Search NASA⌕ Search

SEARCH · Search NASA

Results for “Spatial Characterization”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Arcjet Supplemental Diagnostics

This document proposes a new set of diagnostics designed to be implemented on the NASA Ames miniature Arcjet Research Chamber (mARC) for improved characterization of the flow. The diagnostics are grouped into three classes:higher cadence measurements, higher spatial resolution, and computer vision techniques for improved analysis of existing imaging. The goal is to better understand and quantify the following properties: flow statistics/uncertainty, temporal & spatial non-uniformity, flow temperature/enthalpy

Haw, Magnus A.↗
NASA NTRS2002

Far infrared interferometer technology development: a progress report

We report on the progress of developing a cryogenic delay line and integrated optics components. These are some of the critical components needed to enable farm, direct detection, interferometers. To achieve background limited performance in the 40 to 400 pm region, the interferometer optics and delay line must be cooled to near liquid Helium temperatures. The cryogenic delay line design incorporates a number of novel features and has been tested and characterized at liquid nitrogen temperatures. The integrated optics effort has focused on producing single mode spatial filters and beam combiners.

Interferometer↗
NASA NTRS1979

Spatial quantification of maps or images - Cell size or pixel size implications

The paper discusses spatial quantification of maps or images. Spatial accuracies evaluated by mapping and inventory measures were observed with a range of cell sizes for a 10.36 sq km soil survey segment. The distribution of interboundary distances in a map was evaluated as unique, characterizing information; experimentally observed relationships between accuracy and cell size and interboundary distance distribution parameters and cell size led to a model of the process of spatial quantization. Grid positioning effects were evaluated and were significant only at the level of individual mapping units; two generations of 'universal' process models were derived, implemented, and evaluated.

Wehde, M. E.↗
NASA NTRSDate not supplied

Aerothermodynamic Measurements in Hypersonic Non-Equilibrium Flows

High enthalpy arc-jets are unique facilities particularly suited for simulating complex flows in the aerospace field, such as the aerothermodynamics of a re-entry vehicle. Arc-jets are often used to evaluate important design factors such as heat shield materials and vehicle design. Characterization of these facilities is important, as studies often match specific in-flight environments during experiments. Due to the complex environment produced by an arc-jet, with effects such as thermodynamic and chemical non-equilibrium occurring in the flow, characterization experiments are significantly more difficult than in traditional blow-down wind tunnels. The current work aims to characterize an arc-jet facility in terms of flow temperature, velocity and unsteadiness, in a spatially-resolved analysis. To achieve this goal, a non-intrusive imaging technique called “planar laser-induced fluorescence” was performed in the NASA Langley Hypersonic Materials Environ-mental Test System arc-jet facility. The experimental data was analyzed to produce the quantitative measurements in multiple regions of the flow around a blunt body sample. A quasi-1D low fidelity solver was created to numerically simulate the flow to investigate non-equilibrium effects occur-ring outside the imaging region in the arc-jet nozzle. Unsteadiness in the test section was minimized by analyzing a subset of data assessing the gas injection location. Radial velocity, rotational temperature and translational temperature measurements are provided that can be used to validate future high-fidelity computational studies. The temperature measurements revealed rotational non-equilibrium potentially occurring in the flow. This work provides a methodology for characterizing arc-jet facilities, identifying and correcting sources of systematic error, and estimating the uncertainty associated with the quantitative measurements.

laser induced fluorescence↗
NASA NTRS2001

Characterization of the yeast copper-inducible promoter system in Arabidopsis thaliana

Inducible promoters or gene-switches are used to both spatially and temporally regulate gene expression. Such regulation can provide information concerning the function of a gene in a developmental context as well as avoid potential harmful effects due to overexpression. A gfp construct under the control of a copper-inducible promoter was introduced into Arabidopsis thaliana (L.) Heynh. and the regulatory parameters of this inducible promoter were determined. Here, we describe the time-course of up- and down-regulation of GFP expression in response to copper level, the optimal regulatory levels of copper, and the tissue specificity of expression in three transgenic lines. We conclude that the copper-inducible promoter system may be useful in regulating the time and location of gene expression in A. thaliana.

