Interview with Arthur E. Covington

Description

Arthur E. Covington, 1913-2001. Interviewed 23 June 1976 at the AAS meeting in Haverford, length of interview: 112 minutes.

Creator

Papers of Woodruff T. Sullivan III

Rights

NRAO/AUI/NSF

Type

Oral History

Interviewer

Sullivan, Woodruff T., III

Interviewee

Covington, Arthur E.

Location

Haverford, PA

Original Format of Digital Item

Audio cassette tape

Duration

112 minutes

Interview Date

1976-06-23

Interview Topics

Personal background; wartime research at Berkeley and at NRC, Ottawa; setting up first radio observations in 1946-1947; 1947-1976 history of daily 10.7 cm solar monitoring; eclipses and building high resolution interferometers; flares in microwave and comparison with optical Hα.

Notes

The interview listed below was conducted as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) and was transcribed for the NRAO Archives by Sierra E. Smith in 2015. The transcript was reviewed and edited/corrected by Ellen N. Bouton in 2016. Any notes of correction or clarification added in the 2016 reviewing/editing process have been included in brackets. During processing, full names of institutions and people were added in brackets when they first appear. Places where we are uncertain about what was said are indicated with parentheses and question mark (?). If researchers are able to suggest correct text, please contact the Archivist. Sullivan's notes about each interview are available on Sullivan's interviewee Web page. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of Sullivan's original cassette tapes.

Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons, including subsequent experiences, interactions with others, and one's feelings about an event.

Series

Working Files Series

Unit

Individuals Unit

Transcription

Transcribed for Sullivan in 1977 by Bonnie Jacobs, transcription corrected and edited by Ellen Bouton in 2016.

Begin Tape 46B

Sullivan

…23rd June at the AAS meeting in Haverford [PA]. Can you tell me a little bit about your educational background and how you got involved in radio work in general?

Covington

I like to start recollections like this with my birthdate – September 21, 1913, in Regina, Saskatchewan. It happened to be a Sunday and I looked through my father’s diary, and I wish I could recall correctly what he said, but it goes something like this: “May he always see the light.” Well, my family – I guess I have an unusual background which only recently I’ve been able to probe. My father was one of those Englishmen who came from London in 1882. And there was no railroad. And as a boy I can recall him telling me (?) being a pile of bones. He grew up there as a contractor and made many of the buildings. And my grandfather came out a year later. He was a blacksmith. At that time the Indians were in turmoil and he was employed to shoe the horses of RMCP [Royal Canadian Mounted Police]. This seems a rather roundabout way of getting into the beginnings. Well, because of the shortage of women in there he married late in life, so there was a tremendous age difference between my father and mother. But one thing my mother told me when I was quite young – my father died when I was young as a matter of fact –my father was interested in astronomy, he belonged to some astronomical society. This happened to be the Regina Center, the Royal Astronomical Society of Canada. And it was only a couple of years ago I discovered that he was one of the charter members of this group. It never survived and in Regina there is now an independent amateur astronomical society.

Sullivan

Did he teach you any astronomy as a boy?

Covington

Oh, in a sense, he would read me these mythological stories, so my introduction, I guess, to astronomy was more via the classical myths.

Sullivan

Yeah, constellations and so on.

Covington

There are many details of that part of my life. Well, then the family moved to Vancouver B.C. Well, other parts of British Columbia. There is another scene which I’ve often tried to date. We had relatives in Victoria B.C. and as you know the 72-inch telescope, the Dominion Astrophysical Observatory, is there. And as a small boy I visited with my aunt and uncle and family. And on the way up I guess I became a very noisy little boy and I just (?) and my uncle spoke to me quite severely in no uncertain terms and put me in place. The story is often repeated in the family. I can recall visiting the Observatory and seeing the two clocks there and the huge dome. I must have been 7 or 8 and asking my father what the two clocks were for. And he mentioned the two kinds of time – sidereal time and ordinary time.

Sullivan

Now what about your college education? Was that where you first got interested in radio, or were you…?

Covington

No. Since my father died quite young, I think I was age 13, I wanted to go out and help support the family and so I started working in a cabinet factory for about 3 years. After I’d gained about 6 months in high school. Well, then after 3 years in the cabinet factory I became aware of amateur radio, and so I built in 1930, I had an amateur station operating – 210 oscillator. At this time it’s rather strange to recall that the rectifier to supply the DC to a plate. It was derived from a lead slop jar. Another thing I did – radio inspectors wouldn’t like it now – I read about Marconi and spark transmitters, got ahold of an old spark coil, and put it directly to an antenna. [Laughter] But for two years it was a lot of fun. I made about 30 contacts from Vancouver – right across Cedar Rapids. I just have a few of those QSL cards – now most of them have vanished.

Sullivan

But there weren’t too many amateurs then, probably?

Covington

I met a few – these radio amateurs. Oh, there were half a dozen as I recall.

Sullivan

In Vancouver?

Covington

Yeah.

Sullivan

So 30 would get you to quite a radius before you picked up that many people. And so you had this interest in radio. Did you follow this up in your college education?

Covington

Well, that was a question of always earning a living. I became conscious of commercial operators so I spent two years getting my commercial tickets. This would take me to ’33, ’35. And then in my spare time I got my matriculation for university and began to realize one needed the technical information. I was curious too, to get involved in all these things.

Sullivan

But it was the middle of the Depression, too. You had to keep on working – you couldn’t just go to college?

Covington

That’s right.

Sullivan

And so you went to which university then?

Covington

It was the University of British Columbia. Working during the summers as wireless operator and assistant bursar on the Canadian National Steamship Company. In the summer they had tourist trips from Vancouver, Prince Rupert, Skagway, and back again – a two week run. That way I earned, I guess it was about $120 a month clear. Of course the board was on the ship. Well, then I got a BA in physics in 1938 – maths and physics. I was always interested in mathematics so it was a combined maths and physics. While at University I accidentally met an amateur astronomer. At some time or another, it must have been age 16 or 17, I ground myself a 5-inch mirror, making use of (?) glass. And again, I came into contact with a group of amateur astronomers. They were awfully helpful. I admit the figure on the mirror is not perfect, but still good enough to see any of the heavenly sights.

Sullivan

But you say also as an undergraduate you met some amateur astronomers?

Covington

Oh, I guess I’m getting somewhat confused in my recollections here. Well, my interest in amateur astronomy carried through as an undergraduate. I remember taking my mirrors to the University and setting them up in the basement and trying the (?) tests. In fact, I still have some of the photographs of the (?) shadows.

Sullivan

So besides this early interest in radio you also had the very early interest in astronomy.

Covington

Amateur astronomy, yes. When ’38 came, oh, then I guess people were quite conscious of the rise of the Nazi movements. ’39 I think war was declared in Canada.

Sullivan

And what sort of job did you take when you finished your degree?

Covington

Oh, we had a lab assistant. I went on for an MA degree in physics alone, and to support myself and learn, of course, I became a lab assistant. The thesis work was on electron microscope. The University of BC through G.M. Shrum and the graduate students who had gone before me, had developed quite a reputation at the University of California. There’s a university at Lafayette – University of Indiana.

Sullivan

Or Purdue?

Covington

Purdue, I mean, yes. And so after the MA I had hopes of going either to Purdue or Berkeley. It turned out to be Berkeley in 1940.

Sullivan

I see. To go on for a PhD?

Covington

Yes. That was quite an exciting year as you probably realize in hindsight.

Sullivan

Yeah. Now who were you working with there in Berkeley?

