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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Candidate cosmic filament in the GJ526 field, mapped with the NIKA2 camera

Distinctive large-scale structures have been identified in the spatial distribution of optical galaxies up to redshift z ~ 1. In the more distant universe, the relationship between the dust-obscured population of star-forming galaxies observed at millimetre wavelengths and the network of cosmic filaments of dark matter apparent in all cosmological hydrodynamical simulations is still under study. Using the NIKA2 dual-band millimetre camera, we mapped a field of ~90 arcmin 2 in the direction of the star GJ526 simultaneously in its 1.15-mm and 2.0-mm continuum wavebands to investigate the nature of the quasi-alignment of five sources found ten years earlier with the MAMBO camera at 1.2 mm. We find that these sources are not clumps of a circumstellar debris disc around this star as initially hypothesized. Rather, they must be dust-obscured star-forming galaxies, or sub-millimetre galaxies (SMGs), in the distant background. The new NIKA2 map at 1.15 mm reveals a total of seven SMGs distributed in projection on the sky along a filament-like structure crossing the whole observed field. Furthermore, we show that the NIKA2 and supplemental Herschel photometric data are compatible with a model of the spectral energy distributions (SEDs) of these sources when a common redshift of 2.5 and typical values of the dust parameters for SMGs are adopted. Hence, we speculate that these SMGs might be located in a filament of the distant ‘cosmic web’. The length of this candidate cosmic filament crossing the whole map is at least 4 cMpc (comoving), and the separations between sources are between 0.25 cMpc and 1.25 cMpc at this redshift, in line with expectations from cosmological simulations. Nonetheless, further observations to determine the precise spectroscopic redshifts of these sources are required to definitively support this hypothesis of SMGs embedded in a cosmic filament of dark matter.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Imaging orbital ferromagnetism in a moiré Chern insulator

Capturing exotic magnetism Ferromagnetism is associated with the breaking of time-reversal symmetry, most frequently by the spin degree of freedom. Although the orbital motion of electrons can also contribute to ferromagnetism, in most materials, it is small relative to the spin contribution. Tschirhart et al. showed that the reverse is true in an unusual magnetic state hosted by twisted bilayer graphene. Their scanning magnetometry measurements were consistent with ferromagnetism of predominantly orbital origin. Science , abd3190, this issue p. 1323

Science & Technology - Other Topics↗
NASA NTRS1975

Electron currents associated with an auroral band

Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed.

Spiger, R. J.↗
NASA NTRS1989

Calibration of polarimetric radar systems

A practical technique is proposed for calibrating single-antenna polarimetric radar systems using a metal sphere plus any second target with a strong cross-polarized radar cross section. It is shown that all magnitudes and phases (relative to one of the like-polarized linear polarization configurations) of the radar transfer function can be calibrated without knowledge of the scattering matrix of the second target. Comparison of values measured (using this calibration technique) for a tilted cylinder at X-band with theoretical values shows agreement with + or - 0.3 dB in magnitude and + or - 5 deg in phase. The technique is particularly useful for calibrating a radar under field conditions because it does not require careful alignment of calibration targets.

Sarabandi, K.↗
NASA NTRS2007

Differential Radiometers Using Fabry-Perot Interferometric Technique for Remote Sensing of Greenhouse Gases

A new type of remote sensing radiometer based upon the Fabry-Perot interferometric technique has been developed at NASA's Goddard Space Flight Center and tested from both ground and aircraft platform. The sensor uses direct or reflected sunlight and has channels for measuring column concentration of carbon dioxide at 1570 nm, oxygen lines sensitive to pressure and temperature at 762 and 768 nm, and water vapor (940 nm). A solid Fabry-Perot etalon is used as a tunable narrow bandpass filter to restrict the measurement to the gas of interest's absorption bands. By adjusting the temperature of the etalon, which changes the index of refraction of its material, the transmission fringes can be brought into nearly exact correspondence with absorption lines of the particular species. With this alignment between absorption lines and fringes, changes in the amount of a species in the atmosphere strongly affect the amount of light transmitted by the etalon and can be related to gas concentration. The technique is applicable to different chemical species. We have performed simulations and instrument design studies for CH4, "Cot isotope, and CO detection. Index Terms- Absorbing media, Atmospheric measurements, Fabry-Perot interferometers, Optical interferometry, Remote sensing.

