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NASA Technical Reports Server (NTRS) (656,804 recursos)
The NTRS is a valuable resource for students, educators, researchers, and the public for access to NASA's current and historical technical literature since it was first released in 1994. NTRS provides access to approximately 500K aerospace related citations, 90K full-text online documents, and 111K images and videos. NTRS numbers continues to grow over time as new scientific and technical information (STI) is created or funded by NASA. The type of information found in NTRS include: conference papers, images, journal articles, photos, meeting papers, movies, patents, research reports, and technical videos.

NASA Center for AeroSpace Information (CASI) (513,494) NIX Images (81,938)


Mostrando recursos 1 - 20 de 4,622

1. Evaluation of the Terminal Sequencing and Spacing System for Performance Based Navigation Arrivals - Martin, Lynne; Swenson, Harry N.; Thipphavong, Jane; Nguyen, Jimmy; Jung, Jaewoo; Lin, Melody
NASA has developed the Terminal Sequencing and Spacing (TSS) system, a suite of advanced arrival management technologies combining timebased scheduling and controller precision spacing tools. TSS is a ground-based controller automation tool that facilitates sequencing and merging arrivals that have both current standard ATC routes and terminal Performance-Based Navigation (PBN) routes, especially during highly congested demand periods. In collaboration with the FAA and MITRE's Center for Advanced Aviation System Development (CAASD), TSS system performance was evaluated in human-in-the-loop (HITL) simulations with currently active controllers as participants. Traffic scenarios had mixed Area Navigation (RNAV) and Required Navigation Performance (RNP) equipage, where...

2. Inflation Physics from the Cosmic Microwave Background and Large Scale Structure - Arnold,K.; Carlstrom, J.E.; Dodelson, S; Buder, I.; Dawson, K.S.; Das, S.; Church, S.; Crawford, T.M.; Bond, J.R.; Calabrese, E.; Cooray, A.; Benson, B.A.; Chiang, H.C.; Chang, C.L.; Austermann, J.; Burke, D.L.; Abazajian, K.N.; Wollack, E. J.; Borrill, J.; Carvalho, C.S.; Dobbs, M.; Devline, M.J.; Crill, B.P.; Bock, J.; Bischoff, C.
Fluctuations in the intensity and polarization of the cosmic microwave background (CMB) and the large-scale distribution of matter in the universe each contain clues about the nature of the earliest moments of time. The next generation of CMB and large-scale structure (LSS) experiments are poised to test the leading paradigm for these earliest moments---the theory of cosmic inflation---and to detect the imprints of the inflationary epoch, thereby dramatically increasing our understanding of fundamental physics and the early universe. A future CMB experiment with sufficient angular resolution and frequency coverage that surveys at least 1 of the sky to a depth...

3. Bioculture System Expanding ISS Capabilities for Space Biosciences Research and Commercial Applications - Sato, Kevin Y.
Oral presentation at the ASGSR 2013 Annual Meeting. The presentation describes the NASA Bioculture System hardware design, capabilities, enabling science research capabilities, and flight concept of operations. The presentation is part of the Enabling Technologies special session and will be presented to perspective users in both academics and commercial communities.

4. Simulation of Image Performance Characteristics of the Landsat Data Continuity Mission (LDCM) Thermal Infrared Sensor (TIRS) - Gartley, Michael; Schott, John; Montanaro, Matthew; Gerace, Aaron; Reuter, Dennis C.; Brown, Scott
The next Landsat satellite, which is scheduled for launch in early 2013, will carry two instruments: the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). Significant design changes over previous Landsat instruments have been made to these sensors to potentially enhance the quality of Landsat image data. TIRS, which is the focus of this study, is a dual-band instrument that uses a push-broom style architecture to collect data. To help understand the impact of design trades during instrument build, an effort was initiated to model TIRS imagery. The Digital Imaging and Remote Sensing Image Generation (DIRSIG) tool was...

5. Green Solvents for Precision Cleaning - Grandelli, Heather; Surma, Jan; Maloney, Phillip; DeVor, Robert; Hintze, Paul
Aerospace machinery used in liquid oxygen (LOX) fuel systems must be precision cleaned to achieve a very low level of non-volatile residue (< 1 mg0.1 m2), especially flammable residue. Traditionally chlorofluorocarbons (CFCs) have been used in the precision cleaning of LOX systems, specifically CFC 113 (C2Cl3F3). CFCs have been known to cause the depletion of ozone and in 1987, were banned by the Montreal Protocol due to health, safety and environmental concerns. This has now led to the development of new processes in the precision cleaning of aerospace components. An ideal solvent-replacement is non-flammable, environmentally benign, non-corrosive, inexpensive, effective and...

