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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Field-aligned current signatures in the near-tail region. I - ISEE observations in the plasma sheet boundary layer

Field-aligned currents in the near-tail region are examined using ISEE magnetometer data. Two substorms (the 1054 UT and the 1436 UT substorms on March 22, 1979) were examined, demonstrating the consistency of the current polarity and intensity with observations at lower altitudes, which suggests that field-aligned currents in the plasma sheet boundary layer are parts of the large-scale current system, the region-1 system. An examination of the steplike changes of the magnetic field direction, which correspond to the spacecraft crossing of a net field-aligned current, showed that the field-aligned currents in the plasma sheet boundary layer have the same polarity as the region-1 system.

Ohtani, S.↗
NASA NTRS2019

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

The history of the Greenland Ice Sheet has been influenced by the geodynamic response to ice sheet fluctuations, and this interaction may help explain past deglaciations under modest climate forcing. We hypothesize that when the Iceland hot spot passed beneath north‐central Greenland, it thinned the lithosphere and left anomalous heat likely with partially melted rock; however, it did not break through the crust to supply voluminous flood basalts. Subsequent Plio‐Pleistocene glacial‐interglacial cycles caused large and rapidly migrating stresses, driving dike formation and other processes that shifted melted rock toward the surface. The resulting increase in surface geothermal flux favored a thinner, faster‐responding ice sheet that was more prone to deglaciation. If this hypothesis of control through changes in geothermal flux is correct, then the long‐term (10 (sup 5) to 10 (sup 6) years) trend now is toward lower geothermal flux, but with higher‐frequency (less than or equal to 10( sup 4) to 10 (sup 5) years) oscillations linked to glacial‐interglacial cycles. Whether the geothermal flux is increasing or decreasing now is not known but is of societal relevance due to its possible impact on ice flow. We infer that projections of the future of the ice sheet and its effect on sea level must integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic, and paleoclimatic information.

Greenland Ice Sheet↗
NASA NTRS1971

Magnetospheric substorms in the distant magnetotail observed by Imp 3.

Study of variations of the magnetic field and plasma sheet in the distant magnetotail (20 to 40 earth radii) during magnetospheric substorms on the basis of the Imp 3 magnetic-field and particle data. Depending on the locations of the satellite with respect to the boundary of the plasma sheet, the variations differ greatly. However, the present results and the results of other workers give a clear indication of an increase of the magnitude of the field outside the plasma sheet and of the simultaneous ?thinning' of the plasma sheet during an early phase of substorms. At about the maximum epoch or during the recovery phase of substorms, the plasma sheet expands and appears to be inflated to at least the presubstorm level. Furthermore, a large excessive flux of the magnetic (approximately equal to Z component) field, as compared with the flux of the original dipole field, appears across the neutral sheet.

Meng, C. I.↗
NASA NTRS2005

Fluctuations in Conjunction Miss Distance Projections as Time Approaches Time of Closest Approach

A responsibility of the Trajectory Operations Officer is to ensure that the International Space Station (ISS) avoids colliding with debris. United States Space Command (USSPACECOM) tracks and catalogs a portion of the debris in Earth orbit, but only objects with a perigee less than 600 km and a radar cross section (RCS) greater than 10 cm-objects that, in fact, represent only a small fraction of the objects in Earth orbit. To accommodate for this, the ISS uses shielding to protect against collisions with smaller objects. This study provides a better understanding of how quickly, and to what degree, USSPACECOM projections tend to converge to the final, true miss distance. The information included is formulated to better predict the behavior of miss distance data during real-time operations. It was determined that the driving components, in order of impact on miss distance fluctuations, are energy dissipation rate (EDR), RCS, and inclination. Data used in this analysis, calculations made, and conclusions drawn are stored in Microsoft Excel log sheets. A separate log sheet, created for each conjunction, contains information such as predicted miss distances, apogee and perigee of debris orbit, EDR, RCS, inclination, tracks and observations, statistical data, and other evaluation/orbital parameters.

Christian, John A., III↗
DOE OSTI2014

Biomass Compositional Analysis: NIR Rapid Methods (Fact Sheet)

NREL biomass analysis scientists use near-infrared (NIR) spectroscopy correlated with compositional data, produced using traditional wet chemical techniques, to develop rapid calibration models. These models dramatically decrease the time required for (and the cost of) routine compositional analyses. NREL has models to predict the composition of a variety of biomass types.

