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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Aerosol Retrieval from Multiangle Multispectral Photopolarimetric Measurements: Importance of Spectral Range and Angular Resolution

We investigated the importance of spectral range and angular resolution for aerosol retrieval from multiangle photopolarimetric measurements over land. For this purpose, we use an extensive set of simulated measurements for different spectral ranges and angular resolutions and subsets of real measurements of the airborne Research Scanning Polarimeter (RSP) carried out during the PODEX and SEAC4RS campaigns over the continental USA. Aerosol retrievals performed from RSP measurements show good agreement with ground-based AERONET measurements for aerosol optical depth (AOD), single scattering albedo (SSA) and refractive index. Furthermore, we found that inclusion of shortwave infrared bands (1590 and/or 2250 nm) significantly improves the retrieval of AOD, SSA and coarse mode microphysical properties. However, accuracies of the retrieved aerosol properties do not improve significantly when more than five viewing angles are used in the retrieval.

angular resolution↗
NASA NTRS2005

Narrow Angle Wide Spectral Range Radiometer Design FEANICS/REEFS Radiometer Design Report

A critical measurement for the Radiative Enhancement Effects on Flame Spread (REEFS) microgravity combustion experiment is the net radiative flux emitted from the gases and from the solid fuel bed. These quantities are measured using a set of narrow angle, wide spectral range radiometers. The radiometers are required to have an angular field of view of 1.2 degrees and measure over the spectral range of 0.6 to 30 microns, which presents a challenging design effort. This report details the design of this radiometer system including field of view, radiometer response, radiometric calculations, temperature effects, error sources, baffling and amplifiers. This report presents some radiometer specific data but does not present any REEFS experiment data.

Camperchioli, William↗
NASA NTRSDate not supplied

A New Linear Polarizer Design for Application in the Far-Ultraviolet Spectral Range

New mission concepts that are under consideration by NASA (such as the Polstar MIDEX mission concept) call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that may produce extinction ratios higher than have ever been reported before in the FUV spectral range (100-200 nm). This polarizer consists of transmitting linearly polarized light through a series of reflections from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the LiF Brewster’s angle. The performance of this polarizer concept was fabricated and tested with an existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASA-GSFC. Initial testing has shown that in the FUV spectral range, this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm. A polarizer with such a performance has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the design’s compact design allows for a new polarizer capability that would one day be implemented in a future spectropolarimetry space mission. In addition, this polarizer concept could potentially be used to characterize the optical properties of new mirror coatings that will be used in a future Habitable World Observatory (HWO) mission concept as proposed by the 2020 Decadal Survey.2

Far Ultraviolet (FUV), polarimetry, instrumentatio↗
NASA NTRSDate not supplied

Linear Polarizer Design for Application in the Far-Ultraviolet Spectral Range

New mission concepts that are under consideration by NASA (such as the Polstar MIDEX mission concept) call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that may produce extinction ratios higher than have ever been reported before in the FUV spectral range (100-200 nm). This polarizer consists of transmitting linearly polarized light through a series of reflections from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the LiF Brewster’s angle. The performance of this polarizer concept was fabricated and tested with an existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASA-GSFC. Initial testing has shown that in the FUV spectral range, this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm. A polarizer with such a performance has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the design’s compact design allows for a new polarizer capability that would one day be implemented in a future spectropolarimetry space mission. In addition, this polarizer concept could potentially be used to characterize the optical properties of new mirror coatings that will be used in a future Habitable World Observatory (HWO) mission concept as proposed by the 2020 Decadal Survey.2

Far Ultraviolet (FUV), polarimetry, instrumentatio↗
NASA NTRS1979

High-resolution spectra of Jupiter in the 744-980 inverse centimeter spectral range

Spectra of the central 5 in region of Jupiter in the 744 to 980 kayser spectral range are presented at 0.05 and 0.28 kayser resolution. The gases (N-14)H3, (N-15)H3, and PH3 are observed in absorption, and C2H2 and C2H6 observed in emission. A synthetic spectrum which included the opacity from the H2, (N-14)H3, (N-15)H3, and PH3 is compared with observations. It is concluded that: (1) the (N-14)H3 line profiles are best fitted with a NH3 density in the troposphere which is 0.5 times the saturated vapor pressure density and an opaque cloud at the 0.56 bar pressure level, (2) the best fit (N-15)H3/(N-14)H3 ratio is 0.006, (3) the PH3/H2 abundance ratios of NH3 and PH3 must be highly subsaturated above the tropopause or the temperature inversion is cooler than model predictions.

