Interview with Gart Westerhout
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The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. 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.
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Sullivan
Alright, this is talking with Gart Westerhout on 22 November ’73 at Max Planck Institute in Bonn. So how did you get involved in radio astronomy?
Westerhout
In essence by ... you know, when you're a young graduate student you don't really quite know where to go yet. So what I started out doing was working with [Theo] Walraven on amplifiers for photoelectric photometry. I don't quite remember anymore why I sort of expressed an interest in radio or electronics. I fiddled with radio when I was young, and somehow or another that made them assign me to Walraven.
Sullivan
You had studied as an undergraduate in astronomy?
Westerhout
Yes, that's right.
Sullivan
So you're one of the very few early radio astronomers that studied astronomy.
Westerhout
That's right, that's quite correct. [Hugo] Van Woerden is another one.
Sullivan
But he's not quite so early, is he?
Westerhout
Yes, he a year earlier than I. He got his PhD much later but he started in '44. He got out of high school the year before I did.
Sullivan
I see. I didn't realize that.
Westerhout
And there, of course, was a year lost for me during the War. I got out of high school in '44 and of course I lost a full year. Van Woerden got out of high school in '43 and in essence lost two years but did already some astronomy.
Sullivan
I still have to talk to him. That’s why I don’t know exactly when he started. So you worked with Walraven?
Westerhout
Yes. And then, I forget exactly when it was, but that must have been in May of 1950 [Sullivan: July 1950], [John G.] Bolton and [Kevin C.] Westfold were making this trip around the world and they were spending a long time in England and [Jan Hendrik] Oort invited them over to come and give a talk. Apparently they did everything together, they had published this paper shortly before on the distribution of radio emission over the sky, where everything was so beautifully smooth. They had even de-convoluted for the antenna pattern, so-called, which was was 17°. So we really believed that that was the distribution of radio emission at that particular frequency- whatever it was I've even forgotten that.
Sullivan
It was 150 or 200, I think. [Sullivan: 100 MHz, actually]
Westerhout
Something like that, yes. And they came and gave a talk. It was actually rather interesting because there were stages where both of them were standing in front of the blackboard at the same time. I can still see that. Jumping up and down and correcting each other, making remarks here and there. I still remember that colloquium vividly; it was a very interesting one. And I don't quite know how it then came about, but I guess in Oort's inimitable way he simply picked somebody and said, "Would you like to look into this particular problem?" And that's how I started to look into that particular problem. I'm trying to think now whether that was- no, that all went sort of at the same time because I was also looking around that same era at [Walter] Baade's determination of the distance to the galactic center, where he looked at all the RR Lyrae variables. You saw that if you plotted the RR Lyrae variables as function of magnitude, it was a beautiful peak. And making appropriate corrections, you could say something about the mass distribution that governed that spherical distribution of RR Lyrae variables. So all that came in and I don't quite know which came first, the idea of making a model of the mass distribution that fitted the radio data, or the other way around.
Sullivan
But that was influencing anyway?
Westerhout
Those things were all influencing each other.
Sullivan
In the way the final paper came out? What I'm particularly interested in is where did the idea come from to base it on the distribution of stars and the mass distribution of stars? That was the fundamental thing in that paper, was it not?
Westerhout
Yes. That was the fundamental thing in that paper. And that idea came mainly from the fact that when you look- there is a chapter in that paper on the distribution of ionized gas and it was quite clear that the distribution of ionized gas was very much thinner than the observed distribution on the sky. So it couldn't be the ionized gas. Moreover you could show, or we could show, that the intensity from the ionized gas, given certain assumptions and so on, was too low. So although we treated that very carefully, we showed in that paper that it could not be the ionized gas, so what it is you do the next time? You say Ok, the other constituent we know is the stars, if whatever emits that radiation has something to do with stars. And the synchrotron theory was not really known yet. I think that the [Hannes] Alfvén and [N.] Herlofson paper came out in '49 or '50.
Sullivan
April '50.
Westerhout
So when we started that work we certainly didn't know anything about that at all. So Ok, let's look at something that's distributed the same way as the general matter in the Galaxy and see what that gives and adjust it a little bit here and there, and lo and behold it sort of seemed to fit reasonably well. I think the most interesting thing I always find in that paper is the naiveté with which one thought that when you apply a Bracewell-type de-convolution that you then see the true picture.
Sullivan
That you had all the information?
Westerhout
You had all the information and that was the distribution. It wasn't until considerably later- "considerably" means a few years- that we began to realize that, of course, meant absolutely nothing. Side lobes had been removed...
Sullivan
You mean the great smoothness was really leading you astray, and you felt it was actually that way, even with infinite resolution?
Westerhout
Yes.
Sullivan
But this paper, would you not agree, really kept the idea of radio stars alive quite a long while? I mean people had talked about discrete sources as radio stars, but then when you talked about the radio distribution relative to the stellar distribution, then you really began to think of radio stars. Would you say that's fair?
Westerhout
No, I don't think so. Maybe in other people’s minds. But I think neither in Oort's mind nor in my mind did we ever think of discrete objects. Well, maybe we did, yes, because there is an analysis in that paper where you stick in the arbitrary luminosity function and you do all sorts of things that way. Yeah, maybe you're right in that analysis, that one really did think about radio stars. I think we were very careful not to call them stars. We were never thinking of stars.
Sullivan
You never say radio stars.
Westerhout
No, we called- at most we may have talked about objects or emitters or something like that. [Sullivan: "star-like source" in the abstract]
Sullivan
I think that's right.
Westerhout
Radio emitters but we very specifically did not think of stars. That's why I was sort of hesitating there.
Sullivan
So you published this paper in your first couple of years of graduate school then?
Westerhout
Yes, after one year in essence.
Sullivan
That's quite an accomplishment.
Westerhout
And then while I was at it- well, this was, of course, as you may note when you look at the paper, I mean I did the spade-work but Oort did the theory. Oort did a lot of the polishing of the writing and all of that. I mean it was Oort's work and I was the young graduate student assisting in it. But it was a lot of looking up things and finding out everything there was to be found out in the literature up to that time, that's all, including the ideas about the ionized hydrogen, what that would emit. At that same time, [Hendrik C.] van de Hulst wasn't there when we wrote that paper. He was in Harvard that year. The other thing that I suddenly remember, I got when I entered the Observatory as a graduate student, I was stuck in a room together with the Chinese [Sullivan: Indonesian] who had been constructing the 21 cm line receiver.
Sullivan
Mr. Hoo?
Westerhout
Right. Whose building had just been burned down. In other words, I wasn't there [Sullivan: Kootwijk] yet when that building burned down [Sullivan: 3/50]. I didn't participate in that fiasco. But he was sort of sitting there for a while, then he more or less disappeared and as a young graduate student, I never quite knew what happened or what didn't happen.
Sullivan
[Christiaan Alexander "Lex" ] Muller didn't really tell me how that happened, or maybe he didn't know, but what is supposedly how that happened?
Westerhout
It was just an accident. How does anything like that happen? I mean it was a wooden shed in which they were constructing that material, sitting beside the Würzburg.
Sullivan
But there were no people in it at the time?
Westerhout
No! No people at all, that's why it burned down to the ground.
Sullivan
They just came out one morning and found it?
Westerhout
Yes, found it burned down. And it was sort of- you know the area around Kootwijk- if a shed burns there, ok, it burns, that's that. I don't know whether they actually came out one morning and saw it burned down, but it was quite obvious that I don't think it was particularly anybody’s fault. Although I have always had the feeling- people like Oort and van de Hulst would be able to give you more information about that- I always had the feeling that they didn't think much of the efforts of Mr. Hoo.
Sullivan
Well, indeed he wasn't getting very far, apparently. I mean certainly Muller got very fast, very quickly.
Westerhout
Yes, and, of course, Muller just had his Engineer's diploma. They got him as a new fresh guy and he got into it.
Sullivan
So it was while you were working on this paper that the line was discovered [Sullivan: 3/51], I guess?
Westerhout
I think so, yes. It must have been the same time. That was in '51. No, I think the paper was finished at that time or just about to be finished, putting the last touches on it. Because I was still busy working at that time with André Muller, the other Muller, assisting him in observing XE Cygni for his PhD thesis, so spending long nights at the Observatory doing photoelectric photometry. And I continued doing that also after the 21 cm line was discovered. I think the first Kootwijk detection was in May and I went out there almost immediately, a few days later because I was in essence the only student who was involved in radio astronomy at that stage. So I went out there to assist in the observing and then several other students went out. But I only spent a week or two there during that first period... the very first period. Isn't it in this BAN [Bulletin of the Astronomical Institutes of the Netherlands] here that we published that very original line profile- this one, yes. "The first receiver in the summer of 1951." Our switching frequencies were very close together. That’s why you always got that sort of a pattern when you change the frequency.
Sullivan
Yes, Muller showed me an actual strip chart which was about three weeks after the discovery. So then when did you actually get involved in radio astronomy again?
Westerhout
I'm trying to think how that worked because I then...
End of Tape 23A
Sullivan Tape 23B
Westerhout
The van de Hulst, Muller, and Oort paper was in '54. So in between there I spent 8, 9 months in South Africa. But somehow or another I had already gotten enough interest, and, of course, I'd worked closely with Oort on that paper, that I was kept very much informed by Oort in letters and he visited South Africa once and so on. So then I gave lectures and colloquia in several places about structure the 21 cm line and galactic structure in South Africa. In fact I wrote an article in the Monthly Notices of the South African Astronomical Society, a mimeographed pamphlet sort of thing on the spiral structure of the Galaxy as found for the 21 cm. That was in the summer or fall of '52. So by then there was already quite because a bit known, because before this Muller and van de Hulst article [Sullivan: 1954]. They were a few smaller things particularly in the Dutch Academy of Science which already had spiral arms in them.
Sullivan
There was one in Observatory.
Westerhout
And in fact, then on the way back from South Africa I stopped off for a day or two in Cambridge at [Martin] Ryle's place and talked to them. In essence, informed them about everything that was going on. So somehow or another I must have been kept quite well informed by the Leiden group about what was going on, mainly by Oort I would say.
Sullivan
And when you went back you jumped right in?
Westerhout
The guy who did most of the initial observing in Kootwijk was a man named [Walter?] Muller, whose name you might have heard.
Sullivan
No, I haven't.
Westerhout
He did a lot of the initial observing. He was also an undergraduate, I think, at the time. Anyway, he did a tremendous amount of the initial observing. And when I came back from South Africa in the end of November ‘52, all the data, I think, for the initial paper had been taken. And I still remember that at one stage, and that must have been in the Spring of '53, that data had to be reduced properly and all- you may have heard that story already.
Sullivan
I think it's in your paper in the New York [Sullivan: National Academy of Sciences]?
Westerhout
All the graduate students in essence were collected by van de Hulst. I can still see us sitting in the collegezaal or lecture hall, everybody had a stack of chart recorders, they were reduced and more things were done with them. I think that was in the spring of '53.
