NASA is set to shut down the Low Energy Charged Particle Instrument on Voyager 2 as part of efforts to conserve power and extend the spacecraft's mission life. This instrument measures ions, electrons, and cosmic rays from the solar system and our galaxy, and its deactivation marks a step in managing the dwindling power resources of the decades-old probe.
The decision comes as the Voyager spacecraft face diminishing power supplies due to the gradual decay of their radioactive plutonium. "If we don't turn off an instrument on each Voyager now, they probably only have a few months left," said Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory.
Both Voyager 1 and Voyager 2 are losing about four watts of power each year due to the decay of their radioisotope power systems, decreasing from an initial output of about 470 watts at launch. To conserve energy and extend the missions, NASA has been gradually shutting down instruments and subsystems on both spacecraft.
In February 2023, NASA's control center deactivated the cosmic ray subsystem experiment on Voyager 1, which measured the energy and flow of cosmic radiation particles.
The twin Voyager spacecraft are the most distant human-made objects in space, located beyond the outer boundary of the heliosphere in interstellar space. Voyager 1 is over 15 billion miles (25 billion kilometers) away from Earth, while Voyager 2 is over 13 billion miles (21 billion kilometers) away. No other human-made spacecraft has reached interstellar space.
Launched in 1977—Voyager 2 on August 20 and Voyager 1 on September 5—both spacecraft are identical probes carrying ten scientific instruments, of which only three are currently operational. Over the years, several instruments have been turned off to conserve power, including those designed for planetary observations during their flybys.
"Every minute of every day, the Voyagers explore a region where no spacecraft has gone before," said Linda Spilker, Voyager project scientist at NASA's Jet Propulsion Laboratory, according to Live Science. Both spacecraft left our solar system, with Voyager 1 crossing the heliosphere boundary in 2012 and Voyager 2 in 2018 after its flyby of Neptune.
The Voyager spacecraft are powered by Radioisotope Thermoelectric Generators that produce electricity using plutonium-238. As the plutonium decays, the power output diminishes, necessitating the shutdown of instruments to conserve energy for critical systems.
NASA aims to extend the missions of Voyager 1 and Voyager 2 until at least 2030 by conserving power, hoping both spacecraft can continue operating with at least one scientific instrument into the 2030s. Engineers believe that by implementing these power-saving strategies, the probes will have enough electricity to run at least one research instrument far into the 2030s.
"The Voyager probes have greatly exceeded their original mission to study the outer planets of the Solar System," said Patrick Koehn, a scientist from the Voyager program. "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."
Starting in April 2024, each Voyager spacecraft will have only three of the original ten instruments still operational, although this number will drop to two in 2026.
Communication with the spacecraft poses challenges due to the vast distances involved. A radio signal takes over 23 hours to reach Voyager 1 and 19.5 hours to reach Voyager 2. Nevertheless, the data collected over the years have provided new insights into the environment beyond the solar system, including changes in charged particle levels and magnetic fields in interstellar space.
Voyager 1 detected a small ring around Jupiter and many of Saturn's moons during its flybys. Voyager 2 remains the only spacecraft to have visited Uranus and Neptune, providing data about these distant planets.
Even as instruments are turned off, NASA emphasizes that shutting down scientific instruments does not mean the end of the Voyager missions. Linda Spilker also stated, "This means that each day could be our last, but it could just as well bring another interstellar discovery."
Engineers will continue to monitor the condition of both spacecraft and make adjustments as necessary so that Voyager can continue to contribute to science for as long as possible.
The article was written with the assistance of a news analysis system.