Several probes have flown as far as Jupiter. In 1973, the Pioneer 10 probe flew by the giant planet taking close-up photographs. The Voyager 1 and 2 probes, launched in 1977, flew by the four gas planets — Jupiter, Saturn, Uranus and Neptune — taking pictures and measurements. The primary Voyager missions were completed in 1989, but both craft are now continuing into the depths of the outer Solar System at a speed of over 56,300km/h (35,000mph). Even at this speed it could take the probes over 30,000 years to reach the outer edges of the Solar System!
The twin spacecraft Voyager 1 and Voyager 2 were launched by NASA in separate months in the summer of 1977 from Cape Canaveral, Florida. As originally designed, the Voyagers were to conduct close-up studies of Jupiter and Saturn, Saturn’s rings, and the larger moons of the two planets.
To accomplish their two-planet mission, the spacecraft were built to last five years. But as the mission went on, and with the successful achievement of all its objectives, the additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible — and irresistible to mission scientists and engineers at the Voyagers’ home at the Jet Propulsion Laboratory in Pasadena, California.
As the spacecraft flew across the solar system, remote-control reprogramming was used to endow the Voyagers with greater capabilities than they possessed when they left the Earth. Their two-planet mission became four. Their five-year lifetimes stretched to 12 and more.
Eventually, between them, Voyager 1 and 2 would explore all the giant outer planets of our solar system, 48 of their moons, and the unique systems of rings and magnetic fields those planets possess.
Had the Voyager mission ended after the Jupiter and Saturn flybys alone, it still would have provided the material to rewrite astronomy textbooks. But having doubled their already ambitious itineraries, the Voyagers returned to Earth information over the year that has revolutionized the science of planetary astronomy, helping to resolve key questions while raising intriguing new ones about the origin and evolution of the planets in our solar system.
