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NASA NTRS1992

The moon - Mid-infrared (7.5- to 11.4-microns) spectroscopy of selected regions

Scaled spectral emissivity spectra have been obtained from five locations on the illuminated lunar surface and are interpreted in terms of differences in their mineralogic composition. The emission maximum, which typically falls near 8.0 microns for lunar rocks and fines, is observed to be shifted from 7.9 microns for noritic Copernicus crater walls to 8.1 microns for the olivine-rich central peak. Two mare locations show the emission maximum centered at 8.0 microns, consistent with laboratory emission measurements of basalts. An emissivity minimum at 10.5 microns in the spectrum from central peak 2 is attributed to the presence of olivine. Minima centered at 8.75 microns in the crater wall spectra resemble minima in laboratory spectra from pyroxene. A broad minimum centered at 8.5 microns in the Kepler ejecta spectrum and a sharp drop in emissivity at wavelengths longer than 11 microns in spectra from both mare locations suggest plagioclase.

Sprague, A. L.↗

NASA NTRS1993

Liquidus temperatures in the Ti-Al system

Liquidus temperatures were determined for the titanium-aluminum system at compositions ranging from 41 to 62 at. pct Al. The measurements were obtained by inducing solidification of slightly undercooled melts under containerless processing conditions using electromagnetic levitation. Absolute temperatures were determined by optical pyrometry in combination with independent measurements of spectral emissivities by laser polarimetry. The present liquidus temperatures are in agreement with two sets of literature values and are consistent with a set of solid-state literature data. These values exceed those selected in one recent proposed phase diagram revision by about 30 K and are as much as 40 to 60 K higher than those in another proposed revision.

Anderson, C. D.↗

NASA NTRS1993

The cryogenic limb array etalon spectrometer (CLAES) on UARS - Experiment description and performance

The design and the performance of the cryogenic limb array spectrometer (CLAES) aboard the NASA Upper Atmosphere Research Satellite are discussed. CLAES measures altitude profiles of temperature, pressure, O3, H2O, CH4, N2O, NO, NO2, N2O5, HNO3, ClONO2, HCl, CFC 11, CFC 12, and aerosol absorption coefficients for atmospheric layer between 10 and 60 km. Examples of atmospheric spectral emission profiles for a number of constituents are presented as well as responsivity and noise parameters.

Roche, A. E.↗

NASA NTRS1993

Near- and mid-infrared imaging of the planetary nebulae BD +30 deg 3639 and IC 418

We present near- and mid-IR images of the planetary nebulae BD +30 deg 3639 and IC 418, with a unique combination of high spatial and spectral resolution. The mid-IR images were obtained with MIRAC, a new IR array camera. For BD +30 deg 3639, the mid-IR images at 10.0, 11.2, 12.4, 12.8, and 13.2 microns have allowed us to separate the various spectral emission components such as the broad UIR features, the 12.8-micron forbidden Ne II emission feature, and continuum emission, to determine the distribution of these components in the nebula. For IC 418, we have obtained high-resolution images in both the near- and mid-IR. The images in the near-IR at J, H, and K are important for determining the source of the IR excess; one component of the excess is located near the central star. We have also imaged the halo emission at H and K, which has been detected in earlier studies, and have determined its spatial extent. The mid-IR images at 9.8 and 11.7 microns show continuum emission coincident with the ionized zone and suggest that SiC emission originates from the region near the central star.

Hora, Joseph L.↗

NASA NTRS1993

Dynamic measurements of thermophysical properties of metals and alloys at high temperatures by subsecond pulse heating techniques

