The two best-known Pioneer spacecraft, Pioneer 10 and 11, left Earth in 1972 and 1973, respectively. They were designed to gather data about the distant gas giant planets Jupiter and Saturn. Each of the twin spacecraft had a nine-foot (three-meter) diameter radio antenna dish, which was used for communications between the spacecraft and receiving stations on Earth. Scientific instruments, cameras, a radioisotope thermoelectric generator (RTG), and a rocket motor were attached to the back of the dish.