Georgieva, Elena M.↗
NASA NTRS1981

Multispectral scanner flight model (F-1) radiometric calibration and alignment handbook

This handbook on the calibration of the MSS-D flight model (F-1) provides both the relevant data and a summary description of how the data were obtained for the system radiometric calibration, system relative spectral response, and the filter response characteristics for all 24 channels of the four band MSS-D F-1 scanner. The calibration test procedure and resulting test data required to establish the reference light levels of the MSS-D internal calibration system are discussed. The final set of data ("nominal" calibration wedges for all 24 channels) for the internal calibration system is given. The system relative spectral response measurements for all 24 channels of MSS-D F-1 are included. These data are the spectral response of the complete scanner, which are the composite of the spectral responses of the scan mirror primary and secondary telescope mirrors, fiber optics, optical filters, and detectors. Unit level test data on the measurements of the individual channel optical transmission filters are provided. Measured performance is compared to specification values.

Source record↗
DOE OSTI2025

Electrical transport and torque magnetometry studies of the kagome compound LuV 6 ⁢Sn 6 under high magnetic fields

We present a comprehensive investigation of the kagome metal LuV 6 ⁢Sn 6 through magnetotransport and torque magnetometry studies in magnetic fields up to 41 T and temperatures as low as 0.3 K. Magnetoresistance measurements up to 31 T reveal clear Shubnikov–de Haas (SdH) oscillations with two dominant frequency peaks: 𝐹 𝛼 =12 T and 𝐹 𝛽 =155 T. The Berry phase Φ 𝐁 , calculated from Landau level fan diagrams, indicates a nontrivial topology for both the 𝛼- and 𝛽-orbits. To explore the possibility of higher-frequency signals in LuV 6 ⁢Sn 6 , we employed another technique: torque magnetometry. Torque measured with applied fields up to 41 T reveals clear de Haas–van Alphen (dHvA) oscillations, with frequency signals as high as 10 kT. Angular and temperature-dependent quantum oscillation measurements allowed us to extract the effective mass of charge carriers and map the Fermi surface of LuV 6 ⁢Sn 6 . To complement the experimental findings, we performed electronic band structure and Fermi surface calculations. The electronic bands of LuV 6 ⁢Sn 6 reveal intriguing features, including flat bands, van Hove singularities, and Dirac points near the Fermi level. Two bands cross the Fermi level, contributing a deformed cylindrical shape at the Γ-point and small chainlike Fermi surfaces near the Brillouin zone boundaries. Theoretical quantum oscillation frequencies derived from Fermi surface cross-sectional areas align well with experimental SdH and dHvA results. These combined experimental and theoretical insights provide a deeper understanding of the electronic structure of LuV 6 ⁢Sn 6 and establish the foundation for exploring electronic properties in other vanadium- and titanium-based kagome systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRSDate not supplied

Atmospheric Escape from Magnetized Rocky Exoplanets

Recent Kepler and TESS observations discovered many rocky exoplanets in habitable zones around active main-sequence stars. The upper atmospheres of exoplanets are subject to two important energy sources derived from their host stars. First, the stellar photon flux in the X-ray and XUV bands ionizes and heats the upper atmosphere, driving atmospheric heating, affecting the conductance, and enhancing atmospheric escape. Second, the stellar wind’s interaction with the exoplanet’s intrinsic magnetic field transfers energy to the atmosphere through field aligned currents and Poynting flux. That energy is dissipated in the high latitude cusp and auroral regions through Joule heating which can inflate the atmosphere and also enhance the atmospheric escape rate. This presentation will discuss recent advances in modeling these energy inputs and their consequences for exoplanetary habitability. Also, I will discuss the development of a new model, the (exo) PLANETary Ionosphere-Thermosphere Tool for Research (PLANET-ITTR) and some early results from it.