6. Motivation and Prospects for Spatio-spectral Interferometry in the Far-infrared - Leisawitz, David
Consensus developed through a series of workshops, starting in 1998. Compelling science case for high angular resolution imaging and spectroscopy, and mission concepts. A robust plan - it has evolved over the years, but has consistently called for high resolution.

7. Two Distinct Roles of Atlantic SSTs in ENSO Variability: North Tropical Atlantic SST and Atlantic Nino - Kug, Jong-Seong; Park, Jong-Yeon; Ham, Yoo-Geun
Two distinct roles of the Atlantic sea surface temperatures (SSTs), namely, the North Tropical Atlantic (NTA) SST and the Atlantic Nino, on the El Nino-Southern Oscillation (ENSO) variability are investigated using the observational data from 1980 to 2010 and coupled model experiments. It appears that the NTA SST and the Atlantic Nino can be used as two independent predictors for predicting the development of ENSO events in the following season. Furthermore, they are likely to be linked to different types of El Nino events. Specifically, the NTA SST cooling during February, March, and April contributes to the central Pacific warming...

8. Visualization of Monitoring Data at the NASA Advanced Supercomputing Facility - Singh, Janice Shobha
No abstract available

9. The NASA Polarimetric Radar (NPOL) - Petersen, Walter A.; Wolff, David B.
Characteristics of the NASA NPOL S-band dual-polarimetric radar are presented including its operating characteristics, field configuration, scanning capabilities and calibration approaches. Examples of precipitation science data collections conducted using various scan types, and associated products, are presented for different convective system types and previous field campaign deployments. Finally, the NASA NPOL radar location is depicted in its home base configuration within the greater Wallops Flight Facility precipitation research array supporting NASA Global Precipitation Measurement Mission ground validation.

10. High Dynamic Range (HDR) Imaging Launch Footage - Karr, Brian A.
High Dynamic Range (HDR) Imaging

11. Stress-Dependent Voltage Offsets From Polymer Insulators Used in Rock Mechanics and Material Testing - Gray, Amber; Carlson, G. G.; Dahlgren, Robert; Johnston, M. J.; Dunson, C.; Vanderbilt, V. C.; Freund, F.
Dielectric insulators are used in a variety of laboratory settings when performing experiments in rock mechanics, petrology, and electromagnetic studies of rocks in the fields of geophysics,material science, and civil engineering. These components may be used to electrically isolate geological samples from the experimental equipment, to perform a mechanical compliance function between brittle samples and the loading equipment, to match ultrasonic transducers, or perform other functions. In manyexperimental configurations the insulators bear the full brunt of force applied to the sample but do not need to withstand high voltages, therefore the insulators are often thin sheets of mechanically tough polymers....

12. The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog - Cohen, Martin; Wachter, Stefanie; Leisawitz, David T.; Debes, John H.; Hoard, D.W.
We have compiled photometric data from the Wide-field Infrared Survey Explorer All Sky Survey and other archival sources for the more than 2200 objects in the original McCook & Sion Catalog of Spectroscopically Identified White Dwarfs. We applied color-selection criteria to identify 28 targets whose infrared spectral energy distributions depart from the expectation for the white dwarf photosphere alone. Seven of these are previously known white dwarfs with circumstellar dust disks, five are known central stars of planetary nebulae, and six were excluded for being known binaries or having possible contamination of their infrared photometry. We fit white dwarf models...

13. Linkages Between Ozone-depleting Substances, Tropospheric Oxidation and Aerosols - Faluvegi, G.; Shindell, D. T.; Voulgarakis, A.
Coupling between the stratosphere and the troposphere allows changes in stratospheric ozone abundances to affect tropospheric chemistry. Large-scale effects from such changes on chemically produced tropospheric aerosols have not been systematically examined in past studies. We use a composition-climate model to investigate potential past and future impacts of changes in stratospheric ozone depleting substances (ODS) on tropospheric oxidants and sulfate aerosols. In most experiments, we find significant responses in tropospheric photolysis and oxidants, with small but significant effects on methane radiative forcing. The response of sulfate aerosols is sizeable when examining the effect of increasing future nitrous oxide (N2O) emissions....

14. Follow on Research for Multi-Utility Technology Test Bed Aircraft at NASA Dryden Flight Research Center (FY13 Progress Report) - Pak, Chan-Gi
Modern aircraft employ a significant fraction of their weight in composite materials to reduce weight and improve performance. Aircraft aeroservoelastic models are typically characterized by significant levels of model parameter uncertainty due to the composite manufacturing process. Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of Multi Utility Technology Test-bed (MUTT) aircraft is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and...

