How the Arecibo telescope works

The Arecibo telescope consists of a 305m fixed reflecting surface, made up of 40,000 individual panels, suspended in a natural limestone sinkhole in northwestern Puerto Rico. Incoming rays are reflected back from the surface to two additional reflectors located 450 feet above on the "platform", a 500 ton structure supported by cables from three towers.

The secondary and tertiary reflectors are located within a dome. The telescope can be "steered" by moving the dome up and down along the curved arm which can also be rotated.

The dome is designed to shield the smaller reflectors from weather and from harmful radio frequency interference caused by local man-made radio transmissions.

Incoming rays are reflected first off the fixed reflector on the bottom of the sinkhole are reflected up to the secondary and then to the tertiary mirror. They finally come to a point focus at the receiver room. Feeds attached to different receivers, covering different frequency (wavelength) ranges, can be moved into position at the focal point because they sit on a rotating turntable in the receiver room.