The Plasma Science Instrument consists of four cups that collect information about the amount of plasma, the fluid charged particles flowing around Voyager 2, and the direction of this flow. The three cups face the Sun and monitor the charged particles of the solar wind as they move through the heliosphere. A fourth cup is placed behind the other four samples to detect plasma in planetary magnetic fields and interstellar space.
The plasma instrument was instrumental in detecting the decrease in the amount of charged particles streaming from the Sun, and in 2018 it showed that Voyager 2 had crossed the boundary between the heliosphere and interstellar space.
Officials at NASA’s Jet Propulsion Laboratory, which oversees the Voyager mission, said in a statement: “Mission engineers are constantly monitoring changes made to the operation of the 47-year-old spacecraft to ensure they do not cause any unwanted side effects. “The team has confirmed that the shutdown command was successfully executed and the probe is operating normally.”
In 2018, the Plasma instrument showed that Voyager 2 crossed the boundary between the heliosphere and interstellar space.
After Voyager 2 exited the heliosphere and passed through the solar wind, the three sunward cups stopped collecting plasma, limiting the usefulness of the plasma instrument. Also, because of Voyager 2’s orientation, the data it has collected over the past few years has become even more limited. The only active cup provides useful data only once every three months when the spacecraft completes a 360-degree spin on its axis. This influenced the decision to turn off the plasma tool in order to save energy.
In the 1980s, after the two spacecraft finished exploring the solar system’s gas giants, engineers turned off several of their instruments. This gave both probes extra power and increased their lifespan. A few years ago, two spacecraft also turned off all their non-essential instruments. Voyager 1’s plasma instrument stopped working in 1980 and was turned off in 2007 to conserve energy.
Meanwhile, NASA engineers are closely monitoring Voyager 2 to decide when to shut down the next science instrument. By doing so, they ensure that this human interstellar probe can explore as far beyond the solar system as possible.
