Interview with Olof E. H. Rydbeck
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The interview listed below was originally transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009). The original transcription was retyped to digitize in 2016, then reviewed, edited/corrected, and posted to the Web in 2016 by Ellen N. Bouton. Places where we are uncertain about what was said are indicated with parentheses and question mark (?).
We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web. Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.
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Originally transcribed by Pamela M. Jernegan (1979), retyped to digitize by Candice Waller (2016).
Begin Tape 116A
Sullivan
This is now talking with Professor O.E.H Rydbeck over the phone from Groningen to Onsala in Sweden on 15 September ’78. Could you start off please by telling me what your training was and how you first came into contact with radio astronomy?
Rydbeck
Hello?
Sullivan
Yes, could you please tell me first what your educational background was and how you first came into contact with radio astronomy?
Rydbeck
My education and background is the following: I studied at the Royal Institute in Stockholm and first got my Master’s degree in electrical engineering. And then after that, the Master’s degree in engineering physics, and I then started some research in Stockholm, 1935-36 on wave propagation. That work came to the knowledge of the ionosphere group at Harvard University. So I then moved to Harvard University late 1936 – Spring 1937.
Sullivan
Was this experimental work or theoretical?
Rydbeck
Both. And while at Harvard – I was there until late 1940 – I developed a lot of equipment for that subsequently indirectly led to LORAN.
Sullivan
I see.
Rydbeck
I developed what’s called oblique incidence recording equipment. You see, I had wide band transmitting equipment at the Cruft Laboratory and had recording receivers in trucks which I drove down to Washington and New York. I had various stations which were synchronized by a relay, because I had no ground wave that could synchronize those stations.
Sullivan
What sort of frequency was this?
Rydbeck
That was from two to about fourteen megahertz.
Sullivan
And which department at Harvard were you associated with?
Rydbeck
Both physics and Cruft Laboratory at Harvard – the Department of Applied Science, Engineering and Applied Science. They are changed names, you know. Part of it is now called Gordon McKay Laboratory.
Sullivan
I see.
Rydbeck
And I subsequently became a Gordon McKay Fellow at Harvard. Those fellowships were later on changed to Gordon McKay Professorships.
Sullivan
Did you, by any chance, hear about Jansky’s or Reber’s observations?
Rydbeck
I’ll come to that in a few minutes. While doing this kind of work, I became interested in radar echoes because I saw so many radar-meteor echoes, you know. This oblique incidence work I recorded meteors many, many, many times.
Sullivan
And was it clear that they were associated with meteors?
Rydbeck
Yes.
Sullivan
How did you know that?
Rydbeck
Well, for various reasons. Because it was, we compared with optic and you could see them, you know.
Sullivan
Yes. Did you know about the work of Schafer and Goodall and Skellett in the early thirties?
Rydbeck
I don’t recall that, no.
Sullivan
They did some associations between optical meteor showers.
Rydbeck
I wasn’t aware of that work at the time.
Sullivan
I see.
Rydbeck
But this kind of meteor work was later on transferred to Sweden and still continues at the Onsala Observatory by a group of scientists from the Lund Observatory.
Sullivan
Right. I guess we’ll come to that later.
Rydbeck
So then I became interested in Jansky’s work and early 1940 a mesh parabaloid was installed – not so far, I believe, I recall near the present Agassiz station on telephone poles.
Sullivan
How large an antenna?
Rydbeck
I don’t recall – I guess 15 meters’ diameter, or something.
Sullivan
Fifteen meters?
Rydbeck
Yes. I guess so. Then the War came on and the laboratory was reorganized, you know. The normal research projects were closed down and so were these this budding radio astronomy efforts also. And when the war was on, I had to return to Sweden because it so happened – which I always forgot – I was a reserve officer in the Swedish Army Signal Corps.
Sullivan
I see.
Rydbeck
My wife and I left Harvard in late 1940 and travelled all the way back along, you know, Norway and Denmark, were occupied at the time, and we travelled along the coast of Greenland up to Bittsburgh and down to Finland north of (?) that now belongs to Russia.
Sullivan
I see. That was in the late 1940?
Rydbeck
Yes. But when I came to Sweden -
Sullivan
Let me just ask though about, you said that you had to stop the project of building the dish and so forth.
Rydbeck
Well, I was only one of the members of the projects.
Sullivan
Right. But the War had not yet begun for the United States.
Rydbeck
No, but apparently, for some reason the electronics division of the, that was founded 1940 was the activities were changed to war projects.
Sullivan
I see.
Rydbeck
I don’t remember the details; I shouldn’t know since I wasn’t an American citizen.
Sullivan
I see. Right.
Rydbeck
Had I remained with Harvard during the War, I would have had to become an American citizen.
Sullivan
I see.
Rydbeck
When I came over here -
Sullivan
Hold it, can I just ask you another question about this beginning that you made on the – it was a hole in the ground sort of antenna?
Rydbeck
No, it was a wire mesh, supported by, I’d guess, ten telegraph poles.
Sullivan
I see. And was it -
Rydbeck
And I don’t remember the man who designed this. He worked for tropospheric propagation at this Blue Hill Observatory near Boston.
Sullivan
At Blue Hill Observatory?
Rydbeck
Yes, the fellow who took the initiative.
Sullivan
Right and is that something associated with Harvard, Blue Hill Observatory?
Rydbeck
No, well, I don’t remember, you know. I guess several colleges were interested in this.
Sullivan
I see.
Rydbeck
But I don’t remember the name of this fellow now, unfortunately.
Sullivan
Do you think there’s a chance that he might be alive? Was he relatively young then?
Rydbeck
Yes, about my age – slightly older. The whole thing was discontinued, you know.
Sullivan
Right, but he was an engineer at this observatory essentially?
Rydbeck
Yes. As far as I recall, he worked for tropospheric propagation and he became interested in radio astronomy I guess for tropospheric wave propagation work.
