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  • Other Sources  (61)
  • GEOPHYSICS  (52)
  • Aircraft Communications and Navigation  (9)
  • Chemical Engineering
  • 2005-2009  (1)
  • 1995-1999  (9)
  • 1970-1974  (51)
  • 1
    Publication Date: 2019-07-13
    Description: This paper discusses the process and results of the performance testing of the GPS receiver planned for use on the International Space Station (ISS) and the X-38 Crew Return Vehicle (CRV). The receiver is a Force-19 unit manufactured by Trimble Navigation and modified in software by the NASA Goddard Space Flight Center (GSFC) to perform navigation and attitude determination in space. The receiver is the primary source of navigation and attitude information for ISS and CRV. Engineers at GSFC have developed and tested the new receiver with a Global Simulation Systems Ltd (GSS) GPS Signal Generator (GPSSG). This paper documents the unique aspects of ground testing a GPS receiver that is designed for use in space. A discussion of the design of tests using the GPSSG, documentation, data capture, data analysis, and lessons learned will precede an overview of the performance of the new receiver. A description of the challenges that were overcome during this testing exercise will be presented. Results from testing show that the receiver will be within or near the specifications for ISS attitude and navigation performance. The process for verifying other requirements such as Time to First Fix, Time to First Attitude, selection/deselection of a specific GPS satellite vehicles (SV), minimum signal strength while still obtaining attitude and navigation, navigation and attitude output coverage, GPS week rollover, and Y2K requirements are also given in this paper.
    Keywords: Aircraft Communications and Navigation
    Type: GPS Conference; Sep 14, 1999 - Sep 17, 1999; Nashville, TN; United States
    Format: application/pdf
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  • 2
    Publication Date: 2011-08-16
    Description: Artificial auroral experiment by Aerobee rocketborne electron accelerator generated monoenergetic electron beam injection onto magnetospheric field
    Keywords: GEOPHYSICS
    Type: ; 367-414. (
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  • 3
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    In:  Other Sources
    Publication Date: 2019-06-27
    Description: There are no author-identified significant results in this report.
    Keywords: GEOPHYSICS
    Type: REPT-2266-7 , Kansas Environ. and Resource Study: A Great Plains Model; 7 p
    Format: text
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  • 4
    Publication Date: 2019-06-27
    Description: Two field-line tracing experiments were conducted on an L = 1.26 magnetic flux tube over Kauai, Hawaii. Barium vapor was created by the detonation of a highly explosive shaped charge aligned with the geomagnetic field at a 467-km altitude. Barium ions traveled along the field line to the conjugate ionosphere in a tube 3 to 5 km in diameter, producing a visible streak along the entire 6900-km path length. Electric fields perpendicular to the magnetic field caused the ions to drift away from the true conjugate during transit, but extrapolation from subsequent ion drift rates allowed the conjugate to be identified and compared with several field models. Differing ion drift rates and directions at the conjugate points indicated that the electric field is not transferred unattenuated along field lines.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 77; June 1
    Format: text
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  • 5
    Publication Date: 2019-06-27
    Description: Results of simultaneous observation of a fast wave event from the Ester Dome Observatory (EDO) near College, Alaska, the Poker Flat Rocket Launching Facility (PKR), and Fort Yukon, Alaska (FYU). The display occurred on Mar. 27, 1971, and the general morphology is described and discussed. It is suggested that fast auroral waves occur when a preceding substorm has enhanced the particle population in the region of the magnetosphere near L = 6 in the midnight sector; then transverse hydromagnetic waves, associated with the onset of further local substorm activity, become visible through their action on this enhanced particle population as they propagate inwards in the equatorial region.
    Keywords: GEOPHYSICS
    Type: Planetary and Space Science; 20; Mar. 197
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  • 6
    Publication Date: 2019-06-27
    Description: The problems involved in the resolution of the temporal/spatial ambiguity in sounding rocket observations are discussed with reference to an experiment involving a mother-daughter rocket combination, together with a flashing light beacon on the rocket and television cameras on the ground. The ambiguity was successfully removed, enabling a proper interpretation of the observations of precipitating low energy electrons to be made.
    Keywords: GEOPHYSICS
    Type: ESRO European Sounding-Rocket and Related Res. at High Latitudes; p 113-118
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  • 7
    Publication Date: 2019-06-27
    Description: Data from a rocket launched into the expansion phase of an auroral substorm have been compared with data from numerous ground stations and several space vehicles. It is shown that this magnetic and auroral substorm has most of the features of larger substorms; thus it is implied that the same plasma processes are involved in all substorms. Some evidence is presented to link the auroral breakup with the field lines conjugate to the inner edge of the plasma sheet. The implications of these two results for substorm morphology and the triggering mechanism of the substorm instability are discussed. It is concluded that spatial gradients in plasma temperature are a likely cause.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 79; Apr. 1
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  • 8
    Publication Date: 2019-06-27
    Description: The author has identified the following significant results. For two years ERTS-1 has been employed to investigate current circulation patterns in Delaware Bay under different tidal, flow, and wind conditions. Since sufficient numbers of current meters and boats are not available, air-droppable drogues and dye packs have been developed and tested. The drogues consist of a styrofoam float and a line to which is attached a stainless steel biplane. The length of the line determines at what depth currents will be monitored. The floats are color coded to distinguish their movement and mark the depth of the biplanes. Simultaneously floating and anchored dye packs of fluorescein dye have been deployed from aircraft. The movement of the dye and drogues is tracked by sequential aerial photography, using fixed markers on shore or on buoys as reference points to calibrate the scale and direction of drogue movement. The current data obtained by this technique is then used to annotate current circulation maps derived from ERTS-1 imagery.
    Keywords: GEOPHYSICS
    Type: E74-10747 , NASA-CR-139987
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  • 9
    Publication Date: 2019-06-27
    Description: Several local edge detection operators were applied to a set of ERTS pictures of the Monterey, Calif. area. Gradient operators performed consistently better than laplacian operators in detecting edges. It was also found that if a grayscale normalization operation, histogram flattening, was applied to the pictures first, the edge detector outputs were greatly enhanced. The use of interpolation for more accurate location of edges on a digital picture was also briefly investigated. Curve detection operators were applied to the edge detector outputs; this had the effect of enhancing the edges while suppressing noise.
    Keywords: GEOPHYSICS
    Type: NASA-CR-138963 , TR-312
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  • 10
    Publication Date: 2019-06-27
    Description: The vertical variations in atmospheric light attenuation under ambient conditions were identified, and a method through which aerial photographs of earth features might be corrected to yield quantitative information about the actual features was provided. A theoretical equation was developed based on the Bouguer-Lambert extinction law and basic photographic theory.
    Keywords: GEOPHYSICS
    Type: NASA-CR-139382
    Format: application/pdf
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