High‐resolution gravity model of Venus

Abstract

The anomalous gravity field of Venus shows high correlation with surface features revealed by radar. We extract gravity models from the Doppler tracking data from the Pioneer Venus Orbiter (PVO) by means of a two‐step process. In the first step, we solve the nonlinear spacecraft state estimation problem using a Kalman filter‐smoother. The Kalman filter has been evaluated through simulations. This evaluation and some unusual features of the filter are discussed. In the second step, we perform a geophysical inversion using a linear Bayesian estimator. To allow an unbiased comparison between gravity and topography, we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps. The maps presented cover 2/3 of the surface of Venus and display the strong topography‐gravity correlation previously reported. The topography‐gravity scatter plots show two distinct trends.

A high resolution gravity model for Venus: GVM‐1

“…Representative of these efforts are models by Ananda et al [1980] We have developed a spherical harmonic expansion of the Venus gravity field complete to degree 50 using the PVO Sband Doppler tracking data by applying a priori constraints to the gravity solution in order to bias poorly observed coefficients towards zero while still resolving the short wavelength gravity field where the PVO data allow it. This is the first spherical harmonic gravity model of this resolution to be computed for Venus, although PVO tracking data has been used to determine high resolution Venus gravity anomalies on a regional basis [Reasenberg et al, 1981;Sjogren et al, 1980;1983]; and more recently on a global scale [Reasenberg and Goldberg, 1992]. This model exploits the varying spatial resolution of the PVO data set while still using a set of global spherical harmonic functions.…”