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  • Other Sources  (9)
  • GEOPHYSICS  (8)
  • SPACE VEHICLES  (1)
  • perturbation theory
  • 1980-1984  (3)
  • 1975-1979  (1)
  • 1970-1974  (5)
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  • Other Sources  (9)
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  • 1
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    Minimal upper mantle temperature variations consistent with observed heat flow and plate velocities (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Heat-flow and plate-velocity measurements are used to model upper-mantle temperature variations; the results are intended to form the basis for a gravity-field-variation model and are also applicable to the interpretation of petrological and seismological data. A 5-deg grid is used, a depth of 280 km is chosen as the fully convecting level, and it is assumed that 85 percent of the global heat production (4.0 x 10 to the 13th W) comes from below this level. The velocity field is calculated by integrating the momentum equations down to 280 km (assuming laterally homogeneous viscosity and density) and then used to determine the temperature fields. The results are presented in graphs, tables, and maps. The largest lateral temperature differences are about 1500 C and occur in the top 20 km, where the largest (about 200 C/Myr) nonlinear terms of the energy equation are also found. Below 50 km, heat transfer becomes more convective than conductive, and the most significant temperature variation appears in the form of negative 'tongues' as cold as -825 C at about 100 km. Temperature variations of at least + or - 180 C are calculated at the fully convecting level.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 10323-10
    Format: text
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  • 2
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    Material properties for mantle convection consistent with observed surface fields (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An attempt is made to derive constraints on mantle convection from observed surface fields: plate velocities, gravity, topography and heat flow. The spherical harmonic spectra of the fields are expressed in terms of a spectral magnitude and slope, and requirements for the minimal representation of the equations for mantle convection are discussed. The effects of the boundary layer represented by the surface fields on convection at the mantle surface and at deeper levels are then examined, and a mean value of the effective mantle viscosity of approximately 10 to the 23rd g/cm per sec is obtained, together with values of 10 to the 8th and 10 to the 7th for the Rayleigh numbers of whole mantle and upper mantle convection, respectively. Consideration is then given to the compositional, thermal and rheological aspects of mantle convection, and it is pointed out that constraints on the depth and other properties of convection will require more detailed modeling using the relationships between the harmonic coefficients of the surface fields.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 85; Dec. 10
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  • 3
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    Inference of variations in the gravity field from satellite-to-satellite range rate (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An analytic scheme for inferring variations of the gravity field from satellite-to-satellite range rate (low-low) is developed. As a test, it is applied to a pair of satellites in polar orbit, at altitude 160 km and spacing 100 km, with 72 data points per revolution. An assumed gravity field of tesseral spherical harmonics up to the eighth degree is completely recovered in three iterations over 64 revolutions. It is apparent that data points at regular intervals enable the use of data analysis techniques that avoid massive matrix inversions.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Oct. 10
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  • 4
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    Absolute plate motions by boundary velocity minimizations (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The main interaction of the earth's interior with the lithosphere is as a material source and sink. An absolute reference frame defined by minimizing the translational motion of tectonic plate boundaries differs by 0.6 cm/year from a frame defined by hot spot traces and by 0.4 cm/year from the frame defined by the most plausible model of drag forces on the plates. The rms absolute translational velocities are about 2 cm/year for ocean-ocean plate boundaries and 1.5 cm/year for ocean-continent plate boundaries. The close agreement between the source and sink and the drag-dependent definitions suggests that the lithosphere, as a stress guide, to some extent controls the locations of its sources and sinks.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 80; Jan. 10
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  • 5
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    Potentialities of lunar laser ranging for measuring tectonic motions. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The lunar laser-ranging system at McDonald Observatory, Texas, is currently attaining accuracies of plus or minus 15 cm, and plus or minus 3 cm appears feasible. Numerical error analyses containing 97 parameters (35 of them for error sources) indicate that the plus or minus 3 cm system would measure station motions to plus or minus 1 cm/year accuracy within a year for east-west motions and within about 3 years for north-south. Furthermore, the correlations of station motions with other parameters are low, so that it is unlikely that the estimate is too optimistic because of modeling inadequacies of the error analysis.
    Keywords: GEOPHYSICS
    Format: text
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  • 6
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    Error analysis for station position from tracking of the Lageos satellite (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The earth physics satellite systems error analysis program was applied to the problem of predicting the relative accuracy of station position determinations under varying orbital and observing geometries. The reference case consists of nine ground stations extending over 1500 km which lasers ranged to a LAGEOS satellite, with simultaneous Doppler tracking from a geosynchronous satellite for 16 days. Eleven variations from the reference case were tested. The results showed little sensitivity to whether the LAGEOS altitude is 3700 or 5690 km. More significant were the high inclination, and that LAGEOS was tracked by a geosynchronous satellite.
    Keywords: GEOPHYSICS
    Type: NASA-CR-140118
    Format: application/pdf
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  • 7
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    Tidal theory and orbital perturbations (1971)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Linking ocean tides to satellite orbits
    Keywords: GEOPHYSICS
    Type: NASA-CR-121641
    Format: application/pdf
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  • 8
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    Error analysis of earth physics satellite systems (1972)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Error analysis of distant-satellite-to-close-satellite range-rate, satellite-to-sea altimetry, and ground station to satellite range are made by simulations in which observational variances are assumed, observation equations are formed, and normal equations incremented. The final normal equation matrix is inverted to obtain standard deviations and correlation coefficients. The natural parameters solved for are the broad variations of the gravity field, represented by harmonic coefficients; local variations of gravity, represented by point masses; and the departure of the sea level from the geoid, represented by area means. A standard case of a low (263 km) polar close satellite, three equatorial geosynchronous satellites, and eight ground tracking stations is set up.
    Keywords: SPACE VEHICLES
    Type: NASA-CR-130357
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  • 9
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    Application of space and astronomic techniques to solid earth and ocean physics (1970)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Space and astronomic methods applied to solid earth and ocean physics
    Keywords: GEOPHYSICS
    Type: ADVANCES IN DYNAMIC GRAVIMETRY, SYMPOSIUM ON DYNAMIC GRAVIMETRY; Mar 16, 1970 - Mar 17, 1970; FORT WORTH, TX
    Format: text
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