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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Saturn's E, G, and F rings - Modulated by the plasma sheet?

Saturn's broad E ring, the narrow G ring, and the structured and apparently time-variable F ring(s) contain many micron and submicron-sized particles, which make up the 'visible' component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. In addition, Coulomb drag forces may be important, in particular for the E ring. The possibility that electromagnetic effects may play a role in determining the F ring structure and its possible time variations is critically examined. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 100 to 10,000 years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

Morfill, G. E.↗
NASA NTRS2016

The e-astrogam Gamma-Ray Space Mission

e-ASTROGAM is a gamma-ray space mission to be proposed as the M5 Medium-size mission of the European Space Agency. It is dedicated to the observation of the Universe with unprecedented sensitivity in the energy range 0.2-100 MeV, extending up to GeV energies, together with a groundbreaking polarization capability. It is designed to substantially improve the COMPTEL and Fermi sensitivities in the MeV-GeV energy range and to open new windows of opportunity for astrophysical and fundamental physics space research. e-ASTROGAM will operate as an open astronomical observatory, with a core science focused on (1) the activity from extreme particle accelerators, including gamma-ray bursts and active galactic nuclei and the link of jet astrophysics to the new astronomy of gravitational waves, neutrinos, ultra-high energy cosmic rays, (2) the high-energy mysteries of the Galactic center and inner Galaxy, including the activity of the supermassive black hole, the Fermi Bubbles, the origin of the Galactic positrons, and the search for dark matter signatures in a new energy window; (3) nucleosynthesis and chemical evolution, including the life cycle of elements produced by supernovae in the Milky Way and the Local Group of galaxies. e-ASTROGAM will be ideal for the study of high-energy sources in general, including pulsars and pulsar wind nebulae, accreting neutron stars and black holes, novae, supernova remnants, and magnetars. And it will also provide important contributions to solar and terrestrial physics. The e-ASTROGAM telescope is optimized for the simultaneous detection of Compton and pair-producing gamma-ray events over a large spectral band. It is based on a very high technology readiness level for all subsystems and includes many innovative features for the detectors and associated electronics.

Compton and pair creation telescope↗
NASA NTRS2019

Does Seed Sanitization Affect the Plant Rhizosphere Microbiome and Its Ability to Compete with the Human Associated Pathogen, E. coli on Salad Crops?

Cultivation of crops in controlled environmental agricultural systems may limit microbial colonization and reduce diversity of the microbial communities. Practices like seed and growth medium sanitization may further impact microbial communities in the mature plant and the plant’s capacity to limit the growth of pathogens through competition. As humans expand their travels to space, understanding plant growth, health, and development in closed environments will be critical to the success of producing a safe, supplemental food source for astronauts. To determine the persistence of a potential human pathogen in plant growth and development, sanitized and unsanitized seeds from, mizuna (Brassica rapa var japonica) and red romaine lettuce (Lactuca sativa cultivar ‘Outredgeous’), were inoculated with Escherichia coli, ATCC 21445, germinated under simulated International Space Station (ISS) environmental conditions and harvested every 7 days until maturity. The persistence of E. coli in the rhizosphere was determined by plating on selective media, real time PCR (Polymerase Chain Reaction) and community sequencing of the rhizosphere communities. E. coli was detected in the crops’ roots and leaves for several weeks post germination. At day 28, plants from sanitized seeds had significantly higher counts of E. coli on the roots than those from unsanitized seeds. E. coli was also detected on a few uninoculated plants indicating airborne cross contamination among plants in the same growth chamber and suggesting an influence of the natural microbiome on human pathogen survival and persistence in leafy greens. Sequencing analysis revealed variations in composition and diversity between the communities. Understanding the microbial community of the rhizospheric microbiome is only the first step in determining the relationships between plants. Additional studies to include genotypic and phenotypic variations in the plants should be considered to determine if the natural microbes in the rhizosphere may contribute to the health and therefore, safety of the edible plants.