Sullivan
How many people were doing this?
Westerhout
Oh, I'm sure there were about 6 or 7 of us or so sitting there plus perhaps a few rekanaars, a few calculating people. It was quite a large group and as a result the thing got done in no time at all, like three days or so. That was, in other words, the reduction of the data to such a point that- and then I think van de Hulst took it over again and started working with it from there on. Then however the receiver had been considerably improved and we had already started the observations in Kootwijk for the big survey, which were done in a very systematic fashion. Muller had developed the system to a fine art so that then these profiles came out and in November '53 I came back from South Africa. So that's when I started getting involved in that. I think I more or less did nothing else anymore. One of the first things we did then was this rotation curve business together with [K. K.] Kwee, who was also a graduate student.
Sullivan
What has happened to him?
Westerhout
He's at Leiden.
Sullivan
He’s still at Leiden?
Westerhout
Sure. He's an expert on W Ursa Majoris stars. I mean it was the only thing in radio astronomy he ever did. And I think that also came out of that session in the lecture room where we reduced all that data. He sort of got interested. He was asked if he would take that on and so he took it on, and so he and I went out and observed pieces of profile and he did most of the reduction. And somehow or another we then finally came up with the final paper.
Sullivan
Now what about the actual observing at Kootwijk for the large survey?
Westerhout
Now that's a whole story in itself. That was great fun. I always remember that as something exciting. I don't know why, because it must have been God-awful boring, but I was young enough I guess to always find it exciting because I would spend weeks and weeks there. I was in- there was a hotel right next door, "Hotel Radio Kootwijk" in Kootwijk, and I was in essence just living in that hotel. And when I came in in the middle of the night, I'd go to the refrigerator and get myself some milk and what not. I remember once the hotelier saying, "Now look, don't put milk in our beer glasses, it ruins the beer glasses for good."
For that Meneer Zwaak or one of these people- I think it was Meneer Zwaak- had calculated these extensive tables, which must still be around somewhere in Leiden, for each - let me think how did it go- There were tables in the galactic plane for a start of azimuth and elevation- not for each day- as a function of sidereal time, of course. But all the scans in the central regions of the Galaxy were made as constant declination scans. And I think that was done because our initial set of tables contained only values for the galactic plane. And, of course, for constant declination scans you simply move the time. You add 5 minutes to the time and...
Sullivan
You move along the plane.
Westerhout
You move along the plane. Well, I have to think of it. They were constant declination scans so we didn't move at all. That's right, it was only later that we got sophisticated. Right, we had azimuth and elevation tables for the galactic plane only, so we would set at the azimuth and elevation for that particular longitude 10 minutes beforehand and then just let the plane drift through during that time. So we did not have to follow a point in the sky.
Sullivan
So you were integrating only with the natural drift rate, I mean they were drift scans really? You weren't following the source at all? Well, this is probably described in the procedure.
Westerhout
I’m trying to think, suddenly, I’m trying to think what the integration time, what the integration time was...
Sullivan
Ok, so in fact you did follow a point for 3 hours.
Westerhout
Yes, we did follow a point for 3 hours, but then we could use the same tables by just moving the time forward by 5 minutes for the next point on that constant declination circle. That's how it was. But then in the outer parts, after we'd done that first thing, of course, more had been calculated and we gained more experience, and we decided to do it at neat intervals of 2.5° in galactic latitude and galactic longitude. And therefore we had a set of tables for each point as a function of time. And what you did-that Würzburg had a motor to drive it in azimuth... In fact it had two motors. It had a motor to drive it in elevation also. But they were fast motors. And then there was a little crank sticking out of the wall for fine adjustments and there was a little crank sticking out of the floor, and the one at the floor was here [Sullivan: demonstrating] the one at the wall was here [Sullivan: demonstrating] and you looked outside and there was an indicator on the big circle and you looked through the floor, there was a hole, and there was an indicator on the azimuth then you stood there and you usually had to crank three or four times here, and three or four times there- We did that every 2.5 minutes. So certainly you were busy all the time. Then every now and again you'd write the frequency by one of those spikes that appeared every 10 kHz as the one-channel receiver slowly but surely swept through the line.
Sullivan
How accurate was its pointing actually? Just roughly. The beam was 1°or something?
Westerhout
No, the beam was 2.5°, so every 2.5 minutes it was better than a 10th of a beam width. I mean there was no doubt about it. I'm trying to think whether I calibrated - I think I did - on point sources. I made a number of calibrations of the positional accuracy of the telescope. Yes, I certainly did that because I also have a paper somewhere of an initial survey with that same telescope of the continuum radiation at 21 cm. Yes, that's right, I made a continuum survey with that.
Sullivan
Is this in the BAN?
Westerhout
Yes, it's also in BAN, There's an article in '56 in the BAN called "Search for Polarization of the Crab Nebula and Cas A at 22 cm Wavelength." In fact, I found the polarization Of the Crab Nebula, but didn't believe it so I said, it is certainly less than 1.5% Well, it was 1.2% or so. I mean, it was clearly there at the right position angle but it was...
Sullivan
But you didn't believe it.
Westerhout
If I had sat there for another two days I would have had it. Alas, that's one of those things, you know.
Sullivan
Is this in the paper, what you just told me?
Westerhout
No- well, what I just told you is in the paper. The result was negative.
Sullivan
I know but from the paper can you see...
Westerhout
Yes, from the paper you can see that I had it. Where the heck is that article on the distribution of radiation along the galactic plane?
Sullivan
Continuum?
Westerhout
Continuum - that material was used by Schmidt at the time to reduce his data for the central parts of the galactic plane. We then split the data up in two the parts, Maarten Schmidt's the central part and mine the other part. In any case, I think all that was to figure out who actually did the pointing calibration. But I'm sure I did the pointing calibration because there is a '56 paper on the galactic center and a '56 paper on the polarization and a '54 paper where it was Kwee, Muller, and Westerhout. So I must have done all the pointing calibration.
Sullivan
Who else was observing out there, students like you, for this survey?
Westerhout
I don't really know.
Sullivan
You did the bulk of it?
Westerhout
No. Because it took more than a year to collect all that data. So I certainly didn't do the bulk of it. I think there were a whole lot of students going out regularly.
Sullivan
Rotating?
Westerhout
Yes, it was usually two weeks at a time.
Sullivan
Well, what about the reduction of this data after it had all been gathered tediously over a year?
Westerhout
It was more gathered tediously over two years, sort of.
Sullivan
Did the reduction proceed in the same sort of "line everyone up in the room"?
Westerhout
No, the reduction was done in essence by myself and Maarten Schmidt with the help of several computing aides, both the old and experienced guys, as well as some young girls that we had, we would tease to tears every now and again. I remember one of them once threw an ashtray at our heads, one of these big, fat, glass ashtrays, which burst in a thousand pieces against the wall and then she ran screaming out of the room. I mean, heck, there were all these young graduate students teasing this poor girl who was sitting there measuring things with a ruler the whole bloody freaking day. That was a pretty horrendous job. What it amounted to was reading off the data from the chart record and tabulating them and fitting a baseline and subtracting it. Well, the whole procedure is given in that paper of course. Then Mr. Zwaak made all the second differences. I still remember that. At one stage I was always trying to get people interested in what they were doing, so I'd given Mr. Zwaak all sorts of- he was close to retirement, almost 64 or 65 and he'd been at the Observatory since the age of 12. So I was giving him nice graphs to make and I'd explain to him exactly what it was. Then at one stage I went to him with this enormous job for 600 profiles, each consisting of 150 points or so to make second differences. And I didn't quite know how to give that to him, but he had to do it. We had decided he was the man who could do that. And after a day he came back and he says, "Meneer Westerhout, I like that job. All those graphs, I really like this job." Oh boy, was I happy. He was really happy there. And he was one of the really good old fashioned people you know, he would make his little - when the numbers became too large and he couldn't do it by heart anymore, do you think he’d use Observatory paper? No, he used pieces of brown wrapping paper to make his calculations on, thousands of little pieces of brown wrapping paper spread around his desk every evening, which he brought from home.
Sullivan
Who was directing all of this? Was it really Oort that was coordinating all of the work that's in that BAN in '57?
Westerhout
No, that's what I was doing with the help of van de Hulst. Oort was relatively little involved other than in the scientific discussion of the matter. No, these were basically, you could say, two pieces of thesis research. One by Schmidt and one by myself. Even though neither of us bothered to make it into a thesis.
Sullivan
It could well have been.
Westerhout
Yes. But I was at that stage, of course, interested in the new telescope that was beginning to come up, the Dwingeloo telescope. And Schmidt got more and more interested in modeling of the Galaxy.
Sullivan
That was his thesis, the mass model?
Westerhout
Yes.
Sullivan
And yours, the continuum survey?
Westerhout
Right. Which is sort of paper number 12 or 13 on the list.
Sullivan
Before we get off to Dwingeloo stuff, is there anything more about this? You haven't really talked about the scientific interpretation of that. Was that sort of straightforward? I mean, it was the same sort of principles as were used in the '54 paper, it's just more data and more complete.
Westerhout
It was very much more complete and in particular, of course, there was a lot of discussion on the accuracy of the data and the very complete way in which we tried to remove the smoothing due to cloud velocities and so on, in defense of that, a big story about accuracies.
Sullivan
I've forgotten now, this sort of thing wasn't going into the '54 paper? Is that correct?
Westerhout
Yes, this didn't go into the '54 paper at all. The '54 paper only has a relatively short section on the reduction.
Sullivan
Well, maybe the way I should ask you is, other than the completeness which enabled you to get an obviously more complete picture, were there fundamentally different things in this paper from the '54 paper?
Westerhout
Yes. Fundamentally different things in that there was very much more detail available. And therefore this paper here, particularly in the conclusions in our interpretation and discussion, there are descriptions of each of the spiral arms, there's a discussion about random motions which, everybody overlooks. The first discussion about random motions, namely the fact that you see, when you look at the galactic anti-center, you see that there are features of 20 or 30 km per second, and I figured out supposing that there would be that same feature at longitude 150° or 140°, how much wrong would we place the spiral arm? And it came out to 2 Kiloparsecs, and I mentioned it here. And it was only very much later that people started coming up with that idea again, that those positions of those spiral arms weren't accurate at all, even though it said so right in the initial paper. And I think the reason is, of course, because it was too long a paper for people in general to read and absorb, like all Dutch papers.
Sullivan
Do you think that was a tactical mistake, perhaps?
Westerhout
Maybe it was. A lot of things there that sort of faded into the background because of such an enormous amount of work. Another basic new thing was, of course, the z distribution.
Sullivan
That's right.
Westerhout
The first paper was only along the galactic plane- we determined the z distribution, we determined the position of the galactic plane. Or rather I did all that. Schmidt used the data in trying to get near and far points in the inner parts separated, but I collected the whole lot together. I missed the fact that in the Southern Hemishpere, I mean I mentioned very precisely that in the Northern Hemisphere quite clearly the plane curves up tremendously, in fact, there's a picture in there which shows it. But I missed the fact that in the Southern Hemisphere it actually turns down. As a result, it's [Frank J.] Kerr and [Bernard F.] Burke in the same year.
