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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Real-time image difference detection using a polarization rotation spacial light modulator

An image difference detection system is described, of the type wherein two created image representations such as transparencies representing the images to be compared lie coplanar, while light passes through the two transparencies and is formed into coincident images at the image plane for comparison. The two transparencies are formed by portions of a polarization-rotation spatial light modulator display such as a multi-pixel liquid crystal display or a magnetooptical rotation type display. In a system where light passing through the two transparencies is polarized in transverse directions to enable the use of a Wollaston prism to bring the images into coincidence, a liquid crystal display can be used which is devoid of polarizing sheets that would interfere with transverse polarizing of the light passing through the two transparencies.

Chao, Tien-Hsin↗
NASA NTRS2022

Characterization of Rochon Prisms for Bi-Directional Imaging Applications

Polarizing prisms are often used in applications where light is split into two separate beams of orthogonal polarization, or to isolate a beam with a preferred polarization state. These prisms are typically used with lasers, but there are applications of their use with imaging systems. One such example is that of a recently developed focusing schlieren system, where light must be transmitted through a Rochon prism in both the forward and backward directions. Three Rochon prisms were characterized in this study in terms of their transmitted intensity and polarization state: a quartz/quartz prism, a glass/quartz prism, and a MgF2/MgF2 prism. Laser testing at four wavelengths was performed, along with full clear aperture collimated LED light testing at a single wavelength. The glass/quartz and MgF2/MgF2 prisms operated in the same manner when light was transmitted in either the forward or backward direction. The quartz/quartz prism, however, exhibited differences between operation in the forward and backward direction. In the forward orientation for input plane polarized light, the transmitted intensity varied sinusoidally as a function of height of incidence through the prism, while the polarization of the unrefracted and refracted beams were uniform and orthogonally polarized. In the backward orientation, the intensity for both unrefracted and refracted beams was uniform, but the azimuthal orientation of the output plane polarized light varied sinusoidally as a function of height of incidence through the prism, while remaining orthogonally polarized between the two beams at each position.

Joshua M Weisberger↗
NASA NTRS1998

Low-field MRI of laser polarized noble gas

NMR images of laser polarized 3He gas were obtained at 21 G using a simple, homebuilt instrument. At such low fields magnetic resonance imaging (MRI) of thermally polarized samples (e.g., water) is not practical. Low-field noble gas MRI has novel scientific, engineering, and medical applications. Examples include portable systems for diagnosis of lung disease, as well as imaging of voids in porous media and within metallic systems.

Non-NASA Center↗
NASA NTRS1999

A system for low field imaging of laser-polarized noble gas

We describe a device for performing MRI with laser-polarized noble gas at low magnetic fields (<50 G). The system is robust, portable, inexpensive, and provides gas-phase imaging resolution comparable to that of high field clinical instruments. At 20.6 G, we have imaged laser-polarized (3)He (Larmor frequency of 67 kHz) in both sealed glass cells and excised rat lungs, using approximately 0.1 G/cm gradients to achieve approximately 1 mm(2) resolution. In addition, we measured (3)He T(2)(*) times greater than 100 ms in excised rat lungs, which is roughly 20 times longer than typical values observed at high ( approximately 2 T) fields. We include a discussion of the practical considerations for working at low magnetic fields and conclude with evidence of radiation damping in this system. Copyright 1999 Academic Press.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRS2014

The Large-Scale Current System During Auroral Substorms

We present an empirical model of the equivalent current system in the ionosphere during the peak of a classical bulge-type auroral sub storm. This model is derived from measurements made by ~110 ground magnetometer stations during 116 substorms. The data are temporally and spatially organized using global auroral images obtained by the Polar Visible Imaging System Earth Camera. The empirical equivalent current system displays three key features: a poleward shift of the westward electrojet connecting the postmidnight and premidnight components; a polar cap swirl; and significantly different magnitudes of the postmidnight and premidnight westward electrojets. This leads us to propose a two-wedge current system linking the ionosphere to the magnetosphere. The bulge current wedge is located in the premidnight region just equatorward of the open-closed field line boundary while another three-dimensional current system is located in the postmidnight region well within the auroral oval. We use Biot and Savart calculations and Tsyganenko mapping and show that this new model is a likely solution for the large-scale current system.

