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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 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Influences of North Pacific Ocean Domain Extent on the Western U.S. Winter Hydroclimatology in Variable-Resolution CESM

Variable-resolution global climate models (VRGCMs) are a dynamical downscaling method that can reach spatiotemporal scales needed for regional climate assessments. Over the years, several users of VRGCMs have assumed where the location and extent of the refinement domain should be based on knowledge of the prevailing storm tracks and resolution dependence of important regional climate processes (e.g., atmospheric rivers [ARs] and orographic uplift), but the effect of high-resolution domain size and extent on the simulation of downstream hydroclimatic phenomena has not been systematically evaluated. Here, we use variable resolution in the Community Earth System Model (VR-CESM) to perform such a test. To do this, three VR-CESM grids were generated that span the entire, two thirds, and one third of the North Pacific and evaluated for a 30-year climatology using Atmospheric Model Intercomparison Project protocols. Simulations are compared with reanalysis products offshore (fifth-generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis [ERA5]) and onshore (Livneh, 2015, https://doi.org/10.1038/sdata.2015.42, and Parameter-elevation Regressions on Independent Slopes Model [PRISM]) of the western United States. The westward expansion of refinement domain influenced integrated vapor transport (IVT), which was generally high biased but minimally impacted AR characteristics. Due to slight differences in landfalling AR counts in the western United States, California winter precipitation generally improved with westward expansion of the refinement domain. Western U.S. mountain snowpack and surface temperatures were insensitive to refinement domain size and were more influenced by changes in topographic resolution and/or land surface model version. Here, given minimal dependence of simulated western U.S. hydroclimate on refinement domain size over the North Pacific, we advise future VR-CESM studies to focus grid resolution on better resolving land surface heterogeneity.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Hydrologic Connectivity and Patch‐To‐Hillslope Scale Relations in Dryland Ecosystems

Abstract In drylands, runoff during storms redistributes water and nutrients from bare soil areas to vegetated patches, subsidizing vegetation with additional resources. The extent of this redistribution depends on the interplay between surface roughness and permeability; greater permeability in vegetated patches promotes run‐on to vegetation, but greater surface roughness diverts runoff, producing tortuous flow paths that bypass vegetation. Here, this interplay is examined in virtual experiments using the 2D Saint Venant Equations to measure runoff connectivity. Flowpaths are delineated using tracers advected by the flow. Distances between tracer sources and sinks along flowpaths measure hydrologic connectivity at two lengthscales: connectivity to the hillslope outlet and within‐slope source‐sink connectivity. Differences between these connectivity lengthscales indicate how flow may “by‐pass” vegetated patches within hillslopes. At the hillslope scale, a derived power‐law relation between the runoff coefficient and outlet connectivity describes hillslope water losses, providing a foundation for identifying landscapes likely to shed water.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

Arctic and subarctic environmental analyses utilizing ERTS-1 imagery

The author has identified the following significant results. Physiognomic landscape features were used as geologic and vegetative indicators in preparation of a surficial geology, vegetation, and permafrost map at a scale of 1:1 million using ERTS-1 band 7 imagery. The detail from this map compared favorably with USGS maps at 1:250,000 scale. Physical boundaries mapped from ERTS-1 imagery in combination with ground truth obtained from existing small maps and other sources resulted in improved and more detailed maps of permafrost terrain and vegetation for the same area. ERTS-1 imagery provides for the first time, a means of monitoring the following regional estuarine processes: daily and periodic surface water circulation patterns; changes in the relative sediment load of rivers discharging into the inlet; and, several local patterns not recognized before, such as a clockwise back eddy offshore from Clam Gulch and a counterclockwise current north of the Forelands. Comparison of ERTS-1 and Mariner imagery has revealed that the thermokarst depressions found on the Alaskan North Slope and polygonal patterns on the Yukon River Delta are possible analogs to some Martian terrain features.