Covington

They happened to receive an RCA electronic microscope just about when I arrived and having produced a thesis on a simple electron microscope I was willing to sort of put it into operation. But then the atomic energy development occurred and all these things got shoved into the background and ultimately I became one of the assistants in the Radiation Lab. For one year I was a teaching assistant from ’40 to ’41, and then in the Radiation Lab from ’41 to ’42. Again, that’s another old story.

Sullivan

What sort of things were you working on?

Covington

Oh, I guess tuning the cyclotron. The Crocker Radiation Lab…

End of Tape 46B

Begin Tape 47A
Sullivan

This is continuing with Arthur Covington on 23rd June 1976. Now what were you working on at the Radiation Lab in Berkeley? Just roughly?

Covington

Keeping the cyclotron tuned up so the beams stayed in the target. We had two programs, the experiments and physics (?), and then a certain part of time was allocated to radiating patients. Lawrence’s brother was a medical man. It’s quite remarkable that the two developments, the physical and the medical, should go along side by side. So all sorts of things like cleaning out the (?) and tuning it up and putting in heavy water, peeking behind the curtains to see that the patients had been put in place and then punching the button. [Laughter] All the time, you see I was a Canadian in a foreign atmosphere, and as the atomic bomb developed and everybody knew what was going on, more or less, then a number of pressures came on. There was a curfew. I was exempt from the curfew, but the professors, such as Segrè, who was of Italian background, had to be off the streets by 7:00 o’clock.

Sullivan

Was this a general curfew for the population?

Covington

Aliens. This was after Pearl Harbor.

Sullivan

But Canadians were excepted?

Covington

I guess I had all the clearances. I know I had all the cards – I can’t recall the details quickly. In any case, the radar development in Canada had proceeded. I’d been getting letters of various kinds, and in May, I finally left the Radiation Lab to pursue the radar program in Ottawa at the National Research Council.

Sullivan

And who was running that program?

Covington

Well that’s quite a complicated story. I think I’d rather not go into it right here. It has some connections, or rather a lot of them, I just can’t immediately recall.

Sullivan

What were you working on at the NRC?

Covington

Well, when I arrived there first – this would be July ’42 – the radar program of the National Research Council was conducted at a radio field station about 10 miles south of Ottawa. Again, it was behind a screened fence and a fair amount of security. And the first task I was assigned was to help someone who was trying to excite a fairly large IQ cavity at a low rate and then discharge it suddenly so that a pulse of energy could be generated quite intensively hard. It never worked but at least I learned something about standing wave ratios, transmission lines. If I recalled correctly, the next job I was given was to work on a 30 megacycle IF strip. It was quite an experience because it was the first time I’d worked with feedback. The feedback, of course, was used to widen the bandwidth. Then the general radar program had progressed so that the senior staff at the radio field station advocated the 10 cm program for 3 cm and 1 cm program. And in time I was transferred to look after essentially 10 cm microwave components. And this involved the magnetrons, the TR boxes, and transitions of various kinds.

Sullivan

How would you describe the work that was being done at this laboratory relative to that at the MIT Radiation Laboratory? Was it sort of in parallel?

Covington

It was in parallel. In fact, I made one trip to Boston to see the MIT Lab. Historically, it’s fairly well known that the microwave work at the National Research Council had about a 3-month head start over that of the MIT Radiation Lab. And this occurred because the Tizard mission from England first stopped in Ottawa before going on to Washington. [2016 note: British Technical and Scientific Mission, September 1940, led by Henry Tizard]

Sullivan

Bringing the information about the English results which they had decided to share?

Covington

Oh, yes. The 10 cm magnetron which was so famous in the development of radar was brought to Ottawa first. We had access to it for 48 hours, so I’ve been told – nondestructive testing. The thing was x-rayed and I guess measured and talked about but that was all. It was a very secure situation, I believe, somebody was always attached to it.

Sullivan

Did this 3-month lead hold out throughout the whole War?

Covington

No. Of course then you get into the situation between Canada and the United States – population question. Ten Americans to one Canadian.

Sullivan

That’s what I was wondering. Did you specialize in some area or were you coordinating programs?

Covington

There was a liaison officer. I mentioned Berkeley, particularly the Radiation Lab. There was a liaison officer for Canada to the United States, a man by the name of Fred Saunders, who was a graduate of Berkeley, or, probably ’28 or ’29. I’ve forgotten the exact date. It could be all dug out of the records. He was a classmate to Ed Condon, and so the liaison between Canada and the United States was done through Fred Saunders at this sort of level. The actual technical contact between the Tizard mission and the National Research Council was through John T. Henderson. In 1957 he was president of the IRE.

Sullivan

So you stayed at the NRC throughout the whole War, I guess, working on radar. And then what happened after the War was over?

Covington

I guess in the first place being a scientist who had been recruited for such work, most of the fellows wanted to quit and go back to school or get a job. A large number of them became interested in atomic energy. It was something new and some of them had been involved. As you know, the Canadian government had set up the Atomic Energy Development at Chalk River. And it would be interesting to figure out the exact fraction of our radar engineers who subsequently went to Chalk River. And I think this makes a tremendous difference in how Canadian radio astronomy developed in reference to the Australian radio astronomy.

Sullivan

Or British.

Covington

Yes, I hadn’t thought about the British. Probably the same fact that the Americans were so tied up with atomic energy that they just couldn’t see radio astronomy.

Sullivan

Well, I’m puzzled. I have some ideas but I’m puzzled why American radio astronomy lagged for so long, and this may be part of the reason. Is to look into what fields the people from the MIT Radiation Laboratory, for instance, went into and so forth. That might give some good insight into what caused it. But anyway, what was your own decision at this time? You decided to stay at NRC, I guess.

Covington

Yes, this would be in 1945, the end of ’45 I approached my immediate superior, W.J. Anderson, he was a cyclotron engineer at Purdue University. Both of us knew about the secret development of atomic energy and then a newspaper report came that there’d been an explosion – an atomic explosion in Japan. We just looked at one another and said, “Gosh, they’ve done it!” It was hard to believe our eyes. I think both of us felt that the task was so out of this world that beyond human….

Sullivan

That it wouldn’t happen, yeah.

Covington

Subsequently, W.J. Anderson became a radiation safety officer at the Chalk River development. And when there was a breakdown in the reactor there, he wrote the final analysis. You can find all this buried in the literature somewhere.

Sullivan

But you were talking about going to him with your proposal for what you wanted to work on.

Covington

Oh, yes. He was in charge of what we called the “tube lab.” In addition to the Canadians developing the magnetron independently of the United States, we developed other tubes like the Klystron, the Sutton tube, as the War went on and they went to higher and higher frequencies. At the end of the War I was wondering what to do. The authorities in the NRC wanted people to get out of military work as quickly as possible and so were given much of a free hand. I approached W.J. Anderson and told him about my reading of Grote Reber’s work and of amateur radio astronomy. We had all this radar equipment and it was so easy to put together something and try an experiment. And this happened to be on the wavelength of 10.7 cm which he dictated more or less by the magnetron that Tizard brought over.

Sullivan

Right. What you said, in turn, was just a very arbitrary thing that had to do with the…

Covington

Well, not entirely. I mentioned one story that could come down. Having settled – trying to push the wavelength as short as possible there came a time of drilling a hole in a block of copper to determine the dimensions of the magnetron. And it happened to be the tool used to pull out the hub of a bicycle. So that probably determines why the wavelength is 10.7 cm rather than 8 or 12 or something.

