Arecibo subreflector system. View of the 90-tonne dome housing the new gregorian subreflector system installed in 1997 for the Arecibo radio telescope. Note the people at upper right. This largest radio telescope in the world is situated in a natural crater in the mountains of Puerto Rico. The new subreflector system with two mirrors is suspended 130 metres above the fixed dish. It can send and receive signals to examine planets & asteroids, & also analyse Earth's upper atmosphere. To scan the sky the dome is steered above the 305m 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.