Interview with George W. Swenson

Sullivan 00:00

Okay. This is talking with George Swenson on 24 March, '75 at the AES meeting in Bloomington. So, you say your first involvement with radio science in the ionosphere and so forth was in Alaska, actually?

Swenson 00:16

Yeah, I guess that's right. I went to the University of Alaska, and I was in the Physics Department and teaching the electrical engineering curriculum single-handed. And Gordon Little came from Jodrell Bank to do some ionospheric research at college. And I helped him develop some instrumentation for studying the scintillation of radio sources.

Sullivan 00:43

Right, and when was this now?

Swenson 00:44

And that was in the winter and spring of the academic year '53, '54.

Sullivan 00:52

So, it had been well-established that the scintillation of radio sources was ionospheric?

Swenson 00:55

That's right, in fact, at Jodrell Bank. And Gordon came from that school. Well, I guessed he'd worked with Alan Maxwell and had done his thesis in this general area and so on. So, they had set up a program at college. And I, being the only electrical engineer around, sort of got involved in that as a summer activity. And, also, I did a lot of electronic consulting for the Geophysical Institute through the year. And then I came back for the next couple of summers and worked on their program. In fact, I took over the design of the IGY ionospheric opacity measurement equipment.

Sullivan 01:47

Yeah, I see. What sort of frequencies?

Swenson 01:49

That was a 30 MHz. During the IGY, they wanted to set up a network of rheometers around the world, especially through US-controlled territory. And Gordon Little was charged with developing the standard IGY rheometer, I think. Now, one of my claims to fame is that I invented the word rheometer. That summer of 1956, in fact, I was in charge of the work on the rheometer in Gordon Little's absence, and I had to have a word to call it. They didn't have a word yet. In fact, we developed a whole vocabulary of the rheometer, but only the word itself stuck.

Sullivan 02:39

And how is it that you got more into radio astronomy as opposed to ionospheric?

Swenson 02:43

Well, for years I've been looking for some way of applying my electronic expertise in some study of the Universe outside the laboratory. And I would have been happy as a geophysicist of some kind. When I went back to the states, I went to Michigan State. And there I read in some of the electrical engineering periodicals about Bernie Burke and Ken Franklin's discovery of Jupiter decametric radiation. And I thought that was fascinating. I wrote to Bernie Burke, asking him how he ever achieved such a narrow beam width and never realizing that it would have taken an enormous antenna. And the abstract I read didn't say anything about it. They never answered me. But I ran into him at an URSI meeting one time. Got acquainted with him. And then after I left-- I guess that was probably-- yeah, that was after I left Michigan State. Well, I know a little bit about radio astronomy from my contacts with Gordon Little and my work on the scintillation project and I'd read more, and had gone over to Pontiac, Michigan, to talk with Helen Dodson Prince, Helen Dodson at that time, who was interested in radio astronomy in a sort of peripheral way. And I wanted to see if there was in some way I could get into radio astronomy through some collaboration with the people of Michigan. That never worked out.

Sullivan 04:25

So, they didn't have the 85 foot yet, did they?

Swenson 04:27

I don't think they did. No, they didn't. I'm sure that would have been 1965, about '55--[crosstalk] and ‘56. But then I went down to Chicago for a committee meeting. One time I ran into a fellow from Illinois and he told me that they were trying to recruit electrical engineering faculty and why didn't I come down to a Urbana with him? We were grumbling about the situation at Michigan State, which he was vaguely familiar with because he saw an opportunity to recruit somebody. So, I went down there and the head of Electrical Engineering, hearing that I had had a little experience with radio astronomy, introduced me to George McVittie of the Astronomy Department. The upshot was that I negotiated a joint appointment in the two departments which I've held ever since.

Sullivan 05:18

And this is when?

Swenson 05:20

Well, I joined them in 1956.

Sullivan 05:24

Why was McVittie interested in the radio astronomer?

