[Cover of Sullivan's book 2009, Cosmic Noise]
Sullivan's Cosmic Noise, Cambridge University Press, 2009


NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Norman W. Broten
At URSI Meeting in Helsinki
7 August 1978
Interview time: 42 Minutes
Transcribed by Sierra Smith

Note: 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 Smith in 2016. The transcript was reviewed, edited/corrected, and posted on the Web in 2016 by Ellen N. Bouton. Places where we are uncertain about what was said are indicated with parentheses and question mark (?).

We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web. 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.

Click start to listen to the audio for tape 111A of the interview.

Begin Tape 111A

Sullivan

This is now talking with Norm Broten on 7 August í78 at URSI in Helsinki. Could you tell me first of all what your educational background was and when you first came in contact with radio astronomy?

Broten

Well I have a BSc in radiophysics. And it was during a summer job at the National Research Council that I came into contact with radio astronomy. And I worked for a summer for Mr. [Arthur E.] Covington.

Sullivan

In Ottawa?

Broten

In Ottawa, in the solar radio observatory with the work he was doing there. I guess that started me off. I got intensely interested in it. And I went to work there after graduation with a BSc.

Sullivan

That would be what year?

Broten

1950.

Sullivan

1950? Oh, I see. So you were there four years before this first publication here, in radio astronomy the science anyway?

Broten

Thatís right.

Sullivan

What did you work on those first few years?

Broten

In the first few years, I worked on instrumentation to improve the equipment, which was always very marginal being old radar equipment and that. And it gradually developed up into something more reliable.

Sullivan

And what were the primary needs for solar radio astronomy instrumentation at that point?

Broten

Well, solar microwave radiation at 10 centimeters, which incidentally has been going continuously since 1947, and is the longest continuous series of solar radio records with high accuracy and I suspect will replace the Zurich sunspot numbers as the index of solar activity, requires reliable instrumentation which can operate continuously without any problem.

Sullivan

So reliability was of more concern to you that the usual radio astronomy? You always want to be reliable, of course, but it was even more of a concern to you.

Broten

Reliability and accuracy. You had to make sure that everything was very (?), yhe results would carry on from one epoch to the other.

Sullivan

Well just bringing up that point of accuracy, in fact, I interviewed [Haruo] Tanaka a few days ago and he was talking about their monitoring effort versus the Canadianís. And that both of them showed the same long term changes but that there was a 10% sort of difference. And his claim was that indeed the Covington group was off by 10%. Do you agree with that in terms of these values through the Ď50s?

Broten

I think youíd have to ask that question of Mr. Covington. [laughter]

Sullivan

You havenít kept up with it?

Broten

My feeling is that the Ottawa records are pretty reliable, but there is a slightly frequency difference between Tanakaís measurement, the solar measurement, and the Ottawa measurement. And there may have be a spectral difference in this.

Sullivan

Yeah, well, 10%, of course, is a very small amount, nevertheless.

Broten

The Nagoya measurements at 3700 agree much better with the Ottawa records than the Tokyo ones. So there is some difference in (??).

Sullivan

Ok, well, that was just an aside. But as you were working on the instrumentation, apparently you became interested in the astronomy also. And what were your main interests in solar radio astronomy?

Broten

Well, 1954 we had operating the first instrument which was capable of resolving the Sun at 10 centimeter. We put into operation a 150 foot waveguide array which had a beam of about 8 minutes of arc. And so we were able with that to get our first, if you like, synthesis of what the solar temperature was from the strip scans on the Sun. And about the same time that Christiansenís group in Australia introduced their 21 centimeter measurements on solar distribution -

Sullivan

Did these give similar results?

Broten

Yes, quite similar. There is a wavelength difference between 21 centimeter and 10 centimeter and their brightness temperature is a factor of 2.5 and so higher than what the 10 centimeter one is. As you would expect because you are higher in the solar atmosphere.

Sullivan

I meant in terms of the qualitative distribution of the Sun, for instance limb brightening?

Broten

Oh, yes. Essentially what was predicted from the theory of limb brightening, limb brightening increases as you get into shorter and shorter wavelengths. And, in fact, it really becomes noticeable down in the millimeter and centimeter wavelengths.

Sullivan

But you did detect it with -

Broten

We do detect some limb brightening and a falling off at the polar regions, yes. Limb brightening on the equatorial, yes.