Non-NASA Center↗
NASA NTRS2013

Solutions of the Taylor-Green Vortex Problem Using High-Resolution Explicit Finite Difference Methods

A computational fluid dynamics code that solves the compressible Navier-Stokes equations was applied to the Taylor-Green vortex problem to examine the code s ability to accurately simulate the vortex decay and subsequent turbulence. The code, WRLES (Wave Resolving Large-Eddy Simulation), uses explicit central-differencing to compute the spatial derivatives and explicit Low Dispersion Runge-Kutta methods for the temporal discretization. The flow was first studied and characterized using Bogey & Bailley s 13-point dispersion relation preserving (DRP) scheme. The kinetic energy dissipation rate, computed both directly and from the enstrophy field, vorticity contours, and the energy spectra are examined. Results are in excellent agreement with a reference solution obtained using a spectral method and provide insight into computations of turbulent flows. In addition the following studies were performed: a comparison of 4th-, 8th-, 12th- and DRP spatial differencing schemes, the effect of the solution filtering on the results, the effect of large-eddy simulation sub-grid scale models, and the effect of high-order discretization of the viscous terms.

DeBonis, James R.↗
NASA NTRS1998

Characterization of Clouds and the Anisotropy of Emitted and Reflected Radiances for the Purpose of Obtaining the Radiative Heating of the Atmosphere

The goal of the work supported through this grant was to assess the validity of the assumptions underlying the CERES Strategy for determining radiative fluxes. Specifically, the work focused on the determination of scene type and the use of anisotropic factors to derive radiative fluxes from observed broadband radiances. The work revealed a dependence of the anisotropy of reflected and emitted broadband radiances on the spatial resolution of the observations that had been overlooked in the formulation of the CERES strategy. This dependence on spatial resolution coupled with errors in scene identification led to view zenith angle dependent biases in the ERBE derived radiative fluxes. Scene identification will be greatly improved in CERES thereby alleviating somewhat the biases arising from the dependence of the anisotropy of the radiances on spatial resolution. Attention was then focused on the validity of plane-parallel radiative transfer theory which is relied on to characterize the scene types viewed by the CERES scanner. Again, viewing geometry dependent biases were found even for single-layered, overcast cloud systems. Such systems are taken to be the closest examples of plane-parallel clouds. At least some of the departures from plane-parallel behavior were evidently due to relatively small bumps on the tops of extensive stratus layers. The bumps cannot be resolved in the imagery that will be used to characterize the scenes viewed by the CERES scanner. As part of this investigation, the ice sheets of Greenland and Antarctica were shown to provide radiometrically stable targets for determining the visible and near infrared calibrations of radiometers. These targets were used to calibrate the reflected sunlight at visible wavelengths used in this study. Finally, the limitations of plane-parallel theory notwithstanding, the common practice of ignoring fractional cloud cover within the fields of view of imaging radiometers was shown to lead to biases in the retrieved cloud properties. The development of retrievals for pixel-scale cloud cover fraction is an attempt to reduce such bases. Work on these retrievals continues.

Coakley, James A., Jr.↗
NASA NTRS2007

Simulation Studies of Forest Structure using 3D Lidar and Radar Models

The use of lidars and radars to measure forest structure attributes such as height and biomass are being considered for future Earth Observation missions. Large footprint lidar makes a direct measurement of the heights of scatterers in the illuminated footprint and can yield information about the vertical profile of the canopy. Synthetic Aperture Radar (SAR) is known to sense the canopy volume, especially at longer wavelengths and is useful for estimating biomass. Interferometric SAR (InSAR) has been shown to yield forest canopy height information. For example, the height of scattering phase retrieved from InSAR data is considered to be correlated with the three height and the spatial structure of the forest stand. There is much interest in exploiting these technologies separately and together to get important information for carbon cycle and ecosystem science. More detailed information of the electromagnetic radiation interactions within forest canopies is needed. And backscattering models can be of much utility here. As part of a NASA funded project to explore data fusion, a three-dimensional (3D) coherent radar backscattering model and a 3D lidar backscatter models were used to investigate the use of large footprint lidar, SAR and InSAR for characterizing realistic forest scenes. For this paper, we use stem maps and other forest measurements to develop a realistic spatial structure of a spruce-hemlock forest canopy found in Maine, USA. The radar and lidar models used measurements of the 3D forest scene as input and simulated the coherent radar backscattering signature and 1064nm energy backscatter, respectively. The relationships of backscatter derived forest structure were compared with field measurements. In addition, we also had detailed airborne lidar (Laser Imaging Vegetation Sensor, LVIS) data available over the stem map sites that was used to study the accuracies of tree height derived from modeled SAR backscatter and the scattering phase center retrieved from the simulated InSAR data will be compared with the height indices, or other structure parameters derived from the lidar data. These results will address the possible synergies between lidar and radar in data in terms of forest structural information.

