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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Nitrogen and Oxygen Photochemistry following SL9

The collision of Shoemaker Levy 9 (SL9) with Jupiter caused many new molecular species to be deposited in the Jovian stratosphere. We use a photochemical model to follow the evolution of the impact derived species. Our results regarding the nitrogen and oxygen compounds are presented here. NH3 photolysis initiates the nitrogen photochemistry. Much of the nitrogen ends up in N2, nitrogen-sulfur compounds, and HCN, but NH3 and nitriles such as C2H3CN may also exist in observable quantities for a year or so after the impacts. Oxygen species survive for a long time in the Jovian stratosphere. The only major oxygen containing compounds that exhibit dramatic changes in the lower stratosphere in the first year following the impacts are SO, SO2, and OCS - H2O, CO2, and CO are comparatively stable. We discuss the important photochemical processes operating on the nitrogen and oxygen species in the Jovian stratosphere, make prediction concerning the temporal variation of the major species, and identify molecules that might act as good tracers for atmospheric dynamics.

Moses, Julianne I.↗
NASA NTRS1995

Nonlinear Coherent Optical Image Processing Using Logarithmic Transmittance of Bacteriorhodopsin Films

The transmission properties of some bacteriorhodopsin-film spatial light modulators are uniquely suited to allow nonlinear optical image-processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude-transmission characteristic of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. I present experimental results demonstrating the principle and the capability for several different image and noise situations, including deterministic noise and speckle. The bacteriorhodopsin film studied here displays the logarithmic transmission response for write intensities spanning a dynamic range greater than 2 orders of magnitude.

Downie, John D.↗
NASA NTRS1997

Scaling Impact-Melt and Crater Dimensions: Implications for the Lunar Cratering Record

The consequences of impact on the solid bodies of the solar system are manifest and legion. Although the visible effects on planetary surfaces, such as the Moon's, are the most obvious testimony to the spatial and temporal importance of impacts, less dramatic chemical and petrographic characteristics of materials affected by shock abound. Both the morphologic and petrologic aspects of impact cratering are important in deciphering lunar history, and, ideally, each should complement the other. In practice, however, a gap has persisted in relating large-scale cratering processes to petrologic and geochemical data obtained from lunar samples. While this is due in no small part to the fact that no Apollo mission unambiguously sampled deposits of a large crater, it can also be attributed to the general state of our knowledge of cratering phenomena, particularly those accompanying large events. The most common shock-metamorphosed lunar samples are breccias, but a substantial number are impact-melt rocks. Indeed, numerous workers have called attention to the importance of impact-melt rocks spanning a wide range of ages in the lunar sample collection. Photogeologic studies also have demonstrated the widespread occurrence of impact-melt lithologies in and around lunar craters. Thus, it is clear that impact melting has been a fundamental process operating throughout lunar history, at scales ranging from pits formed on individual regolith grains to the largest impact basins. This contribution examines the potential relationship between impact melting on the Moon and the interior morphologies of large craters and peaking basins. It then examines some of the implications of impact melting at such large scales for lunar-sample provenance and evolution of the lunar crust.

Cintala , Mark J.↗
NASA NTRS1997

Automatic registration of satellite imagery

Image registration is one of the basic image processing operations in remote sensing. With the increase in the number of images collected every day from different sensors, automated registration of multi-sensor/multi-spectral images has become an important issue. A wide range of registration techniques has been developed for many different types of applications and data. The objective of this paper is to present an automatic registration algorithm which uses a multiresolution analysis procedure based upon the wavelet transform. The procedure is completely automatic and relies on the grey level information content of the images and their local wavelet transform modulus maxima. The registration algorithm is very simple and easy to apply because it needs basically one parameter. We have obtained very encouraging results on test data sets from the TM and SPOT sensor images of forest, urban and agricultural areas.

Fonseca, Leila M. G.↗
NASA NTRS1997

[Activities of Dept. of Geological Sciences, Colorado University]

Using remotely sensed data and GPS observations we completed a study of neotectonic processes responsible for landscape changes in an area of active extensional deformation and volcanism. The findings from this study describe the extensional processes operating in the region of the Afar triple junction and the northern Ethiopian rift.