Sullivan
I see. Did you get a receiver going at this site?
Rydbeck
Oh, no, no there was no receiver going.
Sullivan
What sort of frequencies were you thinking of?
Rydbeck
About 15 megahertz or something.
Sullivan
Fifteen?
Rydbeck
About fifteen.
Sullivan
About the same as Jansky then.
Rydbeck
About fifteen megahertz.
Sullivan
You would have had very low directivity.
Rydbeck
Yes, now this was sort of, this was so early you know. As a matter of fact, it’s difficult to be very (?) equipment, and you know, there was (?) coming in fifty megahertz so -
Sullivan
So it was just a start.
Rydbeck
Just a very simple start. As a matter of fact, I became interested in radio, well, I used to attend lectures or seminars at Harvard College Observatory because they lectured on meteors.
Sullivan
Right.
Rydbeck
So that was one reason why I used to attend those seminars. And as a by-product of this, I came to hear about Jansky’s work and read his papers about cosmic studies.
Sullivan
I see. Did you… do you remember if Jansky’s work was discussed very much at Harvard?
Rydbeck
Well, no, not very much because most astronomers didn’t attach any significance to it, which surprised me.
Sullivan
Do you have any reason why they might have – why that might have happened?
Rydbeck
Well, they didn’t think it, they didn’t realize that radio emission from the galaxy was important – that’s what I remember from ‘34-’35, I mean from ‘37-‘38.
Sullivan
Yes.
Rydbeck
I don’t think any optical astronomers really understood, at that time, the significance of Jansky’s work.
Sullivan
Right. Right.
Rydbeck
Anyway, when I came back home I started ionospheric research facility near – half way between Gothenburg and Onsala.
Sullivan
Yes.
Rydbeck
And founded what is presently known as the Geophysical Observatory in Kiruna.
Sullivan
I see.
Rydbeck
North of the Arctic Circle in Sweden where I had built a panoramic ionospheric recorder.
Sullivan
Now what time are you talking about?
Rydbeck
This was 1946, you see. When I came back, I had to do war work.
Sullivan
Yes.
Rydbeck
(?) and supersonics, sonar work. And as soon as the War was over, we started building the ionospheric observatory.
Sullivan
I see.
Rydbeck
And the Kiruna Observatory where I built and developed a panoramic, ionospheric recorder, Mark II – is still operational, as far as I know.
Sullivan
I see.
Rydbeck
And then we, this is an interesting point, that then we built a radar, an aurora radar you know, with rotating Yagi groups. And while doing this, I saw that by, well, while working with this antenna, I saw that we received solar noises. And we switched to do meteor, and then I saw so many meteor echoes again, so -
Sullivan
What frequency was this now?
Rydbeck
The meteor, that was 33 megahertz, and that’s the frequency we were using today with the radar meteor equipment at Onsala.
Sullivan
I see.
Rydbeck
And while using this, well, I then built a second meteor recorder which I installed at the (?) Propagation Observatory which became the nucleus of the present Onsala and operating this, I saw solar noise bursts coming in.
Sullivan
Now this is after the War?
Rydbeck
Yes, 1950.
Sullivan
Oh, 1950. I see.
Rydbeck
Or 1952. I had heard from Sir Edward Appleton – I knew him quite well. He told me, because we were in close contact, on account of the fact that we both worked in the field of ionosphere, and he told me, he mentioned to me that he had received (?) bursts – a historic case, you know, (?) he with an English radar antenna.
Sullivan
Right, during the War.
Rydbeck
After - yes just about the end of the War.
Sullivan
Well, no, actually, this fellow named Hey in 19 -
Rydbeck
Yes, Hey. He worked with Appleton.
Sullivan
Well -
Rydbeck
Well, after the War anyway, Sir Edward told me about, you know, there was a gigantic sun spot.
Sullivan
That’s right.
Rydbeck
And he told me about the solar noise, and so I became interested in solar noise to begin with. And so then about 1951-52, I don’t remember quite correctly, I made no notes about it you see, I found that the interference level was too high – then at the site south of Gothenburg where there is now a big residential area.
Sullivan
Right.
Rydbeck
So I had to acquire property and build a new observatory; this actually became Onsala. I had to find the space that was electrically quiet. And then we moved Onsala in 1951-52 and I had no good antennas, so we built a solar noise interferometer.
Sullivan
Now was the idea that Onsala would be a combined ionospheric and radio astronomy?
Rydbeck
No, no. Pure radio astronomy.
Sullivan
Just radio astronomy.
Rydbeck
So we built this, the first instrument was an interferometer with two antenna rays, you know. And it worked on 150 megahertz.
Sullivan
Right. Let me ask you, by this time, had there been any publications from your group?
Rydbeck
No. None were forthcoming on account of the fact that we couldn’t compete with Ryle’s big group, you know. We had hardly any money, you know, and it was difficult to get any financial support for radio astronomy in those days. So my next step was to get the bigger antenna, and so I went to Norway, and we bought five, the big Würzburg antenna. I don’t know if you remember that.
Sullivan
Oh yes, I know them well.
Rydbeck
Which they used in Holland, and my idea then, was to use this assembly in Norway. I moved them on barges all the way to Onsala, and had hardly any money at all. I installed one and the idea was to detect the 21cm line.
Sullivan
What year was this when you moved these antennas?
Rydbeck
1949.
Sullivan
Now hold it, you said that Onsala was begun in 1952.
Rydbeck
No, we got the property in 1949 and because I wasn’t correct in my memory. It was 1949 and in 1950 we started erecting the first Würzburg antenna.
Sullivan
Okay.
Rydbeck
Before, they were not installed before 1952, which I regard as sort of the starting place. But, I applied for money from the Swedish, then a very small Science Foundation, to build a 21cm recorder. It was subsequently built but we came too late. And so, the first work with that recorder was published in the Archives of Physics; my associate, Höglund, did that work.
Sullivan
And what year was that published?