Sullivan

Another note I have here from the abstract is the equator was found to be brighter than the pole.

Broten

Yes, thatís right.

Sullivan

Now how could you determine that? Did you have a north-south fan beam?

Broten

No, it was an east-west fan beam. Of course, the Sun does change its inclination with time, plus or minus 26 degrees, which gives you some resolution that way. And itís a modeling technique that has to be used in anything like this. And we divided the Sun up into segments to fit our results.

Sullivan

I see. Where did the idea for a slotted waveguideÖ as far as I know still is unique in radio astronomy?

Broten

Well, the idea came from World War II, where a slotted waveguide arrays were used for radar and the National Research Council developed this early in the 1940s for World War II.

Sullivan

I see. Were you part of the wartime radar?

Broten

No, I wasnít. I was in the Air Force overseas at the time. But it was just an extension of that into something very much bigger and longer for a solar work, which was carried on by Mr. Covington, who perhaps instigated it, but the chap who did the work is now off at the University of Syracuse.

Sullivan

Who is that?

Broten

Dr. Harry Bloomberg.

Sullivan

Bloomberg?

Broten

Yeah.

Sullivan

But is it not true that I donít think anyone even since has used slotted waveguides?

Broten

No, that is true. They are fairly complex to build to get any degree of resolution. And they have no gain in ascension in the north-south dimension. They were just radiating out from slots. Itís perhaps much easier to build interferometers, which was our next step. To add on this slotted waveguide array, four parabolic cylinders each with slotted waveguide feeds, to give the same (?) angle as the other end. And then form, what we call and has been called since, a compound interferometer.

Sullivan

And this wasÖ now it said it gave you a 2 arc minute by 2 degree beam in the abstract. I guess the 2 degrees now, was the limitation due to the small dishes.

Broten

2 degrees is the north-south resolution of the small parabolic cylinders. They werenít dishes. And 2 minutes is the resolution we got from extending our our compound system.

Sullivan

And what did this enable you to find out about the Sun?

Broten

It confirmed, of course, what had been found with the 8 minute of arc slotted waveguide array, that the radio plage, radio emissions were associated with plage areas of the Sun, which were overlying sunspots regions. It enabled us to get better resolution on the limb and see radio spots emerging before they are optically visible. I suppose that is the major sort of contribution of that resolution. In fact, the array has since been extended into - not with the slotted waveguide, but an array of dishes up at Algonquian now where we have an interferometer, which has 1 minute of arc by 2 degrees. And it takes daily strip scans of the Sun, which are published in the Quarterly Journal of Solar Activity.

Sullivan

How long has that been going on?

Broten

Thatís been going on since about 1966-67.

Sullivan

Since about when the big dish -

Broten

About the same time, yeah.

Sullivan

Why was it was that your resolution went fromÖ you had 8 arcminutes with the 150 foot slotted waveguide and 2 arcminutes with the compound interferometer?

Broten

Thatís a feature of the compound system, which is what Mr. Covington and I pioneered at that time. If you add on another element of the same length and you multiply the two together, you get the interference between the phase centers of the two elements, which now gets you twice the resolution if you just had that same aperture. Extending the array by another 150 feet gets you 4 minutes of arc.

Sullivan

I see. And then you get the doubling effect -

Broten

By taking them separately and then multiplying all through the phase centers you get 2 minutes of arc. That principle is still used. Itís being used by [Wilbur Norman ďChrisĒ] Christensenís group in Australia in the first (?). Stanford has used it in their array before they closed it down. Weíve done some work on our array in Algonquin whereby we get 15 seconds of arc resolution, a compound system.

Sullivan

So this was the first compound interferometer?

Broten

This was the first compound interferometer.

Sullivan

Are there any special difficulties with operating it when you have such different kinds of elements?

Broten

Yeah, there are special difficulties in any complex antenna system. And the particular one in this one is to keep all the phasings right and all the phase lengths right and so forth. If your antennas get somewhat off phase, you get phase errors in the system and patterns which arenít nice, sine over x patterns.

Sullivan

But more so than a regular interferometer?

Broten

Yes, more so than a regular interferometer.

Sullivan

And why is that now?

