By Kenneth Franklin

Although there had been earlier attempts to detect radiation at wavelengths longer than the infrared, it fell to the efforts of Karl Jansky at New Jersey’s Bell Labs to find this energy in 1933. He was trying to learn why trans-Atlantic radio telephone communications were degraded by some sort of natural noise. He found that the source was located in the sky, so the phone company could do nothing about it.

Grote Reber near Chicago found the problem fascinating and investigated the celestial source. He made the first radio maps of the Milky Way. He submitted his findings to the Astrophysical Journal whose editor, Otto Struve, sent two astronomers to visit Reber and assess his instruments and his work. Struve decided to publish Reber’s paper, because if correct, it was important. "If not," he said, "it would simply join many other published papers that were not important." Of course, it and Reber’s subsequent papers, are now considered classics.

In the late 1930s, science news items reported battleships could now fire on enemy vessels at night when the targets could not be seen by eye. As World War II got under way, reports claimed the new device could tell destroyers from battleships. Later, whatever this thing was could begin to detect airplanes. After the war, we learned that the device was called radar, for RAdio Detection And Ranging.

Sir Robert Watson-Watt in England had perfected the equipment to the point that they could count the German bombers headed for Britain. One morning their receiving equipment, aimed over Europe, was jammed so badly that they knew the Germans must have discovered their secret device. A great flight of bombers must be headed their way. The English fighters were scrambled, but no Germans appeared. The next few mornings the same action took place. The antennas, under the direction of J. S. Hey, were then set to following the source of the jamming radiation, and it mounted the sky. The source was the sun. Hey and his crew had made the surprising astronomical discovery that the sun was a strong emitter of radio waves, but it was a military secret! It remained so until 1946 at war’s end.

The improvement in radar’s observation abilities was made as engineers learned how to make electronics work at higher and higher frequencies, putting more and more smaller waves to palpating the targets. It worked so well at a wavelength of about 10 centimeters the engineers tried 3 centimeters. They tested the system thoroughly, and It worked so well they went into production to provide 3-centimeter radar devices for use in the Pacific Theater. When they were put into service in the South Seas, they couldn’t see past the shores of the islands. It seems they had tested all over dry Arizona where they never found they had settled on the frequency of a water vapor absorption line. In a talk, Charles Townes said the abundance of this equipment was a boon to post-war microwave spectroscopy physics.

On another island there was an important radar outpost for defense of the Hawaiian Islands. One day the equipment failed. Technicians sought the problem, checking from the antenna into the electronics until they got to a box that had a warning:

TOP SECRET

DO NOT OPEN UNDER ANY CIRCUMSTANCES.

SEND TO THE DEPOT.

They then looked for the trouble all the way from the receiver toward the antenna, but came to the same box. They put a second system into use, but it, too, soon failed. Technicians came again to the same box. The Lieutenant in charge knew the island observation post was very important, that an operating radar was crucial. "Open the box and fix it!", he ordered. They opened it. It was empty! It was a cavity resonator, another top secret electronic device used to insure stable oscillator operation – an electromagnetic echo chamber. E. G. "Taffy" Bowen had carried one in his lap, it was told, in a flight from England to the US during the war, insuring better radar instruments for us.

After the war, there was a surfeit of old radar equipment, now used and useless surplus. In Australia, the Commonweath Scientific and Industrial Research Organization was a well-disciplined group who had contributed to the improvement of radar. They wanted to continue to work together. A cadre of top people knew of the work of Jansky and Reber and decided to start work in radio astronomy.

The early 1950s was an exciting time in the field. Every thing investigators looked at was a discovery. The sun was especially ripe for new information. Most of the work was coming from the CSIRO. In time I got to know many of those workers, including B. Y. Mills who had visited Berkeley when I was a graduate student. Otto Struve, then Chairman of the UC Astronomy Department, had written an article about radio astronomy for Sky and Telescope Magazine. I suggested to him that he should give a course in it, as it was missing from the curriculum. He protested that the article was the entire extent of his knowledge of radio astronomy. I began to read the literature on my own. We had a very good library which subscribed to all the pertinent journals, so it was not difficult to keep up with developments.

There is a curious sidebar to this story. One of our professors was Louis Henyey, a friend of Edward Teller. (Henyey was one of the astronomers Struve sent to visit Reber.) Teller visited Berkely one day, and at a colloquium he presented a theory he had concerning an aspect of solar radiation and particle emissions. I was surprised that he was interested in the sun, but I recognized he was missing some information. After the colloquium was over and he and Henyey were ready to leave, I accosted him. I explained how the sun was being observed in radio waves, seeing ionized material streaming from the photosphere, and deducing its velocity from the change in frequencies received. I was surprised when he interpreted part of my discussion as the correct velocity of 3000 km/sec. Then I explained new information obtained with more sensitive equipment that showed other material having a velocity of 100,000 km/sec. The nice part of the tale is that this velocity confirmed his theor y, and he had not known about it. He and Henyey left in good spirits. Nothing further came from the encounter.

The Carnegie Institution of Washington’s Department of Terrestrial Magnetism, then headed by Merle Tuve, had a big conference on radio astronomy in January, 1954, which I attended. When a fellowship opened up at DTM, I was fortunate enough to get it. Perhaps my interest in radio astronomy had made an impression in Berkeley. When I left for the fellowship, my office at the Students’ Observatory was given to Ron Bracewell of the CSIRO.

Australian Bernie Mills had been visiting DTM during the big conference. He had told the DTM physicists of his and F. Graham Smith’s design for a crossed antenna array. Merle Tuve, always enthusiastic, decided it was a good Idea. "Let’s build it." I arrived in September, 1954, and was assigned to work with Bernie Burke on the Mills Cross project, still in its early phases. The plan was to make a survey of the sky at the long wavelength of 11 meters, a significant contribution to the field. As the apparatus was being continually improved, we stayed on the same band of the sky to monitor the progress. It was just luck that Jupiter crossed the pencil beam every day. Yes, the 1950s was an exciting decade in radio astronomy. It was fun for Bernie and me to be a part of it.

Our 1955 discovery that Jupiter was emitting radio waves is recorded by the plaque set up at DTM’s Mill’s Cross site near Seneca, Maryland. I am sorry not to be able to attend the proceedings, but I am deeply moved by the honor of being included in the memory of our serendipitous discovery 50 years ago. I had no idea it would be regarded as worth all this effort. I will conclude by quoting Nick Mayall at the ceremony on Kitt Peak naming the 158-inch telescope for him: "I didn’t expect it. I don’t deserve it. But I like it."

Thanks again to Leonard Garcia for working in my behalf, and thanks to all his colleagues for their efforts toward the success of this commemoration event.