But right now, it is moving towards us.

Relatively speaking.

This is the control room for NASA's Deep Space Network

and the scientists here still listen for the signals that Voyager is sending.

Deep Space Network is a collection of antennas around the world

that we use for tracking deep space missions.

We provide commands to the spacecraft, so y'know, “turn left at the next corner”

kinds of things, right?

Little more complicated than that.

Turn the instrument on, turn the instrument off, software updates.

The most important reason for sending the thing out there

is to get the science data back, and so the instruments are taking

visible pictures, infrared pictures, measuring particles in the case of Voyager.

We need to get that data back down and distribute it to the scientists.

The Deep Space Network's three stations cover the whole sky.

Any mission more than 30,000 km away from Earth

is visible to at least one station all the time.

Geostationary orbit, where we keep most of our communication satellites,

is further away than that.

We really have three complexes around the world:

Madrid in Spain, Goldstone here in California, and the Canberra complex in Australia.

We typically don't track things that go over the pole because

the types of missions that we deal with are in deep space

and tend to be in the ecliptic.

If you look at the solar system, where the Sun is,

and where the planets are that are revolving around the sun,

they all tend to be more or less in one plane.

That launch along the plane of the solar system, along the ecliptic,

is the reason that Voyager is getting closer to Earth right now.

Yes, Voyager is always moving away from the sun, but sometimes the Earth's orbit

means that our planet is travelling in roughly the same direction only faster.

So we're catching up.

Of course, we'll get pulled back in our elliptical orbit

so it'll even out when we go back the other way.

In terms of checking in with spacecraft, I think with Voyager for example,

we probably downlink from them almost every day.

Because again, there's a lot of good data, but when you are only coming at 160 bits per second,

it takes a long time to get that data off the spacecraft.

The signal has to be, in some sense, above the noise level for us to see it.

You first of all just try to filter the noise out as much as possible,

just from a frequency standpoint.

My signal occupies this much spectrum in frequency,

I don't want to let in any more noise than what's there.

I want to correlate the signal that's coming down

with what I think that signal looks like.

You got to take advantage of what you know about the signal

and use those characteristics as best you can to extract it from the noise.

Voyager 1 is carrying radioisotope thermoelectric generators, RTGs.

It's powered by radioactive decay.

And there's enough power there to last until around 2025.

After that, the craft will go dark, carrying a message forward into interstellar space

for… well, we don't know where, or when, or even who.

If there was enough light being bounced off of it,

you might be able to see it with a telescope, but it's so far away, and so dim,

without a radio signal coming from Voyager at all,

there's no way that we, the DSN, would be tracking it.

And so I think that's pretty much the end, once it goes dark.

Thank you very much to all the team at NASA, the Jet Propulsion Laboratory,

and here at the Deep Space Network.

Pull down the description for more about them, and about their missions.