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  • LUNAR AND PLANETARY EXPLORATION  (4)
  • 1980-1984  (4)
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  • 1
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    Unknown
    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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  • 2
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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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  • 3
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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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  • 4
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    Structure and circulation of the Venus atmosphere (1980)
    In:  Other Sources
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    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
    Format: text
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