Broten

Because you are multiplying two phased antennas together. If the phase between them slips a little bit -

Sullivan

Itís more critical.

Broten

Yes. And then it slips around from being sine x over x.

End Tape 111A

Click start to listen to the audio for tape 111B of the interview.

Begin Tape 111B

Sullivan

Continuing with Norm Broten on 7 August í78.

Broten

These systems form the basis of smart arrays, you know, which are used in radar.

Sullivan

In what sense now?

Broten

Well, smart arrays in radar are ones in which the antennas scanned or formed, made to follow something. Well the compound system is part of this system and then by changing the phase between different antennas, you can now make one scan and then it (?) to follow targets.

Sullivan

Did you know about this sort of thing? Was this sort of thing going on in the military at that time?

Broten

No, I think this came after.

Sullivan

Let me just ask this as an aside while it occurs to me. Is it not true that Canadian radio astronomy has never been funded by the military?

Broten

That is correct.

Sullivan

You know, American radio astronomy has had so much input, at that time anyway.

Broten

There has never been any military funding in radio astronomy.

Sullivan

Itís all been through your National Research Council?

Broten

Yes. Almost all. There has been a little bit of work done at a place called the Defense Research Board by a fellow by the name of Ted (?) and Ted Hartz.

Sullivan

Hartz?

Broten

Hartz, H-A-R-T-Z, who was funding by the Defense Research Board, which was effectively a military establishment.

Sullivan

But that was a very minor.

Broten

That was a very small matter, a very small amount, yes.

Sullivan

Alright, now was there any other solar work that you were involved with that we should cover? I donít see anything else here in the abstracts.

Broten

There were some solar eclipses.

Sullivan

Oh, yes. Thatís right. In June í54, there was one here mentioned. Were there any expeditions that you went on? Or were they just the ones that happen to come over?

Broten

No, I didnít go on any expeditions. Although Mr. Covington took his equipment off on a solar eclipse expedition in Quebec. But after the Algonquin Radio Observatory was established we had there operating a 10 meter antenna, which Dr. Higgs and I fitted out for 6 centimeter operations - 5 centimeter operation it was, with a scanning beam in which we scanned continuously around the limb of the Sun and watched the Moon bite into it.

Sullivan

I see. What size antenna was this?

Broten

It was 10 meters.

Sullivan

What year was this?

Broten

This was 1953, I think it was.

Sullivan

But I thought you said that you took it to Algonquin.

Broten

That was at Algonquin. 1963.

Sullivan

Oh, 1963.

Broten

Yeah, 10 years later.

Sullivan

Ok, well, speaking of Algonquin, here you have a paper with (Pattenson and Aiken?) in í58, in which you were doing a site survey for the Canadian National Radio Astronomy Observatory. Could you tell me how this concept came up and then how that developed? The concept for a national observatory.

Broten

Yes. Well, the concept of a national facility had been growing for some time. Prior to this time the need for a national facility was evident. And, a couple of us (?) the fact that our solar observing site near Ottawa was being swamped more and more with both military and airport radars. And so, it was evident that we were going to have to change sites for the solar work as well. So two concepts kind of coupled together. With the permission of the National Research Council, we set out to establish a site for a national facility.

Sullivan

Was there any push to get into non-solar work also?

Broten

Yes. The push was there. For some years the funds werenít.

Sullivan

Who were the people that were interesting?

NBL: Well, myself chiefly and to a certain extent Mr. Medd.

Sullivan

And another question is, did the optical astronomers have any role in this or were you pretty well distinct from them?

Broten

At this time, we were distinct because at that time government astronomy in Canadian was operated under two branches. One was the National Research Council, which all the solar radio work was done under. And about 1960, í61, also was the establishment of the Dominion Radio Astrophysical Observatory at Penticton under Mines and Technical Surveys, or something like that. The government astronomy as a whole had been done under a department similar in name to the Mines and Technical Surveys because of the support that the survey people gave to Canada as a whole. And the Dominion Observatory was formed as part of that. And then later on -

Sullivan

In Victoria?

Broten

At Ottawa.

Sullivan

The Dominion Observatory in Ottawa.

Broten

Yes. And then later on the Dominion Astrophysical Observatory in Victoria was formed and operated by the same department. In 1970, I believe, the government transferred responsibility for all astronomy to the National Research Council.

