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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Imaging Radar Interferometry

Synthetic aperture radar has been used for high resolution imaging from aircraft and satellites for many years.

imaging radar interferometry↗
NASA NTRS1992

Radio and optical interferometric imaging

Since diffraction-limited imaging with a single aperture yields angular resolution approx. lambda/D, the attainment of high angular resolution with single apertures requires the construction of correspondingly large monolithic apertures, the whole surface of which must be figured to much less than a wavelength. At the longer wavelengths, it is impossible to build a sufficiently large single aperture: for example, at lambda 21 cm, arcsec resolution requires an aperture of diameter approx. 50 km. At the shorter wavelengths, the atmosphere imposes a natural limit in resolution of about one arcsec. However, another route is possible; that is, using synthetic apertures to image the sky. Synthetic apertures are now in use in many fields, e.g., radio interferometry, radar imaging, and magnetic-resonance imaging. Radio-interferometric techniques developed in radio astronomy over the past 40 years are now being applied to optical and IR astronomical imaging by a number of groups. Furthermore, the problem of figuring synthetic apertures is considerably simpler, and can be implemented in a computer: new 'self-calibration' techniques allow imaging even in the presence of phase errors due to the atmosphere.

Cornwell, Tim J.↗
NASA NTRS1996

Surface Deformation and Coherence Measurements of Kilauea Volcano, Hawaii, from SIR-C Radar Interferometry

The shuttle imaging radar C/X synthetic aperture radar (SIR-C/X-SAR) radar on board the space shuttle Endeavor imaged Kilauea Volcano, Hawaii, in April and October 1994 for the purpose of measuring active surface deformation by the methods of repeat-pass differential radar interferometry. Observations at 24 cm (L band) and 5.6 cm (C band) wavelengths were reduced to interferograms showing apparent surface deformation over the 6-month interval and over a succession of 1-day intervals in October. A statistically significant local phase signature in the 6-month interferogram is coincident with the Pu'u O'o lava vent. Interpreted as deformation, the signal implies centimeter-scale deflation in an area several kilometers wide surrounding the vent. Peak deflation is roughly 14 cm if the deformation is purely vertical, centered southward of the Pu'u O'o caldera. Delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures, at the level of 12 cm peak-to-peak in the radar line-of-sight direction. Though the phase observations are suggestive of the wide-area deformation measured by Global Positioning System (GPS) methods, the atmospheric effects are large enough to limit the interpretation of the result. It is difficult to characterize centimeter-scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous, spatially distributed measurements of reactivity along the radar line of sight. Studies of the interferometric correlation of images acquired at different times show that L band is far superior to C band in the vegetated areas, even when the observations are separated by only 1 day. These results imply longer wavelength instruments are more appropriate for studying surfaces by repeat-pass observations.

Rosen, P. A.↗
NASA NTRS1995

Atmospheric Limitations to Repeat-Track Radar Interferometry

In a recent mission, the Shuttle Imaging Radar (SIR-C) satellite devoted three days to repeat-track interferometry. The data was analyzed from a test site in the Mojave desert of California. Although good topography was obtained, most of the error was caused by turbulent water vapor in the lower atmosphere. Analysis of the effects of water vapor on multiple-track interferometry is given.

shuttle↗
NASA NTRS1999

Achievements in the Development of Space-borne Imaging Radar

This article describes past and current achievements in the development of space-borne imaging radar technology and discusses possibilities for the future. The article focuses on space-borne capabilities for civil and scientific purposes.

space-borne imaging radar interferometry↗
NASA NTRS1995

Atmospheric Limitations to Repeat-Track Radar Interferometry

In its recent radar imaging mission, the Shuttle Imaging Radar satellite (SIR-C) devoted three days to repeat-track interferometry. We have analyzed the data from a test site in the Mojave desert of California. Although good topography ( +/- 10 m on 21 m postings) was obtained, most of the error was caused by turbulent water vapor in the lower atmosphere. Spatial structure of 6 km and all smaller sizes was observed. The RMS, one-way time delay was found to be 0.24 cm. Essentially identical results were obtained at two wavelengths, 24 and 5.7 cm.

Goldstein, Richard↗
NASA NTRS1998

Synthetic Aperture Radar Interferometry

Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

remote sensing SAR Synthetic Aperture Radar interf↗
NASA NTRS2004

Aseismic deformation of a fold-and-thrust belt imaged by SAR interferometry near Shahdad, southeast Iran

At depth, many fold-and-thrust belts are composed of a gently dipping, basal thrust fault and steeply dipping, shallower splay faults that terminate beneath folds at the surface. Movement on these buried faults is difficult to observe, but synthetic aperture radar (SAR) interferometry has imaged slip on at least 600 square kilometers of the Shahdad basal-thrust and splay-fault network in southeast Iran.