Khodadad, Christina L. M.↗
NASA NTRS1978

E region coupling effects on the Perkins spread F instability

The Perkins instability theory for mid-latitude spread F is generalized to include the effects of the E region on growth rates. A three-layer model, representing the E region, the F region, and a resistive layer of low Pedersen conductivity which separates them, is developed. The E region Pedersen current has a stabilizing effect on the perturbed F region, thereby reducing the growth rate of the instability. For spread F onset on September 17, 1974, the maximum growth rate is found to be only one third of the Perkins growth rate. The resistive layer reduces the electric field perturbation in the E region for short wavelengths but has little effect for long wavelengths.

Klevans, E. H.↗
NASA NTRS1978

Temperate zone sporadic-E maps /f/0/E/s/ greater than 7 MHz/

Three maps are presented of f(0) sporadic-E greater than 7 MHz for temperate zones. During map preparation it was assumed that: (1) the geographical area would be between plus and minus 60 deg geomagnetic latitude, excluding the equatorial zone, (2) the maps would be for f(0) sporadic-E greater than 7 MHz, (3) sunspot cycle variation would be ignored, (4) one map would represent the peak sporadic-E period with a discontinuity at the geographic equator, (5) one map would represent non-peak periods with a discontinuity at the geographic equator, (6) one map would represent all twelve months with no equatorial discontinuity, and (7) previously determined coefficients for median and upper decile f(0) sporadic-E would be extrapolated to 7 MHz.

Smith, E. K.↗
NASA NTRS1986

The laboratory millimeter-wave spectrum of methyl formate in its ground torsional E state

Over 250 rotational transitions of the internal rotor methyl formate (HCOOCH3) in its ground v(t) = 0 degenerate (E) torsional substate have been measured in the millimeter-wave spectral region. These data and a number of E-state lines identified by several other workers have been analyzed using an extension of the classical principal-axis method in the high barrier limit. The resulting rotational constants allow accurate prediction of the v(t) = 0 E substate methyl formate spectrum below 300 GHz between states with angular momentum J not greater than 30 and rotational energy of not more than 350/cm. The calculated transition frequencies for the E state, when combined with the results of the previous analysis of the ground-symmetric, nondegenerate state, account for over 200 of the emission lines observed toward Orion in a recent survey of the 215-265 GHz band.

Plummer, G. M.↗
NASA NTRS1995

Global equatorial ionospheric vertical plasma drifts measured by the AE-E satellite

Ion drift meter observations from the Atmosphere Explorer E (AE-E) satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes less than or equal to 7.5 deg) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diuurnal, seasonal, and solar cycle dependence of the logitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nighttime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longituudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors.

Fejer, B. G.↗
NASA NTRS2005

What is the Water (OH) Content of the E Asteroids?

Attempts to match the E asteroids with enstatite-rich meteorites universally conclude that the aubrites or enstatite chondrites are natural candidates, and accordingly conclude that E asteroids as a class are very water-poor. Accordingly, the highly reduced nature of typical enstatite-rich meteorites suggests that aqueous alteration was an improbable process on any E asteroid. However, there are spectroscopic observations of several E-class asteroids that suggest the presence there of hydrated phases. Examination of the Kaidun meteorite reveals the true situation.