Sullivan

Now but Dominion Observatory and DAO had been around for a long time, had they not?

Broten

Yes, yes.

Sullivan

But you were in not particular contact -

Broten

I was in contact but not -

Sullivan

But not in close cooperation or -?

Broten

Thatís right.

Sullivan

Not even with the solar optical astronomers?

Broten

To a certain extent. It was somewhat limited because by this time the site at Ottawa, the Dominion Observatory, had more or less ceased to exist function as an operating observatory, except for the (?? tubes?) and transit.

Sullivan

For reasons of interference also, I suppose?

Broten

For reasons of light interference.

Sullivan

In fact, if I remember correctly from Covingtonís papers primarily, I think you may have had good connections with the University of Michigan optical -

Broten

Yes. Helen Dodson and the people down there, yes.

Sullivan

In general, let me ask, when you talked about solar work in the radio, were you talking with the solar optical astronomers or was it pretty much talking to other radio astronomers? Which did you feel more a part of, which community?

Broten

Pre-1960s, I think radio astronomy as a whole was isolated from the optical. In fact, URSI used to be the only place in which radio astronomy papers were given. They were not accepted at the American Astronomical Society. So I think that it really wasnít until the more galactic work was done that radio astronomy became accepted as a branch of astronomy. It was really considered as an (offshoot?). Reber couldnít get his stuff published really through -

Sullivan

Well, letís be fair now, he did get it published in ApJ, even in the early 1940s.

Broten

Thatís right. But he didnít really get much attention from the -

Sullivan

No. Now you say you couldnít give a paper at a AAS meeting. Do you have some personal experience with that or are you just saying that no one bothered to go to these meetings?

Broten

No one bothered because there werenít any radio astronomers going to them. So there wasnít any point in giving a paper there.

Sullivan

One exception I do know about though is the hydrogen work done at Harvard. [Bart J.] Bok, of course, (being a traditional astronomer?). They did give papers. And I think otherwise (???). [Voices obscured by background noise]

Broten

We gave more papers at URSI than at the AAS.

Sullivan

Well, going back to the site survey for the Canadian NRAO, can you tell me what your requirements were and where this lead you in terms of the site?

Broten

The same things as the requirements for any radio astronomy observatoryóisolation from interference.

Sullivan

But was it important that it be in eastern Canada, for instance?

Broten

Not essential that it to be in eastern Canada but western Canada was being served by the Dominion Radio Astrophysical Observatory, in effect. And therefore it was more logical to try and establish one in eastern Canada near the large universities in Toronto and Queens.

Sullivan

And especially since you have quite a bit of wilderness in Eastern Canada. But Iím still a little bit confused. Why not just put this thing at Penticton, unless it is a matter of convenience? You are establishing an observatory there about this same time.

Broten

Well, I think that is partly political in that, you know, Canada is a pretty big country and to try and travel back and forthÖ Travel was even more even more difficult in those days. And the politics of it was such that it was probably easier to get money to establish something which would be of service and of usefulness to the eastern universities, which are large, rather than to put it in the west again. There was one in the west which was established a year before the Algonquin one. At least the site survey was approved a year before. And so really probably more of a matter of politics to establish one in the east, just as you have a fairly large observatory at Caltech and you have one at NRAO in the United States.

Sullivan

Sure. But whatís different is that both of these in Canada are national in some sense. At least one is called Dominion and the other is called National.

Broten

No, the Dominion Radio Astrophysical Observatory is not -

Sullivan

Oh, I see. Maybe that is my misunderstanding.

Broten

- a national facility.

Sullivan

Despite this name which would tend to make it look like itís for the entire Dominion. Is it really more like the Naval Research Lab in terms of itís a government funded thing and outsiders donít really have access to it unless they know the people?

Broten

Well, outsiders do have access to it but by nature the type of instrumentation is more long term program type of thing than it is a short term program.

Sullivan

Visitor-oriented in a sense.

Broten

Visitor-oriented ones come to the Algonquin.

Sullivan

Now, was this the concept right from the very beginning?

Broten

This was the concept from the beginning.

Sullivan

And this is also about the same time that NRAO was beginning to get going in the late Ď50s. Were there any contacts there as to -

Broten

Oh, yes, oh, yes.

