Proud Space Nerds Episode 5: How Do Satellites “Talk” to Each Other and Earth?


– How do we talk to satellites in space? And what role do
communication satellites play in our daily lives? Let’s find out in this episode
of How to Build a Spaceship. Honeywell Aerospace Mission Control. Do you read? – Roger. Reading you loud and
clear, Mission Control. (techno music) – Satellites are an integral
part of our modern lives. From communications to navigation, Earth observation to
space weather monitoring, we interact with Earth-orbiting satellites multiple times a day. There are hundreds of
communication satellites in Earth orbit. Without satellites, a lot of simple things we
take for granted everyday would no longer function. Communication satellites work by receiving signals from Earth. These signals fade on the journey of up
36,000 kilometers in orbit so the satellite has to
amplify the signal on board before transmitting it back to Earth. Multiple Honeywell components play a key role in this process including switches and multiplexers. Can you explain how
satellite switches work? – Well, a satellite switch
changes the direction of energy on a satellite, sort of
like a railway track, moving the train from
one track to another. – And why do satellites need switches? – One of them is to move
information, move data around. For instance, you might
want to have a lot of data at the East Coast in the morning, the West Coast in the
afternoon so you move the beam. Another reason is for redundancy. Things can wear out on the satellite and what the switches will do then is they’ll switch out
another piece of equipment. – So what is a multiplexer or a MUX? – A multiplexer is a piece
of equipment on a satellite that takes the big signal
that comes from the Earth and breaks it down into
smaller chunks called channels. We have the name channels
from the old days when it represented one TV
channel worth of information. Today, it’s not so much TV channel. It could be any sort
of digital information, voice, data, whatever, but what the multiplexer does, it takes a big band,
breaks into little chunks, allows the satellite to
process it, amplify it, and then the MUX puts
it back together again to send it back down to Earth. I’m Jeff Wiesel and a proud space nerd. – What kind of communications
do your satellites provide? – Well, satellites are best
known for broadcasting. A single satellite can reach tens of millions of dishes from geo. Additionally, satellites can be used for point-to-point communication, connecting boats, trains and rural areas. – How big of an area do
the satellites cover? – That depends on the orbit
and the antenna configuration. But to give you an example,
a geostationary satellite can cover one-third of
the Earth’s surface. A satellite in LEO on the
other hand would only cover something like 600 to 1,000
kilometers in diameter. – How do the signals going
to the satellite from Earth not interfere with the
signals coming to Earth from the satellite? – The way the satellites do not interfere with the uplink and the downlink is they’re on different radio frequencies. The uplink is transformed
aboard the satellite and then re-transmitted to the ground. – How do the signals from
satellites differ from the signal that I would have here on
Earth with my cellphone? – They’re remarkably the same. The cell signals actually
form spots on the ground that are about 10 kilometers in diameter. The satellite being much higher in the sky forms much larger spots on the order of 500 to 600 kilometers. I’m Sid Rao and a proud space nerd. – And that’s how we talk
to satellites in space and how they talk back
to us here on Earth. Hailing Frequencies Open. Yeah, you’re gonna wanna
take a right at Pluto. (techno music)

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