Voyagers voyage to the edge of the solar system

NPR : Some 35 years ago, Voyagers I and II left Earth on one of the most ambitious journeys in human history, a tour of the solar system with visits to Jupiter, Saturn, Uranus, and Neptune. The spacecraft were to use gravitational assist from the gravity wells of the planets they visited in order to slingshot toward the next target. Both spacecraft are still going, and Voyager I is about to pass the heliopause, the boundary between the absolute edge of our solar system and interstellar space. No scientist expected that the spacecraft would still be working at this point or that mission scientists would be able to upgrade them throughout the mission. The next time a similar trip could be planned is 150 years from now. Voyagers I and II are expected to keep working for another 10-15 years.