Sullivan
The data was available?
Westerhout
Not really, but there must have been ... I mean when you look at it, you see it going up here and you see it going down here. So one could have...
Sullivan
You could have speculated?
Westerhout
Speculated, yes. But it was in that same year Kerr and to Burke to whom the discovery of that effect is attributed, even though it's quite clearly there and described in the paper.
Sullivan
What about the reality of all these spiral features? Did you believe in them too much then, I mean looking back on it now? Or did you really have the right idea that - or not the right idea, but a more modern idea that this needs to be taken not too seriously?
Westerhout
Well, since I knew how they were arrived at, I was fairly convinced that the contour map, this one here
Sullivan
The colored one.
Westerhout
The colored one was pretty good. In other words that, given the mass model of the Galaxy and so on, you knew that the mass model wasn't quite correct because at that time already Schmidt was busy on his PhD thesis, so we knew that the tail of the mass model, particularly for the outer parts, could flip up and down somewhat, which would move things in and out.
Sullivan
By changing the rotation curve?
Westerhout
Changing the rotation curve. I think I have a remark somewhere that such things as these splits in the spiral arm might not be actual splits but might be simply due to random motions. So I certainly was aware already at that stage that it was certainly not necessarily on small scale a true representation of the distribution of neutral hydrogen. On a large scale there was, of course, no doubt about it- when things connect there beautifully. And then, of course, this so-called artist's impression was quite a major effort. I think we spent a month on that, just day and night trying to figure out which is the best representation of that, looking at all... This contour map here is a projection on the galactic plane - no, sorry, it's the maximum densities in the z direction. Well, of course, you would have a spiral arm going up here and another one going sort of underneath it and it's only the underneath one which has more intensity that would be shown on here. And realizing that there was much more in all these charts which represent the real data than there was in this map, I decided to make that one up.
Sullivan
We're talking about plate A and B in the '57 group of papers.
Westerhout
So that really tried to represent everything there was in these bifurcations and so on, you still see in more modern things just as much as you saw in those old data.
Sullivan
So in other words you don't think you over-interpreted the distribution of the hydrogen, looking back on it now?
Westerhout
No: There was no over-interpreting in the sense that I simply represented what I had observed.
Sullivan
Do you think it may have been taken that way by other people? In believing every little feature too much? I mean, this is a very striking map- it’s even in color - so people might take that too much at face value at what you would really see if you were outside the Galaxy.
Westerhout
Yes. People were taking that far too much at face value, and in particular they did not read the paper that went with the picture, which made comments about random peculiar motions of clouds or cloud complexes which could change positions of things rather drastically. And, of course, objects like this here, these beautiful smooth spiral arms that you see, I'm thinking of the Sagittarius arm and the Norma-Scutum arm, sort of in the range of 4, 5, and 6 kiloparsecs. I know exactly how we got those features. We had some gas left over and we decided to distribute it evenly along the circle where it was probably located. And it said so in the Schmidt paper. People then right or wrong don’t realize that anymore. That's why later on, and even now, you see no detailed maps of the central part of the Galaxy. People have never redone the Schmidt work and the same work that Kerr did on the other side simply because it's too damn hard and we'll have to do a lot more modeling before we're able to do it. That's why you see that the Sagittarius arm on all these maps always has a dotted thing and another dotted thing for the Norma-Scutum arm. While in the outside people draw all these little lines and small connections because there it is much more unambiguous. It's quite clear that there are two major features going around here, but you can't say at all where to place it.
Sullivan
Ok, then this was published in '57.
Westerhout
Let me say one more thing about Kootwijk before we step off Kootwijk. You may have that piece of information already, but Muller told me once, and I certainly believe him, that he blames a good deal of the success of his receiver on the fact that he was working right in the middle of the Dutch transmitting station. And as a result he had to shield every single part of his receiver so unbelievably well that all the problems that people got later, who built 21-cm line receivers and got birdies and all sorts of things, all sorts of interactions and all these problems, Muller never had, from the beginning he never had them, because every piece of equipment had to be completely encapsulated or you would get something. And he was sitting right in the middle of a transmitting station. Funny that...
Sullivan
Yeah, he mentioned that to me.
Westerhout
He has mentioned that to you, Ok. I remember one man, one instance where one of the engineers said, "Now I’ll show you something neat." At that stage the Dutch still had their long wave transmitting broadcast at 1800 meters or something like that. There was this enormous antenna mast, with great big guywires and enormous numbers of insulators on it, and this was sort of a wet day, so he said, "Now come along to the bottom of one of the guy wires," and with a great big screwdriver in his hands and he held it by the guy wires and there came a huge big spark jumping over, and the spark was modulated, so in the crackling you heard the music of radio Hilversum. And it was in that environment that we were observing all that stuff. Unbelievable!
Sullivan
No, he did mention that. He didn't mention though, you said that other people did have a lot of trouble with birdies and so forth in the early days.
Westerhout
Oh, yes.
Sullivan
Now that I didn't realize.
Westerhout
[Harold "Doc" Irving] Ewen later then built a receiver for [Bart] Bok at Harvard and always had trouble with that. Always things here and there and everywhere. Anybody who built receivers in those early days had problems with signals leaking through for spectral line receivers. After all, this was the first spectral line receiver. If you have a birdie in a continuum receiver all right, it doesn't matter, your total noise goes up a little bit. In those early days there were lots of problems of that kind with the spectral line receiver.
Sullivan
So, about this time the Dwingeloo dish came into operation. I guess it was actually in '56, wasn't it?
Westerhout
Yes.
Sullivan
When it was commissioned?
Westerhout
That's right.
Sullivan
And did you immediately begin to work with that?
Westerhout
Have you interviewed [Ben G.] Hooghoudt?
Sullivan
No, I haven't.
Westerhout
Because he was, of course, completely in charge of that.
Sullivan
Of the building of it?
Westerhout
Of the building of that.
Sullivan
I'm afraid I won't get to him, at least this time I won't.
Westerhout
Because he'll certainly have a tremendous amount to say about all the various problems. I wasn't really much involved in the design of that thing at all. For one thing I had my hands full with this thing, of course. It wasn't until we actually started getting receivers ready for it that I started getting involved. And the first time we got involved was the two occultations of the Crab Nebula in November of '55, where Seeger at that stage had developed a very good 400 MHz receiver. It was more or less the first time- and I do not recall who thought of the idea that the Crab Nebula was going to be occulted by the Moon- I have a strong feeling that it originated in Leiden, but I can hardly believe that because I can't imagine who would have originated that. It must have been one of the clever chaps in Cambridge. In any case, that opportunity was grabbed. The telescope for the first occultation, was the beginning of November- this is the Dwingeloo telescope now- this was November '55 - could not move yet in elevation. It could already move with the fast motor in azimuth, but not yet in elevation. It was sitting vertically. For some reason or another it was not - no, the manufacturer must have done that for us, put it in a vertical position. The took occultation took place just after the Crab Nebula rose or just before it set, either one or the other, so it was relatively close to the horizon. So the manufacturer set the telescope for us with a big metal boom that stuck out from the edge of the telescope and thereby tightened it at an elevation of 7°. That's where the telescope set.
Sullivan
At your request?
Westerhout
At our request.
Sullivan
Where the occultation was going to be?
Westerhout
That's right. And the occultation however, of course, took an hour. So how do you follow? Well, we followed by moving the focus, the big pole on which the antenna was mounted, up and down. All that I calibrated beforehand and I was entirely responsible for that. In other words, I had to calibrate the telescope in azimuth and I had to calibrate the telescope in elevation. The elevation one was rather remarkable. One of the inventions that I had that also made me famous in the early days of Green Bank, namely the top guide wire was the one with which you could lower the boom on which the feed was hanging sitting at the end. So we used that lowering mechanism so that simply, if you can think of the dish here Sullivan: drawing at blackboard] and here's the apex of the dish, there's a box here, this wire came down here and then somehow or another there was a crank here. So I attached to that wire, a thin little wire that went down here, over a little pulley there because it was in the way somehow or another and down there again, and on here had a little pointer and I had a long ruler here, and that was the elevation scale which then had to be calibrated. Similarly in azimuth, we looked over various drawings and we found that there was one axle, one little axle coming up out of the azimuth shaft, which actually went around as the telescope went around.
We were not allowed to disturb the manufacturer. So we settled on that axle and we said, "Now, how are we going to read off that axle?" So I went to Ruinen, the nearest town, and bought an alarm clock. We dug into the alarm clock and attached it with tape and baling wire onto that axle and somehow or another attached the things that set the hands to that axle. So when the telescope rotated, the alarm clock hands go around ticking off the hours and the minutes. And I calibrated that in degrees of azimuth. That was an unbelievable system. So during that first occultation there was- after having done all that and made all those calibrations for which I think we only had two days because we worked on and off again, because we were disturbing these guys- we were actually able to point at the Crab Nebula and follow the Crab Nebula during the entire occultation. One guy standing upstairs with a table in his hand, which I had also calculated, and one guy downstairs with a table in his hand, cranking in azimuth and cranking in elevation. The second occultation...
Sullivan
A month or two later?
Westerhout
No, it was one month later- 28 days later, in fact. The elevation fast motors worked and we decided not to lower the boom anymore, but actually use the elevation thing. Moreover, it was at a different altitude. However, we still needed a calibration. This time we needed the calibration of the elevation angle. So somehow, on some member, I made markers to calibrate the elevation angle, and we fed up from directly out of the box in which the elevation motors were located a little cable out with a pushbutton and there was a lot of training involved in that because you could give it only tiny little bursts- and another 20 second later- oomph- another little burst of power to make it jump up in little pieces. That was the second occultation. So that was approximately half a year before the telescope was officially finished.
Sullivan
That was [Charles L.] Seeger and you and...
Westerhout
That was Seeger and myself.
Sullivan
That's all?
Westerhout
Yes.
Sullivan
And what were the results?
Westerhout
The results were two beautiful occultation curves of the Crab Nebula indicating that the center of the Crab Nebula - because the Moon of course, on those two occultations went through at different angles, so we could really get almost a two-dimensional picture- indicating that the radio center of the Crab coincided to within a small fraction of a minute of arc with the what was then assumed to be central double star, one of which we now know is the pulsar. And [Gijsbert] van Herk measured to unbelievable accuracy the position of the central double star, which had never been done before. In or so other words he took a Mount Palomar plate or so to the plate measuring machine and measured and applied all the corrections, attached it to the fundamental catalogues that were then in existence. So the position of that double star in that particular paper is in essence the standard position of the center of the Crab Nebula. I don't think anybody has done it with that sort of accuracy anymore.
Sullivan
And that's published in BAN?
Westerhout
That was a BAN article, right.
Sullivan
That's very interesting. I haven't heard about that.
Westerhout
That was published in '56. We published that pretty soon afterwards because we were all very excited, of course, about the whole thing. And that was absolutely unbelievable that that came off.
