An estimate of sixth‐degree and sixth‐order harmonic coefficients of the global gravity field of Venus has been obtained by processing the long periodic variations of the mean orbital elements of the Pioneer Venus orbiter. Approximately 220 days of data have been included in this reduction, which provides almost complete longitudinal coverage. Our estimate of oblateness (C20) is −5.97±3.2 × 10−6. The amplitudes of other coefficients are similar to the predicted coefficients using Kaula's rule under equal stress assumption. Atmospheric density values as a function of altitude have been obtained to help model drag perturbation. A radial acceleration map at 100 km above the Venus surface has been generated, and correlation between gravity anomalies and major topographic features is observed. Spectral analysis of the harmonic model suggests that the interior density anomalies are similar to those on earth. The orientation angles of the principal axes of the moments of inertia have been computed, and deviation of the maximum moment of inertia axis from the spin axis is observed to be small (<5°). The minimum moment of inertia axis passes through the Aphrodite and Beta regions.
A point mass representation of a tion, 1976] shows consistency for each of the quasi-global gravity field of the moon is devel-second-and third-degree harmonic coefficients. oped by processing Apollo 15 and 16 subsatellite However, higher-degree terms show little consisand Lunar Orbiter 5 Doppler tracking data. The tency. High-degree harmonic gravity fields determodel is generated by reducing the long periodic mined by Lorell [1970], Liu and Laing. [1971], and variations in the mean orbit element rates. The Michael and Blackshear [1972] show some correlacoefficients show reasonable presented in the accompanying paper by Ferrari agreement with other known fields. and Ananda [1977]. A model with 117 point masses has been estimated from the long periodic variar --
Recent reductions of Apollo subsatellite and Lunar Orbiter 5 data'have determined the first plausible models for the farside lunar gravity field. This paper presents a selenodesy method which estimates gravity by fitting to the long-term variations of the Kepler element rates. Raw Doppler tracking data taken over short arcs are reduced to estimate a best set of mean orbital elements for each orbit. A succession of Such fits is performed to generate a history of mean elements. The element rates are determined from patched cubic spline fits to the elements.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.