[Costain, 1961]
Carman Costain, 1961 (DRAO photo from Jack Locke collection)



NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Carman H. Costain
At Penticton, B.C., Canada
28 March 1974
Interview time: 50 minutes
Transcribed by Alan H. Bridle

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 Alan H. Bridle in 2015. The transcript was reviewed and edited/corrected by Ellen N. Bouton. Any notes of correction or clarification added in the 2015 reviewing/editing process have been included in brackets; places where we are uncertain about what was said are indicated with parentheses and a question mark, e.g. (?) or (possible text?). Sullivan's notes about each interview are available on Sullivan's interviewee Web page. During processing, full names of institutions and people were added in brackets when they first appear. 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.

Click start to listen to the audio for part 1 of the 1974 interview. (Link for part 2 audio is below.)



Sullivan

[I'm speaking with Carman] Costain at Penticton on 28 March 1974. Where did you begin in Radio Astronomy? What was your association with it in the beginning?

Costain

The start was really a summer student job at the Radio Physics lab at the Defense Research Board.

Sullivan

That was located where?

Costain

This was in Ottawa. I was at the University of Saskatchewan at the time and I had just finished my B.A. Year and wanted to get away for the summer and I had some contacts at the Defense Research Board there. And [Martin] Ryle's phase switch paper had just come out, the phase switching interferometer.

Sullivan

So this was '52 then?

Costain

This was the summer of 1953, the paper was out in '52. I had done electronic work in summers previous and had as a hobby even before university. So I was asked to build a phase switch set essentially to monitor Cassiopeia A for scintillations.

Sullivan

I see. By whom now? Who asked you?

Costain

This was Peter [Peter Allan] Forsyth, who was later head of the Radio Physics Group there at the Defense Research Board and is now director, I think, of upper atmosphere research at the Upper Atmospheric Research Institute at the University of Western Ontario. I had worked with him previously at Saskatchewan, I had run a radar set on the aurora. That was almost a family connection, he was a friend of my brother's and so on. At any rate, I had built electronics for him before and he asked me to build this in the summer was just long enough to set up a simple ten-lambda interferometer, very simple dipole antennas, but for Cassiopeia that's adequate. And the phase switching receiver actually was used for about five years, I think, Ted Hartz of the same group actually analyzed the data. I left at the end of that summer. But it did look like a promising project. One of the main efforts at Saskatchewan was the upper atmosphere research and it was even closer of course to the magnetic North pole so upper atmosphere research on aurora was one of the projects.

Sullivan

What was the purpose of this? To use Cass as a background source?

Costain

Cass was a transmitter coming through the atmosphere and you just measured the scintillation caused by irregularities in the ionosphere. Particularly it was of perhaps of more interest there because of storm activity. When you had the aurora, when you the disturbances, what was the dominant effect? So I built another unit then at Saskatchewan for my M.A. Project, in fact. I had an early start on it at the end of my Honors year and I had about nine months of observations to work on. I suppose the main thing about it was that the dominating factor there was not so much the night time effects, scintillations in the early papers by Hewish had always peaked about 1 a.m. or something so they were definitely a night time effect but overwhelmingly the dominant effect as viewed from Saskatoon was the effect of the auroral zone and the fact that you were looking through more disturbed ionosphere so the scintillations were very, very severe at lower culmination of Cassiopeia.

Sullivan

I see.

Costain

By the time I had finished this sort of work and reading the background on it, it seemed to me the most exciting thing was ...

Sullivan

Cass itself

Costain

...the astronomy. And at that time, this was '54 or '55, the only places to go for a research student really would be Cambridge or Jodrell or Sydney, Australia. I thought a little bit about perhaps Cornell which again would have been upper atmosphere but those were the choices and since my brother had been to Cambridge and they had a strong group there, I did apply, and happily was able to go.

Sullivan

And when did you go to Cambridge? This was '55?

Costain

This was '55. Well, the one advantage I found I had in going to Cambridge most of the students there hadn't had any practical experience before entering graduate school. I recall Jan Hogbom particularly who was a very brilliant chap but he'd never seen a vacuum tube up close (laughs) and spent a couple of years just trying to find out what they were all about. And this had the advantage that just a month or two after I arrived I was building small antennas to observe a Crab Nebula occultation. It happened to be that there were two that particular year, one was in the Fall of '55 and one early in 1960. The first one didn't work out properly because we hadn't the interferometers really weren't set up properly to get rid of the low order components from the Galaxy, and it turned out this was the thing dominating our records [next few words unlear]. In the second one we got a very wide spacing and we had the source going through it sort of tangentially through the interference lobes as we set up a more or less North-South interferometer, and we phased the maxima onto the source during immersion and emersion. We confined that to 80 MHz, but it worked very well and defined the structure of the Crab Nebula then to the usual three minutes of arc source.