Anderson, D. M.↗
NASA NTRS1981

Computation of averaged monthly zonal albedo utilizing the solar zenith angle, properties of clear and cloudy atmospheres

The zonal temporal averages of albedos at the top of the atmosphere were considered as a function of the length of the day. The length of the day were used to determine the average daily values of mu sub 0(=Cos of the solar zenith angle, theta sub 0). Polynominal fits of the slope and intercept functions of A sub s (cloud-free albedo) and A sub c(cloud albedo) as function of Cos theta sub 0 were obtained by using the sample values of albedo corresponding to solar zenith angles from 0 to 90 deg with interval of 5 deg. The daily zonal values of mu sub 0 and the surface albedos were used to compute the daily zonal values of albedos at the top of the clear and cloudy atmosphere. The monthly zonal cloud fractions were used to compute planetary albedo A at the top of the atmosphere. The global values of monthly albedos A sub s, A sub c and A were computed by using the weighting function defined as the difference of the sins of zonal values of latitudes. The computer program implementation is also described.

Dhuria, H.↗
NASA NTRS1993

Wind-tunnel investigation of aerodynamic efficiency of three planar elliptical wings with curvature of quarter-chord line

Three planar, untwisted wings with the same elliptical chord distribution but with different curvatures of the quarter-chord line were tested in the Langley 8-Foot Transonic Pressure Tunnel (8-ft TPT) and the Langley 7- by 10-Foot High-Speed Tunnel (7 x 10 HST). A fourth wing with a rectangular planform and the same projected area and span was also tested. Force and moment measurements from the 8-ft TPT tests are presented for Mach numbers from 0.3 to 0.5 and angles of attack from -4 degrees to 7 degrees. Sketches of the oil-flow patterns on the upper surfaces of the wings and some force and moment measurements from the 7 x 10 HST tests are presented at a Mach number of 0.5. Increasing the curvature of the quarter-chord line makes the angle of zero lift more negative but has little effect on the drag coefficient at zero lift. The changes in lift-curve slope and in the Oswald efficiency factor with the change in curvature of the quarter-chord line (wingtip location) indicate that the elliptical wing with the unswept quarter-chord line has the lowest lifting efficiency and the elliptical wing with the unswept trailing edge has the highest lifting efficiency; the crescent-shaped planform wing has an efficiency in between.

Mineck, Raymond E.↗
NASA NTRS2007

Desert Research and Technology Studies (RATS) Local and Remote Test Sites

Desert RATS (Research and Technology Studies) is a combined group of inter-NASA center scientists and engineers, collaborating with representatives of industry and academia, for the purpose of conducting remote field exercises. These exercises provide the capability to validate experimental hardware and software, to evaluate and develop mission operational techniques, and to identify and establish technical requirements applicable for future planetary exploration. D-RATS completed its ninth year of field testing in September 2006. Dry run test activities prior to testing at designated remote field site locations are initially conducted at the Johnson Space Center (JSC) Remote Field Demonstration Test Site. This is a multi-acre external test site located at JSC and has detailed representative terrain features simulating both Lunar and Mars surface characteristics. The majority of the remote field tests have been subsequently conducted in various high desert areas adjacent to Flagstaff, Arizona. Both the local JSC and remote field test sites have terrain conditions that are representative of both the Moon and Mars, such as strewn rock and volcanic ash fields, meteorite crater ejecta blankets, rolling plains, hills, gullies, slopes, and outcrops. Flagstaff is the preferred remote test site location for many reasons. First, there are nine potential test sites with representative terrain features within a 75-mile radius. Second, Flagstaff is the location of the United States Geologic Survey (USGS)/Astrogeology Branch, which historically supported Apollo astronaut geologic training and currently supports and provides host accommodations to the D-RATS team. Finally, in considering the importance of logistics in regard to providing the necessary level of support capabilities, the Flagstaff area provides substantial logistics support and lodging accommodations to take care of team members during long hours of field operations.

