[Rydbeck, 1975]
O.E.H. Rydbeck, 1975 (NRAO/AUI Archives, Sullivan Papers)



NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Interview with Olof E. H. Rydbeck
By phone from Groningen to Onsala, Sweden
15 September 1978
Interview time: 60 minutes
Originally transcribed by Pamela M. Jernegan (1979), retyped to digitize by Candice Waller (2016)

Note: 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.

Click start to listen to the audio for tape 116A of the 1978 interview.

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 í78. 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 Masterís degree in electrical engineering. And then after that, the Masterís 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 Ė Spring 1937.

Sullivan

Was this experimental work or theoretical?

Rydbeck

Both. And while at Harvard Ė I was there until late 1940 Ė I developed a lot of equipment for that subsequently indirectly led to LORAN.

Sullivan

I see.

Rydbeck

I developed whatís 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 Ė 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 Janskyís or Reberís observations?

Rydbeck

Iíll 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 donít recall that, no.

Sullivan

They did some associations between optical meteor showers.

Rydbeck

I wasnít 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 weíll come to that later.

Rydbeck

So then I became interested in Janskyís work and early 1940 a mesh parabaloid was installed Ė not so far, I believe, I recall near the present Agassiz station on telephone poles.

Sullivan

How large an antenna?

Rydbeck

I donít recall Ė I guess 15 metersí 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 Ė which I always forgot Ė 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 donít remember the details; I shouldnít know since I wasnít 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 Ė it was a hole in the ground sort of antenna?

Rydbeck

No, it was a wire mesh, supported by, Iíd guess, ten telegraph poles.

Sullivan

I see. And was it -

Rydbeck

And I donít 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 donít remember, you know. I guess several colleges were interested in this.

Sullivan

I see.

Rydbeck

But I donít remember the name of this fellow now, unfortunately.

Sullivan

Do you think thereís a chance that he might be alive? Was he relatively young then?

Rydbeck

Yes, about my age Ė 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, itís 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 Janskyís work and read his papers about cosmic studies.

Sullivan

I see. Did youÖ do you remember if Janskyís work was discussed very much at Harvard?

Rydbeck

Well, no, not very much because most astronomers didnít attach any significance to it, which surprised me.

Sullivan

Do you have any reason why they might have Ė why that might have happened?

Rydbeck

Well, they didnít think it, they didnít realize that radio emission from the galaxy was important Ė thatís what I remember from Ď34-í35, I mean from Ď37-Ď38.

Sullivan

Yes.

Rydbeck

I donít think any optical astronomers really understood, at that time, the significance of Janskyís work.

Sullivan

Right. Right.

Rydbeck

Anyway, when I came back home I started ionospheric research facility near Ė 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 Ė 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 thatís 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 Ė 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 Ė 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

Thatís 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 donít remember quite correctly, I made no notes about it you see, I found that the interference level was too high Ė 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 couldnít compete with Ryleís 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 donít 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 wasnít 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 donít 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 didnít know about the attempts, but I had read a note Ė I guess by Shklovsky.

Sullivan

Oh yes, thatís 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 Ė the one from natural sciences -

Sullivan

Yes.

Rydbeck

- turned down (?) upon the recommendation (?) an interesting case and turned down my application Ė because it was refereed by, I guess by an optical astronomer who said, ďItís (?) also, it could emit radio waves,Ē but that he didnít attach any particular significance to it.

Sullivan

I see.

Rydbeck

Because he didnít 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, thatís in my laboratory files in Gothenburg, or maybe I could find it from (?) or Stockholm. I donít know.

Sullivan

Thereís no rush Ė 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 Ė I didnít 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 donít remember. I probably heard that the Dutch group Ė 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, thatís 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

Thatís 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

Thatís 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 couldnít buy components, and so forth.

Rydbeck

Well, we used what we had, and that slowed down the whole thing. I donít 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 Shklovskyís 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, weíll come back to the telescope because I built the 26.8-meter telescope; thatís 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 Iím not asking about that time. There was some work going on then?

Rydbeck

Yes.

Sullivan

Did they publish any papers?

Rydbeck

Yes, I donít remember when the first papers were published, you see, because I didnít, there was some from the early observations at the (?) station south of Gothenberg, before we got the Onsala property. That appeared in a Masterís 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 masterís theses and not published in journals.

Rydbeck

No, it wasnít 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 wasnít 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 weíre still using essentially the same type of equipment to this Lund University ó

Sullivan

Right. When I visited Onsala five years ago, I still saw this Würzburg, with the Yagi antenna Ė is that still being used?

Rydbeck

Thatís still being used.

Sullivan

Amazing. Letís 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. Letís go back to the early 1950ís. 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 donít know when that was finished Ė I donít 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., youíll 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 Ė 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 Ė 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

Click start to listen to the audio for tape 116B of the 1978 interview.

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

Thatís 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 Townesí 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 Ė 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 wasnít detected you see.

Sullivan

The ammonia line in the laboratory or in the sky?

