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  • Weitere Quellen  (10)
  • Lunar and Planetary Science and Exploration  (7)
  • Computer Programming and Software  (3)
  • 2015-2019  (10)
  • 2019  (5)
  • 2018  (5)
  • 1
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    Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planet-encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover's meteorological sensors, cameras, and spectrometers. Mast Camera 880-nanometer optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97 percent reduction in incident total ultraviolet solar radiation at the surface, 30 degrees Kelvin reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 pascals. No active dust-lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission's storm observations and initial results.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN66591 , GSFC-E-DAA-TN65722 , Geophysical Research Letters (ISSN 0094-8276) (e-ISSN 1944-8007); 46; 1; 71-79
    Format: application/pdf
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  • 2
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    Trade-Space Analysis Tool for Designing Constellations (TAT-C) (2018)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: While there is growing interest in implementing future NASA Earth Science missions as Distributed Spacecraft Missions (DSMs), there are currently no tool to help in the design of DSMs. The objective of our project is to provide a framework that facilitates DSM Pre-Phase A investigations and optimizes DSM designs with respect to a-priori Science goals. Our Trade-space Analysis Tool for Constellations (TAT-C) allows to investigate questions such as: "Which type of constellations should be chosen? How many spacecraft should be included in the constellation? Which design has the best cost/risk value?" This paper provides a description of the TAT-C tool and its components.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN43210 , International Geoscience And Remote Sensing Symposium 2017 (IGARSS 2017); Jul 23, 2018 - Jul 28, 2018; Fort Worth, TX; United States
    Format: application/pdf
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  • 3
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    Combining Progressive Nodal Release with the Virtual Crack Closure Technique to Model Fatigue Delamination Growth Without Re-Meshing (2018)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The present work summarizes an approach to model mixed-mode 3D fatigue crack growth using the Virtual Crack Closure Technique (VCCT) without requiring re-meshing. It is demonstrated that the proposed approach can be used to simulate crack shapes that do not conform to the underlying mesh. The proposed approach relies solely on Paris Law characterization data to model delamination growth. Growth is determined as a post-processing step at the end of each increment, and hence no convergence issues associated with the progressive nodal release are encountered. This approach can be readily applied using standard solid element formulations and is implemented via an interface user element in Abaqus/Standard.
    Schlagwort(e): Computer Programming and Software
    Materialart: NF1676L-27504 , AIAA SciTech; Jan 08, 2018 - Jan 12, 2018; Kissimmee, FL; United States
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  • 4
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    Blockchain Application Within a Multi-Sensor Satellite Architecture (2018)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: With the thrust towards multi-sensor satellite architectures for earth and space exploration, such as constellations and swarms, new technologies are required to enable the transition to this future capability. One of the areas of interest is establishing secure, efficient and prioritized data and command communication pathways among ground and space-based sources for such systems. This paper presents early research results on the potential role, capabilities and value of blockchain usage within constellation and swarm satellite architectures. It demonstrates the use of blockchain's smart contract and distributed ledger capabilities for secure and prioritized multi-sensor satellite collaborative data exchanges, as well as the logging and tracking of command and control events. Adapting and utilizing this emerging technology will aid in addressing technology gaps expected from future constellation flight architectures, such as managing collective computational operations (correlation), dynamic and autonomous observation planning, time-critical events, and provenance tied to ground and space-based autonomous operations and control recordkeeping. In this scenario blockchain is applied in encrypted command transmittal to multiple, yet specific, entities enabling acknowledgement transmittals, performance scalability, and automatic event-based triggering.
    Schlagwort(e): Computer Programming and Software
    Materialart: GSFC-E-DAA-TN61040 , Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS); Sep 11, 2018 - Sep 14, 2018; Maui, HI; United States
    Format: application/pdf
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  • 5
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    The Gas Composition and Deep Cloud Structure of Jupiter's Great Red Spot (2018)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We have obtained high-resolution spectra of Jupiter's Great Red Spot (GRS) between 4.6-5.4 microns using telescopes on Mauna Kea to derive gas abundances and to constrain its cloud structure between 0.5-5 bars. We used line profiles of deuterated methane (CH3D) at 4.66 microns to infer the presence of an opaque cloud at 5 plus or minus 1 bars. From thermochemical models, this is almost certainly a water cloud. We also used the strength of Fraunhofer lines in the GRS to obtain the ratio of reflected sunlight to thermal emission. The level of the reflecting layer was constrained to be at 570 plus or minus 30 millibars based on fitting strong NH3 lines at 5.32 microns. We identify this layer as an ammonia cloud based on the temperature where gaseous NH3 condenses. We found evidence for a strongly absorbing but not totally opaque cloud layer at pressures deeper than 1.3 bars by combining Cassini/CIRS (Composite Infrared Spectrometer) spectra of the GRS at 7.18 microns with ground-based spectra at 5 microns. This is consistent with the predicted level of an NH4SH cloud. We also constrained the vertical profile of H2O and NH3. The GRS spectrum is matched by a saturated H2O profile above an opaque water cloud at 5 bars. The pressure of the water cloud constrains Jupiter's O/H ratio to be at least 1.1 times solar. The NH3 mole fraction is 200 plus or minus 50 ppm (parts per million) for pressures between 0.7-5 bars. Its abundance is 40 ppm at the estimated pressure of the reflecting layer. We obtained 0.8 plus or minus 0.2 ppm for PH3, which is a factor of 2 higher than in the warm collar surrounding the GRS. We detected all five naturally occurring isotopes ofgermanium in GeH4 in the GRS. We obtained an average value of 0.35 plus or minus 0.05 ppb (parts per billion) for GeH4. Finally, we measured 0.8 plus or minus 0.2 ppb for CO in the deep atmosphere.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN64553 , The Astronomical Journal (ISSN 0004-6256) (e-ISSN 1538-3881); 156; 3; 101
