intermediate mass pre-main sequence stars, the higher mass analogues to the T Tauri stars. Because of their higher mass, they are expected form more rapidly than the T Tauri stars. Whether the Herbig Ae/Be stars accrete only from collapsing infalling envelopes or whether accrete through geometrically flattened viscous accretion disks is of current debate. When the Herbig Ae/Be stars reach the main sequence they form a class called Vega-like stars which are known from their IR excesses to have debris disks, such as the famous beta Pictoris. The evolutionary scenario between the pre-main sequence Herbig Ae/Be stars and the main sequence Vega-like stars is not yet revealed and it bears on the possibility of the presence of Habitable Zone planets around the A stars. Photometric studies of Herbig Ae/Be stars have revealed that most are variable in the optical, and a subset of stars show non-periodic drops of about 2 magnitudes. These drops in visible light are accompanied by changes in their colors: at first the starlight becomes reddened, and then it becomes bluer, the polarization goes from less than 0.1 % to roughly 1% during these minima. The theory postulated by V. Grinnin is that large cometary bodies on highly eccentric orbits occult the star on their way to being sublimed, for systems that are viewed edge-on. This theory is one of several controversial theories about the nature of Herbig Ae/Be stars. A 5 year mid-IR spectrophotometric monitoring campaign was begun by Wooden and Butner in 1992 to look for correlations between the variations in visible photometry and mid-IR dust emission features. Generally the approximately 20 stars that have been observed by the NASA Ames HIFOGS spectrometer have been steady at 10 microns. There are a handful, however, that have shown variable mid-IR spectra, with 2 showing variations in both the continuum and features anti-correlated with visual photometry, and 3 showing variations in the emission features only while the continuum level remained unchanged. The first 2 stars mentioned probably have reprocessing envelopes. The other 3 stars gives important clues to the controversy over the geometry of the gas and dust around these pre-main sequence stars: the steady underlying 10 microns continuum and variable features indicates that an optically thick continuum probably arising from an accretion disk is decoupled from the optically thin emission features which may arise in a disk atmosphere. Bernadette Rodgers has joined this monitoring campaign in the near-IR using GRIMII with the goal of detecting variations in the hot dust continuum and the gas density in the dense accretion region close to these stars.

Wooden, Diane↗
NASA NTRS2003

NASA's Far-IR/Submillimeter Roadmap Missions SAFIR and SPECS

The far-IR is rich with information about star, disk and planet formation because protostars emit predominantly in this spectral range, and the radiation can escape from the inherently dusty stellar birth sites. Spectral lines contain particularly valuable information about the cooling, collapse, and chemistry of molecular cloud cores and protostars. However, the interpretation of line intensities and profiles is model-dependent; ultimately, high angular resolution is needed to break model degeneracy and definitively characterize the source. Processes occurring on scales smaller than 10,000 AU (72 arcsec at 140 pc, where the nearest protostellar objects are found) likely affect the stellar initial mass function and determine the product of cloud collapse (Binary star or planetary system? How many planets, and what kind will they be?) The next-generation far-IR observatories SIRTF, SOFIA, and Herschel will revolutionize star formation studies and leave the community yearning for telescopes that operate in this spectral region but provide many orders of magnitude better angular resolution. NASA's space science roadmap includes the JWST-scale Single Aperture Far-IR (SAFIR) telescope and the 1 km maximum baseline far-IR interferometer, SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). I will give the scientific motivation for these missions, describe mission concepts and telescope measurement capabilities, and compare these capabilities with those of the next-generation IR telescopes and with the complementary JWST and ALMA. I will also describe the Space Infrared Interferometric Telescope (SPIRIT), a science and technology pathfinder for SPECS, which could be ready to launch in about a decade. At 100 microns, SAFIR will provide 2.5 arcsec resolution (10 times better than SIRTF), SPIRIT will provide 0.25 arcsec resolution, and SPECS will provide 10 milli-arcsec resolution, which is comparable to that of the Hubble Space Telescope.

