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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 161 - 180 de 320.544

  1. Achievable Human Exploration of Mars: Highlights from The Fourth Community Workshop (AM IV)

    Thronson, Harley; Cassady, Joseph
    About a half decade ago, several professionals working mainly in industry on scenarios for initial human exploration of Mars together recognized that, under generally similar assumptions, there was a fair degree of similarity among these scenarios. Moreover, opportunities should be sought for greater community input into NASA's own scenario-building for the future of human space flight. A series of focused community workshops were considered to be effective to assess these scenarios and involve more directly the science community, including planetary protection, with industry. Four workshops to date each involve about sixty professional scientists, engineers, technologists, and strategists from NASA, academia,...

  2. Observing Planetary Rings and Small Satellites with the James Webb Space Telescope: Science Justification and Observation Requirements

    Milam, Stefanie N.; Hedman, Matthew M.; Tiscareno, Matthew S.; Cuzzi, Jeffrey N.; Tamayo, Daniel; Hamilton, Douglas P.; Verbiscer, Anne J.; Stansberry, John A.; Nicholson, Philip D.; French, Richard G.; Showalter, Mark R.; de Pater, Imke; Burns, Joseph A.
    The James Webb Space Telescope (JWST) will provide unprecedented opportunities to observe the rings and small satellites in our Solar System, accomplishing three primary objectives: (1) discovering new rings and moons, (2) unprecedented spectroscopy, and (3) time-domain observations. We give details on these science objectives and describe requirements that JWST must fulfill in order to accomplish the science objectives.

  3. Solar System Observations with the James Webb Space Telescope

    Chanover, Nancy; Ferruit, Pierre; Hammel, Heidi; Norwood, James; Sonneborn, George; Stansberry, John; Tiscareno, Matthew; Lunine, Jonathan; Milam, Stefanie; Hines, Dean; Brown, Michael
    The James Webb Space Telescope (JWST) will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in...

  4. Plasma Clouds and Snowplows: Bulk Plasma Escape from Mars Observed by MAVEN

    Halekas, J. S.; Brain, D. A.; DiBraccio, G. A.; Harada, Y.; McFadden, J. P.; Espley, J. R.; Hara, T.; Jakosky, B. M.; Ruhunusiri, S.; Mitchell, D. L.; Mazelle, C.; Connerney, J. E. P.
    We present initial Mars Atmosphere and Volatile EvolutioN (MAVEN) observations and preliminary interpretation of bulk plasma loss from Mars. MAVEN particle and field measurements show that planetary heavy ions derived from the Martian atmosphere can escape in the form of discrete coherent structures or "clouds." The ions in these clouds are unmagnetized or weakly magnetized, have velocities well above the escape speed, and lie directly downstream from magnetic field amplifications, suggesting a "snowplow" effect. This postulated escape process, similar to that successfully used to explain the dynamics of active gas releases in the solar wind and terrestrial magnetosheath, relies on...

  5. MAVEN Observations of Energy-Time Dispersed Electron Signatures in Martian Crustal Magnetic Fields

    Larson, D. E.; Hara, T.; Mitchell, D. L.; McFadden, J. P.; Halekas, J. S.; Ruhunusiri, S.; Brain, D. A.; Connerney, J. E. P.; Espley, J.; Harada, Y.; Mazelle, C.; Jakosky, B. M.; DiBraccio, G. A.; Livi, R.; Lillis, R. J.
    Energy-time dispersed electron signatures are observed by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission in the vicinity of strong Martian crustal magnetic fields. Analysis of pitch angle distributions indicates that these dispersed electrons are typically trapped on closed field lines formed above strong crustal magnetic sources. Most of the dispersed electron signatures are characterized by peak energies decreasing with time rather than increasing peak energies. These properties can be explained by impulsive and local injection of hot electrons into closed field lines and subsequent dispersion by magnetic drift of the trapped electrons. In addition, the dispersed flux enhancements are...

