SEARCH · Engineering Papers

Results for “LaS”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Development of an intelligent interface for adding spatial objects to a knowledge-based geographic information system

Earth Scientists lack adequate tools for quantifying complex relationships between existing data layers and studying and modeling the dynamic interactions of these data layers. There is a need for an earth systems tool to manipulate multi-layered, heterogeneous data sets that are spatially indexed, such as sensor imagery and maps, easily and intelligently in a single system. The system can access and manipulate data from multiple sensor sources, maps, and from a learned object hierarchy using an advanced knowledge-based geographical information system. A prototype Knowledge-Based Geographic Information System (KBGIS) was recently constructed. Many of the system internals are well developed, but the system lacks an adequate user interface. A methodology is described for developing an intelligent user interface and extending KBGIS to interconnect with existing NASA systems, such as imagery from the Land Analysis System (LAS), atmospheric data in Common Data Format (CDF), and visualization of complex data with the National Space Science Data Center Graphics System. This would allow NASA to quickly explore the utility of such a system, given the ability to transfer data in and out of KBGIS easily. The use and maintenance of the object hierarchies as polymorphic data types brings, to data management, a while new set of problems and issues, few of which have been explored above the prototype level.

Campbell, William J.↗

NASA NTRS1988

The Laboratory for Oceans Computing Facility

The first VAX computer in the Laboratory for Oceans Computing Facility (LOCF) was installed and the facility was largely expanded. The growth is not only in hardware and software, but also in the number of users and in supporting research and development projects. The LOCF serves as a general purpose computing facility for: ocean color research projects, sea ice research projects, processing of the Nimbus-7 Coastal Zone Color Scanner data set, real time ingest and analysis of TIROS-N satellite data, study of the Synthetic Aperture Radar data, study of LANDSAT data, and many others. The physical space and the electrical power layout of the computing room were modified to accommodate all the equipment. The LOCF has several image processing stations which include two International Imaging Systems (IIS) model 75 processors and one Adage processor. The facility has the capability of ingesting the TIROS-N HRPT satellite data on a real time basis. More than 30 software packages were installed on the systems. System software packages, network software, FORTRAN and C compilers, database management software, image processing software, graphics, mathematics and statistics packages, TAE, Catalog Manager, GEMPAK, LAS and many other software developed on the LOCF computers such as SEAPAK have greatly advanced the capability of the LOCF.

Kao, R.↗

NASA NTRS1988

Millisecond optical photometry of the DQ Herculis objects

The results of millisecond optical photometry of the DQ Herculis stars EX Hya, H2252-035, V1223 Sgr, and AE Aqr obtained at the Las Campanas Observatory and Cerro Tololo Inter-American Observatory during the years 1985, 1986, and 1987 are reported. The data for coherent and incoherent features are searched for. Coherent features (other than those previously known) were not detected for frequencies between 0.1 and 250 Hz at 4-sigma upper limits of 0.05-0.4 percent. Evidence is not found for 1-3 s, quasi-coherent features. Such features have been detected in the optical emission of the AM Her objects AN UMa, EF Eri, and E1405-451. Because of the similarities between AM Her and DQ Her objects, it was suggested that such quasi-coherent features might also be found in the DQ Her objects.

Imamura, James N.↗

NASA NTRS1989

High-speed optical photometry of the DQ Herculis object H2215-086

The paper presents the results of high-time-resolution white-light photometry of H2215-086 obtained at Las Campanas Observatory and Cerro Tololo Inter-American Observatory during 1985-1987. Descriptions of periodic features, including power spectra due to rotational and orbital modulation, are presented as well as quasi-periodic features. It is found that H2215-086 displays large-amplitude modulations in its optical, IR, and X-ray emission on the 20.9 min rotational period of the white dwarf. Possible sites for this emission are discussed.

Steiman-Cameron, Thomas Y.↗

NASA NTRS1989

Population studies in groups and clusters of galaxies. II - A catalog of galaxies in the central 3.5 deg of the Fornax Cluster

A catalog of 2678 galaxies within an area of about 40 sq deg centered on the Fornax Cluster has been compiled based on 26 deep large-scale plates obtained with the 2.5-m Las Campanas Observatory reflector. The catalog includes 340 likely cluster members and 2338 likely background galaxies. Radial velocities are given for 89 of the galaxies. The spatial distributions of various types of galaxies have been modeled as the sum of a King (1962) model cluster component superimposed on a uniform background. Using maximum-likelihood fits to these distributions, a core radius of 0.7 deg is found for a King model fit to the cluster, suggesting that there are few cluster members contained in the sample of background galaxies.