Rydbeck
I don’t remember, 1952-53-54 -
Sullivan
I think I do know that paper.
Rydbeck
You know that was when (?) neutral hydrogen line structure (?) central region of the galaxy.
Sullivan
Right. But let me ask you, you say you wanted to build a 21cm receiver even before the line had been discovered.
Rydbeck
Yes.
Sullivan
Did you know about the attempts at Harvard and in Holland?
Rydbeck
No, I didn’t know about the attempts, but I had read a note – I guess by Shklovsky.
Sullivan
Oh yes, that’s right, in 1948 he wrote a paper.
Rydbeck
So I was familiar with the spin-flip mechanism, but unfortunately, this is a typical and interesting case, the Science Foundation. We have several Science Foundations – the one from natural sciences -
Sullivan
Yes.
Rydbeck
- turned down (?) upon the recommendation (?) an interesting case and turned down my application – because it was refereed by, I guess by an optical astronomer who said, “It’s (?) also, it could emit radio waves,” but that he didn’t attach any particular significance to it.
Sullivan
I see.
Rydbeck
Because he didn’t understand the importance of radio spectrum line emissions whereby you could trace the spiral structure, you know.
Sullivan
Do you think there would be any chance that you could find a copy of that proposal?
Rydbeck
Might be.
Sullivan
That would be very interesting to look at.
Rydbeck
You see, that’s in my laboratory files in Gothenburg, or maybe I could find it from (?) or Stockholm. I don’t know.
Sullivan
There’s no rush – any time in the next few months that you might be able to -
Rydbeck
I was quite disappointed, and that delayed, you see, because I got no grant, I had to build the 21cm receiver – I didn’t have any grant. I had to have graduate students and pick up a little money here and there to get it ready, but that then delayed the whole project and we were too late. But that was one of the, I must have (?) I don’t remember. I probably heard that the Dutch group – because they had a (?) you know. And they were going to use it to detect, look for, the 21cm line. I could easily have heard it at some of the URSI meetings in Europe.
Sullivan
Yes, that’s possible.
Rydbeck
You see, 1950 URSI meeting in Switzerland.
Sullivan
In Zurich, right.
Rydbeck
I could have heard this, but my interest in the line stems from the reading of the paper by Shklovsky.
Sullivan
That’s right and I know that paper. Let me just ask and get the sequence straight. You obtained the Würzburg antennas, and then almost simultaneously you tried to get money for the receiver.
Rydbeck
That’s correct.
Sullivan
And you were not able to.
Rydbeck
No, so we started building the one in the lab, you know, without having any money for the purpose available.
Sullivan
So you couldn’t buy components, and so forth.
Rydbeck
Well, we used what we had, and that slowed down the whole thing. I don’t mean that we would have detected the line, but we could have.
Sullivan
Yes, I know what you mean.
Rydbeck
The Dutch had much more money available for the purpose, you see.
Sullivan
Harvard had still yet more.
Rydbeck
Yes. But that, I became interested in spectral line astronomy really by reading Shklovsky’s paper you know.
Sullivan
Yes, he also talked about the CH emission.
Rydbeck
Yes, and my interest in CH stems from this time. Although it, we’ll come back to the telescope because I built the 26.8-meter telescope; that’s in my application, specifically for the purpose of detecting OH, using masers, you see.
Sullivan
Let me just ask about, there was some meteor radar work being done even in the late 1940s, is that correct? By your group?
Rydbeck
Yes, it still goes on.
Sullivan
But I’m not asking about that time. There was some work going on then?
Rydbeck
Yes.
Sullivan
Did they publish any papers?
Rydbeck
Yes, I don’t remember when the first papers were published, you see, because I didn’t, there was some from the early observations at the (?) station south of Gothenberg, before we got the Onsala property. That appeared in a Master’s of Science thesis from my students. That was very preliminary work, you see.
Sullivan
What were the names of some of these people that were working on meteor radar?
Rydbeck
One of them was Stjenberg; he was one of my early grad students. S-T-J-E-N-B-E-R-G. He then went into industry.
Sullivan
So this was mainly for master’s theses and not published in journals.
Rydbeck
No, it wasn’t published in journals. We improved the techniques; the technique was quite good, you know, the recordings were really very good.
Sullivan
Did you know about the other meteor radar work going on in Canada and in (?)
Rydbeck
Canada I wasn’t aware of, but -
Sullivan
Jodrell Bank.
Rydbeck
About that time, I became aware of meteor work being done by the Jodrell Bank group.
Sullivan
I see. Well, okay.
Rydbeck
Subsequently, quite a number of papers have been published and we’re still using essentially the same type of equipment to this Lund University —
Sullivan
Right. When I visited Onsala five years ago, I still saw this Würzburg, with the Yagi antenna – is that still being used?
Rydbeck
That’s still being used.
Sullivan
Amazing. Let’s go to -
Rydbeck
That group, the meteor group had collected the most; I mean they had been performing statistical studies of radar, meteor records for more than two solar cycles.
Sullivan
Right. Let’s go back to the early 1950’s. After your application was turned down, you say you began to build a receiver at a much slower rate. Can you tell me, then, how that went?
Rydbeck
Well, I don’t know when that was finished – I don’t recall. It must have been 1952, 54-55 perhaps.
Sullivan
Who was working with you on these things at that time?
Rydbeck
Well, the man, Dr. Elldér, still with my group, my chief observer.
Sullivan
What is his name?
Rydbeck
Elldér.
Sullivan
Elldér, yes.
Rydbeck
He has worked with me in OH and CH. Dr. Joel J., you’ll find his name on many of our papers.
Sullivan
Oh, yes, I know his name.
Rydbeck
He worked with me on that receiver.
Sullivan
Right.
Rydbeck
And he did most of the work.
Sullivan
So it was mainly -
Rydbeck
And some other assistants who have now left my laboratory many years ago.
Sullivan
But it was mainly just the two of you.
