Okay kiddo, you know those big machines in space that take pictures of the earth and help us understand things like weather and land use? Those are called Earth observation satellites.
Now, to send those pictures and other data back to us here on Earth, those satellites use something called transmission frequencies. Kind of like when you use your walkie talkie to talk to your friend - you need to be on the same frequency so you can hear each other.
The frequencies Earth observation satellites use are a special kind of radio wave. They are very high frequency, which means they are super energetic and can travel long distances through space without losing their strength.
But because they are so powerful, we need to make sure they don't interfere with other communication signals on Earth. So we have specific frequencies set aside just for Earth observation satellites.
These frequencies are regulated by the international community through something called the Radio Regulations. This helps keep everything organized so that different types of equipment don't accidentally start sending signals on the same frequencies and causing interference.
So in short, Earth observation satellites use special radio waves called transmission frequencies to send us information about the Earth. And we make sure they don't interfere with other types of communication by regulating which frequencies they can use.