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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Magnetization of the oceanic crust - Thermoremanent magnetization of chemical remanent magnetization?

A model was proposed in which chemical remanent magnetization (CRM) acquired within the first 20 Ma of crustal evolution may account for 80 percent of the bulk natural remanent magnetization (NRM) of older basalts. The CRM of the crust is acquired as the original thermoremanent magnetization (TRM) is lost through low temperature alteration. The CRM intensity and direction are controlled by the post-emplacement polarity history. This model explains several independent observations concerning the magnetization of the oceanic crust. The model accounts for amplitude and skewness dicrepancies observed in both the intermediate wavelength satellite field and the short wavelength sea surface magnetic anomaly pattern. It also explains the decay of magnetization away from the spreading axis, and the enhanced magnetization of the Cretaceous Quiet Zones while predicting other systematic variations with age in the bulk magnetization of the oceanic crust. The model also explains discrepancies in the anomaly skewness parameter observed for anomalies of Cretaceous age. Further studies indicate varying rates of TRM decay in very young crust which depicts the advance of low temperature alteration through the magnetized layer.

Raymond, C. A.↗
NASA NTRS1988

Annealing results on low-energy proton-irradiated GaAs solar cells

AlGaAs/GaAs solar cells with an approximately 0.5-micron-thick Al(0.85)Ga(0.15)As window layer were irradiated using normal and isotropic incident protons having energies between 50 and 500 keV with fluence up to 1 x 10 to the 12th protons/sq cm. The irradiated cells were annealed at temperatures between 150 and 300 C in nitrogen ambient. The annealing results reveal that significant recovery in spectral response at longer wavelengths occurred. However, the short-wavelength spectral response showed negligible annealing, irrespective of the irradiation energy and annealing conditions. This indicates that the damage produced near the AlGaAs/GaAs interface and the space-charge region anneals differently than damage produced in the bulk. This is explained by using a model in which the as-grown dislocations interact with irradiation-induced point defects to produce thermally stable defects.

Kachare, R.↗
NASA NTRS1991

Stress analysis of Tellus Regio, Venus, based on gravity and topography - Comparison with Venera 15/16 radar images

The tectonics of the Tellus Region highland on Venus is examined using the altimetry and gravity data collected by Pioneer Venus, which were incorporated into a thin elastic shell model to calculate both the global (long-wavelength) and the regional (short-wavelength) stresses for various assumed values of crust, lithosphere, and mantle thickness and modes of compensation. The resultant stress fields were compared to the surface morphology observed in the Venera 15/16 radar images and interpreted in terms of stress history of Tellus Regio. The best fitting parameters were found to be consistent with minor amounts of lithospheric flexure being necessary to produce the observed surface features of this region.

Williams, David R.↗
NASA NTRS1993

International Ultraviolet Explorer observations of the white dwarf nucleus of the very old, diffuse planetary nebula, IW-2

UV low-dispersion spectra of the central star of the faint planetary nebula, IW-2, were obtained with the IUE. The apparent large diameter of the very diffuse nebula, about half that of the moon, as seen on the Palomar Sky Survey plates by Ishida and Weinberger (1987), indicates this object to be potentially quite evolved, and nearby. The IUE spectra clearly reveal a hot stellar continuum extending over the entire wavelength range of the short-wavelength prime camera (1200-2000 A). This object with V = 17.7 +/- 0.4 is definitely one of the faintest stars ever successfully observed with the IUE. Comparisons of the IUE observed fluxes with those from white dwarf model atmospheres suggest extinction near E(B - V) = 0.45 for a white dwarf of T(eff) roughly 100,000 K. Constraints from estimates of the nebular emission measure and observed visual magnitude also argue for a white dwarf of T(eff) roughly 100,000 K at a distance of 300 to 350 pc. The nucleus of IW-2 is one of the most evolved stars to be identified with a planetary nebula.

Bruhweiler, F. C.↗
NASA NTRS1990

Diode laser array

A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.