Sullivan

This would have been '56?

Costain

Yes, early '56, sorry I said 1960, but this was early '56.

Sullivan

This has been done before successfully ...

Costain

There was one occultation done before on IC443 but the problem there was of course they had no idea of the distribution of radio brightness in the source. They did have one short drop in intensity if you like and you could assume that belonged to the eastern arc which in fact I guess was true, as later on the resolution showed it but in those days you didn't know. It was [Francis] Graham Smith, I think, and someone else, had done it. So with Bruce Elsmore we did this occultation and in comparison of the delay times of immersion and emersion it also gave an upper limit on the Moon's atmosphere, or I should say the ionized part of it. I think the number was ten to the minus thirteenth or something like that.

Sullivan

So that was the first successful one on the Crab, then?

Costain

I think so, yes. And after that I did a brief experiment using John Blythe's 38 Mc/s antenna looking for structure of very large angular size. He had done a synthesis survey, he had about a two degree beam I guess with that system, but we were looking for things that perhaps you could measure by using sections of the antenna. It was quite a simple experiment and in fact it didn't work out. The sky was just too confusing or is not made up, if you like, of lumps of large angular diameter about a few degrees. And then really at the end of that year the grant that made possible the Lord's Bridge radio astronomy site was obtained - I guess the Nuffield Foundation, I'm not sure of the exact term - and then of course the plans were to build the new antennas and I was offered the opportunity to build the 38 Mc/s system providing I could stay for three more years. That was obviously going to be a long job because you were going into a site where I think you were still running in electric power, you didn't have anything on the site, you were starting absolutely from scratch. This was with Graham Smith as my supervisor. Most of my work then was involved in the design of that and building it really from scratch, everything, even IF strips which were just converted from surplus war equipment. All of the electronics, in those days the students really had to build everything. Bruce McAdam, who was a colleague, actually I think built the integrator for it. But all of the other parts of it, the phasing switches and all the electronics and receivers, preamps and so on we had to build as well as much of the physical structure, hammering in stakes and concrete.

Sullivan

That I have heard a lot about from many people. You didn't buy things off the shelf because of lack of money, or they just weren't available?

Costain

I think it was money, I think it was definitely money. There is a disadvantage to this in that of course it eats up student years. On the other hand, it's marvelous training for independent research which I feel the Cambridge system is very, very good in that regard. You weren't really pushed too much by your supervisor, you were turned loose by your supervisor who would check up on you at certain intervals, and you'd be asked questions and you'd have to defend your decisions, but providing you could do this there usually would be a meeting every once in a while. Ryle always knew what was going on with all the experiments really at that time. It was a comparatively small group with Hogbom and McAdam and myself and David Edge joined the group as research students that year and that doubled the number, there were four others.

Sullivan

You all came in in '50

Costain

We all came in the Fall of '55.

Sullivan

So these three years that you built the 38 MHz array, which three years were they?

Costain

That would have been '56, well starting very late in '56 and planning on '57, '58. We had it operating in '58, and I would say I think the East-West arm was largely constructed, I could date it from Sputnik One which caused a great excitement at the time.

Sullivan

John Baldwin has described that to me.

Costain

Oh, that was a very exciting time. We had sent one person out to get a receiver going, we had Saturday morning meetings every week where we discussed literature and everything else that needed doing, and [George] Whitfield was sent off Saturday afternoon to set up a system and detected it Saturday evening, and on Sunday of course everyone went out to see what had happened. Then a proper survey antenna went in and by the end of the week there were about five different experiments running, people working all around the clock and sleeping [there] of course. That took about a month out of it but at that time we had most of the East-West arm built which of course was the heart of that particular antenna, the long East-West corner reflector and 128 wavelengths. And the moving antennas were built shortly after. Part of the time then was just really sorting out the problems with the electronics and the observing. I did do one series of observations, of which I guess the most interesting result was the first really good high resolution map of the North Galactic Spur. But there was just barely time then because we were still handling - having the software problems as well as converting to a new computer and so on, and so I didn't really personally derive a great deal of profit from that but I had the fun at least of building the antenna.