Tokunaga, A. T.↗
NASA NTRS1978

Shock-tube studies of atomic silicon emission in the spectral range 180 to 300 nm

Emission spectroscopy of shock-heated atomic silicon was performed in the spectral range 180 to 300 nm, in an environment simulating the ablation layer expected around a Jovian entry probe with a silica heat shield. From the spectra obtained at temperatures from 6000 to 10,000 K and electron number densities from 1 quadrillion to 100 quadrillion per cu cm, the Lorentzian line-widths were determined. The results showed that silicon lines are broadened significantly by both electrons (Stark broadening) and hydrogen atoms (Van der Waals broadening), and the combined line-widths are much larger than previously assumed. From the data, the Stark and the Van der Waals line-widths were determined for 34 silicon lines. Radiative transport through a typical shock layer was computed using the new line-width data. The computations showed that silicon emission in the hot region is large, but it is mostly absorbed in the colder region adjacent to the wall.

Prakash, S. G.↗
NASA NTRS1975

Investigation of Facsimile Camera-spectrometer Capability in the 1.0 to 2.7 Micron Spectral Range

The capability of the facsimile camera augmented with a filter-spectrometer to provide scientifically valuable information in the 1.0 to 2.7 microns spectral range was investigated for a future planetary lander mission to Mars. A computer model was used to evaluate tradeoffs between signal-to-noise ratio, spatial and spectral resolution, and the number of spectral channels. Spectral absorption features resulting from water and chemical variations found in pyroxenes were used to represent scientific information of interest to biologists and geologists. Expected output data from a filter-spectrometer is illustrated which indicates that important information pertaining to water content and chemical composition can be obtained using six to eight spectral channels with 0.3 degree spatial resolution.

Kelly, W. L., IV↗
NASA NTRS1979

High resolution atmospheric transmission calculations down to 28.7 km in the 200-243-nm spectral range

Decrease in stratospheric ozone absorption and increase in oxygen absorption with decreasing wavelength combine to produce a window of maximum atmospheric transmission near 210 nm. Since solar radiation in this spectral region dissociates molecular oxygen, the deep atmospheric penetration at this wavelength is of particular aeronomical interest. High resolution calculations of the transmittance down to 28.65 km were made for the 200-243-nm spectral range in this window region, in support of a stratospheric balloon flight from Fort Churchill in July 1974. The calculations were made by dividing the atmosphere into layers which were chosen so that each could be assumed homogeneous; optical depths were calculated separately for each of these layers and then summed to obtain the over-all transmittance of the atmosphere. Absorption by molecular oxygen (line and continuum) and by ozone was included, as well as extinction through Rayleigh scattering by air molecules. The calculated transmittances were combined with high altitude (above 100-km) rocket measurements of the sun-center spectrum and center-to-limb variations to give residual high resolution solar spectral flux for several altitudes and solar zenith angles.

Cann, M. W. P.↗
NASA NTRSDate not supplied

Linear Polarizer Design for Application in the Far-Ultraviolet Spectral Range

New mission concepts that are under consideration by NASA call for the design and implementation of Far Ultraviolet (FUV) polarizer technologies that have not been developed yet. A team that includes members from the NASA Goddard Space Flight Center (GSFC), Arizona State University (ASU), and Woodruff Consulting, worked on the design and development of a polarizer design that produce very high extinction ratios in the FUV spectral range (100-200 nm). This polarizer consists of reflecting light through a series of mirrors from a combination of two silicon carbide (SiC) and two lithium fluoride (LiF) crystals positioned at angles of incidence (relative to surface normal) close to the average LiF Brewster’s angle in the FUV. The output is a highly linearly polarized beam. This polarizer concept was fabricated and tested in the existing McPherson 225 Vacuum Ultraviolet (VUV) spectrometer located in the Optics Branch at NASA-GSFC. Initial testing using a MgF2 crystal at the Brewster’s angle as an analyzer has shown that this design can produce state-of-the-art extinction ratios at the Hydrogen Lyman-Alpha (Ly-α) wavelength of 121.6 nm, and that the measured extinction ratio of the two crossed polarizers, ≈114, is mostly limited by the MgF2 analyzer. A polarizer with such a performance at this wavelength has never been reported and it signifies a breakthrough in FUV polarization technology. The levels of effectiveness paired with the polarizer’s compact design allows for a new polarizer capability that would one day be implemented in a future FUV spectropolarimetry space mission.

Far Ultraviolet (FUV)↗
NASA NTRS2012

FISM 2.0: Improved Spectral Range, Resolution, and Accuracy

The Flare Irradiance Spectral Model (FISM) was first released in 2005 to provide accurate estimates of the solar VUV (0.1-190 nm) irradiance to the Space Weather community. This model was based on TIMED SEE as well as UARS and SORCE SOLSTICE measurements, and was the first model to include a 60 second temporal variation to estimate the variations due to solar flares. Along with flares, FISM also estimates the tradition solar cycle and solar rotational variations over months and decades back to 1947. This model has been highly successful in providing driving inputs to study the affect of solar irradiance variations on the Earth's ionosphere and thermosphere, lunar dust charging, as well as the Martian ionosphere. The second version of FISM, FISM2, is currently being updated to be based on the more accurate SDO/EVE data, which will provide much more accurate estimations in the 0.1-105 nm range, as well as extending the 'daily' model variation up to 300 nm based on the SOLSTICE measurements. with the spectral resolution of SDO/EVE along with SOLSTICE and the TIMED and SORCE XPS 'model' products, the entire range from 0.1-300 nm will also be available at 0.1 nm, allowing FISM2 to be improved a similar 0.1nm spectral bins. FISM also will have a TSI component that will estimate the total radiated energy during flares based on the few TSI flares observed to date. Presented here will be initial results of the FISM2 modeling efforts, as well as some challenges that will need to be overcome in order for FISM2 to accurately model the solar variations on time scales of seconds to decades.

