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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 199 records · Page 11
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NASA NTRS1990

First images of water vapor masers in the galaxy M33

The first successful VLBI observations of 10 extragalactic H2O masers in the M33 galaxy are reported. A spectral-line VLBI synthesis map is constructed, the first of any extragalactic H2O maser sources. The map has the lowest noise of any K-band spectral line VLBI map yet produced. The maser emission extends over about 300 milliarcseconds and is divided into 14 distinct spatial components, the strongest of which has a correlated flux density of about 0.7 Jy. The relative positions of some of these components are determined accurately enough to provide first-epoch measurements for proper motion studies. The characteristics of the maser are similar to those of the most powerful maser in the Galaxy, W49N. A compact H II region is found close to the maser which is 1 pc in diameter and whose emission measure is about 6 x 10 to the 7th pc/cm exp 6. This region is the compact component of a more extended H II complex that extends over about 100 pc.

Greenhill, L. J.↗
NASA NTRS1991

The comet rendezvous asteroid flyby mission: A status report

The Comet Rendezvous Asteroid Flyby (CRAF) mission received a new start in fiscal year 1990. CRAF will match orbits with an active short-period comet and follow it around the Sun, making scientific measurements of the nucleus, coma, and tail. The Imaging system will map the nucleus surface at a resolution of 1 meter/line-pair or better, while Visible and Infrared Mapping Spectrometer (VIMS) and Thermal Infrared Radiometer Experiment (TIREX) will produce spectral and thermal maps of the surface. Onboard instruments will collect cometary dust, ice, and gases and perform elemental and molecular analysis. A suite of fields and particles instruments will observe the solar wind interaction with the cometary atmosphere and tail. Radio tracking of the spacecraft will provide an accurate measure of the nucleus mass and higher harmonics in the comet's gravity field. En route to the comet, the spacecraft will make a close flyby of a large asteroid, preferably a primitive type from the outer main belt. Observations at the asteroid include remote sensing mapping of the surface, detection of any solar wind interaction observable at the flyby distance, and measurement of the asteroid mass to better than 10 percent accuracy. Detailed design of the CRAF spacecraft is currently underway at the Jet Propulsion Laboratory (JPL). Recent mass growth has necessitated a switch to Venus-Earth gravity assist type trajectories, similar to that used by the Galileo spacecraft. These trajectories require longer flight times from launch to rendezvous with the target comet. The details of the current baseline mission, spacecraft design, and instrument payload will be reviewed.

Weissman, Paul R.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-27483-DND

scene to retrieve their microphysical properties. The Clouds and the Earth's Radiant Energy System (CERES) Project uses the infrared channels (6.72 Âμm, 7.33 Âμm, 13.3 Âμm,13.6 Âμm, 13.9 Âμm, and 14.2 Âμm) available on the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) to build its algorithms to retrieval cloud properties. Unfortunately, The Visible Infrared Imaging Radiometer Suite (VIIRS) on board Suomi-NPP (National Polar-Orbiting Partnership) lacks these particular measurements. While conducting research using VIIRS data, it is desirable to bring these data into the VIIRS resolution. The Cross-track Infrared Sounder (CrIS), which is also on board Suomi-NPP, has these infrared channels. This paper describes a method to map the CrIS spectral radiances of CO2 and water vapor to VIIRS, with the mapping software in ATOVS and AVHRR Pre-processing (AAPP) package provided by Satellite Application Facilities for Numerical Weather Prediction (NWP SAF). This method is validated comparing mapped10.763 Âμm from CrIS with M15 from VIIRS. The mapped CO2 and water vapor channels were then created and combined with the conventional VIIRS product, as well as compared against corresponding channels of Aqua MODIS instrument.

Yan Chen↗
NASA NTRS2001

Modeling and Prediction of Wildfire Hazard in Southern California, Integration of Models with Imaging Spectrometry

