How do space probes transmit data back to Earth across vast distances?
In: Planetary Science
There’s a few ways first they use a frequency that has a long transmission wavelength. For example AM radio has a wavelength that measures about 2 meters in length.
They also use high power transmitter the more power you put into the transmission the longer it can go.
Here on Earth with with all the interference that we have a long wire antenna can transmit a hundred Watts across the world. NASA talks to Mars with about 250 Watts. The Voyager probe has a 1,000 Watts transmitter and it doesn’t have to deal with any interference.
The other thing is it sends all data in a more simplified form slow but long transmissions. So a simple status update could take 2 hours to transmit.
Add to that it sends the same signal at minimum of three times. The reason for that each listening station could hear a different part of the message. Or have errors due to interference and sending the transmission three times those errors don’t line up so you will get at least one clean signal out of it.
The other way is on the receiving end. Having multiple stations listening for that satellite all over the world and transmitting to that satellite from all over the world means that any signal that is received can be picked up in chunks and then processed so that the signal becomes clear and understandable.
An amateur radio we do this. Where we will ask for information to be sent tripled that way we get a clear reception of every part of the message since atmospheric and other interference won’t show up at the exact same space every time.
And just kind of put the point home, think of these radio communications like light. In the old days ships would communicate by flashing Morse code a simple on and off signal across the water. Now when the ship was communicating this way to shore it was easy to understand because there’s only one signal of that style and the person on shore was looking for that specific signal. Now if you did the same thing communicating using flashlights in a city it would be harder to understand because of all the interference from the other lights.
In short using radio waves and multiple transmissions of the same signal on the transmitter side. And multiple receivers on the planet side looking for a very specific frequency in a very specific region of space. All the other interference kind of goes away cuz it’s filtered out. Leaving just the original signal with errors which get corrected by the multiple transmissions.
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