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NASA tweaks Voyager 2's power supply to avoid another sensor shutdown

By redirecting energy from probe's voltage regulator, NASA buys itself another three years

NASA boffins seeking a way to postpone instrument shutdowns on the venerable Voyager spacecrafts have worked out a solution they say will get another three years of power to Voyager 2's five remaining scientific tools.

The trick involves repurposing Voyager 2's onboard voltage regulator, NASA said. That device is designed to trigger a backup circuit in the event electrical flow to Voyager's scientific instruments changes suddenly, which could damage them. 

The regulator draws a small amount of power from Voyager's radioisotope thermoelectric generators and stores it for emergencies, but NASA was able to modify it from 12 billion miles away to shunt that power to the remaining scientific instruments, delaying the need to turn one off until 2026. Without the trick, NASA said an instrument would have had to go offline sometime this year.

"The science data that the Voyagers are returning gets more valuable the farther away from the Sun they go, so we are definitely interested in keeping as many science instruments operating as long as possible," said Linda Spilker, a Voyager project scientist at NASA's Jet Propulsion Laboratory.

Of course, by repurposing the voltage regulator, the power to Voyager 2's systems won't be as tightly controlled, but NASA doesn't seem too bothered by that. "Even after more than 45 years in flight, the electrical systems on both probes remain relatively stable, minimizing the need for a safety net," the space agency said. Beyond that, Voyager mission control has the ability to tweak onboard voltage in the event of an emergency.

Voyager 1 isn't getting the regulator repurpose just yet, as it previously lost a scientific instrument due to equipment failure. With only four remaining instruments, Voyager 1 has another year until an instrument shutdown would be necessary. If NASA determines the change works well for Voyager 2, it may be implemented on Voyager 1 later.

Voyager project manager Suzanne Dodd described the move as low risk with a big reward, that being several more years of scientific data from the Voyager probes before they go dark. "We've been monitoring the spacecraft for a few weeks, and it seems like this new approach is working," Dodd said.

These are the Voyagers ...

Voyager 1 and 2 are identical craft that were launched in 1977 with an original mission duration of four years – just long enough to get the pair to Saturn and Jupiter. NASA extended the Voyager 1 and 2 missions to travel to Neptune and Uranus, and a second extension in 1990 set the craft on course to provide the first readings of the heliosphere, a giant bubble of solar winds that mark the edge of the Sun's magnetic influence on space.

Both of the Voyagers left with 11 onboard instruments, many of which have been shut down over the years to conserve power by eliminating unnecessary components. Along with instruments, NASA has also shut off heaters and other systems that aren't essential to the crafts' core scientific operations.

Voyager 1 reached and passed through the heliosphere in 2012, while Voyager 2 made the same trip in 2018, making the two craft Earth's first interstellar representatives. That's not to say the Voyagers have truly entered the interstellar void - the two craft still have around 300 years of traveling around a million miles a day to make it to the edge of the Oort cloud, the outermost limit of the Sun's gravitational influence. 

The icy, comet-like objects that reside in the Oort Cloud will be the Voyagers' last impression of the Solar System as they coast for 30,000 years to reach its far side, long after the probes have exhausted their radioactive batteries and Earth has hopefully moved beyond operating legacy Fortran code. ®

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