Carlson, Nils W.↗
NASA NTRS1978

Calibration of longwavelength exotech model 20-C spectroradiometer

A brief description of the Exotech model 20-C field spectroradiometer which measures the spectral radiance of a target in the wavelength ranges 0.37 to 2.5 microns (short wavelength unit), 2.8 to 5.6 microns and 7.0 to 14 microns (long wavelength unit) is given. Wavelength calibration of long wavelength unit was done by knowing the strong, sharp and accurately known absorption bands of polystyrene, atmospheric carbon dioxide and methyl cyclohexane (liquid) in the infrared wavelength region. The spectral radiance calibration was done by recording spectral scans of the hot and the cold blackbodies and assuming that spectral radiance varies linearly with the signal.

Kumar, R.↗
NASA NTRS1982

Pre-eclipse ultraviolet spectra of Epsilon Aurigae

Existing high dispersion, long wavelength IUE, high dispersion long and short wavelength, and Balloon borne ultraviolet stellar spectrograph (BUSS) spectra providing a baseline measurement of the ultraviolet spectrum of the Epsilon Aurigae system before eclipse are reviewed. Plans for ultraviolet spectrum IUE observations during the 1982 to 1984 eclipse of Epsilon Aurigae are presented.

Chapman, R. D.↗
NASA NTRS1991

Boundary-layer receptivity of sound with roughness

An experimental study of receptivity was carried out using an acoustical disturbance in the freestream. The receptivity was enhanced by using a uniform two-dimensional roughness strip (tape). The roughness strip generated the local adjustment in the flow needed to couple the long-wavelength sound wave with the short-wavelength T-S wave. The method proved to be highly sensitive, with slight changes in the forcing frequency or in the height of the 2D roughness element having a strong effect on the amplitude of the observed T-S wave.

Saric, William S.↗
DOE OSTI2021

Broadband Liquid Crystal Tunable Metasurfaces in the Visible: Liquid Crystal Inhomogeneities Across the Metasurface Parameter Space

Optical metasurfaces—planar nanostructured devices that can arbitrarily tailor the wavefront of light—may be reconfigured by changing their dielectric environment. The application of external stimuli to liquid crystals is a particularly promising means of tuning the optical properties of embedded metasurfaces because of liquid crystals' large and broadband optical anisotropy. However, the detailed behavior of liquid crystals immediately adjacent to the nanostructured meta-atoms elements is often overlooked, despite the optics of the device depending sensitively on this behavior (e.g., the spectral position of the meta-atom resonances). This is of increasing concern as the wavelength of operation further approaches the short-wavelength end of the visible spectrum and, therefore, the length scale of the inhomogeneities in the liquid crystal director field. In this manuscript, we undertake a fully comprehensive study, across the metasurface geometrical parameter space, of broadband (450-700 nm) all-dielectric liquid crystal tunable metasurfaces operating in the visible. Here, through combined experimental characterization, liquid crystal modeling, and optical simulations, we reveal and quantify the improved accuracy with which the optical properties of the liquid crystal tunable metasurfaces may be described, and identify the underlying physical mechanism: the three-dimensional spatial overlap of the liquid crystal director field and metasurface optical near fields in the vicinity of the meta-atoms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Mshock HED Council Request FY24 [Slides]

ICF and HEDP experiments experience complicated loadings including successive shocks, but modeling and analytic work has mostly engaged the simpler shock or shock-reshock case. This is because the co propagating case is difficult to achieve with conventional (non-HED) drivers. Successive shocks will be challenging to model in BHR or modal model interpretations: 1) Ex: Consider the case where long wavelength modes re-invert coherently, but short wavelength nonlinear modes are spun up turbulently. 2) Necessitates more advanced diagnostics and analysis than simple “mixing layers.” High resolution spectral information (concomitant with Ω-EP campaigns) and higher-order moment analyses will be necessary to stress and validate the reduced BHR-type models.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1979

Calibration of long wavelength Exotech model 20C spectroradiometer

A brief description of the Exotech model 20C field spectroradiometer, which measures the spectral radiance of a target in the wavelength ranges from 0.37 to 2.5 microns (short wavelength unit), 2.8 to 5.6 microns, and 7.0 to 14 microns (long wavelength unit) is given. It is a rugged field instrument which uses four circular-variable-filters to get wavelength scan. Wavelength calibration of the long wavelength unit was done by use of the strong, sharp, and accurately known absorption bands of polystyrene, atmospheric carbon dioxide, and methyl cyclohexane (liquid) in the IR wavelength region. The spectral radiance calibration was done by recording spectral scans of the hot and the cold blackbody targets and assuming that spectral radiance varies linearly with the signal.

