Recursos de colección

NASA Technical Reports Server (NTRS) (685.125 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.

Mostrando recursos 21 - 40 de 320.544

  1. Astromaterials Curation Online Resources for Principal Investigators

    Todd, Nancy S.; Zeigler, Ryan A.; Mueller, Lina
    The Astromaterials Acquisition and Curation office at NASA Johnson Space Center curates all of NASA's extraterrestrial samples, the most extensive set of astromaterials samples available to the research community worldwide. The office allocates ~1500 individual samples to researchers and students each year and has served the planetary research community for 45+ years. The Astromaterials Curation office provides access to its sample data repository and digital resources to support the research needs of sample investigators and to aid in the selection and request of samples for scientific study. These resources can be found on the Astromaterials Acquisition and Curation website at...

  2. Accurate Characterization of Rain Drop Size Distribution Using Meteorological Particle Spectrometer and 2D Video Disdrometer for Propagation and Remote Sensing Applications

    Gatlin, Patrick; Bringi, Viswanathan; Thurai, Merhala; Kennedy, Patrick; Notaros, Branislav
    Accurate measurements of rain drop size distributions (DSD), with particular emphasis on small and tiny drops, are presented. Measurements were conducted in two very different climate regions, namely Northern Colorado and Northern Alabama. Both datasets reveal a combination of (i) a drizzle mode for drop diameters less than 0.7 mm and (ii) a precipitation mode for larger diameters. Scattering calculations using the DSDs are performed at S and X bands and compared with radar observations for the first location. Our accurate DSDs will improve radar-based rain rate estimates as well as propagation predictions.

  3. Sugars and Sugar Derivatives in Residues Produced from the UV Irradiation of Astrophysical Ice Analogs

    Nuevo, M.; Sandford, S. A.; Cooper, G.
    Carbonaceous chondrites contain a large variety of organic compounds of prebiotic interest, which include amino acids, amphiphiles, nucleobases, and sugar derivatives. The presence of these compounds strongly suggests that molecules essential to life can form abiotically under astrophysical conditions. Among the sugar derivatives reported in the Murchison and Murray meteorites, only one sugar (dihydroxyacetone) was found, together with a variety of sugar alcohols and sugar acids containing up to 6 carbon atoms, including sugar acid derivatives of the biological sugars ribose and glucose. On the other hand, laboratory studies on the formation of complex organic molecules from the ultraviolet (UV)...

  4. Recent Progress in Laboratory Astrophysics and Astrochemistry Achieved with the COSmIC Facility

    Sciamma-O'Brien, Ella; Bejaoui, Salma; Salama, Farid
    We describe the characteristics and the capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to generate, process and analyze interstellar, circumstellar and planetary analogs in the laboratory. COSmIC stands for "Cosmic Simulation Chamber" and is dedicated to the study of neutral and ionized molecules and nanoparticles under the low temperature and high vacuum conditions that are required to simulate various space environments such as diffuse interstellar clouds, circumstellar outflows and planetary atmospheres. COSmIC integrates a variety of state-of-the-art instruments that allow recreating simulated space conditions to generate, process and monitor cosmic analogs in the laboratory. The...

  5. The Far-Infrared Surveyor Mission Study: Paper I, the Genesis

    Milam, S.; DiPirro, M.; Flores, A.; Battersby, C.; Meixner, M.; Cooray, A.; Bradford, C. M.; Leisawitz, D.; Armus, L.; Roellig. T.; Bergin, E.; Carter, R.; Ennico, K.
    This paper describes the beginning of the Far-Infrared Surveyor mission study for NASA's Astrophysics Decadal 2020. We describe the scope of the study, and the open process approach of the Science and Technology Definition Team. We are currently developing the science cases and provide some preliminary highlights here. We note key areas for technological innovation and improvements necessary to make a Far-Infrared Surveyor mission a reality.

