Arecibo Observatory - General Information

General Information

The main collecting dish is 305 m (1,000 ft) in diameter, constructed inside the depression left by a karst sinkhole. It contains the largest curved focusing dish on Earth, giving Arecibo the largest electromagnetic-wave-gathering capacity. The dish surface is made of 38,778 perforated aluminum panels, each measuring about 3 by 6 feet (1 by 2 m), supported by a mesh of steel cables.

The telescope has three radar transmitters, with effective isotropic radiated powers of 20 TW at 2380 MHz, 2.5 TW (pulse peak) at 430 MHz, and 300 MW at 47 MHz.

The telescope is a spherical reflector, not a parabolic reflector. To aim the telescope, the receiver is moved to intercept signals reflected from different directions by the spherical dish surface. A parabolic mirror would induce a varying astigmatism when the receiver is in different positions off the focal point, but the error of a spherical mirror is the same in every direction.

The receiver is located on a 900-ton platform which is suspended 150 m (500 ft) in the air above the dish by 18 cables running from three reinforced concrete towers, one of which is 110 m (365 ft) high and the other two of which are 80 m (265 ft) high (the tops of the three towers are at the same elevation). The platform has a 93-meter-long rotating bow-shaped track called the azimuth arm on which receiving antennas, secondary and tertiary reflectors are mounted. This allows the telescope to observe any region of the sky within a forty-degree cone of visibility about the local zenith (between −1 and 38 degrees of declination). Puerto Rico's location near the equator allows Arecibo to view all of the planets in the Solar System, though the round trip light time to objects beyond Saturn is longer than the time the telescope can track it, preventing radar observations of more distant objects.