Chamberlin, Phillip C.↗
NASA NTRS2002

Complex Refractive Index of Ammonium Nitrate in the 2-20 micron Spectral Range

Using high resolution Fourier Transform Infrared Spectroscopy (FTIR) absorbance/transmittance spectral data for ammonium sulfate (AMS), calcium carbonate (CAC) and ammonium nitrate (AMN), comparisons were made with previously published complex refractive indices data for AMS and CAC to infer experimental parameters to determine the imaginary refractive index for AMN in the infrared wavelength range from 2 to 20 microns. Kramers-Kronig mathematical relations were applied to calculate the real refractive index for the three compositions. Excellent agreement for AMS and CAC with the published values was found, validating the complex refractive indices obtained for AMN. Backscatter calculations using a lognormal size distribution for AMS, AMN, and CAC aerosols were performed to show differences in their backscattered spectra.

Jarzembski, Maurice A.↗
NASA NTRS1971

Simple spectroscope used with solid state image amplifier over wide spectral range

Prism plus image amplifier panel provides visual image of many infrared spectral lines from carbon arc impregnated with metal compound. Different metal compounds generate various desired spectra. Panel also aligns and focuses simple spectroscopes for detecting spectral lines inside and outside visible region.

Brown, R. L., Sr.↗
NASA NTRS2020

Spectral Range Within Global aCDOM(440) Algorithms for Oceanic, Coastal, and Inland Waters with Application to Airborne Measurements

The optically active component of dissolved organic material in aquatic ecosystems, or colored dissolved organic matter (CDOM), is represented by the coefficient of absorption due to the dissolved aquatic constituents at 440 nm, aCDOM(440). Remote sensing of aCDOM(440) enables characterization of ecosystem processes and aids in retrieval of chlorophyll a, a proxy for phytoplankton biomass. Spectrally adjacent band-ratio domains, e.g., blue to green, have previously been applied for remote sensing of aCDOM(440) in coastal and oceanic waters with similar results compared to more complex semi-analytical algorithms. Estimation of aCDOM(440) from ratios of the most spectrally separated ocean color wavebands (end members), e.g., ultraviolet (UV) to near-infrared (NIR), termed end-member analysis (EMA), has previously been shown to increase the accuracy of global aCDOM(440) retrievals from in-water observations of diffuse attenuation and to enable a unified algorithmic perspective without requiring regional adjustment of internal bio-optical parameters. EMA of above-water observations is evaluated herein, with a focus on coastal and inland waters in which increasing optical complexity and likelihood of bottom reflectance challenge the oceanic algorithms developed for deep and optically simple (case-1) waters. Analysis herein of three independent, in situ, bio-optical datasets indicates significant correlation between aCDOM(440) and end-member band ratios (next-generation 320 and 780 nm or legacy 412 and 670 nm ratios) with a coefficient of determination, R2, of 0.87 (log-scale) or higher based on a dataset spanning the dynamic range of global, conservative water bodies. For applicable wavelengths, EMA algorithms are shown to agree with case-1 relationships and to produce consistent log-scale uncertainties across more than three orders of magnitude in aCDOM(440) values (0.001–2.305 m􀀀1). EMA using UV and NIR wavelengths (320 and 780 nm) is applied to low-altitude airborne observations and satisfies 25% uncertainty based on unbiased percent differences (UPDs) within each of three dissimilar match-up sites ranging in aCDOM(440) from 0.02–0.57 m􀀀1. Results demonstrate that EMA is a useful and robust approach for the remote sensing of aCDOM(440) in coastal and inland waters, which are generally shallower, contain more optically complex environments, and span a greater range in aCDOM(440) than oceanic waters.

CDOM↗
NASA NTRS1995

Ground-based observations of the corona in the visible and NIR spectral ranges

Since late 1993 we have been using a mirror coronagraph on Pic du Midi (PICO) to observe the solar emission corona in several spectral lines of (FE-X), (FE-XIII), and (FE-XIV). For good meteorological conditions the diffuse corona and coronal holes in between can be seen out to 1.2 solar mass for sun center. Active regions can be mapped to bond 1.5 solar mass in the green and infrared lines. Recent observations of PICO are presented.

Epple, Alexander↗