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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 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Upgrading and testing program for narrow band high resolution planetary IR imaging spectrometer

An imaging spectrometer, intended primarily for observations of the outer planets, which utilizes an acoustically tuned optical filter (ATOF) and a charge coupled device (CCD) television camera was modified to improve spatial resolution and sensitivity. The upgraded instrument was a spatial resolving power of approximately 1 arc second, as defined by an f/7 beam at the CCD position and it has this resolution over the 50 arc second field of view. Less vignetting occurs and sensitivity is four times greater. The spectral resolution of 15 A over the wavelength interval 6500 A - 11,000 A is unchanged. Mechanical utility has been increased by the use of a honeycomb optical table, mechanically rigid yet adjustable optical component mounts, and a camera focus translation stage. The upgraded instrument was used to observe Venus and Saturn.

Wattson, R. B.↗
NASA NTRS1981

Resolution requirements for a soil moisture imaging radar

Image simulation techniques were employed to establish the relationship between spatial resolution and the accuracy of soil moisture estimated by an imaging radar. A spaceborne synthetic aperture radar at an orbital altitude of 600 km, operating at 4.5 GHz with HH polarization configuration and covering a ground swath width of 143 km corresponding to an angle of incidence range extending between 7-22 degrees relative to the vertical, provided the images simulated by a 17.7 km x 19.3 km test site. The role of resolution was evaluated by simulating various sets of images with resolutions ranging from 20 m x 20 m to 1 km x 1 km. Each simulated image was subjected to a soil moisture prediction algorithm whose input is limited to the image intensity level. Results show that the 1 km x 1 km resolution provides the best prediction accuracy for most soil moisture distributions except for drought-like conditions for which the 100 m x 100 m resolution is found to be preferred. In general it was found that the soil moisture of about 90% of the pixels is predicted with an error of + or - 20% of field capacity or less.

Dobson, C.↗
NASA NTRS1989

New features in Saturn's atmosphere revealed by high-resolution thermal infrared images

Observations of the stratospheric IR emission structure on Saturn are presented. The high-spatial-resolution global images show a variety of new features, including a narrow equatorial belt of enhanced emission at 7.8 micron, a prominent symmetrical north polar hotspot at all three wavelengths, and a midlatitude structure which is asymmetrically brightened at the east limb. The results confirm the polar brightening and reversal in position predicted by recent models for seasonal thermal variations of Saturn's stratosphere.

Gezari, D. Y.↗
NASA NTRS1990

Incidence angle and resolution - Potential effects on interpreting Venusian impact craters in Magellan radar images

The effects of incidence angle and spatial resolution are analyzed in order to evaluate the types of information that Magellan imaging radar may provide about impact craters on Venus. Seasat synthetic-aperture radar images of small terrestrial craters at high resolution (about 25 m) and Soviet Venera images of comparatively large Venusian craters at low resolution (1000 to 2000 m) and shorter wavelength show comparable radar responses to crater morphology. At low incidence angles, it is difficult to locate the precise position of crater rims on images, while at higher incidence angles, images show less distortion of crater morphology. Magellan will obtain images through a range of incidence angles varying from about 45 deg at low latitudes to 16 deg at polar latitudes. Radially symmetrical landforms such as impact craters are expected to show outlines that vary with the incidence angle and to appear bilaterally symmetrical and increasingly compressed at higher latitude.

Ford, J. P.↗
NASA NTRS2016

Seasonal Monitoring and Estimation of Regional Aerosol Distribution over Po Valley, Northern Italy, Using a High-Resolution MAIAC Product

