Voyager, 1, humanity's most distant spacecraft, is back in contact after briefly losing touch with Earth last month.
The spacecraft stopped phoning home for about 48 hours between Oct. 18 and 20 due to a communications glitch that Voyager 1 resolved on its own, before engineers could send the long-running spacecraft a remote fix.
"This is the first time we've seen the spacecraft do something like this, but we are also at a point in the mission where we have to expect the unexpected," Kareem Badaruddin, Voyager mission manager at NASA's Jet Propulsion Laboratory (JPL), said in an agency statement about the incident on Oct. 29.
Voyager 1 is almost one light-day from Earth, meaning that a command takes nearly a day to reach the spacecraft and a response takes another day to come back to our planet. The spacecraft will reach the light-day milestone on Nov. 18, at 16.09 billion miles (25.89 billion kilometers) from Earth.
NASA's Deep Space Network of three antennas does check-ins to make sure the spacecraft is doing well. On Oct. 18 and 19, Voyager 1 did not respond. Its signal fortunately reappeared on Oct. 20.
"Engineers still are investigating what caused the communication loss," JPL added in the statement, but said it appears Voyager 1 went into a sort of safe mode. "The team has so far determined that one group of thrusters went offline and their backups turned on. Such a swap is programmed to occur automatically if the spacecraft computers detect something amiss with the active thrusters."
Voyager 1 and its still-operational twin, Voyager 2, both launched in 1977 on an initial mission to explore planets in the solar system. The two spacecraft took advantage of a rare alignment that allowed them to swing from Jupiter to Saturn to Uranus and Neptune using a minimum of fuel, although funding to explore the more distant planets and moons was not guaranteed at launch.
The spacecraft duly swung by Jupiter's and Saturn's systems (some months apart from each other) to great acclaim before parting pathways. Voyager 1's close-up view of Saturn's rings as well as the moon Titan — which may have prebiotic or pre-life chemistry — altered the spacecraft's trajectory to put it high above the plane of the solar system. Meanwhile, Voyager 2 flew on to Uranus and Neptune in 1986 and 1989, respectively, providing the only up-close view of these planetary systems to date.
Running on nuclear power, and continuing to deliver valuable science from deep space, the Voyagers saw their missions extended repeatedly. Both crossed into interstellar space a few years ago, and are still operational.
But with age comes a cost: the plutonium power sources on both spacecraft are diminishing, requiring engineers to periodically shut off instruments or come up with other clever ways of saving power. Voyager 1 just underwent one of those power adjustments, nicknamed the "Big Bang" because it reconfigured a number of spacecraft instruments.
"In early September, engineers successfully turned off three devices on the Voyager 1 spacecraft and substituted them with three lower-power alternatives," JPL wrote of the effort, noting that Voyager 2 also had a "Big Bang" about six weeks previous to that.
JPL did not provide an estimate for how long the missions could keep running, but noted each spacecraft loses four watts of power a year — each launched with 470 watts — and that the spacecraft could continue operating science instruments "longer than previously anticipated" due to the Big Bang. On Voyager 1, for example, the falling power would have otherwise meant switching off another instrument possibly as soon as next summer.
In 2022, Suzanne Dodd, project manager for Voyager at JPL, stated the hope was the mission would continue to operate into the 2030s.
