The Pioneer Venus Orbiter, also known as Pioneer Venus 1 or Pioneer 12, was a mission to Venus conducted by NASA as part of the Pioneer Venus project. Launched in May 1978 atop an Atlas-Centaur rocket, the spacecraft was inserted into an elliptical orbit around Venus on December 4, 1978. It returned data from Venus until October 1992. The spacecraft conducted radar altimetry observations allowing the first global topographic map of the Venusian surface to be constructed. Manufactured by Hughes Aircraft Company, the Pioneer Venus Orbiter was based on the HS-507 bus. The spacecraft was a flat cylinder, 2.5 meters (8.2 ft) in diameter and 1.2 meters (3.9 ft) long.

Wikipedia: https://en.wikipedia.org/wiki/Pioneer_Venus_Orbiter. Related NASA reference: https://science.nasa.gov/mission/pioneer-venus-1/. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).