Radome of Arecibo telescope. Night view of the 90- tonne dome housing the new gregorian subreflector system installed in 1997 for the Arecibo radio telescope. This largest radio telescope in the world is situated in a natural crater in the mountains of Puerto Rico. The dome with its two mirror subreflector system is suspended 130 metres above the fixed dish. It can send and receive signals to examine planets and asteroids, and also analyse Earth's upper atmosphere. To scan the sky the dome is steered above the 305 metre dish. The Arecibo upgrade includes a 16m high buffer screen around the dish and a new radar transmitter that increases Arecibo's power by 20 times.