  6. Solar Wind Charge Exchange Contribution To The ROSAT Sky Survey Maps

    Liu, W.; Koutroumpa, D.; Kuntz, K. D.; Collier, M. R.; Prasai, K.; Morgan, K.; Snowden, S. L.; Ursino, E.; Chiao, M.; Porter, F. S.; Galeazzi, M.; McCammon, D.; Lallement, R.; Lepri, S. T.; Thomas, N. E.; Cravens, T.; Uprety, Y.; Walsh, B. M.
    DXL (Diffuse X-ray emission from the Local Galaxy) is a sounding rocket mission designed to estimate the contribution of solar wind charge eXchange (SWCX) to the diffuse X-ray background and to help determine the properties of the Local Hot Bubble. The detectors are large area thin-window proportional counters with a spectral response that is similar to that of the PSPC (Position Sensitive Proportional Counters) used in the ROSAT All Sky Survey (RASS). A direct comparison of DXL and RASS data for the same part of the sky viewed from quite different vantage points in the solar system, and the assumption...

  7. Seasonal and Static Gravity Field of Mars from MGS, Mars Odyssey and MRO Radio Science

    Mazarico, Erwan; Neumann, Gregory A.; Genova, Antonio; Goossens, Sander; Zuber, Maria T.; Lemoine, Frank G.; Smith, David E.
    We present a spherical harmonic solution of the static gravity field of Mars to degree and order 120, GMM-3, that has been calculated using the Deep Space Network tracking data of the NASA Mars missions, Mars Global Surveyor (MGS), Mars Odyssey (ODY), and the Mars Reconnaissance Orbiter (MRO). We have also jointly determined spherical harmonic solutions for the static and time-variable gravity field of Mars, and the Mars k 2 Love numbers, exclusive of the gravity contribution of the atmosphere. Consequently, the retrieved time-varying gravity coefficients and the Love number k 2 solely yield seasonal variations in the mass of...

  8. Wide Field-of-View Soft X-Ray Imaging for Solar Wind-Magnetosphere Interactions

    Cravens, T. E.; Walsh, B. M.; Carter, J. A.; Read, A. M.; Porter, F. S.; Connor, H. K.; Sibeck, D. G.; Thomas, N. E.; Collier, M. R.; Sembay, S.; Collado-Vega, Y.; Kuntz, K. D.; Snowden, S. L.
    Soft X-ray imagers can be used to study the mesoscale and macroscale density structures that occur whenever and wherever the solar wind encounters neutral atoms at comets, the Moon, and both magnetized and unmagnetized planets. Charge exchange between high charge state solar wind ions and exospheric neutrals results in the isotropic emission of soft X-ray photons with energies from 0.1 to 2.0 keV. At Earth, this process occurs primarily within the magnetosheath and cusps. Through providing a global view, wide field-of-view imaging can determine the significance of the various proposed solar wind-magnetosphere interaction mechanisms by evaluating their global extent and...

  9. The Development of the GSFC DORIS Contribution to ITRF2014

    Lemoine, F. G.; Le Bail, K.; Chinn, D. S.; Zelensky, N. P.; Beall, J. W.
    The NASA GSFC DORIS analysis center has processed data from January 1993 to December 2014 and provided 1141 weekly solutionsin the form of normal equations for incorporation into the DORIS solution for ITRF2014. The solution time series, designated asgscwd26, were based on tracking data to eleven DORIS satellites divided generally into seven-day arcs. With respect to the ITRF2008 submission (Le Bail et al., 2010), the measurement model was updated to model the beacon frequency variations at certain DORIS sites,to apply the DORIS antenna phase law for the Starec and Alcatel antennae, and to apply the antenna offset corrections in the...

  10. MAVEN Observation of an Obliquely Propagating Low-Frequency Wave Upstream of Mars

    Livi, R.; Harada, Y.; Mitchell, D. L.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E. P.; Collinson, G.; Jakosky, B. M.; Espley, J. R.; Ruhunusiri, Suranga; Larson, D. E.; Brain, D.; Mazelle, C.
    We report Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observations of a large amplitude low-frequency plasma wave that propagated oblique to the ambient magnetic field upstream of Mars along with a non-solar-wind plasma component that had a flow velocity perpendicular to the magnetic field. We consider nine possibilities for this wave that include various combinations of its propagation direction, polarization in the solar wind frame, and ion source responsible for its generation. Using the observed wave parameters and the measured plasma parameters as constraints, we uniquely identify the wave by systematically discarding these possibilities. We determine that the wave is...

