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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Use of ERTS-1 pictures in coastal oceanography in British Columbia

The ERTS-1 color composite picture of the Vancouver-Victoria region illustrates the value of ERTS data for coastal oceanography. The water of the Fraser River plume which is so clearly visible in the center of the scene has been of interest to oceanographers on the west coast of Canada for a long time as an easily visible tracer of surface water circulation in the strait of Georgia. Maps of the plume at different states of the tide and with different river flow and weather were compiled from oblique aerial photographs in 1950 and used in the siting of sewage and other outfalls in the Vancouver area. More recently high level aerial photomosaics have been used to map the plume area, but the plume can spread over distances of 30 to 40 miles and many photographs, with the uneven illumination inherent in wide angle coverage, are needed for the mosaic. The ERTS satellite gives the first complete view of the plume area. Electronic enhancement of the images shows that the satellite's narrow angle coverage allows very weak surface turbidity features to be made visible to give information on surface currents over a wide area.

Gower, J. F. R.↗
NASA NTRS1995

Nature and location of the source of plasma sheet boundary layer ion beams

Onsager et al. (1991) have put forward a model of the formation of the plasma sheet boundary layer (PSBL) which relies on a steady source of plasma from a spatially extended plasma sheet, together with steady equatorward and earthward ExB convection of field lines due to reconnection at a downtail neutral line. This model is a synthesis of earlier proposals and it explains such features as an electron layer exterior to the ion boundary layer, ion velocity dispersion, counter streaming beams, low-speed cutoffs in the beams. It also explains the apparent evolution of the ion beams through 'kidney bean' shaped velocity-space distributions toward quasi-isotropic shells without invoking pitch angle scattering or energy diffusion. In this paper we explore two ramifications of the model. In principle we can map, as a function of time, the downtail neutral line distance and establish whether or not it is retreating during substorm recovery. We can also reconstruct the plasma distribution function near the neutral line to see if it is most consistent with mantle or plasma sheet plasma. We perform this analysis using International Sun Earth Explorer (ISEE) Fast Plasma Experiment (FPE) data for two plasma sheet recovery events, one on March 1, 1978, and the other on April 18, 1978. On March 1, 1978, we find evidence for an initial retreat from around 110 to 160 R(sub E) in the first 15 min; little further retreat occurs thereafter. On April 18, 1978, the neutral line location ranges from as little as 40 R(sub E) tailward of the satellite to as much as 200 R(sub E), but there is no evidence for a systematic retreat. The reconstructed ion distributions for these events are most consistent with a plasma sheet origin for the March 1 case and possibly plasma mantle or low-latitude boundary layer for the April 18 case.

Elphic, R. C.↗
NASA NTRS1995

ROSAT observations of the supernova remnant 3C 400.2

We have used the ROSAT point source proportional counter (PSPC) to examine the X-ray emission from 3C 400.2, a supernova remnant (SNR) which is a member of a class of remnants with limb-brightened radio and centrally condensed X-ray morphologies. The X-ray emission fills the radio shell and is characterized by an interior peak in the northwest region of the remnant. Otherwise, the surface brightness has a relatively smooth distribution. The X-ray peak is not correlated with any radio features or with the observed optical filaments. The PSPC X-ray spectrum is not well fitted by a power-law model but can be described in terms of thermal emission from a hot plasma with solar abundances. The only point source along the line of sight to the SNR is associated with a bright foreground F8 star. Thus the X-ray emission from 3C 400.2 is unlikely to be due to synchrotron radiation from an active pulsar. If the emission arises from a thermal plasma and the absorbing column along the line of sight to 3C 400.2 is 7.8 x 10(exp 21)sq cm, then the temperature of the plasma is 0.27 keV, and the 0.4-2.4 keV X-ray luminosity is 1.3 x 10(exp 36) ergs/s for an assumed distance of 6 kpc. An X-ray hardness ratio map shows a slight increase in the hardness of the emission in the regions of the remnant with a higher X-ray surface brightness. Assuming uniform absorption across the remnant, this increase implies the temperature is approximately 1.5 times greater in the high surface brightness regions of SNR. The relatively uniform spectrum and the anticorrelation between X-ray and radio features seems to rule out the possibility that 3C 400.2 is actually two overlapping or interacting SNRs. The morphology of 3C 400.2 can be explained in terms of a multiphase interstellar medium (ISM) in which the primary shock is expanding into an ISM studded with dense cloudlets, if the clouds are evaporated or disrupted on a timescale which is long compared to the age of the SNR. It may also be possible to explain the emission in terms of the interaction of the SNR with a massive wind-driven shell, although the existing models for the evolution of A SNR in this environment suggest that the H-alpha luminosity should be much larger than the X-ray luminosity, which is not observed. We cannot completely rule out the possibility that 3C 400.2's appearance as a centrally peaked X-ray SNR is the result of an interaction between the remnant and a cloud along the line of sight, although this seems unlikely.

