Martian Alpha Voyager 1 Reaches One Light-Day From Earth: What It Means
On Nov. 18, 2026, Voyager 1 becomes the first human-made object one light-day (25.9 billion km) from Earth. What a light-day is and how far Voyager has come.
On Wednesday, November 18, 2026, at 2:16:07 a.m. PST, NASA says Voyager 1 will be 16.094 billion miles (25.902 billion kilometers) from Earth, the distance light travels in 24 hours, or one light-day. No other human-made object has been that far away. The milestone is about distance, not time: it means a radio signal from Earth will take a full day to reach the spacecraft, and the reply another day to come back. Voyager 2 is on pace to reach the same distance in November 2035.
What a light-day is#
NASA defines a light-day as the distance light travels in 24 hours: 16,094,799,096 miles (25,902,068,356 km). Putting it next to other light-distances makes the scale clear, using NASA's own figures:
| Distance | Light (or radio) travel time |
|---|---|
| Earth to the Moon (238,855 miles on average) | 1.3 seconds |
| Sun to Earth (93 million miles) | about 8 minutes 20 seconds |
| Earth to Mars | 3 to 22 minutes, depending on where the planets are |
| Neptune (about 2.8 billion miles from Earth on average) | about 4 hours 10 minutes |
| Voyager 1 on November 18, 2026 | 24 hours |
By simple arithmetic from the definition, a command sent to Voyager 1 at that moment would take a day to arrive and the acknowledgment another day to return: a 48-hour round trip. For comparison, NASA notes the nearest star system, Proxima Centauri, is about 4.24 light-years away.
How Voyager 1 got here#
Voyager 1 launched in 1977 and has been in flight for nearly 50 years. NASA says it will have taken 49 years, two months and 11 days to travel one light-day from Earth. It's cruising at nearly 38,000 mph (61,000 km/h); NASA's Voyager FAQ describes its escape from the solar system as about 3.5 AU a year (an AU is the Earth-Sun distance, about 93 million miles).
Voyager 1 and its twin are the only spacecraft ever to operate outside the heliosphere, the protective bubble of particles and magnetic fields generated by the Sun. Voyager 2 took a different path, visiting Uranus and Neptune, and travels more slowly, at about 3.1 AU a year.
Voyager 1 is headed toward the star AC +79 3888 (Gliese 445) in Ursa Minor, and NASA expects it to pass within about 1.7 light-years of that star in 40,000 years. Even at 38,000 mph, the spacecraft is a crawl compared to light.
Still talking, with fewer instruments#
NASA's FAQ notes that both Voyagers were still functioning in April 2026. Each spacecraft's radioisotope power source produces about 4 watts less each year, so the mission has turned instruments off one by one to keep the most valuable ones running. NASA's instrument table, updated April 17, 2026, shows on Voyager 1:
- Magnetometer and Plasma Wave Subsystem: on.
- Cosmic Ray Subsystem: off to save power (February 25, 2025).
- Low-Energy Charged Particles: off to save power (April 17, 2026).
- Cameras: off since 1990.
Voyager's computers process about 8,000 instructions per second, against more than 14 billion for a modern smartphone, according to NASA.
Why the milestone matters for space business#
Voyager is a government science mission, not a company, but it shows the economics of deep space: signal delay, power, and long lifetimes. Planning communications with spacecraft at the Moon, Mars and beyond runs on the same physics that makes a light-day. For the trajectories that get spacecraft to other planets in the first place, see our guide to porkchop plots and Mars launch windows, and for the propellant maths, the rocket equation worked examples.
Follow it on Martian Alpha#
Martian Alpha's Deep-Space Mission Tracker (free account) shows the distances from Earth and the Sun for Voyager 1 and 2, JWST, Europa Clipper, Parker Solar Probe and other spacecraft, with mission timelines and upcoming milestones, including this one. The 3D solar system viewer places the planets and probes on any date. NASA's own Eyes on the Solar System tool is the official live visualization, so treat our page as a convenient companion and check NASA for the exact figure and the countdown.
FAQ#
When does Voyager 1 reach one light-day from Earth?#
NASA says on Wednesday, November 18, 2026, at 2:16:07 a.m. PST, when it will be 16.094 billion miles (25.902 billion km) away.
How long does a signal take to reach Voyager 1?#
At one light-day, a signal takes 24 hours one way, by definition of a light-day, so a round trip takes 48 hours.
How fast is Voyager 1 travelling?#
NASA gives nearly 38,000 mph (61,000 km/h), or about 3.5 AU a year.
When will Voyager 2 reach one light-day?#
NASA says November 2035.
Is Voyager 1 still working?#
According to NASA's Voyager FAQ, both Voyagers were still functioning in April 2026, with several instruments switched off to save power.
Sources#
- NASA Science, Voyager 1: What Is a Light-Day?: https://science.nasa.gov/mission/voyager/voyager-1/voyager-1-what-is-a-light-day/
- NASA Science, Where Are Voyager 1 and Voyager 2 Now? (instrument status updated April 17, 2026): https://science.nasa.gov/mission/voyager/where-are-voyager-1-and-voyager-2-now/
- NASA Science, Voyager Frequently Asked Questions: https://science.nasa.gov/mission/voyager/frequently-asked-questions/
This article is for information only and is not financial advice. Do your own research before making any investment.