Janoiko, Barbara↗
NASA NTRS2007

Remote and Ground Truth Spectral Measurement Comparisons

FORMOSAT III are a set of six research satellites from Taiwan that were launched in April 2006. The satellites are in 800 km, 71 degree inclination orbits and separated by 24 degrees in ascending node. Ground truth spectral measurements were taken of outer surface materials on FORMOSAT III. From those measurements, a computer model was built to predict the spectral reflectance, which included phase angle and orientation of the spacecraft relative to the observer. However, materials exposed to the space environment have exhibited spectral changes including a darkening and a reddening of the spectra. This reddening was seen as an increase in slope of the reflectance as the wavelength increases. Therefore, the model of pristine materials was augmented to include the space weathering effects. Remote data were collected on two of the six FORMOSAT satellites using the 1.6 meter telescope at AMOS (Air Force Maui Optical and Supercomputing) site with the Spica spectrometer. Due to the separation in ascending node, observations were made on whichever one of the six satellites was visible on that specific night. Three nights of data were collected using the red (6000 9500 angstroms) filter and two nights of data were collected using the blue (3200 -6600 angstroms) filter. A comparison of the data showed a good match to the pristine model for the blue filter region. The absorption feature near 5500 angstroms due to the copper colored Kapton multi-layer insulation (MLI) was very apparent in the remote samples and a good fit to the data was seen in both satellites observed. The features in the red filter regime agreed with the pristine model up through 7000 angstroms where the reddening begins and the slope of the remote sample increases. A comparison of the two satellites showed similar features in the red and blue filter regions, i.e. the satellites were aging at the same rate. A comparison of the pristine model to the first month of remote measurements showed the amount by which the satellite had reddened. This information was used in the space weathered model to predict the second month s reflectance measurement. The results showed that the reddening did not increase from the first month of observations to the second. A third month of data will be necessary to determine if the reddening occurs instantly and then stabilizes with time or if the effect continues to increase with time.

Abercromby, Kira Jorgensen↗
DOE OSTI2018

Joint UAS-Balloon Activities (JUBA) Field Campaign Report

Using internal investment funds within Sandia National Laboratories’ (SNL) Division 6000, the Joint UAS-Balloon Activity (JUBA) was a collaborative exercise between SNL Organizations 6533 and 6913 (later 8863) to demonstrate simultaneous flights of tethered balloons and unmanned aerial systems (UAS) on the North Slope of Alaska. JUBA UAS and tethered balloon flights were conducted within the Restricted Airspace associated with the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility third ARM Mobile Facility (AMF3) site at Oliktok Point, Alaska. The Restricted Airspace occupies a two-nautical-mile radius around Oliktok Point. JUBA was conducted at the Sandia Arctic Site, which is approximately 2 km east-southeast of the AMF3. JUBA activities occurred from 08/08/17 and 08/10/17. Atmospheric measurements from tethered balloons can occur for a long duration, but offer limited spatial variation. Measurements from UAS could offer increased spatial variability. To understand how balloon and UAS activities could occur together, JUBA activities included the following: Developing aviation safety plans for the simultaneous, collocated operation of tethered balloons and UAS Adapting tethered balloon-based fiber optic distributed temperature sensing (DTS) measurements to a UAS platform Creating solutions to technical challenges such as: Developing a motor system to match the fiber deployment rate with the ascent/descent rate of the UAS Evaluating methods of identifying the surface in the DTS temperature profile Correlating simultaneous balloon and UAS DTS temperature measurements Assessing the effects of a fiber optic rotary joint on the DTS temperature measurements Determining what UAS-based sensors provided the best calibration source for the DTS temperature data.

