Eli5 – How do satellites tell the time?

Question

A friend of mine told me they measure with nuclear decay to tell time on satellites but I don’t understand what TF that means

In: 7

Answer 1

Not all satellites “tell time” on their own, many just have the time told to them by clocks on the ground. It’s only GPS satellites specifically that track time on their own. They have atomic clocks onboard, but those are the same as atomic clocks on the Earth. Are you asking how atomic clocks in general work?