On August 20, 1977, Voyager 2 was launched into space.
The two Voyagers were types of unmanned spacecraft called space probes.
Two weeks later, Voyager 1 set off.
Their mission was to travel to the more distant planets of the solar system and send information about them back to earth.
No spacecraft had ever traveled so far into space before.
Voyagers 1 and 2 each carried 11 instruments.
These included remote-controlled computers, television cameras, ray detectors, infrared and ultraviolet sensors, and a magnetometer.
These instruments recorded and sent back information about our solar system.
Technology has developed quickly since the Voyager probes were launched. That equipment is now out of date. A modern, desktop computer is more powerful than the Voyager computers. Scientists have updated the probes' computer programs and made repairs from earth by remote control.
In 1980, three years after its launch, Voyager 1 reached Titan, Saturn's largest moon.
The probe sent back information to earth. It found chemicals like those on earth. But Titan is too cold for these chemicals to develop into living things as they have done on earth.
The journey of Voyager 21. On August 20, 1977, Voyager 2 was launched from earth at a speed of just over 24,800 miles (40,000 kilometers) per hour. The idea was to use the gravity, or pull, of each planet it passed to catapult the space probe faster and faster through space, from one planet to the next.
2. On July 9 1979, Voyager 2 came closest to Jupiter and discovered it has three more moons. The planet’s gravitational pull increased the speed of Voyager 2 to around 30.700 miles (48.000 kilometers) per hour.
3. It was August 25, 1981, and Voyager 2 passed Saturn at a speed of 33,700 miles (54,400 kilometers) per hour. Then we learned that Saturn has nine more moons that it was known to have.
4. At Uranus, on January 24, 1986, Voyager 2 discovered 10 new moons. Its speed was now 36,700 miles (59,200 kilometers) per hour.
5. Mission completed! On August 25, 1989, Voyager 2 passed within 3,000 miles (4,800 kilometers) of Neptune's cloud top.
We learned that this planet is a hostile world.
No living thing could survive here.
Twelve years after it left Earth, Voyager 2 reached Neptune. It had traveled nearly 4.4 billion miles (7.1 billion kilometers) and arrived four minutes early!
Voyager 2 carries its own message—a record of voices and other sounds from earth— just in case there is life beyond our solar system.
Voyager 2 is expected to enter interstellar space within a few years of 2016. It is not headed toward any particular star, although in roughly 40,000 years it should pass 1.7 light-years (9.7 trillion miles) from the star Ross 248.
Voyager 2 is expected to keep transmitting weak radio messages until at least 2025, over 48 years after it was launched.