Ferguson, Henry C.↗

NASA NTRS1989

Aerosol in the Pacific troposphere

The use of near real-time optical techniques is emphasized for the measurement of mid-tropospheric aerosol over the Central Pacific. The primary focus is on measurement of the aerosol size distribution over the range of particle diameters from 0.15 to 5.0 microns that are essential for modeling CO2 backscatter values in support of the laser atmospheric wind sounder (LAWS) program. The measurement system employs a LAS-X (Laser Aerosol Spectrometer-PMS, Boulder, CO) with a custom 256 channel pulse height analyzer and software for detailed measurement and analysis of aerosol size distributions. A thermal preheater system (Thermo Optic Aerosol Descriminator (TOAD) conditions the aerosol in a manner that allows the discrimination of the size distribution of individual aerosol components such as sulfuric acid, sulfates and refractory species. This allows assessment of the relative contribution of each component to the BCO2 signal. This is necessary since the different components have different sources, exhibit independent variability and provide different BCO2 signals for a given mass and particle size. Field activities involve experiments designed to examine both temporal and spatial variability of these aerosol components from ground based and aircraft platforms.

Clarke, Antony D.↗

NASA NTRS1990

A 190 second periodicity in the optical emission of the enigmatic X-ray source GX 339-4

The results are reported of submillisecond white-light optical photometry of the X-ray source GX 339-4 obtained over the years 1985-1988 at the Las Campanas Observatory and Cerro Tololo Inter-American Observatory. A coherent, df/f less than 0.025, 5.25 mHz feature with pulsed amplitude up to 50 percent is found which persisted for about 20-30 cycles. The feature only appeared in data taken in July 5, 1986 UT. The 885 Hz feature proposed by Imamura et al. (1990) was not detected at 90-percent-confidence upper limits of 2 percent pulsed emission. The 885 Hz feature was reported by Imamura et al. to have a pulsed amplitude of 2.3-2.4 percent. The proposed 0.2 mag, 0.618 day orbital variation proposed by Honey et al. (1988) could not be verified due to the length of the data strings.

Steiman-Cameron, T.↗

NASA NTRS1992

Dynamics of the young LMC cluster NGC 1866

The 1.0-m telescope at Las Campanas was used to obtain V-band CCD images of the young LMC cluster NGC 1866 out to a projected radius of 100 pc. Radial velocities with a mean precision of 1.0 km/s were measured for 69 member supergiants using the echelle spectrograph on the 2.5-m telescope. The total cluster luminosity is 6.5 +/-0.3 x 10 exp 5 solar luminosities. A star-subtracted, median-filtered U frame was employed to determine photometric shape parameters. The stellar radial velocities indicate that NGC 1866 has a systemic velocity of 301.2 +/-1.0 km/s. A comparison of the derived values for NGC 1866 and the theoretical nu-0/sigma-0 - epsilon relationship indicates that the observed flattening is consistent with rotation. The quality of the fits for models with rotation is clearly superior to those without, and isotropic orbits agree best with the data in both cases.

Fischer, Philippe↗

NASA NTRS1992

A multiwavelength study of the supernova remnant N49 in the Large Magellanic Cloud

The 2.5-m du Pont telescope at Las Campanas, the IUE, and archival high-resolution imager X-ray data from the Einstein Observatory are used to present a detailed imaging and spectroscopic study of the SNR N49 in the LMC. The asymmetry of the optical image and the relatively high X-ray and optical luminosity of this remnant both arise from its interaction with an extended dense cloud to the southeast seen in CO emission. The optical spectra reveal clear evidence of reddening variations on spatial scales as small as about 2 arcsec over the face of the SNR. UV line emission is associated primarily with the bright optical filaments, and the total luminosity of N49 is measured in several optical and UV lines. A combined analysis of IUE and optical spectra indicates a range of radiative shock velocities. Implications for the interstellar medium surrounding N49 are discussed.

