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  • Data
  • Other Sources  (4)
  • Communications and Radar  (2)
  • Review article  (2)
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  • Data
  • Other Sources  (4)
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  • 1
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    Unknown
    IReservoir induced seismicity data management center developments at the University of Texas at Austin (1989)
    In:  Eos, Trans., Am. Geophys. Un., San Francisco, Pergamon, vol. 70, no. 20, pp. 602, pp. B05315, (ISSN: 1340-4202)
    Details
    Publication Date: 1989
    Keywords: Seismology ; Review article ; Seismic networks ; Data analysis / ~ processing
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Evidence for a plate tectonics debate (2001)
    In:  Earth Science Reviews, San Francisco, Pergamon, vol. 55, no. 3-4, pp. 235-336, pp. B05315, (ISSN: 1340-4202)
    Details
    Publication Date: 2001
    Keywords: Plate tectonics ; Review article ; rifting ; Iceland ; plumes ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; spreading ; MORB ; ConvolutionE ; Mineralogy
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Measured Changes in C-Band Radar Reflectivity of Clear Air Caused by Aircraft Wake Vortices (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Wake vortices from a C-130 airplane were observed at the NASA Wallops Flight Facility with a ground-based, monostatic C-band radar and an antenna-mounted boresight video camera. The airplane wake was viewed from a distance of approximately 1 km, and radar scanning was adjusted to cross a pair of marker smoke trails generated by the C-130. For each airplane pass, changes in radar reflectivity were calculated by subtracting the signal magnitudes during an initial clutter scan from the signal magnitudes during vortex-plus-clutter scans. The results showed both increases and decreases in reflectivity on and near the smoke trails in a characteristic sinusoidal pattern of heightened reflectivity in the center and lessened reflectivity at the sides. Reflectivity changes in either direction varied from -131 to -102 dBm(exp -1); the vortex-plus-clutter to noise ratio varied from 20 to 41 dB. The radar recordings lasted 2.5 min each; evidence of wake vortices was found for up to 2 min after the passage of the airplane. Ground and aircraft clutter were eliminated as possible sources of the disturbance by noting the occurrence of vortex signatures at different positions relative to the ground and the airplane. This work supports the feasibility of vortex detection by radar, and it is recommended that future radar vortex detection be done with Doppler systems.
    Keywords: Communications and Radar
    Type: NASA-TP-3671 , NAS 1.60:3671 , L-17618
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Estimating a Large Phased Array Antenna Radiation Pattern by Computer Electromagnetic Simulation (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The design of a conformal antenna for use on UAV's (Unmanned Aerial Vehicle) and other aircraft can be enhanced with computational electromagnetic modeling to determine the expected radiation patterns of the antenna when mounted on the aircraft. However, detailed simulation of the antenna structure and the aircraft together requires significant computational resources and time which may not be available. This paper details several methods for estimating the radiation pattern of a 50 by 50-element patch antenna. The Conformal Lightweight Antenna Structures for Aeronautical Communication Technologies (CLASACT) Program aims to build and test a 14.25 gigaherz (Ku-band) conformal antenna on a NASA-owned UAV. The antenna is intended for satellite communications and will enable communication between a ground station and a UAV when the separation distance is too great for line-of-sight communication. It is estimated that a 2 degree beamwidth will be necessary, requiring a 50 by 50 array of patch elements. The narrow beamwidth requirement, together with an element spacing of 0.6 lambda means that the array length will be 30 wavelengths, electrically very large. Three methods of varying complexity are described for estimating the total far-field radiation pattern. The results are shown for each method in the form of a normalized power pattern.
    Keywords: Communications and Radar
    Type: NASA/TM-2018-220094 , L-20970 , NF1676L-31484
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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