Kumar, R.↗
NASA NTRS1979

Techniques for interpretation of geoid anomalies

For purposes of geological interpretation, techniques are developed to compute directly the geoid anomaly over models of density within the earth. Ideal bodies such as line segments, vertical sheets, and rectangles are first used to calculate the geoid anomaly. Realistic bodies are modeled with formulas for two-dimensional polygons and three-dimensional polyhedra. By using Fourier transform methods the two-dimensional geoid is seen to be a filtered version of the gravity field, in which the long-wavelength components are magnified and the short-wavelength components diminished.

Chapman, M. E.↗
NASA NTRS1990

Sensor requirements for Earth and planetary observations

Future generations of Earth and planetary remote sensing instruments will require extensive developments of new long-wave and very long-wave infrared detectors. The upcoming NASA Earth Observing System (EOS) will carry a suite of instruments to monitor a wide range of atmospheric and surface parameters with an unprecedented degree of accuracy for a period of 10 to 15 years. These instruments will observe Earth over a wide spectral range extending from the visible to nearly 17 micrometers with a moderate to high spectral and spacial resolution. In addition to expected improvements in communication bandwidth and both ground and on-board computing power, these new sensor systems will need large two-dimensional detector arrays. Such arrays exist for visible wavelengths and, to a lesser extent, for short wavelength infrared systems. The most dramatic need is for new Long Wavelength Infrared (LWIR) and Very Long Wavelength Infrared (VLWIR) detector technologies that are compatible with area array readout devices and can operate in the temperature range supported by long life, low power refrigerators. A scientific need for radiometric and calibration accuracies approaching 1 percent translates into a requirement for detectors with excellent linearity, stability and insensitivity to operating conditions and space radiation. Current examples of the kind of scientific missions these new thermal IR detectors would enhance in the future include instruments for Earth science such as Orbital Volcanological Observations (OVO), Atmospheric Infrared Sounder (AIRS), Moderate Resolution Imaging Spectrometer (MODIS), and Spectroscopy in the Atmosphere using Far Infrared Emission (SAFIRE). Planetary exploration missions such as Cassini also provide examples of instrument concepts that could be enhanced by new IR detector technologies.

Chahine, Moustafa T.↗
NASA NTRS1999

Landsat-7 EMT+ On-Orbit Radiometric Calibration

Landsat-7 was launched on April 15, 1999 and completed its on orbit initialization and verification period on June 28, 1999. The ETM+ payload is similar to the TM sensors on previous Landsat satellites and incorporates two new devices to improve its absolute radiometric calibration. The Full Aperture Solar Calibrator (FASC) is a deployable diffuser panel. This device has been deployed 9 times to date, with a normal deployment schedule of once per month. The initial analysis of the FASC data has given absolute calibration results within 5% of the prelaunch integrating sphere calibrations and a range of variation of 2% between dates. The Partial Aperture Solar Calibrator (PASC), is a set of auxiliary optics that allows the ETM+ to view the sun through a reduced aperture. Data have normally been acquired on a daily basis with the PASC. Initial results with the PASC were encouraging, despite some unexpected saturation in the shortest wavelength band. The response of the ETM+ short wavelength (silicon) bands to the PASC increased initially and has begun to decrease in some of these bands. The longer wavelength (InSb) bands have shown up to 30% oscillations that vary between detectors within the band. Studies are ongoing to better characterize the response to the PASC. The ETM+ also incorporates an internal calibrator (IC), a shutter that oscillates in front of the focal plane that directs light from the internal calibrator lamps to the focal plane. The responses to this device are also varying, though differently than the PASC results. Both the IC and PASC results are attributable to the calibration devices as opposed to the ETM+ itself.

Markham, Brian L.↗
NASA NTRS2000

Ground-Based Measurements of Stratospheric Composition from Mt. Barcroft, California

The MkIV is an FTIR spectrometer designed and built at JPL in the 1980's for remote sensing the composition of the Earth's atmosphere by solar absorption spectrometry. Optically, MkIV is very similar to the JPL ATMOS instrument, which flew three times on the Space Shuttle. Both use double-passed configurations with a KBr beamsplitter and compensator, in order to cover the mid-infrared. The main advantage of the MkIV is that it uses two detectors in parallel, a HgCdTe photoconductor for the long wavelengths and an InSb photodiode for the short wavelengths, allowing the entire 650 to 5650/cm region to be measured simultaneously. At a 10 kHz sampling rate, each 130 cm OPD interferogram takes 3 minutes to acquire. This paper describes how the MkIV instrument was adapted for remote operation from the Barcroft site, where the harsh winter conditions make access difficult. Some of the main technical challenges will be discussed including, (i) operation from solar panels and batteries, (ii) cooling the detectors with LN2, (iii) instrument control and monitoring over a cellular phone, and (iv) data storage, processing and analysis. Finally, MkIV spectra measured from Barcroft are compared with those measured from JPL to highlight the advantages of the higher altitude site.

