NASA’s Voyager 1 will be one light-day from Earth at 5:16:07 a.m. Eastern time on Wednesday, November 18, 2026, about 16.094 billion miles away. No other human-made object has traveled that far. At that distance, a command from Earth takes a full day to arrive and the reply takes another, so every exchange with the spacecraft takes two days.
Key Takeaways
- Voyager 1 crosses one light-day at 2:16:07 a.m. Pacific and 5:16:07 a.m. Eastern on November 18, 49 years, two months and 11 days after launch.
- NASA lost Voyager 1’s signal on October 18 and 19, and it returned about 48 hours later on October 20, after the spacecraft switched to backup thrusters on its own.
- In September, engineers swapped three power-hungry devices for lower-power ones in an operation nicknamed the “Big Bang.”
- Each Voyager loses about 4 watts of power a year as its plutonium-based generators decay.
- Voyager 2, which took a different route through the solar system, is on pace to reach one light-day in November 2035.
Voyager 1 Crosses One Light-Day at 5:16 a.m. Eastern on November 18
A light-day is the distance light travels in 24 hours. NASA’s Voyager status page puts Voyager 1 at 16.094 billion miles, or 25.902 billion kilometers, from Earth at 2:16:07 a.m. Pacific on November 18. Readers on the East Coast will see the moment at 5:16:07 a.m. That’s standard time, since clocks fell back one hour on November 1.
Voyager 1 launched from Florida on September 5, 1977. It flew past Jupiter and Saturn, then kept going, crossing the heliopause into interstellar space in 2012. It now travels at about 38,000 mph. NASA says reaching the one-light-day mark took 49 years, two months and 11 days.
Nothing physically changes for the spacecraft when it crosses the line. The milestone matters to the people who operate it, because the distance now sets the pace of everything they do.
Every Message to Voyager 1 Now Takes Two Days
Radio signals travel at the speed of light, so once Voyager 1 is a light-day away, a command takes 24 hours to reach it and any response takes another 24 hours to come back. Suzanne Dodd, Voyager project manager at NASA’s Jet Propulsion Laboratory in Southern California, put it simply: a “hello” to Voyager means sending the message, going home, and waiting two days for an answer.
For the engineers, that delay changes how they troubleshoot. A team working on spacecraft near Earth can check the result of a command within minutes. The Voyager team waits two days to learn whether a fix worked, and each check of its findings adds two more.
A 48-Hour Blackout Weeks Before the Milestone
The delay became real in October. NASA’s Deep Space Network, a set of large radio antennas at three sites around the world, failed to pick up Voyager 1’s signal during two scheduled contacts on October 18 and 19, 24 hours apart. At the time, the spacecraft was about 16 billion miles away.
The signal came back on October 20, roughly 48 hours after the interruption began, and contact has held since. Engineers then sent commands to investigate. They found that one set of Voyager 1’s thrusters had stopped working and that the spacecraft had switched to its backup thrusters on its own.
That switch comes from a built-in safety system called fault protection. When the onboard computers detect a possible problem, they can move to backup hardware, put the spacecraft in a stable state and pause normal work until controllers on Earth respond. NASA has not yet determined what caused the problem.
“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,” said Kareem Badaruddin, Voyager mission manager at JPL.
JPL Keeps Voyager 1 Running on Shrinking Power
Both Voyagers run on radioisotope thermoelectric generators, which turn heat from decaying plutonium into electricity. As the plutonium decays, each spacecraft loses about 4 watts of power a year. After nearly five decades, there is almost no power to spare.
In early September, the team completed an operation nicknamed the “Big Bang,” replacing three devices on Voyager 1 with alternatives that use less electricity. The devices help keep the spacecraft warm in the cold of interstellar space, and all three swaps had to happen at the same time to save power while keeping heat spread properly through the spacecraft. The team had done the same procedure on Voyager 2 about six weeks earlier.
The swap bought time for the science. Voyager 1 launched with 10 instruments, and power limits forced NASA to turn off two of them in recent years. Without the Big Bang, NASA could have had to shut down another instrument as early as summer 2027.
Why the Remaining Instruments Still Matter
Voyager 1 and Voyager 2 are the only spacecraft to directly measure the environment outside the heliosphere, the bubble of particles and magnetic fields produced by the Sun. No other mission can collect those measurements today. Every instrument JPL keeps powered extends the only direct record of interstellar space.
Voyager 2 took a longer route to fly past Uranus and Neptune, and NASA says it will reach its own one-light-day mark in November 2035.
FAQs
When will Voyager 1 be one light-day from Earth?
Voyager 1 reaches one light-day at 2:16:07 a.m. Pacific, 5:16:07 a.m. Eastern, on Wednesday, November 18, 2026.
How far is one light-day?
One light-day is the distance light travels in 24 hours. For Voyager 1, NASA puts it at 16.094 billion miles, or 25.902 billion kilometers.
How long does it take to communicate with Voyager 1?
At one light-day, a signal takes 24 hours to reach Voyager 1 and another 24 hours to return, for a 48-hour round trip.
Is Voyager 1 still working?
Yes. Contact resumed on October 20 after a 48-hour interruption, and the spacecraft is still returning data from interstellar space. Power limits have forced NASA to turn off several instruments over the years.
When will Voyager 2 reach one light-day?
NASA says Voyager 2 is on pace to reach one light-day from Earth in November 2035.
How is Voyager 1 powered?
Voyager 1 runs on radioisotope thermoelectric generators, which convert heat from decaying plutonium into electricity. The spacecraft loses about 4 watts of power a year.