Sullivan

- to try to learn from each other about how to do this? Of course, neither of you had a model of a previously existing national observatory. This was rather different from the British and Australia style. Well, another question that pops to mind is that in the U.S., as you are probably aware, there was some opposition from the universities to an NRAO because they felt it would be taking funds away essentially and they were rather dubious about the value. It seems like from what you said that it wasnít that way in Canada.

Broten

No, I think they wanted because funds for continuing programs, funds for developing major instrumentation is much more difficult to get in Canada for universities than it is for a government agency. If you can get a development grant to build something, the funds for continuing the operation of it are something which arenít covered under that development grant.

Sullivan

Once you get your foot in the door -

Broten

The university then has to see where to get the funds for this. And to apply year by year for operating funds for something is not very good. So I think that they were happy and pleased in that sense that the National Research Council could provide this. And the University of Toronto always had a very firm interest in the Algonquin Radio Observatory, right from the very commencement of it.

Sullivan

Was that the primary university that was pushing for it?

Broten

Yes.

Sullivan

What were the others?

Broten

Queens University was also pushing hard at Kingston, but to a lesser extent at that time than right now, although they have turned out to be a major user of it.

Sullivan

Okay. Well, having located the Algonquin site, you just mentioned before that you moved up some solar equipment to use it right away. Do I have that right? And that was in what year?

Broten

1960 it started, January 1960.

Sullivan

And what was the plan at that stage for the big dish? What were your goals?

Broten

Well, our goals were for a dish on the order of 150 feet in diameter. And that being sort of the diameter where we thought we could get funds for. Although we were somewhat concerned because of the problems that they had had with the 140 Foot at Green Bank.

Sullivan

Were having.

Broten

And were having at that time. We were encouraged by the very great success which was evident at the CSIRO, the Parkes Antenna. And so we, in fact, opted for going back to the same designers.

Sullivan

Freeman Fox?

Broten

Freeman Fox, since they had achieved something at Parkes which was quite successful. And we went back to them and asked them to design us a radio telescope.

Sullivan

And in what respects does the 150 Foot differ from the Parkes dish? Or is it quite similar?

Broten

Well similar in many (?) ways but it differs from any other radio telescope in that the surface, which is quarter inch plate over 36 meters of it, interacts with the ribs. It forms part of the support structure. So that it is different in that fashion. It is different in as much as we had specified as our (?)ó 10 centimeters over 150 feet and 3 centimeters over 120, whereas the Parkes was only specified for 21 centimeters over 210 feet. In fact, we used the whole 150 feet at 3 centimeters and other portions down as far as 1 centimeter.

Sullivan

You have in recent years?

Broten

Yes.

Sullivan

So was this the first time that a dish had been sort of designed for an intersection to have somewhat higher accuracy? Or were you just saying that because you had a somewhat smaller dish you had could push it up to shorter wavelengths?

Broten

I think that would be a fair statement to say, and yet it may not be because Parkes had in mind using the inner 17 meters of their dish at a higher frequency.

Sullivan

Which, of course, they are still working on.

Broten

Which they are working on, and have achieved excellent success. But Parkes and our dish certainly would be the first ones in which they had the concept of better resolution. All the way one recognizes gravitational distortions were towards the edge of the dish (???).

Sullivan

Well, the dish you said got on the air in 1966 or so, so there was a period of six years in there. Did everything go relatively smoothly? Or what were the troubles or highlights during that period of building this facility?

Broten

There were essentially no problems in building (??? the radio telescope?). We had operating at the site a 10 meter telescope on which some work was done. And after the original specifications and the initial design of the 150 foot, the 46 meter was complete, I spent two years in Australia doing some research and came back about the time the dish was ready for some of its commissioning.

Sullivan

I see. Which two years were those?

Broten

í63-í65.

Sullivan

So you were working with the new Parkes dish, I suppose, primarily?

Broten

Thatís right.

Broten

What kind of work?

Broten

What kind of work - Magellanic Clouds, polarization of the Galaxy at 600 MHz, some 30 MHz observations, and 5 centimeter observations of the Galactic center.

Sullivan

30 MHz? Using what for an antenna?

Broten

The Parkes dish.

Sullivan

The Parkes dish? Good lord! [Laughter]

Broten

On that I did 30 MHz. The major work which I did there was probably the Magellanic Cloud, the 10 centimeter survey of the Magellanic Cloud.

