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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Analysis of data acquired by synthetic aperture radar and LANDSAT Multispectral Scanner over Kershaw County, South Carolina, during the summer season

Data acquired by synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) were processed and analyzed to derive forest-related resources inventory information. The SAR data were acquired by using the NASA aircraft X-band SAR with linear (HH, VV) and cross (HV, VH) polarizations and the SEASAT L-band SAR. After data processing and data quality examination, the three polarization (HH, HV, and VV) data from the aircraft X-band SAR were used in conjunction with LANDSAT MSS for multisensor data classification. The results of accuracy evaluation for the SAR, MSS and SAR/MSS data using supervised classification show that the SAR-only data set contains low classification accuracy for several land cover classes. However, the SAR/MSS data show that significant improvement in classification accuracy is obtained for all eight land cover classes. These results suggest the usefulness of using combined SAR/MSS data for forest-related cover mapping. The SAR data also detect several small special surface features that are not detectable by MSS data.

Wu, S. T.↗
NASA NTRS1990

Reducing Speckle In One-Look SAR Images

Local-adaptive-filter algorithm incorporated into digital processing of synthetic-aperture-radar (SAR) echo data to reduce speckle in resulting imagery. Involves use of image statistics in vicinity of each picture element, in conjunction with original intensity of element, to estimate brightness more nearly proportional to true radar reflectance of corresponding target. Increases ratio of signal to speckle noise without substantial degradation of resolution common to multilook SAR images. Adapts to local variations of statistics within scene, preserving subtle details. Computationally simple. Lends itself to parallel processing of different segments of image, making possible increased throughput.

Nathan, K. S.↗
NASA NTRS1987

The Alaska synthetic aperture radar (SAR) facility project

A receiving station for the acquisition and processing of spaceborne synthetic aperture radar (SAR) data is being established by the National Aeronautics and Space Administration (NASA) at the University of Alaska, Fairbanks. The data that will be received from a number of SAR satellites that are to be launched starting in 1990 will allow U.S. researchers to study sea ice, oceanographic and geological features, hydrological processes, glaciers, and vegetation cover in Alaska and its surrounding seas.

Carsey, F.↗
NASA NTRS2016

Development of RFI Mitigation Techniques with Digital Beamforming

Remote sensing radars with longer wavelengths penetrate deeper into the observed scene and are more suitable for the scientific observation of ice sheets or vegetation. Therefore, SAR systems are moving to lower frequencies like L- or P-band. However, as the frequency spectrum is a limited resource, this means that the occupied frequency band has to be shared with existing users. These users can have serious impact on the imaging quality. Radio frequency interference (RFI) that arrives at the antenna together with the SAR backscatter is causing a drop of the signal-to-noise ratio. Despite the high processing gain of the SAR signal, artifacts can appear in the image if the RFI is strong enough. This can lead to a corruption of the acquired data and make it unsuitable for scientific purposes. Hence, the investigation of methods for RFI mitigation is critical to the performance of radar missions and to ensure they meet their main task.

Digital Beamforming↗
NASA NTRS1996

(abstract) Alaska SAR Facility Ocean and Ice Data Opportunities Over the Next Decade

The Alaska SAR Facility (ASF) is currently processing data from four satellites. All of these generate SAR data useful for ice observations and three of them generate data useful for ocean observations. The data sets from these satellites are available to approved US and other investigators although the approval mechanisms are different. More satellites are planned. These will carry SAR instruments of increased capability for ocean and ice observations. We will discuss the anticipated situation for access to these data sets by the scientific community and we will speculate on what the major oceanographic applications may be.