Sullivan

When did you read Reber’s work for the first time?

Covington

When I was at University I recall, browsing through the library. And in one magazine, again, my recollections are not clear, there was a picture of Grote Reber’s telescope in Illinois. I was working on the electron microscope at the time and, of course, the ideas are somewhat related. I’d even thought of the idea of putting an electron microscope somewhere in the eyepiece of an ordinary telescope to reduce the light amplification.

Sullivan

An image tube?

Covington

An image tube. [Laughter] Of course, that never materialized beyond thinking about it. Subsequently, I look back on some in these old journals and at that time Reber’s work was very well advertised.

Sullivan

Yes, right, he had several articles at the time. And so you decided it just looked like it was worth following up?

Covington

Yes. And permission was given. There were two aspects of it: building the radiometer and building the radio telescope. I had the radiometer going in early 1946 and the radio telescope was completed in the summer of 1946.

Sullivan

And what was that telescope?

Covington

It’s a 4-foot reflector which was taken off the GL3 C radar. GL standing for Gun Laying Mark 3 and the C for Canadian version of it. Incidentally, when I talked about that radar set I’ve heard and seen it written that immediately after Pearl Harbor the Canadian military authorities shipped one of these several sets to the Panama Canal because the Americans at that time didn’t have such high definition radar sets.

Sullivan

In order to defend the Panama Canal?

Covington

Yeah. The radar sets at Pearl Harbor I believe were 200 megacycles.

Sullivan

And what were these radars?

Covington

The Canadian ones? They were the 2800 MHZ – 10.7 cm.

Sullivan

Was this equatorially mounted?

Covington

The radio telescope turned out to be a real hybrid. It had the GL, Gun Laying reflector, and the axis was part of a marine 268 radar which was set at a polar angle and carried the rotating coupler. It was a real hybrid of various things. We put it on the sun as I recall on July the 26th. It was one day after the big flare had occurred on the sun. The sunspot was visible with the naked eye in the evenings of that period. I can recall seeing the sunspot when the sun was low on the horizon. And the frustrations of not being able to complete the fabrication in time to get some observations. As it was we were one day – we missed the big flare by one day.

Sullivan

As you were building the radiometer and the dish, was your objective solar observations to begin anywhere?

Covington

Oh no, I was going to do cosmic noise. In fact, we created some files with the title Research on Cosmic Noise.

Sullivan

Because of Reber? You were influenced by his maps and so forth and you wanted to see what they were at a higher frequency?

Covington

Yes, the sun was just incidental. I think part of this was flavored by what Southworth had done. As you recall, Southworth had discovered solar emission in the microwave band in 1943.

Sullivan

Right. Did you know about this before the publication at the end of the War?

Covington

Yes. We’d known about Southworth’s results because through our scientific liaison there was an exchange of documents. On the other hand, I knew nothing about Hey’s work. The English liaison was a bit more remote and I think a bit more severe.

Sullivan

Do you still have a copy of this war-time document? I’ve never seen that. That would be very interesting.

Covington

I suppose it exists in our files. It could be an interesting thing to dig out.

Sullivan

Yeah. I’d be very interested to see what it says. So you knew about this work, but you were planning to do the galactic background radiation, as it’s called now. So what happened when you first got something working?

Covington

The idea was to… The sun was present with a beautiful sunspot and, of course, the obvious thing – I think scientists are somewhat opportunists – was to try it out. The first observations were made when the drive motor was not complete, so all I could get was a drift curve. And I still have the records of a simple bell shaped curve which represents the sun passing through the beam of the antenna. Well, then a bit of an excitement. Well, there it is. And then the next question was polarization – the single dipole, and I think I rotated the dipole through 90 degrees to see if there was any polarization of the solar emission. Right away I established that the two orthogonal components were more or less equal. And that was all that I did that particular day. The next question of course, was the intensity factor. You see the qualitative results and then try to figure out, well, is that – what do the numbers mean?

Sullivan

Right, let’s calibrate this thing. Were you interested in using the sun as a calibration source for the antenna beam at all? Was that another motivation to look at the sun?

Covington

No, at that time calibrations were completely open.

Sullivan

So you just took the size of the beam as being roughly ?/d?

Covington

The factors that are entered into calibration are the gain which is really interested in the equivalent area of the dish. We know that fairly well from radar work.

Sullivan

That’s true.

Covington

The other – the main unknown was the sky background which the sun was projected against. Now the beamwidth of the antenna was about 7 degrees so there was an awful lot of empty sky. I think my first guess – we really didn’t know about the temperature of the empty sky.

Sullivan

At this wavelength, right.

Covington

I just can’t recall what I did next.

Sullivan

You didn’t take it to zero?

Covington

No. I know I didn’t take it as zero. As you go to the shorter wavelengths the water absorption starts to come in,so there’d be a certain thermal emission from the water vapor in the earth’s atmosphere. Then there was the question of emission from the ionosphere and possible ground reflections in the ionosphere. Since I’m not a theoretically inclined person, it was definitely an experimental approach that I took. And it involved calibrating the radiometer using a load of some kind. At one stage, I’m not quite sure when, I remember making the resistive load which could be plunged into a flask of liquid nitrogen, because that would get you a temperature considerably below room temperature.

Sullivan

Was this a technique that had been used at the NRC Lab before?

Covington

Not that I know of. It was certainly the obvious thing to do. For very small temperature variations I’d been using a piece of platinum wire matched into a waveguide and heating it with an electrical current. From its resistance, of course, you could calibrate its temperature. Those were for 10s and 20s of degrees. Finally, there are a number of stages here which I can’t quite recollect quickly. But the ultimate outcome of a lot of experimentation was to make a radio black box, about 18 inches as a cube, and this was placed over the dipole in the 4-foot dish. There had been a lot of theoretical discussion of this problem by an Englishman, R.A. Burgess. I just borrowed the theory that he had outlined – the equilibrium between the black box and the termination you put to the antenna which is connected to a space of a black box. This proved very satisfactory. Later on I made another black box in which I could heat it to various high temperatures and in that case I would extrapolate down in towards absolute zero and it involved having a good detector to avoid curvature errors.

Sullivan

This black box, was the dipole inside while it was mounted on the antenna or was this on the bench?

Covington

The black box could be mounted right on the antenna. We stuck a thermometer in it so you would then get a measure out of the temperature of the emission. It has the advantage of eliminating all the ohmic losses in the transmission line. In any case, the result of these experiments I think I assigned – I have to check – 50 degrees absolute for the sky temperature. And then, once I had determined this, I decided to start observing the sun making use of emission from the black box at 50 degrees and then using the temperature emission. Fifty degrees was assigned to the zenith and the black box supplies the ambient temperature. When you have two levels and then you can find what the solar emission is. That same system is being used even today.

Sullivan

So it seems that right from the very beginning then, you spent quite a bit of time on absolute calibration of your measurements?

Covington

Yes. On one theory – the black box was always a source of discussion and argument. People would say, “Well, it isn’t a black box. Cosmic rays can go through it.” [Laughter] Whenever an astronomer would visit the Institute, he’d see the radio black box and, of course, they’re familiar with optical black boxes, and the endless discussions. And it was a remarkably easy way to enable someone familiar with the optical field to enter this new radio field.