  11. A Comparative Analysis of the Magnetic Field Signals over Impact Structures on the Earth, Mars and the Moon

    Purucker, Michael; Isac, Anca; Langlais, Benoit; Mandea, Mioara
    An improved description of magnetic fields of terrestrial bodies has been obtained from recent space missions, leading to a better characterization of the internal fields including those of crustal origin. One of the striking differences in their crustal magnetic field is the signature of large impact craters. A comparative analysis of the magnetic characteristics of these structures can shed light on the history of their respective planetary-scale magnetic dynamos. This has motivated us to identify impact craters and basins, first by their quasi-circular features from the most recent and detailed topographic maps and then from available global magnetic field maps....

  12. An Infrared Search for HDO in Comet D/2012 S1 (ISON) and Implications for iSHELL

    Gibb, Erika L.; Mumma, Michael J.; Bonev, Boncho P.; Paganini, Lucas; Villanueva, Geronimo L.; DiSanti, Michael A.
    We performed a sensitive search for HDO in comet D/2012 S1 (ISON) on 2013 November 16, 17, and 22 using CSHELL and the NASA Infrared Telescope Facility. We constrained the HDO/H2O ratio to less than 2.0 VSMOW (the terrestrial ocean value) at the 3 sigma uncertainty level from two independent measurements corresponding to different H2O outgassing rates. This represents the best constrained HDO/H2O ratio for a comet using a small (3 m) telescope and illustrates that when CSHELL is replaced with iSHELL, 3 m class telescopes are still strong contenders for detecting minor volatile species in moderately bright comets.

  13. M2 Internal Tides and Their Observed Wavenumber Spectra from Satellite Altimetry*

    Zaron, E. D.; Ray, R. D.
    A near-global chart of surface elevations associated with the stationary M2 internal tide is empirically constructed from multi-mission satellite altimeter data. An advantage of a strictly empirical mapping approach is that results are independent of assumptions about ocean wave dynamics and, in fact, can be used to test such assumptions. A disadvantage is that present-day altimeter coverage is only marginally adequate to support mapping such short-wavelength features. Moreover, predominantly north-south ground-track orientations and contamination from nontidal oceanographic variability can lead to deficiencies in mapped tides. Independent data from Cryosphere Satellite-2 (CryoSat-2) and other altimeters are used to test the solutions...

  14. Mapping the Gas Turbulence in the Coma Cluster: Predictions for Astro-H

    Markevitch, M.; ZuHone, J. A.; Zhuravleva, I.
    Astro-H will be able for the first time to map gas velocities and detect turbulence in galaxy clusters. One of the best targets for turbulence studies is the Coma cluster, due to its proximity, absence of a cool core, and lack of a central active galactic nucleus. To determine what constraints Astro-H will be able to place on the Coma velocity field, we construct simulated maps of the projected gas velocity and compute the second-order structure function, an analog of the velocity power spectrum. We vary the injection scale, dissipation scale, slope, and normalization of the turbulent power spectrum, and...

  15. The Rate of Dielectric Breakdown Weathering of Lunar Regolith in Permanently Shadowed Regions

    Schwadron, N. A.; Jordan, A. P.; Wilson, J. K.; Stubbs, T. J.; Spence, H. E.
    Large solar energetic particle events may cause dielectric breakdown in the upper 1 mm of regolith in permanently shadowed regions (PSRs). We estimate how the resulting breakdown weathering compares to meteoroid impact weathering. Although the SEP event rates measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO) are too low for breakdown to have significantly affected the regolith over the duration of the LRO mission, regolith gardened by meteoroid impacts has been exposed to SEPs for approx.10(exp 6 yr. Therefore, we estimate that breakdown weathering's production rate of vapor and melt...