09 BIOMASS FUELS↗
DOE OSTI2019

SCISR Slick sheet

The SCISR radio is a small (cell phone size), light-weight, digital data link designed to pass high capacity IP traffic in diverse spectral environments. Multiple vendors produce baseline SCISR radios – built upon the government owned BE-CDL specifications. All SCISR radios are interoperable with each other, as well as any BE-CDL compliant terminal.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1994

Midtail plasma flows and the relationship to near-Earth substorm activity: A case study

Recent simulations of magnetotail reconnection have pointed to a link between plasma flows, dipolarization, and the substorm current wedge. In particular, Hesse and Birn (1991) have proposed that earthward jetting of plasma from the reconnection region transports flux into the near-Earth region. At the inner edge of the plasma sheet this flux piles up, producing a dipolarization of the magnetic field. The vorticity produced by the east-west deflection of the flow at the inner edge of the plasma sheet gives rise to field-aligned currents that have region 1 polarity. Thus in this scenario the earthward flow from the reconnection region produces the dipolarization ad the current wedge in a self-consistent fashion. In this study we examine observations made on April 8, 1985 by the Active Magnetospheric Particle Tracer Explorers (AMPTE)/Ion Release Module (IRM), the geosynchronous satellites 1979-053, 1983-019, and 1984-037, and Syowa station, as well as AE. This event is unique because IRM was located near the neutral sheet in the midnight sector for am extended period of time. Ground data show that there was ongoing activity in the IRM local time sector for several hours, beginning at 1800 UT and reaching a crescendo at 2300 UT. This activity was also accompanied by energetic particle variations, including injections, at geosynchronous orbit in the nighttime sector. Significantly, there were no fast flows at the neutral sheet until the great intensification of activity at 2300 UT. At that time, IRM recorded fast eartheard flow simultaneous with a dipolatization of the magetic field. We conclude that while the aforementioned scenario for the creation of the current wedge encounters serious problems explaining the earlier activity, the observations at 2300 UT are consistent with the scenario of Hesse and Birn (1191). On that basis it is argued that the physics of substorms is not exclusively rooted in the development of a global tearing mode. Processes at the inner edge of the cross-tail current that cause a disruption of the current and a consequent dipolarization and current wedge may be unrelated to the formation of a macroscale reconnection region. Thus the global evolution of a substorm is probably a complicated superposition of such processes operating on a very localized scale and a global macroscale process that allows for such things as releasing te energy stored in lobe flux and creation of plasmoids.

Lopez, R. E.↗
NASA NTRS2017

Impact of MODIS Sensor Calibration Updates on Greenland Ice Sheet Surface Reflectance and Albedo Trends

We evaluate Greenland Ice Sheet (GrIS) surface reflectance and albedo trends using the newly released Collection 6 (C6) MODIS (Moderate Resolution Imaging Spectroradiometer) products over the period 2001-2016. We find that the correction of MODIS sensor degradation provided in the new C6 data products reduces the magnitude of the surface reflectance and albedo decline trends obtained from previous MODIS data (i.e., Collection 5, C5). Collection 5 and 6 data product analysis over GrIS is characterized by surface (i.e., wet vs. dry) and elevation (i.e., 500-2000 m, 2000 m and greater) conditions over the summer season from 1 June to 31 August. Notably, the visible-wavelength declining reflectance trends identified in several bands of MODIS C5 data from previous studies are only slightly detected at reduced magnitude in the C6 versions over the dry snow area. Declining albedo in the wet snow and ice area remains over the MODIS record in the C6 product, albeit at a lower magnitude than obtained using C5 data. Further analyses of C6 spectral reflectance trends show both reflectance increases and decreases in select bands and regions, suggesting that several competing processes are contributing to Greenland Ice Sheet albedo change. Investigators using MODIS data for other ocean, atmosphere and/or land analyses are urged to consider similar re-examinations of trends previously established using C5 data.

radiative forcing↗
NASA NTRS1994

Comparison of radar-altimetry data over Greenland with surface topography derived from airborne laser altimetry

During the Summers of 1991, 1992, and 1993, NASA flew a scanning laser altimeter over transects of the Greenland ice sheet. Airplane location was measured precisely using differential Global Positioning System (GPS) surveying techniques. This allowed all altimetry data to be reduced to an estimate of ice surface elevations relative to the Earth ellipsoid. Repeat flights over the same areas indicate data consistency to 10 to 20 cm. Many of the aircraft flights were made along the ERS-1 'radar-altimeter footprint track' for a commissioning phase orbit. Rigorous comparison between the ERS-1 altimeter measurements and those from the laser altimeter will require analysis of individual ERS-1 altimeter waveforms, and since the information needed to do this is not yet available, results from comparison of TOPEX (Topology Ocean Experiment) Poseidon (T/P) radar altimetry data with laser data obtained at the northernmost limit of the T/P orbits are presented.