Sullivan

But now I’m just noticing that the first publication that I have down by you is in Nature in 1947 in which you talked about the partial solar eclipse in November of ’46. [2016 note: Micro-Wave Solar Noise Observations During the Partial Eclipse of November 23, 1946. A.E. Covington. Nature 159: 405-406, 1947.] So it seems like you did not talk at all about these first observations. You did not publish them – only when this eclipse came along. Is that correct?

Covington

Oh, I got sidetracked into monitoring a noise from the zenith, the sky background. And there’s a prior publication to the eclipse observations.

Sullivan

Terrestrial Magazine?

Covington

Yes. But the partial eclipse came along suddenly, and I was more or less unprepared for it. We had made the initial observations I discussed, and then decided to tear the equipment apart to make improvements. And about two weeks before the partial eclipse, my wife told me from a newspaper account that a partial eclipse was occurring. [Laughter] What was I doing? That certainly put the bee in my bonnet. I was able to approach our shop manager and get priorities and some of the staff worked overtime. And one day before the eclipse we had the equipment reassembled and operational. It was a very fortunate situation because, as I recall, November the 21st, the day, turned out to be beautifully clear and we could watch the whole partial eclipse through dark glasses, watched the radio record and various contacts. There was a large spot on the disk at the time and we could certainly see when it was being covered up by the moon, or uncovered.

Sullivan

I have a note here that you determined what the temperature of that sunspot group was from this as one and a half million degrees.

Covington

Yes.

Sullivan

Which was one of the very earliest determinations of the high temperature of a sunspot group. Or the fact of the localization of these high temperature regions. But now had you … and you also have the temperature of the quiet sun was 5,600 Kelvins.

Covington

I guess it’s 56,000.

Sullivan

No, 5,600, the quiet sun part of it.

Covington

I recall 56,000. [Note added by Sullivan to original typescript: “This is correct.”]

Sullivan

Well, maybe I copied it wrong or maybe it was misprinted. OK, 56,000. But now had you determined from non-eclipse observations also this temperature?

Covington

No. It was the first real calculation I’d done.

Sullivan

I see. But why couldn’t – you could have done it from the non-eclipse days just as well could you not?

Covington

Not for the sunspot because….

Sullivan

Oh, not for the sunspot, no! But the quiet part of the sun.

Covington

I suppose we could have, more or less, yes. I just didn’t do it.

Sullivan

You just didn’t do it. The eclipse goaded you into making some calculations?

Covington

Yeah, that’s it.

Sullivan

But tell me about the microwave sky noise and what you did for that. I’m interested in these bursts or whatever.

Covington

Well, that’s rather a lost cause at this stage. Although there are one or two observations which I still stand by. But, of course, they don’t really…

Sullivan

Can you just describe what the nature of the phenomenon was?

Covington

Oh, as was well known the sun, the flares occur on the sun and these produce ionospheric disturbances. At this time scientists were quite critical, and many of them assumed that the radio bursts were really radio emission from a disturbed ionosphere. And to sort of counter this argument, I actually for a while had two radiometers and two radio telescopes in operation: one following the sun and one pointing toward the zenith all the time. So if the background emission was enhanced, there would be a registration in both radiometers. Now if it were true solar origin, only one would respond. It’s interesting to know, I think Appleton and Hey recorded in their early observations one source of radio noise coming from magnetic north and this was part of the argument that the solar noise bursts were terrestrial origin.

Sullivan

I see. I’m not familiar at least with published papers arguing this point. Do you remember that there were such papers?

Covington

Yes, I can supply the references.

Sullivan

Yes, I’d like to have that.

Covington

And also Reber in one of his notes, can recall hearing certain kinds of swishes at night time and in day time and he was thinking that some of these noise bursts were locally produced by the energetic particles coming in.

Sullivan

So anyway, you got some bursts which were coming only from the zenith, not from the sun. Or how was it?

Covington

Oh, at most there were a few bursts coming from the zenith and to see how they related with magnetic storms and so on I approached the Dominion Observatory and examined the magnetic records. There are a few good examples of coincidence. But by and large most of the bursts were of solar origin, that is, originating in the radiometer and radio telescope which was apart from the sun.

Sullivan

And this phenomenon you say is still not really resolved as to ….?

Covington

Well periodically it keeps coming up again. It really hasn’t been nailed down.

Sullivan

Right, no one has spent the time doing it properly.

Covington

That’s right.

Sullivan

I think you should do it. You’re the only one that’s going to do it.

Covington

Oh, I don’t know. [laughter]

Sullivan

You’ve got the equipment, the patience to monitor. OK, if I go on to your next publication, that was really the first major one in Proceedings of the IRE in ’48 in which you established that there was a 27-day periodicity. [2016 note: A.E. Covington. Solar Noise Observations on 10.7 Centimeters. Proc. IRE 36: 254-257, 1948]

Covington

Well, coming back to the eclipse observations, I think they were the ones which really suddenly shot me from an obscure lab technical into someone in the forefront of radio astronomy. In that connection there is another incident which has yet to be recorded. During the War, Sir Edward Appleton was Secretary of many organizations. Of course, then there was the classic paper of Appleton and Hey’s who knew all about radio astronomy and its implication. But he’d spent much of his time during the War in England, and after the War ended he was given a trip to North America, I think he was giving the lectures to Arthur D. Little Co., he gave the first honorary lecture. And either coming or going from that presentation he stopped in at Ottawa. It happened to be one or two days after the eclipse. Our management, of course, was quite anxious to show Sir Edward what had been accomplished. I can remember the great pains we went to cleaning the desks and benches, and in one particular case, in order to save time, we made a 7 foot or 10 foot wooden stair to go over a security fence. [Laughter]

Sullivan

Just for his visit, eh?

Covington

Just for his visit. I came back with the eclipse records. I knew about Sir Edward’s account of solar noise bursts and his plea for construction of large radio telescopes to single out the emission from radio spots. All this is published in Nature somewhere.

Sullivan

Well, I’m not sure about his plea for large telescopes. Is that also published in Nature?

Covington

Yes. I hope I’m right. Or maybe some variation – I may be being somewhat free.

Sullivan

OK, I’ll check that out.

Covington

And I remember standing by the bench and waiting for his arrival. It came with the President of NRC and other high officials. As soon as Sir Edward saw what had happened, everything clicked and we started talking. I began to realize, I explained everything, and he wanted to know more and more. And I presumed a lot of time. Sir Edward talking to me – the time was rapidly vanishing and the President of NRC was looking at me [laughter] – daggers and so on, and he finally interrupted. But I could hardly stop the enthusiasm.

Sullivan

Were you able to demonstrate the dish also?

Covington

Not at that time. I showed him the equipment. But he made a point when he returned to England of sending me some autographed reprints.

Sullivan

I see, so he was obviously impressed by this set-up. Another question before we go any further, obviously you got hooked on the sun by this point and you forgot the cosmic noise part. How did that exactly happen?

Covington

Oh, I guess that goes back to a good physics professor. We had a course in spectroscopy. The professor is Arthur Croaker [Croker? Kroker?], University of Toronto graduate, and he’s isolated some of the lines in lead. And one of the first possibilities of a research thesis for an MA was to tackle the lines of iodine. I looked at iodine and realized I couldn’t be a spectroscopist. But in these discussions he mentioned Fe XIV and [Bengt] Edlén’s work and mysterious coronium. So I was well versed in the high temperature of the corona as discovered by spectroscopy. After making the calculations for the solar eclipse and coming up with this million and a half degrees, coupled with the fact that the Australians had already, from metric wave work, come up with the same temperature, the thing began to fit together. And being in the radio branch and also aware of SIDs and the need of a good solar index, I began to realize that this program was not for galactic work. On top of that I tried looking for galactic emission and none was evident. So here was a really good little program and what to do with it. Just keep it going. [Laughter.]

