Tracy Drain

But, yeah, there are a lot of things that we build into the spacecraft so that they do have smarts to take care of some situations.

They're so far away.

Jupiter is far enough away that a radio signal traveling at the speed of light will take 50, 5-0 minutes to get there and then 5-0 minutes to get back.

And so we can't just joystick the thing.

It has to be able to deal with some circumstances that come up.

And so we have, for every component that the spacecraft really needs to work in order to stay safe, there are usually two.

There are two star trackers that it uses to figure out what its orientation is in space.

There are two inertial measurement units, which is kind of a dead reckoning thing.

If you're walking across a room and you close your eyes and you take 10 steps, the reason you know how much you've moved in space is kind of your own inertial measurement, right?

We have units like that, two of those, and a variety of things like that.

So...

For the spacecraft, it's programmed so that if X happens, do Y. If Z happens, do B. And it can swap components if something's wrong with it.

But it can get itself into situations that are too complicated for it to know what to do.

And so then it'll power off everything it doesn't need, point its antenna at the Earth and go into what we call a safe mode and essentially say, you know, help Earth.

And then after enough time goes by for us to see the signal, we on the ground get to do the mystery game.

Okay, what happened?

Why did that happen?

What can we do about it in order to get the spacecraft back on track?

If you look at an image of the moon, you will notice that it is much smoother than our moon's surface or many of the other moons that are around Jupiter.

And that's one of the clues that scientists had, that something is going on there that is resurfacing the moon on a relatively smooth,