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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Using Dust Shed from Asteroids as Microsamples to Link Remote Measurements with Meteorite Classes

Given the diversity of asteroids, it is impossible to consider returning samples from each one• Dust particles are abundant around asteroids• Primary minerals and organic materials can be measured by in situ dust detectorinstruments• These particles can be used to classify the parent body as an ordinary chondrite,basaltic achondrite, or other class of meteorite• Such instruments could provide direct links to known meteorite groups withoutreturning the samples to terrestrial laboratories

Cohen, B. A.↗
NASA NTRS2018

Linking Improvements in Sulfur Dioxide Emissions to Decreasing Sulfate Wet Deposition by Combining Satellite and Surface Observations with Trajectory Analysis

Sulfur dioxide (SO2), a criteria pollutant, and sulfate (SO42) deposition are major environmental concerns in the eastern U.S. and both have been on the decline for two decades. In this study, we use satellite column SO2 data from the Ozone Monitoring Instrument (OMI), and SO42 wet deposition data from the NADP (National Atmospheric Deposition Program) to investigate the temporal and spatial relationship between trends in SO2 emissions and the downward sulfate wet deposition over the eastern U.S. from 2005 to 2015. To establish the relationship between SO2 emission sources and receptor sites, we conducted a Potential Source Contribution Function (PSCF) analysis using HYSPLIT back trajectories for five selected Air Quality System (AQS) sites - (Hackney, OH, Akron, OH, South Fayette, PA, Wilmington, DE, and Beltsville, MD) - in close proximity to NADP sites with large downward SO42 trends since 2005. Back trajectories were run for three summers (JJA) and three winters (DJF) and used to generate seasonal climatology PSCFs for each site. The OMI SO2 and interpolated NADP sulfate deposition trends were normalized and overlapped with the PSCF, to identify the areas that had the highest contribution to the observed drop. The results suggest that emission reductions along the Ohio River Valley have led to decreases in sulfate deposition in eastern OH and western PA (Hackney, Akron and South Fayette). Farther to the east, emission reductions in southeast PA resulted in improvements in sulfate deposition at Wilmington, DE, while for Beltsville, reductions in both the Ohio River Valley and nearby favorably impacted sulfate deposition. For Beltsville, sources closer than 300km from the site contribute roughly 56% observed deposition trends in winter, and 82% in summer, reflecting seasonal changes in transport pattern as well as faster oxidation and washout of sulfur in summer. This suggests that emissions and wet deposition are linked through not only the location of sources relative to the observing sites, but also to photochemistry and the weather patterns characteristic to the region, as evidenced by a west to east shift in the contribution between winter and summer. The method developed here is applicable to other regions with significant trends such as China and India, and can be used to estimate the potential benefits of emission reduction in those areas.

Acid depostion↗
NASA NTRS2019

Mitigating Interference from Urban Air Mobility Vehicles on Satellite Communication Links by Using Vortex Radiometry

Vortex radiometers (VR) establish an early warning system for communication systems by generating concentric annular beam patterns around the active link. Received power peaks are monitored as interfering signals traverse overhead, allowing the VR to estimate source velocity. From this information the VR determines 1) when a fade will occur, 2) how long the fade will persist for and 3) how intense the fade will be. This paper demonstrates how VRs can be used to increase the resilience of communication systems used in urban air mobility applications.

vortex radiometry↗
NASA NTRS2019

Mitigating Interference from Urban Air Mobility Vehicles on Satellite Communication Links by Using Vortex Radiometry

Vortex radiometers (VRs) establish an early warning system for communication channels by generating concentric annular beam patterns around the active link. Peaks in received power are monitored as interfering signals traverse overhead, allowing the VR to estimate source velocity. From this information the VR determines 1) when a fade will occur, 2) how long the fade will persist for and 3) how intense the fade will be. This paper demonstrates how VRs can increase the resilience of communication systems used in urban air mobility applications.