Sullivan

What are SIDs?

Covington

Sudden ionospheric disturbances.

Sullivan

Oh yes, right. So then you decided that solar was the way to go and what got you onto the thing which, of course, is your whole life career’s work, namely the daily monitoring? This began almost right from the very beginning, didn’t it?

Covington

Not quite. But again this – I don’t know how I became aware of the need of a good solar index. In Ottawa there was a group devoted to ionospheric work. This is Frank Davis, Jim Scott, Jack Mead. And during the War they set up a chain of ionospheric stations in northern Canada and they in turn were stimulated by Appleton and people here in the United States in Washington, the Carnegie Institution. It must have been through a casual conversation of these people – solar control of the ionosphere – we had these sunspot numbers, dark blotches on the sun. [Laughter.] How on earth could the increase the ionization in the ionosphere? Well, with this million and a half degree area of the sunspot, the thing began to come to a head.

Sullivan

Were you talking with any solar optical astronomers?

Covington

None whatsoever. Oh yes, I must qualify that. Because of the Dominion Observatory. They had a solar telescope there – it’s a horizontal type and takes an image of the sun – oh, about 14 inches in diameter. During the eclipse of November they fortunately took a series of photographs of the positions of sun and moon. And it was from these that I was able to find the exact times when the moon covered the sunspot. But other than that.... Oh, a bit more is coming back…. During the War the Dominion Observatory was staffed by quite a senior staff. You see it was wartime conditions and these astronomers were nearing the end of their career, and it was pretty well run down. I hate to use the word, but that’s what it was. And it was Mr. O’Connor who supplied the photographs of the geometrical positions of the sun and moon. Then there was a Ralph DeLury, you’ll find considerable references to rotation of the sun, about the 1920s. It was quite a problem then – he established a reputation. In talking with him, he drove home to me the need to measure the sun’s ultraviolet emission somehow or other. Late in his career he became quite concerned in trying to relate solar activity to growth of trees and flights of birds, weather, etc.

Sullivan

When did you talk to him for the first time?

Covington

Oh, after the eclipse.

Sullivan

But early in ’47, sometime then, you think?

Covington

Well, it was a few days after the eclipse. I went over there.

Sullivan

That’s right, because he’s the one who had the photographs, yes.

Covington

But the discussions lasted for about six months, six months of conversation.

End of Tape 47A

Begin Tape 47B

Sullivan

This is continuing with Arthur Covington on 23rd June ’76. So now when did the daily monitoring program actually begin?

Covington

In February, sometime, of 1947.

Sullivan

And has been continuous until – it’s still going?

Covington

It’s still going. And it’s even multiplied to two stations. One in Lake Traverse, Ontario, and the other in Penticton, British Columbia.

Sullivan

When did that happen?

Covington

The Penticton station occurred in 1964. The ARO station in 1962. In the solar patrol, observations were, of course, taken at the radio field station in ’47 as I’ve mentioned. And we were surrounded by radar developments so that was a real nuisance. I can recall running around the radio field station just asking who had various transmitters on. So in about a year’s time we established a Goth Hill Radio Observatory, about 5 miles away from the radio field station. And that was – Goth Hill was in existence from 1947 to 1962. Goth Hill Observatory, in turn, became polluted with radar interference from the Ottawa Airport and that led to the establishment of the Algonquin Radio Observatory, ARO, at Lake Traverse.

Sullivan

All these years, how many days did you miss per year specifically?

Covington

Oh, at first we took Saturdays and Sundays off – a matter of convenience.

Sullivan

It was not automated then, either?

Covington

No, it wasn’t. But in about two years’ time we began to see the gaps were significant and then made arrangements to continue Saturdays and Sundays. But the real program of continuous observations didn’t start until the IGY [International Geophysical Year] in 1957.

Sullivan

What do you mean by “the real program?” What was the difference before and after?

Covington

The solar program I’ve just taken as incidental. There was always a need to develop new equipment. After the solar patrol was established, we tried a number of experiments – I can’t recall which came first. But one of them was to build a high resolution – a big antenna to get high resolution so that we could pick out sunspots. Well, we went through various stages and finally ended up with a slotted waveguide array 150 feet long. That was in operation around 1950 or so.

Sullivan

1950? Now it was first described here in ’54, I think, in an article with Covington and Broten in Ap. J. [2016 note: Covington, A.E., Broten, N.W. Brightness of the Solar Disk at a Wave Length of 10.3 Centimeters. Ap. J. 119: 569, 1954]

Covington

That’s right. I guess the construction started in 1950, finished in ’52, and wrote the paper in ’54. So that’s a four year undertaking.

Sullivan

And what was the purpose, now? What was your goal to do with this?

Covington

This was to study the radio emission from individual radio sunspots.

Sullivan

Right. And you had a fan beam, I guess?

Covington

Yes, the fan beam as I recall was about 8 minutes east-west and 10 degrees north-south. The slotted waveguide array is probably the longest that’s ever been made.

Sullivan

For any purpose?

Covington

Any purpose.

Sullivan

How did you come upon that? I don’t think anyone else in radio astronomy has made a slotted waveguide array either. Is that true?

Covington

I think it’s not true. I think maybe Swarup has one in India. And the people in Illinois had one. I think Vermilion?

Sullivan

What was that used for?

Covington

Cosmic noise, the Galactic sources.

Sullivan

Really? Before [George W.] Swenson?

Covington

Swenson, yes.

Sullivan

Before they got the big dish, I mean the big hole in the ground.

Covington

Swenson had a parabolic cylinder in the ground where the line feeds were along the top, referring to the line feed –

Sullivan

Oh, the line feed. So that was a feed in that case rather than the actual antenna.

Covington

Well, we’re getting into what’s an antenna.

Sullivan

Well, before we get on that, though, when I was asking how many days were missed I meant just due to electronics failure or something like this. I’m just curious as to how perfect the record is of a flux value at 10.7 cm on each day.

Covington

There came a time when I realized that if the service was to be maintained it would be wise to have duplicate apparatus. So quite early we duplicated everything that we built. And, of course, it’s easier to keep two sets going than one.

Sullivan

Do you have any feel, though, for how many – still, there must be a couple of days that got missed for one reason or another.

Covington

Well after ’57 I think the records are pretty continuous. The technical staff, of course, worked Saturdays and Sundays and arrangements had to be made to compensate them one way or another.

Sullivan

What was the change in the program before and after the IGY?

Covington

After the IGY the solar radio emission was then really accepted as a measure of solar activity. And we started sending our daily flux values to the World Network [World Data Center for Solar Terrestrial Physics], in North America the headquarters were centered in Boulder, Colorado. With this sort of service, outside service, the feeling is somebody depends on you so you take a slightly different attitude towards your work. Prior to that I know I was more interested in building big antennas, improving receiver quality.

Sullivan

So you’re saying that the monitoring for the 10 years, ’47 to ’57, was really just something always going on the side and your main activity was in thinking about building new antennas of high resolution and so forth.

Covington

That’s right. In time – Another factor occurred from about ’47 to ’56. The National Research Council Observatory was the only one operating in Canada. The Dominion Observatory as the senior observatory, a tremendous intense tradition and they became interested quite seriously in wanting to get into radio astronomy. Then there was some need to cooperate. It was quite a difficult period. I don’t quite know how to describe it.

