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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Landsat image data quality studies

Preliminary results of the Landsat-4 Image Data Quality Analysis (LIDQA) program to characterize the data obtained using the Thematic Mapper (TM) instrument on board the Landsat-4 and Landsat-5 satellites are reported. TM design specifications were compared to the obtained data with respect to four criteria, including spatial resolution; geometric fidelity; information content; and image relativity to Multispectral Scanner (MSS) data. The overall performance of the TM was rated excellent despite minor instabilities and radiometric anomalies in the data. Spatial performance of the TM exceeded design specifications in terms of both image sharpness and geometric accuracy, and the image utility of the TM data was at least twice as high as MSS data. The separability of alfalfa and sugar beet fields in a TM image is demonstrated.

Schueler, C. F.↗
NASA NTRS1985

The Landsat thematic mapper World Data Base

A World Data Base of potential thematic mapper (TM) scenes was developed to aid in acquisition planning. The World Data Base contains geopolitical, geographic and economic regions along with a format that enables users to find the satellite day, sun angle and cloud cover probability for any month of the year. Scenes that have been acquired by TM and have an average cloud cover of 30 percent of less from July 1982 when TM was launched until the Landsat system was taken over by NOAA in September 1984 are also in the World Data Base. Processed data are referenced in maps and data bases at EROS Data Center; however, a large number of acquistions have never been processed and therefore are not accessible. The World Data Base enables the rapid location of scenes and areas with the least effort making it invaluable in TM scheduling. Users of TM data can use the World Data Base to determine if scenes of interest have been acquired, the acquisition date, and if scenes have been processed to computer-compatible tape (CCT). These uses of the World Data Base make it a valuable tool in the acquisition and location of TM scenes.

Ludwig, R. W.↗
NASA NTRS1987

Interpreting forest and grassland biome productivity utilizing nested scales of image resolution and biogeographical analysis

This report summarizes progress made in our investigation of forest productivity assessment using TM and other biogeographical data during the third six-month period of the grant. Data acquisition and methodology hurdles are largely complete. Four study areas for which the appropriate TM and ancillary data were available are currently being intensively analyzed. Significant relationships have been found on a site by site basis to suggest that forest productivity can be qualitatively assessed using TM band values and site characteristics. Perhaps the most promising results relate TM unsupervised classes to forest productivity, with enhancement from elevation data. During the final phases of the research, multi-temporal and regional comparisons of results will be addressed, as well as the predictability of forest productivity patterns over a large region using TM data and/or TM nested within AVHRR data.

Iverson, Louis R.↗
NASA NTRS1989

Differentiating volcanic rock assemblages using Landsat Thematic Mapper data - Influence of petrochemistry and desert varnish

An investigation has been conducted of the composition, distribution, spectral properties, and Landsat TM influences of desert varnish from three sites in southern Nevada. It is established that the TM signatures of diverse volcanic rock assemblages primarily depend on primary petrochemical characteristics. Desert varnish is found to exert a minimal influence on TM imagery at longer wavelengths, but absorbs the higher frequency radiation of TM bands 1-3, thereby leading to high TM band 5/2 values and dark contrast on 5/2 images over units with high rock-varnish albedo difference; highly evolved volcanic deposits show steep positive spectral slopes in the TM band 5-7 region.

Spatz, D. M.↗
NASA NTRS2009

2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of ~50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam size is suitable for high efficiency. For Q-switched operation, the optimal energy extraction relies on the pump intensity, pump volume, and pump duration which is inversely proportion to the repetition rate. CW and Q-switched Ho:YLF lasers with different linear cavity configurations have been designed and demonstrated for a 30 W Tm:fiber pump laser. The CW Ho laser slope efficiency and optical-to-optical efficiencies reach 65% and 55%, respectively. The pulsed laser efficiency depends on the repetition rate. For 1 kHz operation, the optical-to-optical efficiency is 39% when the pump power is 14.5W. Currently, the injection seeding success rate is between 99.4% and 99.95%. After a ten thousand pulses, the standard deviation of the laser frequency jitter is about 3 MHz. It meets the requirements of highly precise CO2 concentration measurement. In conclusion, an injection seeded, high repetition rate, Q-switched Ho:YLF laser has been developed for a coherent CO2 differential absorption lidar. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. It can potentially meet the requirements of the coherent detection of CO2 concentration by a differential absorption lidar technique.

