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Ohio Historical Society
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Dedication Ceremony
November 5, 2000

Brochure: A History of the OSU Radio Observatory


Radio Astronomy at the Ohio State University

History of the OSU Radio Observatory
And

BIG EAR

Ohio State University Radio Observatory, Columbus, Ohio

By Jerry R. Ehman

The story of OSURO is inextricably tied to its founder and Director, Dr. John D. Kraus. Before he founded OSURO, he achieved an impressive list of accomplishments. As a youth, he built a radio from a coil of wire, a galena crystal with a fine wire ("cat whisker") and a pair of earphones; he spent many hours fascinated as he listened to AM radio stations across the country. He also set up a telephone and a telegraph system between his house and the houses of some friends.

He learned Morse code and became a ham radio operator. His first call letters were 8AFJ; later, he requested and received the now famous call letters W8JK. Besides his interest in physics and radio as a youth, he also became interested in aeronautics. He decided to pursue a major in physics at the University of Michigan, although he kept up his interest in flying by joining the glider club there. He continued at the University of Michigan and obtained his Ph.D. degree in physics. His dissertation topic involved the study of ultra-short radio waves (specifically with wavelengths of about 5 meters, which were considered ultrashort at that time.

After obtaining his doctorate in 1933 he spent some time in Europe. He began his professional career on a project in the University of Michigan's Physics Department to reduce the compressor noise in refrigerators. While there he helped construct and perform research with their cyclotron ("atom smasher"). In November 1940 he was hired by the Naval Ordnance Laboratory where he worked on a means to protect warships from magnetic mines ("degaussing") and helped develop the earliest "walkie-talkies" using a wavelength of 1 meter. In 1943 he went to the Radio Research Laboratory where he worked on radar counter-measures (including locating and jamming radars), and, after the end of World War II, he helped write a book on the developments at the lab.

In early 1946, John Kraus accepted a faculty position in the Department of Electrical Engineering at the Ohio State University, and began by teaching courses in electromagnetics, transmission lines and waveguides, and antennas. Later, he taught courses in radio astronomy. As an offshoot of teaching, he has written several books. Some of them are: "Electromagnetics", "Antennas", "Radio Astronomy", "Big Ear" (and "Big Ear Two"), and "Our Cosmic Universe"; all of these have been through multiple editions. In addition, he has published hundreds of articles.

John Kraus used various kinds of antennas including several he invented himself. He invented: the "flat-top beam" (often given the name "W8JK beam" or "8JK beam" by other hams); several forms of the corner reflector; and the cylindrical helix.

Kraus' early research at OSU dealt mostly with the helix antenna and the development of a working radio telescope. His first radio telescope antenna was a tiltable flat framework 6 meters long (horizontally) by 4 meters in vertical slant height covered with a coarse mesh. Mounted to the mesh initially were 24 dipoles. However, these dipoles were too hard to adjust, so an array of 6 helices of 11-turns each were used instead; this array worked well. A newspaper reporter, who wrote an article about this radio telescope, referred to it as a "big ear". That terminology was applied consistently to a later and much larger OSU radio telescope.

The one section of 6 helices was expanded to 8 sections (48 helices), and later, by expanding the vertical slant height to 7 meters, 96 helices were obtained; this telescope was located on the west campus of OSU. Observing in a frequency band around 250 MHz, most of the observable radio sky was mapped and converted to a photograph-like display that received much praise worldwide (it shows strong radio sources as bright spots or areas and fainter sources as various shades of gray).

The data in the vicinity of the Andromeda galaxy was also converted into a map. Although this radio telescope was a good instrument, its 2-to-1 frequency bandwidth was insufficient. After some analysis, John Kraus conceived of an instrument that was both larger and could operate over at least a 10-to-1 frequency bandwidth. Thus arose Big Ear.

In 1956, an agreement was reached between OSU and Ohio Wesleyan University (OWU, located in the city of Delaware, Ohio, about 20 miles north of Columbus). This agreement allowed OSU to build and operate a large radio telescope on some of OWU's land ("20 acres more or less") adjacent to Perkins Observatory, which, at that time, operated a 69-inch optical telescope used mostly by OSU's optical astronomers. This land was only a 30-minute drive north of the OSU campus. OWU agreed to restrict the use of the property in the vicinity of the radio observatory (OSURO) site in such a manner as to prevent interference, radio or otherwise.

Construction of the telescope, begun in 1956, was completed in 1961. It took so long because students were employed to do most of the construction, learning welding in the process. Funds for construction were provided by Ohio State University ($122,000) and the National Science Foundation (NSF; $400,000), of which OSU charged $150,000 in overhead leaving $250,000 usable. Receivers were built and installed. By 1963, mapping of the sky began.

The collecting area of the telescope consisted of two reflectors (mirrors using wire mesh) which reflected radio waves, one curved (paraboloidal) fixed (unmovable) reflector, and the other a tiltable flat reflector. The orientation of each reflector was along an east-west line. The paraboloidal reflector was 360 feet (110 m) wide by 70 feet (21 m) high. 500 feet (152 m) to the north was the flat reflector; it was 340 feet (104 m) wide by 100 feet (30 m) in slant height. This flat reflector was tiltable (one section at a time) through a total angle of 50 degrees, allowing 100 degrees of declination of sky to be observed.