Sullivan

As to how exactly to bring this about, you mean?

Covington

I think, in the case of the National Research Council, the long array which we were using was first 150 feet and them we made it into a compound interferometer by adding two outside dishes and it was 300 feet. At that stage there was the question of whether to make a north-south extension or still to go further east-west. At this time the Dominion Observatory indicated that they wanted to become involved in radio astronomy and a series of meetings occurred between the two institutions, and it was decided to commence a site survey throughout Canada. This was where, in our particular case, Nick [? Pattinson?] got together some radio equipment in a lorry, sensitive receivers, and a number of sites were tested.

Sullivan

What year was this?

Covington

This is ’56, late ’56. The actual field observations were made in ’57. The Dominion Observatory under Jack Locke first used the equipment. They went to Green Bank. It’s rather interesting, I think they took the first radio observations at Green Bank with this portable equipment. This was en route to California. Whether or not they stopped off at John Bolton’s site at Owens Valley I don’t know. But then they went on to British Columbia, and British Columbia, of course, examined in more detail a number of sites.

Sullivan

What was the purpose of going to Green Bank?

Covington

If I remember correctly, Jansky and Bailey had made a site survey for a national observatory in the United States and they wanted to use that site to sort of get a comparative calibration.

Sullivan

They weren’t thinking of putting the Canadian observatory in Green Bank. [Laughter.]

Covington

Well, we often joked about it. [Laughter.]

Sullivan

You were not directly involved.

Covington

No, I wasn’t. At that time I was quite committed in the IGY program so this would be in ’57 and IGY was going in full swing.

Sullivan

What were you doing especially for the IGY?

Covington

There was – making sure the daily flux measurements were made and sent out on this international network. And then we further introduced the practice of looking at outbursts and describing them in terms of type, telling when they commenced, their peak flux, and so on.

Sullivan

I should first ask, the daily monitoring – this was a single new time value?

Covington

The daily monitoring – by this time the equipment had some automatic features so the antenna would start tracking at sunrise and continue until sunset without any person being present. The actual determination of the sensitivity required somebody being present.

Sullivan

Putting a noise tube on or something?

Covington

Putting the black box around the dipole to measure ambient temperature and pointing the antenna towards the zenith.

Sullivan

And that black box was used all the way up until the IGY, you’re saying?

Covington

Yes, and even now the black box is being replaced by a more convenient waveguide termination. We call it a flap attenuator. We’re using a standard s-band waveguide, that’s three inches by one and a half, and there’s a long flap piece of Bakelite covered with carbon which flips in and it ii the (?) black box. This has proven very reliable. I have quoted and still stand by it that the relative accuracy over this period of time, except for the first six months, is about 2.5 percent. And more recently when we’ve had the two observatories going, i.e. ARO and DRAO, I’d say the relative accuracy could be half a percent.

Sullivan

There was another article in the special issue of Proc. IRE in ’58 with Medd [2016 note: Medd, W.J., Covington, A.E. Discussion of 10.7-CM Solar Radio Flux Measurements and an Estimation of the Accuracy of Observations. Proc. IRE 46: 112, 1958] in which you say the earliest fluxes were good to plus or minus 10 percent. And when did they become more accurate?

Covington

After about six months or so, late ’47.

Sullivan

And what was the measurement at that time? That was not tracking all day long, was it?

Covington

No. We would come out to the lab about 9:00 or so, and we’d start the instruments going.

Sullivan

And you’d take a mean of the entire day’s – ?

Covington

Oh, no. The 10 cm emission is quite constant compared to the metric wave emission. Usually one calibration per day is satisfactory. Of course we had to test this. I remember spending a week or two taking observations every hour during the day and seeing that they were pretty constant and realizing one would be sufficient.

Sullivan

The monitoring was only for solar activity then?

Covington

Yes.

Sullivan

I mean the daily tracking was only for activity. OK, let’s look at some of these other papers that haven’t been mentioned. Proceedings of the IRE in 1949 [2016 note: Covington, A.E. Circularly Polarized Solar Radiation in 10.7 Centimeters. Proc. IRE 37: 407, 1949] you say that the quiet sun has no polarization but sunspots have circular polarization. This is apparently a large quarter wave plate that you – Can you tell me about that?

Covington

Oh, nothing much other than it’s a direct analog taken from optical physics.

Sullivan

I think that was the first time that anyone in radio astronomy had done that. Well, maybe Ryle about that time.

Covington

No, I think it would be the first or second. You should look and check and see what Ryle did. He might have used an interferometer with crossed dipoles.

Sullivan

That’s what he did, yes.

Covington

And I think that came slightly before but –

Sullivan

Oh yes. He detected the circular polarization before, but I’m thinking of the quarter wave plate over the antenna was sort of unusual.

Covington

Oh yes, that would be, I think.

Sullivan

He had that in ’46, that circular polarization. And Hey and Appleton also had circular polarization in ’46. In fact there was a third paper – that must be the Australians because that’s all that’s left – they were all together in Nature within two weeks. Now here Covington and Medd in ’49 of the Journal of the RASC on simultaneous observations of eight events at 1.5 meters as well as the 10.7 cm. [2016 note: Covington, A.E., Medd, W.J. Simultaneous Observations of Solar Radio Noise on 1.5 Meters and 10.7 Centimeters. JRASC 43: 106, 1949] Did you set these meter wavelength observations up yourself?

Covington

Well, I was curious to see what the metric wavelengths profile looked like in comparison to the 10 cm. Actually having actual observations in my own hands. Wilf [Wilford Medd] was the first engineer who was working with me. It was one of his first projects. We looked at those simultaneous profiles and I know I realized that an entirely different nature indicated that the 10 cm emission came from one level and the metric from another. And there would be such a wealth of detail in these two regions that it would be wise for me not to pursue the metric wavelength. SO I more or less bowed out of the metric wavelength.

Sullivan

So you decided to stick to microwave. Now what about this Journal of the RASC in ’53 where you talk about the diminution of the 10.7 cm flux after a flare in May ’51. [2016 note: Covington, A. E.; Dodson, Helen W. Absorption of 10.7-centimetre Solar Radiation during Flare of May 19, 1951. JRASC 47: 207, 1953] And you were wondering according to the abstract whether the flocculi might be doing some absorbing. Has this phenomenon been confirmed since?

Covington

It’s quite a rare event but it’s been confirmed. We’ve confirmed it. The Japanese confirmed it after us. The Germans, [Otto] Hachenberg, Heinrich Hertz Institute, confirmed it. It’s relatively rare.

Sullivan

What are the conditions that are necessary, does it seem?

Covington

It seemed as though the flare occurrs, it’s a brightening of a certain level and then later on some dark clouds are ejected and they lie over this bright plage and they’re dense, cooler, and thereby it cut off the more intense emission from the underlying area. Just an illustration of the complexity of a flare event.

Sullivan

In other words, the plasma frequency becomes so high as to not to let the 10.7 cm through?

Covington

Yes, that’s one way of putting it.

Sullivan

You’re talking about the microwave flux goes down, the Ha flux does not diminish too, does it?

Covington

Yes, in the May event it did diminish. In fact, that’s how you can detect that the dark clouds lie over the –

Sullivan

When you say dark you really do mean that.

Covington

They are dark, yes, in this case.

Sullivan

It looks like the first time that you teamed up with some optical astronomers to do some interpretation was in ’53 when you gave a talk at the AAS with [Helen W.] Dodson and [E. Ruth] Hedeman – you talked about the percentage of Ha events with respect to the percentage of radio events and the flare importances, so forth. Is this the first time you had collaborated with them?