Toon, G. C.↗
NASA NTRS1994

Simulated ASTER data for Geologic Studies

The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) is a high spatial resolution imaging instrument, due to be launched on NASA's Earth Observing System AM-1 satellite platform in 1998. ASTER acquires data in 14 bands, spanning the wavelength region from the visible, near infrared, short wavelength infrared, and thermal infrared, with spatial resolution varying from 15 m to 90 m, depending on wavelength region. In order to evaluate our ability to use ASTER data for geological mapping, we used aircraft data over Cuprite, Nevada to create a simulated 14-band ASTER data set. The study site has sparse vegetation, and exposes a wide range of unaltered and hydrothermally altered volcanic rocks. The wide range of wavelengths covered by ASTER allowed us to recognize or separate iron oxide minerals, clay-bearing minerals, sulfate minerals, ammonia minerals, siliceous rocks, and carbonates. Combined with laboratory spectral measurements, we were able to identify these constituents. Based on both sets of information, we produced an alteration map showing the distribution of argillized rocks, opalized rocks with alunite, silicified rocks, and areas dominated by kaolinite and buddingtonite. The map was as accurate as published maps made by traditional field methods. ASTER promises to be a major improvement over existing satellite systems for geologic mapping.

Advanced↗
DOE OSTI2025

Broadband THz Modulation via Solid–State Organic Electrochemical Devices

The sub-Terahertz and Terahertz bands play a critical role in next-generation wireless communication and sensing technologies, thanks to the large amount of available bandwidth in this spectral regime. While long-wavelength (microwave to mm-Wave) and short-wavelength (near-infrared to ultraviolet) devices are well-established and studied, the sub-THz to THz regime remains relatively underexplored and underutilized. Traditional approaches used in the aforementioned spectral regions are more difficult to replicate in the THz band, leading to the need for the development of novel devices and structures that can manipulate THz radiation effectively. Herein a novel organic, solid-state electrochemical device is presented, capable of achieving modulation depths of over 90% from ≈500 nm of a conducting polymer that switches conductivity over a large dynamic range upon application of an electronically controllable external bias. The stability of such devices under long-term, repeated voltage switching, as well as continuous biasing at a single voltage, is also explored. Switching stabilities and long-term bias stabilities are achieved over two days for both use cases. Additionally, both depletion mode (always “ON”) and accumulation mode (always “OFF”) operation are demonstrated. These results suggest applications of organic electrochemical THz modulators in large area and flexible implementations.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Bias‐Dependent Quantum Efficiency Reveals Recombination Pathways in Thin Film Solar Cells

Identifying where recombination predominantly occurs—whether at the front interface, back interface, or throughout the bulk—is crucial for optimizing CdSeTe solar cells and many other photovoltaic device architectures. Here, a simple and effective diagnostic is demonstrated: measuring external quantum efficiency (QE) under varying forward biases. The drift–diffusion simulations reveal that each recombination pathway leaves a distinct bias-induced signature in the normalized QE: a progressive drop at long wavelengths for back-limited devices, a short-wavelength decline for front-limited devices, and a relatively uniform decrease across all wavelengths for bulk-limited devices. These predictions are validated with experiments on As-doped and Cu-doped CdSeTe devices, with and without passivation layers or different front buffers. In each case, the observed bias-dependent QE spectral changes align with the simulated recombination map. Because this method uses standard QE instrumentation, it offers a broadly accessible and cost-efficient means to diagnose recombination pathways—extending beyond CdSeTe to other thin-film and emerging solar cell technologies. By pinpointing recombination bottlenecks, researchers and manufacturers can strategically refine doping profiles, passivation schemes, and interface designs to further improve device performance.

CdTe↗