Zolensky, M. E.↗
NASA NTRS2005

Sporadic E Morphology from GPS-CHAMP Radio Occultation

The scintillations of phase and amplitude in terms of signal-to-noise ratio (SNR) of the GPS radio occultation signal are caused by thin ionization layers. These thin irregular electron density layers in the E region ionosphere are often called sporadic E (Es). For a monthly retrieval of Es morphology we use the variances of the phase and SNR fluctuations of worldwide ~6000 GPS/CHAMP occultations in the E region. The Es climatology is studied globally with the SNR and phase variances in terms of monthly zonal means, seasonal maps, and diurnal and long-term variations. The zonal mean variances reveal strong, extended Es activities at summertime midlatitudes but weak, confined activities in wintertime high latitudes, peaking at ~105 km. Global maps at 105-km altitude show clear dependence of Es activities on the geomagnetic dip angle, where the summertime midlatitude Es occurs mostly at dip angles of 30 deg. - 60 deg. and the wintertime high-latitude enhancement occurs mostly at dip angles greater than 80 deg. The midlatitude Es variances exhibit a strong semidiurnal variation with peak hours near 0800 1000 and 2000 local solar time, respectively. The peak hours are delayed slightly with decreasing height, suggesting influences from the semidiurnal tide. To provide more insights on the observed SNR and phase variances, we model radio wave propagation for the CHAMP observing geometry under several perturbed cases in the E region ionosphere. The model simulations indicate that the SNR variance has the maximum response to Es perturbations at vertical wavelengths of 1.2 km, whereas the phase response maximizes at ~2 km (for the 1-s variance analysis). The characteristic scale depends little on the truncation time used in the SNR variance analysis, but it increases with the truncation time for the phase variances. Initial studies show that reasonable global Es morphology can be produced on a monthly and seasonal basis with the CHAMP one-antenna occultations. Better results from other existing and upcoming GPS occultation missions are anticipated in future studies, and they will significantly improve our understanding of this important phenomenon.

signal to noise ration (SNR)↗
NASA NTRS2011

Subsurface Emission Effects in AMSR-E Measurements: Implications for Land Surface Microwave Emissivity Retrieval

An analysis of land surface microwave emission time series shows that the characteristic diurnal signature associated with subsurface emission in sandy deserts carry over to arid and semi-arid region worldwide. Prior work found that diurnal variation of Special Sensor Microwave/Imager (SSM/I) brightness temperatures in deserts was small relative to International Satellite Cloud Climatology Project land surface temperature (LST) variation and that the difference varied with surface type and was largest in sand sea regions. Here we find more widespread subsurface emission effects in Advanced Microwave Scanning Radiometer-EOS (AMSR-E) measurements. The AMSR-E orbit has equator crossing times near 01:30 and 13 :30 local time, resulting in sampling when near-surface temperature gradients are likely to be large and amplifying the influence of emission depth on effective emitting temperature relative to other factors. AMSR-E measurements are also temporally coincident with Moderate Resolution Imaging Spectroradiometer (MODIS) LST measurements, eliminating time lag as a source of LST uncertainty and reducing LST errors due to undetected clouds. This paper presents monthly global emissivity and emission depth index retrievals for 2003 at 11, 19, 37, and 89 GHz from AMSR-E, MODIS, and SSM/I time series data. Retrieval model fit error, stability, self-consistency, and land surface modeling results provide evidence for the validity of the subsurface emission hypothesis and the retrieval approach. An analysis of emission depth index, emissivity, precipitation, and vegetation index seasonal trends in northern and southern Africa suggests that changes in the emission depth index may be tied to changes in land surface moisture and vegetation conditions

Galantowicz, John F.↗
NASA NTRS2016

A New Operational Snow Retrieval Algorithm Applied to Historical AMSR-E Brightness Temperatures

Snow is a key element of the water and energy cycles and the knowledge of spatio-temporal distribution of snow depth and snow water equivalent (SWE) is fundamental for hydrological and climatological applications. SWE and snow depth estimates can be obtained from spaceborne microwave brightness temperatures at global scale and high temporal resolution (daily). In this regard, the data recorded by the Advanced Microwave Scanning Radiometer-Earth Orbiting System (EOS) (AMSR-E) onboard the National Aeronautics and Space Administration's (NASA) AQUA spacecraft have been used to generate operational estimates of SWE and snow depth, complementing estimates generated with other microwave sensors flying on other platforms. In this study, we report the results concerning the development and assessment of a new operational algorithm applied to historical AMSR-E data. The new algorithm here proposed makes use of climatological data, electromagnetic modeling and artificial neural networks for estimating snow depth as well as a spatio-temporal dynamic density scheme to convert snow depth to SWE. The outputs of the new algorithm are compared with those of the current AMSR-E operational algorithm as well as in-situ measurements and other operational snow products, specifically the Canadian Meteorological Center (CMC) and GlobSnow datasets. Our results show that the AMSR-E algorithm here proposed generally performs better than the operational one and addresses some major issues identified in the spatial distribution of snow depth fields associated with the evolution of effective grain size.