Singh, Upendra N.↗
NASA NTRS2020

NASA Meteoroid Engineering Model (MEM) Version 3

The Meteoroid Engineering Model (MEM) version 3 is NASA’s most current and accurate model of the meteoroid environment. MEM 3 supersedes all previous versions of MEM, including MEM Release 2.0 (MEMR2), MEM Release 1.0c (MEMR1c), and previously internally controlled and released versions of MEMCxP v2.0 and LunarMEM v2.0. Earlier versions of MEM superseded older models of the meteoroid environment such as the Grün model and its derivative, Technical Memo 4527 (hereafter abbreviated as TM 4527) [1]. Prior to the establishment of the NASA Meteoroid Environment Office (MEO), NASA’s meteoroid environment models relied on a simple empirical expression derived from [2], as described in [3] and later in [1]. This expression describes the meteoroid flux incident on a flat plate near 1 au. TM 4527 assumes an isotropic environment, making the orientation of the plate irrelevant [4]. The flux was combined with scale factors to account for the reduction in flux occurring when the Earth shields the spacecraft from a portion of the meteoroid environment and the enhancement in flux due to the focusing effect of Earth’s gravitational field. TM 4527 also introduced a crude, piecewise meteoroid speed distribution with an average velocity of 19 km/s for an orbiting spacecraft based on [5]. Finally, TM 4527 assumed a three-step density distribution in which dust particles smaller than 10−6 g have a density of 2 g/cu cm, micrometeoroids between 10−6 g and 0.01 g have a density of 1 g/cu cm, and meteoroids larger than 0.01 g have a density of 0.5 g/cm3. Thus, the meteoroid model presented in TM 4527 was assembled from multiple independent sources. The model of TM 4527 was also used for years in Space Station risk assessments, and is described in Space Station Specification (SSP) 30425.

Moorhead, A. V.↗
DOE OSTI2024

Effects of irradiation damage on the elastic properties and hardness of complex transition metal diborides

Multi-principal component transition metal (TM) diborides represent a class of high-entropy ceramics (HECs) that have received considerable interest in recent years owing to their promising properties for extreme environment applications that include thermal/ environmental barriers, hypersonic vehicles, turbine engines, and next-generation nuclear reactors. While the addition of chemical disorder through the random distribution of TM elements on the cation sublattice has offered opportunities to tailor elastic stiffness and hardness, the effects of irradiationinduced structural damage on the physical properties of these complex materials have remained largely unexplored. To this end, changes in the hardness and elastic moduli of a high-entropy TM diboride (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)B2 and three of its quaternary subsets following irradiation with 10 MeV gold (Au) ions to fluences of up to 6 × 10^15 Au cm-2 are investigated at the micrometer and sub-micrometer length-scales via the dispersion of laser-generated surface acoustic waves (SAW) and nanoindentation, respectively. The nanoindentation measurements show that the TM diborides exhibit an initial increase in hardness following irradiation with energetic Au ions, with a subsequent decrease in hardness following further irradiation. One quaternary composition, (Hf1/3Ta1/3Ti1/3)B2, exhibits a notable exception to the trend and continues to exhibit an increase in hardness with ion irradiation fluence. Although differences in the absolute values of the effective elastic moduli obtained from the measured SAW dispersion and nanoindentation are observed (and attributed to microstructural variations at the measurement length-scale), both techniques yield similar trends in the form of an initial reduction and subsequent saturation in the elastic modulus with increasing ion irradiation fluence. The quaternary TM diboride (Hf1/3Ta1/3Ti1/3)B2 again exhibits a departure from this trend. The high-entropy TM diboride (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)B2 exhibits the greatest recovery in hardness and modulus when irradiated to high ion fluences following initial changes at low fluence, indicating superior resistance to radiation-induced damage over its quaternary counterparts. Opportunities for designing HECs with superior hardness and modulus for enhanced radiation resistance (compared to their single constituent counterparts) by tailoring chemical disorder and bond character in the lattice are discussed.

36 - MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmGa2Pd by Materials Project

TmPdGa2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tm is bonded in a 1-coordinate geometry to five equivalent Pd and ten equivalent Ga atoms. There are a spread of Tm–Pd bond distances ranging from 2.90–3.51 Å. There are a spread of Tm–Ga bond distances ranging from 3.00–3.35 Å. Pd is bonded in a 9-coordinate geometry to five equivalent Tm and six equivalent Ga atoms. There are two shorter (2.64 Å) and four longer (2.66 Å) Pd–Ga bond lengths. Ga is bonded in a 10-coordinate geometry to five equivalent Tm, three equivalent Pd, and two equivalent Ga atoms. There are one shorter (2.62 Å) and one longer (2.67 Å) Ga–Ga bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmAl2Ni by Materials Project

TmNiAl2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Tm is bonded in a 1-coordinate geometry to three equivalent Ni and ten equivalent Al atoms. There are one shorter (2.78 Å) and two longer (3.00 Å) Tm–Ni bond lengths. There are a spread of Tm–Al bond distances ranging from 3.04–3.25 Å. Ni is bonded in a 9-coordinate geometry to three equivalent Tm and six equivalent Al atoms. There are two shorter (2.46 Å) and four longer (2.51 Å) Ni–Al bond lengths. Al is bonded in a 3-coordinate geometry to five equivalent Tm and three equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmAl7Au3 by Materials Project

