Voyager 1 reaches one light-day from Earth on November 18, 2026

NASA's Voyager 1 spacecraft, launched in September 1977, is set to reach a historic milestone on November 18, 2026, when it will be approximately 26 billion kilometers (16 billion miles) from Earth—a distance known as one light-day. At this distance, radio signals traveling at the speed of light take 24 hours to reach the probe, making round-trip communication between Earth and the spacecraft take a minimum of 48 hours. This achievement marks nearly 50 years of continuous operation, far exceeding the probe's original five-year mission design for Jupiter and Saturn exploration.

Maintaining Voyager 1's operations has required increasingly sophisticated engineering solutions as its power source deteriorates. The spacecraft relies on three radioisotope thermoelectric generators (RTGs) that convert heat from plutonium decay into electricity. These generators lose approximately 4 watts of capacity annually. In September 2026, NASA engineers completed a complex power-conservation procedure nicknamed "Big Bang," which simultaneously replaced three onboard heating devices with lower-power alternatives. This operation was critical to preserve the spacecraft's remaining scientific instruments, as without it NASA would have faced shutting down another instrument by summer 2027.

The mission has faced unexpected challenges recently. In October 2026, Voyager 1 experienced a 48-hour communications blackout when NASA's Deep Space Network lost signal contact. Investigation revealed that one of the spacecraft's thrusters had automatically switched to a backup unit as part of the probe's autonomous fault-protection system, though engineers continue investigating the precise connection between this thruster event and the communication loss. The spacecraft successfully resumed contact on October 20.

Experts estimate the remaining RTG power will sustain Voyager 1's operations through the 2030s. The spacecraft continues traveling at approximately 61,000 kilometers per hour (37,844 miles per hour) relative to the Sun, heading toward a star designated AC +79 3888 in the Ursa Minor constellation, which it will approach within 1.7 light-years in approximately 17 light-years—a journey requiring over 300,000 years. Voyager 2, its sister spacecraft, is expected to reach the one light-day milestone approximately nine years later in November 2035.