Rydbeck
Yes, and Elldér did most of the observation work and Höglund did the analysis of the anti-center spectra.
Sullivan
Right. And that, however, was now getting into the mid-1950s, I guess.
Rydbeck
Mid-fifties and then I realized that first of all, I had to get the bigger antenna and what could we do – we had a dish, the Dutch were then contemplating the present Dwingeloo antenna we were talking about the (?) antenna already at the time. So I, you now, what was the use of trying to copy what the Dutch were doing?
Sullivan
Right.
Rydbeck
Then I started building masers in my laboratory. See, my laboratory consisted of two units: you know, the wave propagation, now radio astronomy group – and the research laboratory at (?) in Gothenberg. And we did very early work on travelling wave tubes; long time we built number two travelling wave tube in the world without having seen (?) at Bell laboratories.
Sullivan
I see. What time is this now?
Rydbeck
1946.
Sullivan
In 1946.
Rydbeck
And as a matter of fact, the interaction between the slow wave structure and electron streams -
End Tape 116A
Begin Tape 116B
Sullivan
This is continuing with Rydbeck on the phone on 15 September '78. Okay, could you just repeat that last sentence please?
Rydbeck
This, our work in low noise (?) wave tubes, led me subsequently to (?) wave tube is based on the (?) of interaction between an electron stream, you know, and the slow wave on the spiral structure.
Sullivan
I see.
Rydbeck
And that led me to study the interaction between, with ionospheric whistler modes, in the (?) ionosphere, whistler modes and charged particles that build up the aurora.
Sullivan
That’s very interesting. So your work in the ionosphere was interacting with your work in electronics.
Rydbeck
Yes. And that led, you see, to the traveling wave maser. Even though I was not then aware of Charlie Townes’ work. But my idea was to follow his evidence, you see, because I had the difficulty, you know I built a traveling wave maser for traveling wave tubes, for 20 – which was very high in those days, for 22 gigahertz.
Sullivan
What time are you talking about now?
Rydbeck
1948.
Sullivan
In 1948?! Wow.
Rydbeck
It was because I was then interested in the ammonia line. Even though it wasn’t detected you see.
Sullivan
The ammonia line in the laboratory or in the sky?
Rydbeck
Yes, in the laboratory – we had an ammonia line spectrometer.
Sullivan
Well, it had been studied in the 1930s crudely.
Rydbeck
Yes, I know that. But anyway, what appeared to me during a financial development was to, because, well working at 23 gigahertz, 22-23 gigahertz with that traveling wave tube, it’s very difficult to build because the spiral structure is so small.
Sullivan
Yes.
Rydbeck
You get a terrific partition noise because if you don’t have a very high quality magnet, many electrons will strike the helix, and you’ll get partition noise, so that too, was very noisy.
Sullivan
Right.
Rydbeck
So then it appeared, why not replace the electron stream with the, an ammonia beam or a molecular beam?
Sullivan
I see.
Rydbeck
You see? Which in principle, is the correct thinking.
Sullivan
Right.
Rydbeck
And molecular beam amplifier. Then I heard about Charlie Townes’ work. And so -
Sullivan
When did you hear about his work?
Rydbeck
Must have been about 1952 something, ’53, I don’t remember.
Sullivan
But you had not actually begun construction of such a device?
Rydbeck
No, but as a matter of fact, I filed a patent application. For a molecular amplifier. But then, you see, I became convinced to replace the molecular stream by, to turn it into traveling wave maser using chromium (?)
Sullivan
Yes.
Rydbeck
So that’s the reason we started building ruby masers already in 1958-59.
Sullivan
Now you’re -
Rydbeck
We started building masers 20 years ago.
Sullivan
Right. By this time did you still only have the Würzburg antennas?
Rydbeck
Yes. Now I come back to the next point. You know, when I approached the Science Foundation to get funds to establish the present 25.6-meter telescope, they said, “You can never compete with Jodrell Bank, you know.”
Sullivan
Right, right.
Rydbeck
Their big antennas. I said I will be able to compete with Jodrell Bank with my traveling wave masers.
Sullivan
Right.
Rydbeck
And then I said I would not do any work, as a matter of fact, the first traveling wave masers did was for the hydrogen line, you know. For the 21cm line, we did our first maser work in that telescope on the 21cm line.
Sullivan
On the 26-meter telescope.
Rydbeck
Right. Of course -
Sullivan
That’s getting later, of course.
Rydbeck
You can’t use it to great advantage because the line temperature (?) is so high anyway. I said to the Science Foundation that with my masers, I would be able to compete with Jodrell Bank with an 84ft instrument. It took me several years to sell that idea.
Sullivan
Which years are these, now?
Rydbeck
I’m approaching 1959 now.
Sullivan
So, it took you several years starting in 1959?
Rydbeck
No, it took me several years to get a good response in Stockholm to get the money necessary to build an 84ft telescope.
Sullivan
But when did you finally succeed?
Rydbeck
1960-61. (?) but it was in 1960-61. What I had in mind at that time, this is interesting, was to build a copy of, well I talked to the (?) Company in Holland you know, so what I had in mind was a copy of the Dwingeloo antenna. But then it struck me that that would not be a good antenna for maser work, I would have to have a (?) effect, you know. And have the helium, liquid helium, cooled low noise front end at the apex of the parabaloid.
Sullivan
You wanted to have it much more accessible.
Rydbeck
Yes. And to avoid ground noise.
Sullivan
Right, and also to avoid the background.
Rydbeck
So in order to make use of the (?) more easily to have an instrument cabin which is more easily accessible.
Sullivan
What about the fact that you would probably want to have a more accurate surface so you could operate at higher frequency?
Rydbeck
That came about because my surface is good up to 9 gigahertz.
Sullivan
Right, but were you reasoning at that time that you could use these masers to better advantage at the higher frequencies?