passive microwave↗
NASA NTRS2023

Study of Pairwise Deconfliction Metrics to Analyze Air Traffic Complexity in Upper Class E Airspace

Upper Class E Traffic Management (ETM) is envisioned to cooperatively facilitate operations of a diverse set of aerial vehicles, such as high-altitude long-endurance fixed-wing unmanned aircraft (low-speed and high-speed), high-altitude platforms, airships, stratospheric balloons, supersonic unmanned and commercial aircraft, etc., with a wide variety of mission types, performance characteristics, communication, navigation and surveillance capabilities, maneuverability, and on-board avionics in the National Airspace System (NAS) ’above’ 60,000 feet above mean sea level, without an active and direct control from human air traffic controllers. A diverse mixture of aerial vehicle types creates significant challenges in understanding air traffic complexity, which may not correlate strongly with air traffic density. One key step for determining air traffic complexity in upper class E airspace is to first understand pairwise deconfliction metrics such as reachability, reserve area, and reserve flight time for each pair of unique aerial vehicle types under potential conflict. Therefore, pairwise deconfliction metrics are first defined, and analytical equations are derived for conflict resolution using the heading change maneuver. Next, case studies are performed to analyze deconfliction metrics to avoid secondary conflicts in upper class E airspace. The study shows that pairwise deconfliction metrics are functions of maneuverability, performance characteristics, uncertainty in position and velocity, heading angle change, and conflict angle of aerial vehicles. The next step for this research is to build a mathematical model for air traffic complexity using pairwise deconfliction metrics and validate it in an upper Class E simulation environment.

Airspace Complexity↗
NASA NTRSDate not supplied

Study of Pairwise Deconfliction Metrics to Analyze Air Traffic Complexity in Upper Class E Airspace

Upper Class E Traffic Management (ETM) is envisioned to cooperatively facilitate operations of a diverse set of aerial vehicles, such as high-altitude long-endurance fixed-wing unmanned aircraft (low-speed and high-speed), high-altitude platforms, airships, stratospheric balloons, supersonic unmanned and commercial aircraft, etc., with a wide variety of mission types, performance characteristics, communication, navigation and surveillance capabilities, maneuverability, and on-board avionics in the National Airspace System (NAS) ’above’ 60,000 feet above mean sea level, without an active and direct control from human air traffic controllers. A diverse mixture of aerial vehicle types creates significant challenges in understanding air traffic complexity, which may not correlate strongly with air traffic density. One key step for determining air traffic complexity in upper class E airspace is to first understand pairwise deconfliction metrics such as reachability, reserve area, and reserve flight time for each pair of unique aerial vehicle types under potential conflict. Therefore, pairwise deconfliction metrics are first defined, and analytical equations are derived for conflict resolution using the heading change maneuver. Next, case studies are performed to analyze deconfliction metrics to avoid secondary conflicts in upper class E airspace. The study shows that pairwise deconfliction metrics are functions of maneuverability, performance characteristics, uncertainty in position and velocity, heading angle change, and conflict angle of aerial vehicles. The next step for this research is to build a mathematical model for air traffic complexity using pairwise deconfliction metrics and validate it in an upper Class E simulation environment.

Airspace Complexity↗
NASA NTRS2014

High-Energy X-Ray Detection of G359.89-0.08 (SGR A-E): Magnetic Flux Tube Emission Powered by Cosmic Rays?