Rydbeck

Yes, in the laboratory Ė 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, itís very difficult to build because the spiral structure is so small.

Sullivan

Yes.

Rydbeck

You get a terrific partition noise because if you donít have a very high quality magnet, many electrons will strike the helix, and youíll 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 Townesí work. And so -

Sullivan

When did you hear about his work?

Rydbeck

Must have been about 1952 something, í53, I donít 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 thatís the reason we started building ruby masers already in 1958-59.

Sullivan

Now youíre -

Rydbeck

We started building masers 20 years ago.

Sullivan

Right. By this time did you still only have the Würtzburg 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, ďYou can never compete with Jodrell Bank, you know.Ē

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

Thatís getting later, of course.

Rydbeck

You canít 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

Iím 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 couldnít 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 didnít 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 Ė could you compete with Jodrell Bank? And people didnít really understand how good and useful the traveling wave masers are and many of the great astronomers, as a matter of fact, didnít 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 Ė 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 Ė 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 thatís 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 didnít -

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 couldnít, and so the answer was a bigger dish.

Sullivan

Right.

Rydbeck

You see, and in between the Science Foundation said, ďWhy couldnít we build a dish (?) Weíll build 12-meter dish?Ē We spent, you know, do you know Hein Hvatum at NRAO, do you know him?

Sullivan

Yes, yes.

Rydbeck

Heís 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 í59 or something, Ď58. 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 didnít 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- Ė 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 Ė 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 canít 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 Ė Hvatum took part in it, I donít 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 donít 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, heís 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 donít know what they think. By the way, Connie Mayer, is he retired?

Sullivan

No, no.

Rydbeck

No, no.

Sullivan

Heís 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, ďJust pump it and it works.Ē

Sullivan

Right.

Rydbeck

ďJust give it enough pump power and its quite stable.Ē 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, itís not a stable arrangement, you know. Actually, I spent several with Charlie Townes.

Sullivan

Right.

Rydbeck

His (?) I donít know what heís doing now, do you?

Sullivan

No. I donít. 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, Iíd been a visiting professor in the States so many time. As a matter of fact, Iím visiting professor a three, well, what do you call it? Three (?) Ė 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, letís 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 Würtzburg 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 Ė That was 1962, I believe.

Rydbeck

With the Würtzburg, the meteor Würtzburg.

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 donít 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, didnít 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 wasnít 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 youíre saying now that in the period of Ď67-68 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

Iíd 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 60ís, 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 Ď68 now.

Rydbeck

Yes, must have been Ď68.

Sullivan

It was discovered in Ď68.

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 Ď70 or something?

Rydbeck

No, that was much earlier.

Sullivan

The excited OH line?

Rydbeck

The excited OH line was Ď69.

Sullivan

Okay, Ď69.

Rydbeck

Yes, we detected excited OH, well the 6 gigahertz excited OH, I detected in (?) 75B, I guess in Ď69. 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, itís always in the back of your mind.

Rydbeck

Well, I became interested in spectral line astronomy through Shklovskyís paper. And then in 1954 there was a conference in Washington which I didnít 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

Thatís right.

Rydbeck

And I realized that the OH and CH had dipoles strong enough to warrant a search for the molecules. I wasnít aware of the OH maser at the time.

Sullivan

Did you know about Al Barrettís 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 Townesí group would have discovered the frequency. Measured the frequency, as far as I recall, Allen Barrett did use, he, they didnít know the frequency well enough. Is that correct?

Sullivan

Yes, thatís 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. Itís perhaps just a coincidence, but itís 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 itís just an accident, actually.

Rydbeck

It is an accident in both cases, I believe.

Sullivan

Well, what I mean, accident, itís not because of your interest in masers in the laboratory that you ended up studying masers in the sky. Thereís 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 Ė 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 itís 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 youíre familiar with cryogenics, when you have coupling loops and whatnot, you see, and we had to, thatís 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 donít 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 Ė 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 Ė 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, thatís 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 didnít have the dish, it was in the building then, wasnít it?

Rydbeck

It was almost finished Ė 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. Itís 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 Ė 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 thatís another interesting story because it was through van Vleckís work on lambda doubling that I became interested in, you see, that when I (?) Iíve seen the dipole moments, maybe it was in Shklovskyís paper the estimated frequencies of OH and CH.

Sullivan

Thatís 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

Thatís right.

Rydbeck

So I heard about the lambda doubling -

Sullivan

Even in the late thirties, youíre saying?

Rydbeck

Yes, in the late thirties, thatís correct. But I didnít 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, wasnít 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 wouldnít say so, I donít 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 didnít, 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

Heís been working with OH ever since, and it took some persuasion Ė I had to persuade him to change from the hydrogen line work to OH, and I donít think he ever regretted that I persuaded him to change to OH.

Sullivan

Right.

Rydbeck

Look, Iíve been for so many years in touch with many astronomers Ė 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 weíve 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


Modified on Wednesday, 25-Jan-2017 16:22:04 EST by Ellen Bouton, Archivist (Questions or feedback)