Bilham, Roger↗
NASA NTRS2000

The Impact of ENSO on Extratropical Low Frequency Noise in Seasonal Forecasts

This study examines the uncertainty in forecasts of the January-February-March (JFM) mean extratropical circulation, and how that uncertainty is modulated by the El Nino/Southern Oscillation (ENSO). The analysis is based on ensembles of hindcasts made with an Atmospheric General Circulation Model (AGCM) forced with sea surface temperatures observed during; the 1983 El Nino and 1989 La Nina events. The AGCM produces pronounced interannual differences in the magnitude of the extratropical seasonal mean noise (intra-ensemble variability). The North Pacific, in particular, shows extensive regions where the 1989 seasonal mean noise kinetic energy (SKE), which is dominated by a "PNA-like" spatial structure, is more than twice that of the 1983 forecasts. The larger SKE in 1989 is associated with a larger than normal barotropic conversion of kinetic energy from the mean Pacific jet to the seasonal mean noise. The generation of SKE due to sub-monthly transients also shows substantial interannual differences, though these are much smaller than the differences in the mean flow conversions. An analysis of the Generation of monthly mean noise kinetic energy (NIKE) and its variability suggests that the seasonal mean noise is predominantly a statistical residue of variability resulting from dynamical processes operating on monthly and shorter times scales. A stochastically-forced barotropic model (linearized about the AGCM's 1983 and 1989 base states) is used to further assess the role of the basic state, submonthly transients, and tropical forcing, in modulating the uncertainties in the seasonal AGCM forecasts. When forced globally with spatially-white noise, the linear model generates much larger variance for the 1989 base state, consistent with the AGCM results. The extratropical variability for the 1989 base state is dominanted by a single eigenmode, and is strongly coupled with forcing over tropical western Pacific and the Indian Ocean, again consistent with the AGCM results. Linear calculations that include forcing from the AGCM variance of the tropical forcing and submonthly transients show a small impact on the variability over the Pacific/North American region compared with that of the base state differences.

Schubert, Siegfried D.↗
NASA NTRS2001

The Magnetospheric Constellation Mission. Dynamic Response and Coupling Observatory (DRACO): Understanding the Global Dynamics of the Structured Magnetotail

Magnetospheric Constellation Dynamic Response and Coupling Observatory (DRACO) is the Solar Terrestrial Probe (STP) designed to understand the nonlinear dynamics, responses, and connections within the Earth's structured magnetotail, using a constellation of approximately 50 to 100 distributed vector measurement spacecraft. DRACO will reveal magnetotail processes operating within a domain extending 20 Earth radii (R(sub E)) across the tail and 40 R(sub E)down the tail, on spatial and time scales accessible to global circulation models, i.e., approximately 2 R(sub E) and 10 seconds.

Source record↗
NASA NTRS1994

Nonlinear Optical Image Processing with Bacteriorhodopsin Films

The transmission properties of some bacteriorhodopsin film spatial light modulators are uniquely suited to allow nonlinear optical image processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude transmission feature of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. The bacteriorhodopsin film displays the logarithmic amplitude response for write beam intensities spanning a dynamic range greater than 2.0 orders of magnitude. We present experimental results demonstrating the principle and capability for several different image and noise situations, including deterministic noise and speckle. Using the bacteriorhodopsin film, we successfully filter out image noise from the transformed image that cannot be removed from the original image.

Downie, John D.↗
NASA NTRS2001

Theoretical Basis for the Surface Spectral Reflectance Relationships Used in the MODIS Aerosol Algorithm

The analysis of data from the MODIS instrument on the Terra platform to derive global distribution of aerosols assumes a set of relationships between the blue, rho (sub blue), the red, rho (sub red), and 2.1 micrometers, rho (sub 2.1), spectral channels. These relations have been established from a series of measurements indicating that rho (sub blue) approximately 0.5 rho (sub red) approximately 0.25 rho (sub 2.1). Here we use a model to describe the transfer of radiation through a vegetation canopy composed of randomly oriented leaves to assess the theoretical foundations for these relationships. The influence of varying fractional vegetation coverage is simulated simply as a linear combination of pure soil and pure vegetation conditions, also known as Independent Pixel Approximation (IPA). Calculations for a wide range of leaf area indices and vegetation fractions show that rho (sub blue) is consistently about 1/4 of rho (sub 2.1) as used by MODIS for the whole range of analyzed cases, except for very dark soils, such as those found in burn scars. For its part, the ratio rho (sub red)/rho (sub 2.1) varies from less than the empirically derived value of 1/2 for dense and dark vegetation (rho (sub 2.1) less than 0.1), to more than 1/2 for bright mixture of soil and vegetation. This is in agreement with measurements over uniform dense vegetation, but not with measurements over mixed dark scenes. In the later case, the discrepancy is probably mitigated by shadows due to uneven canopy and terrain on a large scale. It is concluded that the value of this ratio should ideally be made dependent on the land cover type in the operational processing of MODIS data, especially over dense forests.

