11 billion miles from Earth, "Grand Tour of the Solar System" comes to an end
In 1977, Jimmy Carter was sworn in as president, Elvis died, Virginia park ranger Roy Sullivan was hit by lightning a record seventh time, and two NASA space probes destined to turn planetary science on its head launched from Cape Canaveral. The identical spacecraft, Voyager 1 and Voyager 2, were launched in the summer and programmed to pass by Jupiter and Saturn on different paths. Voyager 2 went on to visit Uranus and Neptune, completing the "Grand Tour of the Solar System," perhaps the most exciting interplanetary mission ever flown. Now NASA has announced that Voyager 1 - about 11 billion miles from Earth - has now sailed to the edge of the solar system and is expected to punch its way into interstellar space in the coming months or years. Voyager 2 is not far behind, but on a different trajectory.
University of Colorado Boulder scientists, who designed and built identical instruments for Voyager 1 and Voyager 2, were as stunned as anyone when the spacecraft began sending back data to Earth.
The discoveries by Voyager started piling up: Twenty-three new planetary moons at Jupiter, Saturn, Uranus and Neptune; active volcanoes on Jupiter's moon, Io; Jupiter's ring system; organic smog shrouding Saturn's moon, Titan; the braided, intertwined structure of Saturn's rings; the solar system's fastest winds (on Neptune, about 1,200 miles per hour); and nitrogen geysers spewing from Neptune's moon, Triton.
Charlie Hord, a former planetary scientist at CU-Boulder's Laboratory for Atmospheric and Space Physics, remembers the salad days of the Voyager program, which was managed by NASA's Jet Propulsion Laboratory in Pasadena. Hord, the principal investigator for a time on the LASP instrument known as a photopolarimeter built for Voyager, still shakes his head in wonder as he recalls some of the discoveries.