Interview with Otto Hachenberg
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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). No release form was obtained by Sullivan for this interview. In preparing Sullivan interviews for Web publication, the NRAO/AUI Archives has made a concerted effort to obtain release forms from interviewees or from their heirs or next of kin. In the case of this interview, we have been unable to find anyone to sign a release. In accordance with our open access policy, we are posting the interview. If you suspect alleged copyright infringement on our site, please email archivist@nrao.edu. Upon request, we will remove material from public view while we address a rights issue. Please contact us if you are able to supply any contact information for Hachenberg's heirs/next of kin.
The original transcription was retyped to digitize in 2017, then reviewed, edited/corrected, and posted to the Web in 2017 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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Begin Tape 17B
Sullivan
This is interviewing Professor Hachenburg on February 22, 1973 at Bonn. What Institute was this in Berlin that you were – or do you go back earlier than that, I don’t know?
Hachenberg
No. I made my studies in astronomy, and during the War I was forced to work on high frequency physics. And so after the War, I had both the high frequency education and also the astronomy education. And we started with observations with astronomical problems in ’54 with the sun. We made measurements of the sun at the solar eclipse.
Sullivan
Who is we? What Institute is this?
Hachenberg
It is the Institute of the Heinrich Hertz Institute of the Germany Academy of Science at Berlin. This is a high frequency institute and you see the development. I went over from the astronomy to the high frequency physics, and after the War I was the Director of a high frequency physics institute.
Sullivan
When you say “high frequency,” do you mean microwave work?
Hachenberg
Microwave work and also in this institute we worked on ionospheric problems in propagation of waves and on microwave physics. And so we began to measure the sun in the high frequency physics range. At first, we had an 8 meter dish and made measurements at 20 cm, then we went down to 10 cm and to 3 cm and in a later step to 1.2 cm, a little bit below the water vapor line in the atmosphere.
Sullivan
Now this was in ’54?
Hachenberg
It was in the range between ’54 to ’57. And we made also in that time, ’54, expedition for a solar eclipse to Sweden and North Germany. That was the beginning.
Sullivan
There was nothing before ’54?
Hachenberg
It was forbidden to do anything from us in this -
Sullivan
I see, until when was that?
Hachenberg
In ’54 it was still forbidden to work at 21 cm. But the Institute was situated on the Russian side, and they gave little bits of permission. They said nothing to do something like this, especially their astronomical problems, not other problems and so on, and so we get not an official permission but nobody –
Sullivan
Nobody would stop you?
Hachenberg
Yes. That was the situation.
Sullivan
I was told that in West Germany military regulations stopped in 1950 or so, but they went longer in East Germany.
Hachenberg
Yes. The next step for us was that we build a dish of 36 meters, but it was only a dish (?) And with this dish we made some measurements on galactic radio astronomy of the galactic structure.
Sullivan
When was that built?
Hachenberg
This dish was built between ’57 and ’58. It was a little bit later than the construction of the Stockert telescope in West Germany.
Sullivan
How short a wavelength could you operate?
Hachenberg
The dish could operate to 10 cm and with the inner part at 3 cm.
Sullivan
And this was this located where?
Hachenberg
South of Berlin not far from the town, about 20 km south of the center. But this instrument had no good development. I left East Berlin in July ’61. During that time we made the development of parametric amplifiers but the development was not finished when I went away. And after my going away, the radio astronomy in East Berlin went down. They had problems to develop, to work on science with industrial respects. So the radio astronomy stopped and later on it went a little bit downhill.
Sullivan
Is that still the situation in East Germany?
Hachenberg
Yes, it is still the situation there. You have no great activity in radio astronomy. They make some measurements on solar physics but not more.
Sullivan
Now you mentioned that there was a little bit of work done with this antenna before you left on galactic, what was that?
Hachenberg
Yes. We made a survey of the galactic plane at 408MHz. It is published by Richter, a student, he made his Doctor Arbeit, it means thesis.
Sullivan
Where was that published? What journal?
Hachenberg
It was published in the Academy of Science at Berlin, I don’t exactly know. I think it is one of the series of the Academy. In ’61 I went to Bonn here, and at that time I began to start my activities at Bonn in ’62, July. So I am nearly 10 years now here at Bonn. When I came here -
Sullivan
Excuse me, I still have a question.
