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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

PSF Estimation in Crowded Astronomical Imagery as a Convolutional Dictionary Learning Problem

In this paper, we present a new algorithm for estimating the Point Spread Function (PSF) in wide-field astronomical images with extreme source crowding. Robust and accurate PSF estimation in crowded astronomical images dramatically improves the fidelity of astrometric and photometric measurements extracted from wide-field sky monitoring imagery. Our radically new approach utilizes convolutional sparse representations to model the continuous functions involved in the image formation. This approach avoids the need to detect and precisely localize individual point sources that is shared by existing methods. In experiments involving simulated astronomical imagery, it significantly outperforms the recent alternative method with which it is compared.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Curvilinear Aperture Monopulse

By a symmetry argument, a synthetic aperture radar collection along a linear path does not collect three-dimensional information about the scene. However, it is known that vertical curvature can be used to derive some vertical position information. This paper approaches the problem from a monopulse perspective, resulting in a non-iterative computation that commutes with efficient image formation algorithms.

Story, Mark↗
DOE OSTI2022

VotE-Dams: a compilation of global dams' locations and attributes (v1)

This dataset represents a compilation of two global and three USA-specific datasets of dam locations and their attributes. The major hurdle toward developing this compilation was the identification of duplicates within the source datasets, especially given the variable precision of dam location coordinates. The most immediately-useful product in this dataset is a spreadsheet (VotE-Dams_v1.csv) that documents the unique dams found across the datasets, their coordinates, and their ids within the respective source datasets. We do not reproduce the source datasets (GRaND, GOODD, GeoDAR, NID, and EHA) here, but their download locations are provided in the README files ('Overview' tab). Some of the source datasets are provided as shapefiles, which require geospatial data software to open (e.g. QGIS/ArcGIS for graphical display, geopandas for Python, rgdal for R, many others freely available). The provided README documents metadata of the source datasets and provides attribute-linking information (i.e. matches attributes among various source datasets that contain the same, or similar, information but have different names). Note that the README is provided as both .xslx and a collection of .csvs (one per tab in the .xslx file). We suggest using the .xlsx version that preserves images, formatting, and sheets. .xlsx files can be viewed using (free) Google Docs or Microsoft Excel.Finally, we provide Technical Documentation.pdf that describes the procedures used to identify unique and duplicate dams.The title of this dataset refers to our 'Veins of the Earth' (VotE) project, which seeks to provide a flexible, scale-free representation of the Earth's river networks. Dams are a critical component of VotE as they heavily influence flows throughout river networks.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Spotlight SAR Data Collection Geometry from ECEF Coordinates

High-performance spotlight Synthetic Aperture Radar (SAR) requires measurement of the radars motion during the synthetic aperture. A convenient coordinate frame for motion measurement is often not the convenient coordinate frame for motion compensation during the SAR data generation and image formation processing. A convenient frame for radar motion measurement is the Earth-Centered Earth-Fixed (ECEF) coordinate frame, whereas spotlight SAR processing typically require s polar coordinates from a selected Scene Reference Point (SRP). This report presents the conversion from ECEF coordinates to appropriate parameters for SAR processing.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Unmanned Aerial Vehicle Synthetic Aperture RADAR for Surface Change Monitoring

Space-based and airplane-based synthetic aperture RADAR (SAR) can monitor ground height using interferometric SAR (InSAR) collections. However, fielding the airplane-based SAR is expensive and coordinating the frequency and timing of ground experiments with space-based SAR is challenging. This research explored the possibility of using a small, mobile unmanned aerial vehicle- base (UAV) SAR to see if it could provide a quick and inexpensive InSAR option for the Source Physics Experiment (SPE) Phase III project. Firstly, a local feasibility collection using a UAV-based SAR showed that InSAR products and height measurements were possible, but that in-scene fiducials were needed to assist in digital elevation model (DEM) construction. Secondly, an InSAR collection was planned and executed over the SPE Phase III site using the same platform configuration. We found that the image formation by the SAR manufacturer creates discontinuities, and that noise impacted the generation and accuracy of height maps. These processing artifacts need to be overcome to generate an accurate height map.

47 OTHER INSTRUMENTATION↗
NASA NTRS1967

Radiography. Volume 4 - Making a radiograph

Radiographic image formation, sensitivity, and exposure calculations described in programmed instruction textbook on radiography for use in nondestructive testing

Source record↗
NASA NTRS1971

The improvement of star positions by photographic methods

A brief description is given of the new astrometric camera and of the program on which it is being employed. This is the photography of the southern sky so that each star appears on at least four overlapping plates. Sets of star coordinates measured on each plate are combined with a limited set of provisional meridian places to give an accurate set of relative star positions which are independent of the meridian system together with a set of residuals for each plate-star. The technique is based on a simple geometrical model of image formation on photographic plates. Current investigations are concerned with the elimination of sources of systematic deviation from this model.

Clube, S. V. M.↗
NASA NTRS1972

ERTS two-inch RBV cameras performance characteristics.

A very-high resolution multispectral television camera system is being developed for NASA for use on the ERTS program. There are three cameras in the system, each viewing the same area but operating in the blue-green, red, and near-infrared spectral bands. In the laboratory, the cameras' limiting resolution is 4500 TV lines over the 25x25-mm image format of the return beam vidicon (RBV). Analysis of typical ERTS scenes shows that actual contrast ratios will be much lower than those of laboratory test targets. A model was developed to predict the resolving power performance of the RBV camera under realistic conditions.

Miller, B. P.↗
NASA NTRS1972

Electronographic cameras for space astronomy.