Saken, Jon M.↗
NASA NTRS1995

Acceleration phenomena of high-speed wind observed at 0.1-0.3 AU with interplanetary scintillation

The radial distance dependence of solar wind speeds, which were measured by interplanetary scintillation method, has been studied especially for a high-speed solar wind, and large increase of the IPS speeds (300 km/s) was observed at the distance range of 0.1 - 0.3 AU. When the streams are mapped back onto the source surface, they distribute in polar coronal holes or their boundaries. Since the IPS measurement can be biased by several effects such as of line-of-sight integration, strong scattering and random velocities, we examined these biasing effects and have found difficulty to explain the large IPS speed increase with the biasing effects.

Kojima, M.↗
NASA NTRS2000

Global Patterns of Precipitation Anomalies Related to ENSO as Determined by the 20-Year GPCP Analysis

The new 20-year, monthly, globally complete precipitation analysis of the Global Precipitation Climatology Project (GPCP) is used to analyze ENSO-related precipitation anomalies over the globe. This Version 2 of the community generated data set is global, monthly, at 2.5 deg x 2.5 deg latitude-longitude resolution and utilizes precipitation estimates from low-orbit microwave sensors (SSM/I) and geosynchronous IR sensors and raingauge information over land. In the 1987-present period the low-orbit microwave (SSM/I) estimates are used to adjust or correct the geosynchronous IR estimates, thereby maximizing the utility of the more physically-based microwave estimates and the finer time sampling of the geosynchronous observations. Information from raingauges is blended into the analyses over land. The extension back to 1979 utilizes the OLR Precipitation Index (OPI) for the satellite component. An ENSO Precipitation Index (ESPI) using gradients of precipitation anomalies in the Maritime-Continent/Pacific Ocean region is used to define El Nino/La Nina months during the 20-year record. Mean anomalies for El Nino and La Nina are examined along with variations with respect to season and for individual events. The El Nino and La Nina mean anomalies are near mirror images of each other and when combined produce an ENSO signal with significant spatial continuity over large distances. This El Nino minus La Nina standardized precipitation anomaly map shows the usual positive anomaly over the central and eastern Pacific Ocean with the negative anomaly over the maritime continent along with an additional negative anomaly over Brazil and the Atlantic Ocean extending into Africa and a positive anomaly over the Horn of Africa and the western Indian Ocean. From these features along the Equator narrow positive and negative anomalies extend into middle latitudes in a V-shaped pattern open to the East as described by previous investigators. A number of the features are shown to continue into high latitudes. Positive anomalies extend in the Southern Hemisphere (S.H.) from the Pacific southeastward across Chile and Argentina into the south Atlantic Ocean. In the Northern Hemisphere (N.H.) the counterpart feature extends across the southern U.S. and Atlantic Ocean into Europe. Further to the west a negative anomaly extends southeastward again from the Maritime Continent across the South Pacific and through the Drake Passage. The N.H. counterpart crosses the North Pacific and southern Canada. Other features seemingly extend into Antarctica and into the Arctic Ocean.

Adler, Robert↗
NASA NTRS2011

Tropospheric Correction for InSAR Using Interpolated ECMWF Data and GPS Zenith Total Delay

To mitigate atmospheric errors caused by the troposphere, which is a limiting error source for spaceborne interferometric synthetic aperture radar (InSAR) imaging, a tropospheric correction method has been developed using data from the European Centre for Medium- Range Weather Forecasts (ECMWF) and the Global Positioning System (GPS). The ECMWF data was interpolated using a Stretched Boundary Layer Model (SBLM), and ground-based GPS estimates of the tropospheric delay from the Southern California Integrated GPS Network were interpolated using modified Gaussian and inverse distance weighted interpolations. The resulting Zenith Total Delay (ZTD) correction maps have been evaluated, both separately and using a combination of the two data sets, for three short-interval InSAR pairs from Envisat during 2006 on an area stretching from northeast from the Los Angeles basin towards Death Valley. Results show that the root mean square (rms) in the InSAR images was greatly reduced, meaning a significant reduction in the atmospheric noise of up to 32 percent. However, for some of the images, the rms increased and large errors remained after applying the tropospheric correction. The residuals showed a constant gradient over the area, suggesting that a remaining orbit error from Envisat was present. The orbit reprocessing in ROI_pac and the plane fitting both require that the only remaining error in the InSAR image be the orbit error. If this is not fulfilled, the correction can be made anyway, but it will be done using all remaining errors assuming them to be orbit errors. By correcting for tropospheric noise, the biggest error source is removed, and the orbit error becomes apparent and can be corrected for