Sullivan
That it all worked.
Westerhout
Yes. Both occultations.
Sullivan
So then the dish came into proper use in '57 or...
Westerhout
In '56. In May of '56 or so, the Queen [Juliana] had to dedicate it.
Sullivan
Oh, she came out?
Westerhout
Yes. Oh, you haven't heard that story?
Sullivan
I knew about her coming to Westerbork, but I didn't know she had gone to Dwingeloo.
Westerhout
Oh, yes, she officially dedicated the telescope and it was all beautifully rigged. And the last few weeks we lived there day and night, Hooghoudt and I mainly again. At that stage I got involved because there was a lot of astronomy to be done. The automatic pilot, which I presume is still there, probably still sitting there, in Dwingeloo. Have you ever seen that thing?
Sullivan
Not knowing that I have, anyway.
Westerhout
I mean it's the big gray thing that's sitting in a box on the floor in the observing cabin, which looks a little bit like a telescope with two axes.
Sullivan
I don't remember but it was four years ago that I was there. I haven’t been there since I’ve been in Holland, I mean in the telescope itself. I’ve been in the lab.
Westerhout
No, I'm sure it's still sitting there. That was a masterly invention of Hooghoudt's, I think- Hooghoudt together with Rademaker. It was an analogue computer converting right ascension and declination into azimuth and elevation simply mounted, in essence, like a little telescope. Just two sets of...
Sullivan
There was a similar thing on the NRL [Naval Research Laboratory] 50 foot.
Westerhout
Right, except that one was unbelievably sloppy. The internal accuracy of the pilot you will find in my thesis paper. I calibrated that whole thing, first internally and then its connection with the telescope.
Sullivan
But anyway, back to the Queen.
Westerhout
That’s right. I’m trying to- Muller at that stage had moved to Dwingeloo and installed his receiver in there. And the day came nearer and nearer and we couldn't point that telescope and there were all sorts of things wrong.
Sullivan
But why did it still matter for the Queen? She wouldn't know.
Westerhout
Well, you know, the thing had to work. Somehow or another, the thing had to work. In fact, the first line profile was obtained the day before the official dedication-showing that the receiver worked which was rather important.
Sullivan
It was a line receiver, the first one that was on there, besides from your occultation?
Westerhout
Yes, that occultation thing was at 400 MHz.
Sullivan
Yes.
Westerhout
Then the line receiver went on. We had a recorder outside with a table, a recorder on it and a great big gold-looking...
Sullivan
Westerhout on 22 November ’73. So the Queen pushed the button and then what happened?
Westerhout
The Queen pushed the button and the button was connected to the pilot and that should start the automatic pilot. However, that at the last minute didn't work. So we had one guy from the electrical company that was doing the installation and one of the technicians inside the telescope and an hour before the Queen came connected a red lamp to the button. So when the red lamp went on inside, they were supposed to move the telescope into the standard position, which is the position of our standard reference field which had a very beautiful profile. And Lex Muller had set his receiver extra fast. Ok, it would be a bit noisy, but within 10 minutes you could see the whole profile come up on the recorder.
Sullivan
The Queen didn't know that these little men were behind the...
Westerhout
No. So the Queen pressed the button and the press was there and, of course, there were hundreds and hundreds of people there. And I had told the press very precisely how the telescope would move so they had all their cameras in the right position. And first nothing happened. Then the telescope very slowly started moving in the opposite direction. Then it started moving a little bit faster in the opposite direction. Whereupon the press grabbed their film cameras and started running. Well, Lex Muller and I, no Ben Hooghoudt and I- Lex Muller was standing there beside Oort- Ben Hooghoudt and I sprinted into the telescope. By the time we got in there the technician and the electrician man were absolutely and utterly confused and dumbfounded. They had done everything they were supposed to do wrong. They were so nervous. Fortunately, Hooghoudt and I were so familiar with the equipment that we started pressing buttons and the telescope then moved, whereupon the press had to run once more to the place where they had been told to go. And from then on everything worked fine.
Sullivan
So then you went to ?=150° and b= 0°? [Sullivan: ? = 50°]
Westerhout
b = 0 and a beautiful line profile appeared on the chart and the Queen got presented with the chart. Then to our horror the Queen insists - the Queen was then, of course, shown the inside of the room, of the receiver racks and so on, then she insisted she wanted to go up to the platform, up those funny stairs, in her white shoes and white dress. And we knew that the previous evening the bannisters had been painted with aluminum paint. When she came down from those stairs, I still remember the horror with which - I was standing there helping her - and those last pieces of the steps were very funny sort of steps, I was helping her down those last steps and she looked with horror at her white gloves which were absolutely and utterly black.
Sullivan
So you hadn’t told her about the paint?
Westerhout
Well nobody dared! Well, the paint wasn't wet anymore but it was sort of - it rubbed off rather easily. The paint we only thought of later. People were horrified that she wanted to climb the stairs.
Sullivan
You hadn’t thought of the paint.
Westerhout
We only thought of it about half way and said, "My God." Ah, beautiful... that was in May. Then, of course, the work really started, because that was the dedication.
Sullivan
But it had the line receiver first of all?
Westerhout
It had the line receiver, but of course it then took a long time before we finally started observing with it. Because at that point it had to be calibrated, many of the electronic things weren't working properly yet, I mean, the steering mechanism and all that. So we did all the calibrations which includes, of course, a lot of optical observations, because I calibrated and checked the steering mechanism by means of optical observations. I attached a small telescope to the thing
Sullivan
Not with a camera? With a telescope
Westerhout
A little telescope and cross-hairs. Somebody downstairs set on Alpha Orionis or whatever star you have, and the telescope would move there and I'd find out how far off it was- we had graphs all over the sky- how far off it was with respect to that telescope. We hadn't quite heard about rigidity in telescopes yet. But that, of course, checked the complete servo loop and the accuracies of that.
Sullivan
How did you get involved in continuum survey now? It would seem like you would have continued with the hydrogen line.
Westerhout
No, because then, of course, we had to calibrate the thing on radio sources. And in the meantime the manufacturers still had to work on it for another month. That month I went to Ireland to sort of get engaged.
Sullivan
To meet a wife?
Westerhout
Yes. This was the year after the IAU [International Astronomical Union] meeting. This was in '56. When I came back I found out that in periods that the manufacturer was not there, Henk van de Hulst had decided that he’s simply turn the thing at full speed in azimuth. You know, for a quickie survey. And that's how such sources as W3 got discovered.
Sullivan
I see.
Westerhout
So I was - when I came back I was presented with this unbelievable stack of continuum data. "Ah," said van de Hulst, "Every now and again the guy wasn't there so I decided we might as well."
Sullivan
So the continuum receiver had been put on to calibrate point sources?
Westerhout
For point sources, yes.
Sullivan
So van de Hulst was really the one that got it started that there were these interesting galactic sources all over?
Westerhout
No., No, van de Hulst simply felt that somehow it was a pity that the thing was sitting idle for parts of the day when the manufacturer was not working on it. So he said, "Let's just go through it." Actually out of that survey I think four sources came, out of the whole thing.
Sullivan
Including W3 though?
Westerhout
No, there were a few sources in that list that do not occur in the strip, in my W list. A few sources that do not occur in the strip of sky that I actually mapped very carefully. They came out of that other fast survey.
Sullivan
So then it was a few months later before you actually began?
Westerhout
No. I then did the final calibration of the telescope with point sources including measuring extinction, refraction, bending, the whole lot. And that, of course, all required a continuum receiver. And then I immediately followed that with two weeks of continuous observation of the galactic plane. And that was it.
Sullivan
That all it took was two weeks?
Westerhout
Yes. And then the line people came on. I quit.
Sullivan
And you went back and reduced all that?
Westerhout
I went back and reduced all that. So in October of '56 the line receiver was used and among other things they looked at the Andromeda Nebula, which is in an article by [Ernst] Raimond, van Woerden and van de Hulst.
Sullivan
And they did the expanding arm?
Westerhout
They did the expanding arm thing, right.
Sullivan
But I still don't quite see how you got in this continuum business. You say it was necessary to calibrate the sources, but what was the motivation behind looking in the galactic plane for continuum sources?
Westerhout
I wanted to get a good survey of the galactic plane. I don't know, let's see, why was I interested...
Sullivan
Because you'd had all this line background? Now, at this time you were displacing the NRL dish as the largest microwave dish, right?
Westerhout
Yeah, right.
Sullivan
So maybe you just realized that this was the dish to do something like that with, since NRL had picked up these H II regions?
Westerhout
[Affirmative]. A few.
Sullivan
In '54.
Westerhout
Yeah.
Sullivan
Yeah, a hand-full.
Westerhout
Now that I come to think of it ... Well, for one thing I'd done the same thing...
[Short interruption]
Westerhout
I was interested in the continuum for a long time before. After all I did make a survey of the galactic plane with the Kootwijk dish in the continuum. And I did these polarization measurements, of Cas A. And, of course, wait a second! The original paper with Oort 1951, which was continuum. Of course! Well, that's where it all came from. That's how I kept the interest...
Sullivan
But that was background, as opposed to discrete sources? But did you realize that you were really - were you going for discrete sources or were you just going for whatever was there?
Westerhout
No, no. I wasn't going for discrete sources... and I found all these discrete sources. And that letter that you gave me a copy of shows where I tell Martin Ryle that we found a lot of discrete sources in the Milky Way which was somewhat unexpected. Because the earlier survey had no discrete sources.
Sullivan
Which earlier one?
Westerhout
My earlier one with Kootwijk with the 2.5° beam. I mean, you could see that now that, you know where they are, they were there all right, the bright ones, but they were I mean sort of smoothed out. I mean you didn't have a very good noise figure and all that. So that indeed came from wanting to continue on. Don't forget that this was only three years later. In '51 was the paper with Oort on the distribution of gas. In '54 I found out that at 1400 MHz at least, the Milky Way was extremely narrow in the continuum. At that point, in other words, we realized our mistake. And I then went on from there as soon as the Dwingeloo dish was ready. I wanted to do the continuum survey. And that in fact is what I wanted to do for my thesis and that's why I didn't make the other thing, the 21 cm line thing my PhD thesis. So that is how my thesis paper comes to have such a lot of calibration stuff in it. [Sullivan: Westerhout looks at his 1958 paper]
Westerhout
Here is the calibration of the pilot. It was the whole telescope, determination of the radio axis.
Sullivan
Which was then used by everyone afterwards?
Westerhout
We didn't think that the mirror would bend- in fact it didn't- but we sure figured out that the mast bends.
Sullivan
The old guy wire in there and everything.
Westerhout
Yes. No, but it bent actually.
Sullivan
Yes, Muller has told me a lot about this whole arrangement and how they finally put in a front-end box and various things like that.
Westerhout
[Sullivan: Still looking at paper] Antenna pattern, antenna receiver, detector law- the whole damn lot, intensities as a function of equivalent air mass.- in other words the extinction business- intensity ratios of the four bright sources, then we finally get the measurements. Oh, here’s the story about this first…
Sullivan
The Kootwijk?