Schemmel, Peter J.↗
NASA NTRSDate not supplied

Evidence for a CERES-Sized, Water-Rich, Carbonaceous Chondrite Parent Asteroid: A Missing Link Found in the Almahata Sitta Meteorite

We have discovered abundant (~10 vol.%) tremolite amphibole in a carbonaceous chondrite (CC) fragment (202, C-ung) from the Almahata Sitta (AhS, Ur-anom) meteorite. Terrestrially, tremolite is a fairly common hydrous mineral that forms under greenschist facies conditions (300-500° C and ~2-8 kbar). Amphibole has been identified in two R chondrites at similar abundances, but it is virtually unknown in CC, having been identified only in Allende (CV3oxA) at trace to minor (likely <<1 vol.%) abundances. Thus, AhS 202 provides evidence of a previously unrecognized CC parent body that must have been of sufficient size (~500-1400 km diameter) to support prolonged, fluid-assisted metamorphism at intermediate pressures and temperatures. The previous detection of amphibole in a CC, even at very low abundances, is noteworthy as it indicates that conditions for that mineral’s formation existed in the early solar system, no matter how briefly or how localized. However, our detection of abundant amphibole in a second CC that implicates a second, large parent body suggests that moderately elevated, hydrous P/T conditions may have been more widespread than previously thought based on meteorites. The apparent absence of amphibole in most carbonaceous chondrites may reflect bias in our meteorite collections and/or failure to identify it in other samples. Finally, samples like AhS 202 provide important missing links if spaceflight missions such as Hayabusa2 and OSIRIS-REx return samples that differ from what exists in meteorite collections.

Victoria E Hamilton↗
NASA NTRS2021

On the Development and Demise of the Fall 2019 Southeast U. S. Flash Drought: Links to an Extreme Positive IOD

Much of the southeast United States experienced record dry conditions during September of 2019, with the area in abnormally dry to exceptional drought conditions growing from 25% at the beginning of the month to 80% by the end of the month. The drought ended just as abruptlydue to above normal rain that fell during the second half of October. In this study we employed MERRA-2 and the GEOS-5 AGCM to diagnose the underlying causes of the drought’s onset, maintenance, and demise. The basic approach involves performing a series of AGCM simulations in which the model is constrained to remain close to MERRA-2 over pre-specified areas that are external to the drought region. The start of the drought appears to have been forced by anomalous heating in the central/western tropical Pacific that resulted in low level anti-cyclonic flow and a tendency for descending motion over much of the southeast. An anomalous ridge associated with a Rossby wave train (emanating from the Indian Ocean region) is found to be the main source of the most intense temperature and precipitation anomalies that develop over the southeast during the last week of September. A second Rossby wave train (emanating from the same region) is responsible for the substantial rain that fell during the second half of October to end the drought. The links to the Indian Ocean Dipole (with record positive values) as well a sa waning El Nino allow some speculation as to the likelihood of similar events occurring in the future.

Siegfried D Schubert↗
NASA NTRS1994

An Overview of the Compensated Earth-Moon-Earth Laser Link (CEMERLL) Experiment

Adaptive optics can mitigate the turbulence-induced wavefront distortions that limit the minimum practical beam divergence in a ground-to-space optical link, and enable high intensity laser beam propagation through the atmosphere. The CEMERLL experiment will use laser guide star adaptive optics to transmit a near-diffraction-limited laser beam from the Starfire Optical Range to the Apollo lunar retro-reflectors. The experiment will validate theoretical models that predict the effect of atmospheric turbulence on uncompensated and compensated laser beam propagation, and explore strategies to compensate for atmosphere-induced wavefront tilt not corrected for by laser guide star adaptive optics.

adaptive↗
NASA NTRS1994

Spatial Acquisition in the Presence of Satellite Vibrations for Free Space Optical Communication Link

Laser communication systems offer distinct advantages over radio frequency based systems for near earth and particularly for deep space communicaiton links. Some of the advantages are smaller size, lower power requirements and higher data rates. However, laser beam widths are very narrow and require more precise pointing, acquisition and tracking (PAT) compared to RF communication sytems. In addition to imprecise knowledge of relative position and complex relative motion between the spacecrafts, the problem of pointing and acquisition is complicated by vibrations present in the spacecraft. This paper analyzes the impact of satellite vibration on acquisition time and acquisition probability for a charge coupled device (CCD) based acquisition scheme.

laser↗
NASA NTRS1993

Operations Automation Using the Link Monitor and Control Operator Assistant

The Link Monitor & Control Operator Assistant (LMC OA) is a knowledge-based prototype system which uses Artificial Intelligence (AI) techniques to provide semi-automated monitor and control functions to support operations of the Deep Space Network (DSN) 70-Meter antenna at the Goldstone Deep Space Communications Camplex (DSCC).