In this work, the new 1-km-resolved Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm is employed to characterize seasonal AOD-PM10 correlations over northern Italy. The accuracy of the new dataset is assessed versus the widely used Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5.1 Aerosol Optical Depth (AOD) data, retrieved at 0.55 microns with spatial resolution of 10 km (MYD04). We focused on evaluating the ability of these two products to characterize both temporal and spatial distributions of aerosols within urban and suburban areas. Ground PM10 measurements were obtained from 73 of the Italian Regional Agency for Environmental Protection (ARPA) monitoring stations, spread across northern Italy, for a three-year period from 2010 to 2012. The Po Valley area (northern Italy) was chosen as the study domain because of severe urban air pollution, resulting from the highest population and industrial manufacturing density in the country, being located in a valley where two surrounding mountain chains favor the stagnation of pollutants. We found that the global correlations between PM10 and AOD are R(sup 2) = 0.83 and R(sup 2) = 0.44 for MYD04_L2 and for MAIAC, respectively, suggesting for a greater sensitiveness of the high-resolution product to small-scale deviations. However, the introduction of Relative Humidity (RH) and Planetary Boundary Layer (PBL) depth corrections gave a significant improvement to the PM AOD correlation, which led to similar performance: R(sup 2) = 0.96 for MODIS and R(sup 2) = 0.95 for MAIAC. Furthermore, the introduction of the PBL information in the corrected AOD values was found to be crucial in order to capture the clear seasonal cycle shown by measured PM10 values. The study allowed us to define four seasonal linear correlations that estimate PM10 concentrations satisfactorily from the remotely sensed MAIAC AOD retrieval. Overall, the results show that the high resolution provided by MAIAC retrieval data is much more relevant than 10km MODIS data to characterize PM10 in this region of Italy which has a pretty limited geographical domain, but a broad variety of land usages and consequent particulate concentrations.

MODIS↗
NASA NTRS1974

Preliminary results of the Apollo 17 infrared scanning radiometer

The thermal emission of the lunar surface has been mapped by an infrared scanner from lunar orbit. Samples from approximately 250,000 scans reveal the full range of lunar temperatures from 80 to 400 K. The temperature resolution was 1 K with about plus or minus 2 K absolute precision. Spatial resolution was approximately 2 km over most of the horizon-to-horizon scan. The total mapped area amounted to approximately 30% of the lunar surface. The data currently available confirms the large population of nighttime thermal anomalies in western Oceanus Procellarum predicted by earth-based observations. Most of these 'hot spots' are associated with fresh impact features or boulder fields. Also seen in the data are 'cold spots' where the local nighttime temperature is depressed relative to the general soil background. Such regions exhibiting low surface conductivity are inferred to be relatively young, nonimpact features.

Mendell, W. W.↗
NASA NTRS1981

A comparison of the height distributions of solar flare hard X-rays in thick target and thermal models

Using recent observations of solar hard X-ray bursts having a spatial resolution of a few arcsec, a computation is made of the theoretically predicted spatial variation of hard X-ray flux versus height in both thick target nonthermal and thermal models of solar hard X-ray bursts. The work on the thick target model revises previous results in this area by adopting a more realistic model for the flaring atmospheric structure and also by taking into account energy loss and scattering processes in the evolution of the nonthermal electron beam which have previously been neglected. It is noted that in the so-called 'thermal' model currently in vogue there is a substantial nonthermal bremsstrahlung component at all photon energies; it is further demonstrated that this nonthermal component results in a hard X-ray flux versus height distribution whose maximum brightness per unit length is, similarly to the thick target model, located in the chromosphere and not in the thermal source itself. The characteristics of the hard X-ray height distributions in both thick target and thermal models are summarized and compared.

Emslie, A. G.↗
NASA NTRS1982

Accelerator test of the coded aperture mask technique for gamma-ray astronomy

A prototype gamma-ray telescope employing the coded aperture mask technique has been constructed and its response to a point source of 20 MeV gamma-rays has been measured. The point spread function is approximately a Gaussian with a standard deviation of 12 arc minutes. This resolution is consistent with the cell size of the mask used and the spatial resolution of the detector. In the context of the present experiment, the error radius of the source position (90 percent confidence level) is 6.1 arc minutes.

Jenkins, T. L.↗
NASA NTRS1987

Observational constraints on interchange models at Jupiter

Data from the Voyager plasma science instrument are used to set limits on transport models for the inner Jovian magnetosphere. The instrument has an effective time resolution for detecting changes in density of 0.24 s, which corresopnds to a spatial resolution of about 20 km (equal to the gyroradius of an oxygen ion) in the region just outside of Io. This resolution enables an upper limit of about 10 percent to be set on changes in density between adjacent magnetic flux tubes, which rules out transport models which invoke inward motion of near empty flux tubes to replace outward-moving flux tubes carrying Iogenic plasma.

