A HIGH-RESOLUTION GRAVITY MODEL FOR VENUS - GVM-1

A spherical harmonic model of the gravitational field of Venus complet e to degree and order 50 has been developed using the S-band Doppler t racking data of the Pioneer Venus Orbiter (PVO) collected between 1979 and 1982. The short wavelengths of this model could only be resolved near the PVO periapse location (approximately 14-degrees-N latitude), therefore a priori constraints were applied to the model to bias poorl y observed coefficients towards zero. The resulting model has a half-w avelength resolution of 400 km near the PVO periapse location, but the resolution degrades to greater than 1000 km near the poles. This grav ity model correlates well with a degree 50 spherical harmonic expansio n of the Venus topography derived from a combination of Magellan and P VO data. New tracking data from Magellan's gravity mission should prov ide some improvement to this model, although a complete model of the V enusian gravity field will depend on tracking of Magellan after the ci rcularization of it's orbit using aerobraking.