  16. The Compositional Evolution of C/2012 S1 (ISON) from Ground-Based High-Resolution Infrared Spectroscopy as Part of a Worldwide Observing Campaign

    Cochran, A.; Kobayashi, H.; DiSanti, M. A.; Weaver, H.A.; Kawakita, H.; McKay, A. J.; Harris, W. M.; Vervack, R. J., Jr.; Lisse, C. M.; Russo, N. Dello
    Volatile production rates, relative abundances, rotational temperatures, and spatial distributions in the coma were measured in C/2012 S1 (ISON) using long-slit high-dispersion (lambda/delta lambda approximately 2.5 times 10 (sup 4)) infrared spectroscopy as part of a worldwide observing campaign. Spectra were obtained on Universal Time 2013 October 26 and 28 with NIRSPEC (Near Infrared Spectrometer) at the W.M. Keck Observatory, and Universal Time 2013 November 19 and 20 with CSHELL (Cryogenic Echelle Spectrograph) at the NASA IRTF (Infrared Telescope Facility). H2O was detected on all dates, with production rates increasing markedly from (8.7 plus or minus 1.5) times 10 (sup...

  17. Goulds Belt, Interstellar Clouds, and the Eocene Oligocene Helium-3 Enhancement

    Rubincam, David Parry
    Drag from hydrogen in the interstellar cloud which formed Gould's Belt may have sent interplanetary dust particle (IDPs) and small meteoroids with embedded helium to the Earth, perhaps explaining part the helium-3 flux increase seen in the sedimentary record near the Eocene-Oligocene transition. Assuming the Solar System passed through part of the cloud, IDPs in the inner Solar System may have been dragged to Earth, while dust and small meteoroids in the asteroid belt up to centimeter size may have been dragged to the resonances, where their orbital eccentricities were pumped up into Earth-crossing orbits; however, this hypotheses does not...

  18. The Refined Shock Velocity of the X-Ray Filaments in the RCW 86 Northeast Rim

    Smith, Randall K.; Katsuda, Satoru; Yamaguchi, Hiroya; Castro, Daniel; Williams, Brian J.; Lopez, Laura A.; Slane, Patrick O.; Petre, Robert
    A precise measurement of shock velocities is crucial for constraining the mechanism and efficiency of cosmic-ray (CR) acceleration at supernova remnant (SNR) shock fronts. The northeastern rim of the SNR RCW 86 is thought to be a particularly efficient CR acceleration site, owing to the recent result in which an extremely high shock velocity of 6000 km s1 was claimed. Here, we revisit the same SNR rim with the Chandra X-ray Observatory, 11 years after the first observation. This longer baseline than previously available allows us to determine a more accurate proper motion of the nonthermal X-ray filament, revealing a...

  19. Density Variations in the Earth's Magnetospheric Cusps

    Walsh, B. M.; Welling, D. T.; Kuntz, K. D.; Mozer, F. S.; Niehof, J.; Sibeck, D. G.; Collier, M. R.; Fritz, T. A.
    Seven years of measurements from the Polar spacecraft are surveyed to monitor the variations of plasma density within the magnetospheric cusps. The spacecraft's orbital precession from 1998 through 2005 allows for coverage of both the northern and southern cusps from low altitude out to the magnetopause. In the mid- and high- altitude cusps, plasma density scales well with the solar wind density (n(sub cusp)n(sub sw) approximately 0.8). This trend is fairly steady for radial distances greater then 4 R(sub E). At low altitudes (r less than 4R(sub E)) the density increases with decreasing altitude and even exceeds the solar wind...

  20. Discovery of X-Ray Emission from the Galactic Supernova Remnant G32.8-0.1 with Suzaku

    Hewitt, John; Petre, Robert; Bamba, Aya; Bocchino, Fabrizio; Safi-Harb, Samar; Terada, Yukikatsu; Zhou, Ping; Sawada, Makoto; Angelini, Lorella
    We present the first dedicated X-ray study of the supernova remnant (SNR) G32.8-0.1 (Kes 78) with Suzaku. X-ray emission from the whole SNR shell has been detected for the first time. The X-ray morphology is well correlated with the emission from the radio shell, while anti-correlated with the molecular cloud found in the SNR field. The X-ray spectrum shows not only conventional low-temperature (kT approximately 0.6 kiloelectronvolts) thermal emission in a nonequilibrium ionization state, but also a very high-temperature (approximately 3.4 kiloelectronvolts) component with a very low ionization timescale (approximately 2.7 times 10 (sup 9) per cubic centimeter per second),...

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