Webb, Frank H.↗
NASA NTRS2017

Boulders on Ceres

Introduction: In December 2015 the Dawn spacecraft moved into the Low Altitude Mapping Orbit (LAMO) around Ceres, encircling the dwarf planet at a distance of 400 km to the surface below. At this altitude, images of the on-board framing camera have a resolution of 36 meters per pixel, high enough to distinguish large boulders on the surface. Indeed, LAMO images show a multitude of boulders around what seem to be fresh craters. The average life-time of boulders on Dawn's previous target, Vesta, was estimated to be similar to that of Lunar boulders, as may be expected from the basaltic surface composition. The bulk composition of Ceres may be carbonaceous chondrite-like with significant contributions of clays, salt, and water ice. As such, the abundance and distribution of boulders on Ceres may be different from that on Vesta. We mapped, counted, and measured the diameter of boulders over the entire surface of Ceres. Our analysis of the data in combination with crater age estimates may provide clues to the physical nature and composition of the surface.

Ceres↗
NASA NTRS1996

Galactic Abundance Gradients fro IR Fine Strucuture LInes in Compact H II regions

We present observations of the [S III]19(micro)m, [O III]52 and 88(micro)m, and [N III]57(micro)m lines toward 18 compact and ultracompact (UC) H II regions. These data were combined with data from the literature and high-resolution radio continuum maps to construct detailed statistical equilibrium and ionization equilibrium models of 34 compact H II regions located at galactocentric distances (Dg)0-12kpc. Our models simultaneously fit the observed IR fine-structure lines and high-resolution radio continuum maps.

galactic elements chemical evolution galaxy format↗
NASA NTRS1997

Precision Thickness Variation Mapping via One-Transducer Ultrasonic High Resolution Profilometry for Sample with Irregular or Rough Surface

An apparatus and method for determination of sample thickness and surface depression utilizing ultrasonic pulses. The sample is held in a predetermined position by a support member having a reference surface. Ultrasonic pulses travel through a medium of known velocity propagation and reflect off the reference surface and a sample surface. Time of flight data of surface echoes are converted to distances between sample surfaces to obtain computer-generated thickness profiles and surface mappings.

Roth, Don J.↗
NASA NTRS1996

Precision Thickness Variation Mapping Via One-Transducer Ultrasonic High Resolution Profilometry for Sample With Irregular or Rough Surface

An apparatus and method for determination of sample thickness and surface depression utilizing ultrasonic pulses is discussed. The sample is held in a predetermined position by a support member having a reference surface. Ultrasonic pulses travel through a medium of known velocity propagation and reflect off the reference surface and a sample surface. Time of flight data of surface echoes are converted to distances between sample surfaces to obtain computer-generated thickness profiles and surface mappings.

Roth, Don J.↗
NASA NTRS1990

Mapping unstructured grid problems to the connection machine

We present a highly parallel graph mapping technique that enables one to solve unstructured grid problems on massively parallel computers. Many implicit and explicit methods for solving discretizated partial differential equations require each point in the discretization to exchange data with its neighboring points every time step or iteration. The time spent communicating can limit the high performance promised by massively parallel computing. To eliminate this bottleneck, we map the graph of the irregular problem to the graph representing the interconnection topology of the computer such that the sum of the distances that the messages travel is minimized. We show that, in comparison to a naive assignment of processors, our heuristic mapping algorithm significantly reduces the communication time on the Connection Machine, CM-2.

Hammond, Steven W.↗
NASA NTRS2013

Method for Enhancing a Three Dimensional Image from a Plurality of Frames of Flash LIDAR Data

A method for enhancing a three dimensional image from frames of flash LIDAR data includes generating a first distance R(sub i) from a first detector i to a first point on a surface S(sub i). After defining a map with a mesh theta having cells k, a first array S(k), a second array M(k), and a third array D(k) are initialized. The first array corresponds to the surface, the second array corresponds to the elevation map, and the third array D(k) receives an output for the DEM. The surface is projected onto the mesh theta, so that a second distance R(sub k) from a second point on the mesh theta to the detector can be found. From this, a height may be calculated, which permits the generation of a digital elevation map. Also, using sequential frames of flash LIDAR data, vehicle control is possible using an offset between successive frames.

Vanek, Michael D.↗
NASA NTRS1972

Program of solar wind data analysis utilizing data from Pioneer 6, Mariner 5 and explorer 35

A combined data analysis and theoretical program aimed at interpreting and utilizing solar wind data obtained from Pioneer 6, Mariner 5, and Explorer 35 has been completed. A theoretical model of the radial dependence of large scale solar wind inhomogeneities was developed and used to map solar wind variations measured by Explorer 35 to various heliocentric distances and to the orbits of Mercury, Venus, and Mars. The model was also used to determine power spectra velocity, density and temperature variations of 20 R sub s from spectra obtained from the Mariner 5 data at an average heliocentric distance of 180 R sub s. Five stream-stream interaction events in the Pioneer 6 data were analyzed which confirmed the picture of a spiral compression ridge interfacing the two streams and the associated east-west deflections of the solar wind flow. Magnetopause crossings observed in Explorer 35 plasma data were used to develop statics on boundary motions at lunar distance. A study of the geomagnetic disturbance field asymmetry was performed and a model of disturbance field from a partial ring current was developed.