Sullivan

So what was your thesis actually, then? The Spur

Costain

Primarily on the design of the synthesis system, what to do about low order components, the defects in a system like the Mills Cross where the central bit was removed and part of that of course that led into the kind of antenna I built when I came to Penticton where we largely, by building it a different way, actually using the overlap region as a part of each array, we could restore that DC component with the proper weight. So it was partly antenna design and a little bit of work on the Spur, where the edge was which with that one degree beam was unresolved, it was a very sharp, Northern border and so on. As I say, really another year would have been some interesting astronomy but [Sidney] Kenderdine and Baldwin and so on finished off the main observing work with that antenna. The other thing of course was we had the problem of calibrating the system so I did a scaled aerial experiment between 38 and 178 [MHz] to check up on background spectra. The original idea was to measure the low order components but we had a 178 antenna the same size so we measured the background spectrum with a fairly broad beam. That number did stand up, it was a little lower than the accepted 0.5 at the time, or 0.55, particularly the higher frequency values which led to steeper indices for the background but in this frequency range it was definitely down around 0.4 and that's the accepted value now. So there was that sort of offshoot to calibrate the system.

Sullivan

I assume that you're ready to move away from Cambridge now.

Costain

Oh yes, if you'd like.

Sullivan

But before you do what was it like in that atmosphere? You say that Ryle knew pretty much everything that was going on in the group as it was small enough at that point. Was he the one who really should have the credit for the whole philosophy of the place and so forth?

Costain

Well I would say 'yes'. I regard Ryle with great admiration. He's a fabulous character, a brilliant man, no question about it. Tremendous energy, a certain nervous energy if you like, he drove himself pretty hard. It was interesting in that you'd think with his stature that you couldn't approach him but in fact he was 'Martin' to everyone, to the lowliest research students. The thing that struck me more than anything else about Cambridge were the Saturday morning discussions, where particularly discussing literature perhaps, various papers that had just come out. It was very very good training for research students because people were sitting around being very rude (laughs) about these things and it was interesting that in the arguments that followed, and they were very vehement arguments, people would yell at one another, and you could call Ryle a clot. It was very difficult to prove, you know, because he thought very quickly on his feet, but the point is you could try. There wasn't any of the austere professor that you couldn't approach. I thought he was rather remarkable in that he could let down to the extent that he would let even first year research students argue with him vehemently about what they believed or what they didn't believe and at the same time he had sort of complete control of the group. There was no problem about that.

Sullivan

He probably gained more respect than he would have otherwise

Costain

Oh, no question. And of course he did attract very, very clever people around him. Inevitably the Cambridge system ... well the name attracts. Historically they have been able to skim the top one or two per cent in Great Britain. I think it perhaps it was easier for people from outside getting in than it was for someone born in Britain but they did have brilliant students and of course [Antony] Hewish and Smith and so on and the people, Baldwin and [John] Shakeshaft, who came around later and then became permanent staff members were of course all very very good.

Sullivan

And is their philosophy pretty much the same as Ryle's?

Costain

Oh, not necessarily. Ryle has very strong views on some subjects. One of the things and there have been some complaints about it in the astronomical community if you like, is some of the results coming out of Cambridge that some people would like to have seen a few months earlier. There are two reasons for this really and I have argued this question with him on many occasions. One of them is that in Cambridge you sink or swim on your thesis. It must be unique research - unique, independent research. If someone comes along at another institution and does precisely the experiment you've done and has published it, then you start all over again.

Sullivan

Even though you did it independently?

Costain

That's right. It has not only to be independent, it has to be unique.

Sullivan

That university policy?

Costain

That's university policy. And this has happened. Theses have been scrapped because the results have come out. So this is one of the reasons why it is not done, you can get around this partly by insisting that of the student has an exciting result that he write it up, and if he has of course published it in his name then the fact that it is Chapter Four of his thesis is all right but this is part of the reason for the time constant. And he doesn't talk much about hardware - again because he feels this is sort of an edge that he gives his students, if you like. It's something that he feels that he needs to provide for his students or he needs in order to get outstanding students. It's something he feels very strongly. I don't agree with this philosophy myself, but this is his own belief. So in this policy it is basically to protect his students, that's the thing behind it, part of the thing where the things come out a little later than they do perhaps in most places. This isn't true of everything, but it's true of some things.