Rapid (subsecond) heating techniques developed at the National Institute of Standards and Technology for the measurements of selected thermophysical and related properties of metals and alloys at high temperatures (above 1000 C) are described. The techniques are based on rapid resistive self-heating of the specimen from room temperature to the desired high temperature in short times and measuring the relevant experimental quantities, such as electrical current through the specimen, voltage across the specimen, specimen temperature, length, etc., with appropriate time resolution. The first technique, referred to as the millisecond-resolution technique, is for measurements on solid metals and alloys in the temperature range 1000 C to the melting temperature of the specimen. It utilizes a heavy battery bank for the energy source, and the total heating time of the specimen is typically in the range of 100-1000 ms. Data are recorded digitally every 0.5 ms with a full-scale resolution of about one part in 8000. The properties that can be measured with this system are as follows: specific heat, enthalpy, thermal expansion, electrical resistivity, normal spectral emissivity, hemispherical total emissivity, temperature and energy of solid-solid phase transformations, and melting temperature (solidus). The second technique, referred to as the microsecond-resolution technique, is for measurements on liquid metals and alloys in the temperature range 1200 to 6000 C. It utilizes a capacitor bank for the energy source, and the total heating time of the specimen is typically in the range 50-500 micro-s. Data are recorded digitally every 0.5 micro-s with a full-scale resolution of about one part in 4000. The properties that can be measured with this system are: melting temperature (solidus and liquidus), heat of fusion, specific heat, enthalpy, and electrical resistivity. The third technique is for measurements of the surface tension of liquid metals and alloys at their melting temperature. It utilizes a modified millisecond-resolution heating system designed for use in a microgravity environment.

Cezairliyan, Ared↗

NASA NTRS1994

High power diode lasers for solid-state laser pumps

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

Linden, Kurt J.↗

NASA NTRS1992

Full-spectrum multiwavelength pyrometry for nongray surfaces

A full-spectrum (encompassing radiation on both sides of the Wien displacement peak) multiwavelength pyrometer was developed. It measures the surface temperature of arbitrary nongray ceramics by curve fitting a spectrum in this spectral region to a Planck function of temperature T. This function of T is modified by the surface spectral emissivity. The emissivity function was derived experimentally from additional spectra that were obtained by using an auxiliary radiation source and from application of Kirchhoff's law. This emissivity was verified by results that were obtained independently by using electromagnetic and solid-state theories. In the presence of interfering reflected radiation this general pyrometry improves the accuracy of the measured temperature by measuring an additional spectrum that characterizes the interfering radiation source.

Ng, Daniel↗

NASA NTRS1994

A laser-based sizing/velocimetry technique to investigate the secondary atomization of aluminum gel propellants

A laser-based, forward-scatter diagnostic technique, employing a single laser sheet, has been developed to simultaneously measure the size and velocity of individual 10-150 micron droplets in a dilute polydisperse droplet stream (less than 1000 particles/cc) and to detect the presence of burning aluminum in these same droplets. Spectral emission from aluminum vapor in the 390-400 nm wavelength region is used as an indication of burning aluminum. The technique utilizes a 4-mm uniformly illuminated probe volume, eliminating trajectory-dependent particle sizing and size-dependent system detection bias. Particle sizing is based on a correlation of particle size with near-forward scattered light intensity. Calculations show average particle sizing variation to be within 3.5% over the expected range of refractive indices. Calibrations using a range of optical pinholes (10-100 micron) were used to verify the above sizing correlation.

Mueller, D. C.↗

NASA NTRS1995

Confirmation of interstellar methylene

Four spectral emission features of the N(sub KK) = 4(sub 04) -3(sub 13) rotational transition of methylene (CH2) have been detected at signal levels 5-7 sigma above noise toward the hot core of the Orion-KL nebula and the molecular cloud in proximity to the continuum source W51 M. Specifically, in both sources we have resolved the F = 6-5, 5-4, and 4-3 hyperfine transitions of the J = 5-4 fine-structure levels and detected the blended hyperfine structure of the J = 4-3 fine structure levels. At the J = 3-2 fine-structure levels, we have observed new transitions of NS, a known interstellar molecule, which severely contaminates the search for CH2 hyperfine transitions. These new sensitive observations finally confirm the existence of interstellar CH2 which was tentatively reported by us some years ago.