Rydbeck
Yes. But that idea I couldn’t send to the Science Foundation because at that time no, you see, what I tried to sell was the idea to use the masers, my OH traveling wave masers to detect OH. And then I knew I could build masers for X-band, but again, people who refereed my application didn’t believe that there were any, that any interstellar molecules exist -
Sullivan
Right.
Rydbeck
So there was great doubt at that time in a small country like Sweden – could you compete with Jodrell Bank? And people didn’t really understand how good and useful the traveling wave masers are and many of the great astronomers, as a matter of fact, didn’t believe it at all, you know.
Sullivan
No, I can well understand that.
Rydbeck
So the idea was to get the surface and a pointing mechanism so I could work up to 9 gigahertz. And this came about by another effort, namely, to get the additional funds to get the pointing system, gear boxes and so on that would be good enough up to 9 gigahertz, and the surface and the steerable sub-reflector. I had to join hands with the Swedish Telegraph Administration and subsequently with the Telegraph Administration as you know, in Denmark, too. The main idea, was mainly that in order to establish a telesatellite ground station, we had to perform experiments while Telstar was up.
Sullivan
I see.
Rydbeck
That idea being, the other solution would have been to build a micro link down to France and make use of the French station. So the Telegraph Administration, they pitched in and they gave me a lot of money to buy a better surface, and I had my (?) very much like the Millstone dish.
Sullivan
Yes, right.
Rydbeck
But a heavier back-structure – some (?) this is structure number two, there are two in the series and I have this extra surface, you see. And high accuracy, fairly high accuracy surface, several control systems – that was paid for by the three Boards of Telegraph Administration in Sweden, Norway and Denmark. And almost four years of experiments with Telstar and other satellites -
Sullivan
That would be in the early 1960s, now.
Rydbeck
Yes, yes.
Sullivan
What fraction of the time did they have, roughly?
Rydbeck
Two-thirds.
Sullivan
Two-thirds, and what -
Rydbeck
And you know I had, that was a very heavy price to pay.
Sullivan
Yes, what fraction of the total cost of the antenna did they - ?
Rydbeck
Well, not two-thirds. I would say one-fourth or one-third. But that was made a severe condition and so you see, the present control building, which you have seen, was occupied by the Telegraph Administration, and I had my equipment inside the tower. So that’s the reason it went on so slowly.
Sullivan
Right.
Rydbeck
My time plan was to have the maser going in 1963, and then, of course, (?) and others detected the OH line.
Sullivan
But now, let me go back a step before we get to the OH. In the late 1950s, were there continued radio astronomical observations at Onsala?
Rydbeck
A moment please.
Sullivan
I was just wondering, were there radio astronomical observations going on in the late fifties at Onsala?
Rydbeck
Not much. We still have the 150 megahertz interferometer, did a lot of scintillation work.
Sullivan
Ionospheric scintillation?
Rydbeck
Yes, and you see, because we were still control of, at that time, of the Kiruna Observatory operation. So I could say when we saw Cas A and other sources through the auroral (?) we were recording the structure of auroral (?) up north and seeing the scintillation here. A couple of papers were published on scintillation, I think.
Sullivan
But you just didn’t -
Rydbeck
But you see, (?) only had the CH numbers at the hydrogen line radiometer, you know. And with the same type of dish in Holland, the Dutch had done almost everything that could be done at the time.
Sullivan
Right. So you just basically could not compete in radio astronomy in the late fifties?
Rydbeck
We couldn’t, and so the answer was a bigger dish.
Sullivan
Right.
Rydbeck
You see, and in between the Science Foundation said, “Why couldn’t we build a dish (?) We’ll build 12-meter dish?” We spent, you know, do you know Hein Hvatum at NRAO, do you know him?
Sullivan
Yes, yes.
Rydbeck
He’s one of my students.
Sullivan
And he helped in building this dish?
Rydbeck
He built the 12-meter dish, which blew to pieces in the 1969 gale.
Sullivan
I see. When was this built?
Rydbeck
Must have been around ’59 or something, ‘58. And that would have improved the hydrogen line recording, you see, because it was a bigger dish.
Sullivan
And was this ever used?
Rydbeck
Yes, it was used, but no (?) you know, because the field was noisy, too. So a lot of recordings were done, but we didn’t obtain anything that was really a significant improvement over what the Dutch had done.
Sullivan
Right, so everything was hanging on getting the large antenna, right?
Rydbeck
Of course, (?) we did lots of solar noise eclipse work.
Sullivan
Oh, I see, yes, tell me about that.
Rydbeck
Well, I moved the interferometer to Naples, 195- – that was the solar eclipse in Naples.
Sullivan
In 1952, I believe.
Rydbeck
1952. I moved both my panoramic and ionospheric recorder; I still had Version 3 and moved that to Naples, and the 150 megahertz interferometer. But that was an unfortunate experiment in a sense, because it was only partial. I was very doubtful about it, but this was arranged through URSI.
Sullivan
Yes.
Rydbeck
An international cooperation, program of cooperation, but you see, the part of the sun that was eclipsed by the moon had sunspots.
Sullivan
Yes.
Rydbeck
As you may recall, so that made, well that made it very, very difficult, almost impossible to do any – we published a report on it, you know, but that was almost a waste of money.
Sullivan
I see, were there other -
Rydbeck
And there was another eclipse in 1954, was it 1954?
Sullivan
I think so, in Sweden itself.
Rydbeck
Yes, there we did a lot of very important ionospheric work on the recombination (?) ionospheres, at the same time we were recording the sun on 150 megahertz, moving the interferometer to north of Sweden, not so far from the Norwegian border.
Sullivan
And did you get some good astronomical results from that?
Rydbeck
Yes, but you know, nothing that you can’t do with a better interferometer. The 150 megahertz resolution was just not good enough.
Sullivan
Right.
Rydbeck
So that spoiled us again, the type of (?) science project.
