For over two decades, beginning in 1977, he concentrated most heavily on Venus, this time utilizing radars aboard spacecraft, first the Pioneer Venus orbiter and later, Magellan. For many years, he pursued the idea for using a radar altimeter to map Venus and contributed key technical ideas. The results, in part, were detailed reflectivity and topographic maps of virtually the entire planet of Venus, providing geologists and geophysicists with lifetimes of work to understand the development of Venus' crust and the history of its interior. Many planetary scientists feel he is one of the individuals most responsible for our present knowledge of Venus (aside from its atmosphere).