Swenson 05:26

Well, he's a cosmologist and he was interested in the logN-logS kind of relationship, and he wanted to participate in an observational way. And he and Stan Wyatt had been talking about building a radio telescope but didn't know enough electronics to do it themselves. They've negotiated with some physicists at Illinois, but that didn't pan out. And Matt had formed a friendship with Ed Jordan of Electrical Engineering, who, in fact Matt, had urged Ed Jordan to go to a meeting, I guess it must have been in about '54, '55, '54, probably in Washington.

Sullivan 06:11

Oh, yes, I know that meeting.

Swenson 06:13

At which the development of radio astronomy in US was being discussed. And Matt couldn't go, and Jordan, the head of EE, went instead. They decided between them that they were going to have a radio astronomy program and they just been keeping their eye open for somebody.

Sullivan 06:30

So, when you got there, what were your plans to do--?

Swenson 06:32

Well, I was told to learn radio astronomy, first of all, and there wasn't any way you could study it in books or anything at the time. So, Matt negotiated with Joe Pawsey, at CSIRO in Australia that I should go down and spend [?] time down there. So, in the spring of '57, I went down to Australia and spent six or eight weeks with Bernie Mills and Joe Pawsey and Wilbur Christiansen.  That was a wonderful eye-opening experience because they're among the cream of the crop.

Sullivan 07:13

Right. Well, was it that easy in six weeks to sort of catch on to almost all the tricks if you really do electronics?

Swenson 07:23

Well, I think so. I got a rough idea of what I needed to do. And first, I was already a fairly well seasoned antenna engineer.

Sullivan 07:33

That's what I mean. The applications to radio astronomy wasn't difficult to understand and want someone to show--

Swenson 07:40

There were some of the subtleties that didn't dawn on me for years, I'm sure. But at least that first trip around the world I actually did conceive of and rough out the design of the 400 ft telescope we ultimately built in Illinois. In fact, I got the idea for it at the Observatoire de Haute Provence in France talking with Laffineur. And I realized that his idea could be developed in a much more business-like way and actually could amount to a good system for doing a deep sky catalog. And that notion was sort of firmed up on the rest of my trip around the world.

Sullivan 08:33

This was all in '57 now you're talking about?

Swenson 08:35

Yeah, in the spring of '57.

Sullivan 08:36

What was his idea?

Swenson 08:37

Well, he had built these two chicken-wire parabolic cylinders in Haute Provence and was trying to do a sky survey. But it never materialized, apparently. So, then I went to Jodrell Bank and talked extensively with Hanbury Brown. And he agreed that this looks like a promising scheme for a deep sky survey, a good way to build a really big telescope. I wanted to do something a little bit novel. At the same time-- because otherwise, it wouldn't have interested me as an electrical engineer. At the same time, I wanted a useful enough instrument so I could do other things besides simply discrete short surveys. So, I didn't really want to build an interferometer like Ryles. But I--

Sullivan 09:36

Or a Mills Cross, yeah.

Swenson 09:37

And I didn't want to build a Mills Cross because that had been done. I guess if you really probe my motives, that had been done. Also, I thought this would be a better instrument for a wider variety of uses. And I also wanted to do the survey at a different frequency from the Mills Cross, you see. I visualized that we had to go deeper into the sky than the Mills Cross was doing. I mean, there were confusion limited at a certain flux density and so was the Cambridge system. Of course, the Cambridge people, and Mills as well had other ideas that they were cooking, but which they didn't advertise to me at the time. But I learned a lot from all of those people.

Sullivan 10:27

Now, how did you think you were going to get over the confusion problem?

Swenson 10:31

Well, I was going to go to a higher frequency. Pawsey and I planned this out quite carefully. Pawsey was a remarkable guy. There was very little chauvinism to him. He was very much interested in our program and making a success of it, and he helped me enormously. And he sort of pointed the way to the analysis of the confusion problem. And, in fact, I did an analysis of the confusion problem while I was there in his lab in Australia, and decided that a filled aperture dish, about 400 ft in diameter, operating at about 600 MHz would be the right thing to do to go down to one flux unit, which is where we thought we had to go for the next step.