Thomas, R. H.↗
DOE OSTI2015

Electronic structure of Ce 2 RhIn 8 : A two-dimensional heavy-fermion system studied by angle-resolved photoemission spectroscopy

We use angle-resolved photoemission spectroscopy (ARPES) to study the 2D heavy fermion superconductor, Ce₂RhIn₈. The Fermi surface is rather complicated and consists of several hole and electron pockets with one of the sheets displaying strong nesting properties with a q-vector of (0.32, 0.32) π/a. We do not observe k z dispersion of the Fermi sheets, which is consistent with the expected 2D character of the electronic structure. Comparison of the ARPES data to band structure calculations suggests that a localized picture of the f-electrons works best. While there is some agreement in the overall band dispersion and location of the Fermi sheets, the model does not reproduce all observed bands and is not completely accurate for those it does. As a result, our data paves the way for improving the band structure calculations and the general understanding of the transport and thermodynamical properties of this material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1979

ISEE 1 and 2 particle observations of outer plasma sheet boundary

Observations of particle structures by a medium-energy particle experiment on the ISEE 1 and 2 spacecraft at a distance of about 20 earth radii in the geomagnetic tail are presented. Comparison of these data with plasma data indicates the existence of a layer of energetic electrons and ions just outside the plasma sheet. The region outside the plasma sheet in the high-latitude lobe is permeated with low-intensity low-energy (about 1.5 KeV) ions. These particle structures have velocities of a few kilometers per second to at least about 60 km/s. Large-scale motions are observed with onset and recovery of substorms. The dimensions of the particle structures are estimated to range from about 200 to 10,000 km at 20 earth radii. The particle structures are dependent upon the energy as well as the species of the particles.

Parks, G. K.↗
DOE OSTI2020

Offshore Wind Technology Data Update (2019) [Slides]

The 2019 Offshore Wind Technology Data Update compiles information from peer-reviewed literature, market reports, press releases, industry news reports, manufacturer specification sheets, and offshore wind project announcements to provide a comprehensive snapshot of the state of the global wind industry in 2019. These data, including capacity projections, project characteristics, technology trends, and cost estimates, are categorized, tabulated, and plotted to provide easily recognizable and understandable summaries. A particular focus is given to the United States offshore wind project pipeline, including project announcements, state procurements, deployment timelines, infrastructure investments, grid interconnections, and other related developments. The update is intended to be used as a reference document by researchers, analysts, industry practitioners, and government officials.

17 WIND ENERGY↗
DOE OSTI2018

Structure of Longitudinal and Transverse Currents in Current Sheets

The structure of magnetic fields and currents in current sheets formed in 2D and 3D magnetic configurations with an X line is analyzed using experimental data. It is found that, in addition to the main (longitudinal) current, transverse currents comparable in magnitude with the main current are also generated in current sheets. Relations between the longitudinal and transverse currents in current sheets formed in different magnetic configurations are obtained. The vectors of the total currents and their deviations from the direction of the main current in different regions of the sheet are determined. It is shown that the total magnetic fields and currents in current sheets have a 3D structure.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Setups for eliminating static charge of the ATLAS18 strip sensors

Abstract Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to beable to track charged particles produced at the High-Luminosity LHC, started in 2020 and is expected tocontinue till 2028. The ITk detector will include 18,000 highly segmented and radiation hard n+-in-psilicon strip sensors (ATLAS18), which are being manufactured by Hamamatsu Photonics. Mechanical and electrical characteristics of produced sensors are measured upon their delivery at several institutes participating in a complex Quality Control (QC) program. The QC tests performed on each individual sensor check the overall integrity and quality of the sensor.During the QC testing of ATLAS18 strip sensors, an increased number of sensors thatfailed the electrical tests was observed. In particular, IV measurements indicated an early breakdown,while large areas containing several tens or hundreds of neighbouring strips with low interstrip isolationwere identified by the Full strip tests, and leakage current instabilities were measured in a long-term leakage current stability setup. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts per inch was measured on a large number of sensors and on the plastic sheets, whichmechanically protect these sensors in their paper envelopes. Accumulated data indicates a clearcorrelation between observed electrical failures and the sensor charge-up.To mitigate the above-described issues, the QC testing sites significantly modified the sensor handlingprocedures and introduced sensor recovery techniques based on irradiation of the sensor surface with UVlight or application of intensive flows of ionized gas. In this presentation, we will describe the setupsimplemented by the QC testing sites to treat silicon strip sensors affected by static charge andevaluate the effectiveness of these setups in terms of improvement of the sensor performance.