End Tape 17B
Click start to listen to the audio for tape 18A of the 1973 interview.
Sullivan
This is continuing with Professor Hachenburg at Bonn on 22nd February ’73. You said that you did 1 cm solar work in ’57 or so.
Hachenberg
Yes.
Sullivan
And I’m just wondering, there weren’t many people working at such a high frequency. In fact, were there anybody that was working?
Hachenberg
I believe we were the first, which worked in this high frequency range on the sun.
Sullivan
NRL was doing a little bit, but I don’t, I think that was actually a little bit later, the Naval Research Laboratories. And why did you – how did you know the techniques? Was this from your war-time background?
Hachenberg
I have 10 years’ work in high frequency physics. We developed the receiver in our Institute here. We had no help from other side.
Sullivan
And one other question before we get to Bonn. I’ve been told there was a man, now I’ve forgotten his name, Professor Priester gave me his name and I have it written down, you probably know, who worked on radar for Telefunken during the War, and they actually did some radio astronomical measurements because it was background noise and so forth. Do you know anything about this?
Hachenberg
Yes, I know the person but I know not exactly the measurements. Excuse me, I’ve forgotten the name.
Sullivan
Well, I have it right here – Franz.
Hachenberg
Franz, yes. Professor Franz is retired. After the War he was in engaged with computer building at Telefunken. For a long time he had developed the TR4.
Sullivan
Oh yes, we had one of those in Groningen.
Hachenberg
He was one of the first persons who worked on this system.
Sullivan
And then also he said Professor Brandt worked on it, but he died a couple of years ago.
Hachenberg
Yes, but Brandt has made no measurements. I know Professor Brandt and he was later on Secretary of State in Nordrhein Westfalen a very high position. During the War here he was engaged with radar organization, not so direct with radar development. And he was Assistant Director of the Director from Telefunken. And from this position, he had, of course, a very good insight in all the physical developments which were done during this time. And he was, of course, very interested in this development but he was not in the laboratory, was not working in laboratory.
Sullivan
Do you think that Franz would be the best person to talk to, to try and find out what radio astronomy they learned?
Hachenberg
Yes, they made measurements of the noise which came out from outside, but I believe they have never published this.
Sullivan
No, I don’t think so. That’s why I’m interested because as you probably know the work of Southworth in America and of Hey in England is well known during the War.
Hachenberg
Yes.
Sullivan
But I’m interested to know what was going on the other side. For instance, did the Germans measure the radiation from the sun and did they think it was English radar jamming because the English thought it was German jamming when they saw it?
Hachenberg
In that other case, Franz had measured the radiation of the galactic planes. He knew that there was radiation coming in from outside but he made no exact measurements. After the War he had also not the possibility to publish it and so it just died.
Sullivan
But you don’t know if he measured anything from the sun?
Hachenberg
I believe not.
Sullivan
Well, I’ll have to contact him.
Hachenberg
Perhaps it is of interest that we made another expedition, a larger solar eclipse expedition, and at that time, in 1960, we used first a large interferometer, a type of instrument which, since that time, was never built. We had a beam with 8 dishes which was moveable so that we could follow the sun.
Sullivan
Which eclipse was this?
Hachenberg
‘60.
Sullivan
And where was it?
Hachenberg
In Bulgaria.
Sullivan
And you had 8 small dishes - ?
Hachenberg
Eight small dishes like the Christiansen system, but we could move this dish. It was 16 meters long and so we had the (?) of the sun, and that’s the beam of the instrument (sound of drawing on chalkboard). During the eclipse we could measure the exact emission of the limb brightness. And at that time the limb brightness was one of the great problems so we intended to make measurements in this way. But we had no advance because in both sides there were active regions, and we got, of course, exact determination of the heights of the active regions, but we found only small limb brightening.
Sullivan
You needed a quiet sun, in other words. Not an active.
Hachenberg
Yes.
Sullivan
Was this work published?
Hachenberg
Yes, that’s published in the Zeitschrift fur Astrophysik.
Sullivan
Yes, that’s interesting. How big was each dish?
Hachenberg
One meter and fifty.
Sullivan
That was still quite a bit of equipment to haul to Bulgaria, I guess?