Richardson, John D.↗
NASA NTRS1991

Global environmental monitoring with the EOS multi-angle imaging spectroradiometer (MISR)

The MISR provides a unique opportunity for studying the ecology and climate of the earth through the acquisition of systematic, global multiangle imagery in reflected sunlight. MISR uses nine cameras: a nadir camera and two banks of four cameras each pointed forward and aftward along the spacecraft ground track to image the earth at +/-30.7, +/-45.6, +/-60.0, and +/-72.5 deg. Radiometrically calibrated images at each angle will be obtained in four spectral bands centered at 440, 550, 670, and 860 nm. MISR will take image data in two different spatial resolution modes: local mode, in which selected targets are observed with 240-m spatial sampling, and global mode, where the entire sunlit eEarth is observed continuously with 1.92-km sampling. The instrument is capable of acquiring global coverage every nine days.

Diner, D. J.↗
NASA NTRS1998

Advanced Water Vapor Lidar Detection System

In the present water vapor lidar system, the detected signal is sent over long cables to a waveform digitizer in a CAMAC crate. This has the disadvantage of transmitting analog signals for a relatively long distance, which is subjected to pickup noise, leading to a decrease in the signal to noise ratio. Generally, errors in the measurement of water vapor with the DIAL method arise from both random and systematic sources. Systematic errors in DIAL measurements are caused by both atmospheric and instrumentation effects. The selection of the on-line alexandrite laser with a narrow linewidth, suitable intensity and high spectral purity, and its operation at the center of the water vapor lines, ensures minimum influence in the DIAL measurement that are caused by the laser spectral distribution and avoid system overloads. Random errors are caused by noise in the detected signal. Variability of the photon statistics in the lidar return signal, noise resulting from detector dark current, and noise in the background signal are the main sources of random error. This type of error can be minimized by maximizing the signal to noise ratio. The increase in the signal to noise ratio can be achieved by several ways. One way is to increase the laser pulse energy, by increasing its amplitude or the pulse repetition rate. Another way, is to use a detector system with higher quantum efficiency and lower noise, on the other hand, the selection of a narrow band optical filter that rejects most of the day background light and retains high optical efficiency is an important issue. Following acquisition of the lidar data, we minimize random errors in the DIAL measurement by averaging the data, but this will result in the reduction of the vertical and horizontal resolutions. Thus, a trade off is necessary to achieve a balance between the spatial resolution and the measurement precision. Therefore, the main goal of this research effort is to increase the signal to noise ratio by a factor of 10 over the current system, using a newly evaluated, very low noise avalanche photo diode detector and constructing a 10 MHz waveform digitizer which will replace the current CAMAC system.

Elsayed-Ali, Hani↗
NASA NTRS1999

Satellite Hyperspectral Imaging Simulation

Simulation of generic pushbroom satellite hyperspectral sensors have been performed to evaluate the potential performance and validation techniques for satellite systems such as COIS(NEMO), Warfighter-1(OrbView-4) and Hyperion(EO-1). The simulations start with a generation of synthetic scenes from material maps of studied terrain. Scene-reflected radiance is corrected for atmospheric effects and convolved with sensor spectral response using MODTRAN 4 radiance and transmissions calculations. Scene images are further convolved with point spread functions derived from Optical Transfer Functions (OTF's) of the sensor system. Photon noise and etectorr/electronics noise are added to the simulated images, which are also finally quantized to the sensor bit resolution. Studied scenes include bridges and straight roads used for evaluation of sensor spatial resolution, as well as fields of minerals, vegetation and manmade materials used for evaluation of sensor radiometric response and sensitivity. The scenes are simulated with various seasons and weather conditions. Signal-to-noise ratios and expected performance are estimated for typical satellite system specifications and are discussed for all the scenes.

Zanoni, Vicki↗
NASA NTRS1999

Satellite Hyperspectral Imaging Simulation

Simulations of generic pushbroom satellite hyperspetral sensors have been performed to evaluate the potential performance and validation techniques for satellite systems such as COIS (NEMO), Warfighter-1 (OrbView-4), and Hyperion (EO-1). The simulaitons start with a generation of synthetic scenes form material maps of studied terrain. Scene-reflected radiance is corrected for atmospheric effects and convolved with sensor spectral response uwing MODTRAN 4 radiance and transmission calculations. Scene images are further convolved with point spread functions derived from Optical Transfer Functions (OTF's) of the sensor system. Photon noise and detector/electronics noise are added to the simulated images, which are also finally quantized to the sensor bit resolution. Studied scenes include bridges and straight roads used for evaluation of sensor spatial resolution, as well as fields of minerals, vegetation, and manmade materials used for evaluation of sensor radiometric response and sensitivity. The scenes are simulated with various seasons and weather conditions. Signal-to-noise ratos and expected performance are estimated for typica satellite system specifications and are discussed for all the scenes.