We report the first detection of high-energy X-ray (E (is) greater than 10 keV) emission from the Galactic center non-thermal filament G359.89−0.08 (Sgr A−E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to approximately 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index gamma approximately equals 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F(sub X) = (2.0 +/- 0.1) × 10(exp -12)erg cm(-2) s(-1) , corresponding to an unabsorbed X-ray luminosity L(sub X) = (2.6+/-0.8)×10(exp 34) erg s(-1) assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A−E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to (is) approximately 100 kyr) with low surface brightness and radii up to (is) approximately 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

X-rays: individual↗
NASA NTRS1973

Energetic electrons in the midlatitude nighttime E region

Nike Apache 14.439 was launched from Wallops Island at 0003 EST on 1 November 1972, a very disturbed night (K sub P = 8). A Geiger counter in the payload detected electrons ( keV) with a maximum flux of 1086 + or -261/sq cm/sec/ster. The height-averaged ionization rate in the upper E region is calculated from the measured electron density profile and has a value of 35 1/cu/cm/sec. The ionization rate can be reconciled with the observed flux of electrons ( 70 2 keV) if the spectrum ( keV) is of the form J ( E) = J sub O exp(-E/E sub O) with E sub O equal to 8.3 keV. The ionization rate on this and other nights is found to be strongly dependent on geomagnetic activity. It is suggested that energetic electrons are the principal source of ionization at midlatitudes in the upper E region near midnight, even under rather quiet geomagnetic conditions.

Smith, L. G.↗
NASA NTRS1977

The E asteroids and the origin of the enstatite achondrites

Color, polarization, and albedo data are summarized for the three known minor planets of optical type E: 44 Nysa, 64 Angelina, and 434 Hungaria. The inventory of E asteroids with dimensions in excess of 50 km is shown to be essentially complete. The surfaces of the E objects evidently consist of colorless translucent iron-free silicates such as plagioclase, forsterite, or enstatite. Their possible identification as the source of enstatite achondrites is consistent with laboratory polarimetry of the Norton County aubrite. Both Nysa and Hungaria seem to be rather favorably situated for the production of meteorites. Nysa has a highly aspherical shape and is dynamically associated with the metal-rich asteroid 135 Hertha and several small objects also apparently of the metal-depleted E type. The configuration is suggestive of the fragments of a differentiated parent body, in which Hertha originated as the iron core and Nysa as the largest surviving mantle fragment. The relative volumes, however, are not consistent with simple igneous differentiation from a chondritic composition.

Zellner, B.↗
NASA NTRS1979

Report of the mid- and low-latitude E and F Region Working Group

The formation and variation of the ionosphere is addressed with regard to the ability to understand, specify, and predict the low and mid latitude E and F regions. A brief survey of prediction methods and techniques is given for long and short term variability in the E and F regions. It is indicated that the usefulness of theoretical models to predict electron density distribution in the low and mid latitude ionospheric E and F regions is limited by the ability to predict the parameters which enter the relevant equations; i.e., neutral atmospheric constituents, neutral and charged particle temperatures, neutral wind, electric fields, and ionizing sources such as solar (E sub uv) radiation and energetic particles. It is recommended that areas for research include improving knowledge of the input parameters and how they respond to changing solar and geophysical conditions.

Rush, C. M.↗
NASA NTRS1982

The negative gravity field over the 85 deg E ridge

Two north-south ridges in the basement topography of the Bay of Bengal may be observed on an isopach map at 85 and at 90 deg E. Free-air gravity anomaly profiles across the region show a strong gravity low (about -60 mGal) over the 85 deg E ridge, and a gravity high over the other. Using a simple two-stage loading model, the negative gravity anomaly over the 85 deg E ridge is explained as a direct consequence of sediment loading, and the flexural rigidity of the lithosphere when the ridge was formed is estimated to have been about 180 times less than the flexural rigidity during the sediment loading. An approximate relationship between flexural rigidity and crustal age shows that the 85 deg E ridge was formed on relatively young lithosphere, 5-15 million years old, and that it was buried when the lithosphere was 40-80 million years old. The alteration of the gravity field by a thick layer of sediments may occur in other large sedimentary basins or along continental margins.

Liu, C.-S.↗