Voyager 1 Reaches One Light-Day From Earth

By SpaceInfo ADM

November 12, 2026 6 min read

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The short version

Voyager 1 reaches one light-day from Earth on Wednesday, November 18, 2026, at 5:16 a.m. EST (10:16 UTC), according to NASA. That is about 25.9 billion km, or 173 astronomical units, the distance light travels in 24 hours. No other human-made object has ever been this far from home, and a command sent to the probe now needs about a day to arrive, with the reply taking another day to come back.

What one light-day actually means

One light-day is the distance light covers in 24 hours: 299,792.458 km/s multiplied by 86,400 seconds gives 25.9 billion km, or 173.14 AU. It is a measure of distance, not of time, and NASA says so explicitly. The table below shows how that compares with other places in light-travel time (average distances, calculated from standard values).

Place	Distance from Earth or Sun	Light travel time
The Moon	384,400 km	1.3 seconds
The Sun	149.6 million km (1 AU)	8 min 19 s
Neptune	about 30 AU from the Sun	about 4 h 10 min
Voyager 1 at the heliopause (2012)	about 121 AU	about 17 hours
Voyager 1 on November 18, 2026	173.14 AU	24 hours
Proxima Centauri	4.25 light-years	about 1,550 days

The last row puts the milestone in proportion. After more than 49 years of flight, Voyager 1 has covered roughly 1/1,550 of the way to the nearest star, and it is not aimed at it. Even so, sunlight needs a full day to reach it. From there the Sun is a single point of light that is still roughly ten times brighter than the full Moon looks from Earth (a calculation from the inverse-square law, not a NASA figure).

Voyager 1 today: two science instruments and a thin power margin

Voyager 1 loses about 4 watts of electrical power every year as its plutonium generators decay, and NASA has spent 2026 deciding what to switch off to keep it alive. The probe flies at about 17 km/s (61,155 km/h) relative to the Sun, and the milestone changes nothing on board: NASA calls it symbolic.

Date	What happened
Oct 18 to 20, 2026	The Deep Space Network detects no signal in two scheduled contacts. The signal returns on Oct 20. One group of thrusters went offline and its backups switched on; the cause is still under investigation.
Early Sept 2026	The “Big Bang” fix: three devices are swapped for lower-power ones, all at once, to keep heat evenly distributed. Without it, another instrument would have been shut down as early as summer 2027.
Apr 17, 2026	Engineers switch off the Low-Energy Charged Particles instrument (LECP) to avoid triggering undervoltage fault protection. A small motor stays on so it can be restarted.
Feb 27, 2026	Power drops unexpectedly during a planned roll maneuver.

According to NASA’s April announcement, two science instruments are left on Voyager 1: the plasma wave subsystem and the magnetometer. Kareem Badaruddin, Voyager mission manager at JPL, said shutting one down “is not anybody’s preference, it is the best option available.” We covered the October signal loss in detail in Voyager 1 Reconnects Ahead of Its One Light-Day Milestone.

Operating a spacecraft with a 48-hour round trip

From November 18, every question the team asks Voyager 1 gets its answer two days later. Radio signals need 24 hours to reach the probe and another 24 hours to come back, so there is no live control, only commands sent in advance and checked afterwards. Suzanne Dodd, Voyager project manager at JPL, describes it as waiting two days before you finally get a response.

The April shutdown of the LECP instrument shows how one change plays out:

Engineers write the command sequence and verify it on the ground, because nothing can be corrected after transmission.
A Deep Space Network antenna sends the commands. In April they took about 23 hours to reach the spacecraft.
Voyager 1 executes them. Switching off the LECP took about 3 hours and 15 minutes.
Telemetry travels back for about another 23 hours, and only then can the team confirm the result.

That delay is why the spacecraft has to protect itself. When one group of thrusters went offline in October, Voyager 1’s onboard fault protection switched to the backups and put the probe into a safe, stable configuration without waiting for anyone on Earth. The same logic explains the fear behind the April shutdown: if power fell too far, undervoltage fault protection would start switching off components on its own, and recovery would take a long time at two days per exchange. Sources: NASA, October 29, 2026 and NASA, April 17, 2026.

How to take part on November 17 and 19

NASA has planned two public events around the milestone, described in the JPL announcement. Times below are converted for Central European Time (UTC+1).

When	What	How to join
Tuesday, Nov 17, after sunset (local time)	“Shine Bright for Voyager’s Light-Day”: a symbolic wave of golden light around the planet. A NASA web page makes a phone or tablet flash “VGR”, Voyager’s call sign, in Morse code.	go.nasa.gov/shinebright. Share photos or video and tag @NASA.
Wednesday, Nov 18, 5:16 a.m. EST (11:16 CET)	Voyager 1 reaches one light-day from Earth.	No event, but a good moment to post.
Thursday, Nov 19, 12 p.m. EST (18:00 CET)	Moderated discussion at JPL’s von Kármán Auditorium on the state of Voyager 1 and 2, their interstellar science and the challenge of operating them. Q&A follows, with a preview of the NASA+ Voyager documentary planned for 2027.	Live on NASA Live.

The panel includes Nicky Fox (NASA associate administrator for science), Jonathan Lunine (JPL chief scientist), Suzanne Dodd (Voyager project manager), Kareem Badaruddin (Voyager mission manager) and Jamie Rankin (Voyager deputy project scientist, Princeton University).

Frequently asked questions

How far is one light-day?

One light-day is 25.9 billion km, about 16.1 billion miles or 173.14 AU. It is the distance light travels in 24 hours.

When does Voyager 1 reach one light-day from Earth?

NASA gives November 18, 2026, at 5:16 a.m. EST, which is 10:16 UTC and 11:16 in Central European Time.

Is Voyager 1 still working?

Yes. NASA reported two science instruments still running in April 2026, the plasma wave subsystem and the magnetometer. Contact was lost for about 48 hours on October 18 to 20, 2026, and the signal returned on October 20.