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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Evaluation of GIS Technology in Assessing and Modeling Land Management Practices

There is an increasing concern of land owners to protect and maintain healthy and sustainable agroecosystems through the implementation of best management practices (BMP). The objectives of this study were: (1) To develop and evaluate the use of a Geographic Information System (GIS) technology for enhancing field-scale management practices; (2) evaluate the use of 2-dimensional displays of the landscape and (3) define spatial classes of variables from interpretation of geostatistical parameters. Soil samples were collected to a depth of 2 m at 15 cm increments. Existing data from topographic, land use, and soil survey maps of the Winfred Thomas Agricultural Research Station were converted to digital format. Additional soils data which included texture, pH, and organic matter were also generated. The digitized parameters were used to create a multilayered field-scale GIS. Two dimensional (2-D) displays of the parameters were generated using the ARC/INFO software. The spatial distribution of the parameters evaluated in both fields were similar which could be attributed to the similarity in vegetation and surface elevation. The ratio of the nugget to total semivariance, expressed as a percentage, was used to assess the degree of spatial variability. The results indicated that most of the parameters were moderate spatially dependent Biophysical constraint maps were generated from the database layers, and used in multiple combination to visualize results of the BMP. Understanding the spatial relationships of physical and chemical parameters that exists within a field should enable land managers to more effectively implement BMP to ensure a safe and sustainable environment.

Archer, F.↗
NASA NTRS2004

The Southern Hemisphere Additional Ozonesondes (SHADOZ) 1998-2002 Tropical Ozone Climatology: Instrumentation and Station-to-Station Variability - 3

Abstract: Since 1998 the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has collected more than 2000 ozone profiles from a dozen tropical and subtropical sites using balloon-borne electrochemical concentration cell (ECC) ozonesondes. The data (with accompanying pressure-temperature-humidity soundings) are archived. Analysis of ozonesonde imprecision within the SHADOZ dataset revealed that variations in ozonesonde technique could lead to station-to-station biases in the measurements. In this paper imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. When SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release), discrepancies between sonde and satellite datasets decline 1-2 percentage points on average, compared to version 7 TOMS. Variability among stations is evaluated using total ozone normalized to TOMS and results of laboratory tests on ozonesondes (JOSE-2O00, Julich Ozonesonde Intercomparison Experiment). Ozone deviations from a standard instrument in the JOSE flight simulation chamber resemble those of SHADOZ station data relative to a SHADOZ-defined climatological reference. Certain systematic variations in SHADOZ ozone profiles are accounted for by differences in solution composition, data processing and instrument (manufacturer). Instrument bias leads to a greater ozone measurement above 25 km over Nairobi and to lower total column ozone at three Pacific sites compared to other SHADOZ stations at 0-20 deg.S.

Thompson, Anne M.↗
NASA NTRS2001

Improving Simulated Annealing by Replacing Its Variables with Game-Theoretic Utility Maximizers

The game-theory field of Collective INtelligence (COIN) concerns the design of computer-based players engaged in a non-cooperative game so that as those players pursue their self-interests, a pre-specified global goal for the collective computational system is achieved as a side-effect. Previous implementations of COIN algorithms have outperformed conventional techniques by up to several orders of magnitude, on domains ranging from telecommunications control to optimization in congestion problems. Recent mathematical developments have revealed that these previously developed algorithms were based on only two of the three factors determining performance. Consideration of only the third factor would instead lead to conventional optimization techniques like simulated annealing that have little to do with non-cooperative games. In this paper we present an algorithm based on all three terms at once. This algorithm can be viewed as a way to modify simulated annealing by recasting it as a non-cooperative game, with each variable replaced by a player. This recasting allows us to leverage the intelligent behavior of the individual players to substantially improve the exploration step of the simulated annealing. Experiments are presented demonstrating that this recasting significantly improves simulated annealing for a model of an economic process run over an underlying small-worlds topology. Furthermore, these experiments reveal novel small-worlds phenomena, and highlight the shortcomings of conventional mechanism design in bounded rationality domains.