magnetic storms↗
NASA NTRS2003

THEMIS Visible Imaging of the South Polar Layered Deposits, Martian Southern Spring, 2003

The polar layered deposits (PLD) of Mars have attracted considerable attention since their identification in Mariner 9 images, largely due to the possibility that these finely layered, volatile-rich deposits hold a record of recent eras in Martian climate history. The PLD have been a target of imaging and other sensors in the last several decades, but only recently has it been possible to obtain a moderately high resolution image map, using the visible sensor on 2001 Mars Odyssey s Thermal Emission Imaging System (THEMIS). We report here on the acquisition of a 36 meter/pixel contiguous single-band visible image data set of the south polar layered deposits (SPLD), obtained during early southern spring in 2003. The data will undoubtedly be applied to many problems in Mars polar studies. We will discuss here, and in more detail at the Conference, the use of these images to further characterize the population of impact craters on the SPLD, and the implications of the observed population for the age and evolution of the SPLD.

Plaut, J. J.↗
NASA NTRS2003

Conjugate Auroral Imagery

Conjugate studies of high-latitude geomagnetic activity are central to understanding the (truly) global magnetospheric response to external perturbations, i.e. the solar wind, and the role of the ionosphere in modulating and coupling with the magnetosphere. Interhemispheric asymmetries as manifested in auroral emissions have been observed for over 40 years. Unfortunately, the nature of the problem has limited the type and extent of studies that can be performed to either conjugate ground based observations or comparison of space based images with all-sky cameras. Recently Frank and Sigwarth (2002) published results using unique simultaneous images from Polar of the northern and southern aurora, but these are necessarily limited to the nighttime and at oblique angles. However, conjunctive images made with the cameras from the Polar and IMAGE missions contain simultaneous conjugate images of the large-scale aurora under many and varying conditions. This rich data set provides an opportunity to study interhemispheric auroral asymmetries and investigate their occurrence as a function of solar wind conditions and ionospheric parameters such as conductivity. In order to use images of different scenes from each of these cameras, knowledge of their relative response is required. To that end, this paper will present preliminary results of comparing the images with emphasis on data from the Polar UVI LBH filters and the IMAGE FUV WIC.

Spann, Jim↗
NASA NTRS2006

Tracking the Martian CO2 Polar Ice Caps in Infrared Images

Researchers at NASA s Jet Propulsion Laboratory have developed a method for automatically tracking the polar caps on Mars as they advance and recede each year (see figure). The seasonal Mars polar caps are composed mainly of CO2 ice and are therefore cold enough to stand out clearly in infrared data collected by the Thermal Emission Imaging System (THEMIS) onboard the Mars Odyssey spacecraft. The Bimodal Image Temperature (BIT) histogram analysis algorithm analyzes raw, uncalibrated data to identify images that contain both "cold" ("polar cap") and "warm" ("not polar cap") pixels. The algorithm dynamically identifies the temperature that separates these two regions. This flexibility is critical, because in the absence of any calibration, the threshold temperature can vary significantly from image to image. Using the identified threshold, the algorithm classifies each pixel in the image as "polar cap" or "not polar cap," then identifies the image row that contains the spatial transition from "polar cap" to "not polar cap." While this method is useful for analyzing data that has already been returned by THEMIS, it has even more significance with respect to data that has not yet been collected. Instead of seeking the polar cap only in specific, targeted images, the simplicity and efficiency of this method makes it feasible for direct, onboard use. That is, THEMIS could continuously monitor its observations for any detections of the polar-cap edge, producing detections over a wide range of spatial and temporal conditions. This effort can greatly contribute to our understanding of long-term climatic change on Mars.