Magnetically-focused electronographic cameras have been under development at the Naval Research Laboratory for use in far-ultraviolet imagery and spectrography, primarily in astronomical and optical-geophysical observations from sounding rockets and space vehicles. Most of this work has been with cameras incorporating internal optics of the Schmidt or wide-field all-reflecting types. More recently, we have begun development of electronographic spectrographs incorporating an internal concave grating, operating at normal or grazing incidence. We also are developing electronographic image tubes of the conventional end-window-photo-cathode type, for far-ultraviolet imagery at the focus of a large space telescope, with image formats up to 120 mm in diameter.

Carruthers, G. R.↗
NASA NTRS1974

Lunar laser ranging data deposited in the National Space Science Data Center: Filtered Observations for July through December 1972 and unfiltered photon dections for January through July 1973

The data acquired by the lunar laser ranging experiment are described for the six months period ending 31 December, 1972. The data are contained on two files of a binary tape written in card image format, using a CDC 6400/6600 computer. Photon detections, and unfiltered photon stops are included.

Mulholland, J. D.↗
NASA NTRS1979

Kitt Peak speckle camera

The speckle camera in regular use at Kitt Peak National Observatory since 1974 is described in detail. The design of the atmospheric dispersion compensation prisms, the use of film as a recording medium, the accuracy of double star measurements, and the next generation speckle camera are discussed. Photographs of double star speckle patterns with separations from 1.4 sec of arc to 4.7 sec of arc are shown to illustrate the quality of image formation with this camera, the effects of seeing on the patterns, and to illustrate the isoplanatic patch of the atmosphere.

Breckinridge, J. B.↗
NASA NTRS1979

The detection of urban expansion from Landsat imagery

Two methodologies for detecting and mapping land cover changes in and around growing urban regions are being studied at Jet Propulsion Laboratory. Both approaches, primarily based on digital image processing techniques, have been developed to supplement data stored in an Image Based Information System (IBIS). The structure of this information system enables the depiction of land cover changes in image format concurrently with statistical reports in tabular form. To date the expansion of two urban areas, Houston, Texas and Orlando, Florida, has been monitored.

Friedman, S. Z.↗
NASA NTRS1980

An investigation of the modulation of capillary and short gravity waves in the open ocean

A preliminary investigation of the modulation of capillary and gravity waves by long ocean waves is described. A pressure transducer is used to obtain water surface displacements, and a high-response laser-optical system is used to detect short-wave slopes. Analytical techniques are developed to account for the orbital motion of long waves. The local mean squared wave slope is found to be maximum leeward of the long-wave crests. For the long waves studied here and for short waves from 1 cm to 1 m, the longer a short-wave component is, the more leeward its maximum tends to occur. Also, the shortest waves tend to modulate least. The modulation of short waves is found to be strong enough to be an important component of the synthetic aperture radar image formation mechanism for long ocean waves.

Evans, D. D.↗
NASA NTRS1980

Crop identification studies using Landsat data Separation of barley from other spring small grains and corn and soybean decision logic

Two labeling procedures were developed which identify various agricultural crops through the use of Landsat data. One procedure separates barley from other spring small grains, and the other identifies corn and soybeans. For both procedures, a minimum data set (critical acquisition time) has been designated. Landsat data in both image format and various graphic displays were used along with ancillary data to obtain information which aided in labeling the spectral signatures. The corn and soybean procedure also employed a structured decision logic. Test results for the barley separation procedure emphasized the importance of obtaining a critical acquisition and showed some success especially in areas where spring crops followed the expected growth patterns. Two tests of the corn and soybean procedure produced good labeling accuracies. Problems with the procedure were easy to identify, and some solutions were implemented for the second test. Automation of various parts of the procedure and extension to other crops and regions were recommended.

Dailey, C. L.↗
NASA NTRS1982

Velocity and attenuation of sound in arterial tissues

The velocity of sound in excised human and canine arterial tissues is measured in order to serve as a basis for the development and application of ultrasonic techniques for the diagnosis of atherosclerotic lesions. Measurements of sound velocity at different regions of 11 human and six canine aortas were made by a time delay spectrometer technique at frequencies from 2 to 10 MHz, and compared with ultrasonic attenuation parameters and the results of biochemical assays. Sound velocity is found to increase with increasing attenuation at all frequencies, and with increasing collagen content. A strong dependence of sound velocity on cholesterol content or low calcium contents is not observed, although velocities of up to 2000 m/sec are observed in highly organized calcified lesions. A decrease in velocity with decreasing temperature is also noted. It is thus concluded that it is principally the differences in tissue collagen levels that contribute to image formation according to sound velocity.

Rooney, J. A.↗
NASA NTRS1983

Low-level water vapor fields from the VAS split-window channels at 11 and 12 microns

Originally, the VAS split window channels were designed to use the differential water vapor absorption between 11 and 12 microns to estimate sea surface temperature by correcting for the radiometric losses caused by atmospheric moisture. It is shown that it is possible to reverse the procedure in order to estimate the vertically integrated low level moisture content with the background surface (skin) temperature removed, even over the bright, complex background of the land. Because the lower troposphere's water vapor content is an important factor in convective instability, the derived fields are of considerable value to mesoscale meteorology. Moisture patterns are available as quantitative fields (centimeters of precipitable water) at full VAS resolution (as fine as 7 kilometers horizontal resolution every 15 minutes), and are readily converted to image format for false color movies. The technique, demonstrated with GOES-5, uses a sequence of split window radiances taken once every 3 hours from dawn to dusk over the Eastern and Central United States. The algorithm is calibrated with the morning radiosonde sites embedded within the first VAS radiance field; then, entire moisture fields are calculated at all five observation times. Cloud contamination is removed by rejecting any pixel having a radiance less than the atmospheric brightness determined at the radiosonde sites.

Chesters, D.↗