Westerhout
No, this first quick thing. "When adjustments to the telescope with a drive mechanism were still in progress a search was made for discrete sources over the whole physical sky. The pilot wasn't in operation yet. The only possible motion was in azimuth and altitude, 72° per minute." How about that for finding sources! "Every discrete source in intensity greater than 30 units was found as a sharp spike well in excess of the noise peaks." Oh, 30 units, sorry, that is 130 flux units, every source brighter than 130 flux units.
Sullivan
That's why you only pick up a couple?
Westerhout
Yes.
Sullivan
Ok, what's the next step after this paper?
Westerhout
This is a neat paper here, it's still a neat paper- you can say what you like.
Sullivan
In fact we used it for this recombination line paper [Sullivan: Sullivan and Downes 1973 A and A]. We got a good total flux for W3 out of it after changing the calibration for Cas A, which was ~30% off or something like that. Other than that it's still the best measurement of that.
Westerhout
My calibration for Cas A was 30 percent off...
Sullivan
Yes, it turns out.
Westerhout
Interesting.
Sullivan
I'm not quite sure how that happened.
Westerhout
It's not 30 years ago. It goes at 1.5% a year.
Sullivan
No, no. I mean at that time it was 30% off. So you need to change all the fluxes there by that...
Westerhout
Oh, I had forgotten that. Now that you mention it, I seem to remember that that was indeed the case.
Sullivan
So what's the next step after this? What did you work on next?
Westerhout
Well, I worked on this- it kept me pretty well occupied for the next two years.
Sullivan
You didn't take any more new observations?
Westerhout
I didn't take any more new observations but I did... I’m trying to think of the chronology there-I did not participate actively in the line work with the Dwingeloo telescope other than, particularly in the beginning, very strongly of course in an advisory capacity and always working with the people on the subject. But I got much more involved in the various continuum things, you know, the continuum work, Seeger's continuum work, and my own, of course, for those two years. I think that's what mainly kept me out of it, working out that survey. Wait a second. That big BAN that appeared in '57. So that was still being prepared for publication, too. That's why my thesis didn't appear until '58, right.
Sullivan
So there were two big papers?
Westerhout
Yes. Two big papers both being finished at that time. So that's what kept me busy for those years. Then in '58, in the summer, I got my degree. I forget what I did after that. In any case, early in '59 I went on a trip around the world.
Sullivan
What kind of a trip?
Westerhout
Just a trip, just to take a trip. I had a NATO [North Atlantic Treaty Organization] fellowship to visit observatories in the United States and I got another kind of fellowship plus a salary from CSIRO [Commonwealth Scientific and Industrial Research Organization] to visit the Australians. So Judith and I and Magda-Kathleen made a trip around the world. We spent five months in the United States and three months in Australia, something like that. Oh, Frank Kerr was in Holland for half a year in '57 and I worked very extensively with him on the 21 cm line work.
Sullivan
Yes, tying together that.
Westerhout
Yes, trying all that together, right. Oh, there's a beautiful anecdote. We tied it a together particularly comparing a considerable number of profiles of his with profiles of ours very carefully. And finding to our great pleasure that when we took the ratios- I think the ratio of his temperatures scaled to ours was 0.98 ± .03. And it wasn't until half a year after he was back in Australia that he wrote in a letter, "By the way, you remember our beautiful arrangements, could you let me know were your antenna temperatures perhaps brightness temperatures, because mine were antenna temperatures and I think yours were brightness temperatures?" And ever since there has been this factor of 1.30 between the Australian and the Dutch data.
Sullivan
Which Ron Harten was very involved in trying to figure out.
Westerhout
Right, and apparently he did figure it out in the end what did go wrong there. But in the '57 session we decided it agreed beautifully except he talked antenna and I talked brightness temperatures.
Sullivan
And this is also where you presumably saw the difference in the rotation curves, the south and north?
Westerhout
Yes, right.
Sullivan
And that's when the Monthly Notices review article came out?
Westerhout
Right and then in '59 in Australia, Frank Kerr and I finished off this article for Kuiper’s Compendium [Sullivan: Vol. VII] among other things. We finished that off and we finished off the series of articles in the Monthly Notices with Gum and so on, on the position of the plane. In '58 at the IAU meeting in Moscow, the IAU decided that a new system of galactic coordinates should definitely be adopted. At the IAU meeting in '55 we had already talked about it. We set up a committee and it wasn't until after the IAU meeting that they discovered that I wasn't a member of the IAU at all and there was an official member of the committee. So apparently you can make a person a member of the IAU, the Executive Committee can do that in between sessions, so they quickly made me a member of the IAU. To come back to that meeting in '55, of course I had the model of the Galaxy which I am sure you can still find in Leiden, somewhere in the attic. The outer parts of the Galaxy are all these maps of these ones on the BAN No. 475, which gives intensity as a function of distance and...
Sullivan
Velocity?
Westerhout
No, distance from the Sun in kiloparsecs and height above the plane.
Sullivan
I see.
Westerhout
It is a cross-section in actual spatial coordinates. Now, I had each of these drawn on Plexiglas, each of they were those. I think they were originally this size. Then I had a great big Plexiglas sheet with grooves cut in it and we drew all these up, colored them, and stuck them all in. So when you looked you could see these sausages whirl around in that great big model.
Sullivan
I've never seen it but I've heard about this.
Westerhout
And that was in '55 already that we had that. That's interesting, this article didn't appear until '57. There must have been a lot to be done, in writing it up quite obviously. I took that to the Dublin meeting and I still remember coming back into Holland, the customs man wanted to know what was in that and I said, "A model of the Galaxy." He says, "A what?" So I had to unpack it. He says, "How much is it worth?" So I figured out the cost of the plastic and the time and I said, "Oh, about 10,000 guilders." "Oh, boy, that will be a lot of import duty." I said, "Come on now, I took this thing out of here three weeks ago." Well, it took a lot of convincing, but finally he agreed. He said, "Can you see anywhere where it says trademark so and so?" and I said, "We don’t have a trademark at the Leiden Observatory." But I got it back into Holland safely without having to pay 10,000 guilders worth of import duty. OK, where were we? My trip around the world?
Sullivan
Right, and that Compendium article was actually finished off in '59 even though it didn't appear until '63 or '64 or something like that?
Westerhout
Yes, right.
Sullivan
And then you got involved, I guess, in polarization in '60, is that the next step when you got back to Holland?
Westerhout
Yes. You want the Dutch story first before you get to the... oh no, you're just stopping at '58?
Sullivan
No, no, that was the classics book. I'm going to the mid-'60s or so with the history.
Westerhout
Because the trip around the world is another whole story in itself.
Sullivan
Well, tell me.
Westerhout
But later we should go back to that...
Sullivan
However you want to do it, Ok.
Westerhout
So when I got back in November of 1959 the 400 MHz receiver was almost ready. That had an enormous amount of headaches attached with it because Seeger on the one hand was a perfectionist in certain aspects, and in other aspects he never got anywhere in organizing things. So that took months to get that thing working and on the air. That was a terrible... hold everything... that wasn't '58. It was in '57, yes, we got it on there again, I think. Oh, my God, I'm getting awfully confused now.
[Break]
Westerhout
The survey that was published in '65, Seeger, Westerhout, [Robin G.] Conway, and [T.] Hoekema, we did in '58.
Sullivan
Before you went on your trip?
Westerhout
Before I went on my trip. So that's where that year that I couldn't account for went, the troubles with the receiver. But it finally did make that survey. That's right. In essence, I left Hoekema with the reduction, that's why his name is on it because he did a tremendous amount of work on that. Then later Mike Davis appeared in Leiden and he took a little bit of that, the sources out of on there. So that's where that went. And then in '60 we started on the polarization, and that again was an enormous amount of headache. In fact, that was so much of a headache that in the end on that first polarization paper even though it was Seeger's pet, l am the chief author because of the fact that in essence, in the end he was nothing more than a technician. I mean he lost all contact with the real world. And he left immediately afterwards, he left Holland.
Sullivan
And when was that?
Westerhout
That was in '61.
Sullivan
Then he went directly to - where is he now- New Mexico...
Westerhout
No, he went to Bracewell's place.
Sullivan
Oh, yes, Stanford.
Westerhout
Right.
Sullivan
But now that first survey is the one that has the nice fold-out with the optical things on it, an overlay showing where the constellations are and it labels the sources? That has Seeger's name, but I can't remember who else.
Westerhout
No, that's the one in the... Seeger, [F. Louis H. M.] Stumpers, van Herk, Philips Tijdschrijft.
Sullivan
That's the same survey?
Westerhout
That is same survey
Sullivan
But that was also published in BAN?
Westerhout
But then in '65 the whole description, the reduction and everything and so on was published in the BAN.
Sullivan
For seven years that was the only information, or maybe for five years?
Westerhout
That map? Yes.
Sullivan
Yes. And what were the main results from this? Was it just higher resolution at the low frequency?
Westerhout
Yes, quite, high resolution at the low frequency.
Sullivan
Yes, picking up all the discrete sources. But now what about the polarization, or after your trip anyway?
Westerhout
Well, the polarization business, of course, was extremely interesting because of the fact that we actually for the first time made a positive detection of polarization.
Sullivan
Of background radiation?
Westerhout
Of background polarization.
Sullivan
But now what about the Russians? Didn't they claim...
Westerhout
Well, [Vladimir] Razin had claimed that he had detected polarization at 240 MHz and so on. But in one of those typically Russian papers that did not say at all how much, where he had looked, the only thing it said is the method he had used. Wide band, narrow band.
Sullivan
Band shifting.
Westerhout
Right. And nobody really trusted that.
Sullivan
But was he right? I mean has it turned out to be that...
Westerhout
No, I don't think so. There was Thomsen in England who had some vague indications that there might be something. And [Joseph L.] Pawsey and [E.] Harting in Australia had tried and got negative results.v
Sullivan
At the same low frequency, I mean roughly?
Westerhout
At the same sort of frequency, yes. And we did it and got beautiful results.
Sullivan
And you were working at 400. Now at 200...
Westerhout
Well the Faraday rotation is so much worse because it really goes rapidly with wavelength. One cannot really think of Razin having actually seen something.
Sullivan
So then indeed you were the first ones to establish it reliably, and that was at 400 MHz?
Westerhout
Right. The introduction says something about that.
Sullivan
So in the '62 BAN article you mention all these earlier attempts and you don't really say that you don't believe them, you just say that Razin claimed a couple percent?
Westerhout
Razin and Thompson obtained positive results- two upper different papers. The other authors gave upper limits of 1-2%, at frequencies between 200 and 410 MHz.
Sullivan
And so you took this as a verification of...
Westerhout
The start of this paper very strongly makes it clear that we did this specifically to verify synchrotron theory.
Sullivan
Right, for the background radiation.