    Format: text
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  • 6
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    Martian Dust Particle Size During the 2018 Planet-Encircling Dust Storm as Measured by the Curiosity Rover (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-09-24
    Beschreibung: We present retrievals of dust particle effective radius during the 2018 planet-encircling dust storm from the Mars Science Laboratory Curiosity rover. Four independent observations with three of the rover's instruments were used for retrievals. We find dust particle radii exceeded 4 m and possibly 5 m during the height of the storm, which represent the largest dust particles yet seen in the martian atmosphere.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN69949 , EPSC-DPS Joint Meeting 2019; Sep 15, 2019 - Sep 20, 2019; Geneva; United States
    Format: application/pdf
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  • 7
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    A New, Long-Lived, Jupiter Mesoscale Wave Observed at Visible Wavelengths (2018)
    In:  CASI
    Details
    Publikationsdatum: 2019-10-19
    Beschreibung: Small-scale waves were observed along the boundary between Jupiters North Equatorial Belt and North Tropical Zone, ~16.5 N planetographic latitude in Hubble Space Telescope data in 2012 and throughout 2015 to 2018, observable at all wavelengths from the UV to the near IR. At peak visibility, the waves have sufficient contrast (~10%) to be observed from ground-based telescopes. They have a typical wavelength of about 1.2 (1400 km), variable-length wave trains, and westward phase speeds of a few m/s or less. New analysis of Voyager 2 data shows similar wave trains over at least 300 hours. Some waves appear curved when over cyclones and anticyclones, but most are straight, but tilted, shifting in latitude as they pass vortices. Based on their wavelengths, phase speeds, and faint appearance at high-altitude sensitive passbands, the observed NEB waves are consistent with inertia-gravity waves at the 500-mbar pressure level, though formation altitude is not well constrained. Preliminary General Circulation Model simulations generate inertia-gravity waves from vortices interacting with the environment and can reproduce the observed wavelengths and orientations. Several mechanisms can generate these waves, and all may contribute: geostrophic adjustment of cyclones; cyclone/anticyclone interactions; wind interactions with obstructions or heat pulses from convection; or changing vertical wind shear. However, observations also show that the presence of vortices and/or regions of convection are not sufficient by themselves for wave formation, implying that a change in vertical structure may affect their stability, or that changes in haze properties may affect their visibility.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN59896 , Astronomical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 156; 2; 79
    Format: application/pdf
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  • 8
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    Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu (2019)
    In:  CASI
    Details
    Publikationsdatum: 2020-01-04
    Beschreibung: Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and SecurityRegolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: GSFC-E-DAA-TN76455 , Science (ISSN 0036-8075) (e-ISSN 1095-9203); 366; 6470; eaay3544
    Format: application/pdf
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  • 9
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    Time-dependent Hybrid Plasma Simulations of Lunar Electromagnetic Induction in the Solar Wind (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-12-21
    Beschreibung: No abstract available
    Schlagwort(e): Lunar and Planetary Science and Exploration
    Materialart: MSFC-E-DAA-TN76019 , AGU Fall Meeting; Dec 09, 2019 - Dec 13, 2019; San Fransico, CA; United States
    Format: application/pdf
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  • 10
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    eddy Users Manual (2019)
    In:  CASI
    Details
    Publikationsdatum: 2019-12-12
    Beschreibung: eddy is a collection of tools - nonlinear solvers, meshing, post-processing, visualization, optimization, etc. - for performing scale-resolving simulations of multi-physics applications. The framework is designed to enable advanced R&D on a variety of topics by leveraging a mature capability for scale resolving simulations, and simultaneously be an appropriate tool for application analysis and support. Currently, eddy is at a relatively low technical readiness level (TRL), and users and developers should maintain appropriate expectations. The technical details behind eddy are outlined in several publications which can be consulted for more information [110]. The solvers are built around an unstructured high-order capability, and heavily utilize the tensor product sum-factorization approach for efficiency. The unsteady formulation utilizes a fully implicit space-time approach with a matrix-free Newton- Krylov method. A primitive steady-state solver is available for testing purposes, but is not expected to converge for all but simple verification cases. The Navier-Stokes fluid solvers do not support either RANS or hybrid-RANS capability, only LES and wall-modeled LES approaches. All of the solvers within eddy support three modes of operation: a primal solve of the full nonlinear problem, and two linearization approaches of the primal solve - the ad joint and the tangent solution. Details on how to select and use these three modes are outlined in Sec. 3.
    Schlagwort(e): Computer Programming and Software
    Materialart: ARC-E-DAA-TN70615
    Format: application/pdf
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