I still cannot believe NASA managed to re-establish a connection with Voyager 1.
That scene from The Martian where JPL had a hardware copy of Pathfinder on Earth? That’s not apocryphal. NASA keeps a lot of engineering models around for a variety of purposes including this sort of hardware troubleshooting.
It’s a practice they started after Voyager. They shot that patch off into space based off of old documentation, blueprints, and internal memos.
To me, the physics of the situation makes this all the more impressive.
Voyager has a 23 watt radio. That's about 10x as much power as a cell phone's radio, but it's still small. Voyager is so far away it takes 22.5 hours for the signal to get to earth traveling at light speed. This is a radio beam, not a laser, but it's extraordinarily tight beam for a radio, with the focus only 0.5 degrees wide, but that means it's still 1000x wider than the earth when it arrives. It's being received by some of the biggest antennas ever made, but they're still only 70m wide, so each one only receives a tiny fraction of the power the power transmitted. So, they're decoding a signal that's 10^-18 watts.
So, not only are you debugging a system created half a century ago without being able to see or touch it, you're doing it with a 2-day delay to see what your changes do, and using the most absurdly powerful radios just to send signals.
The computer side of things is also even more impressive than this makes it sound. A memory chip failed. On Earth, you'd probably try to figure that out by physically looking at the hardware, and then probing it with a multimeter or an oscilloscope or something. They couldn't do that. They had to debug it by watching the program as it ran and as it tried to use this faulty memory chip and failed in interesting ways. They could interact with it, but only on a 2 day delay. They also had to know that any wrong move and the little control they had over it could fail and it would be fully dead.
So, a malfunctioning computer that you can only interact with at 40 bits per second, that takes 2 full days between every send and receive, that has flaky hardware and was designed more than 50 years ago.
It's hard to explain how significant the Voyager 1 probe is in terms of human history. Scientists knew as they were building it that they were making something that would have a significant impact on humanity. It's the first man made object to leave the heliosphere and properly enter the interstellar medium, and this was always just a secondary goal of the probe. It was primarily intended to explore the gas giants, especially the Jovian lunar system. It did its job perfectly and gave us so many scientific discoveries just within our solar system.
And I think there's something sobering about the image of it going on a long, endless road trip into the galactic ether with no destination. It's a pretty amazing way to retire. The fact that even today we get scientific data from Voyager, that so far away we can still communicate with it and control it, is an unbelievable achievement of human ingenuity and scientific progress. If you've never seen the image the Pale Blue Dot you should see it. That linked picture is a revised version of the image made by Nasa and released in 2020. It's part of a group of the last pictures ever taken by Voyager 1 on February 14th 1990, a picture of Earth from 6 billion kilometers away. It's one of my favorite pictures, and it kinda blows my mind every time I see it.
I was already impressed when they managed to diagnose a single bit flip a few years ago.
Keep in mind too these guys are writing and reading in like assembly or some precursor to it.
I can only imagine the number of checks and rechecks they probably go through before they press the "send" button. Especially now.
This is nothing like my loosey goosey programming where I just hit compile or download and just wait to see if my change works the way I expect...
Rejected : please comment your changes
When I hear what they did, I was blown away. A 50 year old computer (that was probably designed a decade before launching) and the geniuses that built that put in the facility to completely reprogram it a light-day away.
Great documentary on the Voyager team: It's quieter in the twilight
Fuck it, we'll fix it live
It reminds me that there are still very intelligent and talented people within our ranks. A nice breath of fresh air.
And the IT support service can't even fix a computer problem of an customer 20 km away.
Imagine being the guy who crashed the probe working with this guy.