Zanoni, Vicki↗
NASA NTRS2013

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Castellucci, Matt↗
NASA NTRS2014

Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

Tiwari, S. K.↗
NASA NTRS2016

Titan Science with the James Webb Space Telescope

The James Webb Space Telescope (JWST), scheduled for launch in 2018, is the successor to the Hubble Space Telescope (HST) but with a signicantly larger aperture (6.5 m) and advanced instrumentation focusing on infrared science (0.6-28.0 microns). In this paper, we examine the potential for scientic investigation of Titan using JWST, primarily with three of the four instruments: NIRSpec, NIRCam, and MIRI, noting that science with NIRISS will be complementary. Five core scientic themes are identied: (1) surface (2) tropospheric clouds (3) tropospheric gases (4) stratospheric composition, and (5) stratospheric hazes. We discuss each theme in depth, including the scientic purpose, capabilities, and limitations of the instrument suite and suggested observing schemes. We pay particular attention to saturation, which is a problem for all three instruments, but may be alleviated for NIRCam through use of selecting small sub-arrays of the detectorssufcient to encompass Titan, but with signicantly faster readout times. We nd that JWST has very signicant potential for advancing Titan science, with a spectral resolution exceeding the Cassini instrument suite at near-infrared wavelengths and a spatial resolution exceeding HST at the same wavelengths. In particular, JWST will be valuable for time-domain monitoring of Titan, given a ve- to ten-year expected lifetime for the observatory, for example, monitoring the seasonal appearance of clouds. JWST observations in the post-Cassini period will complement those of other large facilities such as HST, ALMA, SOFIA, and next-generation ground-based telescopes (TMT, GMT, EELT).

Nixon, Conor A.↗
NASA NTRSDate not supplied

Two Decades of Atmospheric and Surface Temperature, Water Vapor, and Cloud Trends Derived from Satellite Remote Sensors

Satellite remote sensor such as Atmospheric Infrared Sounder (AIRS), Cross-track Infrared Sounder (CrIS), and Infrared Atmospheric Sounding Interferometer (IASI) provide high-quality atmospheric temperature, water, vapor, and greenhouse gas vertical profiles. Additionally, they provide atmospheric cloud properties, surface emissivity, and surface skin temperatures. We have developed two algorithms which can consistently derive these products from multiple IR sounders. The first one is a Single Field-of-view Sounder Atmospheric Product (SIFSAP) algorithm and the second one is a Climate Fingerprinting Sounder Product (ClimFiSP) algorithm. Compared to current operational AIRS and CrIS Level-2 (L2) algorithms, which perform one retrieval for each 3 by 3 field of views (FOVs) using a cloud-clearing approach, the SiFSAP algorithm, on the other hand, performs one retrieval for each FOV using an all-sky optimal estimation approach. The SiFSAP algorithm retrieves all the above-mentioned atmosphere and surface properties simultaneously including cloud properties with 3-time higher spatial resolution and 9-times more products. Climate products are typically derived by performing spatial and temporal averaging of L2 products. It is a time-consuming process to generate L2 data products since AIRS, CrIS, and IASI have millions of observations each day with thousands of spectral channels for each observation. Additionally, differences in L2 retrieval algorithms for different satellite sensors can lead to errors in the climate products. Our ClimFiSP algorithm, which performs retrievals from spatiotemporally averaged L1 hyperspectral radiances directly, will be orders of magnitude faster than traditional method. he ClimFiSP algorithm uses consistent radiative kernels and a robust spectral fingerprinting method. It provides accurate data climate data fusion products from multiple satellite sensors. We have applied this method to both AIRS and CrIS (on SNPP and on NOAA 20) data and generated two decades climate data records for atmospheric temperature, water vapor, cloud, trace gases, and surface skin temperature. Both SiFSAP and ClimFiSP will be available at NASA GES DISC data center for public access.

remote sensing↗
NASA NTRS1999

High Resolution Optical/Near-Infrared Imaging of Cool Ultraluminous Infrared Galaxies

We present here new multiwavelength observations with 1.5 and 4x the spatial resolution of previous ground-based observations at optical and near-infrared wavelengths; despite being ground-based, they allow us to isolate interesting features such as the star-forming knots detected in the warm ULIG sample.

near-infrared cool ultraluminous infrared galaxies↗