Endeavour may be grounded, but Voyager just keeps on going.
NASA experts noted that more than 30 years after the twin Voyager probes set sail for space, they are now poised on the edge of the solar system -- and set to continue their voyage into interstellar space.
And they're both working fine.
“It’s uncanny,” says Ed Stone of the California Institute of Technology in Pasadena, Voyager Project Scientist since 1972. “Voyager 1 and 2 have a knack for making discoveries,” he added.
Voyager 1 has visited Jupiter and Saturn, while Voyager 2 has flown past Jupiter, Saturn, Uranus and Neptune. Stone’s partial list of discoveries from those missions include the discovery of volcanoes on Jupiter’s moon Io; evidence for an ocean beneath the icy surface of Europa; hints of methane rain on Saturn’s moon Titan; icy geysers on Neptune’s moon Triton; and more.
“Each of these discoveries changed the way we thought of other worlds,” says Stone. In 1980, Voyager 1 used the gravity of Saturn to fling itself slingshot-style out of the plane of the solar system. In 1989, Voyager 2 got a similar assist from Neptune.
With that assist, both probes set sail into the void.
They presently navigate the "heliosheath," a strange place filled with a magnetic froth no spacecraft has ever encountered before, echoing with low-frequency radio bursts heard only in the outer reaches of the solar system, so far from home that the Sun is a mere pinprick of light.
“In many ways, the heliosheath is not like our models predicted,” says Stone.
No one knows exactly how many more miles the Voyagers must travel before they “pop free” into interstellar space, however. But most researchers believe the end is near.
“The heliosheath is 3 to 4 billion miles in thickness,” estimates Stone. “That means we’ll be out within five years or so.”
There is plenty of power for the rest of the journey. Both Voyagers are energized by the radioactive decay of a Plutonium 238 heat source.This should keep critical subsystems running through at least 2020.
After that, he says, “Voyager will become our silent ambassador to the stars.”