Sooner or later, the workhorse spacecraft will bid adieu to the solar system and enter a new realm of space — the first time a manmade object will have escaped to the other side.
Perhaps no one on Earth will relish the moment more than 76-year-old Ed Stone, who has toiled on the project from the start.
"We're anxious to get outside and find what's out there," he said.
When NASA's Voyager 1 and Voyager 2 first rocketed out of Earth's grip in 1977, no one knew how long they would live. Now, they are the longest-operating spacecraft in history and the most distant, at billions of miles from Earth but in different directions.
Wednesday marks the 35th anniversary of Voyager 1's launch to Jupiter and Saturn. It is now flitting around the fringes of the solar system, which is enveloped in a giant plasma bubble. This hot and turbulent area is created by a stream of charged particles from the sun.
Outside the bubble is a new frontier in the Milky Way — the space between stars. Once it plows through, scientists expect a calmer environment by comparison.
When that would happen is anyone's guess. Voyager 1 is in uncharted celestial territory. One thing is clear: The boundary that separates the solar system and interstellar space is near, but it could take days, months or years to cross that milestone.
Voyager 1 is currently more than 11 billion miles from the sun. Twin Voyager 2, which celebrated its launch anniversary two weeks ago, trails behind at 9 billion miles from the sun."