William Danchi↗
DOE OSTI2026

Optimal Operation of Residential High Performance Water Heater for Reduction of Electricity Cost and Peak Demand Through Field Validation

Water heating accounts for about 18% of a typical US home’s energy use. Modern water heaters have enabled control options through APIs, offering customers the opportunity to reduce their energy cost and peak demand by dynamically adjusting settings. A water heater’s capacity to store energy using its storage tank makes it an asset for peak demand reduction and energy cost savings. For this reason, a mixed-integer linear programming model is proposed to minimize the energy cost of a high-performance water heater while also reducing the peak demand of the residential household under a time-of-use utility rate by dynamically changing the water heater’s running mode. Specifically, a multi-objective optimization model is formulated to determine the mode settings of the water heater considering hot water use, time-of-use rate, and peak demand limit of the residential household. The mode settings are associated with different dead bands of water temperature for triggering on/off action of the heat pump and heating element. A 66-gal hybrid electric high performance water heater was used for numerical simulation and practical experiments. The simulation results were well aligned with measurements of practical experiments, validating the soundness of the thermodynamic model. In addition, reductions of energy cost, enabling affordability, and reducing peak demand are demonstrated. The research team also developed a software framework with dashboards to automatically and continuously monitor and manage devices.

Liu, Guodong [ORNL] (ORCID:0000000213498608)↗
NASA NTRS1984

Field-aligned electron density irregularities near 500 km. Equator to polar cap topside sounder Z mode observations

In addition to spread F, evidence for field-aligned electron density irregularities is commonly observed on Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, these Z mode waves (and stimulated electrostatic waves at the plasma frequency) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. The radio frequency (RF) noise environment to be expected in the 400 to 500 km altitude region from low to high latitudes was examined by analyzing perigee Alouette 2 topside sounder data. All observed noise bands were scaled on nearly 200 topside sounder ionograms recorded near perigee at low, mid, and high latitude telemetry stations. The minimum and maximum frequencies of each noise band were entered into a data base or compuer analysis. The signals of primary interest in the perigee study were found to be sounder-generated.

Benson, R. F.↗
NASA NTRS1985

Field-aligned electron density irregularities near 500 km Equator to polar cap topside sounder observations

In addition to spread F, evidence for field-aligned electron density irregularities is commonly observed on Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, these Z mode waves (and stimulated electrostatic waves at the plasma frequency) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. The radio frequency (RF) noise environment to be expected in the 400 to 500 km altitude region from low to high latitudes was examined by analyzing perigee Alouette 2 topside sounder data. All observed noise bands were scaled on nearly 200 topside sounder ionograms recorded near perigee at low, mid, and high latitude telemetry stations. The minimum and maximum frequencies of each noise band were entered into a data base or computer analysis. The signals of primary interest in the perigee study were found to be sounder-generated.

Benson, R. F.↗
NASA NTRS2004

A Two-Dimensional, Semiconducting Bolometer Array for HAWC

The Stratospheric Observatory For Infrared Astronomy's (SOFIA's) High resolution Airborne Wideband Camera (HAWC) will use an ion-implanted silicon bolometer array developed at NASA s Goddard Space Flight Center (GSFC). The GSFC Pop-Up Detectors (PUDs) use a unique folding technique to enable a 12 x 32 element closepacked array of bolometers with a filling factor greater than 95%. The HAWC detector uses a resistive metal film on silicon to provide frequency independent, approx. 50% absorption over the 40 - 300 micron band. The silicon bolometers are manufactured in 32-element rows within silicon frames using Micro Electro Mechanical Systems (MEMS) silicon etching techniques. The frames are then cut, "folded", and glued onto a metallized, ceramic, thermal bus "bar". Optical alignment using micrometer jigs ensures their uniformity and correct placement. The rows are then stacked side-by-side to create the final 12 x 32 element array. A kinematic Kevlar suspension system isolates the 200 mK bolometer cold stage from the rest of the 4K detector housing. GSFC - developed silicon bridge chips make electrical connection to the bolometers, while maintaining thermal isolation. The Junction Field Effect Transistor (JFET) preamplifiers for all the signal channels operate at 120 K, yet they are electrically connected and located in close proximity to the bolometers. The JFET module design provides sufficient thermal isolation and heat sinking for these, so that their heat is not detected by the bolometers. Preliminary engineering results from the flight detector dark test run are expected to be available in July 2004. This paper describes the array assembly and mechanical and thermal design of the HAWC detector and the JFET module.