Leisawitz, David↗
NASA NTRS2004

Atmospheric Trace Gas Abundances and Stable Isotope Ratios via IR-LIF

We propose to develop new technologies with support provided by PIDDP that will enable the in situ measurements of abundances and stable isotope ratios in important radiatively and biogenically active gases such as carbon dioxide, carbon monoxide, water, methane, nitrous oxide, and hydrogen sulfide to very high precision (0.1 per mil or better for the isotopic ratios, for example). Such measurements, impossible at present, could provide pivotal new constraints on the global (bio)geochemical budgets of these critical species, and could also be used to examine the dynamics of atmospheric transport on Mars, Titan, and other solar system bodies. We believe the combination of solid state light sources with imaging of the IR laser induced fluorescence (IR-LIF) via newly available detector arrays will make such in situ measurements possible for the first time. Even under ambient terrestrial conditions, the LIF yield from vibrational excitation of species such as water and carbon dioxide should produce emission measures well in excess of ten billion photons/sec from samples volumes of order 1 c.c. These count rates can, in principle, yield detection limits into the sub-ppt range that are required for the in situ isotopic study of atmospheric trace gases. While promising, such technologies are relatively immature, but developing rapidly, and there are a great many uncertainties regarding their applicability to in situ IR-LIF planetary studies. We therefore feel PIDDP support will be critical to developing these new tools, and propose a three-year program to combine microchip near-IR lasers with low background detection axes and state-of-the-art HgCdTe detectors developed for astronomical spectroscopy to investigate the sensitivity of IR-LIF under realistic planetary conditions, to optimize the optical pumping and filtering schemes for important species, and to apply the spectrometer to the non-destructive measurement of stable isotopes in a variety of test samples. These studies form the necessary precursors to the development of compact, lightweight stable isotope/trace gas sensors for future planetary missions.

Blake, Geoffrey A.↗
NASA NTRS2013

Cross-correlating Cosmic IR and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources

In order to understand the nature of the sources producing the recently uncovered cosmic infrared background (CIB) fluctuations, we study cross-correlations between the fluctuations in the source-subtracted CIB from Spitzer/IRAC data and the unresolved cosmic X-ray background from deep Chandra observations. Our study uses data from the EGS/AEGIS field, where both data sets cover an approx = 8' x 45' region of the sky. Our measurement is the cross-power spectrum between the IR and X-ray data. The cross-power signal between the IRAC maps at 3.6 micron and 4.5 micron and the Chandra [0.5-2] keV data has been detected, at angular scales approx >20'', with an overall significance of approx = 3.8 sigma and approx. = 5.6 sigma, respectively. At the same time we find no evidence of significant cross-correlations at the harder Chandra bands. The cross-correlation signal is produced by individual IR sources with 3.6 micron and 4.5 micron magnitudes m(sub AB) approx. > 25-26 and [0.5-2] keV X-ray fluxes << 7 × 10(exp -177 erg sq. cm/ s. We determine that at least 15%-25% of the large scale power of the CIB fluctuations is correlated with the spatial power spectrum of the X-ray fluctuations. If this correlation is attributed to emission from accretion processes at both IR and X-ray wavelengths, this implies a much higher fraction of accreting black holes than among the known populations. We discuss the various possible origins for the cross-power signal and show that neither local foregrounds nor the known remaining normal galaxies and active galactic nuclei can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations. local foregrounds, nor the known remaining normal galaxies and active galactic nuclei (AGN) can reproduce the measurements. These observational results are an important new constraint on theoretical modeling of the near-IR CIB fluctuations

Cosmic X-ray Background (CXB)↗
NASA NTRSDate not supplied

Reliable IR Line Lists for N2O and OCS Isotopologues for High Temperature Applications up to 2000 K

To address the needs of planetary and exoplanetary atmosphere studies towards JWST, HWO and future IR astronomy missions, theoretical IR line lists of Carbonyl Sulfide (OCS) and Nitrous Oxide (N2O) are generated to provide complete, reliable, and consistent IR reference data in the range of 0 - 15,000 cm-1, or wavelength longer than 0.67 Å, for temperature up to 2000 K. The line lists are quantum mechanically computed using spectroscopically accurate potential energy surfaces empirically refined with reliable high-resolution experimental data, and high-quality dipole moment surfaces constructed at CCSD(T) level with aug-cc-pVT/Q/5(+d)Z basis and extrapolations to complete basis set limit. The Ames N2O line list includes the primary isotopologue 14N2 16O (denoted "446") with J=0-210 and E' up to 25,000 cm-1, and 11 minor isotopologues of 15N and 17/18O with J=0-150 and lower E' cutoffs. For OCS, Ames "natural" 296 K line list includes 12 most abundant isotopologues. The intensity contribution of OCS minor isotopologues at higher temperature is non-negligible, e.g., 8.6 ± 4.9% at 1000 K. The 16O12C32S (93.7%) and 16O12C34S (4.2%) transitions are computed with J=0-240 and E'< 22,000 cm-1, plus J=0-150 and E' < 16,000 cm-1 for five more minor isotopologues. Reliable Effective Hamiltonian models (e.g., NOSL-296 for 14N2 16O), experimental data collections, and reliable HITRAN or MARVEL levels are combined with quantum rovibrational calculations to deliver accurate and consistent empirical corrections for line positions. The reliability and accuracy of our IR intensity predictions are demonstrated by comparison with available databases, line lists, and experiments, at both room temperature and at high temperature. The line lists will be freely available to public online at ZENODO and NAS data portal. We acknowledge the financial support from NASA XRP and APRA programs.