Vancura, Olaf↗

NASA NTRS1993

Standardization work for the calibration of intensities of celestial objects

Observations of celestial phenomena need to be calibrated, to be related, to some measurable quantity. There continues to be a long-term need for accurate photometric standard stars, those with known intensities and colors, so that brightness and color measurements made of various celestial phenomena by different observers can be integrated and compared with one another. Toward this end, the author has been emphasizing data collection in recent years for stars of 'intermediate' brightness, those approximately in the magnitude range 11.5 is less than V is less than 16.0. Photoelectric data were obtained at the Cerro Tololo InterAmerican Observatory's (CTIO) telescopes for stars in certain selected areas near the celestial equator. Stars of extreme color outside the selected areas, but near the equator, also were selected to provide a more broad and complete range in color index. It was proposed to complete the photoelectric phase of the program. The author proposed developing extremely faint sequences of photometric standard stars useful for both large space-based detectors and for land-based detectors. These data were to be collected via charge-coupled devices (CCD's) at telescopes located at CTIO and at the Las Campanas Observatory (LCO), both observatories being located in Chile. It was hoped that accurate data could be collected down to the 21st or 22nd magnitude.

Landolt, Arlo U.↗

NASA NTRS1993

Distant radio galaxies in the near IR

We are carrying out a program of near IR imaging and spectroscopy of radio galaxies with redshifts of 1.5 and greater. One of its principal goals is to constrain the ages and star formation histories of massive galaxies at early epochs. The radio galaxies are drawn from the survey of 1Jy class sources by McCarthy et al (1989) and McCarthy (1990). The sample contains 18 radio galaxies with redshifts greater than 2 and an additional 10 objects with 1.5 less than z less than 2.0. The redshifts were obtained from long slit spectra with the CTIO 4 m. While the galaxies are quite faint (r approximately = 21-24.5) all have Lyman alpha emission with rest frame equivalent widths of 100 - 1000 A. Multicolor photometry in the g,r,i and J,H,K bands has been obtained with the 2.5-m Du Pont Telescope on Las Campanas and with the Hale 5 m telescope at Palomar. We have recently obtained near IR spectra, using the 4 m telescopes at KPNO and CTIO, of a few objects with the goal of determining the Lyman alpha/H-alpha ratio and hence the reddening.

Mccarthy, P. J.↗

NASA NTRS1993

Extremely red objects in the fields of high redshift radio galaxies

We are engaged in a program of infrared imaging photometry of high redshift radio galaxies. The observations are being done using NICMOS2 and NICMOS3 arrays on the DuPont 100-inch telescope at Las Campanas Observatory. In addition, Persson and Matthews are measuring the spectral energy distributions of normal cluster galaxies in the redshift range 0 to 1. These measurements are being done with a 58 x 62 InSb array on the Palomar 5-m telescope. During the course of these observations we have imaged roughly 20 square arcminutes of sky to limiting magnitudes greater than 20 in the J, H, and K passbands (3 sigma in 3 square arcseconds). We have detected several relatively bright, extremely red, extended objects during the course of this work. Because the radio galaxy program requires Thuan-Gunn gri photometry, we are able to construct rough photometric energy distributions for many of the objects. A sample of the galaxy magnitudes within 4 arcseconds diameter is given. All the detections are real; either the objects show up at several wavelengths, or in subsets of the data. The reddest object in the table, 9ab'B' was found in a field of galaxies in a rich cluster at z = 0.4; 9ab'A' lies 8 arcseconds from it.

Persson, S. E.↗

NASA NTRS1992

An RR Lyrae period shift in terms of the Fourier parameter Phi sub 31

The Fourier phase parameter Phi sub 31 has been determined for RRc stars in five globular clusters, NGC 6171, M5, M3, M53, and M15. The results indicate that the RRc stars in a given cluster show a sequence of Phi sub 31 increasing with period, and that the higher the cluster metallicity, the higher the sequence lies in a plot of Phi sub 31 with period. The Phi sub 31 values for the stars in NGC 6171 and M5 presented here are based on observations made with the University of Toronto 0.61 m telescope at Las Campanas, Chile, while those for M3, M53, and M15 are based on published data. A bootstrap procedure has been used to establish the uncertainties in the Fourier parameters. The physical significance of the relationship among Phi sub 31, period, and metallicity is not yet understood. It will need to be tested with hydrodynamic pulsation models computed with new opacities.