Voellmer, George M.↗
NASA NTRS2020

Characterization and Commissioning of a Ka-Band Ground Station for Cognitive Algorithm Development

In 2018, the Cognitive Communications and Propagation projects completed installation and checkout testing of a new Ka-Band ground station at the NASA Glenn Research Center in Cleveland, Ohio. The Cognitive Algorithms Demonstration Testbed (CADeT) was developed to provide a fully characterized and controllable dynamic link environment to researchers looking to demonstrate hardware and software aligned with atmospheric sensing and cognitive algorithms. CADeT integrates a host of precision control and measurement systems in addition to repurposing a 5.5 meter beam-waveguide dish platform previously used with the Advanced Communications Technology Satellite (ACTS). This paper will discuss the laboratory testing of ground station components with a emphasis on elements vital to achieving link budget requirements including characterization of the new Gallium Nitride (GaN) Solid State Power Amplifier (SSPA) and far-field measurements of the new antenna feed. Finally, the paper discusses in-situ tests conducted with CADeT and the Tracking and Data Relay Satellite System (TDRSS) to validate laboratory results and make necessary link budget adjustments before reviewing the lessons learned.

Cameron M Seidl↗
DOE OSTI2024

Spontaneous emergence of straintronics effects and striped stacking domains in untwisted three-layer epitaxial graphene

Emergent electronic phenomena, from superconductivity to ferroelectricity, magnetism, and correlated many-body band gaps, have been observed in domains created by stacking and twisting atomic layers of Van der Waals materials. In graphene, emergent properties have been observed in ABC stacking domains obtained by exfoliation followed by expert mechanical twisting and alignment with the desired orientation, a process very challenging and nonscalable. Here, conductive atomic force microscopy shows in untwisted epitaxial graphene grown on SiC the surprising presence of striped domains with dissimilar conductance, a contrast that demonstrates the presence of ABA and ABC domains since it matches exactly the conductivity difference observed in ABA/ABC domains in twisted exfoliated graphene and calculated by density functional theory. The size and geometry of the stacking domains depend on the interplay between strain, solitons crossing, and shape of the three-layer regions. Interestingly, we demonstrate the growth of three-layer regions in which the ABA/ABC stacking domains self-organize in stable stripes of a few tens of nanometers. The growth-controlled production of isolated and stripe-shaped ABA/ABC domains open the path to fabricate quantum devices on these domains. These findings on self-assembly formation of ABA/ABC epitaxial graphene stripes on SiC without the need of time-consuming and nonscalable graphene exfoliation, alignment, and twisting provide different potential applications of graphene in electronic devices.

