Radio waves, Light we see, ultraviolet, Xrays are all the same thing. We can see light, Xraay machines can see and record x-rays, but instruments on earth can also see the special Radio wave light beacon on the spacecraft from very far away. It's hard to block and doesn't take a lot of energy to transmit compared to a lot of other special types of lights. The light blinks on and off very rapidly. The antannae on earth see it and convert the ons and offs into 1s and 0s. DATA!