Pioneer Venus Orbiter

The Pioneer Venus Orbiter, also known as Pioneer Venus 1 and Pioneer 12, was a mission by NASA to orbit Venus and collect information. It was launched on May 20, 1978 by an Atlas Centuar rocket, and operated (sent data) until October 8, 1992. Pioneer Venus Orbiter fell into Venus’s atmosphere 2 weeks later on October 22. It arrived at Venus on December 4, 1978, and continued sending data for 14 years. The Pioneer Venus Orbiter is part of a space program called the Pioneer Program.
From its orbit of Venus, the Pioneer Venus Orbiter was able to watch Halley's Comet when it was hidden from Earth during February 1986. It found the loss of water from the comet's center on February 9.