Sun, Guoqing↗
NASA NTRS2010

Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 sq. km, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as possible sites for near-continuous sources of solar power.

E. Mazarico↗
NASA NTRS2000

Early Instrument Performance Results from the Terra/Moderate Resolution Imaging Spectroradiometer (MODIS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) is a major observational capability flying on the Earth Observing System (EOS) AM-1 "Terra" mission. This mission is to go into orbit in late 1999 or very early 2000. The MODIS was developed to provide improved observations of land, ocean, and atmosphere features relative to "heritage instruments" such as the NOAA Advanced Very High Resolution Radiometer (AVHRR), the Nimbus Coastal Zone Color Scanner (CZCS)and the SeaStar/SeaWiFS instruments, in particular. In addition the MODIS should provide complementary observations to the Landsat-7 Thematic Mapper and the NOAA HIRS instrument. There has been considerable effort to include capabilities or plans to characterize and assure calibration of the instrument data. These efforts include on on-board blackbody (BB), a solar diffuser (SID), a solar diffuser stability monitor (SDSM), and a spectral radiometric calibration assembly (SDSM). These devices, along with careful analyses of scenes acquired during orbit, are expected to allow comparisons with pre-launch expectations regarding spatial performance, spectral performance, and radiometric performance. In addition deep space observations and observations of the moon are to be used to characterize instrument performance. The purpose of this paper is to provide quantitative comparisons, as results become available from the Terra MODIS, to heritage instruments, pre-launch expectations and specifications.

Salomonson, V. V.↗
NASA NTRS2004

Landcover Based Optimal Deconvolution of PALS L-band Microwave Brightness Temperature

An optimal de-convolution (ODC) technique has been developed to estimate microwave brightness temperatures of agricultural fields using microwave radiometer observations. The technique is applied to airborne measurements taken by the Passive and Active L and S band (PALS) sensor in Iowa during Soil Moisture Experiments in 2002 (SMEX02). Agricultural fields in the study area were predominantly soybeans and corn. The brightness temperatures of corn and soybeans were observed to be significantly different because of large differences in vegetation biomass. PALS observations have significant over-sampling; observations were made about 100 m apart and the sensor footprint extends to about 400 m. Conventionally, observations of this type are averaged to produce smooth spatial data fields of brightness temperatures. However, the conventional approach is in contrast to reality in which the brightness temperatures are in fact strongly dependent on landcover, which is characterized by sharp boundaries. In this study, we mathematically de-convolve the observations into brightness temperature at the field scale (500-800m) using the sensor antenna response function. The result is more accurate spatial representation of field-scale brightness temperatures, which may in turn lead to more accurate soil moisture retrieval.

Limaye, Ashutosh S.↗
NASA NTRS1997

Characterization and Demonstrations of Laser-Induced Incandescence in both Normal and Low-Gravity

Knowledge of soot volume fraction is important to a wide range of combustion studies in microgravity. Laser-induced incandescence (LII) offers high sensitivity, high temporal and spatial resolution in addition to geometric versatility for real-time determination of soot volume fraction. Implementation of LII into the 2.2 see drop tower at The NASA-Lewis Research Center along with system characterization is described. Absolute soot volume fraction measurements are presented for laminar and turbulent gas-jet flames in microgravity to illustrate the capabilities of LII in microgravity. Comparison between LII radial intensity profiles with soot volume fraction profiles determined through a full-field light extinction technique are also reported validating the accuracy of LII for soot volume fraction measurements in a microgravity environment.

