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  • 1
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    Seismic P Wave Velocity Model From 3-D Surface and Borehole Seismic Data at the Alpine Fault DFDP-2 Drill Site (Whataroa, New Zealand) (2021)
    Details
    Publication Date: 2021-09-24
    Description: The New Zealand Alpine Fault is a major plate boundary that is expected to be close to rupture, allowing a unique study of fault properties prior to a future earthquake. Here we present 3-D seismic data from the DFDP-2 drill site in Whataroa to constrain valley structures that were obscured in previous 2-D seismic data. The new data consist of a 3-D extended vertical seismic profiling (VSP) survey using three-component and fiber optic receivers in the DFDP-2B borehole and a variety of receivers deployed at the surface. The data set enables us to derive a detailed 3-D P wave velocity model by first-arrival traveltime tomography. We identify a 100–460 m thick sediment layer (mean velocity 2,200 ± 400 m/s) above the basement (mean velocity 4,200 ± 500 m/s). Particularly on the western valley side, a region of high velocities rises steeply to the surface and mimics the topography. We interpret this to be the infilled flank of the glacial valley that has been eroded into the basement. In general, the 3-D structures revealed by the velocity model on the hanging wall of the Alpine Fault correlate well with the surface topography and borehole findings. As a reliable velocity model is not only valuable in itself but also crucial for static corrections and migration algorithms, the Whataroa Valley P wave velocity model we have derived will be of great importance for ongoing seismic imaging. Our results highlight the importance of 3-D seismic data for investigating glacial valley structures in general and the Alpine Fault and adjacent structures in particular.
    Keywords: 622.15 ; vertical seismic profiling ; P wave velocity tomography ; distributed acoustic sensing ; Deep Fault Drilling Project ; subglacial valley
    Language: English
    Type: map
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    CITATION GEO-LEO
  • 2
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    Active vehicle charging measurements in sounding rocket and space shuttle orbiter environments at Low Earth Orbit (LEO) altitude (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It was concluded that for electron beam emission up to 100mA, vehicle charging is not a significant problem with the Space Shuttle Orbiter. Similarly, sounding rocket payloads have no serious charging problems up to this level of beam current, provided that the maximum amount of the rocket skin is available to collect ionospheric electrons from the LEO altitude range. However, sounding rockets are marginal in their collecting area capability and other effects may occur to balance the beam current when operated at lower altitudes during the night.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AGARD, The Aerospace Environment at High Altitudes and its Implications for Spacecraft Charging and Communications; 16 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    A numerical model of electrodynamics of plasma within the contaminant gas cloud of the Space Shuttle Orbiter at low earth orbit (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A two-dimensional cloud was used to study the plasma dynamics within the outgas cloud associated with the Orbiter. It is shown that the polarization field is not symmetric about the direction of motion of the outgas cloud. It rotates in a way that can be predicted in simple cases by the ratio of the Hall and Pederson currents within the outgas cloud. The polarization field magnitude produced in the model was not large.
    Keywords: PLASMA PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9049-906
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Reactive collision terms for fluid transport theory (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: A modified Bhatnagar-Gross-Krook (BGK) collision method is used for the derivation of reactive collision terms to allow for complete higher-moment approximations in fluid transport theory. The general reactive collision terms for the 8-, 10- and 13-moment approximation for binary reactions are derived. Then, reactive collision terms for specific chemistry are derived with the assumptions: (1) all reactants and products have 13-moment distribution functions; (2) simple, classical assumptions provide sufficient models for reaction dynamics; and (3) the reaction rate is energy-independent. The derived specific formulas reflect two extremes in reactive collision dynamics: direct and indirect reaction mechanisms. Finally, considerations for correct use of the reactive collision terms are discussed in the context of space plasma environments.
    Keywords: PLASMA PHYSICS
    Type: Planetary and Space Science (ISSN 0032-0633); 40; 47-62
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Plasma parameters in the near wake of the Space Shuttle (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Results are presented from a Spherical Retarding Potential Analyzer and a spherical Langmuir Probe which were flown on the Spacelab-2 mission of the Space Shuttle Orbiter in August 1985. The probes were mounted in such a position that for certain Orbiter orientations, the wake edge formed by the starboard payload bay sill swept across the probes at a roll rate of once per orbit about an inertially stabilized pointing direction. Profiles of O(+) number density and electron number density across the wake edge showed that the charge particle number densities declined into the wake at a faster rate than that predicted by theoretical models. At angles of more than 10 deg into the wake from its geometric edge, two electron populations are found, with different mean random energies and electrical potentials. One of these populations is suggested to be the result of selective filtering of the high energy tails of the ambient ionospheric population, the other, a result of photoemission from the payload bay surfaces.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Geophysical Research Letters (ISSN 0094-8276); 14; 359-362
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.
    Keywords: Mathematical and Computer Sciences (General)
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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