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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Standoff Detection of Chemical Plumes Using Swept-ECQCL Remote Detection Technology: Results from EMRTC Complex Terrain Dual Tracer Experiment

As part of the Complex Terrain Dual Tracer Experiments performed in support of the LYNM program, a swept-wavelength external cavity quantum cascade laser (swept-ECQCL) remote detection system was deployed to measure chemical plume propagation with high temporal resolution. The swept-ECQCL remote detection technology was initially developed at PNNL, and is now under further development at Opticslah, LLC under SBIR funding from DOE (DOE SBIR Phase I Project DE-SC0019855, Remote Detection Technologies, Program Manager Chris Ramos). The swept-ECQCL technology provides a single-frequency infrared laser source which is rapidly scanned over a large wavelength range to measure the infrared absorption of gases, liquids, or solids. Analysis of the measured infrared absorption spectrum is used to detect, identify, and quantify the chemical species which are present. While most previous laser-based techniques used small wavelength tuning ranges to measure only a few isolated spectral lines of a few species, the swept-ECQCL provides the large tuning range needed to measure multiple species simultaneously, and to detect broad absorption features from large molecules or condensed phase materials. In addition, the swept-ECQCL systems have high enough spectral resolution and sensitivity to measure narrow lines of small molecules and determine isotope ratios. The remote detection system for gas plumes is based on the swept-ECQCL technology, and consists of a swept-ECQCL source, infrared detector, control electronics, and beam transmitting and alignment optics. The remote detection system directs the infrared output of the swept-ECQCL to a target retro reflector typically located at ~10-10,000 m distance. The swept-ECQCL wavelength is varied continuously over a large wavelength range (>1000 nm) at rates up to 1000 Hz. The swept ECQCL light reflected from the remote target is collected and focused onto an infrared photodetector. By measuring the detector signal continuously as the swept-ECQCL wavelength is varied, a time-series of absorption spectra are measured for the gases along the beam line of-sight. Based on analysis and fitting of the measured absorption spectra, the time-dependent chemical concentrations of species are determined. Multiple species and mixtures can be detected simultaneously, for all species with absorption features above the sensor noise floor. The sensor output is thus a continuous, high-speed record of identified chemicals along with their concentrations and isotope ratios of interest. The high-speed operation enables low-noise operation in conditions of atmospheric turbulence and allows tracking of fluctuating concentrations in transient chemical plumes as needed for reliable remote detection applications. All components operate with minimal cooling requirements and no cryogens are needed. In addition, the output infrared light is invisible with an intensity below the maximum permissible exposure (MPE) threshold of 100 mW/cm2 for these infrared wavelengths and thus eye safe. The measurement concept for plume detection using the swept-ECQCL remote detection system is as follows. The ECQCL beam is directed toward a remote retro-reflector, which reflects the beam back to the ECQCL system where it is focused onto an infrared photodetector. The line-of-sight from the ECQCL system to the retro-reflector defines the measurement path. The detected infrared signal is recorded continuously and detects the absorption of molecular species along the measurement path. Before a plume release, the system measures absorption from atmospheric constituents, which in this LWIR band consist primarily of lines from H 2 O and CO 2 , with additional weaker absorption from N 2 O, NH 3 , and O 3 possibly contributing. The system then measures any changes in absorption due to the tracer compounds when they enter the measurement path. The shape of absorption features is used to distinguish and identify the different tracer compounds, and the strength of the absorption is used to determine the path-integrated concentration – also called the column density.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1993

Infrared Cirrus and Discrete Sources in the Outer Galaxy

Studies of Galactic infrared cirrus have been based on observations of individual high latitude clouds, analysis of large scale emission at high latitudes in the Solar Neighborhood and complete linear decomposition of the global emission from IRAS and other observations over the entire Galaxy.