Wagstaff, Kiri L.↗
NASA NTRS2003

Themis Visible Imaging of the South Polar Layered Deposits, Martian Southern Spring, 2003

The polar layered deposits (PLD) of Mars have attracted considerable attention since their identification in Mariner 9 images, largely due to the possibility that these finely layered, volatile-rich deposits hold a record of recent eras in Martian climate history. The PLD have been a target of imaging and other sensors in the last several decades, but only recently has it been possible to obtain a moderately high resolution image map, using the visible sensor on 2001 Mars Odyssey's Thermal Emission Imaging System (THEMIS). We report here on the acquisition of a 36 meter/pixel contiguous single-band visible image data set of the south polar layered deposits (SPLD), obtained during early southern spring in 2003. The data will undoubtedly be applied to many problems in Mars polar studies.

Mariner 9↗
NASA NTRS2016

Polarimetry and Flux Distribution in the Debris Disk Around HD 32297

We present high-contrast angular differential imaging (ADI) observations of the debris disk around HD32297 in H-band, as well as the first polarimetric images for this system in polarized differential imaging (PDI) mode with Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at > or = 5(sigma) levels from approx. 0.45" to approx.1.7" (50-192AU) from the star and recover the spine deviation from the midplane already found in previous works. We also find for the first time imaging and surface brightness (SB) indications for the presence of a gapped structure on both sides of the disk at distances of approx. 0.75" (NE side) and approx. 0.65" (SW side). Global forward-modeling work delivers a best-fit model disk and well-fitting parameter intervals that essentially match previous results, with high-forward scattering grains and a ring located at 110AU. However, this single ring model cannot account for the gapped structure seen in our SB profiles. We create simple double ring models and achieve a satisfactory fit with two rings located at 60 and 95AU, respectively, low-forward scattering grains and very sharp inner slopes. In polarized light we retrieve the disk extending from approx. 0.25-1.6", although the central region is quite noisy and high S/N are only found in the range approx. 0.75-1.2". The disk is polarized in the azimuthal direction, as expected, and the departure from the midplane is also clearly observed. Evidence for a gapped scenario is not found in the PDI data. We obtain a linear polarization degree of the grains that increases from approx. 10% at 0.55" to approx. 25% at 1.6". The maximum is found at scattering angles of 90, either from the main components of the disk or from dust grains blown out to larger radii.

high-contrast angular differential imaging (ADI)↗
NASA NTRS1982

Weather satellites: Stereoscopy and Sounding; Proceedings of the Topical Meeting, Ottawa, Canada, May 16-June 2, 1982

Attention is given to the validation of meteorological satellite observing systems and to stereoscopic observations from meteorological satellites. Particular papers are presented on such topics as the comparison of cloud top heights measured by airborne lidar and TIROS-N image data, the determination of surface global radiation using Meteosat images and ground-based visibility measurements, multichannel improvements to satellite-derived global sea surface temperatures, validation of the Stratospheric Sounding Unit, and the international comparison of satellite winds. Also considered is tropical storm structure revealed by stereo photographs from Skylab, stereo imaging from polar orbit and synthetic stereo imaging, simultaneous measurements of sea surface temperature by GMS-1 and GMS-2, and real-time spectroscopic applications using the GOES operational satellites.

Yates, H.↗
NASA NTRS2000

Global Remote Sensing of Precipitating Electron Energies: A Comparison of Substorms and Pressure Pulse Related Intensifications

The Polar Ultraviolet Imager (UVI) observes aurora responses to incident solar wind pressure pulses and interplanetary shocks such its those associated with coronal mass ejections. Previous observations have demonstrated that the arrival of it pressure pulse at the front of the magnetosphere results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside aurora precipitations. Our observations show it simultaneous brightening over bread areas of the dayside and nightside auroral in response to a pressure pulse, indicating that more magnetospheric regions participate as sources for auroral precipitation than during isolate substorm. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated event to those during isolated substorms. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral substorms. Electron precipitation during substorms has characteristic energies greater than 10 KeV and is structured both in local time and in magnetic latitude. For auroral intensifications following the arrival of'a pressure pulse or interplanetary shock. Electron precipitation is less spatially structured and has greater flux of lower characteristic energy electrons (Echar less than 7 KeV) than during isolated substorm onsets. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and magnetospheric response to perturbations in the solar wind.