North Slope of Alaska, arctic processes, unmanned ↗
DOE OSTI2015

Optimizing cosmogenic burial isochrons using muon-inclusive simple burial dating

Isochron burial dating with cosmogenic nuclides presents new opportunities for determining the deposition age of Plio-Pleistocene gravels. The method uses paired measurements of 26 Al and 10 Be from individual clasts and is able to generate ages even if burial histories are complex and poorly constrained. Critical to the isochron method is the assumption that gravel is deposited with a predictable 26 Al/ 10 Be ratio, based on near-surface production rates, that then decreases due to radioactive decay after burial. If all clasts are collected from the same depth in a deposit, they share the same history of post-burial production and decay. Because decay constants are known, a line regressed through a bivariate plot of 26 Al and 10 Be concentrations represents an isochron, the slope of which is related to burial duration. The method is ideal when samples are numerous (≥ 5 data points) and yield a spread of concentrations such that linear regression can resolve a meaningful slope, but logistics, costs, and site geology can preclude such ideal datasets. Additionally, it can be difficult to identify and reject samples that may have been deposited with nuclide ratios resulting from prior burial that have the potential to contaminate isochron age estimates. Here we present a methodology for checking the integrity of small isochron datasets (≤4 samples) by co-applying a muon-inclusive simple burial dating algorithm that scales muogenic production with shielding mass (cover density * depth). This analysis uses the same 26 Al and 10 Be concentrations as the isochron method, but incorporates assumptions based on site geology to independently validate and inform isochron results. We use two examples to demonstrate how these burial calculations can increase confidence in isochron results, show when the isochron method is inappropriately applied, and provide criteria for rejection of data points in isochrons.

58 GEOSCIENCES↗
DOE OSTI2020

Growth and Properties of Vapor Diffused Nb3Sn Coating for Superconducting Radiofrequency Accelerator Cavity Applications

The desire to reduce construction and operating costs of future SRF accelerators motivates the search for higher-performing alternative materials. Nb3Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. The tin vapor diffusion process is currently the technique of choice to produce promising Nb3Sn-coated cavities. Understanding Nb3Sn nucleation and growth in this process is essential to progress. Samples representing different stages of Nb3Sn formation have been produced and studied to elucidate the effects of nucleation, growth, process conditions, and impurities. Nb3Sn films with thickness from a few hundred nm up to ~15 µm were grown and characterized. The microscopic examination of samples suggests the mechanisms of thin film nucleation and growth. Broadly, nucleation deposits tin as a thin surface phase and, under some conditions, a few hundred nanometer sized particles as well. Conditions that impair nucleation promote the formation of defects, such as ?patches?, in subsequent coating growth. Analysis of coated samples is consistent with the model of Nb3Sn grown in which tin diffuses via grain boundaries to Nb3Sn-Nb interface, where the growth Nb3Sn into the niobium bulk takes place. Similar scaling laws are found for grain growth and layer thickness. Non-parabolic layer growth is consistent with significant grain growth, which reduces the number of Sn-transport channels. Examination of patchy region in Nb3Sn coating revealed it to be large single crystalline grains, pointing to impeded Nb3Sn layer growth due to low grain boundary density, resulting in a significantly thin coating in those areas. Examination of RF loss regions from a coated cavity, identified with a thermometry mapping system showed patchy regions and carbonus defects were associated with strong local field-dependent surface resistance. RF measurements of coated cavities were combined with material characterization of witness samples and coated-cavity cutouts to improve the coating process. Understanding obtained and applied to cavity coatings, resulted in single-cell Nb3Sn cavities with a quality factor of ~2 ×1010 up to 15 MV/m accelerating gradient at 4 K, without "Wuppertal" Q-slope. We have also produced Nb3Sn-coated CEBAF 5-cell cavities with accelerating gradients useful for accelerator cryomodules. This dissertation will discuss the genesis of the Nb3Sn coating in a typical tin vapor diffusion process, effects of different process parameters, and its consequences to the coating of single-cell and multi-cell SRF cavities.