Westerhout
And we were sort of then, of course, it turned out that there was much more polarized radiation than you actually thought. Then it turned into a whole new field, of course, but that's another...
Sullivan
And what did you do with that in this paper when you had more then you expected?
Westerhout
Well, I gave a whole story... well, it's not so much... No, let's put it this way. We were rather surprised to find such strong signals, but then in the course of the analysis I had to explain away the fact that the signals were actually so low. So I was surprised how beautiful it was. We came out with in essence to the conclusion that the radiation must come from regions very near to the sun, within a few hundred parsecs at the most. Because of the Faraday rotation in the interstellar medium, even with normal ionized gas you will get lots of Faraday rotation that would completely smooth it and smooth it away.
Sullivan
But it is true, is it not, that [Cornell H.] Mayer et al. were the first to detect polarization other than on Jupiter and the Sun?
Westerhout
Yes, Crab Nebula and Taurus A, that's '57 or so.
Sullivan
Ok, I just wanted to check that. So this represented altogether-- a good year or two of work, I guess altogether in the early ‘60s?
Westerhout
Yes.
Sullivan
And you only did that one frequency though?
Westerhout
Yes. Because as you see this article was published in '62, July 6, and I arrived in Maryland on '62 April 11. So that was the end of my involvement in the Leiden effort with the exception of the paper on the 400 MHz survey which didn't appear until '65 at Leiden. I had all the data but I just never got around to writing it up. When I finally had written it up, it turned out to be a massive paper. That's probably why it took so long.
Sullivan
Would you be willing to comment why you chose to go to the States or would you rather do that off the record? I mean, it seems like you were getting all sorts of interesting results here. Or maybe it was just a matter of personal...
Westerhout
It was mainly a matter of personal things. In the first place I don't feel- I've always felt and I still felt at that time, that one should not stay forever at the that place where one got ones education. And that became, of course, more and more clear. As time went along and I became a senior scientist but yet quite clearly in the eyes of the powers that be, I was a student. That was one. But I think the main one was that having travelled through the United States and having seen all the many things that went on there, we in the end decided that Holland was too narrow.
Sullivan
Too confining.
Westerhout
Yes. And I wanted to start something, in essence I wanted to start something for myself. That's why also to everybody's amazement, I accepted the offer from Maryland rather than going to Berkeley or to NRAO which were the other two I was very seriously considering. In fact I was considering those and Berkeley already thought I was coming, and Maryland came up with an offer.
Sullivan
Where you could actually just start something for yourself?
Westerhout
Where I could really start something for myself. So I first enquired around Holland and van de Hulst said, "It's a football college- you're crazy." So I simply went there and looked around and saw the Physics Department and the enormous vigor with which that went.
Sullivan
You noticed what?
Westerhout
Vigor which that Physics Department had. That clinched it.
Sullivan
Were there any other astronomers there when you went there?
Westerhout
Uco van Wijk had arrived that September before.
Sullivan
But it had no direction as being a department specializing in radio astronomy?
Westerhout
No, none whatsoever. No plans.
Sullivan
That was essentially because you went.
Westerhout
They also had already hired [William C.] Erickson.
Sullivan
This was about simultaneously?
Westerhout
Yes. Erickson had already said yes before I said yes. But then Erickson had already committed himself to go to Holland for 14 months to guide the Benelux Cross antenna project.
Sullivan
So he was away?
Westerhout
He was away that first year. In essence from there on van Wijk, Erickson, and myself were the people who were attracted by the then-physicists, and I took over from there.
Sullivan
van Wijk is originally Dutch, I suppose?
Westerhout
Yes, he was born in Indonesia.
Sullivan
He didn't live in Holland then?
Westerhout
No, he didn't live any extended time in Holland.
Sullivan
So that was just sort of a coincidence?
Westerhout
Yeah, that was a coincidence. Elske Smith similarly is a coincidence. She never lived in Holland either.
Sullivan
She lived in South Africa?
Westerhout
No. She was a diplomat’s daughter. Her mother was English and her father was Dutch and she was born in Morocco and lived a long time in England and studied at Ratcliffe. Went to South Africa as a graduate student with Bok, that's where she did all her polarization work.
Sullivan
I see, I didn't realize that.
Westerhout
And Henry Smith, of course, was a graduate student at Harvard.
Sullivan
What was your main thrust at Maryland?
Westerhout
I never set out to make Maryland a department that was interested in radio astronomy. Particularly, because I, of course, grew up in a department that was an all-around astronomy department. I guess because of my name a lot of people did come, but you may note that I was mentioning Erickson and I having been attracted there, that the first people who arrived on the scene after that were [Roger A.] Bell, Smith, [Donat G.] Wentzel...
Sullivan
That's getting somewhat later.
Westerhout
Is it? Who else have we got?
Sullivan
I think those are the only early ones, before '66 or so.
Westerhout
And I was trying desperately to attract such people as [Rudolf] Kippenhahn and so on to come, but they wouldn't budge.
Sullivan
Kippenhauer?
Westerhout
Kippenhahn. I mean stellar atmosphere people, stellar interior, stellar evolution.
Sullivan
That's right, you told me you were trying to get Böhm.
Westerhout
Like Böhm and so on, right. We tried Kahn too. We lot tried every Tom, Dick and Harry under the Sun.
[Interruption]
Sullivan
But as it turned out, Maryland got a radio reputation.
Westerhout
Yes, when you come to think of it, why?
Sullivan
Well, I think the radio people just ended up being a little bit more dynamic than the others.
Westerhout
Yes, but that was only me for a long time, and Erickson.
Sullivan
And Erickson, yes.
Westerhout
But Erickson always had his business out in California.
Sullivan
But you and Erickson were somewhat more dynamic than Smith and Bell, then Kerr came in and well... but I agree with you when you look at the people, it's really sort of half and half.
Westerhout
Yes.
Sullivan
But now what about your research direction?
Westerhout
At Maryland?
Sullivan
Yes. You must have obviously seen the 300 foot?
Westerhout
Yes, I saw the 300 foot, quite. I mean I was one of the very first people to work with that together with Bernie Burke who drove his truck out there, his trailer with the whole multi-channel receiver.
[Interruption]
Westerhout
And I participated in those measurements with Burke and [Merle] Tuve.
Sullivan
The first things you did, were they actually part of the survey or did you do some other small projects on the 300 foot?
Westerhout
No, I wasn't immediately, I didn't immediately...
Sullivan
With Gart Westerhout on 22 November ’73.
Westerhout
This was with Bernie Burke and Tuve, we started in the winter of '62 already and one thing I did was get a lot of line profiles along the galactic plane and in particular the Perseus region. And that's the work that Jim Rickard reduced and got his Master's thesis on. That was a terrible headache because it was all on flux state and all sorts of errors in it and a lot of just chart recorders in typical DTM [Department of Terrestrial Magnetism] fashion. I think I then slowly, but surely got involved in the survey. And I, of course, got very much involved in the initial stages and the debugging of the auto-correlator.
Sullivan
The 100-channel, yeah.
Westerhout
Yes, the 100-channel correlator, the first one. And in fact the initial tapes from that auto-correlator in the first few months, the tapes went to Maryland because there was no computer at NRAO. There was a correlator and a tape recorder, but no computer. There was a 1620 desk sort of computer which, however, of course couldn't read tapes. So [Art] Shalloway rigged up something that connected it in that could read it bit by bit. But in essence we checked those very initial tapes to find out if was there anything on it. We had a little box with iron filings and we could then through a magnifying glass see the actual bits on the tape. That was in the summer of '64 and a few months later they got their 7040.
Sullivan
That was the first summer you spent out there?
Westerhout
No, I spent the summer of '63 there again with Burke’s equipment. The first winter of '62 we didn't do too much, it was more trying things out and so on. But then that summer we spent several months getting 21 cm line profiles with the DTM receiver.
Sullivan
But you didn't publish any of this?
Westerhout
I didn’t publish any of it, no.
Sullivan
In fact, really none of this has been published in journals.
Westerhout
No. There some of it in symposia reports by Burke and some of it, of course, in the Carnegie Institution stuff. Well, what of Carnegie has been published in journals? Very little.
Sullivan
But I was just thinking even of all of your hydrogen work, none of it’s been published in journals.
Westerhout
No.
Sullivan
You had the two additions of the survey, and now the third one.
Westerhout
Yes, quite correct. I more or less stopped publishing extensive papers since I came to Maryland, that's quite correct. And I hope now that I'm off administrative duties that I'll be able to correct that. Even though I have quite a list of papers after I did come to Maryland, most of those are either review papers or papers with other people or what have you.
Sullivan
What was the motivation behind the large survey? I mean one can think of a couple of obvious things, but was it the next step from Kootwijk I to Kootwijk II and now this would be the one that...
Westerhout
Yes. In Dwingeloo they never got around to making a complete survey. So I decided let's skip that step and do it immediately with a large telescope and I know this is going to take a number of years, but so what, so it will take a number of years. Actually it took longer than I expected. In other words use the telescope with the highest resolution available for as wide a region of the Galaxy as possible. And it was quite clear that we have to get down to the details now.
Sullivan
And of course it's quite suitable for a survey instrument also.
Westerhout
Right. The main motivation was, well, as you have noticed from most of my papers, I think they are all survey papers, I'm that way motivated. I like to produce something that is useful more than once, not just to me but to a lot of people. I've been doing that in essence in a whole lot of my research and I wanted to do that specifically with that and I defended the surveys specifically on that basis, service to the community we needed. I'm interested in the Galaxy myself quite obviously. But there is such a wealth of material that you should get at it in a systematic way or you'll never get it.
Sullivan
I just thought of one question that [Peter G.] Mezger commented on a little bit this morning, namely the early days at NRAO [National Radio Astronomy Observatory] there was various friction between the universities and NRAO, the former thinking that the latter wasn't worth too much. Now you were a university user of it in the early days. Were you not agreeing with these people?
Westerhout
Of course, I was very strongly in disagreement with those people because I felt NRAO - don't forget that I, of course, came from a university where there was a national facility that could be used by that university and by anybody else. I was already aware of the advantages of that sort of a set up. Well, right from the start I felt that if you want large telescopes you should do it nationally and not spread the interest all that widely. So I was very... no, it was indeed true that initially because of some bungling with the 140 foot and so on, things didn't go as rapidly as perhaps they should have at NRAO. But even initially NRAO did quite a bit of pioneering work. Some of it didn't quite come off well.
Sullivan
Well, there was a period though, I mean the first couple of years after the Tatel telescope, yes, but wasn't there a period of from sort of '60 to '64 where there wasn't a whole lot coming out of NRAO?
Westerhout
I was going to say for the first years of the Tatel telescope there was quite a bit coming out at that point. Then, of course, came the 300 foot when it was clear that the 140 foot would take much longer. In fact, the Tatel telescope was built as an after-thought.
Sullivan
That's right. The 140 foot was going to be the first one.
Westerhout
Was going to be the first one, then they decided let's put a smaller one up, too. Thank goodness they thought, they decided that. And then, of course, the 300 foot was built out of surplus funds more or less. Not quite, of course, I mean they had to have permission and all that.