IRAS infrared cirrus linear decomposition Point So↗
NASA NTRS2011

The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological parameters that affect the small-scale CMB power. The ACT data combined with WMAP give a 6 sigma detection of primordial helium, with Y(sub p) = 0.313 +/- 0.044, and a 4 sigma detection of relativistic species, assumed to be neutrinos, with N(sub eff) = 5.3 +/- 1.3 (4.6 +/- 0.8 with BAO+H(sub 0) data). From the CMB alone the running of the spectral index is constrained to be d(sub s) / d ln k = -0,034 +/- 0,018, the limit on the tensor-to-scalar ratio is r < 0,25 (95% CL), and the possible contribution of Nambu cosmic strings to the power spectrum is constrained to string tension G(sub mu) < 1.6 x 10(exp -7) (95% CL),

Dunkley, J.↗
NASA NTRS1979

New multiple systems in molecular clouds

Twenty-micron searches of the dense cores of the molecular clouds S140, S255, and Cepheus A have revealed the existence of multiple sources of infrared radiation which seem to be precursors to Trapezium-like clusters of OB stars. Two of the new sources are extended with unusually low color temperatures, less than 100 K. Observations with the Very Large Array with 1 mJy sensitivity have shown that three and possibly four of the infrared sources are associated with small H II regions. Multiple systems appear to be the rule rather than the exception in molecular clouds.

Beichman, C. A.↗
NASA NTRS1980

Infrared observations of the galactic nucleus

Infrared observations of the galactic nucleus and conclusions regarding the nature of the objects present there are reviewed. Observations of three sources of infrared radiation are discussed: near-infrared emission from cool stars, mid- and far-infrared emission from dust, and line emission from ionized gas. These observations provide information about the mass distribution, the stellar population, and the origin and ionization of the compact mid-infrared sources. The possibility of the existence of a massive central black hole is discussed.

Lacy, J. H.↗
NASA NTRS1986

Generating Tunable Far-Infrared Laser Sidebands

New tunable source extends infrared spectroscopy into far infrared wavelengths. Frequency-Tunable far-infrared radiation produced by mixing of fixed-frequency far-infrared laser beam with output of frequency-tunable klystron. By sweeping klystron frequency in synchronism with video display of detector output, one obtains direct presentation of absorption-cell spectrum. Immediate applications are local oscillator for heterodyne systems and tunable source for spectroscopy.

Pickett, H. M.↗
NASA NTRS1980

Source detection for the infrared astronomical satellite

A recursive algorithm is described which detects and characterizes point sources and extended sources in the data obtained from the Infrared Astronomical Satellite (IRAS) in the presence of non-stationary noise. The analysis of tests using simulated data indicates that the performance of the point source detector is very close to that expected from a matched filter with stationary gaussian noise. The false alarm rate of the extended source detector tends to be higher than expected at a given SNR.

Aumann, H. H.↗
NASA NTRS1986

Near-infrared observations of IRAS sources in and near dense cores

We report 0.4 to 20 micron photometry of 27 Infrared Astronomy Satellite (IRAS) point sources associated with dense cores in nearby dark clouds. It is found that these objects have a bimodal distribution of spectral slopes. The objects in the group with steep spectral slopes are typically within one half power radius of the core peak and are not visible on the POSS. The remainder of the objects are typically further from their cores, are optically visible and have shallow spectral slopes (s is approximately 0.6). Most of the sources in this group which have been previously identified are T Tauri stars. Both the groups of objects have essentially the same luminosity function with median luminosity of 1 to 2 L(solar), which is similiar to the luminosity function for T Tauri stars. The near-infrared (J,H,K,L) colors of the objects have been used to estimate the visual extinction to the stars. This indicates that the typical steep spectrum source has extinction A(upsilon) of approximately 30 magnitudes, which is larger by a factor of 3 to 4 than a uniform core can provide, thus the density must rise steeply in the vicinity of the star. For those objects where optical estimates of the extinction are available the optical estimates are typically smaller than our IR estimates by a factor of 1.6. For multiple scattering by grains that scatter primarily in the forward direction, this implies a grain albedo of 0.4 at V, consistent with theoretical predictions for bare grains. Using this derived extinction, the FIR emission from a spherical shell with an inverse power law density which contributes the correct amount of extinction has been modelled. It is shown that to be consistent with both the observations of the density of the core at a scale of 1.5 x 10(17) cm and the extinction derived from the near-IR colors there must be a circumstellar hole of radius 10-100 A.U. for all density laws with exponents greater than 1.2. It is also shown that a component in addition to the star and circumstellar shell is necessary to match the observed spectrum of steep spectrum sources.