Sullivan 11:19

This was while the Ryle versus Mills Cross is raging full force?

Swenson 11:22

Yes. Yes. I wasn't really very much aware of it. I knew the two people had some controversial attitudes towards each other. But I was really more interested in the technicalities of it all. And I only became interested in the personalities and the conflicts and so on as I got to know them better in later years. So, after that trip around the world, I came back to the States, and I thought a lot more about different things to do, different kinds of interferometry and different kinds of single dish systems and so on. And finally, I decided to build this parabolic cylinder and we interested the Office of Naval Research. My trip, my original trip, and my original studies were sponsored by the University. But then once we got a proposal together, the ONR picked it up. I get the feeling that it was not difficult to get money from ONR at that time. It seems ONR, in fact, was trying to spread their money around to a number of different institutions and they had negotiated with McVittie to set up a project. I think the initial [inaudible] I'm not sure that they did. I'm not sure that they did. But at any rate, did they have an early meeting of the minds between McVittie and Arnold Shostak, who was sort of the fairy godmother of radio astronomy in the United States at that time.

Sullivan 12:59

In what sense did [crosstalk]--?

Swenson 13:00

I mean, he was the director of the electronics program in ONR.

Sullivan 13:04

I see.

Swenson 13:05

And he was very sympathetic to radio astronomy and nurtured it and funded it, of course, you'll see, with the blessing of his superiors, Ronald Robertson and others in the--

Sullivan 13:18

Do you know where he is now?

Swenson 13:20

Yeah, Ronald Robertson?

Sullivan 13:21

No, I mean, Shostak?

Swenson 13:22

Shostak is retired.

Sullivan 13:24

And do you know where he lives?

Swenson 13:25

In Washington somewhere.

Sullivan 13:27

Maybe try to talk to him?

Swenson 13:29

Oh, yes. Arnold would be a marvelous-- I think he's got a teaching position at one of the small colleges around Washington. Maybe on a part-time basis. I'm not sure.

Sullivan 13:44

Arnold, do you remember his middle initial, or--?

Swenson 13:46

Don't think he has one.

Sullivan 13:48

Okay. S-H-O-S-T-A-K.

Swenson 13:50

That's right. Yeah. Now, if you can get him to talk about business, he can give you an enormous amount of information. He's a very astute confined person, but he has this sort of frivolous exterior that you got to get under and he'll tell you jokes until you're blue in the face. But he's a great guy and when you talk to him, give him my regards.

Sullivan 14:19

Okay.

Swenson 14:20

His son is a radio astronomer.

Sullivan 14:22

Oh, I see. Seth Shostak is his son?

Swenson 14:24

Yeah. Actually, Seth is working for the Pennsylvania [?] now.

Sullivan 14:27

But I do know Seth. Yeah, that's interesting.

Swenson 14:30

So, you could perhaps locate him through Seth if necessary.

Sullivan 14:34

Right. Okay. So, you got the money from ONR And when did you actually begin building this dish?

Swenson 14:41

Well, let's see, we started building a 400 ft I suppose about the fall of 1968 from maybe '58. Maybe, I think the fall of '58 we started moving dirt, and then we had to suspend everything during the winter and start it again in the summer of ‘59. And I guess we got our first observation probably the fall of 1960 or some time like that. And then immediately shut the whole thing down to redo the electronics, which were not satisfactory the first time around, although we got our first publication out of it before.

Sullivan 15:31

The first publication was what?

Swenson 15:32

Was a map of Cygnus X. The Cygnus X region at 600 MHz.

Sullivan 15:38

In ApJ?

Swenson 15:41

Probably AJ. Yeah.

