Arecibo Travel Blog› entry 2 of 5 › view all entries
The Arecibo Observatory is located approximately 9 miles south-southwest from Arecibo, Puerto Rico (near the extreme southwestern corner of Arecibo pueblo). It is operated by Cornell University under cooperative agreement with the National Science Foundation. The observatory works as the National Astronomy and Ionosphere Center (NAIC) although both names are officially used to refer to it. NAIC more properly refers to the organization that runs both the observatory and associated offices at Cornell University.
The observatory's 305-m radio telescope is the largest single-aperture telescope (cf. multiple aperture telescope) ever constructed. It carries out three major areas of research: radio astronomy, aeronomy (using both the 305-m telescope and the observatory's lidar facility), and radar astronomy observations of solar system objects.
The telescope is visually distinctive and has been used in the filming of two notable motion pictures: as the villain's antenna in the James Bond movie GoldenEye and as itself in the film Contact. The telescope received additional international recognition in 1999 when it began to collect data for the SETI@home project.
The Arecibo telescope is distinguished by its enormous size: the main collecting dish is 305 m in diameter, constructed inside the depression left by a karst sinkhole.
It is a spherical reflector (as opposed to a parabolic reflector). This form is due to the method used to aim the telescope: the telescope's dish is fixed in place, but the receiver at its focal point is repositioned to intercept signals reflected from different directions by the spherical dish surface. The receiver is located on a 900-ton platform which is suspended 150 m (450 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 construction of the Arecibo telescope was initiated by Professor William E. Gordon of Cornell University, who originally intended to use it for the study of Earth's ionosphere. Originally, a fixed parabolic reflector was envisioned, pointing in a fixed direction with a 150 m (500 ft) tower to hold equipment at the focus.
The two brothers thought of a more efficient way to suspend the feed, and finally designed the cable suspension system that was used in final construction. U.S. Patent office granted Helias Doundoulakis patent No. 3,273,156 on Sept. 13, 1966 with the title “Radio Telescope having a scanning feed supported by a cable suspension over a stationary reflector”.
Construction began in the summer of 1960, with the official opening taking place on November 1, 1963. As the primary dish is spherical, its focus is along a line rather than at a single point (as would be the case for a parabolic reflector), thus complicated 'line feeds' had to be used to carry out observations.
The telescope has undergone several significant upgrades over its lifespan. The first major upgrade was in 1974 when a high precision surface was added for the current reflector. In 1997 a Gregorian reflector system was installed, incorporating secondary and tertiary reflectors to focus the radio waves at a single point. This allowed the installation of a suite of receivers, covering the whole 1-10 GHz range, that could be easily moved onto the focal point, giving Arecibo a flexibility it had not previously possessed. At the same time a ground screen was installed around the perimeter to prevent receivers from sensing the ground (which, due to its temperature, would make observations less sensitive) and a more powerful transmitter was installed.
The Arecibo telescope has made many significant scientific discoveries. On 7 April 1964, shortly after its inauguration, Gordon H. Pettengill's team used it to determine that the rotation rate of Mercury was not 88 days, as previously thought, but only 59 days. In 1968, the discovery of the periodicity of the Crab Pulsar (33 ms) by Lovelace and others provided the first solid evidence that neutron stars exist in the Universe. In 1974 Hulse and Taylor discovered the first binary pulsar PSR B1913+16, for which they were later awarded the Nobel Prize in Physics. In 1982, the first millisecond pulsar, PSR J1937+21, was discovered by Don Backer, Shri Kulkarni and others.
In August 1989, the observatory directly imaged an asteroid for the first time in history: asteroid 4769 Castalia. The following year, Polish astronomer Aleksander Wolszczan made the discovery of pulsar PSR B1257+12, which later led him to discover its three orbiting planets (and a possible comet). These were the first extra-solar planets ever discovered. In 1994, John Harmon used the Arecibo radio telescope to map the distribution of ice in the poles of Mercury.