Kaufman, Yoram J.↗
NASA NTRS1999

Going Paperless

Sentel Corporation has commercialized NASA's Electronic Portable Information Collection (EPIC) System, which stemmed from a NASA Kennedy Space Center SBIR contract. NASA and Sentel designed, built, and tested work authorization procedures used as a paperless procedures system for Space Shuttle and International Space Station payload processing operations. EPIC is now being applied to various markets including; airplane maintenance, aerospace system data management, shipbuilding industries, shipping industries, law enforcement agencies, and public utilities. KSC is planning a pilot program to use EPIC at the Hypergol Maintenance Facility. In addition, Ames Research Center and KSC are working together to apply EPIC to the area of wireless communication.

Source record↗
NASA NTRS1992

Valve Packing

"S Glass" yarn was originally developed by NASA for high temperature space and aeronautical applications. When John Crane, Inc. required material that would withstand temperatures higher than 1,200 degrees Fahrenheit, they contacted Owens-Corning, which had developed a number of applications for the material. John Crane combines the yarn with other components to make Style 287-I packing. The product can be used in chemical processing operations, nuclear power stations, petroleum products, etc. Advantages include increased service life and reduced maintenance costs.

Source record↗
NASA NTRS2002

Relationship Between Surface Reflectance in the Visible and Mid-IR used in MODIS Aerosol Algorithm-Theory

Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument that flies in polar orbit on the Terra platform, are used to derive the aerosol optical thickness and properties over land and ocean. The relationships between visible reflectance (at blue, rho(sub blue), and red, rho(sub red)) and mid-infrared (at 2.1 microns, rho(sub 2.1)) are used in the MODIS aerosol retrieval algorithm to derive global distribution of aerosols over the land. These relations have been established from a series of measurements indicating that rho(sub blue) is approximately 0.5 rho(sub red) is approximately 0.25 rho(sub 2.1). Here we use a model to describe the transfer of radiation through a vegetation canopy composed of randomly oriented leaves to assess the theoretical foundations for these relationships. Calculations for a wide range of leaf area indices and vegetation fractions show that rho(sub blue) is consistently about 1/4 of rho(sub 2.1) as used by MODIS for the whole range of analyzed cases, except for very dark soils, such as those found in burn scars. For its part, the ratio rho(sub red)/rho(sub 2.1) varies from less than the empirically derived value of 1/2 for dense and dark vegetation, to more than 1/2 for bright mixture of soil and vegetation. This is in agreement with measurements over uniform dense vegetation, but not with measurements over mixed dark scenes. In the later case the discrepancy is probably mitigated by shadows due to uneven canopy and terrain on a large scale. It is concluded that the value of this ratio should ideally be made dependent on the land cover type in the operational processing of MODIS data, especially over dense forests.

Kaufman, Yoram J.↗
NASA NTRS1982

Synoptic and Mesoscale Cloud Tracking

The papers in this section include: 1)'Wind Derivation from Geostationary Satellites'; 2) 'The Operational Processing of Wind Estimates from Cloud Motions: Past, Present, and Future'; 3) 'Intercomparision of SMS Wind Sets: A Study Using Rapid Scan Imagery'; 4) 'Mesoscale Wind Fields for a Severe Storm Situation Determined from SMS Cloud Observations'; 5) 'Moisture Convergence Using Satellite-Derived Wind Fields: A Severe Local Storm Case Study'

Wilson, G.↗
NASA NTRS1999

Discovery of a Three-Layered Atmospheric Structure in Accretion Disks around Stellar-Mass Black Holes

We have carried out systematic modeling of the X-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40, using our newly developed spectral fitting methods. Our results reveal, for the first time, a three-layered structure of the atmosphere in the inner region of the accretion disks. Above the conanonly known, cold and optically thick disk of a blackbody temperature 0.2-0.5 keV, there is a layer of warm gas with a temperature of 1.0-1.5 keV and an optical depth of around 10. Compton scattering of the underlying disk blackbody photons produces the soft X-ray component we comonly observe. Under certain conditions, there is also a much hotter, optically thin corona above the warm layer, characterized by a temperature of 100 keV or higher and an optical depth of unity or less. The corona produces the hard X-ray component typically seen in these sources. We emphasize that the existence of the warm layer seem to be independent of the presence of the hot corona and, therefore, it is not due to irradiation of the disk by hard X-rays from the corona. Our results suggest a striking structural similarity between the accretion disks and the solar atmosphere, which may provide a new stimulus to study the common underlying physical processes operating in these vastly different systems. We also report the first unambiguous detection of an emission line around 6.4 keV in GRO J1655-40, which may allow further constraining of the accretion disk structure. We acknowledge NASA GSFC and MFC for partial financial support. (copyright) 1999: American Astronomical Society. All rights reverved.