Hollis, J. M.↗

NASA NTRS1994

Detection of a flaring low-energy gamma-ray source

We report the detection of a flaring gamma-ray source by the University of New Hampshire (UNH) balloon-borne coded aperture gamma-ray telescope (DGT) on 1984 October 2. The source was detected at the significance level of 7.2 sigma over the energy range 160-2000 keV. The intensity in the range (160-200) keV was 1.1 Crab. The best-fit position of the source is given by R.A. = 3h 25.8m and Decl. = 67 deg 653 min and is located in the constellation of Camelopardia. The source was visible within the Field of View (FOV) of the telescope for approximately = 2 hr and exhibited signs of flaring. The derived photon spectrum can be equally fitted by an optically thin bremsstrahlung distribution of kT approximately = 52 keV or a power law of the form, dN(E)/dE = 3.7 x 10(exp -6) (E/400)(exp -4.5) photons/sq cm/keV. We compare its spectral characteristics ad energy output to various types of fast X-ray transients. No measurable flux could be detected from CG 135+1, the COS B source which was in the FOV and therefore, we present 2 sigma upper flux limits on its spectral emission over the energy range 160 keV to 9.3 MeV.

Bhattacharya, Dipen↗

NASA NTRS1993

Effects of a parallel electric field and the geomagnetic field in the topside ionosphere on auroral and photoelectron energy distributions

The consequences of electric field acceleration and an inhomogeneous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one-dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogeneous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of O(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function is investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogeneous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Min, Q.-L.↗

NASA NTRS1993

Land surface temperature measurements from EOS MODIS data

The task objectives of this reporting phase included: (1) completing the draft of the LST Algorithms Theoretical Basic Document by July 30, 1993; (2) making a detailed characterization of the thermal infrared measurement system including spectrometer, blackbody, and radiation sources; (3) making TIR spectral measurements of water and snow-cover surfaces with the MIDAC M2401 spectrometer; and (4) making conceptual and engineering design of an accessory system for spectrometric measurements at variable angles. These objectives are based on the requirements by the MODIS Science Team and the unique challenge in the development of MODIS LST algorithms: to acquire accurate spectral emissivity data of land covers in the near-term and to make ground validations of the LST product in the long-term with a TIR measurement system.

Wan, Zhengming↗

NASA NTRS1993

Effects of a Parallel Electric Field and the Geomagnetic Field in the Topside Ionosphere on Auroral and Photoelectron Energy Distributions

The consequences of electric field acceleration and an inhomogencous magnetic field on auroral electron energy distributions in the topside ionosphere are investigated. The one- dimensional, steady state electron transport equation includes elastic and inelastic collisions, an inhomogencous magnetic field, and a field-aligned electric field. The case of a self-consistent polarization electric field is considered first. The self-consistent field is derived by solving the continuity equation for all ions of importance, including diffusion of 0(+) and H(+), and the electron and ion energy equations to derive the electron and ion temperatures. The system of coupled electron transport, continuity, and energy equations is solved numerically. Recognizing observations of parallel electric fields of larger magnitude than the baseline case of the polarization field, the effect of two model fields on the electron distribution function in investigated. In one case the field is increased from the polarization field magnitude at 300 km to a maximum at the upper boundary of 800 km, and in another case a uniform field is added to the polarization field. Substantial perturbations of the low energy portion of the electron flux are produced: an upward directed electric field accelerates the downward directed flux of low-energy secondary electrons and decelerates the upward directed component. Above about 400 km the inhomogencous magnetic field produces anisotropies in the angular distribution of the electron flux. The effects of the perturbed energy distributions on auroral spectral emission features are noted.

Min, Q.-L.↗

NASA NTRS1996

Validation of UARS Microwave Limb Sounder ClO Measurements

Validation of stratospheric ClO measurements by the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS) is described. Credibility of the measurements is established by (1) the consistency of the measured ClO spectral emission line with the retrieved ClO profiles and (2) comparisons of ClO from MLS with that from correlative measurements by balloon-based, ground-based, and aircraft-based instruments. Values of "noise" (random), "scaling" (multiplicative), and "bias" (additive) uncertainties are determined for the Version 3 data, in the first version public release of the known artifacts in these data are identified. Comparisons with correlative measurements indicate agreement to within the combined uncertainties expected for MLS and the other measurements being compared. It is concluded that MLS Version 3 ClO data, with proper consideration of the uncertainties and "quality" parameters produced with these data, can be used for scientific analyses at retrieval surfaces between 46 and 1 hPa (approximately 20-50 km in height). Future work is planned to correct known problems in the data and improve their quality.