Fuller, G. A.↗
NASA NTRS1995

[No Title]

The Two Micron All-Sky Survey will result in a database of millions of newly-discovered near-infrared bright sources of all types, from stars to nebulae to distant galaxies. The full potential of thesurvey will be greatly expanded by providing optical (blue and/or visual) identifications to thesesources from existing databases of optical objects from digitized Schmidt plate archives. I willdescribe the procedures developed at IPAC to identify infrared sources in the IRAS Faint SourceSurvey using such optical archives, and how these will be applied to the 2MASS survey. I willsummarize some of the expected results and in particular will discuss a search for distant near-infrared luminous Active Galactic Nuclei in the 2MASS database.

2MASS Survey↗
NASA NTRS1973

The moon as a proposed radiometric standard for microwave and infrared observations of extended sources.

Measured values of the average midnight and morning terminator infrared brightness temperatures of the central portion of the lunar disk can quite accurately determine the mean surface temperature despite likely horizontal and vertical inhomogeneities of the thermal properties of the lunar soil. These data together with laboratory measurements on lunar soil and in situ temperature measurements in and on the lunar surface lead to a mean surface temperature of 220.5 K plus or minus 2.5 per cent and a mean temperature 35 K hotter at a depth of 1 m. The monthly average brightness temperature is then estimated as a function of wavelength between 10 microns and 100 cm taking into account likely temperature dependencies of the thermal conductivity and loss tangent, and the variation of emissivity with wavelength.

Linsky, J. L.↗
NASA NTRS1982

Gaseous infrared absorption in the lower atmosphere of Venus

Possibly important sources of infrared opacity in the Venusian atmosphere was identified. It is shown that which is the major atmospheric constituent comprising about 97 percent of the atmosphere, is the dominant infrared opacity source. Not shown is N2 which comprises about 3 percent of the atmosphere. The mixing ratio of water vapor varies considerably with altitude but falls in the range of about 20 to 200 parts per million (ppm). The mixing ratio of SO2 falls in the range of 100-200 ppm. This number is about 5000 times larger than estimates obtained earlier via Earth-based observations. The abundance of some of the other minor constituents is also shown.

Chackerian, C., Jr.↗
NASA NTRS1989

Stratospheric Observatory for Infrared Astronomy (SOFIA) system concept

The system concept for the Stratospheric Observatory for Infrared Astronomy (SOFIA), as developed by NASA Ames Research Center is described. The SOFIA facility is a 3-meter class optical/infrared/submillimeter telescope mounted in an open cavity in the forebody of a Boeing 747 aircraft, to be operational in 1992. It represents the next generation of Ames' existing airborne IR facilities, and is about ten times more sensitive than the Kuiper Airborne Observatory (KAO) with 3 times better angular resolution, and able to detect all the far-infrared point sources discovered by IRAS (Infrared Astronomical Satellite) survey in 1983. Major requirements and design attributes of the SOFIA telescope are presented, along with a brief description of the Ground Support/Operations System.

Wiltsee, Christopher B.↗
NASA NTRS1984

Infrared cirrus - New components of the extended infrared emission

Extended sources of far-infrared emission superposed on the zodiacal and galactic backgrounds are found at high galactic latitudes and near the ecliptic plane. Clouds of interstellar dust at color temperatures as high as 35 K account for much of this complex structure, but the relationship to H I column density is not simple. Other features of the extended emission show the existence of warm structures within the solar system. Three bands of dust clouds at temperatures of 150-200 K appear within 10 deg on both sides of the ecliptic plane. Their ecliptic latitudes and derived distances suggest that they are associated with the main asteroid belt. A third component of the 100-micron cirrus, poorly correlated with H I, may represent cold material in the outer solar system or a new component of the interstellar medium.