Goldstone↗
NASA NTRS1996

Galileo Telecom Link and its Application to Future Missions

On May 23, 1996, Galileo successfully switched to a new telecommunication mode with upgraded software on the spacecraft and comprehensively revised ground equipment. The new link offers multiple techniques (arraying, error-correcting coding, data compression, etc) to maximize the data return, while applying automation to minimize the complexity and cost of operations.

Galileo↗
NASA NTRS0202

Rest architecture for link analysis tools portal

A web portal is under development to improve overall services provided by NASA networks that support near-­‐Earth missions. These networks are managed by Space Communication and Navigation (SCaN) Program of NASA and include the following: Deep Space Network (DSN), Space Network (SN), and Near-­‐Earth Network (NEN). DSN is a network of antennas located in three longitudinally separated sites and supports interplanetary spacecraft missions, radio science, and radar astronomy observations. SN consists of a number of geostationary Tracking and Data Relay Satellites (TDRS) and associated ground stations. NEN consists of both NASA-­‐owned ground stations and those owned by international, commercial, and academic partners. This study investigates different web access techniques for mission users to use link analysis tools that aid in operating NASA networks. We developed a web portal prototype following principles of Representational state transfer (REST) architecture to leverage scalability, independent deployment of tools, and generic interfaces. In REST architectures, requests and responses between clients and servers are built around transferring representations of resources that can be addressed in memory. We demonstrate the feasibility of using REST architecture to facilitate web-­‐service transactions via web-­‐portal.

Lee, Carlyn-­‐Ann↗
NASA NTRS2013

A 294 GHz 0.47m W Caterpillar amplifier based transmitter in 65 nm CMOS for THz data-links

A fully integrated CMOS THz transmitter for short range data-links is presented which provides 0.47 mW of output power to 294 GHz. The output frequency is derived from a 147 GHz on-chip LO and fully differential caterpillar power amplifier combined with a transformer coupled frequency doubler. The transmitter is integrated with an on-chip dipole antenna for use in THz communication systems and consumes a total of 258 mW.

Chang, Mau-Chung Frank↗
NASA NTRS2022

Continental Patterns of Bird Migration Linked to Climate Variability

For nearly 100 years, avian migration studies have divided North America into three or four primary flyways, at times based on subjective approaches or just for convenience. Those studies often fail to adequately reflect a critical characterization of migration —phenology. This shortcoming has been partly due to the lack of reliable continental-scale data, a gap filled by our current study. Here, we leveraged unique radar-based data quantifying migration phenology and used an objective regionalization approach to revisit the traditional spatial framework. Consequently, we identified two regions with distinct inter annual variability of spring migration across the contiguous U.S. This new data-driven framework has enabled us to explore the climatic cues affecting the inter annual variability of migration phenology, “specific to each region” across North America. For example, our “two-region” approach allowed us to identify an east-west dipole pattern in migratory behavior linked to atmospheric Ross by waves. Also, we revealed a low-frequency variability in migration movements over the western U.S. that is inversely related with temperature and the Pacific Decadal Oscillation (PDO). Our spatial platform would facilitate future work on better understanding the mechanisms responsible for broad-scale migration phenology and its potential future changes.