Large urban wildfires throughout southern California have caused billions of dollars of damage and significant loss of life over the last few decades. Rapid urban growth along the wildland interface, high fuel loads and a potential increase in the frequency of large fires due to climatic change suggest that the problem will worsen in the future. Improved fire spread prediction and reduced uncertainty in assessing fire hazard would be significant, both economically and socially. Current problems in the modeling of fire spread include the role of plant community differences, spatial heterogeneity in fuels and spatio-temporal changes in fuels. In this research, we evaluated the potential of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Airborne Synthetic Aperture Radar (AIRSAR) data for providing improved maps of wildfire fuel properties. Analysis concentrated in two areas of Southern California, the Santa Monica Mountains and Santa Barbara Front Range. Wildfire fuel information can be divided into four basic categories: fuel type, fuel load (live green and woody biomass), fuel moisture and fuel condition (live vs senesced fuels). To map fuel type, AVIRIS data were used to map vegetation species using Multiple Endmember Spectral Mixture Analysis (MESMA) and Binary Decision Trees. Green live biomass and canopy moisture were mapped using AVIRIS through analysis of the 980 nm liquid water absorption feature and compared to alternate measures of moisture and field measurements. Woody biomass was mapped using L and P band cross polarimetric data acquired in 1998 and 1999. Fuel condition was mapped using spectral mixture analysis to map green vegetation (green leaves), nonphotosynthetic vegetation (NPV; stems, wood and litter), shade and soil. Summaries describing the potential of hyperspectral and SAR data for fuel mapping are provided by Roberts et al. and Dennison et al. To utilize remotely sensed data to assess fire hazard, fuel-type maps were translated into standard fuel models accessible to the FARSITE fire spread simulator. The FARSITE model and BEHAVE are considered industry standards for fire behavior analysis. Anderson level fuels map, generated using a binary decision tree classifier are available for multiple dates in the Santa Monica Mountains and at least one date for Santa Barbara. Fuel maps that will fill in the areas between Santa Barbara and the Santa Monica Mountains study sites are in progress, as part of a NASA Regional Earth Science Application Center, the Southern California Wildfire Hazard Center. Species-level maps, were supplied to fire managing agencies (Los Angeles County Fire, California Department of Forestry). Research results were published extensively in the refereed and non-refereed literature. Educational outreach included funding of several graduate students, undergraduate intern training and an article featured in the California Alliance for Minorities Program (CAMP) Quarterly Journal.

Roberts, Dar A.↗
NASA NTRS1976

Comparison of cross-spectral and signal enhancement methods for mapping steady-state acoustic fields in turbomachinery ducts

The conceptual differences between the following two approaches used to measure spatial variations in steady-state acoustic pressure amplitude were examined: taking the cross spectrum between two signals from probes in the same field or taking the difference in complex Fourier transform of enhanced probe signals. Each approach is used to analyze pressure data from the inlets of two different turbomachines. A complete mapping of this steady-state field may then be used to determine its modal content. A problem with long term nonstationarity was found with both methods. Conditions for equivalence of the two methods are discussed.

Posey, J. W.↗
NASA NTRS1979

Machine processing of Landsat MSS data and DMA topographic data for forest cover type mapping

A study with the objective of developing and testing techniques which utilize both digital topographic data and Landsat MSS spectral data to map forest cover types is examined. Emphasis is given to the topographic distribution model (TDM), which combines point-by-point information about forest species, elevation, slope, and aspect to quantitatively describe topographic positions. Results show the stratified random sample approach to be very effective for developing the TDM, while the use of topographic data significantly improved the overall classification accuracy of forest cover types as compared to using spectral data alone.

Fleming, M. D.↗
NASA NTRS1989

Comparison of Landsat Thematic Mapper and Geophysical and Environmental Research Imaging Spectrometer data for the Cuprite mining district, Esmeralda, and Nye counties, Nevada

Landsat TM images and Geophysical and Environmental Research Imaging Spectrometer (GERIS) data were analyzed for the Cuprite mining district and compared to available geologic and alteration maps of the area. The TM data, with 30 m resolution and 6 broadbands, allowed discrimination of general mineral groups. Clay minerals, playa deposits, and unaltered rocks were mapped as discrete spectral units using the TM data, but specific minerals were not determined, and definition of the individual alteration zones was not possible. The GERIS, with 15 m spatial resolution and 63 spectral bands, permitted construction of complete spectra and identification of specific minerals. Detailed spectra extracted from the images provided the ability to identify the minerals alunite, kaolinite, hematite, and buddingtonite by their spectral characteristics. The GERIS data show a roughly concentrically zoned hydrothermal system. The mineralogy mapped with the aircraft system conforms to previous field and multispectral image mapping. However, identification of individual minerals and spatial display of the dominant mineralogy add information that can be used to help determine the morphology and genetic origin of the hydrothermal system.

Kierein-Young, Kathryn S.↗
NASA NTRS1980

Optics for future solar system exploration

The optics technology necessary for future solar system exploration is discussed. To satisfy the various mission objectives, optical components need to be of low weight, provide adequate spatial resolution and mapping coverage, provide necessary spectral resolution, provide means to perform adaptable mapping spectrometry, operate under low light levels, provide color images of high fidelity and operate under high temperatures. Future near-infrared mapping spectrometers are examined, and the use of focal-plane detectors to improve their sensitivity is discussed.

