Which Soviet orbiters first identified Venusian coronae with radar images in 1983?

The Soviet orbiters that first identified Venusian coronae in radar images were Venera 15 and Venera 16.

The two spacecraft entered polar orbits around Venus in October 1983 and used synthetic-aperture radar to examine the planet through its permanently clouded atmosphere. Their radar images covered the northern part of Venus at roughly 1-to-2-kilometer resolution, revealing geological structures that earlier observations could not resolve clearly.

Those images helped identify coronae as distinctive circular or oval features with concentric fractures, volcanic structures and complex tectonic patterns. Before the Venera 15 and 16 survey, some unusual surface features had been mistaken for impact craters or were too poorly resolved to classify confidently.

The spacecraft mapped only part of Venus, but their results transformed understanding of the planet’s surface geology. Later, NASA’s Magellan spacecraft produced much more extensive and detailed global radar maps. Magellan confirmed and expanded the picture of coronae, volcanoes, lava plains and tectonic belts first made visible in detail by the Soviet mission.