VanderWal, Randall L.↗
NASA NTRS1978

Inversion of data from diffraction-limited multiwavelength remote sensors. I - Linear case

The remote sensing inverse problem is considered in which the sensor does not necessarily view the same area on the earth at each wavelength, and spatial correlations of the geophysical parameters may be present. Under the conditions of linearity and stationary statistics, the minimum mean-square error solution to the problem of inverting such data is a spatial filter of the Wiener-Kolmogorov class. The resulting remote-sensing system can be characterized by an impulse response matrix in ordinary space or by a transfer matrix in frequency space. A signal-to-noise matrix for the geophysical parameters to be sensed is also defined; this matrix depends on the postulated a priori statistics and on the characteristics of the remote-sensing instrument. The system transfer matrix and the signal-to-noise matrix are simultaneously diagonalizable. The optimum transfer matrix filters out of the estimate vector those eigenparameters for which eigenvalues of the signal-to-noise matrix are less than unity.

Rosenkranz, P. W.↗
NASA NTRS1998

Multi-Scale Fractal Analysis of Image Texture and Pattern

Fractals embody important ideas of self-similarity, in which the spatial behavior or appearance of a system is largely independent of scale. Self-similarity is defined as a property of curves or surfaces where each part is indistinguishable from the whole, or where the form of the curve or surface is invariant with respect to scale. An ideal fractal (or monofractal) curve or surface has a constant dimension over all scales, although it may not be an integer value. This is in contrast to Euclidean or topological dimensions, where discrete one, two, and three dimensions describe curves, planes, and volumes. Theoretically, if the digital numbers of a remotely sensed image resemble an ideal fractal surface, then due to the self-similarity property, the fractal dimension of the image will not vary with scale and resolution. However, most geographical phenomena are not strictly self-similar at all scales, but they can often be modeled by a stochastic fractal in which the scaling and self-similarity properties of the fractal have inexact patterns that can be described by statistics. Stochastic fractal sets relax the monofractal self-similarity assumption and measure many scales and resolutions in order to represent the varying form of a phenomenon as a function of local variables across space. In image interpretation, pattern is defined as the overall spatial form of related features, and the repetition of certain forms is a characteristic pattern found in many cultural objects and some natural features. Texture is the visual impression of coarseness or smoothness caused by the variability or uniformity of image tone or color. A potential use of fractals concerns the analysis of image texture. In these situations it is commonly observed that the degree of roughness or inexactness in an image or surface is a function of scale and not of experimental technique. The fractal dimension of remote sensing data could yield quantitative insight on the spatial complexity and information content contained within these data. A software package known as the Image Characterization and Modeling System (ICAMS) was used to explore how fractal dimension is related to surface texture and pattern. The ICAMS software was verified using simulated images of ideal fractal surfaces with specified dimensions. The fractal dimension for areas of homogeneous land cover in the vicinity of Huntsville, Alabama was measured to investigate the relationship between texture and resolution for different land covers.

Emerson, Charles W.↗
NASA NTRS2004

USGS and NASA Digital Imagery Product Characterization

This paper presents viewgraphs about a partnership between USGS and NASA who are jointly developing an airborne digital imagery characterization capability. The topics include: 1) USGS-NASA Product Characterization Approach; 2) Stennis Character Range; 3) Stennis Geodetic Targets; 4) Stennis Manhole Covers; 5) Stennis Edge Target; 6) Stennis Characterization Site; 7) Delivered Data; 8) Other Data Considerations; 9) Status; 10) Geopositional Assessment Approach; 11) Spatial Assessment Approach; 12) Edge Response; and 13) Results to Date.

Zanoni, Vicki↗
NASA NTRS2005

A GeoSTAR progress report

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new concept for a microwave sounder, intended to be deployed on NOAA's next generation of geostationary weather satellites, GOES-R. A ground based prototype has been developed at the Jet Propulsion Laboratory, under NASA Instrument Incubator Program sponsorship, and is now undergoing tests and performance characterization. With the aperture synthesis approach used by GeoSTAR it is possible to achieve very high spatial resolutions even in the crucial 50-GHz temperature sounding band without having to deploy the impractically large parabolic reflector antenna that is required with the conventional approach. The technology and system design required for GeoSTAR are rapidly maturing, and it is expected that a space demonstration mission can be developed before the first GOES-R launch. GeoSTAR will be ready for operational deployment 2-3 years after that. The prototype developed under IIP implements a small version of the temperature sounding component of GeoSTAR, is fully functional as a sounder and has all of the features and capabilities of an operational system with the exception of spatial resolution. It therefore represents a complete proof of concept as well as significant risk reduction for a space implementation.