It was a meridian transit instrument dependent on the rotation of the earth to move the beam across a strip of sky. Most of the observations were done in a frequency band on and near a frequency of 1420 MHz (a wavelength of 21 cm) where the size of the beam was 8 arcminutes in right ascension by 40 arcminutes in declination. Other observations were made around 610 MHz and 2650 MHz (wavelengths of 49 cm and 11 cm, respectively). Radio waves from a source on the southern meridian pass above the paraboloid across to the flat reflector, reflect back across to the paraboloid, and finally reflect back and are focused into either of two horns (funnel-like objects) that collect the radio energy. That energy is converted into a minuscule electrical current which is amplified millions of times by an amplifier near the end of the horn and by additional amplifiers in a room underground (the focus room). The amplified signal (including noise received from the surroundings and generated in the receiver) is detected (converted to low frequency signals) and then those analog (continuously varying) low frequency signals are converted into digital data for analysis and storage in the onsite computer.

The surface between the two reflectors (called the "ground plane") was covered with aluminum foil which served to reduce the unwanted radio signals from the ground and the surroundings. This design was unique at the time construction began (1956) but other telescopes of similar design were later constructed. The major advantages of this design are: low cost, low wind resistance, low interference from undesired radio signals, stable receivers, and a large collecting area.

Several graduate students worked at the Big Ear over the nearly four decades of its operation, most receiving Masters and/or Doctorate degrees. One of these was Robert (Bob) Dixon. His Ph.D. dissertation involved the development of computer techniques for the obtaining of faint signals swamped by noise. Bob later became the Assistant Director of OSURO.

As more computer programming to analyze the data taken by Big Ear was done, a point was reached whereby a systematic mapping of the sky could occur. This project was called the Ohio Sky Survey. Installment I of this survey was published in 1967; it covered 1000 square degrees (about 2.5% of the total sky). This and all subsequent installments provided the location (right ascension and declination) and source strength (flux density) for each source found. These sources were listed in a table and contour maps of flux density vs. coordinates were provided in each published installment.

Late in 1967, Jerry Ehman was hired by John Kraus, spending one half of his time on the Ohio Sky Survey and other related OSURO projects (especially computer programming), and the other half as a faculty member in the Department of Electrical Engineering. He was coauthor of two of the Ohio Survey installments.

By 1973, over 19,000 radio source positions and strengths had been measured, over half of which never had been measured by any other observatory. Thus, the Ohio Sky Survey increased the known source count by about 100%. Our survey was found to be very reliable by other astronomers, so we earned a good reputation. The survey was published in seven installments totaling 660 pages in the "Astronomical Journal".

As the Ohio Sky Survey was progressing, several sources with interesting spectra were studied in detail. A radio spectrum is the variation of signal strength (flux density) with frequency. The data from our survey was compared with observations of the same radio source by other observatories at different frequencies. In one case (the source OH471) it was relatively strong in our survey but not detected by any other survey. It became a candidate as an "Ohio Special", sources that deserve special interest. Periodically, members of our group would travel to other observatories to measure these "Ohio Special" sources at a variety of different frequencies to obtain both the spectrum and a better position. With a better position, a look at the Palomar Sky Survey prints might reveal the optical source that corresponds to the radio source. In a few cases, the Palomar prints showed nothing (a blank field). For some of those cases, we were able to encourage optical astronomers to take long exposure photographs of the region to pinpoint the optical source. Also, optical spectra of some of the sources were made.

In the case of OH471, the optical spectrum revealed a very large red shift (Doppler shift) due to the expansion of the universe; in fact, it was the first object known to have a redshift greater than 3 (specifically, 3.40) putting its distance at about 90% of the way to the edge of the visible universe (it was called "the blaze marking the edge of the universe"). Many other Ohio Specials also led to interesting discoveries (e.g., OQ208: a galaxy at about 1 billion light years distance; OJ287: an erratic, rapid, violently variable quasar; and OQ172, a quasar with the even higher redshift of 3.53). In 1976, three years after their redshifts had been determined, OH471 and OQ172 were still the two objects with the highest known redshifts (at distances of about 12 billion light years).

Some other notable accomplishments were achieved during the time of the Ohio Sky Survey. Bob Dixon prepared a user's guide to the Palomar Sky Survey, followed up by a set of computer-generated overlays on clear plastic with identifications of the optical objects that had been named. In 1970, Bob Dixon published A Master List of Non-Stellar Objects. Much work went into these projects.

On August 8, 1972 the National Science Foundation (our principal funding agency), without any previous warning, phoned John Kraus to inform him that it was cutting off their support effective August 31. We learned later that this was happening to NSF grants at other universities as well. It turned out that the U.S. Congress decided that less grant money should be given to universities for their research in favor of providing greater funding to national facilities. The net result of this was that our sky survey observations were speeded up until August 31 and then were stopped, the data were analyzed, written up and published, and the team members found new employment.