Covington

Yes, it was the first time I had collaborated with optical astronomers of that nature. Helen Dodson and Ruth Hedeman are from the McMath-Hulbert Observatory. Previous to that they had collaborated with Cornell University – [Charles L.] Seeger and [Charles E.] Burrows. And they’d sort of exhausted that particular study. And then they became aware of our 10 cm work. And they discussed the whole possibility of coming to Ottawa with Dr. [Robert R.] McMath, and, of course, got his blessing and I was told he was sort of skeptical of radio astronomy. I recall he said, “Make sure those bumps are genuine.” [Laughter.]

So I think it was in February Helen and Ruth came, and I recall meeting them at the hotel. They had two suitcases chock full of optical pictures. And I took them out to the radio field station and sort of set things down. One of the first questions Helen asked me was, “What did you see on May 19, 1951?” And she had observed this darkening of the Ha with the dark cloud lying over the bright plage . So we looked at the radio records and there was the diminution. Up to then I had been aware of the reduction of the radio waves, but being so unusual I was skeptical and didn’t know what to make of it. You see, you just have an isolated event – . I happened to be at the observatory when that was occurring, and fortunately I checked all the equipment and satisfied myself that everything was normal. I was willing to stand by it as it being a good observation.

Sullivan

I’m interested in this because this is one of the earliest examples of a direct joint collaboration between optical and radio astronomers.

Covington

I hadn’t realized that.

Sullivan

Well, if you’ll think about it, there really wasn’t very much, because the optical astronomers were very skeptical. They did not understand the radio technology and so forth.

Covington

McMath’s statement, “Make sure those bumps are genuine.” That’s all he regarded them as, bumps. [Laughter.]

Sullivan

But apparently Helen Dodson, anyway, believed that this was a very useful science, and so forth.

Covington

Yes, she was quite helpful and I appreciate her understanding from the optical side.

Sullivan

She came to you rather than – You did not go out seeking?

Covington

That’s right. It was through McMath. I think Helen approached McMath, of course. And [Edith] Müller is involved in this, the McMath end, as well.

Sullivan

You had an NRC report in ’55 in which you talk about information that can be derived about atmospheric defraction and absorption from low elevation observations which I suppose was just something that you decided. [2016 note: Covington, A.E. Notes on Low Angle Reception of Solar Radio Emission, ? = 10.7 cm. NRC ERB-368, December 1955.] Was this a special program?

Covington

The background of that is interesting. It goes back to the radar aspect. There was a Bill Brown, who was in charge of the radar program, and he saw the radio telescope on top of the building and how it was following the sun. Now he had the task of calibrating boresight of the radar antenna. And he decided that he would use the sun, immediate position of the sun from the almanac. I think as early as ’47, no, it would be a bit later – ’48 or ’49, he was using the sun to calibrate the boresight of an MHF, microwave [high?] finder. And it was quite successful. Well then time went on, a few years, and this was picked up by the Canadian Army. They wanted to know more about the whole radio phenomena of a setting sun. And in response to their request, I wrote and prepared that internal report.

Sullivan

Did this involve special observations?

Covington

Not particularly.

Sullivan

It was things that you already know.

Covington

And it was very practical because the Canadian Air Force was at numerous stations throughout Canada and they had to check the boresight of all these antennas and this was about the only convenient and reliable way it could be done. I think now it’s very common practice for certain antennas.

Sullivan

What about the 1955 eclipse which you have a paper with Medd, [Gladys] Harvey and [Norman] Broten? [2016 note: Covington, A. E.; Medd, W. J.; Harvey, G. A.; Broten, N. W. Radio Brightness Distribution of the Sun at a Wave-length of 10.7 Centimetres, June 30, 1954. JRASC 49: 235, 1955] Can you tell me the story about that?

Covington

Oh, that was more or less prepared. We knew it well in advance.

Sullivan

Was that in Ottawa?

Covington

In Ottawa. It was a partial eclipse.

Sullivan

You’ve never gone on any expeditions to eclipses?

Covington

Yes, we did that in 1963 to a place in Quebec, the Province of Quebec.

Sullivan

Now you said that Medd was your first engineer. Was the group working with you growing during this time or was it always staying -- ?

Covington

Oh, I mentioned the exodus of engineers from the Council [National Research Council] into school into the atomic energy program. Well, I then required two technicians. So they were working with me for a while. Then Medd came. It was growing and then Broten came. He came first as a summer student and majored as an engineer. Then Gladys Harvey. We had (Zotov?). No, not (Zotov?, Markoff?) He only stayed a year or two. And by 1954 and ’55 we were quite a small group, four professionals and three or four technicians. At one time, I guess it’s worthwhile to mention, during the Korean affair, Medd was assigned to some radar development and the NRC nearly closed down the radio astronomy. I had a stubborn streak and refused to move, so we hung on. But after that it grew some more.

Sullivan

But there was no other radio astronomy until Penticton got going in Canada, is this correct?

Covington

Pretty well. There was a group over in Defense Research Board, Ted Hartz. I’m not quite sure what he started.

Sullivan

What did he do?

Covington

He was monitoring the scintillations from Cassiopeia and the absorptions of cosmic noise due to the SID effect.

Sullivan

H-A-R-T-Z?

Covington

H-A-R-T-Z.

Sullivan

I don’t know his name. And this was about what time?

Covington

’54 to ’55. Ted Hartz, in the history of radio astronomy, I think stands out and should be checked – Canadians had the Alouette satellite and they took some of the first radio astronomy observations from the satellite.

Sullivan

When was that satellite sent up? Roughly, once again.

Covington

’65? I should know.

Sullivan

Mid-‘60s sometime.

Covington

Yes, mid-‘60s.

Sullivan

OK, I’ll check into that.

Covington

Yes, I would check that. It’s a significant observation. I remember being at meetings discussing the whole thing.

Sullivan

Well, we got sidetracked from talking about your Proceedings of the IRE in 1948 paper in which you established the 27 day periodicity. [2016 note: Covington, A.E. Solar Noise Observations on 10.7 Centimeters. Proc. IRE 36: 454, 1948.] This must have been quite exciting to find this, that the monitoring was really worthwhile and so forth. In terms of showing something. Were you learning a lot about the standard solar astronomy all this time in the process, or were you just – I’m trying to get at how you went about trying to interpret all this.

Covington

At that period I remember [Joseph L.] Pawsey came through. I’ve been trying to place this visit. You said it was ’47 – I guess we learned our astronomy in sort of an amateurish way. We were really more interested in radio technology. Joe Pawsey, of course, was an ionosphere man and he and the Australian groups had pretty well set the theory. As a radio engineer you sort of pick up these things quickly and you don’t worry too much about them. So I think I wasn’t too excited about the –

Sullivan

Well, what really did turn you on then as a result.

Covington

The building of the big antenna. Getting after high resolution.

Sullivan

But you must have had great dedication, though, to keep this monitoring going. That doesn’t mean it’s exciting, of course. It’s just sort of a service, is that the way you were looking at it?

Covington

Yes, the dedication came much later. The solar patrol even in the group it was something you do. [Laughter.] Like keeping house. Looking back now I wish we’d been a little bit tidy.

Sullivan

Well could you summarize briefly what you feel – it’s been almost 30 years now of monitoring, what that monitoring has mainly shown in terms of solar physics?

