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World's Biggest Radio Telescope
June 1964 Radio-Electronics

June 1964 Radio-Electronics

June 1964 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

World's Biggest Radio Telescope, June 1964 Radio-Electronics - RF CafeThe National Science Foundation's 1000-meter Arecibo radio telescope, carved into a Puerto Rico mountain valley, was commissioned on November 1, 1963. Justification in funding the colossal project was partly from the Department of Defense because of a need to characterize the Earth's upper atmosphere. Satellites and looming threats of soon to be developed ICBM traffic were of prime concern. One of the renowned uses of the Arecibo radiotelescope was when Carl Sagan's team transmitted a "we are here" message toward the M13 globular cluster in the constellation of Hercules in 1974. The amount of research and data collected over the ensuing six decades has been invaluable from both communications and astronomical perspectives. Tragically, on November 7, 2020, the dish suffered a catastrophic mechanical failure in the suspension supports, resulting in irreparable damage. Planning on the site's future is ongoing.

World's Biggest Radio Telescope ... What It Is For - What It Will Do ...

By Hugo Gernsback

We recently had the privilege of visiting the Arecibo Ionospheric Observatory (its official name), the giant radio telescope that we pictured on our Feb. 1964 cover and described in technical detail in the article on page 36 of that issue.

Because of its stupendous vastness, its even greater technical complexity, and because of its potentialities as a key for unlocking much of our still unknown universe - almost universally uncomprehended - we should like to say a little more (in simple language) about its raison d'être.

Like the great pyramid of Cheops, whose real purpose was unknown and for thousands of years understood by only a small minority (it was to be the Pharaoh's tomb), the Arecibo Observatory and its purpose is a dark secret for most of the American population. Few have heard about it. Even in Puerto Rico it is a total enigma. It is vaguely known as "a big radar." No one, even among the most intelligent people, knows that the observatory is really the biggest single thing in all of Puerto Rico.

Located 12 miles south of Arecibo in the north of Puerto Rico, some 62 miles from San Juan, the observatory is in an almost perfect wilderness in the hills. It was the brainchild of Professor William E. Gordon of Cornell University who was appointed director of the facility.

Erected at a cost of almost 9 million dollars, the Arecibo Ionospheric Observatory (AIO) was constructed over a period of almost 4 years, under contract with Air Force Cambridge Research Laboratories by Cornell University and the US Army Corps of Engineers.

Its chief physical feature is its 1,500-foot diameter bowl, blasted out of the rock, in a natural depression. It is a spherical cap - not quite a half sphere. It required the removal of 300,000 cubic yards of rock and earth to fashion the bowl in the valley. The lower part of the bowl is completely lined with heavy, mesh wire on metal cables. Total dish surface is about 18.5 acres.

Figures or even photographs mean little in helping us visualize the huge size of this bowl that could hold 403,000 humans standing upright, without undue crowding. Suspended high over the center of the bowl is the 500-ton triangular "feed system" measuring 200 feet on a side. It has a 340-foot crescent-shaped arm which can be rotated horizontally over the bowl. Attached to the arm is a 96-foot "line feed" pointing down to the bowl and positioned 435 feet over it. Its purpose is to steer and reflect incoming as well as outgoing radio waves.

The role of the Observatory is threefold.

1. It will vastly increase our knowledge of the earth's ionosphere, which can be called "the curved electronic mirror in the sky." Composed of electrically conducting ionized gas, it envelops the earth from a distance of 200 miles out to a distance of several thousand miles. Without the ionosphere, much of our broadcasting and radio communication would not be possible.

The Department of Defense believes that better knowledge of our ionosphere would greatly assist it in tracking enemy I.C.B.M.'s.

2. The Observatory's future role of listening in to distant star electronic emissions is vitally important to Radio Astronomy research. Only very recently (1964) have scientists listened in to radio star emissions that originated 10 billion years ago! This knowledge helps us to interpret the age of the universe.

3. A.I.O. now makes it possible to beam more powerful radio and radar signals to the various planets of the solar system with greater precision.

The Observatory can beam the world's strongest radar signals into space - 21 1/2 million watts at peak power. Since A.I.O. opened last November, its scientists have sought to contact the solar system's largest planet, the giant Jupiter 400 million miles distant. So far, however, the experiment has been inconclusive, probably because of that planet's deep, gaseous envelope that could have absorbed the radar energy completely. No reflected signals from Jupiter could be detected at A.I.O. This in no way discourages associate director Dr. G. H. Pettengill, who is an old hand at reflecting radar beams successfully from planets. He was among the first to bounce radio emissions from Venus, when he still was connected with MIT's Millstone Hill radar installation. ("Road to Universe opened", Radio-Electronics, May 1959, page 47.)

Dr. Pettengill will try again with the giant Jupiter this Fall, using either different radio frequencies or different waveforms, and new ways of processing the returned signals.

Right now, Pettengill and his associates must solve one of the most important and pressing space problems: What is the actual consistency of the lunar surface? Late in March, Moscow scientists declared that the moon is deeply covered with meteoric dust, making any landing by humans extra-hazardous. This has been predicted by a number of scientists as well as the present writer for many years.

Pettengill expects that much new information about the lunar surface consistency can be obtained with the A.I.O. radar sometime in the near future. If a deep quicksand-like dust layer actually exists, the NASA scientists who are building the lunar space capsule must alter their design, so that the capsule with its human explorers will not sink out of sight into a sea of impalpable dust.

How does one "listen in" to the world's "biggest ear"? It was K. Jansky, who in Dec. 1931 was the first to discover that radio waves were reaching the earth from some source in space. This in time became the present art of Radio Astronomy, or listening in on the radio emissions of distant stars. Jansky listened in with the usual earphones, because that was the only means we had to hear the distant radio noises in those days.

Nowadays all this has been changed radically. Humans no longer "listen in" directly with their ears to distant stars. At A.I.O. modern data processing equipment now does the task of humans. Here the latest computers with their associated oscilloscopes and accurate time recorders are used.

The equipment records all signals automatically, filtering out unwanted noises. Then the equipment records all signals as well as the exact time on special typewriters.

Inasmuch as the computers can work around the clock, the scientists are free to do other essential work - or sleep. All "listening in" is done automatically by the computers. Next day, or later, the scientists read the recorded data and interpret the results - a long and painstaking job. - H.G.



Posted July 21, 2023

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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

1996 - 2024


Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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