Wolpert, David H.↗
NASA NTRS2022

Mapping Firn Saturation over Greenland using NASA’s Soil Moisture Active Passive Satellite

Mapping the spatial extent of recently identified englacial hydrological features (i.e., ice slabs and perennial firn aquifers) formed by meters-thick water-saturated firn layers over the percolation facies of the Greenland Ice Sheet using L-band microwave radiometry has recently been demonstrated. However, these initial maps are binary, and do not provide a parameter to estimate the spatial variability in the thickness and volumetric fraction of meltwater stored within the firn pore space. Here, we exploit enhanced-resolution vertical-polarization L-band brightness temperature (T^(B)_(V)) imagery (2015–2019) generated using observations collected over Greenland by NASA’s Soil Moisture Active Passive (SMAP) satellite and a simple two-layer L-band brightness temperature model. We map water-saturated firn layers via a “firn saturation” parameter, and interpret our results together with ice slab and perennial firn aquifer spatial extents, estimates of snow accumulation simulated via the Regional Atmospheric Climate Model (RACMOp2.3), and airborne radar surveys collected via NASA’s Operation IceBridge (OIB) campaigns. We find that variable firn saturation parameter values are mapped in lower snow accumulation ice slab areas in western, northern, and northeastern Greenland, where firn is colder and water-saturated firn layers seasonally refreeze as solid-ice. Higher firn saturation parameter values are mapped in higher snow accumulation perennial firn aquifer areas in southeastern, southern, and northwestern Greenland, where firn is near the melting point, and meters-thick water-saturated firn layers exist. Our results have implications for identifying expansive englacial reservoirs that store significant volumes of meltwater in locations that are vulnerable to meltwater-induced hydrofracturing and accelerated outlet glacier flow year-round.

Greenland ice sheet↗
NASA NTRS1990

The radiation budget of a Cirrus layer deduced from simultaneous aircraft observations and model calculations

Several aircraft were employed during the FIRE Cirrus IFO in order to make nearly simultaneous observations of cloud properties and fluxes. A segment of the flight data collected on 28 October 1988 during which the NASA Ames ER-2 overflew the NCAR King Air was analyzed. The ER-2 flew at high altitude making observations of visible and infrared radiances and infrared flux and cloud height and thickness. During this segment, the King Air flew just above the cloud base making observations of ice crystal size and shape, local meteorological variables, and infrared fluxes. While the two aircraft did not collect data exactly coincident in space and time, they did make observations within a few minutes of each other. For this case study, the infrared radiation balance of the cirrus layer is of primary concern. Observations of the upwelling 10 micron radiance, made from the ER-2, can be used to deduce the 10 micron optical depth of the layer. The upwelling broadband infrared flux is also measured from the ER-2. At the same time, the upwelling and downwelling infrared flux at the cloud base is obtained from the King Air measurements. Information on cloud microphysics is also available from the King Air. Using this data in conjunction with atmospheric temperature and humidity profiles from local radiosondes, the necessary inputs for an infrared radiative transfer model can be developed. Infrared radiative transfer calculations are performed with a multispectral two-stream model. The model fluxes at the cloud base and at 19 km are then compared with the aircraft observations to determine whether the model is performing well. Cloud layer heating rates can then be computed from the radiation exchange.

Ackerman, Thomas P.↗
NASA NTRS2023

Mobile Observations of Ozone and Aerosols in Alabama: Southeastern US Summer Pollution and Coastal Variability

We present a detailed analysis of measurements of ozone (O 3 ) and aerosols collected using multiple platforms and instruments during a 5-day mini-campaign in Alabama, for improving our understanding of the chemistry and air quality in the Southeastern United States. Our study features the first on-road O 3 lidar profiling on highways and the coordinated airborne observations that captured O 3 and aerosol structures associated with synoptic weather conditions, stratospheric intrusions, wildfire smoke transport, and enhancements in urban areas. The Doppler wind lidar data suggest that the vertical structures and variability of O 3 and aerosols at Dauphin Island, a coastal site in the Gulf of Mexico, were related to both the synoptic flow and local-scale land-sea breeze circulation. The onshore gulf breeze, which typically started in the afternoon, helped to quickly dilute air pollutants near the surface, resulting in large gradients toward inland areas. In contrast, gradients were much smaller on days without a gulf breeze. O 3 and humidity were highly anti-correlated in the lower free troposphere, but weakly anti-correlated in the planetary boundary layer (PBL) suggesting more complicated emissions and sink of O 3 in the PBL. Our on-road and airborne measurement strategies to quantify the vertical and horizontal chemical gradients will be useful for future geostationary satellite validation.