Sullivan
Did you know about the -
Rydbeck
The solar noise, we did solar noise work – Hvatum took part in it, I don’t recall where he published it, on I guess, it was 3 gigahertz or something with the 12-meter dish, as far as I recall. Studied limb brightening.
Sullivan
And when was this now?
Rydbeck
I don’t recall; that was published.
Sullivan
And what was his name?
Rydbeck
Hein Hvatum.
Sullivan
Oh, Hvatum, yes, right.
Rydbeck
He was one in the group and we published a paper on the limb brightening, I guess we published a paper on limb brightening.
Sullivan
Okay.
Rydbeck
Deduced from the solar eclipse data, you know.
Sullivan
Right.
Rydbeck
That was one, if you call that radio astronomy, that was one of the things we did.
Sullivan
Did you know about the NRL group that came to Sweden to observe that eclipse?
Rydbeck
Yes, yes.
Sullivan
Did they come and visit your - ?
Rydbeck
Yes, I went with them. I helped them get started at (?) Eastern Sweden, John Hagen.
Sullivan
Oh yes, right.
Rydbeck
I knew John Hagen.
Sullivan
And Connie Mayer was along, I think.
Rydbeck
Yes, I knew Connie Mayer. I remember their equipment very well. And he is very careful, he’s a careful experimenter.
Sullivan
Right.
Rydbeck
And yes, yes.
Sullivan
Were there any profitable exchanges of information on microwave work at that time, since, of course, they were operating at much higher frequencies?
Rydbeck
No, I was the person who gained by looking at their equipment. I went there several times.
Sullivan
I see.
Rydbeck
So I assisted them, in many ways, getting started here. I think so I did; I don’t know what they think. By the way, Connie Mayer, is he retired?
Sullivan
No, no.
Rydbeck
No, no.
Sullivan
He’s still head of radio astronomy branch at NRL.
Rydbeck
When you see him again, give him my best regards.
Sullivan
Okay, will do. As you know, I used to work there.
Rydbeck
I met him many, many times in the past.
Sullivan
Did - You must have followed with interest when Townes brought his maser down to NRL and put it on the 50-ft. in 1958 or so.
Rydbeck
Yes, I was there.
Sullivan
You were there?
Rydbeck
Yes, I took part in one of the recording sessions from one of the planets with Charlie.
Sullivan
I see, was that just by accident?
Rydbeck
No, no. I was interested. I remember that convinced me because of the very, sort of temporary arrangement he had. I remember the (?) thing hanging in the air, you know. And (?) some kind of rope arrangement.
Sullivan
Right.
Rydbeck
And Charlie said, “Just pump it and it works.”
Sullivan
Right.
Rydbeck
“Just give it enough pump power and its quite stable.” That was about, shortly thereafter we started work on (?) so Charlie, when I saw how easily Charlie could work with his one cavity maser, that really convinced me that the laboratory could and should invest money in developing traveling wave masers.
Sullivan
I see.
Rydbeck
I never believed in the cavity maser because basically, it’s not a stable arrangement, you know. Actually, I spent several with Charlie Townes.
Sullivan
Right.
Rydbeck
His (?) I don’t know what he’s doing now, do you?
Sullivan
No. I don’t. At Columbia, right?
Rydbeck
Yes. That was, that planetary experiment was kind of an inspiration to me.
Sullivan
So did you visit America at that time specifically to be an observer, more or less?
Rydbeck
No, I was, you see, I’d been a visiting professor in the States so many time. As a matter of fact, I’m visiting professor a three, well, what do you call it? Three (?) – Penn State and U. Mass.
Sullivan
I see.
Rydbeck
So from my Harvard days, you know, I had so many associates that I used to visit the States every year.
Sullivan
Oh, I see. Okay.
Rydbeck
Lectured from our traveling wave tube work, I used to visit the Quantum Electronics Conference every year; so I kept in close touch with low noise receiver developers in the States throughout the fifties.
Sullivan
Okay. Well, let’s go back to the 26-meter antenna, were there any special problems in building it or did it go pretty smoothly?
Rydbeck
It was directed by my own staff.
Sullivan
Yes.
Rydbeck
And the Kennedy Co. did most of the engineering work; what we did the servo systems, of course, and the sub-reflectors, the three phase sub-reflectors, you know. It was designed in such a fashion because you had no geostationary satellites in those days.
Sullivan
Right.
Rydbeck
I had the wobbling kind of arrangement with the sub-reflector (?) tracking area, you know, and you tracked a satellite and therefore automatically locked the telescope onto the satellite.
Sullivan
Right.
Rydbeck
As a matter of fact, we started tracking deep-space probes with the Würzburg as a test before I could, before we tracked Mariner 4 with the 25.6-meter instrument.
Sullivan
Before you tracked which satellite?
Rydbeck
Mariner 2.
Sullivan
The Mariner 2.
Rydbeck
And then we used the parametric amplifier, the first to my knowledge in Scandinavia, at least; perhaps one of the first in Europe. We built the parametric amplifier; they used about 960 megahertz at the time.
Sullivan
Right.
Rydbeck
And we tracked, NASA had no tracking station in Europe at the time; and we tracked Mariner 2.
Sullivan
I see – That was 1962, I believe.
Rydbeck
With the Würzburg, the meteor Würzburg.
Sullivan
Right.
Rydbeck
So one of the first things we did with the, to test the new telescope was to track Mariner 4. And had a phase, a phase-lock kind of receiver arrangement. We tracked it all the way to Mars.
Sullivan
And this would be what year now?
Rydbeck
I don’t remember.
Sullivan
1963-64, I guess?
Rydbeck
Something of that order. We, in the final recording phase, were using a bandwidth of about one hertz.
Sullivan
I see.
Rydbeck
We got the picture on tape.
Sullivan
Hm. And what was the first radio astronomy you did with the new antenna?
Rydbeck
Must have been around, well, that was with paramps on OH.
Sullivan
Now the line had just been discovered, right?