Instruments & Instrumentation↗
DOE OSTI2024

Modeling and Simulation of Electrostatics of Ge$_{\text{1-x}}$Sn$_{\text{x}}$ Layers Grown on Ge Substrates

This work introduces a comprehensive simulation tool that provides a robust 1D Schrödinger – Poisson solver for modeling the electrostatics of heterostructures with an arbitrary number of layers, and non-uniform doping profiles along with the treatment of partial ionization of dopants at low temperatures. The effective masses are derived from the first-principles calculations. The solver is used to characterize three Ge 1-x Sn x /Ge heterostructures with non-uniform doping profiles and determine the subband structure at various temperatures. Here, the simulation results of the sheet carrier densities show excellent agreement with the experimentally extracted data, thus demonstrating the capabilities of the solver.

42 ENGINEERING↗
DOE OSTI2023

Offshore-onshore record of Last Glacial Maximum–to–present grounding line retreat at Pine Island Glacier, Antarctica

Pine Island Glacier, West Antarctica, is the largest Antarctic contributor to global sea-level rise and is vulnerable to rapid retreat, yet our knowledge of its deglacial history since the Last Glacial Maximum is based largely on marine sediments that record a retreat history ending in the early Holocene. Using a suite of 10 Be exposure ages from onshore glacial deposits directly adjacent to Pine Island Glacier, we show that this major glacier thinned rapidly in the early to mid-Holocene. Our results indicate that Pine Island Glacier was at least 690 m thicker than present prior to ca. 8 ka. We infer that the rapid thinning detected at the site farthest downstream records the arrival and stabilization of the retreating grounding line at that site by 8–6 ka. By combining our exposure ages and the marine record, we extend knowledge of Pine Island Glacier retreat both spatially and temporally: to 50 km from the modern grounding line and to the mid-Holocene, providing a data set that is important for future numerical ice-sheet model validation.

58 GEOSCIENCES↗
NASA NTRS1978

Chatanika radar observations of ionospheric and field-aligned currents

A method for estimating field-aligned current densities from ground-based measurements of the horizontal ionospheric currents at two or more latitudes using the Chatanika incoherent scatter radar is presented. It is assumed that the one-dimensional divergence of the horizontal currents approximates the current density of a field-aligned current sheet. The field-aligned current densities found via radar data agree with those given by simultaneous magnetic observations by the Triad satellite. It is noted that downward or upward field-aligned currents having densities of 10 to the -6th to 10 to the -5th A/sq m are achieved in the evening or morning sector. The densities are further increased during periods of increased geomagnetic activity and when current directions are reversed. This reversal generally occurs during auroral oval expansion.

Kamide, Y.↗
NASA NTRS1982

Merging LANDSAT Derived Land Covers into Quad-referenced Geographic Information Systems

An approach for merging multiscene LANDSAT data bases into existing geographic information systems having 5-second or smaller cells is described. The approach uses the output from the State of Maryland's UNIVAC 1180-based LANDSAT classification program ASTEP (Algorithm Simulation Test and Evaluation) developed by NASA. The structure of the technique was designed to address the problems that emerged as part of the LANDSAT classification of the 64,000 square mile Chesapeake water shed involving twelve scenes. The removal of overlap among adjacent scenes, the crossreferencing of ground control points, and the isolation of the appropriate pixels from the LANDSAT data base for subsequent positioning into a file containing ancillary data referenced to a specific USGS 7 1/2 minute quadrangle sheet are described. Examples illustrate the clustering of classified LANDSAT pixels to define the dominant land use for each of 8,100 cells within a series of quadrangle sheets distributed over the State of Maryland. The approach uses a hard copy terminal tied to an ASTEP algorithm through telephone lines. A coordinate digitizing board for inputing the position of ground control points is also valuable, although manual measurements are possible. The approach is quite efficient and should be especially attractive for use on regional scale studies.

White, J. M.↗