  6. Transiting Exoplanet Studies and Community Targets for JWST's Early Release Science Program

    Angerhausen, Daniel; Curry, S. M.; Charbonneau, David; Krick, J. E.; Birkmann, Stephan M.; Dalba, Paul A.; Agol, Eric; Mandell, Avi M.; Burrows, Adam; Lewis, Nikole K.; Fraine, Jonathan; Bean, Jacob L.; Line, Michael R.; Barstow, Joanna K.; Beichman, Charles; Wakeford, Hannah R.; Crouzet, Nicolas; Cubillos, Patricio E.; Valenti, Jeff A.; Cowan, Nicolas B.; Kilpatrick, Brian M.; Stevenson, Kevin B.; Lothringer, Joshua D.; de Wit, Julien; Greene, Thomas P.
    The James Webb Space Telescope (JWST) will likely revolutionize transiting exoplanet atmospheric science, due to a combination of its capability for continuous, long duration observations and its larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) Cycle1 program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to...

  7. Clast Selection and Metallographic Cooling Rates: Initial Results on Type 1A and 2A Mesosiderites

    Baecker, B.; Frasl, B.; Corrigan, C. M.; Cohen, B. A.; Rubin, A. E.
    We initiated a comprehensive study on selected clasts and metal of mesosiderites using SEM, electron microprobe and the complete suite of noble gases. Here we report initial results on the petrography of selected clasts and metallographic cooling rates using the central Ni method used in sev-eral publications. We focus on the approach of selecting grains in least recrystallized mesosiderites. Hence, especially (lithic) clasts in type 1A, 1B, 2A and 2B are the first choice. They provide highest primitive-ness and least annealing/metamorphism. All grains selected should be in close proximity to each other. Lithic clasts in mesosiderites are of high interest...

  8. Payload Design for the Lunar Flashlight Mission

    Sellar, G.; Paine, C.; Crabtree, K.; Hayne, P. O.; Paige, D. A.; Cohen, B. A.; Greenhagen, B. T.; Camacho, J. M.
    Recent reflectance data from LRO (Lunar Reconnaissance Orbiter) instruments suggest water ice and other volatiles may be present on the surface in lunar permanently shadowed regions, though the detection is not yet definitive. Understanding the composition, quantity, distribution, and form of water and other volatiles associated with lunar permanently shadowed regions (PSRs) is identified as a NASA Strategic Knowledge Gap (SKG). These polar volatile deposits are also scientifically interesting, having the potential to reveal important information about the delivery of water to the Earth-Moon system.

  9. Cryogenic High Accuracy Refractive Measuring System (CHARMS): Recap of Recent Work

    Miller, Kevin H.
    No abstract available


    Zuhone, J. A.; Markevitch, M.; Zhuravleva, I.
    The published version of this paper contained an error in Figure 5. This figure is intended to show the effect on the structure function of subtracting the bias induced by the statistical and systematic errors on the line shift. The filled circles show the bias-subtracted structure function. The positions of these points in the left panel of the original figure were calculated incorrectly. The figure is reproduced below (with the original caption) with the correct values for the bias-subtracted structure function. No other computations or figures in the original manuscript are affected.

  11. A Search for O2 in CO-Depleted Molecular Cloud Cores With Herschel

    Charnley, Steven B.; Ceccarelli, Cecilia; Wirstroem, Eva S.; Cordiner, Martin
    The general lack of molecular oxygen in molecular clouds is an outstanding problem in astrochemistry. Extensive searches with the Submillimeter Astronomical Satellite, Odin, and Herschel have only produced two detections; upper limits to the O2 abundance in the remaining sources observed are about 1000 times lower than predicted by chemical models. Previous atomic oxygen observations and inferences from observations of other molecules indicated that high abundances of O atoms might be present in dense cores exhibiting large amounts of CO depletion. Theoretical arguments concerning the oxygen gas-grain interaction in cold dense cores suggested that, if O atoms could survive in...