Sullivan

Your second point was not divulging great details about hardware.

Costain

It was again an edge, if you like, for his students.

Sullivan

Do you know of any cases where radio astronomy students got hit by this first rule that you mentioned, this first point?

Costain

No. I did hear of a couple while I was there but it wasn't specifically in radio astronomy, it was in another

End of Tape 31A

Begin tape 31B



Sullivan

This is continuing with Carman Costain on 28 March 1974. You were there precisely when the great controversy with Mills over the 2C survey and so forth and you came in as sort of an outsider so maybe you could look at it more objectively. Or did you quickly take on the Cambridge point of view?

Costain

No, I think that actually all worked out in the end. There was one part of this that was never very much accepted by people outside Cambridge and that was Peter Scheuer's analysis, the so-called P(D) distribution. Now this is, I still think, a valid treatment of the data. You have confused data, but at the same time if you put different populations, different models of the Universe into this, you simply get different answers and there's no question about it. And all of the Cambridge instruments that were built had very good signal to noise at the confusion level so that there's no doubt of course that the confusion was, as far as it affected the individual source fluxes in the 2C survey, was very much under estimated but of course if you like, this should have been something that somebody had studied and Scheuer's work could almost be used to show it, that you can take the probability of getting a certain intensity at a certain position and if you do that with the 2C survey then you come out with exactly the numbers that you expect and the errors that you expect.

Sullivan

In fact it was used for just the opposite, wasn't it?

Costain

No, it was an extension of it. It was used - the source counts, when you show the fluxes are not valid, all right, the intensities or the counts for the weaker sources were certainly not valid, there's no question about that and they had to back off on those. The conclusions about the law of the galaxy count, or the log(N)-log(S) slope, were in fact consistent with the P(D). You might call this a fluke, or whatever. It sounds like a lame defense but it is still valid. When the surveys became deeper and resolution was no longer a factor that slope still held. In fact, the main difference in that thing with Mills, firstly the Cambridge weaker sources were not valid, that is certainly true, but also there was a large number of sources of high flux density that were declared sort of extended sources on the Mills Cross. Now these when they were later checked out turned out to be in most instances blends of other sources, that is there was not a very high population of extended sources. This was the main error in the Mills thing. Now this of course adds a number of brighter sources that you put in which also affects the slope. Now when you take these two things out, the differences between the surveys as far as galaxy counts largely disappears.

Sullivan

So you're saying the confusion thing is well known but this thing about Mills's survey is not so well known, I don't think.

Costain

This was the thing with the 4C - well even in 3C but particularly in 3C Revised where they were using the 4C antenna and going to higher and higher resolution now, and you begin to check up on these things and also a lot of the heat had gone out of the argument so that Mills was visiting the Cambridge observatories and looking at the scans of the particular sources about which they were arguing, if you like. The higher resolution measurements that were done at Cambridge and did in fact as I say eliminate a large number of these sources which would have gone into the counts as bright intense sources which affect the slope at that particular end. There are not many sources there, you see. In all of these log(N)-log)S) arguments one of the things that is perhaps overlooked is how weak the statistics are at that particular end. So in the end I think that all worked out. The thing that people felt, and I think were wrong in the sense that they were saying Cambridge were clinging to this in spite of the fact that sources were wrong, was that they did very much overlook Scheuer's analysis, and Hewish later on analysis, the P(D) which I still think is valid.

Sullivan

You mean that this gave Cambridge the justification to think that the data was still good.

Costain

It wasn't a question of the individual source fluxes being correct, it was that the population had to have that steep slope.

Sullivan

The right distribution...

Costain

The right distribution was there, and this is still true at this frequency, apparently there are differences at higher frequencies but I think these have been adequately discussed.

Sullivan

I hadn't heard this. So after the heat died down, then actually Mills and the Cambridge people did get together, and

Costain

Oh yes, I think so.

Sullivan

I've only heard about the great animosity.

Costain

Well, there was in the early years, but it was just not enough personal contact. I think when that started to happen. I can recall a particular visit of Mills to Cambridge, I've just forgotten the year now, I guess it was after I left the observatory and I was back for, perhaps I'm not sure now whether it was the Hamburg I.A.U. or an URSI Meeting or something ....

Sullivan

Some time in the early 60's...