Clement, Christine M.↗

NASA NTRS1993

The RR Lyrae variables in the globular cluster M68

New observations, made with the Helen Sawyer Hogg telescope at Las Campanas, have been analyzed in a search for double-mode pulsators (RRd stars) in the metal-poor globular cluster, Messier 68. Of the 30 stars studied, nine have been identified as RRd stars; V33, which exhibited the characteristics of an RRd star in 1950, now appears to be an RRc star. Reliable periods and period ratios have been determined for six of the RRd stars. Masses for these RRd stars, calculated from fitting formulas given by Kovacs et al. (1991), range from 0.75 to 0.90 solar mass, depending on the assumed luminosity and metal abundance. These masses are in the same range as those for the RRd stars in M 15, whose RRd sample resembles that of M68 very closely. Fourier parameters determined for the light curves of the M68 variables show that the RRc stars in the two clusters are also very similar. In particular, on the plot of phase parameter phi sub 31 with period, the M15 and M68 RRc samples are virtually indistinguishable. A comparison of the new M68 observations with observations made 40 yr ago shows that the periods of some of the stars have changed, but the 40 yr interval is too short for detecting period changes caused by evolutionary effects.

Clement, Christine M.↗

NASA NTRS1994

Gas-grain simulation facility: Aerosol and particle research in microgravity

This document reports on the proceedings of the Gas-Grain Simulation Facility (GGSF) Science Workshop which was co-hosted by NASA Ames Research Center and Desert Research Institute, University of Nevada System, and held in Las Vegas, Nevada, on May 4-6, 1992. The intent of the workshop was to bring together the science community of potential GGSF experimenters, Science Working Group and staff members, and the Phase A contractor to review the Phase A design with the science participants and to facilitate communication between the science community and the hardware developers. The purpose of this report is to document the information disseminated at the workshop, to record the participants' review of the Phase A GGSF design concept and the current science and technical requirements for the Facility, and to respond to any questions or concerns that were raised at the Workshop. Recommendations for the future based on numerous discussions with the participants are documented, as well as science presentations and poster sessions that were given at the Workshop and a summary of 21 candidate experiments.

Huntington, Judith L.↗

NASA NTRS1994

Canopy reflectance modelling of semiarid vegetation

Three different types of remote sensing algorithms for estimating vegetation amount and other land surface biophysical parameters were tested for semiarid environments. These included statistical linear models, the Li-Strahler geometric-optical canopy model, and linear spectral mixture analysis. The two study areas were the National Science Foundation's Jornada Long Term Ecological Research site near Las Cruces, NM, in the northern Chihuahuan desert, and the HAPEX-Sahel site near Niamey, Niger, in West Africa, comprising semiarid rangeland and subtropical crop land. The statistical approach (simple and multiple regression) resulted in high correlations between SPOT satellite spectral reflectance and shrub and grass cover, although these correlations varied with the spatial scale of aggregation of the measurements. The Li-Strahler model produced estimated of shrub size and density for both study sites with large standard errors. In the Jornada, the estimates were accurate enough to be useful for characterizing structural differences among three shrub strata. In Niger, the range of shrub cover and size in short-fallow shrublands is so low that the necessity of spatially distributed estimation of shrub size and density is questionable. Spectral mixture analysis of multiscale, multitemporal, multispectral radiometer data and imagery for Niger showed a positive relationship between fractions of spectral endmembers and surface parameters of interest including soil cover, vegetation cover, and leaf area index.

Franklin, Janet↗

NASA NTRS1994

The initial mass function for massive stars in the Magellanic Clouds. 1: UBV photometry and color-magnitude diagrams for 14 OB associations

UBV charge coupled device (CCD) photometry has been obtained for 14 OB associations in the Magellanic Clouds using the University of Toronto's 0.6 m telescope and the Carnegie Institution of Washington's 1.0 m reflector, both on Las Campanas, Chile. The data are presented and used to construct color-magnitude diagrams for the purposes of investigating the massive-star content of the associations.

Hill, Robert J.↗

NASA NTRS1992

Nondestructive monitoring damage in composites using scanning laser acoustic microscopy

Several Nicalon fiber reinforced LAS (lithium alumino-silicate) glass matrix composites were tested to study the relation between the residual strength and the different amounts of damage. The samples were fatigued by four-point cyclic loading at a 5 Hz rate at 500 C for a different number of cycles. 10 MHz scanning laser acoustic microscope (SLAM) images were taken to monitor damage on the samples. Our SLAM results indicate that there were defects already existing throughout the sample before fatigue, and the resultant damage pattern from fatigue could be related to the initial defect distribution in the sample. Finally, the fatigued samples were fractured and the residual strength data could not be explained by the cyclic fatigue alone. Rather, the damage patterns evident in the SLAM images were needed to explain the scatter in the data. The results show that SLAM is useful in nondestructively monitoring damage and estimating residual strength of fatigued ceramic composites.

Wey, A. C.↗