Rydbeck
Yes, we verified that.
Sullivan
Right.
Rydbeck
And we took even some spectra, not of the quality we have today by any means.
Sullivan
Right.
Rydbeck
OH in (?) B which just yesterday (?) for two hours or something.
Sullivan
I think you had a paper or two in Nature about this, didn’t you?
Rydbeck
No.
Sullivan
No? I must be getting mixed up.
Rydbeck
We, I guess, reported on it at some kind of URSI meetings or something.
Sullivan
Okay.
Rydbeck
And then the Telegraph Administration left the telescope 1964, and my first good masers, OH masers, were ready by 1966-67.
Sullivan
Right.
Rydbeck
(?) the CH maser at the time we had three of four CH masers amplified.
Sullivan
CH masers?
Rydbeck
Yes, because the frequency wasn’t known.
Sullivan
Right.
Rydbeck
As a matter of fact, we are sending a CH maser to Parkes.
Sullivan
Oh really?
Rydbeck
In January.
Sullivan
I see. So you’re saying now that in the period of ‘67-68 you were developing CH masers also?
Rydbeck
Yes, we started to build, we built OH and CH masers at about the same time, but the first CH maser with frequency range was too low and the project (?) maser is still lying in the shop in Gothenburg.
Sullivan
I see.
Rydbeck
One of the things I like to do which I looked at yesterday, I have now more reliable figures on the SIH frequency.
Sullivan
I see.
Rydbeck
I’d say it lies around 2.9 gigahertz, so we may start looking for it within the next year or so.
Sullivan
Right. Well now, going back to the early 60’s, you say you did confirmation of the OH discovery, and you also began a longer-term OH programs. What other kinds of programs were done?
Rydbeck
Formaldehyde, we built a formaldehyde maser.
Sullivan
Now this is getting up to ‘68 now.
Rydbeck
Yes, must have been ‘68.
Sullivan
It was discovered in ‘68.
Rydbeck
Yes, we detected it two weeks later or something. Without really being aware of the American discovery.
Sullivan
I see. Is that true? And also, when you got the large antenna, did you expand the staff at Onsala quite a bit?
Rydbeck
I did. As a matter of fact, the reason, you see, I became interested in excited OH very early. The reason I built the five gigahertz maser which we used to detect formaldehyde was to detect the 5 gigahertz excited OH (?)
Sullivan
Oh yes.
Rydbeck
The maser was built for this double purpose.
Sullivan
Right. I see. That happened in ‘70 or something?
Rydbeck
No, that was much earlier.
Sullivan
The excited OH line?
Rydbeck
The excited OH line was ‘69.
Sullivan
Okay, ‘69.
Rydbeck
Yes, we detected excited OH, well the 6 gigahertz excited OH, I detected in (?) 75B, I guess in ‘69. And with the same maser, detected, actually we were the first to detect, excited OH 6-gigahertz in absorption W3C.
Sullivan
Right. And you say this work on OH and CH all goes back to this original Shklovsky paper?
Rydbeck
In my mind it does.
Sullivan
Right, it’s always in the back of your mind.
Rydbeck
Well, I became interested in spectral line astronomy through Shklovsky’s paper. And then in 1954 there was a conference in Washington which I didn’t attend.
Sullivan
Yes, I know that conference.
Rydbeck
And I got the print from Charlie Townes. Well, he had estimated, as far as I recall, the dipole moments of CH and OH and Shklovsky had done the same thing.
Sullivan
That’s right.
Rydbeck
And I realized that the OH and CH had dipoles strong enough to warrant a search for the molecules. I wasn’t aware of the OH maser at the time.
Sullivan
Did you know about Al Barrett’s unsuccessful search at NRL in the mid-fifties?
Rydbeck
I remember visiting John Hagen, and I guess Barrett had left at that time, or maybe he was around, and I still have that first paper in the blue cover.
Sullivan
The NRL report, you mean?
Rydbeck
Yes. So I was, I guess, I know that it had Charlie Townes’ group would have discovered the frequency. Measured the frequency, as far as I recall, Allen Barrett did use, he, they didn’t know the frequency well enough. Is that correct?
Sullivan
Yes, that’s correct. He was searching over a very wide band.
Rydbeck
Yes, so I know when Charlie Townes had determined the frequencies of the two main lines, I knew that the time was ripe to look for OH with the traveling wave maser.
Sullivan
Something just occurred to me. It’s perhaps just a coincidence, but it’s interesting that both you and Townes worked so much with masers in the laboratory and also got involved with them in the sky. But I think it’s just an accident, actually.
Rydbeck
It is an accident in both cases, I believe.
Sullivan
Well, what I mean, accident, it’s not because of your interest in masers in the laboratory that you ended up studying masers in the sky. There’s really no connection.
Rydbeck
No. You see that the maser in the laboratory is one thing, but to build a maser that could be used in a telescope, a traveling wave maser that could be stable enough mechanically – then I got money from the Science Foundation, I had to convince them it was worth the money to build masers, specially developed masers, for this telescope.
Sullivan
When you were working on masers in the lab in the late fifties, were you quite convinced that they could work on the telescope or - ?
Rydbeck
I was all the time. Not cavity masers, you know, I built ruby cavity masers because (?) (?) which were silver coated and had small wave guide holes in it, you know. But it’s not a stable device, when you increase the gain you decrease the band width.
Sullivan
Right, right.
Rydbeck
So I was convinced that we had to build a ruby maser. I was convinced that the specific gain of ruby so low that you end up with a very long maser, so then we very early, as you may know, turned to (?) (?) in our present, within a few weeks gone to test masers that operate with 32-34 gigahertz for the new telescope. So that has (?) So we left the ruby field very early.
Sullivan
What were the special things you had to do to adapt a lab maser to be a radiometer on the telescope.