Atmosphere↗
NASA NTRS2020

WISEA J083011.95+283716.0: A Missing Link Planetary-mass Object

We present the discovery of WISEA J083011.95+283716.0, the first Y-dwarf candidate identified through the “Backyard Worlds: Planet 9” citizen science project. We identified this object as a red, fast-moving source with a faint W2 detection in multiepoch AllWISE and unWISE images. We have characterized this object with Spitzer and Hubble Space Telescope’s (HST) follow-up imaging. With mid-infrared detections in Spitzerʼs ch1 and ch2 bands and flux upper limits in HST F105W and F125W filters, we find that this object is both very faint and has extremely red colors (ch1 − ch2 = 3.25 ± 0.23 mag, F125W− ch2 ≽ 9.36 mag), consistent with a T(sub eff) ∼ 300 K source, as estimated from the known Y-dwarf population. A preliminary parallax provides a distance of - 11.1+1.5 2.0 pc, leading to a slightly warmer temperature of ∼350 K. The extreme faintness and red HST and Spitzer colors of this object suggest that it may be a link between the broader Y-dwarf population and the coldest known brown dwarf WISE J0855−0714, and may highlight our limited knowledge of the true spread of Y-dwarf colors. We also present four additional “Backyard Worlds: Planet 9” late-T brown dwarf discoveries within 30 pc.

Brown dwarf↗
NASA NTRS2018

Linking Improvements in Sulfur Dioxide Emissions to Decreasing Sulfate Wet Deposition By Combining Satellite and Surface Observations With Trajectory Analysis

Sulfur dioxide (SO2), a criteria pollutant, and sulfate (SO42−) deposition are major environmental concerns in the eastern U.S. and both have been on the decline for two decades. In this study, we use satellite column SO2 data from the Ozone Monitoring Instrument (OMI), and SO42− wet deposition data from the NADP (National Atmospheric Deposition Program) to investigate the temporal and spatial relationship between trends in SO2 emissions and the downward sulfate wet deposition over the eastern U.S. from 2005 to 2015. To establish the relationship between SO2 emission sources and receptor sites, we conducted a Potential Source Contribution Function (PSCF) analysis using HYSPLIT back trajectories for five selected Air Quality System (AQS) sites - (Hackney, OH, Akron, OH, South Fayette, PA, Wilmington, DE, and Beltsville, MD) - in close proximity to NADP sites with large downward SO42− trends since 2005. Back trajectories were run for three summers (JJA) and three winters (DJF) and used to generate seasonal climatology PSCFs for each site. The OMI SO2 and interpolated NADP sulfate deposition trends were normalized and overlapped with the PSCF, to identify the areas that had the highest contribution to the observed drop. The results suggest that emission reductions along the Ohio River Valley have led to decreases in sulfate deposition in eastern OH and western PA (Hackney, Akron and South Fayette). Farther to the east, emission reductions in southeast PA resulted in improvements in sulfate deposition at Wilmington, DE, while for Beltsville, reductions in both the Ohio River Valley and nearby favorably impacted sulfate deposition. For Beltsville, sources closer than 300 km from the site contribute roughly 56% observed deposition trends in winter, and 82% in summer, reflecting seasonal changes in transport pattern as well as faster oxidation and washout of sulfur in summer. This suggests that emissions and wet deposition are linked through not only the location of sources relative to the observing sites, but also to photochemistry and the weather patterns characteristic to the region, as evidenced by a west to east shift in the contribution between winter and summer. The method developed here is applicable to other regions with significant trends such as China and India, and can be used to estimate the potential benefits of emission reduction in those areas.

sulfur dioxide emissions↗
NASA NTRSDate not supplied

Automated classification of scientific publications linked to GES DISC datasets

The data collections archived and distributedby the GES DISC NASA data center arewidely utilized for various Earth Science studies.As these collections are created, many researchworks are published regarding the collections, algorithms,validations and applications. SinceGES DISC collects these publications and providestheir citations for the users, it is helpful tocategorize them based on how they relate to the datasetsthey are associated with. Specifically,whether the publication that is linked to GES DISCdataset is using it for applicational research,or if it describes the algorithm for dataset creation,or the validation of the dataset, or providesthe general overview of the data collection. Currently,this process requires simple manuallabelling, and as such, may be possible to solve viaautomation. To approach this problem, wedeveloped machine learning classifiers to predictthe category a publication belongs to. We usedmanually labeled publications as training data forsupervised machine learning algorithms:Random Forest and Naive Bayes. We achieved classificationaccuracy that is substantially betterthan the baseline accuracy, thus greatly improvingthe efficiency of the publication internalanalysis.

Rohan Dayal↗