NASA has powered down one of Voyager 2’s key science instruments, the plasma science detector, as the spacecraft’s power supply continues to decline. The decision, made to conserve energy, comes as Voyager 2 explores the interstellar medium over 12.8 billion miles from Earth. Despite the shutdown, Voyager 2 will continue to collect data from other instruments, extending its mission into the 2030s.
NASA Shuts Down Voyager 2’s Plasma Instrument as Dwindling Power Threatens Mission
NASA has deactivated one of Voyager 2's science instruments as the spacecraft's power levels continue to decline. Launched in 1977, Voyager 2 is currently more than 12.8 billion miles (20.5 billion kilometers) from Earth, exploring the interstellar medium beyond the heliosphere, the outermost layer of the Sun's influence. While still functioning, the spacecraft is powered by slowly decaying plutonium, leading to gradual reductions in the energy available to operate its systems.
The Decision to Power Down Voyager 2
The deactivated instrument is the plasma science instrument, one of the key tools onboard Voyager 2 that measured the density and direction of ionized particles. Since entering interstellar space in 2018, this instrument has played a vital role in confirming that Voyager 2 had crossed beyond the influence of the Sun’s heliosphere, allowing scientists to monitor the transition from solar wind-dominated space to the largely uncharted regions beyond. However, as the mission has progressed, the plasma science instrument has been used less frequently, with data collection occurring only once every three months during a full rotation of the spacecraft.
NASA engineers faced a difficult decision but ultimately chose to deactivate this system. "The team has confirmed that the switch-off command was executed without incident and the probe is operating normally," NASA’s Jet Propulsion Laboratory noted in a recent statement. Despite its importance, the plasma science instrument was shut down to conserve energy, with other instruments continuing to function. This marks the seventh of the ten original instruments onboard Voyager 2 to be turned off, leaving just a few still active to study the far reaches of interstellar space.
Power Limitations and Future Operation
Both Voyager 1 and Voyager 2 are powered by radioisotope thermoelectric generators (RTGs), which convert the heat produced by the decay of plutonium-238 into electrical power. At launch, Voyager 2's RTGs generated about 470 watts of power, but this output declines by approximately 4 watts each year as the plutonium fuel decays. As a result, power conservation has become increasingly crucial to ensure that Voyager 2 remains operational for as long as possible.
The decision to shut off the plasma science instrument is part of NASA’s long-term strategy to extend the mission’s lifespan. In recent years, mission specialists have turned off various systems not critical to spacecraft operations, including heaters and other instruments no longer essential for data collection.
Preserving the Mission
As Voyager 2 ventures farther into the interstellar medium, the challenges of maintaining communication and functionality increase. With a communication delay of nearly 18 hours each way between Earth and the spacecraft, every adjustment and command must be executed carefully. According to NASA, the remaining four instruments still functioning onboard include a magnetometer, which measures the magnetic fields in interstellar space, and a cosmic ray system, which detects high-energy particles originating from outside the solar system. These instruments are critical to understanding the structure and composition of the interstellar environment.
NASA hopes to keep Voyager 2 operational through the 2030s, but by then, it will likely have only one active science instrument. As power levels continue to dwindle, engineers will need to prioritize which tools are most valuable for ongoing exploration. The plasma science instrument’s reduced usefulness in recent years, due to its orientation and the spacecraft’s position, factored into the decision to deactivate it.
A Remarkable Legacy
Despite these limitations, the Voyager mission remains one of NASA's most significant achievements. Since their launch in 1977, Voyager 1 and Voyager 2 have revolutionized our understanding of the outer planets and now continue to explore uncharted territory in space. Voyager 2 is the only spacecraft to have visited both Uranus and Neptune, providing humanity with unprecedented images and data on these distant ice giants. Its journey through interstellar space, beyond the heliosphere, offers scientists a rare opportunity to study this final frontier.
While the plasma science instrument’s deactivation marks the end of an era for Voyager 2, the spacecraft remains a vital source of knowledge about the interstellar medium. Every year it continues to operate is a testament to the ingenuity of the scientists and engineers who designed and have maintained this historic mission for nearly five decades. The Voyager Interstellar Mission represents a monumental effort to push the boundaries of human knowledge, and even with reduced capacity, Voyager 2's exploration is far from over.