Arecibo radio observatory, as seen by the Ikonos satellite. This radio telescope (centre) is situated in a natural crater in the mountains of Puerto Rico. The larger circle is a 300 metre fixed reflecting dish and suspended 130 metres above is a 90 tonne dome housing a gregorian subreflector system installed in 1997. The Arecibo telescope can send and receive signals to examine planets and asteroids, and also analyse Earth's upper atmosphere. Ikonos was the first commercial satellite to collect data at one-metre resolution. Image taken on 7 January 2002.