In the late summer of 1977, NASA launched the twin Voyager spacecraft. These remote ambassadors still beam messages back to Earth 40 years later, with data from their deep space travels. Voyager 1 is about 13 billion miles from Earth in interstellar space, and Voyager 2 is not far behind.
Voyager 1 is in Interstellar space and Voyager 2 is currently in the Heliosheath — the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas. Both Voyagers use real spacecraft trajectories and are updated every five minutes. Distance and velocities are updated in real-time.
Voyager 1 is expected to keep its current suite of science instruments on through 2021 and Voyager 2 through 2020.
The radioisotope thermoelectric generator on each spacecraft puts out 4 watts less each year. Because of this diminishing electrical power, the Voyager team has had to prioritize which instruments to keep on and which to turn off. Heaters and other spacecraft systems have also been turned off one by one as part of power management.
Voyager is probably the most scientifically productive mission ever. It was only the second mission to visit Jupiter and Saturn and the only one to visit Uranus and Neptune. Voyager 1 and 2 obtained the first detailed profiles of the atmospheres of Saturn, Uranus and Neptune and improved the understanding of the characteristics of the atmosphere of Jupiter. The Voyager spacecraft revealed the enormous amount of detail in the rings of Saturn, discovered the rings of Jupiter and provided the first detailed images of the rings of Uranus and Neptune. Discovery of active volcanism on Io, a satellite of Jupiter, was probably the greatest surprise. It was the first time active volcanoes had been seen on another body in the solar system. (Source: NASA)