Planetary↗
NASA NTRS1980

Simultaneous IR and X-ray burst observation of Ser X-1

It has been suggested that the very bright IR bursts observed from the Rapid Burster (MXB 1730-335) are due to Type I X-ray bursts. If the suggestion is correct, similar bright IR bursts may, in general, accompany Type I X-ray bursts. This paper investigates this possibility for one specific case. During the 1977 coordinated worldwide burst watch, simultaneous X-ray and IR observations were made. On 00 h 00 min 25s June 17 UT, a Type I X-ray burst was observed, which was almost certainly emitted by Ser X-1 (MXB 1837+05, 4U1837+04). Simultaneous IR observations failed to detect any bursts.

Lewin, W. H. G.↗
NASA NTRS1984

Far-IR selected star formation regions

Detailed far-IR observations and complemenary submillimeter, 5 GHz continuum and c(18)0 observations of a sample of far-IR selected luminous regions of star formation. The clouds and that the exciting stars lie deep within these condensations. The far-IR sources have diversely shaped 40 micron to 180 micron spectra even through their 60 micron to 100 micron color temperatures are similar. The radio and far-IR results together show that the exciting stars are in clusters containing either zero-age main sequence and pre-main sequence stars or consisting entirely of premain sequence objects. C(18)0 and submillimeter observations imply gas densities approximately .00005 - high enough to make t(sub dust) approximately t(sub gas).

Jaffe, D. T.↗
NASA NTRS1985

High-spatial-resolution studies of young stellar objects. II - A thick disk surrounding Lynds 1551, IRS 5

Heavily oversampled, small (2 arcsec) beam 2 micron maps of the region surrounding Lynds 1551, IRS 5 provide the basis for reconstructing maximum-entropy 'images' which have an effective spatial resolution of about 0.6 arcsec. These images reveal an extended, cusp-like structure surrounding IRS 5. This structure most likely results as light from IRS 5 is scattered in our direction by dust grains located in a thick disk of diameter 1000 AU. The disk is viewed nearly edge-on and has a mass in dust grains of 2 to 5 x 10 to the -5th solar masses. Its polar axis lies along the observed direction of the bipolar mass outflow inferred from molecular line observations of the L1551 cloud. It is possible that the observed infrared disk may represent the inner regions of a much larger thick-disk structure, whose shape derives from the combined effects of disk rotation and the gravitational field of IRS 5.

Strom, S. E.↗
NASA NTRS1986

IR heating of the cometary atmosphere

The transfer of radiation, solar and IR dust, in the cometary atmosphere is analyzed using a six-band radiative transfer model. The first five bands correlate with the strongest IR band of H2O and the sixth corresponds to the bulk of solar energy. The radiation field for each band is calculated as a function of the cometocentric distance using the three-stream approximation. It is observed that the mean intensity of the IR radiation field generated by the dust and the cometary nucleus drops from a very large value of about 40,000 erg/sq cm sec at the surface to 400 erg/sq cm sec at 7 km, rises to a peak value of 500 erg/sq cm sec at 100 km and then falls off monotonically. The causes of these changes in radiation field intensity are discussed. The effect of variation of the IR radiation field on the gas temperature is studied.

Marconi, M. L.↗
NASA NTRS1988

Comparison of satellite IR rain estimates with radar rain observations in hurricanes

Radar-observed rainrates and rain areas obtained for the Hurricanes Frederic (1979), Alicia (1983), and Diana (1984) were used in conjunction with GOES IR data to examine the validity of three satellite IR rain estimation techniques: the Arkin (1983) method, the Negri-Adler-Wetzel (1984) technique, and the convective-stratiform technique of Adler and Negri (1987). The Alicia hurricane was also monitored using the subjective manual technique of Spayd and Scofield (1984). It is shown that the success of IR techniques in identifying areas of rainfall depends on the hurricane feature being addressed. Thus, the three objective IR techniques were unable to identify the locations of radar-observed eyewall and inner band precipitation areas because of strong vertical wind shear in the eyewall and the lack of the vertical extent of stratiform precipitation beneath the central dense overcast.

Morris, K. Robert↗
NASA NTRS1988

Study of nonlinear optical sBs phenomena in mid IR fibers

This is the first reported attempt at investigation of the sBs phenomena in mid IR fibers using externally fed or laser self generated low frequency and microwave frequency phonon waves as diagnostic probes of such processes. The observation of laser excited phonon emissions in the mid IR fiber and direct modulation of CO2 laser pulse transmission by externally imposed low frequency radiation is the first indication of the predicted low sBs threshold in these fibers in the phonon rich mid IR spectral region. The prospect of wide applications of the sBs process in optical switching, phase conjugation and ultimately optical computing and possible deleterious effects in mid IR laser heterodyne spectroscopy, sideband modulation and transmitted power limitation is discussed.

