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The Building of Big Ear

The Design

The Big Ear Radio Telescope was designed and built under the leadership of the late Dr. John D. Kraus; at the time of his death in 2004 he was a Professor Emeritus and a McDougal Professor of Electrical Engineering and Astronomy at the Ohio State University. Kraus wrote in his book Big Ear Two, "The idea for the telescope evolved gradually over weeks and months of contemplation and pondering various designs and alternatives. The final design crystallized quietly and without fanfare from my notes and calculations." He had described his idea in the March 1955 issue of Scientific American.

Little Ear?

Before Big Ear was ever built, a scale model was built on the roof of Caldwell Laboratory at Ohio State University. A grant of $23,000 from the National Science Foundation was used to build the prototype. The model was constructed (following the design by Dr. John Kraus) by a graduate student named Bob Nash. The model took months to build, and had a receiving system two miles away on the roof of another university building. Using the prototype, Nash and Kraus were able to make measurements of the antenna pattern which confirmed their expectations. Bob Nash's construction of the model was used in fulfillment of his masters degree.

Location, Location, Location

Meanwhile, Dr. Kraus had been looking for a suitable site for the telescope. The site had to meet certain criteria: it had to be large enough for the telescope and without radio interference in the vicinity. Geoffrey Keller, who was then the Director of Perkins Observatory, suggested some land behind Perkins to Dr. Kraus. The land was owned by Ohio Wesleyan University. Therefore, in May of 1956, Dr. Kraus approached Donald Hornberger, who was then the Vice President of Ohio Wesleyan, to ask for the use of the land. An agreement was later signed between Ohio Wesleyan and Ohio State Universities granting 20 acres for a radio observatory.

Another grant of $48,000 from the National Science Foundation was used to start construction of the telescope, although the grant was so much less than expected that the telescope had to be scaled back from one with a 2000 foot parabola to one with a parabola 360 feet long by 70 feet high.

Help Wanted - Students, Welding Experience Preferred

The telescope was built almost entirely with student help to cut costs. Students Bob Nash and John Hoover were involved in the initial process of selection of girder shapes, bolt sizes and welded joint designs. Another student, Lou Malik, was hired on the spot after he offered Dr. Kraus his assistance as an experienced welder. Lou then taught welding to other students in his time between classes. Another student, Dave Lipphardt, aided in the design of the trusses and towers using his special area of interest in time and motion studies.

The Parabola Takes Shape

Work started with the 70-foot parabola tower legs, which were so large that they had to be constructed one at a time on a special jig set in concrete. As each tower leg was finished, it was lifted off the jig with a crane. By the fall of 1956, the foundation pillars had been poured.

In the spring of 1957, the students began assembling the parabola. Ninety-six trusses (30 feet long and made of steel angle and rod) were constructed west of the campus in a former factory building. After completion, the trusses were hauled to the observatory. The first bay was raised on June 10, 1957. The remaining 11 were assembled and raised during the summer and fall.

Dr. Kraus Goes to the Fair

By 1958 all bays of the parabola had been raised, and construction began on the tiltable flat reflector. Dr. Kraus had worked on many different designs for tilting the bays of the reflector, but got his final idea from watching a ferris wheel being turned by large steel cables at the county fair.

Meanwhile, the project had received additional grants from the National Science Foundation, and work was progressing rapidly. By the summer of 1959, the foundations had been excavated and the concrete poured for the nine flat reflector bays.

The Ground Plane - Giant Tanning Bed

By the summer of 1960, the tiltable flat reflector had been completed, and work began on the three acre ground plane between the flat reflector and the parabola. Since the ground plane needed to be reflective, yet inexpensive, Dr. Kraus decided on a base of concrete several inches thick with aluminum sheeting bonded to it. Huge machines were needed to push around the 20,000 cubic yards of earth which had been piled between the reflectors.

The concrete was being poured by July of 1961, and work began in September on the aluminum sheeting. The aluminum came in rolls which were five feet wide and had to be glued down with an asphalt-like substance. Dr. Kraus writes in his book Big Ear Two, "The work had to be done in dry, hot weather and the workmen were broiled not only by the direct rays of the sun from above but also by reflection from the shiny sheet aluminum below. They consumed what must have been record amounts of water and aspirin!"

The Missing Pieces

Many other components were also required for a fully operational telescope, including receivers, feed antennas, a computer, controls for operating the flat reflector winches, and a method accurately setting the reflector. A precision optical device for setting the reflector was designed by graduate student Al Herriman and machined by Jess Wolfe of the electrical engineering department.

A sensitive parametric amplifier was built by "Mickey" Uenohara at Bell Telephone Laboratories in New Jersey. Mickey had graduated from OSU the previous year, and volunteered to build the amplifier at cost ($6000). Graduate students Steve O'Donnell and Bob Townsend drove to New Jersey in 1963 to pick up the amplifier.

Big Ear Comes to Life

All pieces of the telescope had been completed, leaving the amplifier as the final element to make the observatory operational. When the students returned from New Jersey, the amplifier was connected to Big Ear and turned on. Switches were thrown and Big Ear began listening to the cosmos!

Information for this page was extracted from the book Big Ear Two by Dr. John D. Kraus. This book contains many, many more anecdotes than were contained in this document, and makes for excellent reading!

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Last modified: August 13, 2005.