Cosmos Up: Three sites were selected to receive data from space, one in California, one in Spain and another in Australia — 120° apart so together they could see the whole sky 24 hours a day.
'On each site, an array of massive satellite dishes ranging from 24 to 70 meters in diameter were constructed.
'This is the most powerful and sensitive communication system in the world. The 70-meter antenna is able to hear quote “a whisper from a billion kilometers” away. Now, because of launch weight restrictions and power limits, broadcast equipment on spacecrafts has to be light, so engineers are forced to use relatively low-powered transmitters — like, 0 watts (that’s way less than the average incandescent light bulb). And it gets weaker as it travels through space.
'By the time the signal reaches the dish, it can be “20-billion times less than the power needed to power a digital watch.” When a signal wave hits the dish, it’s reflected to a highly sensitive receiver at the center — and put through a crazy powerful amplifier. The amplifiers are cooled to near absolute zero, to minimize electrical interference from the equipment itself.
'So, because of their position on the globe, no matter where the satellites are, at least one DSN dish will be able to hear the broadcast. Signals from near-Earth missions are strong, and can be picked up relatively easily. For deep-space missions, it’s a bit harder.'