Nearly half a century ago, a probe about the size of a small car launched from Florida on a mission planned to last five years. This week, NASA said it turned off one of Voyager 1’s remaining science instruments — not because the mission failed, but to extend the spacecraft’s life.
Voyager 1, the most distant human-made object, is running low on power. Engineers at NASA’s Jet Propulsion Laboratory are taking steps to delay the inevitable loss of systems so the probe can keep sending data as long as possible.
A mission built for five years that has lasted nearly fifty
Voyager 1 launched on Sept. 5, 1977, from Cape Canaveral atop a Titan-Centaur rocket. It weighs about 1,797 pounds — roughly a mid-size sedan — and carries a 12-foot dish antenna to keep it pointed at Earth for communications. Built at JPL, the spacecraft has operated almost continuously for nearly 49 years.
The mission grew from a rare planetary alignment discovered in the late 1960s that made gravity-assist flybys possible. NASA originally planned a broad “Grand Tour” of the outer planets but scaled the program to the Voyager missions focused on Jupiter and Saturn. The spacecraft were designed for five years; they have now lasted almost ten times that.
Voyager 1 flew past Jupiter in March 1979, revealing active volcanism on the moon Io — the first time volcanoes were observed beyond Earth. It visited Saturn in November 1980, providing close studies of the rings and the moon Titan. The Titan encounter altered Voyager 1’s trajectory out of the solar system’s plane, ending its planetary tour but sending it toward interstellar space.
In 1990, NASA expanded the mission as the Voyager Interstellar Mission to study the edge of the Sun’s influence and beyond. On Aug. 25, 2012, Voyager 1 crossed the heliopause — the boundary where the Sun’s charged-particle wind ends and interstellar space begins — becoming the first human-made object to enter that region. Voyager 2 crossed later, in 2018.
More than 15 billion miles away, on borrowed power
As of this spring, Voyager 1 is more than 15 billion miles from Earth. A radio signal takes over 23 hours to travel one way between Earth and the spacecraft. Every command and every data packet traverses that vast distance.
Voyager runs on a radioisotope thermoelectric generator (RTG) that converts heat from decaying plutonium into electricity. It has no solar panels or rechargeable batteries; the RTG’s power output drops by roughly 4 watts per year. After nearly five decades, that decline is becoming critical.
During a routine maneuver in late February, Voyager 1’s power fell unexpectedly, putting it close to triggering an automatic fault‑protection shutdown — a safety response that would require a long and risky recovery. Engineers acted first to avert that.
Switching off a piece of history to preserve the whole
On April 17, mission engineers sent commands to deactivate the Low‑energy Charged Particles experiment (LECP), one of Voyager 1’s remaining science instruments. LECP measured ions, electrons, and cosmic rays from both the solar system and the galaxy, helping map interstellar structure. Voyager 2’s LECP was turned off in March 2025.
Years ago, the Voyager science and engineering teams agreed on an order for powering down instruments to conserve energy while keeping the most valuable capabilities online. The LECP was next on that list. “While shutting down a science instrument is not anybody’s preference, it is the best option available,” said Kareem Badaruddin, Voyager mission manager at JPL, in a NASA blog.
Voyager 1 now has two operational science instruments: a plasma wave sensor and a magnetometer. Engineers estimate the LECP shutdown could buy the mission roughly another year.
They are also preparing a larger power-saving procedure nicknamed “the Big Bang” — a coordinated swap of several powered components to lower-energy alternatives. Tests on Voyager 2 are planned for May and June 2026; if successful, the same procedure could be attempted on Voyager 1 no sooner than July. If it works, there’s a slim chance LECP might be brought back online.
The team hopes to keep at least one instrument operating on each Voyager into the 2030s, allowing both spacecraft to continue sending data from regions no machine has ever explored before.