The Arecibo Radio-Radar Observatory in Puerto Rico is facing a significant reduction in funding over the next 3 or 4 years. Originally (1) it was intended only for ionospheric research, mainly so the military could predict frequencies and paths for long range communications. It was therefore initially under the control of the U. S. Department of Defense. Through a number of innovations before and after operation began in November 1963, it has become a general purpose radio-radar observatory especially suited to planetary radar work. The transmitter furnishes one megawatt. The receivers are cooled with liquid helium. One of the first innovations included in the original design was the rotatable azimuth arm below the 900 ton platform. Antennas and later the Gregorian dome can move along the length of the arm to provide steering up to 20 degrees from vertical. The original ionospheric research required only vertical aiming.
In 1965 Arecibo established the rotation rate of Mercury at 59 days. Previously it was thought to present the same side to the Sun with an 88 day rotation and 88 day orbit. In 1968-69 radio pulses from the Crab Nebula discovered at Green Bank (WV, US) were confirmed and more precisely located by Arecibo. In 1969 the National Science Foundation assumed control from the DoD. However ionospheric research has continued as a mission element throughout the history of the observatory. In 1974 a new reflector surface and the planetary radar were installed. From 1974 to the present many observations of asteroids, comets, and planets and extra-solar system objects have been made. In 1996 the Gregorian dome was installed, which allowed correction for aberration of the spherical main reflector.
Some of the other large radio telescopes now in service (2) are: The RATAN-600 in Russia, Jodrell Bank in the U. K., and Green Bank Telescope in WV, U. S. The 576 meter RATAN-600 is a conical shaped structure that is fixed. Limited steering is provided by individual movable panels. The 76 meter Jodrell Bank and 100 meter Green Bank Telescope cover much lower angles than Arecibo, but have much smaller aperture areas also. The Arecibo primary perimeter diameter is 305 meters.
The NSF may be premature in reducing funding for Arecibo if no other similar planetary and Near Earth Object radar is available to replace it. Professional staff can not be expected to stay with a project doomed to be de-funded. I wrote to Congress to ask that they maintain Arecibo funding. You may wish to do the same. I did not mention SETI work (which is always "piggy-backed" with other principal research) because that can be done elsewhere and because many members of Congress have a very negative attitude towards SETI. Instead I emphasized the need for continued surveillance of (low probability, but deadly on collision) NEOs and the need to keep the finest planetary radar system in operation.
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this page last updated 2 August 2008
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