Waters, J. W.↗

NASA NTRS1999

Solid Phase Luminescence of Several Rare Earth Ions on Ion-Exchange Films

The development and characterization of a novel ion-exchange film for solid-phase fluorometry and phosphorimetry is reported. This new cation-exchange material is suitable for spectroscopic applications in the ultraviolet and visible regions. It is advantageous because it, as a single entity, is easily recovered from solution and mounted in the spectrofluorometers. After preconcentration on the film, the luminescence intensity of lanthanide ions is several orders of magnitude greater than that of the corresponding solution, depending on the volume of solution and the amount of film. This procedure allows emission spectral measurements and determination of lanthanide ions at solution concentrations of < 5 (micro)g/L. The film may be stored for subsequent reuse or as a permanent record of the analysis. The major drawback to the use of the film is slow uptake of analyte due to diffusion limitations.

Tanner, Stephen P.↗

NASA NTRS2000

Determination of Surface and Atmospheric Parameters from AIRS/AMSU/HSB Data

AIRS (Atmospheric Infra Red Sounder) is the first of a series of next generation high spectral resolution infrared sounders which will fly on satellite missions in the next decade. AIRS is a 2368 channel grating spectrometer, with spectral resolving power of roughly upsilon / DELTA upsilon) = 1200, which will fly on the Earth Observing System (EOS) Aqua platform in December 2000 accompanied by Advanced Micowave Sounding Unit (AMSU) A and High Spatial Bandwidth (HSB), which is similar to AMSU B. New methodology has been developed by the AIRS Science Team to analyze AIRS/AMSU/HSB data in the presence of multilayer broken clouds. The baseline AIRS/AMSU products include surface skin temperature, surface spectral emissivity, atmospheric temperature-moisture-ozone profiles and cloud heights and amounts. Research products include CO and CH4 profiles, total CO2 burden, and OLR. This methodology will be briefly described and results will be shown of AIRS Science Team simulations, based on one day of simulated global data. RMS errors of atmospheric temperature profiles are expected to be better than 1 K for 1 km layer mean temperatures in up to 80% multilayer fractional cloud cover and RMS errors for moisture profiles are better than 15% for 2 km layers throughout the troposphere.

Susskind, J.↗

NASA NTRS2000

Determination of Surface and Atmospheric Parameters from AIRS/AMSU/HSB Data

AIRS (Atmospheric Infra Red Sounder) is the first of a series of next generation high spectral resolution infrared sounders which will fly on satellite missions in the next decade. AIRS is a 2368 channel grating spectrometer, with spectral resolving power of roughly upsilon /Delta(upsilon) = 1200, which will fly on the EOS Aqua platform in December 2000 accompanied by AMSU A and HSB, which is similar to AMSU B. New methodology has been developed by the AIRS Science Team to analyze AIRS/AMSU/HSB data in the presence of multilayer broken clouds. The baseline AIRS/AMSU products include surface skin temperature, surface spectral emissivity, atmospheric temperature-moisture-ozone profiles and cloud heights and amounts. Research products include CO and CH4 profiles, total CO2 burden, and OLR. This methodology will be briefly described and results will be shown of AIRS Science Team simulations, based on one day of simulated global data.. RMS errors of atmospheric temperature profiles are expected to be better than 1 K for 1 km layer mean temperatures in up to 80% multilayer fractional cloud cover and RMS errors for moisture profiles are better than 15% for 2 km layers throughout the troposphere.

Susskind, Joel↗

NASA NTRS2000

Optical Measurement and Visualization in High-Pressure, High-Temperature, Aviation Gas Turbine Combustors

Planar laser-induced fluorescence (PLIF), planar Mie scattering (PMie), and linear (1-D) spontaneous Raman scattering are applied to flame tube and sector combustors that burn Jet-A fuel at a range of inlet temperatures and pressures that simulate conditions expected in future high-performance civilian gas turbine engines. Chemiluminescence arising from C2 in the flame was also imaged. Flame spectral emissions measurements were obtained using a scanning spectrometer. Several different advanced concept fuel injectors were examined. First-ever PLIF and chemiluminescence data are presented from the 60-atm Gas turbine combustor facility.

Hicks, Yolanda R.↗