Shi Kuang↗
NASA NTRS1998

Predicting Ecologically Important Vegetation Variables from Remotely Sensed Optical/Radar Data Using Neural Networks

A number of satellite sensor systems will collect large data sets of the Earth's surface during NASA's Earth Observing System (EOS) era. Efforts are being made to develop efficient algorithms that can incorporate a wide variety of spectral data and ancillary data in order to extract vegetation variables required for global and regional studies of ecosystem processes, biosphere-atmosphere interactions, and carbon dynamics. These variables are, for the most part, continuous (e.g. biomass, leaf area index, fraction of vegetation cover, vegetation height, vegetation age, spectral albedo, absorbed photosynthetic active radiation, photosynthetic efficiency, etc.) and estimates may be made using remotely sensed data (e.g. nadir and directional optical wavelengths, multifrequency radar backscatter) and any other readily available ancillary data (e.g., topography, sun angle, ground data, etc.). Using these types of data, neural networks can: 1) provide accurate initial models for extracting vegetation variables when an adequate amount of data is available; 2) provide a performance standard for evaluating existing physically-based models; 3) invert multivariate, physically based models; 4) in a variable selection process, identify those independent variables which best infer the vegetation variable(s) of interest; and 5) incorporate new data sources that would be difficult or impossible to use with conventional techniques. In addition, neural networks employ a more powerful and adaptive nonlinear equation form as compared to traditional linear, index transformations, and simple nonlinear analyses. These neural networks attributes are discussed in the context of the authors' investigations of extracting vegetation variables of ecological interest.

Kimes, Daniel S.↗
NASA NTRS2007

Safety Performance of Airborne Separation: Preliminary Baseline Testing

The Safety Performance of Airborne Separation (SPAS) study is a suite of Monte Carlo simulation experiments designed to analyze and quantify safety behavior of airborne separation. This paper presents results of preliminary baseline testing. The preliminary baseline scenario is designed to be very challenging, consisting of randomized routes in generic high-density airspace in which all aircraft are constrained to the same flight level. Sustained traffic density is varied from approximately 3 to 15 aircraft per 10,000 square miles, approximating up to about 5 times today s traffic density in a typical sector. Research at high traffic densities and at multiple flight levels are planned within the next two years. Basic safety metrics for aircraft separation are collected and analyzed. During the progression of experiments, various errors, uncertainties, delays, and other variables potentially impacting system safety will be incrementally introduced to analyze the effect on safety of the individual factors as well as their interaction and collective effect. In this paper we report the results of the first experiment that addresses the preliminary baseline condition tested over a range of traffic densities. Early results at five times the typical traffic density in today s NAS indicate that, under the assumptions of this study, airborne separation can be safely performed. In addition, we report on initial observations from an exploration of four additional factors tested at a single traffic density: broadcast surveillance signal interference, extent of intent sharing, pilot delay, and wind prediction error.

Consiglio, Maria C.↗
NASA NTRS1973

Components for solar energy

A requirement for the direct technological utilization of solar energy is a device for capturing and absorbing the available sunlight. These devices are commonly termed collectors. Because of the highly variable nature of sunlight, a facility for storing the collected energy is often essential. A device for direct conversion of light into electricity, which depends for operation on incident sunlight, is the photovoltaic cell. These components for solar energy systems are considered.

