How much time do the Voyagers have left?

It seems like it was just last week, that I posted about one of Voyager 1's experiments being shut down to save power, but it was April 17, just over three weeks ago. Today, Space.com follows up with some interesting input on the Voyagers and a new (optimistic) prediction on how long the Voyagers can last. 

The Voyager 1 and 2 spacecraft were launched within two weeks of each other in August and September of 1977. They originally left on a multiple planetary flyby missions but those were completed in four years. As they completed missions in our solar system, the pair had their cameras and high power consumption instruments shut down with the intent to save power and prolong their missions. 

When they were launched, their Radioisotope Thermal Generators produced 470 Watts. Today, they're both well under 100W. 

Voyager 1 crossed into interstellar space in 2012, and Voyager 2 followed suit six years later. For years, NASA has been turning off the probes' instruments one at a time as their power supplies dwindled. They still lose about four watts of power a year. But NASA's Jet Propulsion Laboratory (JPL) in Southern California has an idea, which will be tested out soon, to give them a little more time. 

Both probes were launched with identical sets of 10 instruments, but over the years have progressively shut down more and more instruments until they're down to the last couple of instruments. Communicating with Earth is the most power intensive thing they do, but they only have to do it rarely - either to download data or to respond to queries from the ground. Voyager 1 is very close to one light day (24 light hours) away and Voyager 2 is 19 light hours away. So "chats", if they existed, would take several days to complete. Originally they had a 20 Watt transmitter, but that's the output power and not what it takes to transmit. 

In a 2022 Suzanne Dodd, project manager for Voyager at JPL, said in a statement about the probes that  "It takes about 200 watts, approximately, to run the transmitter on the spacecraft, to be able to send signals back to Earth."

"An upcoming engineering activity — nicknamed the ‘Big Bang' — on NASA's twin Voyager spacecraft will continue the agency's efforts to maximize the science output of the mission," the spokesperson said in an email.

"Voyager engineers will turn off three devices on the spacecraft that have been used to keep the thruster fuel lines from freezing — and turn on three other devices that will keep the fuel lines warm, but use a total of almost 10 watts less power," the spokesperson continued.

"If successful, this could delay the need to turn off a science instrument aboard each spacecraft by at least one year. The engineering team will test and implement the program on Voyager 2 in May and June. Based on the outcome, the mission plans to do the same on Voyager 1 sometime this summer."

And this is where project manager Dodd dropped the interesting lines.

In August 2022, Dodd was asked during a JPL livestream how far she thought the Voyagers would go. She predicted each spacecraft would "definitely" make it to the 50th anniversary in 2027 — which still seems to be possible from the perspective of today — but added she has a "stretch goal" assuming that gets accomplished.

Ideally, Dodd said she would love to see the spacecraft reach 200 astronomical units (AU; Earth-sun distances) from our planet, which would happen in about 2035. (At the moment, Voyager 1 is about 169.8 AU from Earth, and Voyager 2 is roughly 143.1 AU away.)

If you'll pardon me, this is the first time I've come across someone "on the inside" of the JPL and familiar with the Voyagers that not only seems to be confident the pair will make their golden (50 year) anniversaries next summer, but thinks they have a good shot at surviving another eight years beyond that. 

Artist’s illustration of one of the Voyager spacecraft. Credit: Caltech/NASA-JPL