Costain

But this had largely been sorted out by that time. I do feel the missing thing, the main factor there that caused much of the trouble was in spite of the counts which were obviously wrong because the weak sources in 2C were in error and blends in many, many instances, the P(D) analysis still held up that steep slope, and of course that's why it was never abandoned. But this was substantiated again when they could actually resolve these sources and get the fluxes properly this was the slope they got again. So I think it's really stood the test of time. You can argue about its interpretation, but not about its reality.

Sullivan

OK, back to you now. You left Cambridge in what year?

Costain

In the Fall of 1959, with the thesis not quite tidied up because [we] just got the things out of the computer at that time, well more or less two thirds finished if you like, and I came to Penticton where we just were putting up the 25 meter dish.

Sullivan

That was the first thing here...

Costain

Yes, we were just building really, in the Fall of '59 it was going up. But by the middle of '60 we had a hydrogen line receiver we had purchased a Ewen-Knight receiver so that we could get started and get the station off the ground.

Sullivan

Can you just briefly tell me about Canadian radio astronomy prior to Penticton and who should I talk to about that?

Costain

The main effort had been solar work. That would be [Arthur E.] Covington, primarily, in the early years. He started monitoring the Sun shortly after the war, I guess in '46 probably, at 10 cm and I guess he has the longest continuous measurements of solar flux at that frequency and has maintained them to the present day, very carefully calibrated and so on. The main effort at that time was certainly in the solar work. When it was decided that Canada should have a another, let's say a larger, instrument to do some radio astronomy, the National Research Council and the Dominion Observatory at that time were competing for the grant to have the new observatory and it was given to the Dominion Observatory, the idea being that it would be primarily aimed at hydrogen line work which would follow, if you like, in the galactic tradition of [Robert Methven] Petrie's work at Victoria and so on, and [Carlyle Smith] Beals's own interest - he was the Dominion Astronomer at the time - in interstellar lines and so on. They thought the radio astronomy and particularly the hydrogen line would be a natural thing for the Dominion Observatory to follow up. So that went into Energy, Mines and Resources department at that time and hence the observatory was built. This site was chosen as the best one they could locate in Canada from the point of view of - well - weather conditions and accessibility and so on, but the main criterion being radio interference, and it's proved indeed to be a very good site from that point of view. And it had enough flat land for my own interest at that time (laughs) to build some large arrays.

Sullivan

So really Covington is the person I should talk to about pre '59 Canadian radio astronomy.

Costain

Yes, I would think so. Then later on of course they were given a grant to build the 150 foot in Algonquin Park which came in later. And in this case [Norman] Broten and [Wilf] Medd and people like that, and later on Jack Locke of course joined that group as well. Locke was given the job as head of the stellar physics group at that time in the Dominion Observatory's group in Ottawa to set up the observatory here in Penticton.

Sullivan

So what were some of the first things done with the new dish?

Costain

One of the things that looked exciting and looked interesting at the time was a paper by Nannielou Dieter on association of neutral hydrogen with OB associations. [Note added 2015: N.D. Conklin, ApJ 132: 49-57, (1960)] Unfortunately at that time we were a little naive about the reality of some of these OB associations, which when we asked Petrie to investigate them in detail, he found they weren't associated in radial velocity, distance or any parameter (laughs) that you could assign, it just turned out to be chance coincidence in many cases. But anyway [Dieter] had apparently had a correlation and that looked like interesting work so we picked a few areas of sky, and since we had just a single channel we decided to map at constant radial velocity over the region - a fairly large area of sky, something like ten, twenty, thirty degrees. Covering this region to see what was here but primarily thinking of OB associations at that time. With a single channel receiver an enormous number of observing hours over two or three years. We took turns ...

Sullivan

Two or three years you spent on this?

Costain

Locke and Galt and myself, for a couple of years anyway. Our observing day was often twelve to eighteen hours.

Sullivan

All the time with a single channel?

Costain

Yes. At that time we decided to abandon (laughs) hydrogen line work for continuum until we had a multi-channel facility. It just takes time to develop your hardware, you come to a new place and a lot of things have to built up to support the system, and the greatest problem, of course, we've always had is that we were grossly understaffed. We started off where in the beginning we had not even one technician. We built our own equipment, that is Galt and [Ed] Argyle, Locke and myself, and [Roy] Hamilton joined a little later.

Sullivan

So what came out of the couple of years spent on the OB associations?