TmAu3Al7 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Tm is bonded in a 6-coordinate geometry to six equivalent Au and twelve equivalent Al atoms. All Tm–Au bond lengths are 3.25 Å. There are six shorter (3.32 Å) and six longer (3.36 Å) Tm–Al bond lengths. Au is bonded in a 9-coordinate geometry to two equivalent Tm and seven Al atoms. There are a spread of Au–Al bond distances ranging from 2.59–2.67 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a distorted trigonal planar geometry to two equivalent Tm and three equivalent Au atoms. In the second Al site, Al is bonded in a trigonal planar geometry to three equivalent Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmSnAu by Materials Project

TmAuSn crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Tm is bonded in a 3-coordinate geometry to six equivalent Au and six equivalent Sn atoms. There are three shorter (2.97 Å) and three longer (3.67 Å) Tm–Au bond lengths. There are three shorter (3.19 Å) and three longer (3.37 Å) Tm–Sn bond lengths. Au is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Sn atoms. There are three shorter (2.82 Å) and one longer (2.92 Å) Au–Sn bond lengths. Sn is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm3InN by Materials Project

Tm3InN is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Tm is bonded in a linear geometry to four equivalent In and two equivalent N atoms. All Tm–In bond lengths are 3.35 Å. Both Tm–N bond lengths are 2.37 Å. In is bonded to twelve equivalent Tm atoms to form InTm12 cuboctahedra that share corners with twelve equivalent InTm12 cuboctahedra, faces with six equivalent InTm12 cuboctahedra, and faces with eight equivalent NTm6 octahedra. N is bonded to six equivalent Tm atoms to form NTm6 octahedra that share corners with six equivalent NTm6 octahedra and faces with eight equivalent InTm12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmSiRu by Materials Project

TmRuSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Tm is bonded in a 9-coordinate geometry to four equivalent Ru and five equivalent Si atoms. There are one shorter (2.92 Å) and three longer (2.94 Å) Tm–Ru bond lengths. There are two shorter (2.96 Å) and three longer (3.00 Å) Tm–Si bond lengths. Ru is bonded in a 8-coordinate geometry to four equivalent Tm and four equivalent Si atoms. There are a spread of Ru–Si bond distances ranging from 2.46–2.55 Å. Si is bonded in a 10-coordinate geometry to five equivalent Tm and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmCuPb by Materials Project

TmCuPb crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Tm is bonded in a 12-coordinate geometry to six equivalent Cu and six equivalent Pb atoms. There are three shorter (2.95 Å) and three longer (3.57 Å) Tm–Cu bond lengths. There are three shorter (3.14 Å) and three longer (3.32 Å) Tm–Pb bond lengths. Cu is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Pb atoms. There are three shorter (2.75 Å) and one longer (2.95 Å) Cu–Pb bond lengths. Pb is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmGeRu by Materials Project

TmRuGe crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Tm is bonded in a 9-coordinate geometry to four equivalent Ru and six equivalent Ge atoms. There are a spread of Tm–Ru bond distances ranging from 2.92–3.00 Å. There are a spread of Tm–Ge bond distances ranging from 3.01–3.30 Å. Ru is bonded in a 8-coordinate geometry to four equivalent Tm and four equivalent Ge atoms. There are a spread of Ru–Ge bond distances ranging from 2.53–2.58 Å. Ge is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Ru atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmInNi4 by Materials Project

TmNi4In crystallizes in the cubic F-43m space group. The structure is three-dimensional. Tm is bonded in a 12-coordinate geometry to twelve equivalent Ni and four equivalent In atoms. All Tm–Ni bond lengths are 2.90 Å. All Tm–In bond lengths are 3.03 Å. Ni is bonded to three equivalent Tm, six equivalent Ni, and three equivalent In atoms to form a mixture of corner, edge, and face-sharing NiTm3In3Ni6 cuboctahedra. There are three shorter (2.46 Å) and three longer (2.49 Å) Ni–Ni bond lengths. All Ni–In bond lengths are 2.90 Å. In is bonded in a 4-coordinate geometry to four equivalent Tm and twelve equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TmNiGe by Materials Project

TmNiGe crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Tm is bonded in a 12-coordinate geometry to six equivalent Ni and six equivalent Ge atoms. There are a spread of Tm–Ni bond distances ranging from 2.89–3.12 Å. There are a spread of Tm–Ge bond distances ranging from 2.92–3.06 Å. Ni is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Ge atoms. There are a spread of Ni–Ge bond distances ranging from 2.44–2.67 Å. Ge is bonded in a 10-coordinate geometry to six equivalent Tm and four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm2InPd2 by Materials Project

Tm2Pd2In crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Tm is bonded in a 6-coordinate geometry to six equivalent Pd and four equivalent In atoms. There are two shorter (2.84 Å) and four longer (2.97 Å) Tm–Pd bond lengths. All Tm–In bond lengths are 3.38 Å. Pd is bonded in a 9-coordinate geometry to six equivalent Tm, one Pd, and two equivalent In atoms. The Pd–Pd bond length is 2.79 Å. Both Pd–In bond lengths are 3.02 Å. In is bonded to eight equivalent Tm and four equivalent Pd atoms to form a mixture of corner and face-sharing InTm8Pd4 cuboctahedra.

36 MATERIALS SCIENCE↗