Source record↗
NASA NTRS1982

X-ray and optical measurements of the cataclysmic variable CH UMa

A program to identify optical counterparts of X-ray sources discovered with the Einstein Observatory has resulted in an independent identification of CH UMa as a cataclysmic variable. Spectrophotometric observations made with the Intensified Image Dissector Scanner on the 2.1-m telescope at KPNO revealed an emission line spectrum from an approximately 15 mag object similar to the spectra of cataclysmic variables. A subsequent search of the Harvard photographic plate collection revealed outbursts of 4 mag in amplitude.

Becker, R. H.↗
NASA NTRS1992

In-flight radiometry of an airborne multispectral sensor

The in-flight radiometric behavior of the NS001 Landsat Thematic Mapper simulator is being reexamined. The absolute radiometric calibration and polarization sensitivity are being analyzed based on data collected in 1990 and 1991. The NS001 has continuously variable gain settings controlled by the aircraft operator. As such, the of in-flight calibration source, an integrating sphere in the solar reflective spectrum, is the only means for calibrating this instrument. Upgrades to the power supply and monitoring circuitry in 1990 improved the in-flight stability. Preliminary results in-flight calibrations of the NS001 indicate no improvement in radiometric accuracy. Laboratory tests have also shown that the NS001 shows strong sensitivity to the degree of polarization and state of the incoming radiations. Simulation studies for typical in-flight conditions have shown that for the NS001 scanning in the principal plane of the sun over a vegetated target, radiance errors reached +/-10 percent in the 0.45-0.52-micron channel and varied with scan angle.

Markham, Brian L.↗
NASA NTRS1949

Summary of section data on trailing-edge high-lift devices

A summary has been made of available data on the characteristics of airfoil sections with trailing-edge high-lift devices. Data for plain, split, and slotted flaps are collected and analyzed. The effects of each of the variables involved in the design of the various types of flap are examined and, in cases where sufficient data are given, optimum configurations are deduced. Wherever possible, the effects of airfoil section, Reynolds number, and leading-edge roughness are shown. For single and double slotted flaps, where a large amount of unrelated data are available, maximum lift coefficients of many configurations are presented in tables.

Cahill, Jones F↗
NASA NTRS1997

Monitoring of the effects of fire in North American boreal forests using ERS SAR imagery

ERS synthetic aperture radar (SAR) imagery represents a tool for monitoring the effects of fires in boreal regions. Fire-scar signatures from ERS SAR collected over Canada and Alaska are presented. The temporal variability exhibited throughout the growing season is underlined. The investigation showed that these signatures have a seasonal trend related to the patterns of soil moisture originating from snow melts in the spring and precipitation during the growing season. These signatures appear in all the regions of the North American boreal forest and remain visible for up to 13 years after a fire.

Kasischke, E. S.↗
NASA NTRS1998

Compositional Variation in Lunar Regolith Samples: Lateral

The composition of samples of lunar regolith collected on the Apollo and Luna missions are highly variable; the lunar meteorites, most of which are breccias of lithified regolith from unknown locations on the Moon, extend the compositional range. Some aspects of regolith composition as inferred from studies of samples that are relevant for interpretation of data obtained remotely are discussed.

Korotev, Randy L.↗
NASA NTRS1948

Summary of Section Data on Trailing-Edge High-Lift Devices

A summary has been made of available data on the characteristics of airfoil sections with trailing-edge high-lift devices. Data for plain, split, and slotted flaps are collected and analyzed. The effects of each of the variables involved in the design of the various types of flap are examined and, in cases where sufficient data are given, optimum configurations are deduced. Wherever possible, the effects of airfoil section, Reynolds number, and leading-edge roughness are shown. For single and double slotted flaps, where a great mass of unrelated date are available, maximum lift coefficients of a large number of configurations are presented in tables.