Costain

Not a great deal, it wasn't terribly profitable. I think mapping at constant velocity was a reasonable observing technique certainly for a small number of channels, and indeed you might, if one were doing similar work, you might adopt the same thing to just simplify [the reduction]. One of the interesting things that did come out was that we did find an isolated cloud around IC443. It was an anticenter region survey, quite large extent, and this was a detached feature that looked very much like it is a cloud involved with the remnant and it is certainly one thing that we will follow up at high resolution with our new synthesis machine.

Sullivan

So this was the only thing done these first couple of years, was this project?

Costain

Yes. Well of course at the same time we were proceeding with the design of the 22 MHz array which was really my main interest.

Sullivan

But that was the only thing done on the single dish? And where was that published?

Costain

That would have been in Ap.J. There was the general survey of the wide area [Note added in 2015: J.L.Locke, J.A.Galt & C.H.Costain, ApJ 139, 1066-1070 (1964)] then a special one that we did with the follow-up on IC443 [Note added in 2015: J.L.Locke, J.A.Galt & C.H.Costain, ApJ 139, 1071-1073 (1964)], but there were many many months of observing in this because it was so terribly slow. A single drift scan of several hours would give you one declination at one frequency and this just shows how things have changed instrumentally, you wouldn't even consider doing this sort of thing now. Then you would reset say fifteen minutes away and you would do another two hour scan. And we had an analog device that would correct the local oscillator, so we would track, and you would have to make fine adjustments on this perhaps every thirty minutes or so but we would keep with an error of let's say a kiloHertz or something like that. But we're talking about 1960 and things are different now and of course now you'd set your computer and have it run the whole thing and you wouldn't even consider doing single channel work. Well of course one of the immediate decisions was to build a multi-channel facility and Argyle did a preliminary thing where I think he built perhaps the first analog delay line thing, for an autocorrelation receiver. This was using, instead of the shift registers commonly used, now he used actual delay line with taps and did a survey of M31 that was certainly, for some time, the best overall survey of that galaxy.

Sullivan

Now when was this built relative to [Sander] Weinreb's autocorrelator, which was '63?

Costain

I have forgotten the dates now, I would have to check that out. I think it was probably done about '62 or '63. At any rate we decided at that time that the analog technique was too difficult for narrow band work. Incidentally, I might add that this was a suggestion by Ryle that we try this technique. He visited us in 1960 and suggested that we try it out and that it might be a good way of making a spectrometer. I guess it would probably be before Weinreb and before the digital shift register would be considered, I've almost forgotten the details. At any rate you couldn't build a very long delay line and he had to build his own anyway, you couldn't buy one that had the frequency characteristics you needed. For the long delays you were of course getting attenuation and so on so actually analyzing the spectrum was difficult. But anyway it did provide sufficient velocity resolution for the 36 minute beam and M31 and did quite a good survey. There were also occultation experiments done with the dish in the continuum but the main effort was obviously to build a multi-channel facility. At that time we then were becoming heavily involved in the 22 MHz array. We wanted to build basically a one degree [resolution] instrument to operate at this frequency. This was almost a factor of two below the 38 MHz array at Cambridge, the idea being to extend background and radio galaxy spectrum measurements. So this was certainly my own major effort at that time with [David] Lacey first and then [Rob] Roger, the three of us worked on this project. And when we had the first part of that built and operating, that is let's say sixteen dipoles, started observing -

Sullivan

And when was this?

Costain

Oh gosh this would be '64 or '65 or something of that order. We found that observing conditions this was at sunspot minimum were just exceptional, that is we were often interference-free 24 hours a day and little scintillation and it became clear then that the array was going to be very successful, that you could really do radio astronomy at 22 MHz. At least in Penticton here we had good protection from local interference and our main concern was Japanese fishing boats. We had picked a marine mobile allocation and this was our source of interference. Because this was so successful, Cambridge at that time were very interested in doing a 10 MHz experiment. Graham Smith primarily and Peter Scheuer. When they visited here - well, we heard about their interest - and they went out to the polar cap area at Resolute because the Alouette satellite had found that the ionosphere was thinnest there. Unfortunately every electron that was there was moving at high velocity (laughs), it was terribly turbulent and even with a ten lambda interferometer they couldn't see Chris Purton did this they couldn't see Cassiopeia, so they abandoned that idea. The idea was of course to build where there was a thin ionosphere but that didn't work out.

Sullivan

I never heard about that. Was that ever published?

Costain

No, I don't think so. As radio astronomy, it was hopeless. It was radio astronomy under very difficult conditions as you can imagine.

Sullivan

But how much did they actually built up in Resolute?

