Voyager Spacecraft: A Legacy of Exploration

The Voyager spacecraft have been traversing the vast expanse of interstellar space for over 47 years, accumulating invaluable data on the cosmos. However, their prolonged journey has taken a toll on these farthest human-made objects, and their operational days are limited. To prolong their mission, NASA engineers are compelled to deactivate science instruments on both Voyager probes.

Conserving Energy to Extend Mission Life

On February 25, mission engineers at NASA’s Jet Propulsion Laboratory deactivated Voyager 1’s cosmic ray subsystem experiment, and they plan to shut off the low-energy charged particle instrument aboard Voyager 2 on March 24, as announced by NASA. These energy-conserving measures will enable the twin probes to operate for an additional year or so, before engineers are forced to deactivate two more instruments. The spacecraft have been experiencing glitches over the past couple of years, and this grim reality underscores the challenges of maintaining these iconic missions.

A Bittersweet Decision

"The Voyagers have been deep space rock stars since launch, and we want to keep it that way as long as possible," said Suzanne Dodd,! Voyager project manager at JPL. "However, electrical power is dwindling. If we don’t deactivate an instrument on each Voyager now, they would likely have only a few more months of power before we would need to declare the end of the mission." The Voyagers are powered by heat from decaying plutonium, which is converted into electricity, and they lose about 4 watts of power each year.

A Legacy of Scientific Discovery

The Voyager spacecraft were initially equipped with 10 science instruments when they launched in 1977, but they now have only three instruments each. Some instruments were necessary for planetary flybys and were deactivated after the spacecraft completed their exploration of the solar system’s planets. Voyager 1 entered interstellar space in 2012, while Voyager 2 reached the boundary in 2018, traveling beyond the protective bubble surrounding the solar system known as the heliosphere.

Instrument Deactivation: A Necessary Measure

In October 2024, the team deactivated Voyager 2’s plasma science instrument to conserve power. Voyager 1’s cosmic ray subsystem, which was shut down last week, is a suite of three telescopes designed to study cosmic rays by measuring their energy and flux. The data collected by these telescopes helped the Voyager team determine when and where Voyager 1 exited the heliosphere, according to NASA. Voyager 2’s low-energy charged particle instrument, scheduled for deactivation later this month, measures various ions, electrons, and cosmic rays originating from our solar system and galaxy.

Future Plans and Legacy

Voyager 1 still has its magnetometer and plasma wave subsystem, and its low-energy charged particle instrument will be shut off next year. Voyager 2 will continue to collect data through its magnetic field and plasma wave instruments, while its cosmic ray subsystem is scheduled to be shut off in 2026. "The Voyager spacecraft have far surpassed their original mission to study the outer planets," said Patrick Koehn, Voyager program scientist. "Every bit of additional data we have gathered since then is not only valuable bonus science for heliophysics but also a testament to the exemplary engineering that has gone into the Voyagers — starting nearly 50 years ago and continuing to this day."

A Journey of Discovery

Voyager 1 launched on September 5, 1977, less than a month after its twin probe, Voyager 2, began its journey to space. The spacecraft took a faster route, exiting the asteroid belt earlier than its twin, and made close encounters with Jupiter and Saturn, where it discovered two Jovian moons, Thebe and Metis, and five new moons, and a new ring called the G-ring, around Saturn. Voyager 2 was launched on August 20, 1977, on a trajectory toward the solar system’s gas giants, Jupiter and Saturn, and explored the icy giants Uranus and Neptune.

The Current State of the Voyagers

Voyager 1 is more than 15 billion miles (25 billion kilometers) away from Earth, while Voyager 2 is over 13 billion miles (21 billion kilometers) away. With the current energy-conserving plan, NASA engineers believe the twin spacecraft could continue operating into the 2030s with one instrument each. "Every minute of every day, the Voyagers explore a region where no spacecraft has gone before," said Linda Spilker, Voyager project scientist at JPL. "That also means every day could be our last."