  12. Formation and Recondensation of Complex Organic Molecules During Protostellar Luminosity Outbursts

    Charnley, Steven B.; Wirstrom, Eva S.; Taquet, Vianney
    During the formation of stars, the accretion of surrounding material toward the central object is thought to undergo strong luminosity outbursts followed by long periods of relative quiescence, even at the early stages of star formation when the protostar is still embedded in a large envelope. We investigated the gas-phase formation and recondensation of the complex organic molecules (COMs) di-methyl ether and methyl formate, induced by sudden ice evaporation processes occurring during luminosity outbursts of different amplitudes in protostellar envelopes. For this purpose, we updated a gas-phase chemical network forming COMs in which ammonia plays a key role. The model...

  13. Atmospheric Tides in Gale Crater, Mars

    Newman, C. E; Guzewich, Scott D,; Smith, M. D.; Kahanpaa, H.; de la Torre Juarez, M.; Wilson, R. J.; Harri, A.-M.; Lemmon, M.
    Atmospheric tides are the primary source of daily air pressure variation at the surface of Mars. These tides are forced by solar heating of the atmosphere and modulated by the presence of atmospheric dust, topography, and surface albedo and thermal inertia. This results in a complex mix of sun-synchronous and nonsun- synchronous tides propagating both eastward and westward around the planet in periods that are integer fractions of a solar day. The Rover Environmental Monitoring Station on board the Mars Science Laboratory has observed air pressure at a regular cadence for over 1 Mars year and here we analyze and...

  14. Hydrogen Distribution in the Lunar Polar Regions

    Boynton, W. V.; Litvak, M. L.; Bodnarik, J. G.; Sanin, A. B.; McClanaham, T. P.; Evans, L. G.; Harshmann, K.; Chin, G.; Fedosov, F.; Mitrofanov, I. G.; Bakhtin, B. N.
    We present a method of conversion of the lunar neutron counting rate measured by the Lunar Reconnaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) instrument collimated neutron detectors, to water equivalent hydrogen (WEH) in the top approximately 1 m layer of lunar regolith. Polar maps of the Moons inferred hydrogen abundance are presented and discussed.

  15. New Methods for Retrieval of Chlorophyll Red Fluorescence from Hyperspectral Satellite Instruments: Simulations and Application to GOME-2 and SCIAMACHY

    Guanter, Luis; Joiner, Joanna; Middleton, Elizabeth M.; Yoshida, Yasuko
    Global satellite measurements of solar-induced fluorescence (SIF) from chlorophyll over land and ocean have proven useful for a number of different applications related to physiology, phenology, and productivity of plants and phytoplankton. Terrestrial chlorophyll fluorescence is emitted throughout the red and far-red spectrum, producing two broad peaks near 683 and 736nm. From ocean surfaces, phytoplankton fluorescence emissions are entirely from the red region (683nm peak). Studies using satellite-derived SIF over land have focused almost exclusively on measurements in the far red (wavelengths greater than 712nm), since those are the most easily obtained with existing instrumentation. Here, we examine new ways...

  16. On the Nature of the Enigmatic Object IRAS 19312+1950: A Rare Phase of Massive Star Formation?

    Cordiner, M. A.; Milam, S. N.; Tielens, A. G. G. M.; Smith, R. G.; Keane, J. V.; Justtanont, K.; Cox, N. L. J.; Wirstrom, E. S.; Charnley, S. B.; Boogert, A. C. A.
    IRAS19312+1950 is a peculiar object that has eluded firm characterization since its discovery, with combined maser properties similar to an evolved star and a young stellar object (YSO). To help determine its true nature, we obtained infrared spectra of IRAS19312+1950 in the range 5-550 microns using the Herschel and Spitzer space observatories. The Herschel PACS maps exhibit a compact, slightly asymmetric continuum source at 170 microns, indicative of a large, dusty circumstellar envelope. The far-IR CO emission line spectrum reveals two gas temperature components: approx. = 0.22 Stellar Mass of material at 280+/-18 K, and 1.6 Me of material at...