Norris, D. D.↗
NASA NTRS1978

Mare basalt types on the front side of the moon - A summary of spectral reflectance data

A unit map of nearside basalt types has been prepared from all telescopic spectral reflectance data currently available for lunar soils. Four parameters were chosen (UV/VIS ratio, albedo, 1 micron band strength, 2 micron band strength) to distinguish and map each of 13 mare basalt types and three additional volcanic groups. Multispectral imagery and albedo maps were used to define unit boundaries while spectra were used to examine the 1 and 2 micron bands and calibrate and quantify the multispectral images. Although the volume of each basalt type is not known, it is clear from the unit map that only 1/3 to 1/2 of the surface basalt types are likely to be represented in the returned lunar samples. For mature lunar soils a single parameter alone does not provide chemical information, but when the four are used together, TiO2 and in some cases FeO can be estimated. Further study of the mineralogy of unsampled lunar basalts requires precise spectra to 2.5 microns with higher spectra and spatial resolution.

Pieters, C. M.↗
NASA NTRS1972

Utilization of ERTS-1 data in North Carolina

The author has identified the following significant results. Initial study and interpretation of ERTS-1 imagery indicates its usefulness for regional land use planning purposes in North Carolina. Quarries, many secondary roads, and the existence of urbanization as well as changes in urban areas may be mapped. Differences in spectral response for various parts of the major cities suggests that the type of activity in urbanized areas may be monitored. Geological mapping at a scale of 1:250,000 may be possible. The major unfavorable comment from various organizations and agencies who are potential users has been to the relatively small scale. The imagery is a powerful illustrative tool for the several state agencies cooperating in the investigation.

Welby, C. W.↗
NASA NTRS1999

The Distribution of Titanium in Lunar Soils on the Basis of Sensor and In Situ Data Fusion

A variety of remote-sensing measurements have been used to map the distribution of elements on the Moon as a means of providing constraints on the processes from which its crust and major terranes originated. Discussed here is Ti, which is incorporated into refractory minerals such as ilmenite during the latter stages of differentiation, and is thus a most useful element for understanding mare basalt petrogenesis. One of the earliest Ti maps showed Ti variations in nearside maria on the basis of groundbased spectral reflectance measurements. A map of Ti derived from gamma-ray measurements on Apollo 15 and 16 was produced at about the same time, and was improved upon considerably by Davis and coworkers, who effectively removed sources of spurious variation from Fe and Al or REE (e.g., Th) interference, and calibrated Ti on the bases of landing-site soil averages. In recent years, spectral reflectance measurements from Clementine have been used by Lucey and coworkers to produce global Ti distribution maps as well. As we indicated previously, the Lucey and Davis maps agree to first order. Meanwhile, we are using the concept of sensor data fusion to combine measurements from the AGR (Apollo gamma-ray) and CSR (Clementine Spectral Reflectance) techniques with ground truth from lunar soils to utilize the differences between the two maps to understand the distribution of Ti within lunar soil components, as we have done with Fe. This technique should be verified and applied on Lunar Prospector gamma-ray measurements of Ti, as the calibrated data become available within the next couple of years. Lunar Ti is found principally in the mineral ilmenite, and is associated with certain components of lunar soil: crystalline Ilmenite mineral fragments and high Ti-bearing glass. All data indicate that Ti is associated with maria and mafic minerals. In AGR and CSR datasets, Ti is highest on the nearside and in the maria, particularly in southern Serenitatis/northern Tranquillitatis and northwestern Procellarum. Unlike CSR-derived values, AGR Ti values show modest increase (up to 0.7%) on the northern farside. Both techniques show a primarily unimodal distribution with a shoulder in the high Ti direction and a primary mode at approximately 0.2% (0.15% for CSR and 0.25% for AGR data), but the AGR Ti data have more structure in the shoulder, including an apparent minor mode at 1.2% Ti, representing non-highland areas. Recalibrating the two datasets on the basis of matching the peaks and range on the histograms would not account for this additional structure in the AGR data. Low Ti areas, which occur predominantly on the farside, are not represented well in the lunar sample collection, although several meteorites thought to be of lunar highland origin show Ti abundances averaging about 0.2%. (Error bars on AGR Ti values are about 0.5%.) Gamma-ray measurements reflect intrinsic Ti surface composition, regardless of the physical or chemical state of Ti. Lucey and coworkers have attempted to produce an equivalent bulk Ti map by normalizing the spectral feature at 415 nm to remove the effects of physical variations from soil to soil. The normalization is based on laboratory measurements of available samples, primarily nearside maria, and is undoubtedly optimized for the proportions in which Ti- components are found in these soils. In particular, mare soils tend to have a much higher proportion of opaque mineral grains, which appears to be well correlated with Ti abundance. The relationship between Ti abundance and proportion of Ti-bearing glass (weighted for Ti abundance) is not as direct. Also shows the relationship between landing site soil average, AGR, and CSR Ti abundances (with CSR filtered to match resolution and field of view of AGR data). AGR Ti values show the best agreement with Ti soil averages, CSR Ti values being somewhat higher in high-Ti soils, and lower in low-Ti soils. These results would tend to support the argument that the technique for deriving Ti from the CSR measurements is optimized for one of the primary Ti-bearing components, most likely opaque mineral grains, and is thus over-compensating and reporting higher Ti values in mare areas, and underreporting Ti in highland areas with much lower proportions of opaque mineral grains. More information is contained in original.