Sullivan

But this was more or less getting geared up and waiting for the Algonquin dish to get ready, I guess?

Broten

In essence, yes. I felt that I would like to do some research at Parkes and at the same time perhaps become familiar with the problems that Iíd have with that telescope.

Sullivan

With a large antenna, yes.

Broten

And therefore get some knowledge of the problems we might have with our own.

Sullivan

And once the antenna was turned over more or less to the radio astronomers, did it operate quite well? Were there any particular problems?

Broten

No, there were no -

Sullivan

It met the specs?

Broten

It met the specs.

Sullivan

Just like the Parkes dish in other words? Freeman Fox delivered again.

Broten

There were no problems.

Sullivan

Now there is one other topic which we should talk about that just occurred to me. That is, you were involved, were you not, in the first successful VLBI in Canada. So I would like to hear in closing about that effort. How did this idea come about, and could you just tell me the story?

Broten

The idea had a germ back in 1961, I guess it was, at the opening of the Penticton dish. And at the same time Canada had a radar station operating at Prince Alberts, Saskatchewan, about 1000 kilometers away from Penticton. And at the opening of this Penticton dish there was a suggestion that the Penticton dish and the Prince Albert dish might be used together as an interferometer, although a very basic suggestion. And the concepts had not been worked out. In fact, any thoughts were perhaps faulty at that time. And it lay there dormant for a number of years.

Sullivan

Excuse me, but the idea was that there would be independent recording of the signals and then later combination?

Broten

Yes, yes. The idea lay dormant then until about 1965, about the time I returned from Australia. And Iím not too sure who sort of started it again, Herb Gush from the University of Toronto, Alan Yen or Dr. Locke. But I met with Dr. Galt at Penticton on my way back from Australia and he says, ďHave you heard anything about the idea of doing long baseline interferometry?Ē I said, ďNo, Iím just coming back.Ē So he briefed me in it and then we joined in with the group in October of í65 to supply some funds and knowledge and manpower.

Sullivan

You say we joined in?

Broten

The National Research Council.

Sullivan

I see. It had not been previously involved.

Broten

Well, there hadnít really been anything concrete done. The first organizational meeting was in October í65, just a general discussion between ourselves. Of course, some discussion had gone on before I came back from Australia between, I think, the Penticton group and the University of Toronto group. It hadnít really gone too far at that stage and none of the concepts had been worked out. The National Research Council then supplied almost all the money for putting the long baseline interferometer together, a good deal of the manpower in terms of our engineers and our astronomers, too. So we had a fun two or three years getting it going.

Sullivan

What was the key that made people think about this? Was it all of a sudden the availability of rubidium oscillators or - ?

Broten

No, no. The experiment could have been done 15 years before.

Sullivan

15?

Broten

Yes. The key really was the discovery of sources whose amplitude fluctuations were short duration. That is to say, sources that varied on the order of a few months and therefore had to be very small diameter cores.

Sullivan

I see. So you mean in the Ď50s no one would think that there would be milliarcsecond sources?

Broten

Thatís right. No one dreamed that there would be anything (milliarcsecond sources on the order of months or weeks of diameter?).

Sullivan

And so these microwave short periods of variation that were discovered around í65, í66, youíre saying were the - ?

Broten

The (?), yes.

Sullivan

But now, fill me in. I didnít realize that technically this could have been done so early.

Broten

The tape recorders we used were traded-in CBC video tape recorders from that theyíd had for ten or 15 years. The hydrogen masers we used for the last of the (???) were experimenting with. They had hydrogen masers going before that. Rubidium clocks had been around for about 15 years. So the whole experiment could have been done before.

Sullivan

I didnít realize that. So it was really mainly the astronomical knowledge that tipped it off rather than the techniques.

Broten

Well, certainly the idea of how to put these techniques together required a bit of work and a bit of thought, you know, how to do it. But the need for doing it was not really evident before.

Sullivan

Or might one say that one also had to have the experience primarily at Jodrell Bank and somewhat in Australia, moving on to longer and longer baselines and - ?

Broten

Yes.

Sullivan

- and still getting fringes?

Broten

That was Jodrell Bank that did that. It wasnít Australia at that time. Yeah, there is certainly some of that but, of course, I think the clue to anyone thinking in terms of this was the fact that sources were varying in the order of weeks and months in intensity. No way could we do this if they were very large sources.