ice ocean observations SAR satellite observations ↗
NASA NTRS1980

A digital fast correlation approach to produce SEASAT SAR imagery

This paper describes a digital processing algorithm and its associated system design for producing images from SEASAT Synthetic Aperture Radar (SAR) data. The proposed system uses the fast Fourier transform approach to perform the two-dimensional correlation process. The range migration problem, which is often a major obstacle to efficient processing, can be alleviated by approximating the locus of echoes from a point target by several linear segments. SAR data corresponding to each segment is correlated separately, and the results are coherently summed to produce full-resolution images. This processing approach exhibits high computation efficiency and simple processing control functions. It is particularly attractive for software implementation based on general purpose computer. Results of this implementation and examples of digitally correlated SEASAT SAR imagery are discussed

Wu, C.↗
NASA NTRS1976

A digital system to produce imagery from SAR data

This paper describes a digital processing algorithm and its associated system design for producing images from Synthetic Aperture Radar (SAR) data. The proposed system uses the Fast Fourier Transform (FFT) approach to perform the two-dimensional correlation process. The range migration problem, which is often a major obstacle to efficient processing, can be alleviated by approximating the locus of echoes from a point target by several linear segments. SAR data corresponding to each segment is correlated separately, and the results are coherently summed to produce full-resolution images. This processing approach exhibits greatly improved computation efficiency relative to conventional digital processing methods.

Wu, C.↗
NASA NTRS1991

Estimating SAR Doppler Shifts From Homogeneous Targets

Algorithm that processes some of information in synthetic-aperture-radar (SAR) echoes from homogeneous targets yields optimal estimates of Doppler frequency shifts. Helps in further processing to extract as much information as possible about targets. Used to improve radiometric calibrations, to estimate direction of radar antenna, and to determine speeds of moving targets more accurately. Also helpful in measurements of speeds of ocean currents and of wind shears at airports.

Jin, Michael Y.↗
NASA NTRS2011

Low Latency DESDynI Data Products for Disaster Response, Resource Management and Other Applications

We are developing onboard processor technology targeted at the L-band SAR instrument onboard the planned DESDynI mission to enable formation of SAR images onboard opening possibilities for near-real-time data products to augment full data streams. Several image processing and/or interpretation techniques are being explored as possible direct-broadcast products for use by agencies in need of low-latency data, responsible for disaster mitigation and assessment, resource management, agricultural development, shipping, etc. Data collected through UAVSAR (L-band) serves as surrogate to the future DESDynI instrument. We have explored surface water extent as a tool for flooding response, and disturbance images on polarimetric backscatter of repeat pass imagery potentially useful for structural collapse (earthquake), mud/land/debris-slides etc. We have also explored building vegetation and snow/ice classifiers, via support vector machines utilizing quad-pol backscatter, cross-pol phase, and a number of derivatives (radar vegetation index, dielectric estimates, etc.). We share our qualitative and quantitative results thus far.

applications↗
NASA NTRS1996

RADARSAT Processing System at ASF

This paper outlines the ASF (Alaska SAR[synthetic aperture radar] Facility) Radarsat data processing requirements as driven by the science users and describes the Radarsat processing system design and implementaiton approach to meet the challenge of providing ASF with and integrated operational SAR image production facility. Design and implementation attributes that facilitate syswtem growth in handling future SAR missions such as Envisat and HIROS are also addressed.

ASF↗
DOE OSTI2026

Iterative ML and Experiments for Emerging VOCs

SAND2026-17074O Iterative ML and Experiments for Emerging VOCs is a tool that analyzes and predicts the behaviors of SARS-CoV-2 variants. It processes experimental data on ACE2 (the receptor for the SARS-CoV-2 virus that allows it to infect the cell) and antibody binding using machine learning models, including neural networks, to forecast ACE2 interactions and variant expression. The tool employs transfer learning and global epistasis modeling, integrating public datasets with proprietary data to enhance prediction accuracy. Additionally, it fits concentration-response curves to determine dissociation constants and generates visualizations to support research findings, thereby aiding in the identification of new antibodies for emerging variants of concern. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Sheffield, Thomas [Sandia National Lab. (SNL-NM), ↗
NASA NTRS1987

