The World of Radio Astronomy

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 Photos courtesy of Alfred Wasser  
a member of  The SETI League        http://www.setileague.org/.)           
 
 
  The VLA consists of 27 of these 25
     meter diameter dishes, each             
   weighing 230 tons                            

26 Meter Radio Telescope


NRAO Tucson


Lovell Telescope

Green Bank Telescope


GNRT Antenna


Fort Davis Texas


Owens Valley, California


North Valley, Iowa


140 Foot Antenna


Los Alamos, New Mexico


Harvard SETI Antenna

 
The Cambridge Low-Frequency  syn- thesis Telescope (CLFST) is an east-west aperture synthesis  telescope currently operating  at 151 MHz. It consists of 60 tracking yagis on a 4.6 km baseline, giving 776 simultaneous baselines. These provide a resolution of 70×70 cosec(declination) arcsec², with a sensitivity of about 30 to 50 mJy/beam, and a field of view of about 9°×9°.

  But there remains a significant community of interest in the search for extra-terrestial life. Absent govenrment support and financing it has been necessary to find new approaches to this search. One such effort is that of  SETI@home which now has now exceeded one million users.
  The approach is beautiful in its simplicity and ingenius in its concept and implementation. The basic idea is to take advantage of the world's installed base of personal computers many of which spend more time in "screen-saver" mode than in use.
  All that was required was a source of signal data, in this case Arecibo and access to these idle machines. The internet provided the access and a "screen-saver" was created that would download the data process it when the machine is not in use and then upload the processed data and download more raw data. 
  If you haven't yet signed up for this project you ought to give it serious consideration.
  Simply download the program from SETI@home and when you machine is idle the screen saver will automatically begin processing data from Arecibo. You maybe the first to discover a signal from our friends the aliens.

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The Arecibo "dish",  a spherical (not parabolic) reflector, is 1000 feet in diameter, 167 feet deep, and covers an area of about twenty acres. The surface is made of almost 40,000 perforated aluminum panels, each measuring about 3 x 6 ft, supported by a network of steel cables. Arecibo Observatory is the largest curved focusing antenna on the planet, and therefore the world's most sensitive radio telescope

  As of August 14, 1999, some 52225.26 years of computer time as been made available by volunteers such as yourself.
  This represents some 3.201879e⁺¹⁹ floating point operations. Two hundred twenty four countries are participating through out the world.



  The Arecibo radio telescope, with its 90-ton, 86-foot diameter dome attached to the end of the 304-feet moveable azimuth arm has sufficient sensitivity and power to observe the farthest reaches of the universe, including pulsars, quasars and other exotic objects, the solar system and the Earth's own upper atmosphere. It is currently the world's largest, most powerful and most sensitive radio telescope.

 
        Arecibo's Suspended Platform

  Suspended 450 feet above the reflector is the 900 ton platform. Similar in design to a bridge, it hangs in midair on eighteen cables, which are strung from three reinforced concrete towers. Another system of three pairs of cables runs from each corner of the platform to large concrete blocks under the reflector. They are attached to giant jacks which allow adjustment of the height of each corner with millimeter precision.
  Just below the triangular frame of the upper platform is a circular track on which the azimuth arm turns. The azimuth arm is a bow shaped structure 328 feet long. The curved part of the arm is another track, on which a carriage house on one side and the gregorian dome (installed in 1996) on the other side can be positioned anywhere up to twenty degrees from the vertical. Hanging below the carriage house are various linear antennas each tuned to a narrow band of frequencies.
  The antennas point downward and are designed specially for the Arecibo spherical reflector. A total of 26 electric motors control the platform. These motors drive the azimuth and the gregorian dome and carriage house to any position with millimeter precision.
  Scientists were surprised soon after the facility was first built 34 years ago to find that the rotation rate of Mercury was not what they had thought. They were also surprised in 1974 to find binary pulsars and in 1991 to find planets around a pulsar. Scientists also found ice on the polar caps of Mercury.
  William Gordon, former Cornell professor of electrical engineering, conceived of the idea of the Arecibo Observatory and recognized the potential for a giant dish in a sinkhole in the karst hills of what formerly a coffee plantation in northeast Puerto Rico, just south of the town of Arecibo.
  Joseph Taylor of Princeton University, won the Nobel Prize in 1993 for co-discovering, in 1974, the first binary pulsar using Arecibo.
  Arecibo was used to first measure the rotation rate of a pulsar associated with a supernova explosion; first measure the slowing down of a pulsar; discover the first binary pulsar, discover a millisecond pulsar, an eclipsing pulsar, discover the first mass of a neutron star, etc.
  Since Arecibo is the largest curved focusing antenna on the planet, it is also the world's most sensitive radio telescope
  With your help Arecibo could end the search for the first extra-terrestrial.

         The Big Bang?   
   

In 1963 Bell Laboratories assigned Arno Penzias and Robert Wilson the task of tracing the radio noise that was interfering with the development of communication satellites. Penzias and Wilson discovered that no matter where the antenna was pointed there was always non-zero noise strength, even where the sky was visibly empty. A simple solution would have been to reset their receivers to zero, but they persisted in tracing the source. This major discovery made by Penzias and Wilson was the cosmic background radiation and the strongest evidence for the big bang. Penzias and Wilson won the Nobel Prize in physics for their discovery in 1978. The image to the left shows Penzias and Wilson with their 6m horn antenna (Photo courtesy of Lucent Technologies, Bell Labs Innovation). The horn shape was used because the field of view remains unobstructed allowing for a precise measurement of the effective collecting area of the antenna.