Thanks to NordVPN for sponsoring today’s video. In early May 2022, Voyager 1’s signal went… strange.
The spacecraft Voyager 1 is tasked with exploring the areas beyond our solar system’s planets. It’s
currently 24 billion km out, about 6 and a half times further than the distance between the Sun
and Pluto. Conditions are harsh in interstellar space, as outside the Sun’s protective magnetic
field you are constantly bombarded by cosmic rays and interstellar radiation. It is the furthest out
that any human spacecraft has ever gone. Although it’s over 45 years old now,
and its power supplies are dwindling, Voyager 1 has been consistently providing fascinating
data about cosmic rays, magnetic fields, and other features of the interstellar medium.
So it was strange when one day, the signals coming from Voyager 1 went… weird.
I’m Alex McColgan, and you are watching Astrum. Although at the time NASA scientists scrambled to
figure out what was going wrong with Voyager 1, it took them months to find out the answer. And there
is still some mystery to what happened. Let’s see those events through their eyes, as we ask:
Can you solve the mystery of Voyager 1? Imagine you are a NASA scientist. You arrive at your
computer for the day, and begin looking through the Voyager 1 telemetry data. Voyager 1 sends
back status updates about its systems, letting you know whether everything is functioning normally.
It takes 22 hours now for a signal to reach Earth from Voyager 1, so communication is a little slow
between you and the craft you’re overseeing. Currently, it is more like sending letters
than texts. However, today, something is wrong. The information it has sent you is gobbledegook.
Instead of precise data explaining exactly what Voyager 1’s thrusters are doing, and
what orientation it believes itself to be at, you get long strings of 0’s, or 377’s. The information
does not make sense. It suggests that Voyager is doing things and pointing directions that cannot
be. You quickly check your computer again – yes, you did just receive a signal from Voyager 1. So,
its antenna must be pointing towards you, the same as it always has. It cannot be pointing in
the strange directions it is claiming, or you would not be getting a signal at all.
And not only are you receiving the signal, but it’s at the exact same strength too,
so it has definitely not changed its direction. And, ping, onto your computer
comes Voyager 1’s latest science data. Strangely enough, this is all normal.
While over the years Voyager 1 has had to turn off 5 of its 11 pieces of scientific equipment - and
a further 2 have stopped working due to general degradation - the remaining 4 continue to take
readings about the interstellar medium, magnetic fields and cosmic rays. Nothing here is garbled
in any way. You check its other systems. Voyager 1’s power supplies are a little low, but that’s to
be expected. The plutonium oxide that fills its 3 generators have a half-life of 87 years, but
Voyager 1 has been travelling for 45 now. It is no wonder the efficiency has started to decline.
In fact, the experts believe that Voyager 1 will not last past 2025. But that is some time
away. It does not explain what is happening now. After checking its other systems, it is
just one that is behaving strangely. The AACS – the Attitude Articulation and Control System.
This computer is one of 3 on Voyager 1, and its job is to make sure the spacecraft’s large,
3m antennae continues to point towards Earth. This AACS has stopped sending coherent data.
You lean back, puzzled. The situation is not as bad as you might have thought, but it is
troubling. It’s kind of like receiving post from a postman who says hello to you every morning,
only for some reason he starts speaking another language one day. The packages he delivers are
still the same, and they’ve arrived at the same address. It’s just the words the man speaks make
no sense to you anymore. To further compound the strangeness, Voyager 1 doesn’t think that
anything is wrong with it at all. The spacecraft comes equipped with emergency “safe mode” settings
that it can go into if it detects that anything is not working the way it ought to be. Essentially,
these involve it powering down until scientists can figure out what’s wrong with it. And these
have not activated. So Voyager 1 believes that all its systems are working the way they should be.
The data is given, the scene is set. This was the question that NASA engineers faced in mid-2022.
A single fault like this might not seem like a big deal, but it hints at something potentially
going wrong with further systems. And if that is true, it might spell an end to the whole mission.
Voyager 1 is by now 23.8 billion km away from you. Your solution will have to be made via deduction,
alongside careful, 22-hour-each-way questions and answers with the faulty spacecraft.
By evaluating the rest of the systems and finding them normal, you can rule out some of the more
unusual explanations. No, this probably is not the work of aliens trying to mess with you.
Although Voyager 1 carries with it a golden disk containing detailed information about the human
race - including images of human biology, the sounds of nature, musical symphonies,
and mathematical equations, on the off chance that it does bump into any aliens who would like
to know about us – it seems that this would be a strange way for aliens to communicate with us.
And no, the laws of physics have probably not broken down. Voyager 1 has not entered a wormhole
that is skewing where it thinks it is while still somehow getting the signal back to you.
Given that the scientific data all appears to be providing normal readouts, it’s much more
likely that the problem lies with the AACS itself. For four months, scientists and engineers gently
prod and examine Voyager 1, testing theory after theory and trying to come up with a solution that
fixes things without causing any further damage in the process. They could just switch over to
a backup system. It would not be the first time they’d started using a new computer on Voyager
1 after the old one stopped working. Voyager 1 is built with redundancies; this isn’t even the first
AACS computer that’s been used – a previous one became defective a while ago. They also
contemplate just leaving things be. After all – the science data is still coming in. Would
it be the end of the world if Voyager 1 simply carried on speaking garbled messages? Perhaps
this could simply be the new normal… except it implies that a deeper problem is being overlooked.
Can you figure out what was going wrong? Feel free to have a guess in the comments.
However, from just the information in this video, it would be very impressive if you could.
It turns out that in the intense, radiation-filled environment of interstellar space, something had
made Voyager decide to start using that older, broken AACS computer to send data back to Earth.
Because of the faults in this computer, the data had become corrupted, resulting in the strange
numbers. So actually, in this case the fix was easy. All NASA had to do to fix it was to ask
Voyager to start using the right computer again. Once Voyager 1 did that, the problem was resolved.
On this occasion, it was an easy fix. But next time it might not be.
Voyager 1 is an old ship, now. As it continues to travel through interstellar space, it may
encounter more and more faults. And there is still a lingering mystery; why did it start using
the old, broken computer? At the time of writing this script, NASA still is not sure of the answer.
Unfortunately, some of the systems on Voyager are so old now that the people who designed them have
long since retired. Perhaps this is one mystery that will never fully be solved. I hope not,
though. I hope Voyager 1 will travel further and push the final frontier as far as it can go.
And I also hope you enjoyed this format. To me, science is all about solving mysteries.
And in order to tackle the larger questions of how the universe works, lots of smaller riddles
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