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  • 1980-1984  (10)
  • 1
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    Polar motion and UT1: Comparison of VLBI, lunar laser, satellite laser, satellite Doppler, and conventional astrometric determinations (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Very long baseline interferometry observations made with a 3900 km baseline interferometer (Haystack Observatory in Massachusetts to Owens Valley Observation in California) were used to estimate changes in the X-component of the position of the Earth's pole and in UT1. These estimates are compared with corresponding ones from lunar laser ranging, satellite laser ranging, satellite Doppler, and stellar observations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Radio Interferometry; p 33-44
    Format: application/pdf
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  • 2
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    Accuracy of relative positioning by interferometry with GPS Double-blind test results (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: MITES (Miniature Interferometer Terminals for Earth Surveying) observations conducted on December 17 and 29, 1980, are analyzed. It is noted that the time span of the observations used on each day was 78 minutes, during which five satellites were always above 20 deg elevation. The observations are analyzed to determine the intersite position vectors by means of the algorithm described by Couselman and Gourevitch (1981). The average of the MITES results from the two days is presented. The rms differences between the two determinations of the components of the three vectors, which were about 65, 92, and 124 m long, were 8 mm for the north, 3 mm for the east, and 6 mm for the vertical. It is concluded that, at least for short distances, relative positioning by interferometry with GPS can be done reliably with subcentimeter accuracy.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Format: text
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  • 3
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    Geodesy by radio interferometry - Intercontinental distance determinations with subdecimeter precision (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analysis of very-long-baseline interferometer (VLBI) observations yielded estimates of the distances between three radio telescopes in the United States and one in Sweden, with formal standard errors of a few centimeters: Westford, Massachusetts-Onsala, Sweden: 5,599,714.66 + or - 0.03 m; Green Bank, West Virginia-Onsala, Sweden: 6,319,317.75 + or - 0.03 m; and Owens Valley, California-Onsala, Sweden: 7,914,131.19 + or - 0.04 m, where the earth-fixed reference points are defined in each case with respect to the axes of the telescopes. The actual standard errors are difficult to estimate reliably but are probably not greater than twice the formal errors.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; Mar. 10
    Format: text
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  • 4
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    Numerical model of the moon's rotation (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The differential equations for the Euler angles that define the moon's orientation with respect to an inertial coordinate frame have been integrated numerically. This numerical model of the moon's rotation, when used in conjunction with current lunar-orbit and earth-rotation models, fits lunar laser ranging observations over a five-year period within 28 cm (rms). The present model is also compared with the numerical model of Williams (1975) and Eckhardt's (1981) semianalytical model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Moon and the Planets; 24; May 1981
    Format: text
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  • 5
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    Tidal dissipation in the moon (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Euler's equations of motion, modified to include elasticity and solid friction, were used to study the rotation of the moon. Two heuristic models for the anelasticity were considered: Q independent of frequency and Q inversely proportional to the frequency and Q inversely proportional to the frequency of the strain oscillation. Parameters in each model were estimated by weighted least squares from 9 years of lunar laser range observations. The root mean square of the postfit range residuals was 19 cm in each case. For a strain period of 1 month, the estimates of Q obtained with the two models were similar and surprisingly low: 23 + or - 6. The range of uncertaintly, + or - 6, represents our estimate of the true standard deviation of the estimate of Q, as affected by systematic errors; it is 3 times larger than the formal, statistical, standard error.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Aug. 10
    Format: text
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  • 6
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    Zonal and meridional circulation of the lower atmosphere of Venus determined by radio interferometry (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The results of the Pioneer Venus differential long-baseline interferometry experiment are presented. The velocity component of the Pioneer probes as they fell to the surface of Venus was calculated from the Doppler shift of the received signal, and the other two orthogonal components were determined by long-baseline interferometry. The ambient wind velocity was about 1 m/s or less near the surface of the planet and about 100 m/s at an altitude of about 65 km at all four probe locations. Strata of high wind shear were found at altitudes of 15, 45, and 60 km. The wind velocity was always directed within a few degrees of due west except at a few km above the surface. The dominant motion of the lower atmosphere seems to be a retrograde zonal rotation, and eddies appear to account for most of the instantaneous meridional velocity. The data suggest that, within the clouds, a thermally driven mean meridional circulation is superimposed upon the much more rapid zonal rotation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
    Format: text
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  • 7
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    Analysis of lunar laser ranging data for Earth dynamics applications (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of elasticity and of tidal friction within the Moon were incorporated into the numerical model of the Moon's rotation which was used in an effort to determine the axial rotation of the Earth, as measured by Universal Time. Some 2,651 normal points representing ranges measured to Lunokhod 2, and to the Apollo 11, 14, and 15 retroflectors were analyzed. Smoothed estimates derived from the lunar rangefinding were compared with smoothed values published by the International Bureau of Time, in the 1968 and 1969 systems. The derived values at the observation sight were connected to corresponding values at the Conventional International Origin, using the BIH data for polar motion. Differences are discussed.
    Keywords: LASERS AND MASERS
    Type: NASA-CR-163145
    Format: application/pdf
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  • 8
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    Structure and circulation of the Venus atmosphere (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Pioneer Venus data relevant to the dynamics and thermodynamics of the atmosphere is summarized and interpreted. On the day side there is a thermosphere in which temperatures increase with height to an exospheric temperature of about 300 K. On the night side there is a cryosphere in which temperatures decrease with height to an exospheric temperature of about 100 K. The atmosphere is stratified stably from the highest altitudes down to about 28 km except for a layer in the clouds between about 50 and 55 km which is nearly adiabatic. Horizontal thermal contrasts are approximately 1 to 2% in the deep atmosphere and 100% in the upper atmosphere. The temperatures generally decrease with latitude at and below the clouds on constant pressure surfaces. Above the clouds there is a reversed zonally averaged latitudinal temperature gradient. The dominant circulation of the atmosphere above the lowest one or two scale heights is a zonal retrograde motion with 100 m/s winds at 60 km altitude. There is also a superrotation at altitudes of 150 km and above.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAGW-47 , Journal of Geophysical Research; 85; Dec. 30
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  • 9
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    Centimeter-level relative positioning with GPS (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Although the Global Positioning System (GPS) was designed primarily for real-time navigation and positioning applications at the decameter level of accuracy, the GPS has been used to determine all three relative position coordinates of fixed points with centimeter-level accuracy, when the distance between the points has been of the order of 10 km. For intersite distances less than 1 km the uncertainty is about 3 mm, and for distances greater than 10 km the uncertainty in each coordinate is about 1-2 ppm of the distance. These results have been obtained with commercially available production equipment (Macrometer model V-1000 interferometric surveyors) operated by regular surveying personnel under real field conditions, not just by university scientists under ideal laboratory conditions. Techniques that promise to reduce the uncertainty to 0.1 ppm for distances greater than 10 km are being developed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: AD-A133842 , AFGL-TR-83-0245 , American Society of Civil Engineers, Surveying Engineering Division, Journal (ISSN 0733-9453); 109; 81-89
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  • 10
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    Applications to Earth physics: Very-long-baseline interferometry and data analysis (1982)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A range of very long baseline interferometry experiments applied to Earth physics are covered.
    Keywords: GEOPHYSICS
    Type: NASA-CR-168743 , NAS 1.26:168743
    Format: application/pdf
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