On December 7, 1973 Bob Dixon began a new program at OSURO without the help of funding (at least initially). The receiver system was modified to include an 8-channel narrowband filter unit in order to search for narrowband signals (in contrast to the wideband Ohio Sky Survey). The goal was to detect any form of strong narrowband signals that could be occurring either naturally or else artificially generated by extraterrestrial beings. The latter (under the designation of SETI, i.e., the Search for ExtraTerrestrial Intelligence) got the most publicity. Both Bob and Jerry found new employment (Bob at the OSU Computer Center, and Jerry as a faculty member at another local university), but both volunteered their time (as have many others over the years) to this new project. Bob and Jerry wrote a complicated set of programs to acquire and analyze the incoming data in real time; this was a real challenge with a computer that had only 32 thousand words (64 KB) of memory. Later, a 50-channel filter replaced the 8-channel unit.

Jerry took on the responsibility of looking at the computer printout for the narrowband survey, noting any interesting signals. When he looked at the data of August 15, 1977, he was astonished to see the strongest narrowband signal ever recorded from the telescope. He saw immediately that the sequence of numbers and letters (6, E, Q, U, J, 5) appearing only in channel 2 reproduced the antenna pattern for a small-angular-diameter radio source emitting a narrowband signal, just what would be expected for a signal from an intelligent civilization. He immediately wrote the word "Wow!" in red ink in the margin of the computer printout. He phoned both John Kraus and Bob Dixon to tell them of this momentous event. Many hours of discussion and research were conducted to determine the source of this signal.

The telescope was kept at the same declination setting to see if the signal would return on subsequent days (it never did). We started calling it the "Wow! signal". Although many possibilities were ruled out, a definitive explanation has not been found, even 22 years after the event. In 1977, for the 20th anniversary of the event, Jerry wrote a detailed article for the website of the group (http://www.bigear.org) in which he provides corrected positions for the signal and describes what possible explanations were ruled out. An ETI beacon signal is still open as a possibility.

In 1978 (one year after the "Wow! signal" arrived) John Kraus provided seed money to start publication of a magazine devoted to all aspects of SETI. He named it "Cosmic Search". In order to break even, at least 10,000 of each issue had to be sold from combined annual subscriptions and from sales of individual copies; that level was never achieved. A total of 13 issues were published over a three-year period before John Kraus discontinued it.

On December 28, 1982 John Kraus learned from a colleague at OSU that Ohio Wesleyan University was going to sell 264 acres of land (including the 20 acres Big Ear was sitting on) for $500,000 to a developer who planned to expand a nearby 9-hole golf course into an 18-hole course, and build some 400 homes as well. Courtesy was lacking, since neither the President of OSU nor anyone from OWU called either John Kraus or Bob Dixon. All of the volunteers were in shock. Many of the faculty of OWU were outraged, as were astronomers from across the country. The press picked up on the story and our work was heralded worldwide. The OWU President tried to justify his decision by saying that since our sky survey had been completed, there was no further use for the telescope; John protested but to no avail. Six months later, the OWU President resigned.

There were attempts to buy the land on which the telescope was sitting, giving the developer an opportunity for a large profit on the sale, but the developer refused all offers. Moving the telescope turned out to be logistically and financially out of the question. Fortunately, OSU arranged for a lease of the land on which the telescope and related buildings sat. The original lease was for 10 years (1983 - 1993), and then a new lease was obtained on an annual basis and was renewed into 1997. However, in 1997, the developers pushed OSU to abandon the telescope and OSU did little to oppose it. We were required to leave the telescope for developers to demolish, which occurred in early 1998. We moved the most valuable items to a location on the west campus of OSU.

In order to raise contributions to fund the operation of our observatory, we formed NAAPO (North American AstroPhysical Observatory). It is now a private foundation, so donations are tax-deductible.

When it was obvious that Big Ear was going to be destroyed, our group of volunteers talked about the future. For several years, Bob Dixon had been considering the idea of a new type (next generation) of radio telescope which he called "Argus", named after the mythological being that had 100 eyes and could see in all directions at once. An Argus radio telescope would be constructed of hundreds or thousands of small elements (antennas), each with its own receiver, detector, and analog-to-digital converter to transform continuously varying radio signals into computer data. The data from all of the receivers would be stored and mathematically manipulated to generate as many beams in the sky as desired (or as the computing ability would permit). This would allow mapping the entire hemisphere of visible sky at once, rather than the very small fraction (say 0.0001%) of the sky that all other telescopes see. Many of the volunteers readily accepted this new challenge and work has been progressing on the design, construction and testing of our Argus radio telescope. Bob Dixon was able to receive funding from the SETI Institute, and several colleagues from the ElectroScience Laboratory (ESL) of OSU have been working on antennas and receivers for Argus.

One of our volunteers, Cindy Brooman, does website development. Our group now proudly displays its own website. The URL is: http://www.bigear.org ; and it contains articles and photos on the history of Big Ear as well as information about our current Argus radio telescope development.


Contributions to the ongoing research efforts of NAAPO (make checks payable to NAAPO/OTTERBEIN) may be mailed to:

Dr. Philip E. Barnhart
4655 Indian Court
Westerville, OH 43082-8817

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