microwaves↗
NASA NTRS2015

Noise Characteristics of a Four-Jet Impingement Device Inside a Broadband Engine Noise Simulator

The noise generation mechanisms for four directly impinging supersonic jets are investigated employing implicit large eddy simulations with a higher-order accurate weighted essentially non-oscillatory shock-capturing scheme. Impinging jet devices are often used as an experimental apparatus to emulate a broadband noise source. Although such devices have been used in many experiments, a detailed investigation of the noise generation mechanisms has not been conducted before. Thus, the underlying physical mechanisms that are responsible for the generation of sound waves are not well understood. The flow field is highly complex and contains a wide range of temporal and spatial scales relevant for noise generation. Proper orthogonal decomposition of the flow field is utilized to characterize the unsteady nature of the flow field involving unsteady shock oscillations, large coherent turbulent flow structures, and the sporadic appearance of vortex tubes in the center of the impingement region. The causality method based on Lighthill's acoustic analogy is applied to link fluctuations of flow quantities inside the source region to the acoustic pressure in the far field. It will be demonstrated that the entropy fluctuation term in the Lighthill's stress tensor plays a vital role in the noise generation process. Consequently, the understanding of the noise generation mechanisms is employed to develop a reduced-order linear acoustic model of the four-jet impingement device. Finally, three linear acoustic FJID models are used as broadband noise sources inside an engine nacelle and the acoustic scattering results are validated against far-field acoustic experimental data.

Broadband↗
NASA NTRSDate not supplied

Springtime SEA Air Is Consistently Both Smoky and Humid, but This Relationship (and Its Radiative Effects) Varies Spatially and Seasonally

The atmosphere over the southeast Atlantic Ocean (SEA) sees a consistent springtime biomass burning (BB) smoke from widespread agricultural fires on the African continent. This smoke layer is initially lofted high in a continental mixed layer (~5-6km) and is then transported westward in the free troposphere, where it overlies and ultimately mixes into the SEA stratocumulus-topped oceanic boundary layer. Coincident with this smoke is an elevated humidity signal which is present from the time a given airmass is over the continental source region. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) was a NASA Earth Venture Suborbital mission with the goal of measuring aerosol, cloud, and atmospheric properties over this region during three deployments in September 2016, August 2017, and October 2018. A previous study discussed the spatial characteristics of the water vapor-BB plume observations in the September 2016 flight data and their degree of agreement with several atmospheric reanalyses and models. In the present work, we first discuss atmospheric chemistry, structure, and aerosol results from all three ORACLES deployments to place these results in a broader seasonal context. Despite the differing locations and season of each deployment, we show that there continues to be good agreement between the airborne ORACLES dataset and large-scale reanalyses, specifically the ECMWF ERA5 and CAMS reanalyses. Other reanalyses (specifically NASA's MERRA-2) preserved the observed correlation between meteorology and biomass burning conditions, but, as was seen for 2016, was frequently displaced spatially relative to the observations. The CAMS reanalysis performs better with water vapor than with CO. Results comparing CAMS column AOD to the field measurements show slight overestimates, consistent with previous analysis, but the good relationship observed between AOD and inlet-based aerosol extinction demonstrates this metric's utility to broader studies. The good ERA5/CAMS/ORACLES agreement allows us to next examine the multi-year seasonal patterns and trends beyond the three ORACLES deployment periods. Looking at seven years of reanalysis data for the BB season, we find distinct variations between each month/deployment in terms of vertical smoke distribution and correlation to atmospheric specific humidity, due to changing conditions through the BB season. Using k-means clustering of these climatological reanalysis, we identify six canonical atmospheric profile types of varying total atmospheric humidity and vertical structure and describe their changing incidence spatially and throughout the season, and six analogous profile types for carbon monoxide, allowing us to characterize the atmospheric structure of both vapor and BB over time throughout the SEA region. This classification will allow for a more complete analysis of the broader radiative and dynamical effects of humid aerosols overlying stratocumulus clouds.

Kristina Marie Myers Pistone↗