Low, F. J.↗
NASA NTRS1985

The internal reference source (IRS) for diffuse infrared background experiment (DIRBE)

A means is described for providing internal calibration for the detectors for DIRBE, which is the Diffuse Infrared Background Experiment (a part of the Cosmic Background Explorer). The internal reference source (IRS) that is used consists of four thermal graybody sources coupled to an integrating sphere. The relative insensitivity of the DIRBE bolometers and the linear temperature dependence of the Rayleigh-Jeans law made bolometer stimulation over five orders of magnitude difficult, so four different sources were used with emitting areas varying by a factor of 10 to the 8th. A low heat capacity design with the necessary stability appears to be thin nichrome films on a sapphire substrate. Voltage stability to 0.01 percent is required for those near infrared bands that required stimulation on the Wien portion of the blackbody curve.

Silverglate, P.↗
NASA NTRS1995

A search for T Tauri stars in high-latitude molecular clouds. 2: The IRAS Faint Source Survey catalog

We present a catalog of infrared point sources from the IRAS Faint Source Survey at Galactic latitudes the absolute magnitude of b is greater than or equal to 30 deg. The aim of this paper is to provide a list of possible star-forming sites at high Galactic latitudes in order to address the question of whether or not the translucent molecular clouds (which are most easily identified at high latitudes) are capable of star formation. The primary list of sources has 12, 25, 60, and 100 micron fluxes within the range typical of pre-main-sequence or T Tauri stars. A secondary list has the same range of 12, 25, and 60 micron fluxes, but only upper limits at 100 microns. A total of 127 candidates from the first category and 65 candidates from the second category are identified and their positions and infrared spectral characteristics tabulated. Although the colors and fluxes of these sources are typical of T Tauri or pre-main-sequence stars and YSOs, extragalactic sources and planetary nebulae sometimes have similar colors. These lists provide a starting point for optical spectroscopy or other techniques to positively identify these objects. We can determine an upper limit to the star forming efficiency of high-latitude molecular clouds assuming all the candidates in our sample are pre-main sequence stars of one solar mass. The upper limit of a few tenths of 1% is less than the star-forming efficiency of local dark cloud complexes such as the Taurus-Auriga or rho Ophiuchus clouds.

Magnani, Loris↗
NASA NTRS1992

The near-infrared counterpart of a variable galactic plane radio source

A near-infrared counterpart to the highly variable, unresolved galactic plane radio source GT 0116 + 622 is identified. This source is of particular interest, as it has been previously suggested to be the counterpart of the gamma-ray source Cas gamma-l. The present NIR and red images detect a faint, spatially extended (3 arcsec FWHM), very red object coincident with the radio position. There is complex spatial structure which may be due in part to an unrelated superposed foreground object. Observations on multiple nights show no evidence for flux variability, despite the high amplitude variability on a time-scale of days reported for the radio source. The data are consistent with an interpretation of GT 0116 + 622 as an unusually variable, obscured active galaxy at a distance of several hundred megaparsecs, although more exotic, and in particular galactic, interpretations cannot yet be ruled out. If the object is extragalactic, the previously suggested identification with the gamma-ray source would seem unlikely.

Margon, Bruce↗
NASA NTRS1984

Infrared observations of galactic bulge X-ray sources

Nine unidentified galactic bulge X-ray sources, the recently identified X-ray burster MXB 1728-34, and two optically identified sources (Sco X-1 and MXB 1735-44) were observed with the NASA 3 m Infrared Telescope Facility. The data constrain both the presence of diffuse infrared sources near the X-ray positions and the flux of possible infrared counterparts. None of the nine unidentified sources lies within obscured globular clusters, although there is marginal evidence for diffuse infrared emission near 4U 1822-00 and 4U 1916-05. This implies that at most two additional luminous galactic bulge X-ray sources lie within undiscovered, obscured globular clusters. No infrared counterparts were detected for unidentified sources; the limits derived are consistent with all of the sources observed being similar to the low mass X-ray binary Sco X-1.

Hertz, P.↗