Pudasaini, Uttar↗
DOE OSTI2023

Machine learning predictions of near-surface permafrost extent at Teller 27, Teller 47, and the Kougarok 64 Hillslope sites on the Seward Peninsula, Alaska: Supporting Data

Geophysical surveys were conducted at the NGEE Arctic Teller mile marker 27 site, Teller mile marker 47 site, and Kougarok mile marker 64 site during the summers of 2018, 2019, and 2021. Additional data was collected at Teller mile marker 47 during September 2021 and August 2022. These surveys were used to identify locations of near-surface permafrost during the period of maximum seasonal thaw depth for ground truth data used in machine learning predictions of near-surface permafrost extent at each site. This dataset contains CSV files of ground truth observations of near-permafrost presence or absence for each site, where PF = 1 indicates permafrost presence and PF = 0 indicates permafrost absence. The dataset also includes 2 sets of binary rasters (WGS84 UTM zone 3) of permafrost extent for each site using 1) all of the training data and 2) the transferred model. For both sets of rasters, 0 = non-permafrost and 1 = permafrost. Included are 6 *.tif files and 5 *.csv files that include a data dictionary (dd.csv) and file-level metadata (flmd.csv). This dataset is in support of the paper "Machine learning-derived high-resolution maps of near-surface permafrost for three watersheds on the Seward Peninsula, Alaska" that is in review (May 2023). The Next-Generation Experiments: Arctic (NGEE Arctic), a research effort to reduce uncertainty in Earth System Models by developing a predictive understanding of carbon-rich Arctic ecosystems and feedbacks to climate. NGEE Arctic was supported by the Department of Energy's Office of Biological and Environmental Research. The NGEE Arctic project had two field research sites: 1) located within the Arctic polygonal tundra coastal region on the Barrow Environmental Observatory (BEO) and the North Slope near Utqiagvik (Barrow), Alaska and 2) multiple areas on the discontinuous permafrost region of the Seward Peninsula north of Nome, Alaska. Through observations, experiments, and synthesis with existing datasets, NGEE Arctic provided an enhanced knowledge base for multi-scale modeling and contributed to improved process representation at global pan-Arctic scales within the Department of Energy's Earth system Model (the Energy Exascale Earth System Model, or E3SM), and specifically within the E3SM Land Model component (ELM).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Spectroscopic signature of moment-dependent electron–phonon coupling in 2 H -TaS 2

Here, charge density wave (CDW) order is ubiquitous among low-dimensional electronic systems, as realized in layered materials such as various 1 T and 2 H polytypes of transition metal dichalcogenides (TMDs). In particular, 2 H -TaS 2 , a prominent member of the vast family of TMDs, hosts a canonical CDW phase transition whose mechanism remains controversial even after decades of research. Using state-of-the-art angle resolved photoemission spectroscopy (ARPES) measurements, we report, for the first time, pronounced many-body renormalizations in 2 H -TaS 2 . These renormalizations are manifested by the presence of multiple slope changes, known as “kinks”, in the electronic dispersions. The temperature independence of the kink energies and their close correspondence with the phonon frequencies of the system evidence that these renormalizations are caused by electron–phonon interactions. In addition, the electron–phonon coupling parameter is momentum-dependent, and the CDW vector is not compatible with any of the Fermi surface nesting vectors. Collectively, these observations establish that the origin of the CDW transition in 2 H -TaS 2 is not the same as that of the Peierls ordering transition, rather this transition is triggered by strong electron–phonon coupling including its momentum anisotropy. The commonality between the ARPES data on 2 H -TaS 2 and those on 2H-TaSe 2 and 2 H -NbSe 2 rationalize the above interpretation of the CDW transition being generic to incommensurate CDW orders in 2 H polytypes of TMDs.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Optical properties of (162173) 1999 JU3: in preparation for the JAXA Hayabusa 2 sample return mission

