The voyage of the voyagers

Last month, there was a glitch with the Voyager 2 spacecraft, but Earth engineers were able to fix it, even though it’s 11.5 billion miles away. From Forbes:

NASA’s Voyager 2 spacecraft is recovering from a scary moment earlier this week, when its onboard computer automatically shut down the spacecraft’s science instruments to keep the spacecraft from draining its power supply. Engineers at NASA’s Jet Propulsion Laboratory say the science instruments are back on, and Voyager 2 should get back to science as usual soon.

The trouble started on January 25, when Voyager 2 was supposed to make a 360⁰ roll to help calibrate its magnetometer. But when the spacecraft’s computer tried to execute the commands it needed to make the roll, it got the timing wrong. As a result, two systems that don’t normally run at the same time ended up running at the same time – and both systems draw a lot of power. Since Voyager 2 is running on a limited power supply courtesy of its onboard generator, this was exactly the sort of problem that could have put the mission in mortal peril.

Fortunately, Voyager 2 (like its twin sibling Voyager 1) was programmed to deal with problems like this. When the spacecraft’s computer realized how much power it was drawing, it shut down the science instruments to save power for really critical things, like heating fragile subsystems and communicating with engineers back home on Earth, who could help find and fix the problem.

It took a solid three days to get one of the overlapping, power-hungry systems shut down and the science instruments turned back on – but engineers spent a lot of that time waiting. At the moment, Voyager 2 is 18.5 billion km (11.5 billion miles) from Earth (and counting), and even for radio communications at the speed of light, it takes 17 hours for a message to get from Earth to Voyager, and another 17 hours for a message to get from Voyager back to Earth. So every time engineers at NASA sent Voyager a command, like “turn off that extra system now,” it took at least 34 hours to find out if the command worked and whether it fixed the problem…

This is a good opportunity to include an excellent YouTube video I’ve been wanting to share with y’all for a long time. It’s over a year old, but no less mind-boggling.

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