Sullivan
That was very successful.
Westerhout
An unbelievable masterpiece, that telescope.
Sullivan
Especially when you look at the cost of it.
Westerhout
Yes. Well, not only the cost but everything that could be done with it. The thing that was wrong with it was not the telescope, but the damn astronomers. Not only at NRAO, but in particular the damn astronomers everywhere else who said, "I don't want to use that telescope because it's a transit telescope and I want to be able to follow the source." The things that could have been done with that telescope that weren't done because people just were too lazy.
Sullivan
Too lazy to add up different days...
Westerhout
Yes, unbelievable. I have never understood that and I still don't.
Sullivan
Well, shall we go back to the trip around the world? I'm interested in your comments about what was going on then.
Westerhout
During that trip, of course, I also visited NRAO and in fact, I was the second outside user of NRAO. George Field was the first.
Sullivan
I've seen your thing on the 8000 MHz survey. You had a little write-up, I think for URSI [International Union of Radio Science] or something, describing whether it would be feasible to do a survey with the Tatel telescope, a continuum survey.
Westerhout
I did?
Sullivan
Yes, I found that somewhere, I can't remember where. I think it was- 8 GHz sticks in my mind.
Westerhout
Yes, right! That's what I was going to do. I was going to make an 8 GHz survey with that telescope.
Sullivan
This describes the feasibility of it. And I thought your conclusion was that there were some problems in doing it.
Westerhout
Yes, quite. That was in '59.
Sullivan
This may have been an internal report.
Westerhout
Ok, that's what you may have seen. I cut my stay at NRAO short and at the end of that period, I wrote an internal report. I rediscovered the fact that the sky at 3 cm radiates. That was a rather interesting thing. I concluded that, given the large bandwidth of the travelling wave tube receiver that they had at that time and so on, I could do it, make a survey. Of course then I was again interested in a continuum survey, this time at 3 cm with a much higher resolution, looking at really the thermal radiation only. I mean it was all beautifully completely workable. In fact I'd still like to do it sometime. But the one snag that neither I nor any of the people at NRAO realized was radiation of the sky, the variable radiation of the sky.
Sullivan
From the atmosphere?
Westerhout
Yes. That could indeed be as serious as it was. And this was very funny because this receiver was provided by Ewen-Knight and we blamed the thing on the receiver. So John Campbell from Ewen-Knight would come over and spend days trying to fix the instabilities on the receiver. Then it would go nice and smooth for a little while and then everything would go all over the scale again. The recorder had a full scale 2° or something like that. And I made quite a number - I spent a number of nights making scans across the Galaxy and in the end found out what it was by going through the old MIT series, war-time.
Sullivan
The Radiation Lab?
Westerhout
The Radiation Lab series. And calculating all the various then effects and I then wrote an internal report and left.
Sullivan
I guess they must have known this at NRL?
Westerhout
Yes.
Sullivan
But it just wasn't known at NRAO.
Westerhout
None of the people at NRAO. Neither did I.
Sullivan
You said that George Field was the first user? I didn't know that he had done any observational radio astronomy.
Westerhout
Yes. What was he doing there at 3 cm? I’m trying to think what he was going there at 3 cm. No, he wasn't doing anything at 3 cm. They had a 21 cm receiver and he was trying to look for intergalactic hydrogen.
Sullivan
Oh, yes, there is a paper...
Westerhout
He was trying to look for intergalactic hydrogen.
Sullivan
Was he at Berkeley then?
Westerhout
No, he was at that time, I think, Princeton. He was at Harvard before then.
Sullivan
He got his degree at Harvard?
Westerhout
I think he did.
Sullivan
I see, so he's gone full circle now.
Westerhout
That was a very nice time there at NRAO because everything was rather primitive- although they had beautiful equipment, things worked sort of primitively. And me with my enthusiasm, well, I always wanted things better and more automated. For example, Bill Meredith still remembers, he was one of the telescope operators at that time. And, of course, Fred Crews could tell you that story, too, about my digital recording mechanism. There was in the corner one of the Hewlett-Packard printers which printed out numbers, just intensities, nothing else. So I decided that I wanted positions on there as well. And there was no proper way to get positions on that. The only way I could see to get positions on there was every degree to move the paper one step. That wasn't possible either. The only way you could move the paper was pulling this little handle. So I made a string running all the way across the ceiling to the operator’s table and every time he passed a degree he pulled the string and the paper went one thing further.
Sullivan
This sounds familiar. It sounds like the set-up that you had for your occultation.
Westerhout
Yes, right. I think I was referring to that earlier when I was talking about the occultation. Beeswax and...
Sullivan
Sealing wax and...
Westerhout
No, string and beeswax or something...
Sullivan
String and sealing wax.
Westerhout
What is sealing wax?
Sullivan
To seal something.
Westerhout
Oh, that sort of sealing wax- not with a C.
Sullivan
So that was the situation at NRAO?
Westerhout
Right.
Sullivan
Who else did you visit?
Westerhout
Well, I started out at Ann Arbor and in essence the whole trip was more or less just inspecting, looking around, seeing what everybody was doing. I started out in Ann Arbor and I went to Columbus, Ohio and saw...
Sullivan
Well, hold it. Can you just tell me very briefly just what was going on? At Ann Arbor did they have the 85 foot?
Westerhout
Yes - no. The 85 foot was just being finished. It was slightly behind the one at NRAO. And they had their 20 foot or whatever it was, and they were doing solar patrol and that was about it.
Sullivan
That was [Fred T.] Haddock?
Westerhout
That was Haddock and Howard was there at the time.
Sullivan
And then Ohio State?
Westerhout
Then I went to Ohio State and saw [John D.] Kraus' helical array with 96 helices- that was a neat instrument. And I went to Toronto where I saw [William H.] McCrae who had some horn antenna set up to do an absolute flux measurement experiment. And then I went to Harvard where, of course, I saw - Bok at that time was already in Australia and had been for quite a while- Tommy [Thomas] Gold was there in charge of the place.
Sullivan
He was in charge of the Agassiz station?
Westerhout
Of the Agassiz station but about to go to Cornell and trying hard to convince me to take it over. So I saw the Agassiz station set-up and I was very unimpressed by the general ineptitude of everybody. I had the feeling that they got absolutely nowhere. They had all sorts of equipment, but they weren't doing much. I mean, as compared to what they were doing in Holland. I found Harvard passé.
Sullivan
It's funny though, a number of good people did come out of that, but yet the work they did at that time I have to agree with you is not very interesting and in fact a couple of the things are just plain wrong, of course.
Westerhout
But yet a number of good people came out of it, so you never can tell. And of course I visited NRL quite extensively.
Sullivan
What was your impression there?
Westerhout
I was very impressed with NRL. There was an enormous amount going on, I mean all the way to the very high frequencies. I was sort of disgusted, and I told them so, that they didn't make more use of their big dish.
Sullivan
Which one, the 84 foot?
Westerhout
No.
Sullivan
The 50 foot?
Westerhout
The one on the roof.
Sullivan
Yes, by then it was switching over to radar.
Westerhout
Yes. And I absolutely flabbergasted Ed [Edward F.] McClain, who was then head of the section, by asking him when the 600 foot telescope was going to be ready. And he went, "What 600 foot telescope?" I said, "The 600 foot telescope that you're all building in West Virginia." Then he finally had to come up and he says, "How do you know?"
Sullivan
Was it supposed to be secret?
Westerhout
Yes! At that time it was highly classified. But we all knew about it in Holland somehow or another.
Sullivan
This was '58, wasn't it?
Westerhout
'59.
Sullivan
Oh, yes, very early.
Westerhout
We all knew about it in Holland.
Sullivan
This was before any of the real troubles began with it?
Westerhout
Yes, quite. So I got absolutely nothing out of him, obviously, because it was a classified subject. But I can still see him absolutely reeling back after this Dutchman tells him... for all you know he may have thought I was a spy from the CIA or something.
Sullivan
That why they made you have an escort around the Laboratory, you may remember that. As a foreigner, you had to have an escort?
Westerhout
Oh, yes. Well, that's still so. It's always the case. And so I think I visited NRL twice, I came back from NRAO to visit them once more. I was very- oh, those were the days, too. Here's maybe not an anecdote, but a real historical thing. I don't think you've ever seen it that way. The DTM, Broad Branch Road, Washington N.W.- they had this Würzburg sitting in the back yard and from the Würzburg went a little cable into the Lab and the Lab was in a room next to the Director's office, which was Merle Tuve’s. And the Lab was an absolute mess, wires coming in here, wires strung from here to there, an unbelievable mess. But somewhere in the middle was the recorder with a little table in front of it. And there were recording charts all over. So I came in and I was ushered into Tuve's office and we talked for about five minutes and Tuve said, 'We're wasting our time! Let's take some data while we're talking." So we open this door in his Lab and he switched on the recorder and said, "Where shall we point it today?" So we decided to point it - I wanted to see the famous ? = 50°, b=0°: our standard fields, so we pointed it to ?=50°, b=0°. That took quite a bit of doing. And in it came, "Oh, isn't that marvelous, look at those peaks, now let's look at something else." So we looked at something else. And that was a way line profiles were recorded at the DTM. Ah, most remarkable.
Sullivan
I'm sorry, this was the same one that was shown the Queen? The same field? I thought you said 150.
Westerhout
No, ? = 50°.
Sullivan
I thought earlier you had said 150.
Westerhout
No. ? is 50, b is 0. It's in the neighborhood of new longitude 90°. Just a Leiden standard field. It's a rotten field for a standard field. But I don't know how we got to use it. It's one of the classical profiles that goes with three beautiful humps and a little fourth hump at the end. On the one hand I was impressed by the way in which something came out of all the wires. On the other hand I was somewhat amazed that they had such good equipment there and did nothing with it. And I saw the Mills Cross out on River Road. And then I went to NRAO and stayed there for a number of weeks. Let me see, what other places did I visit on the East Coast- I think that was about it. There was Princeton and things like that, but there isn't much to say about those. I went to an AAS [American Astronomical Society] meeting in Rochester. And then I went to Caltech and I spent about two months at Caltech. Instead of spending the two months at NRAO, I then spent the two months at Caltech. I don't quite know what I did except talk with people, did a lot of talking to people. I didn't make any observations as such.
Sullivan
What did they have there then?
Westerhout
They had the new interferometer which was ready.
Sullivan
This was '59?
Westerhout
Yes.
Sullivan
Ok, it had just started.
Westerhout
Yeah, it was just starting up. That of course was a very exciting time. Everything was humming and buzzing with interest.
Sullivan
What about the optical astronomers there? Were they sort of aloof from all this radio stuff then?
Westerhout
Yes. I was and I have always been, invariably, even now, whenever I visit Caltech, I am always disgusted at the way the optical astronomers don't really know what's going on. They have no contact with the radio astronomy group even though it's in the same building and everything. It's amazing, absolutely amazing. And that includes Schmidt.
