“The Voyager Probes: Still Collecting Valuable Data 45 Years Later”

Pasadena, California (CNN) When the Voyager probes were separated by weeks in 1977, no one expected that the twin spacecraft would stretch from four years to 45 years and are still going.

Now, the mission team is innovating power supply and instrument strategies on Voyager 1 and 2 to allow the two probes to continue collecting valuable data as they explore uncharted interstellar regions.

Voyager 1 is currently almost the most distant spacecraft from Earth It is 15 billion miles (24 billion km) away, while Voyager 2 has traveled more than 12 billion miles (20 billion km) from Earth. Both are in interstellar space and are the only spacecraft operating beyond the heliosphere, the bubble of the sun’s magnetic field and particles that extend beyond the orbit of Pluto.

As the only extension of humanity outside the protective bubble of the heliosphere, the two probes are alone even in their cosmic journey as they travel in different directions.

Think of the planets of the solar system being in one plane. Voyager 1’s trajectory ascends and descends from the planetary plane after passing Saturn, said Susan Dodd, Voyager project manager at NASA’s Jet Propulsion Plane, while Voyager 2 passes over Neptune and moves on and off the planetary plane. Laboratory in Pasadena, California.

Information collected by these long-lived probes is helping scientists learn about the comet-like shape of the heliosphere and how it protects Earth from energetic particles and radiation in interstellar space.

Voyager 2’s invaluable data was captured and returned to Earth by its five science instruments, while Voyager 1 still had four operational instruments after one of them failed on a previous mission.

But Dodd says it takes a lot of attention and monitoring to keep the “seniors” working.

“I would describe them as twins,” Dowd told CNN. “One lost his hearing and needed a hearing aid, and the other lost his sense of touch. So, they fail differently over time. But overall, they are quite healthy for their age.”

Instruments designed to observe planets while Voyager explored the solar system in the 1980s were shut down to reuse memory for interstellar missions that began in 1990, Dodd said. Voyager 1 reached the atmospheric limit in 2012, while the slower Voyager 2 crossed the boundary in 2018.

Both Voyager probes rely on radioisotope thermoelectric generators. The nuclear power supply loses 4 watts per year as the plutonium it relies on slowly decays and heat is converted to electricity. Over time, the Voyager team ordered the probe to turn off the instrument heaters and other non-essential systems.

“But (Voyager) also gets really cold and we need to keep the fuel lines pretty warm, about 2 degrees Celsius.” (35.6 degrees Fahrenheit). If they freeze, we may lose the ability to point to Earth. So there’s a balance between energy and heat and how we operate the spacecraft,” said Dodd.

delicate balance

The team was pleasantly surprised that the recalibrated instrument became slightly more sensitive at collecting data because some of Voyager’s detectors performed better when it was colder.

“One way to look at it,” says Linda Spilker, Voyager project scientist at the Jet Propulsion Laboratory, “is to think of Voyagers as cabins up in the mountains, and it’s really cold out there. Turn off the lights inside to save your energy. You also have to lower the thermostat, and it still works fine.”

Voyager 2 started using a small backup power reserve that is part of a safety mechanism, allowing the spacecraft to turn off other science instruments until 2026 instead of this year. The safety mechanism, which protects the instruments if the amperage in the spacecraft changes drastically, contains a small amount of power that acts as a backup circuit.

Now, that power can be used to keep Voyager 2’s instruments running.

The spacecraft’s electrical system was still largely stable, so the team decided it was a small risk for a bigger reward for being able to gather science data. The team will continue to monitor the Voyager 2 effort and act accordingly if there are any fluctuations.

If this strategy works for Voyager 2, it could also apply to Voyager 1, where the team should consider closing other science instruments on the spacecraft by 2024.

“Instead of shutting down scientific instruments, we might want to do something really creative, from an engineering standpoint, to get another year of science data,” Dodd said. “It propels the spacecraft in a way it was never designed to power.”

The Plasma Science Instrument on Voyager 2 is still operational, allowing direct measurements of plasma density in interstellar space. Space plasma consists of charged particles, the movement of which is controlled by electric and magnetic forces NASA.

“Think of it as an ocean of space with constant waves and turbulence and activity, and Voyager’s instruments can measure what’s going on,” Spilker said. “Before you go to a new place, you make predictions about what you think you will find when you get there. With Voyager, we learned to be surprised.”

Scientists expected that the plasma density decreased as Voyager got farther from the Sun, but it increased instead. Spilker said the probe can measure and see the shocks as they propagate from the sun.

As long as Voyager 1 and 2 remain healthy, the aging probes will likely continue their record-breaking missions for years to come.