Sullivan

Yeah, yeah. Well, tell me in terms of the actual observing, once you had put together a system, did the fringes just fall out?

Broten

We had our problems, like the American group did.

Sullivan

Were you knowledgeable that they were going on - ?

Broten

Yes. Ken Kellermann and I were in weekly contact with each other, finding out what our status was. It was a very friendly rivalry going on between us. And, yes, we had some problems in getting it operating. And we opted to go for the whole distance between Algonquin and Penticton to start with, after having done an experiment on site between the 10 meter dish and the 46 meter dish, just separated by 200 meters. And so we went out to Penticton and played the tapes back and got nothing. And so we got a little worried about that so we then pulled our tape recorder and oscillator back to Ottawa, some 186 kilometers, and got all kinds of stuff. And essentially the same sort of thing happened in the United States. They got fringes to NRL but they didnít get any -

Sullivan

From Green Bank, right.

Broten

They didnít get any fringes to Arecibo. Well, we went back to our tapes we had taken and played them and finally discovered that what we had was a very small time jump in recording, a few microseconds. And so our correlation wasnít at the spot we thought it was. And we did that and then found our fringes loud and clear.

Sullivan

I see. So you werenít searching assuming different clock errors?

Broten

Oh yes, we searched but it isnít quite the same, you know.

Sullivan

Yeah, when you really know where you should be looking, you look hard.

Broten

Our techniques were more rudimentary at that time. We didnít do quite the same we do now.

Sullivan

And I suppose that when you obtained the fringes on the short baseline and not on the very long one, you werenít sure whether youíd resolved the source or something hadnít worked also.

Broten

There are always these possibilities, yes.

Sullivan

But was there any attempt then at an intermediate sort of baseline?

Broten

No. After we had success, which was announced at a joint US-Canadian URSI, 1967 in Ottawa -

Sullivan

I didnít realize that. How appropriate.

Broten

Well, itís even more astonishing than that. Dr. Yen and I had been up trying to get this correlation in the tapes at our observatory where we were doing it, and had just finished working about 24 hours when we got the first fringes on a Saturday. We worked then all day on Saturday and Sunday morning, yes. We worked all day Sunday to get these better and defined. We drove down without any sleep to Ottawa and Monday morning presented them at the conference. [Laughter]

Sullivan

I see. Had you already sent in an abstract about this?

Broten

No, no.

Sullivan

This was an unscheduled paper.

Broten

We were to speak to speak at URSI on the idea -

Sullivan

The idea, the technique.

Broten

Yeah. The technique and that. So it was the American group under Marshall Cohen, who was also to speak at it.

Sullivan

Okay, well, now let me ask you a general question. If someone in the late 1950s said at a cocktail party or something has said ďWhat do you call yourself?Ē or ďWhat do you do?Ē, what would have been your answer at that time.

Broten

In the late Ď50s?

Sullivan

Yeah.

Broten

I would have called myself an astronomer.

Sullivan

An astronomer? You wouldnít even have said radio astronomer? I see. So despite the fact that you werenít invited, so to speak, to astronomical meetings, you still called yourself an astronomer.

Broten

Yes, I think that the feeling has always been that radio astronomy is (just another phase?) of astronomy. I donít think the feeling has ever been any different.

Sullivan

Amongst the radio astronomers anyway.

Broten

Amongst the radio astronomers. The reason why URSI was used more than AAS was for two reasons, maybe three reasons. One that they didnít feel at home giving their papers in the optical sessions. But more that in the early days, a great deal of what you were doing was technical. And all the early radio astronomers were also technical people who did some of their own work. Nowadays people graduate in astronomy and expect the equipment to work. But that was not the case. We had to build our own equipment, everything. So URSI was a place where you came and gave your technical results, where you came and presented your astronomical results, and where you met other radio astronomers. In the early Ď50s, there probably werenít more than about 50 radio astronomers around the whole world and you knew them all.

Sullivan

Right. Thank you very much. That finishes talking with Norm Broten on 7 August í78.

End Tape 111B


Modified on Wednesday, 20-Jul-2016 13:57:53 EDT by Ellen Bouton, Archivist (Questions or feedback)