SAR image data compression for an on-line archive system

This paper summarizes the investigation of SAR image data compression for an on-line archive data distribution system. This system is planned for the ground processing system of Alaska SAR Facility (ASF) and Shuttle Imaging Radar (SIR-C). The objective of the SAR image data compression is to enable the data archive system to provide the remote users a large data base with good image quality, short response time, low transfer cost, and minimal decoding complexity. The requirements and limitations of the on-line archive data distribution system are presented. The effects of SAR image data characteristics on data compression are addressed. The users' survey results suggest that compression ratios between 10:1 and 20:1 appear suitable. Based on the algorithm evaluation results, the two-level tree-searched vector quantization technique has been recommended as the SAR image data compression algorithm for the on-line archive data distribution system.

Chang, C. Y.↗
NASA NTRS1994

Surface processes in Greenland Sea convection

ERS-1 SAR (Synthetic Aperture Radar) data were used to specify Winter physical processes on the surface of the Greenland Sea, and SSM/I (Special Sensor Microwave/Imager) data were used to characterize the regional behavior of the ice cover. Examination of the SSM/I data indicated that the convective water was likely to be confined to small (less than 100 km) domains near the ice edge. Using ERS-1 SAR data crossing the ice edge, it was possible to identify ice edge features that are very similar to modeled plumes; they have a diameter of about 100 m, a spacing of about 300 m, and cover an area about 20 by 90 km. This plume observation is the first such identification of convection. The plumes are topped by ice, and the return-water areas are open, indicating a freshened top layer of the sea and emphasizing the importance of this layer to convection.

Carsey, Frank D.↗
NASA NTRS1991

Observation of wave refraction at an ice edge by synthetic aperture radar

In this note the refraction of waves at the ice edge is studied by using aircraft synthesis aperture radar (SAR). Penetration of a dominant swell from open ocean into the ice cover was observed by SAR during the Labrador Ice Margin Experiment (LIMEX), conducted on the marginal ice zone (MIZ) off the east coast of Newfoundland, Canada, in March 1987. At an ice edge with a large curvature, the dominant swell component disappeared locally in the SAR imagery. Six subscenes of waves in the MIZ from the SAR image have been processed, revealing total reflection, refraction, and energy reduction of the ocean waves by the ice cover. The observed variations of wave spectra from SAR near the ice edge are consistent with the model prediction of wave refraction at the ice edge due to the change of wave dispersion relation in ice developed by Liu and Mollo-Christensen (1988).

Liu, Antony K.↗
NASA NTRS1998

Poro-elastic Rebound Along the Landers 1992 Earthquake Surface Rupture

Maps of post-seismic surface displacement after the 1992, Landers, California earthquake, generated by interferometric processing of ERS-1 Synthetic Aperture Radar (SAR) images, reveal effects of various deformation processes near the 1992 surface rupture.

Poro-elastic rebound Landers Earthquake Interferom↗
DOE OSTI2024

Framework for a Digital Documented Safety Analysis

This framework is developed to progress the digital implementation of digital tools applied to the DOE authorization process, with future applications to NRC SAR development/review, to accelerate the design and review processes of advanced nuclear reactors. The engineering design and licensing process for nuclear reactors is currently burdened by a document-based approach that leads to duplications and errors due to a lack of traceability among numerous static documents. Changes to design information require labor-intensive manual tracing through these documents, creating a high potential for human error. The adoption of a digital ecosystem, utilizing a digital thread to link various aspects of project design and analysis, promises dynamic documentation generation, automatic updates, and error reduction. Model Based Definition (MBD) and Product Lifecycle Management (PLM) tools are central to this digital transformation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1998

Data Quality of the JERS-1 SAR Global Rain Forest Mapping (GRFM) Project

The National Space Development Agency of Japan's (NASDA) JERS-1 SAR began collecting data in 1995 for the Global Rain Forest Mapping Project (GRFM). The GRFM data quality has been examined for products resulting from both the NASDA and Alaska SAR facility's (ASF) processing facilities.

JERS-1 SAR Rain Forest Mapping↗