Covington

One thing, I hope and I think will happen, is it will provide a very precise measure of solar x-ray ultraviolet emission. And if the technology were pushed a little bit you can get down to a tenth of a percent accuracy. And this is far more than any optical observatory can do. Well, the satellite observatory. And even though some people don’t like saying it’s the next decimal place but when you look back over the history of science, the next decimal place is usually many times. The discovery of argon and so on. The work I’ve done I think can be summarized in perhaps three areas: the provision of this index, which is pretty well recognized. I was also puzzled over the burst profiles, the dynamics of flares. Yes, you’re bringing back memories. I can remember spending months looking at these burst profiles and thinking of mechanisms, how regions can decay. Not very profound, but they intrigued me.

Sullivan

I don’t think you published very much along these lines, did you?

Covington

Well, yes. There was an international symposium in Paris in 1958. And there’s a paper in there. [2016 note: Covington, A.E. The solar emission at 10-cm wavelength. IAU Symp. 9: 159, 1959] That paper was produced under great stress and very quickly – in two weeks, I think. In less than two weeks I produced it. And somebody has referred to it as a classic. [Laughter.] I was surprised.

Sullivan

But in the Journal of the RASC in ’58, also, you talk about there are two basic types of flares: thermal and nonthermal.

Covington

Yes.

Sullivan

And this must have come from studying the burst profiles also?

Covington

Yes. That intrigued me more than the solar patrol nature. And, of course, the development of high resolution antennas that led to the compound interferometer.

Sullivan

You haven’t told me about actually building the compound interferometer.

Covington

Oh, I think that would be another stage. [Laughter.]

Sullivan

That was in the mid-50s?

Covington

’54, after ’54. In ’54 I made a trip to England and the continent. It was to attend the URSI General Assembly at The Hague, and there I realized that Lovell’s big dish was about to be completed and that if we could do something with our slotted waveguide array and using the strong source as the sun, we could probably get some high resolution that Lovell couldn’t get. And so that was part of the realization of the creation of the compound interferometer.

Sullivan

I see. Although he in fact never did any solar work with that dish.

Covington

No.

Sullivan

But you didn’t know that at the time?

Covington

I was just more anxious in getting the resolution.

Sullivan

What came out of the compound interferometer in its extension? Did this high resolution pay off?

Covington

Yes. At the Algonquin Radio Observatory we now have a 32-element array which is 600 feet long and produces a fanned beam of 1.5 minutes of arc and we are now taking daily transits of the sun.

Sullivan

I see. Thirty-two small dishes?

Covington

Thirty-two dishes in a row.

Sullivan

Well, what about these in the ‘50s, these compound interferometers. What did they tell you about the nature of the burst in active regions and so forth?

Covington

Well, it gave us the equivalent temperature of the sunspot which more or less verified the eclipse observations, and the east-west dimensions, a few minutes of arc. Again, that more or less verified the eclipse observations. We did notice that on the edge, on the limb of the sun the radio spots were point-like so this would imply that the emitting surface was a plate-like structure that lay on the solar surface.

Sullivan

I notice that back in 1960 you have a paper in the Bulletin of the Radio Electronic Engineering Division of NRC, Covington, Legg, and Wong proposed an array of 10 foot dishes for Algonquin which I guess is what you just described.

Covington

Yes.

Sullivan

It’s grown out of that. This is 1960, however. When did this finally get built?

Covington

That was when the idea was conceived and it was finished in ’66. So that was a six year program. There are actually four stages proposed in that antenna and we only finished two of them. We were running short of manpower and money so the full potential of the ideas are not available. It’s interesting to realize that the Japanese, the University of Nagoya, [Haruo] Tanaka, have picked up this idea and they have really exploited it. The final step is to connect a computer to the antenna and data process the information, taking out various errors, and produce a map of the sun.

Sullivan

A daily map of the sun?

Covington

Yeah. But we have a two-dimensional map of the sun.

Sullivan

Well but now, how would this be superior to Bracewell’s array? Is this not similar?

Covington

It’s quite similar. The Japanese are using a T. Bracewell has a cross. The compound interferometer eliminates some of the redundancy and makes use of – trades that off to gain resolution. When you reduce – eliminate the redundancy then you have to desirably use a computer to process the information to have everything absolutely perfect. And there’s no redundancy. Things have to be perfect.

Sullivan

Right, everything counts. One final thing. We haven’t talked too much about your work, well somewhat, about your work relative to other solar work going on. Other monitoring programs and so forth. When was the first other additional monitoring program? Until the IGY, was that the first time?

Covington

Yes, I think the IGY brought in many observatories. And after three or four years they sort of dropped out and got into other areas of activity. I guess I was left holding the bag. [Laughter.]

Sullivan

But you were the only one before then that was doing microwave monitoring?

Covington

Well, the Naval Research Lab commenced 3 cm work first. Then later extended it to millimeter work.

Sullivan

Right. But they never really monitored –

Covington

Yes, they monitored the sun. I can recall inter-comparing our 10 cm records with their 3 cm records. This was through Fred Haddock. I think they never really published anything. It’s a good case, you know, many institutions have a backlog of good ideas which have never been published. More recently the Air Force at Cambridge picked up the solar monitoring and they are carrying it to a number of frequencies.

Sullivan

That’s quite recent though – the last five years or something like that?

Covington

’65. ’66 I think.

Sullivan

Well I think that pretty well covers what I wanted to talk about unless you can think of some comments that haven’t been touched upon.

Covington

I realize looking back now there have been a lot of ramblings, sort of free associations and any one of these could lead to further interesting stories.

Sullivan

When was the first time that you actually – well the first time you talked with the optical astronomers was with Helen Dodson, apparently. Well, that’s right after you did that solar eclipse.

Covington

Lurie. And then the second time would be Helen Dodson.

Sullivan

But it was even after that, before you were presenting your results to astronomers at astronomers’ meetings. You were usually going to URSI meetings and things like this.

Covington

Well that’s quite true. It’s interesting that after the War the URSI meeting, the spring URSI meeting was held in Washington. This would be ’47. And at the meeting I can recall speaking to Reber and Jansky, quite a thrill looking back. Jansky, of course, at that time was not working in radio astronomy but was working on receivers, I think, or something.

Sullivan

Low noise receivers, yeah.

Covington

But he came down to the meeting and he read an abstract and he wanted to see what was going on. Other people I met at that meeting was John Hagen, Haddock from NRL, Alan Shapley of Central Bureau of Propagation [Central Radio Propagation Laboratory, National Bureau of Standards]. He was concerned with providing a warning service for radio circuits. There was another person, J.F. [Jean François] Denisse from France. He was theoretically inclined, and I know he picked up my observations and made extensive use of them.

Sullivan

Right, he had a big thesis, in ’48 or so.

Covington

Yes, in fact I think it would be the first thesis in radio astronomy.

Sullivan

It well might be.

Covington

And the people at NRL [Naval Research Laboratory] translated it.

Sullivan

Yes, that’s right. I’ve seen that translation. Is there any point where you can sort of say, “Well, at that time I began talking to astronomers more than I did to radio engineers?” Does this strike you as a valid question at all?

Covington

I’ve been pretty well more with radio engineers than astronomers. The galactic astronomers are way out there.

Sullivan

Well, thank you very much. That ends the interview with Arthur Covington on 23rd June 1976.

End Tape 47B

Citation

Papers of Woodruff T. Sullivan III, “Interview with Arthur E. Covington ,” NRAO Archives, accessed July 31, 2021, https://www.nrao.edu/archives/items/show/14593.