How the Voyager probes go and go decades after launch | CNN

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When the Voyager probes lifted off weeks apart in 1977, no one expected that the twin spacecraft would extend their missions from four years to 45 years.

Now, the mission team is getting creative with its strategies for powering and instrumenting both Voyager 1 and 2, enabling both probes to continue collecting valuable data as they explore uncharted interstellar territory.

Voyager 1 is currently the farthest spacecraft from Earth At a distance of 15 billion miles (24 billion kilometers), Voyager 2 traveled more than 12 billion miles (20 billion kilometers) from Earth. Both are in interstellar space and the only spacecraft to operate beyond the heliosphere, the Sun’s bubble of magnetic fields and particles extends beyond Pluto’s orbit.

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

Think of the planets of the solar system as existing on the same plane. Voyager 1’s trajectory took it up and out of the planetary plane after passing Saturn, while Voyager 2 passed over Neptune and moved down and out of the planetary plane, said Suzanne Dodd, Voyager’s project manager at NASA’s Jet Propulsion. Laboratory in Pasadena, California.

The information collected by these long-duration probes is helping scientists learn about the shape of the comet’s heliosphere and how it shields Earth from energetic particles and radiation in interstellar space.

Voyager 2’s valuable data was captured and returned to Earth by its five science instruments, while Voyager 1 has four more operational instruments after the previous one failed in the mission.

But it took a lot of care and oversight for “senior citizens” to act, Dodd said.

“I would describe them as twin sisters,” Dodd told CNN. “One has lost his hearing and needs some hearing aids, and the other has lost some sense of touch. Therefore, they have failed differently over time. But in general, they are very healthy for how old they are.

Instruments designed to look for planets as the Voyager probes toured the solar system in the 1980s were turned off to recycle memory for the interstellar mission that began in 1990, Dodd said. Voyager 1 reached the heliosphere boundary in 2012, while the slower Voyager 2 crossed the boundary in 2018.

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

“But (Voyager) gets very cold and we have to warm the propellant lines quite a bit, about 2 degrees Celsius. (35.6 degrees Fahrenheit). If they freeze, we may lose our ability to show up to Earth. “So it’s a balancing act between power and thermal and how we operate the spacecraft,” Dodd said.

The team was pleasantly surprised when the instruments were recalibrated to be a little more sensitive in their data collection, as some Voyager detectors work better when cold.

“One way to look at it is maybe think of the two Voyagers as being like cabins on top of a mountain, and it’s very cold there,” said Linda Spilker, Voyager’s project scientist at JPL. You are doing well.

Voyager 2 has begun using a small backup power reserve as part of a safety mechanism that will prevent the spacecraft from shutting down another science instrument until 2026, rather than this year. A safety mechanism includes a small amount of power that acts as a backup circuit to protect the equipment in case the power flow in the spacecraft changes significantly.

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

The spacecraft’s electrical systems are largely stable, so the team decided it was a small risk for the big reward of being able to collect science data. The team will continue to monitor Voyager 2’s voltage and act accordingly if there are fluctuations.

If this strategy works for Voyager 2, it could also be implemented on Voyager 1, as the team will have to consider decommissioning another science instrument on the spacecraft in 2024.

“Instead of turning off the science equipment, we wanted to do something very creative, engineering-wise, to get another year of science data,” Dodd said. “It’s operating the spacecraft in a way it was never designed to operate.”

Voyager 2’s plasma science instrument is still operational, so it can take direct measurements of the density of plasma in interstellar space. Space plasma is a substance made up of charged particles whose motion is controlled by electric and magnetic forces, according to NASA.

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

Scientists had expected the density of the plasma to decrease as Voyager moved further from the Sun, but instead it increased. And probes can measure and see shocks from the Sun, Spilker said.

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