Zhang, S. N.↗
NASA NTRS2000

Analysis of edible oil processing options for the BIO-Plex advanced life support system

Edible oil is a critical component of the proposed plant-based Advanced Life Support (ALS) diet. Soybean, peanut, and single-cell oil are the oil source options to date. In terrestrial manufacture, oil is ordinarily extracted with hexane, an organic solvent. However, exposed solvents are not permitted in the spacecraft environment or in enclosed human tests by National Aeronautics and Space Administration due to their potential danger and handling difficulty. As a result, alternative oil-processing methods will need to be utilized. Preparation and recovery options include traditional dehulling, crushing, conditioning, and flaking, extrusion, pressing, water extraction, and supercritical extraction. These processing options were evaluated on criteria appropriate to the Advanced Life Support System and BIO-Plex application including: product quality, product stability, waste production, risk, energy needs, labor requirements, utilization of nonrenewable resources, usefulness of by-products, and versatility and mass of equipment to determine the most appropriate ALS edible oil-processing operation.

NASA Discipline Life Support Systems↗
NASA NTRS1989

Secular change in chert distribution: a reflection of evolving biological participation in the silica cycle

In the modern oceans, the removal of dissolved silica from sea water is principally a biological process carried out by diatoms, with lesser contributions from radiolaria, silicoflagellates, and sponges. Because such silica in sediments is often redistributed locally during diagenesis to from nodular or bedded chert, stratigraphic changes in the facies distribution of early diagenetic chert provide important insights into the development of biological participation in the silica cycle. The abundance of chert in upper Proterozoic peritidal carbonates suggests that at this time silica was removed from seawater principally by abiological processes operating in part of the margins of the oceans. With the evolution of demosponges near the beginning of the Cambrian Period, subtidal biogenetic cherts became increasingly common, and with the Ordovician rise of radiolaria to ecological and biogeochemical prominence, sedimented skeletons became a principal sink for oceanic silica. Cherts of Silurian to Cretaceous age share many features of facies distribution and petrography but they differ from Cenozoic siliceous deposits. These differences are interpreted to reflect the mid-Cretaceous radiation of diatoms and their subsequent rise to domination of the silica cycle. Biogeochemical cycles provide an important framework for the paleobiological interpretation of the organisms that participate in them.

Non-NASA Center↗
NASA NTRS1994

Acquisition and processing of data for isotope-ratio-monitoring mass spectrometry

Methods are described for continuous monitoring of signals required for precise analyses of 13C, 18O, and 15N in gas streams containing varying quantities of CO2 and N2. The quantitative resolution (i.e. maximum performance in the absence of random errors) of these methods is adequate for determination of isotope ratios with an uncertainty of one part in 10(5); the precision actually obtained is often better than one part in 10(4). This report describes data-processing operations including definition of beginning and ending points of chromatographic peaks and quantitation of background levels, allowance for effects of chromatographic separation of isotopically substituted species, integration of signals related to specific masses, correction for effects of mass discrimination, recognition of drifts in mass spectrometer performance, and calculation of isotopic delta values. Characteristics of a system allowing off-line revision of parameters used in data reduction are described and an algorithm for identification of background levels in complex chromatograms is outlined. Effects of imperfect chromatographic resolution are demonstrated and discussed and an approach to deconvolution of signals from coeluting substances described.

NASA Discipline Exobiology↗
NASA NTRS2004

Choosing Mars-Time: Analysis of the Mars Exploration Rover Experience

This paper focuses on the Mars Exploration Rover (MER) mission decision to work on Mars Time and the implications of that decision on the tactical surface operations process as personnel planned activities and created a new command load for work on each Martian sol. The paper also looks at tools that supported the complexities of Mars Time work, and makes some comparisons between Earth and Mars time scheduling.

Bass, Deborah S.↗