Sullivan 15:43

And what was unsatisfactory about the electronics?

Swenson 15:46

Well, I wasn't sensitive enough. We missed the mark conceptually on the design of the transmission line system. These were electronic technicalities that we didn't do right the first time. We had to do it over again. That took us quite a little while.

Sullivan 16:07

Need too much loss in the cables basically.

Swenson 16:09

We tried to match all the cables to the transmission line. We later found that it was much more practical if we tolerated a large mismatch between the antennas and the traveling wave transmission line. This is all discussed. Our final system is all discussed in detail. And a paper in the 1960 PGAP Transactions. There's a radio astronomy issue.

Sullivan 16:47

Oh, yes, a special issue in Radio Astronomy '64, I think it was.

Swenson 16:51

Oh, no, it was earlier than that. There were two papers describing our-- maybe it was '62. There were two papers describing the whole system. Three, actually. There was one in the transactions on military electronics.

Sullivan 17:11

Oh, that's the one I'm thinking of.

Swenson 17:12

That paper was by McVittie, and that described the cosmological considerations. And there was a paper in PGAP, which I believe was probably 1960, something like that. I'm pretty sure in 1960 because there was a special issue on radio astronomy of the proceedings was '58. And then I think the next one was two years later, and that was in PGAP. And Y.T. Low and I wrote a paper on the theory of the antenna. And then about two years later, something like that. So, say 1962 or '63, there was a paper in Radio Science by K.S. Yang and me describing the electronic system.

Sullivan 18:22

Okay, I'll check those out. Did you have any particular troubles with the dish itself? Was that pretty straight?

Swenson 18:29

Not initially. The contractors did a good job of making the dish as we had designed it, and it was very smooth and very good condition when we began. I remember Hanbury Brown came and looked at it and says, "Oh, you can easily use this at 21 cm." So, it was a very large dish.

Sullivan 18:50

And this was the only one of this design--

Swenson 18:53

Anywhere near that size, it was the largest single dish paraboloid in the world for a long time. I guess it still is. Well, no, it isn't now. This big thing that [inaudible] would probably have that.

Sullivan 19:12

Okay, so you redid the electronics, and then the only observations you did with the old electronics was a map of the Cygnus X region. So, you only did that one product with the original receiver?

Swenson 19:28

Well, we did a lot of things with it. We mapped as much as the sky as we had time to for discrete sources, even with the old receiver. Wait a minute. Yeah, I'm sorry. I interpreted the receiver to mean the antenna. No, we didn't change the receiver. We just changed the transmission line. That was a rather tricky problem, as you'll see if you read through that stuff.

Sullivan 20:05

Okay, so then once you got that fixed up, then what was the program?

Swenson 20:08

We just started surveying the sky. Now, my original notion was that this telescope could be made a very fast and versatile instrument, because we could have put a multiple feed system into it very easily. In other words, simply by adding more receivers, we could have put more beams on the sky very easily. And I was having in mind to do that. Now, that's what Mills have done with his regional Mills Cross and also with his second Mills Cross, but I never was able to scrounge up the funds to buy those other receivers and all the rest of the transmission line arrangements and so on. So, we always struggle along with one beam, which made it a very slow project. And it also meant that other people better funded were able to get ahead of us in the mapping.

Sullivan 21:00

The RO survey went over many, many years then.

Swenson 21:03

It did. We operated the telescope for 10 years, and we were surveying for much of that time. And we've published a series of sections of catalog which you may be familiar with.

Sullivan 21:16

Did you do anything in between, any short little projects?

Swenson 21:20

When we crossed the Galaxy, we recorded the Galactic flux and we made a map of the whole Galaxy which we could see, which I think is still probably the most comprehensive and detailed map at that resolution, at that wavelength. And I think it ought to have some usage. That's all in the literature. But it didn't really seem to be turned into a general-purpose instrument like you were originally talking about.

Sullivan 21:49

No, in that sense, it didn't.