Siscoe, G. L.↗
NASA NTRS1984

Radio and UV Observations of High Latitude HI

Interstellar Lyman alpha observations toward high latitude stars, which give the column density of H I between Earth and the star, and 21 cm radio observations, which give the total H I column density to and beyond the star, can be combined to map out the amount of neutral gas as a function of distance from the Sun. Observations of the 21 cm and Lyman alpha lines made toward approximately 50 high latitude OB stars are presented. These data are used to discuss the distribution of H I in the solar neighborhood.

Lockman, F. J.↗
NASA NTRS1996

The interstellar medium and the soft X-ray background

The soft X-ray background (SXRB) surface brightness provides data to study the approximately 10(exp 6) K plasma of the local interstellar medium of our Galaxy. Various studies were carried out in order to search for negative correlation, or shadowing, of the SXRB, and were coupled with interstellar medium absorption line studies. The purpose was to determine whether the distances to the shadowing material will lead to a three dimensional mapping of the X-ray emitting, and X-ray absorbing components.

Snowden, S. L.↗
NASA NTRS2017

Space Exploration

New range Passage Tomb may be the first structure with known astronomical significance. It was built around 3,200 B.C. in Ireland. It's central passage allows light end-to-end for about 2 weeks around winter solstice. The Sun, Moon, Planets, and Stars held significance in early times due to the seasons, significance for food crops, and mythology. Citation: Corel Photography and Windows to the Universe The Greek may be among the first to pursue analytical interpretations of what they saw in the sky. In about 280 B.C. Aristarchus suggested Earth revolves around the Sun and estimated the distance between. Around 130 B.C. Hipparchus developed the first accurate star map. Today still seek to understand how the universe formed and how we came to be and are we alone. Understanding the causes and consequences of climate change using advanced space missions with major Earth science and applications research. center dotFire the public imagination and inspire students to pursue STEM fields. Train college and graduate students to create a U.S. technical workforce with employees that embody the values of competence, innovation, and service. center dotDrive the technical innovations that enable exploration and become the engine of National economic growth. center dotPartner domestically and internationally to leverage resources to extend the reach of research.

space↗
NASA NTRS2016

Euclid Near Infrared Spectro Photometer instrument concept and first test results obtained for different breadboards models at the end of phase C

The Euclid mission objective is to understand why the expansion of the Universe is accelerating through by mapping the geometry of the dark Universe by investigating the distance-redshift relationship and tracing the evolution of cosmic structures. The Euclid project is part of ESA's Cosmic Vision program with its launch planned for 2020 (ref [1]). The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments and is operating in the near-IR spectral region (900- 2000nm) as a photometer and spectrometer. The instrument is composed of: - a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly (corrector and camera lens), a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control system - a detection subsystem based on a mosaic of 16 HAWAII2RG cooled to 95K with their front-end readout electronic cooled to 140K, integrated on a mechanical focal plane structure made with molybdenum and aluminum. The detection subsystem is mounted on the optomechanical subsystem structure - a warm electronic subsystem (280K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data This presentation describes the architecture of the instrument at the end of the phase C (Detailed Design Review), the expected performance, the technological key challenges and preliminary test results obtained for different NISP subsystem breadboards and for the NISP Structural and Thermal model (STM).

Maciaszek, Thierry↗
NASA NTRS1999

Lightning First Pulses Used in the "Last" (Time-of-Arrival) and "Atlas" (Single Station) Total Lightning Mapping Systems

The first RF pulse from "total lightning' discharges (cloud and ground flashes) has been used in different ways to locate the origin of flashes in two new types of lightning detection systems. The multisensor LASI time-of-arrival (TOA) system uses GPS timing of the first pulse. The ATLAS single sensor system uses the amplitude of the first pulse, which is invariant in magnitude and polarization for all lightning discharges, to determine distance from the sensor. It is significantly more accurate than past single sensor lightning mapping systems. The polarity of the first pulse generally identifies lightning type (IC or CG). Both systems utilize only the first pulse which makes signal processing much simpler than with previous lightning locating systems. Knowing the position where lightning begins (maximum electric fields, mixed phase hydrometeors and updrafts) is valuable for identifying convective cells producing the hazardous meteorological conditions caused by thunderstorms. It is also important for research studying thunderstorm electrification and associated microphysical problems.

Markson, Ralph↗