Costain

Oh it was just one phase switch set, the sort of thing you need - where you'd expect to get a nice sine wave out of it, or a scintillating sine wave -

Sullivan

And how long did they spend up there?

Costain

Oh I think just a few months or a few weeks perhaps, I'm not certain. [AHB comment added 2015: Peter Scheuer made a brief visit to Resolute in the summer of 1963 to begin the installation there but Chris Purton spent much of the following winter documenting the conditions and also wrote the abortive polar cap experiment up as a chapter of his Cambridge Ph.D. thesis.] It doesn't take very long for someone who knows his way around to put up a simple interferometer and equipment but then we discovered their interest and it turned out that we could finance a 10 MHz array. We were short of people so we agreed to do it as a joint venture. So after the 22 MHz array was finished, or sort of well on its way, we started building the 10 MHz array as well.

Sullivan

This was before you had any results out of the 22 MHz array?

Costain

This was before we had any results out of the 22, this was a separate project. John Galt, Peter Scheuer and Chris Purton primarily, and this was certainly the largest low-frequency array at that time and another order of magnitude down in frequency by another factor of two. It was used by Purton firstly and then by [Alan] Bridle and later on by [Jim] Caswell who was here as a post-doctorate fellow. With the 22 MHz array we first concentrated on observing source spectra. When the array was conceived [slight break in recording] the obvious need was for radio source flux densities at 22 MHz. When the array was planned we only had values for four sources Cassiopeia and Cygnus and Taurus and Virgo, and that was it. We expected to and will eventually end up with about 500. The first intensive observing was actually with operators here pointing and scanning the known sources, pretty well around the clock, and then we would spend a day just on the general scanning. So we were combining mapping the whole sky and observing particular sources. It was necessary to observe many many times, the problem is the ionosphere of course, with interference and scintillations and absorption. We did monitor absorption along with the other things so that we could at least keep track of ionospheric problems.

Sullivan

I guess to differentiate the crap from the real stuff you had to repeat -

Costain

We had to repeat, most of the sky has been done about ten times in fact. That's why the time scale on this is rather horrible and... we ended up with about 200,000 IBM cards, each would have say ten values.

Sullivan

How many of those ten values are useful?

Costain

Oh, this is the useful data (laughs) We had discarded after editing we had about 200,000 [cards] and most of the sky has been done from minus 25 declination to a little over 80 degrees. We didn't bother with the pole because we proposed to do that with a polar cap synthesis. So we have a full sky background map from that. We have done a little bit of reduction on that but the sources we combined with the 10 MHz results to get the spectra and the scales for the sources. I think perhaps the most interesting new result in that was a few sources with very steep spectra that correlated with Abell clusters. By steep I mean sort of 1.5, 1.8, 2.0 very very steep low-frequency spectra - and some of these are obviously extended components. In the case of the Coma Cluster it's roughly the size of the cluster itself, about fifty minutes of arc.

Sullivan

Are these connected with the X-ray sources?

Costain

Yes, and some of them are correlated with the X-rays as well. And there's been some recent work by Bridle and [Paul] Feldman on the theoretical interpretation of this, whether you've got a hot gas or whether you have inverse Compton. With the very broad sources in the clusters and the steep low frequency spectra this is consistent with the inverse Compton interpretation, but we'll probably be doing some more on that with the remaining sources.

Sullivan

So you started in '65 or so with the 22 MHz

Costain

Something of that order, yes.

Sullivan

And you still really haven't got all the data out.

Costain

That's true. We have published about 60 per cent of the source fluxes, very little of the background. Roger did one what we call pilot interpretation of the W3, W4, W5 region, just to see what it was possible to do with data of this kind where we had a high frequency survey that pretty well delineated the ionized hydrogen as far as structure is concerned, and you then can work out what you should see at 22 MHz and compare that with what you do see and then you can sort out the ionized part from the ordinary nonthermal background radiation. And as a matter of fact we have a good map at 178 MHz from Caswell and with the high frequency maps, 38 MHz from Cambridge and the 22, and with this kind of data you can actually solve as a function of frequency as well, and measure temperature, and these were again consistent with the ones determined from the excited hydrogen lines, that is temperatures of the order of 4000 degrees for one region and I think about 6000 degrees for another. So I think there's a good deal of profit in that kind of work but most of this indeed has yet to be done.

Sullivan

So it's been really a sort of ten year program.

