Their public voice also continues to reach us from this distance. Despite being technologically frozen in the 1970s, the Voyagers have managed to embrace the digital age — now harnessing Twitter to communicate their story. When a Twitter follower asked “what could Voyager 2 see?” it replied in fitting Sagan-esque prose: “I can sense stars and their whispers amid the roaring of our own sun.”
Although they do not tweet every day, both craft still maintain daily contact with the Earth. Even traveling at the speed of light their messages take quite a long time to reach home.
“The journey time is now about 15 hours each way,” Voyagers’ current manager Suzanne Dodd said. “We sent a command [on] Saturday morning and it came back Sunday afternoon.”
Dodd has been with the Voyagers since the mid-1980s and likens keeping in touch with the spacecraft to the nurturing of an elderly senior citizen.
“Sometimes they need a bit of tuning on their hearing,” she said.
It is not just the Voyagers that are aging. Everyone on the team has lived out their lives against the backdrop of their mission.
“When I started on Voyager my two daughters were young,” said Ed Stone, who has been on board since day one.
“By the time they were in college, we had passed Saturn and were on our way to Uranus. They got married and the Voyagers just kept going, and we had grandchildren and Voyager just kept going and our grandchildren are now aware of what’s happening to the Voyagers,” he said.
Barring any serious engineering failures, the Voyagers will both continue to report from interstellar space until around 2025, when declining power and propellant required to point their communication dishes towards Earth will gradually prevent them from calling home.
Were it not for these diminishing consumables and the risk of losing their lock on the increasingly dim and distant Sun, NASA could track them for another century or two.
Yet even without power the two Voyagers will continue to serve us. In the largely empty, benign environment of interstellar space, these craft are likely to last for millions of years. They will outlive the pyramids, they are likely to outlive us, and perhaps even the Earth itself; the only record of our existence, circling the galaxy forever. If other intelligent, technological creatures ever find them, as they drift for eons in deep space, the craft will reveal something about the beings that built them. Our size and dexterity can be inferred from their scale. Their engineering sophistication will tell these creatures something about our technological and mathematical abilities, at least as they were in the 1970s. However, the Voyagers’ design alone will tell them nothing about what kind of creatures we really were.
So while the team at the Jet Propulsion Lab put the finishing touches to the Voyagers in early 1977, spacecraft engineer John Casani suggested to Sagan that they include something on board each craft that would address this. Sagan reasoned that music might be the best way of communicating to other creatures something more about us.
“Could the meaning of music be understood by something else?” Sagan wondered.