We investigated the magnitude-phase relation of (162173) 1999 JU3, a target asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed the International Astronomical Union's H-G formalism but found that it fits less well using a single set of parameters. To improve the inadequate fit, we employed two photometric functions: the Shevchenko and Hapke functions. With the Shevchenko function, we found that the magnitude-phase relation exhibits linear behavior in a wide phase angle range (α = 5°-75°) and shows weak nonlinear opposition brightening at α < 5°, providing a more reliable absolute magnitude of H {sub V} = 19.25 ± 0.03. The phase slope (0.039 ± 0.001 mag deg{sup –1}) and opposition effect amplitude (parameterized by the ratio of intensity at α = 0.°3 to that at α = 5°, I(0.°3)/I(5°) = 1.31 ± 0.05) are consistent with those of typical C-type asteroids. We also attempted to determine the parameters for the Hapke model, which are applicable for constructing the surface reflectance map with the Hayabusa 2 onboard cameras. Although we could not constrain the full set of Hapke parameters, we obtained possible values, w = 0.041, g = –0.38, B {sub 0} = 1.43, and h = 0.050, assuming a surface roughness parameter θ-bar = 20°. By combining our photometric study with a thermal model of the asteroid, we obtained a geometric albedo of p {sub v} = 0.047 ± 0.003, phase integral q = 0.32 ± 0.03, and Bond albedo A {sub B} = 0.014 ± 0.002, which are commensurate with the values for common C-type asteroids.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Landslides caused by the Mw7.8 Kaikōura earthquake and the immediate response

Tens of thousands of landslides were generated over 10,000 km 2 of North Canterbury and Marlborough as a consequence of the 14 November 2016, M w 7.8 Kaikōura Earthquake. The most intense landslide damage was concentrated in 3500 km 2 around the areas of fault rupture. Given the sparsely populated area affected by landslides, only a few homes were impacted and there were no recorded deaths due to landslides. Landslides caused major disruption with all road and rail links with Kaikōura being severed. The landslides affecting State Highway 1 (the main road link in the South Island of New Zealand) and the South Island main trunk railway extended from Ward in Marlborough all the way to the south of Oaro in North Canterbury. The majority of landslides occurred in two geological and geotechnically distinct materials reflective of the dominant rock types in the affected area. In the Neogene sedimentary rocks (sandstones, limestones and siltstones) of the Hurunui District, North Canterbury and around Cape Campbell in Marlborough, first-time and reactivated rock-slides and rock-block slides were the dominant landslide type. These rocks also tend to have rock material strength values in the range of 5-20 MPa. In the Torlesse ‘basement’ rocks (greywacke sandstones and argillite) of the Kaikōura Ranges, first-time rock and debris avalanches were the dominant landslide type. These rocks tend to have material strength values in the range of 20-50 MPa. A feature of this earthquake is the large number (more than 200) of valley blocking landslides it generated. This was partly due to the steep and confined slopes in the area and the widely distributed strong ground shaking. The largest landslide dam has an approximate volume of 12(±2) M m 3 and the debris from this travelled about 2.7 km 2 downslope where it formed a dam blocking the Hapuku River. The long-term stability of cracked slopes and landslide dams from future strong earthquakes and large rainstorms are an ongoing concern to central and local government agencies responsible for rebuilding homes and infrastructure. A particular concern is the potential for debris floods to affect downstream assets and infrastructure should some of the landslide dams breach catastrophically. At least twenty-one faults ruptured to the ground surface or sea floor, with these surface ruptures extending from the Emu Plain in North Canterbury to offshore of Cape Campbell in Marlborough. The mapped landslide distribution reflects the complexity of the earthquake rupture. Landslides are distributed across a broad area of intense ground shaking reflective of the elongate area affected by fault rupture, and are not clustered around the earthquake epicentre. The largest landslides triggered by the earthquake are located either on or adjacent to faults that ruptured to the ground surface. Surface faults may provide a plane of weakness or hydrological discontinuity and adversely oriented surface faults may be indicative of the location of future large landslides. Their location appears to have a strong structural geological control. Initial results from our landslide investigations suggest predictive models relying only on ground-shaking estimates underestimate the number and size of the largest landslides that occurred.