Chua, D.↗
NASA NTRS2000

Magnetic resonance imaging of convection in laser-polarized xenon

We demonstrate nuclear magnetic resonance (NMR) imaging of the flow and diffusion of laser-polarized xenon (129Xe) gas undergoing convection above evaporating laser-polarized liquid xenon. The large xenon NMR signal provided by the laser-polarization technique allows more rapid imaging than one can achieve with thermally polarized gas-liquid systems, permitting shorter time-scale events such as rapid gas flow and gas-liquid dynamics to be observed. Two-dimensional velocity-encoded imaging shows convective gas flow above the evaporating liquid xenon, and also permits the measurement of enhanced gas diffusion near regions of large velocity variation.

Non-NASA Center↗
NASA NTRS2004

Development of Laser-Polarized Noble Gas Magnetic Resonance Imaging (MRI) Technology

We are developing technology for laser-polarized noble gas nuclear magnetic resonance (NMR), with the aim of enabling it as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation, perfusion, and gas-exchange. In addition, laser-polarized noble gases (3He and 1BXe) do not require a large magnetic field for sensitive NMR detection, opening the door to practical MRI with novel, open-access magnet designs at very low magnetic fields (and hence in confined spaces). We are pursuing two specific aims in this technology development program. The first aim is to develop an open-access, low-field (less than 0.01 T) instrument for MRI studies of human gas inhalation as a function of subject orientation, and the second aim is to develop functional imaging of the lung using laser-polarized He-3 and Xe-129.

Walsworth, Ronald L.↗
NASA NTRS1981

Rectification and enhancement of three severely distorted images of Jupiter's north polar region

A number of high-resolution images of Jupiter's northern hemisphere were received from the imaging photopolarimeter (IPP) aboard Pioneer 11 in 1974. Erratic scanning of the IPP caused severe distortions in three scientifically important images, which until now have never been satisfactorily restored. New rectification and enhancement techniques, implemented on up-to-date image processing hardware, yielding images of sufficient quality to enable full scientific exploitation of the photometric data are reported.

Strickland, R. N.↗
NASA NTRS1983

Remote sensing with spaceborne synthetic aperture imaging radars: A review

A review is given of remote sensing with Spaceborne Synthetic Aperture Radars (SAR's). In 1978, a spaceborne SA was flown on the SEASAT satellite. It acquired high resulution images over many regions in North America and the North Pacific. The acquired data clearly demonstrate the capability of spaceborne SARs to: image and track polar ice floes; image ocean surface patterns including swells, internal waves, current boundaries, weather boundaries and vessels; and image land features which are used to acquire information about the surface geology and land cover. In 1981, another SAR was flown on the second shuttle flight. This Shuttle Imaging Radar (SIR-A) acquired land and ocean images over many areas around the world. The emphasis of the SIR-A experiment was mainly toward geologic mapping. Some of the key results of the SIR-A experiment are given.

Cimino, J. B.↗
NASA NTRS2019

Implementing Polar Projections with OGC Services for the Enhancement of AIRS NRT Visualization in LANCE

The Atmospheric Infrared Sounder (AIRS) NRT product is one important element in the Land, Atmosphere Near real-time Capability for EOS (LANCE). The LANCE processing of AIRS NRT products and the image generation are performed at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). The Open Geospatial Consortium (OGC) services are being utilized to access AIRS NRT images. The ongoing AIRS NRT imagery enhancement work includes adding a new set of the images in polar projections. Polar projections are commonly used for mapping Antarctica and Arctic regions. We have implemented more precise south polar (EPSG:3031) projection and north polar (EPSG:3413) projection making our OGC service instances more useful and interoperable. Thus, AIRS NRT data can be easily accessed and integrated with other applications. It greatly increases the impact of our data on researches in polar regions.In this presentation, we will introduce the optimized processing workflow for OGC services from data access with spatial-temporal index to data visualization with different SLD, and demonstrate how to use open source software to provide more precise map images in polar projections.

Zhao, Peisheng↗