Hachenberg
Yes, (laughter) but later on, then I left East Berlin, there was nobody to use this instrument. Or, I think they used it to make measurements of the radiation propagation in the atmosphere. They had a very strong transmitter behind the horizon, and then they illuminated the horizon and they tried to determine the scatter of the waves in the atmosphere from a transmitter behind the horizon. They used this instrument in this.
Sullivan
Another question I’d like to ask specifically, was there other radio astronomy in East Germany before ’61, before you left?
Hachenberg
Yes. There was another group in radio astronomy at the Astrophysical Observatory in Potsdam that was Dr. Daene.
Sullivan
How do you spell that?
Hachenberg
Dr. Daene. D-A-E-N-E. (writing on chalkboard) He made all the measurements on the sun, but in the meter wave range. We were specialized on the centimeter, and on the millimeter microwave region.
Sullivan
And he had an array I suppose, a Yagi array or something?
Hachenberg
Yes, Yagi arrays, and interferometers of those two dishes, and so on.
Sullivan
And what period of time was he operating?
Hachenberg
Also in the time from ’57 to ’60. And he works, this small group exists still in Potsdam.
Sullivan
I see. And was this work published anywhere that Daene was doing?
Hachenberg
Oh, yes. They published -
(Interruption)
Hachenberg
That’s the name of the Institute. The Deutches Akademie Wissenschaft, “Investigations on Type III – Type V Bursts.” (pages turning)
Sullivan
I see. There are actually some articles in English also. – Oh, this is ’65, well after you left.
Hachenberg
Yes.
Sullivan
But his early work in the late ‘50s, was that also in this - ?
Hachenberg
These are the measurements during the Geophysical Year, IGY.
(Looking through papers at this moment)
Hachenberg
All these publications, Daene, that’s a man from Prague, and Kruger, Proto Flares and Their Relation to Other Events in the 11 Year Cycle (translating)
Sullivan
And these are – well you can say the German better. Could you just –
Hachenberg
Wissenschaften – Communications, Scientific Communications, of the Heinrich-Hertz-Institut.
Sullivan
I see. And Hartz is the correct way to pronounce it in German?
Hachenberg
Hertz.
Sullivan
That’s useful, I didn’t know about these. And I suppose that during the IGY there were many observatories that were monitoring the sun?
Hachenberg
Yes.
Sullivan
So that in general, the Proceedings of the IGY, well not the proceedings of it, but the summary of it might be a good place to find out what was going on at that time. Ok, that’s a good source.
Hachenberg
There’s also “Research on the Solar Radio Bursts in Centimeter and Decimeter.”
(More shuffling of papers)
Hachenberg
Oh that’s perhaps interesting. I only published in this type of reprint. “The Thermal Radiation of the Water and also of the Atmosphere at 1.2 cm Wavelengths.”
Sullivan
What year is this?
Hachenberg
1955. That’s the polarization – we had the small telescope above a water surface and you could measure the polarization angles known from the optics, but we could measure it at the same time at 1 cm. That’s the two parallel and anti-parallel.
Sullivan
Right.
Hachenberg
And with this instrument, there’s the radiation against (?) the thermal radiation of the atmosphere.
Sullivan
I’m quite interested in that water vapor line because that’s what I did my thesis on, the galactic radiation. You know, the maser emission that’s been discovered from the 1.3 cm line.
Hachenberg
At that time we made also measurements of the thermal radiation of the ground, and also of the human body at 3 cm.
Sullivan
I see. How did you do that? You just put somebody in front of a horn?
Hachenberg
We had a horn nearly 2 meters in diameter, not a dish, and normally you could not see the radiation of the human body because it also has 300 K temperature and it is not too differentiated against the ground. But we put an aluminum sheet so that we have reflected the cold sky into the dish, and then if a person bent before this cooled cold radiation the thermal radiation of the sky you could see.
Sullivan
That’s interesting.
Hachenberg
At that time it was a little bit the situation to search for radar, to make a radar or a picture of the ground without radar radiation. Only with the thermal. And, of course, you could see the water surface if you look from above on the ground the water vapors or of buildings and also especially buildings with sheet roofs. It was very nice to see from above the thermal radiation, the differences in the thermal radiation of the ground.
Sullivan
Was this 1 cm wavelength developed by the Germans during the War already? With that high a frequency? Or was that afterwards?