Source record↗
NASA NTRS2023

PACE Technical Report Series, Volume 11: The PACE Postlaunch Airborne eXperiment (PACE-PAX)

The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE; https://pace.gsfc.nasa.gov) mission is NASA's latest and greatest effort to study the ocean-atmosphere system and build upon the legacy of previous satellite missions that have revolutionized our understanding of our home planet. By using advanced radiometric and polarimetric instruments to measure ocean color and key atmospheric variables, PACE aims to provide new insights into the complex interactions between the ocean, atmosphere, and biosphere. This information will be critical for improving our ability to model and predict changes in the Earth's climate, as well as to manage and conserve our planet's valuable natural resources. Performance assessments and science data product validation is a critical process for any Earth Science space-borne mission, as it involves assessing and verifying the quality of the data products generated by the mission while it is in orbit, as well as assigning uncertainties to these retrievals. More specifically, validation efforts are essential for assessing the accuracy of instrument data and the derived science products across varied spatial and temporal scales and ensuring their reliability and consistency with the mission's scientific goals and objectives. The overall plan for validation of PACE data is described in “PACE Science Data Product Validation Plan” (see, e.g., https://pace.gsfc.nasa.gov), and among range of post-launch activities, it describes the need and requirements for a post-launch airborne field campaign in support of PACE validation. This volume outlines the plans and requirements of the PACE Postlaunch Airborne eXperiment (PACE-PAX). The main goal of PACE-PAX is to gather validation and assessment data for the PACE mission, using a variety of airborne and ground-based assets. These assets will be coordinated to obtain complementary measurements of key ocean and atmospheric variables, such as ocean color, aerosols, and clouds. By collecting data from multiple sources, PACE-PAX will help to validate and refine the data products generated by the PACE mission, as well as to identify any potential errors or biases in the measurements. This will be essential for ensuring the accuracy and reliability of the PACE data products, and for maximizing the scientific value of the mission.

Kirk D Knobelspiesse↗
NASA NTRS1986

Electrostatic charging of electrically active spacecraft

A model is presented which predicts the temporal behavior of the ionospheric charging of spacecraft which eject energetic positive ions. The dynamic interaction of the spacecraft with the space-plasma environment is modelled as an equivalent electrical circuit consisting of a variable capacitor in parallel with two current sources. The spacecraft/space-plasma sheath is modelled as a variable capacitor containing positive-ion space charge. The ejection of energetic positive ions from the spacecraft represents a current source which charges the capacitor. Return current collected from the space-plasma sheath to the spacecraft is modelled as a variable current source which discharges the capacitor. The model can predict the temporal behavior of sheath movement, spacecraft potential, and space-plasma return current for a wide range of altitude, duty cycle, and ejected positive-ion current. Experimentally measured charging results, obtained for the Satellite Positive Ion Beam System (SPIBS) rocket flight, are accurately predicted by the model. Anticipated vehicle charging levels are presented for neutral-particle-beam platforms operating with a net, unneutralized, positive-ion-current component present in the emitted neutral-particle beam.

Matossian, J. N.↗
NASA NTRSDate not supplied

Evolution of the Next Exploration Toilet through Human-in-the-Loop (HITL) Testing

Human waste collection in space is a unique and necessary function that all crewmembers must perform. The variability in how each crewmember uses the toilet to urinate and defecate introduces complexities and challenges with regards to overall hardware design. Because of this variability, it is important to consider crew inputs in all aspects of a toilet design especially with regards to crew interfaces that could impact overall waste collection. Access to crew feedback is essential to the design process and should be considered early and often through the various design phases. In 2020, NASA started a project for the Human Landing System (HLS) program to develop a Government Furnished Equipment (GFE) toilet option. The project is known as the Lavatory On-Orbit (LOO). During the early development of the LOO, the project team conducted several crew evaluations to collect and summarize valuable crew feedback on system design, function, and overall usability to influence the next design iteration. Because every person could use the system differently in space, it was extremely important to collect and analyze the data in a very methodical manner to appropriately influence the design based on the evaluation results. Establishing a standard process ensures consistent data collection from one evaluation to another, helps to maintain privacy for each test subject’s inputs and removes any potential bias from test subject to test subject. To date, the team has completed four crew evaluations on prototypes for the different LOO hardware. This paper will summarize the methodology used to conduct the evaluations as well as how data was collected and analyzed. The paper will also provide details on each of the evaluations and how the design was updated based on the results.

toilet↗