Global views of Venus from Magellan

Analysis of a global radar backscatter mosaic generated from cycle 1 and 2 Magellan data shows that the Venusian surface is, on average, only hundreds of millions of years old, dominated by volcanic plains, and that it exhibits a variety of tectonic features. Impact craters are well‐preserved and widely distributed. In this article, we consider resurfacing models that are consistent with these observations and interpretations. On August 10, 1990, the Magellan spacecraft, with its 12.6 cm wavelength radar system, was placed in a highly inclined elliptical orbit around Venus, with a periapsis located at ∼10° northern latitude. [Saunders and Pettengill, 1991]. Since September 15, 1990, the 3.7‐m diameter high gain antenna (HGA) has been used to acquire side‐looking synthetic aperture radar (SAR) backscatter images and passive radiometry data in HH (horizontally polarized transmit and receive) polarization [Pettengill et al., 1991]. A smaller, nadir‐pointing antenna (ALTA) that shares electronics with the high gain antenna has been used to obtain echoes from which elevation and surface scattering properties have been derived [Pettengill et al., 1991]. The orbital ground track shifts approximately 20 km eastward at the equator from orbit to orbit, returning to the same position in 243 days, the time it takes Venus to rotate once beneath the orbital plane. Each complete circuit is called a “mapping cycle.” Mapping cycle 1 ended on May 15, 1991. After completion of cycle 1, the spacecraft's orbit was changed to offset the ground track relative to cycle 1 to allow for interleaving of altimetry ground swaths.