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  • 1
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    An improved model for the Earth's gravity field (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An improved model for the Earth's gravity field, TEG-1, was determined using data sets from fourteen satellites, spanning the inclination ranges from 15 to 115 deg, and global surface gravity anomaly data. The satellite measurements include laser ranging data, Doppler range-rate data, and satellite-to-ocean radar altimeter data measurements, which include the direct height measurement and the differenced measurements at ground track crossings (crossover measurements). Also determined was another gravity field model, TEG-1S, which included all the data sets in TEG-1 with the exception of direct altimeter data. The effort has included an intense scrutiny of the gravity field solution methodology. The estimated parameters included geopotential coefficients complete to degree and order 50 with selected higher order coefficients, ocean and solid Earth tide parameters, Doppler tracking station coordinates and the quasi-stationary sea surface topography. Extensive error analysis and calibration of the formal covariance matrix indicate that the gravity field model is a significant improvement over previous models and can be used for general applications in geodesy.
    Keywords: GEOPHYSICS
    Type: Ohio State Univ., Progress in the Determination of the Earth's Gravity Field; p 8-11
    Format: application/pdf
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  • 2
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    Polar motion results from GEOS 3 laser ranging (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The observability of polar motion from laser range data has been investigated, and the contributions from the dynamical and kinematical effects have been evaluated. Using 2-day arcs with GEOS 3 laser data, simultaneous solutions for pole position components and orbit elements have been obtained for a 2-week interval spanning August 27 to September 10, 1975, using three NASA Goddard Space Flight Center stations located at Washington, D.C., Bermuda, and Grand Turk. The results for the y-component of pole position from this limited data set differenced with the BIH linearly interpolated values yield a mean of 39 cm and a standard deviation of 1.07 m. Consideration of the variance associated with each estimate yields a mean of 20 cm and a standard deviation of 81 cm. The results for the x-component of pole position indicate that the mean value is in fair agreement with the BIH; however, the x-coordinate determination is weaker than the y-coordinate determination due to the distribution of laser sites (all three are between 77 deg W and 65 deg W) which results in greater sensitivity to the data distribution. In addition, the sensitivity of these results to various model parameters is discussed.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 84; July 30
    Format: text
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  • 3
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    Progress in the determination of the gravitational coefficient of the earth (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: In most of the recent determinations of the geocentric gravitational coefficient (GM) of the earth, the laser ranging data to the Lageos satellite have had the greatest influence on the solution. These data, however, have generally been processed with a small but significant error in one of the range corrections. In a new determination of GM using the corrected center-of-mass offset, a value of 398600.4415 cu km/sq sec (including the mass of the atmosphere) has been obtained, with an estimated uncertainty (1 sigma of 0.0008 cu km/sq sec.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 529-531
    Format: text
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  • 4
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    Determination of the gravitational coefficent of the earth from near-earth satellites (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Laser range, Doppler, and altimeter data collected from 14 near-earth satellites have been combined to determine the value of the geocentric gravitational coefficent (GM) of the earth. A long-arc solution using three years of laser range data to Lageos was used in a separate determination in which the effects of general relativity were invetigated. The value of GM (including the mass of the atmosphere) was determined to be 398600.4405 cu km/sq sec when all corrections for general relativity are taken into account. The uncertainty (1-sigma) in the value of GM is estimated to be 0.001 cu km/sq sec.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 271-274
    Format: text
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  • 5
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    Absolute positioning using DORIS tracking of the SPOT-2 satellite (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The ability of the French DORIS system operating on the SPOT-2 satellite to provide absolute site positioning at the 20-30-centimeter level using 80 d of data is demonstrated. The accuracy of the vertical component is comparable to that of the horizontal components, indicating that residual troposphere error is not a limiting factor. The translation parameters indicate that the DORIS network realizes a geocentric frame to about 50 nm in each component. The considerable amount of data provided by the nearly global, all-weather DORIS network allowed this complex parameterization required to reduce the unmodeled forces acting on the low-earth satellite. Site velocities with accuracies better than 10 mm/yr should certainly be possible using the multiyear span of the SPOT series and Topex/Poseidon missions.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 20; p. 2039-2042.
    Format: text
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  • 6
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    Polar motion from laser range measurements of GEOS-3 (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Using two-day arcs of GEOS-3 laser data, simultaneous solutions for pole position components, x sub p and y sub p, and orbit elements have been obtained for the period spanning 3 February to 6 March 1976 using three NASA Goddard Space Flight Center laser stations located near Washington, D.C. (STALAS) and on the islands of Bermuda and Grand Turk. The results are in general agreement with the BIH results. However, because of the locations of the laser sites, the x sub p solution is weaker than the y sub p solution. The x sub p and y sub p estimates were smoothed with a straight line by weighted least squares using the variance associated with the pole estimates as weights in order to reflect the effect of widely different data distributions. The smoothed y sub p differs by one meter with respect to the BIH smoothed values and the smoothed x sub p differs by about two meters. Spectral analysis of the results has identified frequencies associated with the orbital motion indicating the need for further improvements in the model of the physical system.
    Keywords: GEOPHYSICS
    Type: Time and the earth''s rotation; Eighty-second Symposium; May 08, 1978 - May 12, 1978; San Fernando; Spain
    Format: text
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