Hachenberg
It was afterwards. During the War, we only had developments until 3 cm, not below 3 cm.
Sullivan
Another question that’s related is, I’m familiar with the American MIT Radiation Lab and all this where they set up these different bands, k-band, x-band, l-band, all this sort of thing, so I know something about that. But was the German radar development, was it sort of a parallel development, would you say?
Hachenberg
Yes, yes, it was completely parallel. That was one of the interesting points during the War. I was on the scientific side, not on the military side. And it was interesting to see that the development went nearly parallel in two systems which are completely different, and we had no connection with one another. And the development was nearly the same, so that I had moments to believe that the technical development had no great variation. They have things which are developed in another way, and small things there, but within 10 years the development goes nearly on the same way if the systems are completely separated.
Sullivan
As long as you have some reasonably good people on both sides.
Hachenberg
Yes.
Sullivan
Was there an equivalent to the MIT Radiation Laboratory in Germany?
Hachenberg
No. We had only developments in the industry. But in industry, we had very good laboratories, at Telefunken and also Siemens at that time. And the institutes could not follow the very quick development which was done in industry.
Sullivan
I guess it must have been interesting for you after the War to read the MIT Radiation Lab books.
Hachenberg
Yes! That was one of the first (speaks in German) “This series we must have.”
Sullivan
Ok, back to Bonn. You said you came to Bonn in ’61.
Hachenberg
I left Berlin in ’61 and then I had one year without a position. I was a scientist without an exact position. And then in ’62, I came to Bonn. At that time, we had at Bonn, the Stockert telescope which was a very good telescope, a 25 meter dish. From there I started on the development of a larger instrument in about ’64.
Sullivan
So the beginnings of the 100 meter are in ’64?
Hachenberg
About ’64, yes. But at that time I first made firstly some studies in the Institute and also some studies of the scientific way which goes the astronomy or radio astronomy in the following years. At that time we had the arrays from Christiansen and also the array from Mills. And it was the question of what we had to do then. And a little bit of influence by the development in the Netherlands which made from Westerbork. In the Netherlands, you made such a large array. We had the consideration that besides a large array it is also necessary to have a large instrument. At that time the problems were the extragalactic objects and we intended to have the spectrum at high frequencies of these objects. That was one of the reasons in the beginning. And then when we made our first design studies then came also the spectroscopy more and more and it was to see that the spectroscopy has a very much importance in the centimeter wave-range and so perhaps still in ’64 we had a plan to make a large dish which is good for centimeter wave-range. And so the development began. First, we get the money, or not the money, the first sum for design studies in January 1965. At that time then we started with design studies with three firms, it was one group, the other firm was MAN and we discussed with the (?) That was the group which during the War made the radar dish.
Sullivan
I see, the Wurzburg?
Hachenberg
The Wurzburg (?) constructed and fabricated in Friedrichshafen.
Sullivan
Is that the name of the town?
Hachenberg
Yes, a small town on the Bodensee south of Germany near Switzerland.
Sullivan
Can I just ask a question about the Wurzburg dishes because they were so important for development of radio astronomy in Sweden, England, Holland and in America. But did you use them at all in East Germany?
Hachenberg
No. All these -
Sullivan
By the time you could work they were all outdated, I guess?
Hachenberg
Yes. All the dishes were destroyed from the (?)
Sullivan
Or taken away?
Hachenberg
Yes. And so we had no dish. Not in East Berlin, and also not in Western Germany.
Sullivan
Now the standard sort of – is it 3 meter Wurzburg dish – is that the standard size?
Hachenberg
It was the standard size. Three meters and then the next size was 7.5 meters.
Sullivan
But that was not as good as a surface, I suppose?
Hachenberg
No, the surfaces were good for 20 cm, perhaps for 10 cm, but not better. And the surface was not adjustable.
Sullivan
I’m wondering now, for instance, the Dutch did their famous hydrogen survery with a 3 meter, wasn’t it?
Hachenberg
No, no. With a 7 meter dish.
Sullivan
Oh, that was the largest that was made by the Wurzburg.
Hachenberg
Yes. But I must repeat there that the development of this large dish that’s one of the works of Leo Brandt. He did not make the construction but he was forced to do these things in this way. And that was my advantage. When I came to Bonn, Professor Brandt had a very high position in the government in Nordrhein, Westfalen, and so I had a good start to do something.