Yu, Chung↗
NASA NTRS1990

Imaging and two-dimensional spectra of the IR-bright galaxy NGC 2146 - A recent low-energy merger?

New data are presented on the IR-luminous galaxy NGC 2146 from several sources: direct imaging in B, R, and H-alpha; IR imaging in the J, H, and K bands; long-slit spectroscopy at optical and IR wavelengths; and scanning etalon observations in H-alpha. The results allow measurement of the interstellar extinction in the dust lane, and estimation of the true luminosity of the galaxy and nuclear regions. The spectra indicate that there is no active nucleus, and measure the changing ratio of forbidden to permitted lines across the galaxy. IR images and colors indicate the existence of a significant population of hot young stars in the central regions of the system. The H-alpha velocity maps show the full radial-velocity pattern, and suggest that the system consists of a disturbed disk and a merging or interacting arm which connects to the inner dust and radio structures. Outer H-alpha and H I structures appear to be the earlier remnants of this spiraling merger.

Hutchings, J. B.↗
NASA NTRS1991

High-resolution CO observations of luminous infrared galaxies with large L(ir)/L(B) ratios - IRAS 10173 + 0828, Zw 049.057, IRAS 17208 - 0014

The Owens Valley mm-wave interferometer has been used for high-resolution (about 3-7 arcsec) mapping of CO emission in three luminous IRAS galaxies: IRAS 17208 - 0014, 15107 + 0724, and IRAS 10173 + 0828. These galaxies are among the most extreme, in terms of their L(ir)/L(B) ratio, for objects in the IRAS Bright Galaxy Surveys. The CO emission detected in the three galaxies originates from a single region centered on the IRAS emission peak. These observations have shown that these galaxies have similar values for the global L(ir)/M(H2) ratio, for the surface density of molecular gas in their central regions and for the extinction toward the nucleus (above 300 mag). A high L(ir)/L(B) ratio seems to be a good predictor for both a high global L(ir)/M(H2) ratio and very large central H2 surface densities.

Planesas, P.↗
NASA NTRS1991

A windswept cometary tail on the Galactic center supergiant IRS 7

High-resolution VLA observations provide evidence of optically thick radio emission from IRS 7, a cool red supergiant star, located at a projected distance of roughly 1 1t-yr from the Galactic center. IRS 7 shows a remarkable tail of ionized gas pointing directly away from the compact nonthermal radio source at the Galactic center, Sgr A(asterisk). Given previous evidence for a strong source of UV emission and for a strong circumnuclear wind emanating from the Galactic center, the free-free emission from IRS 7 and its associated tail are interpreted in terms of the ionization and removal of the circumstellar envelope of the red supergiant either by the ram pressure of the nuclear wind or by the pressure of radiation arising from the immediate vicinity of Sgr A(asterisk). The wind mechanism is preferred because: (1) the force it can potentially exert is much greater; and (2) Sgr A(asterisk) is clearly not a known source of luminous energy in the near-IR, whereas it remains a plausible source of a hot, high-velocity wind. Also considered is the potential effect of a nuclear wind upon the atmospheres of red giants in the inner parsec.

Yusef-Zadeh, F.↗
NASA NTRS1993

Estimation of monthly rainfall over Japan and surrounding waters from a combination of low-orbit microwave and geosynchronous IR data

A method is described for estimating the mean monthly rainfall data for climate studies by combining the geosynchronous IR and low-orbit microwave data. The microwave technique uses the brightness temperature at 37 and 86 GHz from the Special Sensor Microwave/Imager instrument on board the DMSP satellite to define raining areas over water and land, and the 86-GHz scattering signal to assign rain rate based on cloud model-microwave calculations. The IR estimates are initially computed separately, using hourly data from the Japanese Geostationary Meteorological Satellite. Results show that, in areas where the microwave technique performs well, the combined microwave-IR monthly total estimates have better error statistics than either the microwave of the IR techniques individually.

Adler, Robert F.↗
NASA NTRS1991

Need for active structures in future large IR and sub-mm telescopes

The potential of active structures technology for future IR and sub-mm telescopes deployed in space is discussed. A space infrared telescope with an aperture of at least 8 m, operating at about 50 k with surface precision better that 0.5 microns is required for future work in space IR and sub-mm astronomy. Telescope parameters, noise, and sensitivity are discussed. The effects of large scale figure errors are examined and conceptual designs of future space IR and sub-mm telescopes are presented. Possible uses of active structures technology and feedback control in future IR and sub-mm space observatories are suggested.

Rapp, Donald↗