58 GEOSCIENCES↗
NASA NTRS1972

Glancing incidence telescopes for space astronomy

Design optimization is reported for glancing telescopes of increased collecting areas. Considered are nested geometries for X-ray and extreme ultraviolet telescopes, each of which generates only one singular principal surface. In the case of the X-ray telescope, the field curvature of the outer telescope serves as a standard and the focus of each of the inner telescopes is made coplanar by a slight descrease in the collecting area of each of the inner telescopes. In the case of the EUV telescope, a slight change in the maximum slope angle of the inner telescope makes the field curvatures coincide. Five concentric X-ray telescopes form a collecting area of approximately 900 sq cm, and a nested EUV telescope consisting of two concentric telescopes produces a collecting area of about 45 sq cm.

Mangus, J. D.↗
NASA NTRS1972

Lineaments of the Apennine Front - Apollo 15 landing site.

The well-developed systems of lineaments that suggest regional fracturing or layering of the bedrock in the mountains at the Apollo 15 site may be illusions created by oblique lighting rather than expressions of true geologic structure. Supporting evidence includes: (1) occurrence of similar dominant lineament trends on many of the slopes even though the slope orientations differ widely; (2) presence of a thick mantling regolith that should conceal bedrock structures; (3) approximate symmetry of some of the lineament sets about the sun line; (4) lack of clear-cut topographic expression for many of the lineaments; and (5) general similarity of the lunar lineaments to lineament patterns produced by low oblique lighting on model surfaces mantled by fine sifted powder. Locally, as at Silver Spur, some lineament trends are related to distinct topographic features and are more confidently interpreted to reflect underlying geologic structures.

Wolfe, E. W.↗
NASA NTRS1988

Geodynamics laser ranging system: Performance simulations and development of the EOS facility

The NASA Geodynamics Laser Ranging System is a spaceborne multicolor laser ranger to be used for studying regional and local scale crustal movements and will provide a capability for height profiling of ice-sheets, land terrains, cloud-tops, and other surfaces. Ranging measurements to retroreflector targets will produce intersite distances and relative heights with subcentimeter accuracy over baselines up to several hundred kilometers long. Arrays containing up to a few hundred targets can be surveyed nearly simultaneously. Altimetric profiling can be performed with spatial resolution of 80m and vertical accuracy of 10cm with the latter depending on the roughness and slope of the terrain.

Cohen, S. C.↗
NASA NTRS1992

Preliminary analysis of thermal-infrared multispectral scanner data of the Iron Hill, Colorado carbonatite-alkalic rock complex

The Iron Hill carbonatite-alkalic igneous rock complex is in the Powderhorn mining district, approximately 40 km south-southwest of Gunnison, Colorado. The complex, which occupies about 30 sq km, was emplaced in metasedimentay and metavolcanic rocks during the later Precambrian or early Cambrian. The main rock types in the complex, from oldest to youngest, are fenite, pyroxenite, uncompahgrite, ijolite, nepheline syenite, and dolomitic carbonatite. The carbonatite is limonitic and forms an elliptially shaped 4 sq km stock. Calcitic and dolomitic carbonatite dikes are also numerous throughout the complex and in the pre-existing rocks. Pyroxenite is the most widespread rock type within the complex, but pyroxene is extensively altered to biotite, phlogopite, and vermiculite. Fenite, which formed through Na, K-metasomatism of the country rocks, typically contains more feldspar and less quartz than the equivalent unaltered country rocks. The other alkalic rock types are less widespread and less well exposed. Parts of the complex are covered by Oligocene ash-flow tuff and alluvial, colluvial, and glacial deposits. Sagebrush and grass cover is moderately dense to very dense at low to intermediate elevations; coniferous tree cover is dense at high elevations and on some north-facing slopes at lower elevations. A new algorithm was used to compute spectral emissivity ratios, independent of any emissivity assumptions. This algorithm has the advantage that any of the possible emissivity ratios can be computed and, thus, a large variety of composite ratio images can be constructed, which permits examination of various geologic hypotheses based on the spectral properties of the surface materials.

Rowan, Lawrence C.↗