Rydbeck
To develop good (?) and reliable couplings and so on, well, that really would be reliable, you know. And that took several years. You know, you have to be, if you’re familiar with cryogenics, when you have coupling loops and whatnot, you see, and we had to, that’s difficult to make properly. And the (?) system, you know.
Sullivan
But basically because the whole thing is moving around to different orientations.
Rydbeck
(?) tilting the maser, and of course, the maser is always tilting to a certain extent. And then, you see, you had to develop servo systems that would keep the helium pressure, the helium temperature, constant. So you could operate the constant gain. In the laboratory you don’t care about it, you know. If the helium boils off or the temperature changes, you measure the gain as a partial temperature, but when you use a maser in a telescope, you must run with constant helium temperatures. There are so many difficult things which have, which we mastered a long time ago.
Sullivan
Things are much more critical, yes.
Rydbeck
But I was convinced all the time.
Sullivan
Well, let me ask a couple more general questions about the fifties – for instance, you went to the Jodrell Bank meeting in 1955, I believe. Do you have any specific memories of that meeting as to any impressions?
Rydbeck
I was in the, the most interesting talks were given by Burbidge and wife.
Sullivan
Burbidge and who?
Rydbeck
Geoffrey Burbidge and his wife.
Sullivan
Oh, his wife, yes.
Rydbeck
Yes, that was one of my great memories.
Sullivan
And this was on what – energetics of radio sources?
Rydbeck
Yes, nuclear synthesis, as far as I recall. But then when I saw, this is not to criticize Jodrell Bank, but when I saw their electronics equipment, then I became convinced because it was at that time a high noise system. That convinced me, that’s interesting because it convinced me that with the masers we would be able to compete with the big Jodrell Bank dishes.
Sullivan
Of course, they didn’t have the dish, it was in the building then, wasn’t it?
Rydbeck
It was almost finished – at least mechanically.
Sullivan
It took another -
Rydbeck
Mechanically because they were testing the servo systems while we were there, you know.
Sullivan
I think it took another two years before they got on the air, actually.
Rydbeck
But I saw the receivers in the electronic shop, and then I was convinced because, you know -
Sullivan
That you could compete, right.
Rydbeck
With masers, right. I was convinced, but after all, with limited resources at the time, it was, it took us several years to build reliable masers. It’s an enormous, an enormous step from having, running traveling wave maser in the laboratory, and running one in the telescope, you know.
Sullivan
Indeed.
Rydbeck
And now we have (?) helium about a week. All that took time to develop.
Sullivan
If someone had asked you in the mid-fifties, what do you do – how would you have described yourself?
Rydbeck
That depends -
Sullivan
What is your profession?
Rydbeck
My profession?
Sullivan
Yes, in the mid-fifties.
Rydbeck
I was, and am, a professor of theoretical electron physics.
Sullivan
Is that what you would have said, or would you have said that you are an electrical engineer or radio physicist?
Rydbeck
Well, no, physicist. Because, you see, at Harvard I studied quantum physics, solid state physics, (?) courses, you know, and that’s another interesting story because it was through van Vleck’s work on lambda doubling that I became interested in, you see, that when I (?) I’ve seen the dipole moments, maybe it was in Shklovsky’s paper the estimated frequencies of OH and CH.
Sullivan
That’s right.
Rydbeck
OH and CH, but then it immediately struck me that that was the theory that lambda doubling that was done by van Vleck.
Sullivan
That’s right.
Rydbeck
So I heard about the lambda doubling -
Sullivan
Even in the late thirties, you’re saying?
Rydbeck
Yes, in the late thirties, that’s correct. But I didn’t attach any significance to it at that time.
Sullivan
Right. What about your relationships with optical astronomers, in Sweden especially, but also in other places? Have you been in contact with them, or has it been, more or less, a separate development of radio astronomy?
Rydbeck
I was in contact especially with the late Professor Lindblad.
Sullivan
With Lindblad, wasn’t it -
Rydbeck
Professor Lindblad, the one who worked in galactic structure.
Sullivan
Right.
Rydbeck
He, within the limited means that he could place at our disposal through the Science Foundation, he supported, he did everything he could to support our work.
Sullivan
I see. So he was the chief astronomer in Sweden, was he not?
Rydbeck
He was at the time, yes.
Sullivan
So you had his support, but you did not have the support of many of the other astronomers, I gather.
Rydbeck
Well, I wouldn’t say so, I don’t think I would be that specific. They were not familiar with the theme, you know.
Sullivan
Right. But they were not -
Rydbeck
But Professor Lindblad never thought that we could discover OH. He thought OH was, would be dissociated, you know.
Sullivan
Was he mainly interested from what you might learn from the hydrogen line?
Rydbeck
Yes, and he was, I would say to put it this way, that he was slightly unhappy when I didn’t, that we did not continue work on the H-line with our first maser.
Sullivan
Right.
Rydbeck
Our first maser, as I told you, was the hydrogen line maser. So we switched, and I said to him, the only we can compete with molecular line OH and CH, I remember, (?) going to stop work on the hydrogen line, yes, I said.
Sullivan
Yes, and this -
Rydbeck
So I switched my men to OH and one of the first I switched was a man by the name of Winberg who works at Bonn.
Sullivan
Oh, yes, I know Anders well.
Rydbeck
He’s been working with OH ever since, and it took some persuasion – I had to persuade him to change from the hydrogen line work to OH, and I don’t think he ever regretted that I persuaded him to change to OH.
Sullivan
Right.
Rydbeck
Look, I’ve been for so many years in touch with many astronomers – Menzel at Harvard, listened to his lectures and we have been in touch for many, many years.
Sullivan
Menzel?
Rydbeck
Yes, right.
Sullivan
Well, that pretty well covers what I wanted to cover. Did you have any other points going up through the early sixties only?
Rydbeck
Not that I can remember, no.
Sullivan
I think we’ve done it pretty thoroughly. Thank you. That ends the interview with Olof Erik Rydbeck over the phone to Onsala on 15 September 78.
End Tape 116B