15. Tropospheric Delay Effects in Radio Interferometry - Lanyi, G.
A new tropospheric mapping function is derived which is more accurate than previous mapping functions above elevations of 4 degrees. The error due to the given analytic approximation is estimated to be less than 0.02% for elevation angles larger than 6 degrees, (less than 0.4 cm at 6 degrees, and approximately 0.004% or 0.03 cm at 20 degrees). The mathematical expansion used in the derivation is valid for any laterally homogeneous atmospheric model of refractivity. The new mapping function, computer generated ray tracing tables and other mapping functions are compared. The results can be used in correcting for tropospheric delays...

16. Multilayer Pressure Vessel Materials Testing and Analysis Phase 2 - Cardinal, Joseph W.; Popelar, Carl F.
To provide NASA with a suite of materials strength, fracture toughness and crack growth rate test results for use in remaining life calculations for the vessels described above, Southwest Research Institute® (SwRI®) was contracted in two phases to obtain relevant material property data from a representative vessel. An initial characterization of the strength, fracture and fatigue crack growth properties was performed in Phase 1. Based on the results and recommendations of Phase 1, a more extensive material property characterization effort was developed in this Phase 2 effort. This Phase 2 characterization included additional strength, fracture and fatigue crack growth of...

17. Cyclic Crack Growth Testing of an A.O. Smith Multilayer Pressure Vessel with Modal Acoustic Emission Monitoring and Data Assessment - Ziola, Steven M.
Digital Wave Corp. (DWC) was retained by Jacobs ATOM at NASA Ames Research Center to perform cyclic pressure crack growth sensitivity testing on a multilayer pressure vessel instrumented with DWC's Modal Acoustic Emission (MAE) system, with captured wave analysis to be performed using DWCs WaveExplorerTM software, which has been used at Ames since 2001. The objectives were to document the ability to detect and characterize a known growing crack in such a vessel using only MAE, to establish the sensitivity of the equipment vs. crack size and / or relevance in a realistic field environment, and to obtain fracture toughness...

18. Multilayer Pressure Vessel Materials Testing and Analysis - Popelar, Carl F.; Page, Richard A.; Cardinal, Joseph W.
To provide NASA a comprehensive suite of materials strength, fracture toughness and crack growth rate test results for use in remaining life calculations for aging multilayer pressure vessels, Southwest Research Institute (R) (SwRI) was contracted in two phases to obtain relevant material property data from a representative vessel. This report describes Phase 1 of this effort which includes a preliminary material property assessment as well as a fractographic, fracture mechanics and fatigue crack growth analyses of an induced flaw in the outer shell of a representative multilayer vessel that was subjected to cyclic pressure test. SwRI performed this Phase 1...

19. Salt Tolerance and Polyphyly in the Cyanobacterium Chroococcidiopsis (Pleurocapsales)1 - Rothschild, Lynn J.; Cumbers, John Robert
Chroococcidiopsis Geitler (Geitler 1933) is a genus of cyanobacteria containing desiccation and radiation resistant species. Members of the genus live in habitats ranging from hot and cold deserts to fresh and saltwater environments. Morphology and cell division pattern have historically been used to define the genus. To better understand the genetic and phenotypic diversity of the genus, 15 species were selected that had been previously isolated from different locations, including salt and freshwater environments. Four markers were sequenced from these 15 species, the 16S rRNA, rbcL, desC1 and gltX genes. Phylogenetic trees were generated which identified two distinct clades, a...

20. An Icy Kuiper Belt Around the Young Solar-type Star HD 181327 - Donaldson, J; Maddison, S. T.; Grady C. A.; Pinte, C.; Lebreton, J.; Pantin, E.; Gonzalez, J.-F.; Duchene, G.; Dent, W. R. F.; Matthews, G. S.; Meeus,G.; Kamp, I.; Augereau, J.-C.; Schneider, G.; Barrado, D.; Woitke, P.; Roberge, A.; Thi, W.-F.; Menard, F.; Riviere-Marichalar, P.; Williams, J. P.
Context. HD 181327 is a young main sequence F5/F6 V star belonging to the Beta Pictoris moving group (age approx.. 12 Myr). It harbors an optically thin belt of circumstellar material at radius approx.. 90 AU, presumed to result from collisions in a population of unseen planetesimals. Aims. We aim to study the dust properties in the belt in details, and to constrain the gas-to-dust ratio. Methods. We obtained far-infrared photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory, complemented by new 3.2 mm observations carried with the ATCA array. The geometry of the belt...

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