  17. NASA Health and Air Quality Applied Sciences Team (HAQAST)

    Neu, Jessica; Liu, Yang; Freedman, Frank; Duncan, Bryan; West, Jason; Russell, Ted; Zondlo, Mark; Holloway, Tracey; Hess, Jeremy; Henze, Daven; Tong, Daniel; Fiore, Arlene; O'Neill, Susan
    Pollution monitoring, Exposure assessment, AQ forecasting, Source attribution, Quantifying emissions, External influences, Exceptional events, and Climate interactions.

  18. Using CATS Near-Real-time Lidar Observations to Monitor and Constrain Volcanic Sulfur Dioxide (SO2) Forecasts

    Hughes, E. J.; Krotkov, N. A.; da Silva, A. M.; Yorks, J.; Mcgill, M.
    An eruption of Italian volcano Mount Etna on 3 December 2015 produced fast-moving sulfur dioxide (SO2) and sulfate aerosol clouds that traveled across Asia and the Pacific Ocean, reaching North America in just 5 days. The Ozone Profiler and Mapping Suite's Nadir Mapping UV spectrometer aboard the U.S. National Polar-orbiting Partnership satellite observed the horizontal transport of the SO2 cloud. Vertical profiles of the colocated volcanic sulfate aerosols were observed between 11.5 and 13.5 km by the new Cloud Aerosol Transport System (CATS) space-based lidar aboard the International Space Station. Backward trajectory analysis estimates the SO2 cloud altitude at 7-12...

  19. Evidence for the Kinematic Sunyaev-Zel'dovich Effect with the Atacama Cosmology Telescope and Velocity Reconstruction from the Baryon Oscillation Spectroscopic Survey

    Bond, J. Richard; Smith, Kendrick M.; Aiola, Simone; Schaan, Emmanuel S.; Ferraro, Simone; Wollack, Edward J.; De Bernardis, Francesco; Ho, Shirley; Battaglia, Nicholas; Vargas-Magana, Mariana; Calabrese, Erminia
    We use microwave temperature maps from two seasons of data from the Atacama Cosmology Telescope at 146 GHz, together with the "Constant Mass" CMASS galaxy sample from the Baryon Oscillation Spectroscopic Survey to measure the kinematic Sunyaev-Zel'dovich (kSZ) effect over the redshift range z1/4 0.4-0.7. We use galaxy positions and the continuity equation to obtain a reconstruction of the line-of-sight velocity field. We stack the microwave temperature at the location of each halo, weighted by the corresponding reconstructed velocity. We vary the size of the aperture photometry filter used, thus probing the free electron profile of these halos from within...

  20. The Variations of Neutron Component of Lunar Radiation Background from LEND LRO Observations

    Sanin, A. B.; Mitrofanov, I. G.; Mokrousov, M. I.; Chin, G.; Bakhtin, B. N.; Malakhov, A.; Livengood, T. A.; Starr, R.; McClanahan, T. P.; Harshman, K.; Evans, L.G.; Sagdeev, R.; Bodnarik, J. G.; Bodnarik, W. V.; Litvak, M. L.
    Lunar neutron flux data measured by the Lunar Exploration Neutron Detector (LEND) on board NASA's Lunar Reconnaissance Orbiter (LRO) were analyzed for the period 2009-2014.We have re-evaluated the instrument's collimation capability and re-estimated the neutron counting rate measured in the Field of View (FOV) of the LEND collimated detectors, and found it to be 1.070.1counts per second. We derived the spectral density of the neutron flux for various lunar regions using our comprehensive numerical model of orbital measurements. This model takes into account the location of the LEND instrument onboard LRO to calculate the surface leakage neutron flux and its...

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