Why NASA Shut Down a Critical Voyager 2 Instrument to Save the Mission

NASA recently switched off the plasma science instrument on Voyager 2 to conserve power, extending the spacecraft’s operational life. This instrument played a key role in confirming its journey into interstellar space. With power running low, NASA’s decision helps ensure the mission continues collecting data for years to come. Let’s explore why this step is crucial for the mission’s future.

Voyager 2: A Journey Through the Cosmos

Launched in 1977, Voyager 2 has traveled farther than any other spacecraft, second only to its twin, Voyager 1. This mission, originally designed to explore the outer planets of our solar system, exceeded all expectations. After completing its primary mission, Voyager 2 continued its journey, eventually entering interstellar space in 2018, following its sibling, Voyager 1.

Voyager 2’s instruments have provided us with invaluable data about Jupiter, Saturn, Uranus, Neptune, and now, the outer reaches of the heliosphere—the protective bubble created by the Sun’s magnetic field. Along the way, Voyager 2 has given us insight into solar winds, cosmic rays, and the plasma environment of the interstellar medium. But the probe’s power supply has been steadily decreasing over the years, and NASA has had to make tough choices to keep it operational for as long as possible.

The Plasma Science Instrument: Why It Matters

One of the most important tools aboard Voyager 2 is its plasma science instrument. This device has played a critical role in understanding the solar wind and the flow of plasma—charged particles that flow from the Sun and interact with the rest of the solar system. When Voyager 2 crossed the heliopause in 2018, the plasma instrument helped confirm that it had exited the heliosphere and entered interstellar space.

The plasma instrument consists of four “cups” designed to measure the flow of plasma. Three of these cups face the Sun, capturing data on the solar wind inside the heliosphere, while the fourth is oriented at a right angle to observe plasma from planetary magnetospheres and, more recently, interstellar space.

The data provided by this instrument has been crucial for understanding how the Sun’s magnetic field interacts with the rest of the galaxy, but its usefulness has declined in recent years. Because of the spacecraft’s orientation, the instrument no longer faces the direction of plasma flow. It now provides key data only once every three months when Voyager 2 makes a 360-degree turn toward the Sun.

Why Did NASA Turn Off the Instrument?

NASA’s decision to turn off the plasma instrument comes down to one simple reason: power. Voyager 2 is powered by radioisotope thermoelectric generators (RTGs), which convert the heat generated by decaying plutonium into electricity. As the plutonium decays, the amount of power produced decreases year after year.

For much of its mission, this wasn’t a problem. The spacecraft had plenty of power to run its instruments, communications systems, and other essential hardware. However, as Voyager 2 approaches the half-century mark, NASA has had to make tough decisions to keep it going. Already, non-essential systems, including heaters for certain instruments, have been turned off to conserve power.

By turning off the plasma science instrument, NASA hopes to conserve enough power to keep Voyager 2 operational into the 2030s. While the loss of this instrument is significant, it’s a necessary step to prolong the spacecraft’s life and continue gathering data from interstellar space.

The Challenges of Powering a Spacecraft for Decades

The power supply for both Voyager 1 and Voyager 2 comes from RTGs, which have been gradually losing efficiency over the decades. These generators work by converting the heat from decaying radioactive material—specifically, plutonium-238—into electricity. But as the plutonium decays, it produces less heat, and thus less electricity.

NASA engineers have managed to keep the Voyager spacecraft running longer than anyone could have expected, but the dwindling power supply means that each year, they must prioritize which systems to keep running. Last year, they adjusted Voyager 2’s voltage regulator to prevent an automatic shutdown of other science instruments, delaying the inevitable power shortage.

This is one of the key reasons why NASA chose to turn off the plasma science instrument. Although the data it provides is important, it was becoming less useful due to the spacecraft’s orientation. With power levels continuing to decline, the mission team decided to prioritize instruments that could continue to provide valuable data about the space beyond the heliosphere.

What’s Next for Voyager 2?

Even without the plasma science instrument, Voyager 2 remains a valuable tool for studying interstellar space. Other instruments aboard the spacecraft, including those that measure cosmic rays, magnetic fields, and low-energy charged particles, are still operational. These instruments will continue to provide critical data about the environment beyond the heliosphere, helping scientists understand the nature of the boundary between our solar system and the rest of the galaxy.

NASA hopes to keep Voyager 2 operational for at least another decade. If all goes well, the spacecraft could continue to send data back to Earth into the early 2030s. However, the power supply will continue to decline, and more instruments may need to be turned off over time.

Despite these challenges, the Voyager mission is a remarkable success story. Designed for a five-year mission to explore the outer planets, both Voyager 1 and Voyager 2 have exceeded all expectations, providing valuable data for nearly 50 years.

Why This Matters: The Legacy of Voyager 2

The decision to turn off Voyager 2’s plasma science instrument is a reminder of the incredible longevity and importance of the Voyager mission. Launched in 1977, these spacecraft have changed our understanding of the solar system and the space beyond it. They have given us our first close-up views of Jupiter, Saturn, Uranus, and Neptune, and they continue to provide valuable data about interstellar space.

In many ways, the Voyager mission has paved the way for future exploration. As NASA and other space agencies look to send missions to explore the outer planets and beyond, the data provided by Voyager 2 will help inform future missions. And as we continue to explore the universe, the lessons learned from the Voyager mission will continue to guide us.

For now, Voyager 2 remains a testament to human ingenuity and our desire to explore the unknown. Even as its power supply dwindles, it continues to send back data from the farthest reaches of space, giving us a glimpse of the universe beyond our solar system.

Source: Nasa