Sullivan
Yes, that's surprising.
Westerhout
Very surprising.
Sullivan
And even with [Jesse] Greenstein having contributed quite a bit to the early theory of radio.
Westerhout
Yes. They were sort of benevolently looking on. It was a good source of money, there was plenty endowed by the Navy or whatever, and I think they didn't see too much in it.
Sullivan
But scientifically it really wasn't.
Westerhout
I've always found that amazing. And that, of course, has been the downfall of Owens Valley, the array that they wanted to build.
Sullivan
Of the optical...
Westerhout
No, the lack of interest of Caltech itself. The radio astronomers were enthusiastic, but the school wasn't interested.
Sullivan
I didn't realize that. You mean for the full array?
Westerhout
Yes, the big one, when there was this competition between the VLA and the Owens Valley array before the Dicke committee. And then there was, of course, the various big dishes as well. I think that was the downfall, the non-interest from the optical astronomers was the downfall of that. The other thing that I'm always blaming them for is that they did not latch on immediately to Ryle's supersynthesis idea. They have all the phase equipment except that they didn't have a phase-stable system, even though a phase-stable system had already been made and proven and was in full operation at Stanford several years before, as developed by [Govind] Swarup- they didn't bother about a phase-stable system. They were working all the time- I'm now talking about '62 when Ryle came out with the supersynthesis thing. They had two dishes and they just had amplitude spacing diagrams and then fitted crude models to it. And they could have within half a year completely wiped out the field. When did they finally have a phase-stable system, starting doing aperture synthesis ... Oh, I don't know.
Sullivan
'65.
Westerhout
No, much later, '68. Long after Ryle had come out with all the beautiful maps.
Sullivan
Yes, you're right.
Westerhout
That really I would say sets.
Sullivan
Well, Kurt Weiler’s stuff I think was amongst the earliest of it- the Crab and all.
Westerhout
Yes. That I think really set radio astronomy in the United States back quite a bit. The fact that people in general did not catch on to new ideas, they stuck to their own old ways.
Sullivan
Well, do you have some other examples of that?
Westerhout
...(no answer)
Sullivan
Of course there's the whole fact that it wasn't developed at all after the War, whereas in England and Australia and in Holland it was.
Westerhout
Yes, but it got an enormous kick in the pants in the late 50s. Yet, somehow or another it didn't develop and the main reason there is that there was no astronomer interest. The only astronomer who was interested in a way was Bok and he left.
Sullivan
But that wasn't really what made it go. Well, in Holland, you have Oort, of course, but in England it certainly wasn't classical astronomer interest that made...
Westerhout
No, it wasn't classical astronomer interest. The people who were doing it were physicists who were interested in getting results. They were technicians.
Sullivan
You mean interest from the scientists rather than engineers?
Westerhout
Yes engineers, right. Sorry, I didn't mean to use the word technicians- engineers, right. It was engineers in almost every place. And those in collaboration with the astronomers could have done a lot, but somehow or another the astronomers never got to it. Dicke's hole in the ground is a funny example of that. I mean Swenson is a marvelous engineer. A hole in the ground was built, it had its struggles but somehow or another [George C.] McVitte wasn't the man to run it. And when support folded- no, not when support folded- he felt that the Navy had given him an assignment and it is little to do with the University, and he never got any University people involved. So eventually the thing fizzled out.
Sullivan
Did you visit Stanford?
Westerhout
Yes, I visited Stanford. I visited Berkeley.
Sullivan
What was going on?
Westerhout
Of course, I visited Berkely but I’m trying to figure out what was going on at Berkeley. I didn't go to Hat Creek because Hat Creek didn't exist yet. They were building Hat Creek. At Stanford, of course, there was Bracewell's beautiful solar cross which was going full tilt. That was a marvelous piece of machinery.
Sullivan
Who else was at Stanford besides Bracewell? You said Swarup.
Westerhout
Swarup was at Stanford at the time. There must have been a few more people, but I can't think of any names. [A. Richard] Thompson came later - Thompson was still in England at that time. He didn't come that much later, he came in the early ‘60s, very early ‘60s.
Sullivan
What about - I guess that covers the U.S.
Westerhout
Yes. I went to Australia and, of course, I was very impressed by CSIRO. This was when they were just beginning to lay - sticking for the first spades in the ground for Parkes. Everybody was still at CSIRO - am I right? '59.
Sullivan
Yes, they didn't start leaving until about 1960-61.
Westerhout
But you could feel the friction already at that stage. I mean they were in completely separate groups who would hardly talk to each other. But the thing that impressed me most at CSIRO was the unbelievable support staff. I mean the huge workshops. That's what made CSIRO what it is, that they have this enormous amount of manpower and availability of workshop time. I mean Paul Wild's machine, his circle, every single antenna was built in the workshop. Nothing was contracted out. The same with [Wilbur Norman "Chris"] Christiansen's array, which is still in use.
Sullivan
This was true in the late ‘50s also?
Westerhout
Oh yes, they had an enormous workshop.
Sullivan
Were most of the early antennas all- the early dishes all built...
Westerhout
All homemade.
Sullivan
I didn't realize that. So where else did you go? I guess all that's left is England and maybe France.
Westerhout
England and France I went to... oh, there's another section. I think this covers this particular trip around the world. There's another section after that and somewhat before that where you may be interested in hearing some of my comments and that is the Benelux Cross. This is an entirely different subject. You might write the number where we start on the Benelux Cross.
I was involved in that, of course, from the very beginning, which I think was '57 when Charles Seeger suggested a million dipoles in the form of a cross at 400 megacycles. I sincerely think that that man was an idealist and when he had an ideal and was enthusiastic for something he would not stop talking about it, and come up with more ideas and more suggestions and more things you could do with it. And he kept talking to Oort. And I think he talked Oort into it. I think the fact that there is Westerbork now is initially due to the enthusiasm of Seeger for building something really big. He would never bring it off, but he would certainly initiate the thoughts. The million dipoles of course already shows how completely unrealistic it was. But the idea of having something going, something big. And then Oort somehow or another got on of course to making it the Benelux project. Maybe it wasn't Oort, maybe it was [J. H.] Bannier and Z.W.O. [Netherlands Organization for the Advancement of Pure Research] who thought that might be a good trick. Of course it then became quite a design study of cylindrical paraboloids. At that point Bologna froze it because they at that point had money and built cylindrical paraboloids, more or less precisely to Leiden design.
Sullivan
Yes, Christiansen went down there and advised them for a few months.
Westerhout
That was still for 400 MHz and that was many kilometers long. I still remember making a picture of it on a map of Leiden to show how big it was. It was hanging on the wall for a long time there in the Sterrenwacht. And then it finally became 125 25 meter dishes in the form of a cross. And that was the point where we said now we're almost there. That was the most we were seriously negotiating with the Belgians about who was going to get what and where it was going. And I was then in charge of the site survey. And boy did I travel around. And the funny thing is that people kept saying, later on in particular, people always said, "Well, of course, it had to be built on the border of Holland and Belgium because it was a Benelux instrument." That was not the original reason at all. It so turned out that that was among all the various regions concerned, one of the thinnest populated regions. All border regions in general are thinly populated because the towns are either off in that direction or off in that direction with only one or two main roads in between.
Sullivan
Why are the towns that way?
Westerhout
People don't cross borders! Right?
Sullivan
So you can't have a town right...
Westerhout
So you can't have a town right on one side of the border. So the border area in general in many areas sets the towns rather far removed from each other. And no main roads. Little roads that gradually grow bigger as they get closer to the towns. But the roads are littlest right around the border areas. So looking at the maps and population general densities and industries and so on, those general areas between Holland and Belgium were extremely useful. Other areas that were useful were, of course, up north and the Zuiderzee.
Sullivan
You mean the polder land?
Westerhout
Yeah the polder land. We went and made a big expedition there with the heads of the Zuiderzee Werken and designed the thing right along a dike. In fact, we could still have had the dikes slightly changed before it was actually dredged out had we made the decision within the next three months then or so. They were still at the position where they could have arranged things according to our pleasure. And engineers went into studies of how stable the stuff would be, how fast it would sag, and it turned out that it was remarkably little after the initial settling of the soil. You did not have to worry too much about the telescope sort of slowly but surely sagging as the soil settled further. After the initial year where everything more or less settled and the water has been pumped out, very little more happens.
Sullivan
So your recommendation turned out to have political advantages, but that wasn't the reason...
Westerhout
That wasn't the reason, no. We drove back and forth around that border with special- usually accompanied by special customs officers or something like that. Because at the same time, we didn't want to give it too much fanfare.
Sullivan
Yes, publicity.
Westerhout
Publicity, at all. And we found a most marvelous site. That was the site in fact we had more or less decided on in the end, when we found out that in the big future plan, European Route E-3 or something like that was going to go right through there. And we still decided for that area because we then figured out that we could shield E-3. I then went to the Dutch Railways. Let me see, why the Dutch Railways? The Dutch Railways were very good at putting up masts and posts and things like that. So I had them calculate how much it would cost to put up concrete or what have you, or metal masts all the way across a railroad track, over such and such a length, and then cover them with wire. In other words put the whole E-3 in a Faraday cage. It was rather expensive- it was a million guilders or a few million guilders or something like that. So that was one possibility. The other possibility, which was very much cheaper which came to about a million guilders, was to make a dike on the appropriate side of that road.
Sullivan
A bank?
Westerhout
Yes. The bank was supposed to be 5 or 6 meters high and then on top of it we going to put a 5 meter metal fence. And believe it or not the calculation showed that that got the radio noise from cars riding on that road down by, I seem to remember 64 dB or something like that. Unbelievable! Just that expediency of going up 10 meters.
Sullivan
This is what they’re going to end up doing for the Cambridge 5 km with the nearby expressway.
Westerhout
Oh, they are? There is an expressway going by there? I didn’t know that.
Sullivan
They're going to have a big mound and a big fence, just this same sort of thing you're describing. That was the compromise.
Westerhout
So I was rather involved in that thing until more or less until the time here. In December of '61 we had this OECD Symposium in Paris, which I'm sure you have the proceedings of. I gave two papers there, one on the site survey and one on the sensitivity limits of an unfilled aperture with all the various quantities involved.
Sullivan
But you never got into interferometry?
Westerhout
No, I personally never got in to interferometry. I wanted to get into line interferometry at NRAO, but somehow or another NRAO decided they wanted to make that an in-house effort. So I never got into that. That was a pity. I certainly would have liked to. And of course I was at that stage already getting too involved in all the various administration problems at Maryland that I could really simply say, well, never mind whether you like it or not, I'm going to do it. What with Heinz there, I think we would have been able to get at it much more quickly than they actually did at NRAO.
Sullivan
Yes, and of course that's still not really figured out.
Westerhout
It’s still not really figured out.
Sullivan
Well, I think that covers an awful lot unless you can think of some other things that you'd like to put on the record. Thank you very much. The ends the interview with Gart Westerhout on 22 November 1973.