Costain

It's an enormous job to take on the whole sky with two people, when particularly you are building at the same time these synthesis systems for hydrogen line work. This is partly time scales, things take longer to build than you expect and the computer at that time was in Ottawa of course, we were doing all of our data reduction by remote control as it were and this is a difficult way to operate. If we could have hired a couple of clerks we could have put out the survey two years ago. It's unfortunate. I very much regret the delay and I've had a lot of rude remarks about it but it's certainly exciting data and we will have it out.

Sullivan

What about the results from the 10 MHz instrument?

Costain

The most complete source survey was done by Bridle and of course [he] combined his results with Purton. And Caswell did several years' observations where he could really only look at the winter sky because of the change of the sunspot cycle, and he has a good map of the background as well as - if you like - confirming the point sources, but Caswell's main interest was in the background radiation and the absorption effects that we just discussed by normal HII regions. In the absorption of course you can detect very, very low emission measures at 10 MHz, things that probably aren't even visible photographically will cause measurable absorption. The sky background is so very, very bright. Along the main part of the plane the temperatures are two or three hundred thousand degrees at 22 MHz and even brighter of course at 10 so that everything there is optically thin. We see quite a broad absorbing trough as well as the known regions.

Sullivan

Well I think that brings us up about to the point I was talking about, you began thinking about the synthesis interferometer you said about '68 or '69.

Costain

About that time, yes. We were looking for something to go on when with this array - after you've surveyed the whole sky that's all there is to do with the low frequency array and the plan was then to look for something interesting and synthesis work at hydrogen line looked like the most profitable thing. It would have been perhaps more profitable or more exciting if the time scale had been a little shorter, it just takes rather a long time to get through the engineering design studies and so on and get to build all the electronics with a small group.

Sullivan

What about the VLBI work? Were you involved in that?

Costain

No, only on a sort of consulting basis. When it was first approached - it was interesting - Herb Gush who was at University of Toronto came out and we happened to - I had been at university with him at Saskatchewan and John Galt had known him in Toronto, and so he did stop by, and he was discussing then very early, about three years before anything happened, or four, about doing an experiment with tape recorder interferometry because atomic clocks were just about good enough. Unfortunately at that time, tape recorders weren't. We were thinking of digital tape recorders and speed of the digital tape recorders then and also the computer which was say an IBM 1620 and for ten seconds or a hundred seconds of observing time there were hours and hours of computing time involved. So after discussing the thing in the group here at that time we decided it wasn't practical. And it was later, perhaps two or three years after that

Sullivan

When was it that you discussed that?

Costain

Oh I would have to look that up. I have it written down perhaps somewhere in some discussion about the Canadian LBI project. It would have been at least two or three years before there was any, let's say, announced intention to go ahead with the project.

Sullivan

That date must have been '65 or something like that.

Costain

Something of that order, yes.

Sullivan

So '62 or '63 -

Costain

It was back then, yes, quite a long time ago. And I don't really remember who was responsible, it might have been [Robin, aka Bob] Chisholm at Queen's, someone realized how good the timing was in the standard television video tape recorders, that the time stability really has to be quite remarkable for them to work. It was simply a matter of putting the numbers in and we realized that with an analog system we could do long baseline interferometry. And the result then was we looked at the problem and it was clearly just an engineering problem that could be solved. There was no question about it, it would work. So it was a co-operative effort - a very good co-operative effort - between our group here, almost entirely John Galt because Rob Roger and I were fully committed to the big low frequency project and clearly couldn't be involved - but some technical people were involved a little bit here - but primarily John Galt and the people at Queen's, Alan Yen at Toronto, and Broten and Locke at NRC in Ottawa. Bob Chisholm at Queen's was a very important part of that, particularly from the technical point of view. And indeed, of course, they were successful in making it work. It was interesting that the early one, two or three years earlier, it had been kicked around and discarded simply because the hardware wasn't good enough at that time. Of course now the American system is a digital system but the tape recorders are very very much better than they were. And the computers. Even now the computing time is non-trivial.

Sullivan

I think that was the key to it, once the high speed computers became more generally available.

Costain

But these are the kind of considerations that affect what you do. It was certainly a very exciting project and they actually made it work.

Sullivan

Well, thank you very much. That ends the interview with Carman Costain on 28 March 1974 at Penticton.


Modified on Tuesday, 17-Nov-2015 09:15:43 EST by Ellen Bouton, Archivist (Questions or feedback)