Clark, P. E.↗
NASA NTRS2007

Identification of Stratospheric Waves in Ozone in the Tropics from OMI High Spectral Resolution Measurements

Previous studies using Total Ozone Mapping Spectrometer (TOMS) measurements have identified several types of tropical waves in the stratosphere. These waves include Kelvin waves, mixed Rossby-gravity waves, equatorial Rossby waves, and global normal modes. All of these detected waves occur when their zonal phase speeds are opposite the zonal winds in the low-mid stratosphere associated with the Quasi-biennial Oscillation (QBO). Peak-to-peak amplitudes in all cases are typically 5 DU. While total ozone data from TOMS is sensitive in detecting these tropical waves, they provide each day only a single horizontal cross-sectional map. The high spatial and spectral resolution of the Aura Ozone Monitoring Instrument (OMI) provides a unique means to evaluate 3D structure in these waves including their propagation characteristics. Ozone profiles retrieved from OMI radiances for wavelengths 270-310 nm are utilized to examine the nature of these wave disturbances extending from the lower to upper stratosphere.

Ziemke, J. R.↗
NASA NTRS1991

Quantitative investigations of geologic surfaces utilizing airborne visible/infrared imaging spectrometer (AVIRIS) and polarimetric radar (AIRSAR) data for Death Valley, California

Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and polarimetric radar (AIRSAR) data were collected over Death Valley, California, USA, in September 1989. These two data sets were used to quantitatively characterize both the mineralogy and surface structure of the valley floor. Field mapping and characterization of the salt flats across the valley identified 16 separate units. The AVIRIS data were calibrated using the 'empirical line' method, and spectra extracted for the 16 units. A water vapor map was generated from the AVIRIS data and showed spatial variations in its distribution due to evaporation of surface water. Unmixing of the 16 spectral units produced maps of endmember abundance.

Kierein-Young, Kathryn S.↗
NASA NTRS1974

Ratio techniques for geochemical remote sensing

The present work discusses spectral ratio methods for extracting information on the composition of minerals and rocks from 0.4-14-micron multispectral scanner data. Ratio images and automatic recognition maps based on spectral ratios have the advantages of covering nearly all wavelength regions of important geochemical information, being relatively insensitive to atmospheric and solar illumination variations, and having definable limits of accuracy concerning the capability of discriminating between important geochemical targets and background materials.

Vincent, R. K.↗
NASA NTRS1993

Mapping and monitoring changes in vegetation communities of Jasper Ridge, CA, using spectral fractions derived from AVIRIS images

An important application of remote sensing is to map and monitor changes over large areas of the land surface. This is particularly significant with the current interest in monitoring vegetation communities. Most of traditional methods for mapping different types of plant communities are based upon statistical classification techniques (i.e., parallel piped, nearest-neighbor, etc.) applied to uncalibrated multispectral data. Classes from these techniques are typically difficult to interpret (particularly to a field ecologist/botanist). Also, classes derived for one image can be very different from those derived from another image of the same area, making interpretation of observed temporal changes nearly impossible. More recently, neural networks have been applied to classification. Neural network classification, based upon spectral matching, is weak in dealing with spectral mixtures (a condition prevalent in images of natural surfaces). Another approach to mapping vegetation communities is based on spectral mixture analysis, which can provide a consistent framework for image interpretation. Roberts et al. (1990) mapped vegetation using the band residuals from a simple mixing model (the same spectral endmembers applied to all image pixels). Sabol et al. (1992b) and Roberts et al. (1992) used different methods to apply the most appropriate spectral endmembers to each image pixel, thereby allowing mapping of vegetation based upon the the different endmember spectra. In this paper, we describe a new approach to classification of vegetation communities based upon the spectra fractions derived from spectral mixture analysis. This approach was applied to three 1992 AVIRIS images of Jasper Ridge, California to observe seasonal changes in surface composition.

Sabol, Donald E., Jr.↗