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Across the world’s space agencies, there are
dozens of spacecraft currently on missions beyond Earth.
But space is big. Really big.
And the farther away the craft is, the weaker its signal is when we receive it.
Also, any signal we want to send from Earth gets weaker, too.
So in order to talk to these far-flung extensions of humanity,
we have a special network of radio dishes.
It’s called the Deep Space Network, or DSN for short.
And it’s not just a messenger. It does science, too!
While it’s operated out of NASA’s Jet Propulsion Laboratory, the DSN’s radio antennas
are at three facilities around the globe, one in Australia, one in Spain, and one in California.
These bases are roughly the same distance apart,
to make sure that any spacecraft can stay in constant communication, even as Earth rotates.
At the beginning of 1958, the forerunner to the DSN was created.
JPL deployed portable radio tracking stations in California, Nigeria, and Singapore
to help pilot Explorer 1, the first manmade American object to fly around the planet.
The actual DSN was established in December 1963,
but its various radio antennas were built in later years, and upgraded over the decades.
During those decades, it helped steer the first satellite to enter another planet’s orbit,
land the first lander on an asteroid,
and show the entire world Neil Armstrong’s first steps on the Moon.
You know, no big deal.
To talk to spacecraft, the DSN has three groups of different sized antennas.
The largest measure 70 meters across, and are how we communicate with the most distant
objects, like Voyager 1, which, by some definitions, is past where the solar system ends.
Why so big? Well, by the time Voyager’s signal gets back to Earth,
it’s 20 billion times weaker than what’s used to power a digital watch.
And because the signal is so weak, the dish can’t have any deformations in it.
So that 3,850 square meter surface is shaped perfectly to within a single centimeter.
Each site also has at least one antenna that’s 34 meters in diameter,
and a single 26-meter antenna used to track Earth-orbiting spacecraft.
All these antennas are equipped with amplifiers to hear faint signals.
But that also means any background noise, including radio static emitted by basically
every object in the universe, gets amplified, too.
So astronomers encode the signals in such a way
that they can distinguish satellite signals from noise.
There’s also the trouble of the equipment itself producing noise
in the form of infrared radiation, AKA heat.
So the amplifiers are designed to work at really cool temperatures, within a few degrees
above absolute zero, so the heat signal doesn’t overwhelm the sensors.
Another way the DSN can amplify communication is
by using the multiple antennas to collect a signal from the same source.
This is called arraying, and it works really well for radio waves because
the wavelengths are so long.
So you don’t have to worry as much about things like interference from the atmosphere.
All together, this means the DSN is even capable of finding and tracking “lost” spacecraft,
ones that aren’t sending out a signal anymore, just by acting like a big radar gun.
In fact, it managed to track down India’s Chandrayaan-1, which is orbiting the moon!
But the DSN isn’t just for tracking and talking to spacecraft,
even though it’s pretty dang good at it.
Every once in a while, it gets in on some science, too!
A lot of times, it works with spacecraft.
For example, by detecting changes in the signals it receives,
it can help determine the composition of whatever the spacecraft is orbiting.
Back during the Cassini mission, the DSN helped find the first evidence of
a liquid water ocean underneath the surface of Enceladus.
As Cassini flew past Enceladus, different regions had different gravitational pulls
on the satellite, because they were made of different stuff.
That changed Cassini’s velocity,
which caused the frequency it transmitted to be shifted just a little bit.
The DSN picked those changes up, and allowed astronomers to figure out
that there had to be water underneath the surface.
And speaking of Cassini, the DSN was also used to study what Saturn’s rings are made of.
Back in 2005, Cassini conducted its first radio occultation observations.
Basically, it sent a radio signal from behind the rings, to Earth.
The denser the ring, the weaker the signal the DSN received.
And by using three different radio frequencies at the same time,
which were each affected differently based on the rings’ particle sizes,
astronomers could get both density and composition profiles.
But the DSN can work alone, too.
It can directly image objects, like asteroids, by bouncing signals off them,
a technique called radar astronomy.
And it’s even been used to test predictions that come out of general relativity.
For instance, it sent radio signals to the Viking spacecraft while Mars and
Earth were basically on opposite sides of the Sun.
And that showed that light passing near a massive body takes longer to travel,
which is gravitational time dilation!
So here’s to you, Deep Space Network.
If it weren’t for you, we’d know so much less about the solar system.
Thanks for watching this episode of SciShow Space!
If you want to learn more about space history related to the DSN,
check out our video about how the US launched Explorer 1 in the late 1950s.
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