how sattelites sent to space to take pictures send data back to earth?


I was just reading a book to put my 4 year old to sleep, and there is a part where there is a satellite that took a picture of pluto, considering how far pluto is, how can the satellite send the images back to earth with that distance?

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Strictly speaking, that photo probably did not come from a satellite, but rather a probe on an escape trajectory.

As for how, they get a huge antenna on the probe, point it at a huge antenna (or several) on Earth, pump as much energy as the probe can spare into the signal, and transmit data slowly.

It is fundamentally a radio. Obviously a sophisticated one. The transmitting end on the craft is not super powerful so the signal is fairly weak by the time it arrives to earth but, on the ground, this data is collected using very large radio wave detectors (think large satellite dishes) that can detect weak signals.

Think of it as wi-fi but on a very very large scale.

Radio waves. Wireless communication is just radio waves*. On a basic level, there’s really nothing different between the radio in your car, the wifi you connect to with your phone or computer, and space probes sending data back to Earth. On all cases, it’s just 2 antennas sending radio waves back and forth between each other. The only real difference is the distance. To overcome the distances involved in space flight, you just need really really big, sensitive antennas.


*There are some very niche wireless communication roles that use other means, such as lasers, but 99%+ of wireless communication is radio waves.

The answer to this question depends on the type of satellite used. If the satellite is a deep space probe, then the images can be sent back to Earth using radio waves. Radio waves are electromagnetic waves that can travel through space and can be received by antennas on Earth. If the satellite is a telescope, then the images can be sent back to Earth using optical communication, which involves using lasers to transmit the images.

You know how you can communicate over a noisy line N as in Nancy, S as in Samuel, and so on. You are essentially trading speed for clarity. They do the same when communicating over long distance. The longer the distance the closer the useful signal to the background (*) noise so it’s more noisy. As the noise increases they compensate by slowing down transmission.

(*) You can’t get rid of background noise because it’s produced by the heat of electronics. They cool down electronics in deep space network antennas cryogenically but there is a practical limit how low they can go.