Rejhon, Martin (ORCID:000000017775487X)↗
NASA NTRS1994

Statistical study of ULF wave occurrence in the dayside magnetosphere

Ultralow-frequency (ULF) waves are observed almost everywhere in the dayside magnetosphere. The mechanism by which these waves are generated and transformed in the dayside magnetosphere is still not understood. Here we report a statistical study of these waves based on magnetic field data from the International Sun-Earth Explorer 1 (ISEE 1) spacecraft. Data from the first traversal of the spacecraft through the entire dayside magnetosphere have been examined to determine the spatial distribution of wave occurrence. Successive 20-min segments of data were transformed to a field-aligned coordinate system. The parallel component was detrended and all three components of the field spectrally analyzed. Wave occurrence was defined by the presence of significant peaks in the power spectra. Wave events were categorized by three wave frequency bands: Pc 3 with T approximately 10-45 s; Pc 4 with T approximately 45-150 s; the short-period part of the Pc 5 wave band with T approximately 150-324 s. Properties of the spectral peaks were then entered into a data base. The data base was next sorted to determine the spatial occurrence pattern for the waves. Our results show that Pc 3 waves most frequently occur just outside synchronous orbit and are approximately centered on local noon. Pc 4 waves have a similar distribution with its peak further out. Pc 5 waves have high occurrence rate at the two flanks of the magnetosphere. Peaks in spectra obtained near the magnetopause are less clearly defined than those deeper in the magnetosphere.

Cao, M.↗
NASA NTRS2003

Use of Multi-Resolution Wavelet Feature Pyramids for Automatic Registration of Multi-Sensor Imagery

The problem of image registration, or alignment of two or more images representing the same scene or object, has to be addressed in various disciplines that employ digital imaging. In the area of remote sensing, just like in medical imaging or computer vision, it is necessary to design robust, fast and widely applicable algorithms that would allow automatic registration of images generated by various imaging platforms at the same or different times, and that would provide sub-pixel accuracy. One of the main issues that needs to be addressed when developing a registration algorithm is what type of information should be extracted from the images being registered, to be used in the search for the geometric transformation that best aligns them. The main objective of this paper is to evaluate several wavelet pyramids that may be used both for invariant feature extraction and for representing images at multiple spatial resolutions to accelerate registration. We find that the band-pass wavelets obtained from the Steerable Pyramid due to Simoncelli perform better than two types of low-pass pyramids when the images being registered have relatively small amount of nonlinear radiometric variations between them. Based on these findings, we propose a modification of a gradient-based registration algorithm that has recently been developed for medical data. We test the modified algorithm on several sets of real and synthetic satellite imagery.

Zavorin, Ilya↗
NASA NTRS1972

Banded whistlers observed on OGO-4

Inspection of broadband VLF records from OGO-4 shows that some whistlers exhibit a banded structure in which one or more bands of frequencies are missing from the whistler's spectrum. The phenomenon is commonly observed by satellites on midlatitude field lines at all local times and at various longitudes around the world. The dispersion of banded whistlers (BW) is of several tens of sec to the 1/2 power, indicating that they originated in the opposite hemisphere and are propagating downward at the satellite. BW are generally spread in time (tenths of seconds) rather than sharply defined and tend to occur at random. The frequency spacing of the bands may be either uniform or irregular, and may vary radically between successive events. Several possible explanations for BW are considered. In particular, an analysis of the interaction of plane electromagnetic waves traveling in an anisotropic plasma with a field aligned slab of enhanced ionization is presented with promising results.

Paymar, E. M.↗
DOE OSTI2021

Electronic, structural and magnetic properties of Mn (1+x) Pt (1-x) Sb

Electronic and magnetic properties of half-metallic Heusler alloys can be modified by tuning their chemical compositions. We have carried out a combined theoretical and experimental investigation of Mn (1+x) Pt (1-x) Sb (0 ≤ x ≤ 0.5) alloys. Our first-principles calculations indicate that the stoichiometric MnPtSb exhibits nearly half-metallic band structure, but a robust half-metallicity can be achieved in Mn-rich compositions Mn (1+x) Pt (1-x) Sb (0 ≤ x ≤ 0.5) with x = 0.25 and higher in their cubic structures. In addition, while MnPtSb exhibits ferromagnetic alignment, Mn (1+x) Pt (1-x) Sb are ferrimagnetic for all non-zero values of x. We have also synthesized cubic MnPtSb and Mn 1.25 Pt 0.75 Sb alloys using arc melting and annealing. The magnetic properties of these alloys are consistent with our theoretical predictions. Furthermore, these results indicate that the Mn-rich Mn (1+x) Pt (1-x) Sb alloys have potential for spin-transport-based devices.

36 MATERIALS SCIENCE↗