The delicate tradeoffs keeping NASA’s Voyager exploring

NASA’s Voyager 1, the age-defying satellite that flew by the far-reaching planets in the solar system, is back at work again.

NASA’s Jet Propulsion Laboratory in California announced Sept. 10 that its engineers had swapped out which set of thrusters the satellite uses after a fuel tube the size of a needle unexpectedly became clogged with silicon dioxide.

With a 47-year-old satellite, things happen.

In April, engineers solved a computer problem after Voyager stopped sending back readable science and engineering data. And fuel tubes aboard Voyager had clogged a generation ago in 2002 and then again in 2018.

But while swapping thrusters may sound like a straightforward solution, every decision on a satellite 15 billion miles away from Earth carries its own second- and third-order effects.

Over the years, the Voyager team has gradually turned off all non-essential onboard systems and some instruments as a way to extend its life and save power, which comes from decaying plutonium. Along the way such steps have also included turning off heaters, which results in making the satellite colder. However, turning on another set of now cold thrusters creates the risk that they might not work.

The solution? NASA’s team decided to turn on the heaters, turn off an instrument to save energy, and then once the thrusters were warmer, turn them back on before then turning the heaters off again.

It worked. On Aug. 27, NASA officials learned the series of commands were successful.

“We switched back to a previous branch, giving us another couple of years,” Linda Spilker, a Voyager project scientist at JPL, told the Space Project. “We're trying to balance all that with the focus of getting science for as long as we can on Voyager. It's a great engineering challenge.”

Voyager, which launched in 1977, was made famous for its ambitions and at the time for its golden record, which included music for any extraterrestrial life that might encounter it. Later, it provided the first images of celestial objects such as Jupiter’s bright white moon Europa and became a hallmark of space exploration.

But now the next goal for NASA is for the satellite to get to its 50th anniversary and then for scientists and engineers to focus on operating into the 2030s.

“We thought the mission would last four years, and now here we are (coming up on) the 50th anniversary, and it's a great time to celebrate, reminisce about everything Voyager did, and what is still to come,” Spilker said.

Voyager left interstellar space, the place where the sun’s flow of material and magnetic field ceased affecting its surroundings, in 2012. Since then, its science and data have been helping NASA’s teams understand the heliopause, the boundary where the pressure from the sun is balanced by the pressure of the interstellar medium.

NASA expects that Voyager will be able to transmit data via a faint signal and remain in range of the Deep Space Network until about 2036, but until then, every decision like those last month, will require a bit of extra forethought.

“One of these days … we won't get anything back, no tone, no signal, no data,” Spilker said. “We may not ever know exactly what happened. Did a component finally break? Did we reach some other threshold? Did a thruster finally clog? … I don't think we know until it happens.”