Sullivan
Good contacts, yes.
Hachenberg
He was very helpful, also, for the development at Bonn of the 100 meter dish. We began with a 60 meter. At that time Parkes was just -
Sullivan
Right, ’63 or ’64 it started.
Hachenberg
And we began to have a dish similar like Parkes. So our first (?) we had (?) directed to a 65 meter dish just like Parkes, but with a better surface. And the price at that time for such a dish was 8,000,000 Marks, very inexpensive.
Sullivan
A pretty good buy.
Hachenberg
But at that time, it was nearly impossible for us to get the sum. Then from this we developed the 80 meter dish and then a 90 meter dish and then a 100 meter dish.
Sullivan
And that’s finally where it is.
Hachenberg
Yes. The 100 meter dish we could do this. We get the money from the Volkswagen Foundation. And so we had 28,000,000 Marks from this foundation and so I could use it for the largest dish, the largest possible dish was a 100 meter dish. But in the development during that time we had a deficit of money from about 6,000,000 Marks. But we get then from the Nordrhein Westfalen 2,000,000 Marks, and from the Ministry for Research and Education 4,000,000 Marks. And so we overcome the difficulties.
Sullivan
What sort of research was going on with the Stockert antenna in the early 60s?
Hachenberg
In the early 60s, we had first – we developed a parametric amplifier for 21 cm for line measurements and then we developed a parametric amplifier. No, we buy it, a second parametric amplifier for 10 cm and we made some measurements with a cooled amplifier at 65 with the Stockert telescope. We made measurements on sources and also of special parts of the galactic plane.
Sullivan
In 1965?
Hachenberg
Yes. There we were one of the first institutes which had a cooled parametric amplifier on the telescope working. At that time different institutes began with cooled parametric amplifiers but we were the first one which had such cooled amplifier on the telescope. Because the Stockert was a little bit – it was easy to use a parametric amplifier. That was one of my first activities at Bonn. I changed the system into a Cassegrain system. And so I had the array in a cabin which stands still. And so I could use very complicated amplifiers and I could change the amplifier during the operation of the telescope. And that was the great advantage of the Stockert.
Sullivan
And the liquid nitrogen and everything was not so much of a problem?
Hachenberg
Yes.
Sullivan
But exactly what research was done in the early 60s even before this?
Hachenberg
Before this cooled parametric amplifier, we made line measurements at 21 cm lines.
Sullivan
For galactic structure?
Hachenberg
For galactic structure. Also for the physics of galactic clouds and so on – physics of the interstellar hydrogen.
Sullivan
And which people were involved in this?
Hachenberg
Dr. (?), Dr. Grahl, Dr. (?). These three people were here when I came over. Mezger was at that time also here, but he left Bonn 6 or 8 months before I came here.
Sullivan
And he went to?
Hachenberg
He went to industry Siemens and he work there for two or three years, I don’t exactly know. And then he went to Green Bank and from Green Bank he came back to Bonn.
Sullivan
I still have to talk to him. And this work on galactic hydrogen was published in Zeitschrift fur Astrophysik mostly?
Hachenberg
Yes. And also we had such a series in the Nordrhein Westfalia.
(Interruption)
Hachenberg
Perhaps you know him.
Sullivan
I know of him, I don’t know him, no. What is the title of this now?
Hachenberg
Research Reports of the Nordrhein Westfalia, “The Determination of 21-cm Line Emission in Eleven Open Stellar Clusters.”
Sullivan
And some of these were never published other than in here?
Hachenberg
Partly they are also published in the Zeitschrift fur Astrophysik but in abstracts. There are others, but I don’t find them at the moment.
Sullivan
Well, that gives me where to look though when I want to. Well, I think that is all. Thank you very much. That ends the interview with Professor Hachenburg in Bonn on 22 February 1973. After the interview, we tried to get ahold of Professor Franz, who still works at Telefunken in Ulm. See the notes in the book on page 6. Because he worked on German radar during the War and was a friend of Hachenberg’s. We called him up, but he was out of town for a couple of days. But he would be a good person to interview on the phone or in person or maybe next time I go to Bonn.
End Tape 18A