SAR interferometry salellite measurements fold and↗
NASA NTRS1980

Images of Venus by three-station radar interferometry - 1977 results

During the 1977 inferior conjunction of Venus, radar observations were made using three receiving stations as a multiple interferometer. Maps of surface reflectivity and altimetry were prepared from these observations. The new altimetry maps show considerable improvement in relation to many of the earlier maps made using the two-station interferometer. In particular, there are consistent and explainable correlations between the altimetry and reflectivity maps that did not always exist in the past. The highest-resolution maps (about 8 km) show three isolated mountains having altitudes of approximately 2 km above their environs, a pair of ridges separated by approximately 100 km and extending 800 km, and a few anomalous reflectivity features for which little or no altitude change is observed. Other maps at slightly lower resolution show a bright irregular ringed crater, a few large low-reflectivity regions, a shallow crater 150 km in diameter, a gently sloping mountain, and a short ridge running north-south. Many of the later features have been seen in earlier radar maps and should be useful in refining the spin axis and further characterizing the regolith of certain areas of Venus.

Jurgens, R. F.↗
NASA NTRS2000

Application of Radar Data to Remote Sensing and Geographical Information Systems

The field of synthetic aperture radar changed dramatically over the past decade with the operational introduction of advance radar techniques such as polarimetry and interferometry. Radar polarimetry became an operational research tool with the introduction of the NASA/JPL AIRSAR system in the early 1980's, and reached a climax with the two SIR-C/X-SAR flights on board the space shuttle Endeavour in April and October 1994. Radar interferometry received a tremendous boost when the airborne TOPSAR system was introduced in 1991 by NASA/JPL, and further when data from the European Space Agency ERS-1 radar satellite became routinely available in 1991. Several airborne interferometric SAR systems are either currently operational, or are about to be introduced. Radar interferometry is a technique that allows one to map the topography of an area automatically under all weather conditions, day or night. The real power of radar interferometry is that the images and digital elevation models are automatically geometrically resampled, and could be imported into GIS systems directly after suitable reformatting. When combined with polarimetry, a technique that uses polarization diversity to gather more information about the geophysical properties of the terrain, a very rich multi-layer data set is available to the remote sensing scientist. This talk will discuss the principles of radar interferometry and polarimetry with specific application to the automatic categorization of land cover. Examples will include images acquired with the NASA/JPL AIRSAR/TOPSAR system in Australia and elsewhere.

vanZyl, Jakob J.↗
NASA NTRSDate not supplied

Independent Technical Assessment of NASA and External Quantum Sensing Capability

The recent FY 2020 federal Research and Development Budget Priorities memo addresses the leadership need in Quantum Information Science (QIS) directing agencies to “prioritize QIS research and development (R&D), which will build the technical and scientific base necessary to explore the next generation of QIS theory, devices, and applications.” Quantum Sensing (QS) is an integral part of QIS. NASA is a key part of the directive to forward American space exploration and commercialization by providing “capabilities that have broad potential applications in space and on Earth.” QS provides an arena for NASA to demonstrate leadership in both areas of the administrative directive. QS uses quantum properties to achieve unprecedented measurement sensitivity and performance, including quantum-enhanced methodologies that outperform their classical counterparts. Typical quantum sensors exploit techniques such as atomic systems, matter waves, quantum entanglement, quantum superposition of states, quantum illumination methods, and manipulation of photons and atoms, in general. Guided by advancements in our ability to generate, manipulate, and control quantum systems, the emerging quantum sensing technologies promise unrivalled sensitivity, resolution, and precision, potentially leading to game-changing applications. Significant gains include technologies important for a range of NASA missions such as remote sensing, in situ measurements, metrology, interferometry, quantum communication, ranging, imaging, radar and lidar receivers, and gravity measurements. NASA Engineering and Safety Center has convened an independent external panel, comprising of Quantum Sensing Experts from Government, DoD, academia, and Federally funded Research and Development Center to conduct an independent technical assessment of the agency's capabilities in Quantum Sensing to understand NASA's internal needs and competencies related to Quantum Sensing and compare agency capabilities with those available externally including industry, academia, and other government agencies. The outcomes of the assessment will help the agency in establishing appropriate strategies and investments to develop and maintain the state-of-the-art sensing competence and capabilities required to meet the agency’s future needs. The External Experts Panel (EEP) is collaborating with HQ, various NASA Center and the representatives in the NASA Quantum Sensing Community of Practice (QS CoP), a part of NASA Sensors and Instrumentation Technical Fellow Technical Discipline Team, in obtaining common, current understanding of agency mission needs where QS can be an important enabler for future needs, and any programs, projects, assets, and technologists working in QS. The EEP organized a Quantum Sensing Workshop of practitioners from industry, academia, other government agencies, external experts, and interested NASA personnel to gather the assessment information. EEP also conducted information gathering on the industry at large, educational institutions, and other government agency research efforts for capture in the assessment database. At the conclusion of this assessment, EEP team will develop findings and conclusions describing NASA’s capabilities for the mission needs, NASA's relative position on new, enabling technologies, and an analysis of the gaps that may present any risks to near-term or far-term mission needs. This presentation will give details of the NASA and External Quantum Sensing Assessment outcomes, findings, observations, and its recommendation to NASA as how it can advance Quantum Sensing technologies and techniques for its science and explorations related missions.

External Quantum Sensing Capability↗