Interview with John P. Hagen

John P. Hagen, 1908-1990. Interviewed 27 August 1976 at the IAU Meeting in Grenoble, length of interview: 110 minutes.

Papers of Woodruff T. Sullivan III

Contact Archivist for details. See Addresses Needed.

Oral History

Sullivan, Woodruff T., III

Hagen, John P.

Audio cassette tape

110 minutes

1976-08-27

Pre-war and WWII radar work at Naval Research Laboratory; post-war microwave solar work at various eclipses, etc; development of radiative transfer theory for sun in corona and chromosphere; construction and calibration of 50 foot dish; 21cm H I region work; use of radio astronomy to Navy; Director of Project Vanguard; Naval Research Laboratory's microwave pre-eminence, 1963+ at Penn State.

The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.

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 Hagen's heirs/next of kin.

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.

Working Files Series

Individuals Unit

Transcribed by Pamela M. Jernegan.

Sullivan

OK, this is talking with John Hagen on 27 August ’76 at Grenoble. So, before we get to radio astronomy per se, can you tell me about your background at NRL [Naval Research Laboratory] before then?

Hagen

All the dates I'm going to give you, of course, are from memory and approximate, but I think I came to NRL in 1935 with the expressed purpose of developing centimeter wave techniques because we were just at that time at NRL beginning to work on radar. The radar in the United States was originated, or invented at NRL.

Sullivan

The [Gregory] Breit and [Merle] Tuve thing, you're referring to?

Hagen

No, no. The Breit and Tuve thing was just an observation, the actual development of the techniques for detecting airplanes was started at NRL under Dr. [Albert Hoyt] Taylor.

Sullivan

Taylor, I see.

Hagen

And it was in that group that I was brought in to see whether centimeter wave technique, which was just then beginning, could be developed to the point where they could be used for radar. So we spent some years on making magnetrons and crystal detectors and things like that to attempt to get centimeter radar going. That continued up to the war, but in 1939 [Sullivan: 1940] the British came over and we had a conference with them on radar techniques. It was quite astounding to see how the radar development in England, which, of course, was a secret development as was the radar development at NRL, how much there was in common.

Sullivan

You didn't know about each other's work?

Hagen

No, not until 1939.

Sullivan

But they were working at lower frequencies, weren't they in general?

Hagen

In general, so was NRL. The main thrust at NRL, at that time, was at 200 megahertz. The British also had their main radar at 40 and somewhat higher frequencies. But the British also developed the Boot magnetron, which was a real breakthrough for centimeter radar.

Sullivan

Right. But you said you came to develop centimeter techniques, but you didn't do too much on that in the first few years?

Hagen

The first few years were spent on doing that - on working on developing receivers and on developing magnetrons.

Sullivan

I'm a little confused. But it hadn't gotten to an operational point like the longer wavelengths?

Hagen

No it hadn't. We had in the centimeter region, we worked with- at that time, because of the power limitations on the transmitters, we worked with CW radar rather than pulse and demonstrated the use of CW radar against ships from the laboratory. And also from at sea from a destroyer escort vessel where the meter radar was first tried out at sea.

Sullivan

I see. About when was this?

Hagen

1938 or thereabouts. This was before the British came over and we started the joint venture. And of course, out of the British trip to the States then the Radiation Laboratory developed under the overall committee, whose name I've now forgotten [Sullivan: NDRC]. And then the principal work on the centimeter radar was done in the Radiation Laboratory where they had so many people.

Sullivan

Now let me just ask, this British delegation was in 1939 and, of course, when England got in the war and was the purpose essentially to see if a combined effort would prove fruitful?

Hagen

Yes. Obviously there’d been a high level decision at that time to cooperate with the British so they came over to find out what we knew and to see whether there could be some joint effort.

Sullivan

And, in fact, during the war, it's been my impression that most of the centimeter radar was built in the States and the British kept to somewhat longer wavelengths.

Hagen

More or less that's true, yes. The British did develop their own centimeter radar, which they had on ships. So you can't really write it off with that generality. You'd have to say the British continued their work on centimeter radar during the war.

Sullivan

Okay. But now, what specifically did you work one during the war?

Hagen

During the war, I worked on several projects. One of them was the development of a radar for use in submarines where you couldn't use conventional antennas, of course. And so we built an antenna that was enclosed in a periscope. That radar was used by the submarines who- they don't like to become exposed. I also worked on countermeasures for centimeter radar during the war. And then, one of the long standing projects, which we had going before the war and carried on through the war, was a device for the automatic navigation of aircraft to get a ground speed indicator using centimeter techniques.

Sullivan

How would you differentiate the effort the Rad [Radiation] Lab versus NRL? Of course, it was much larger at the Rad Lab.

Hagen

Much, much larger at the Rad Lab. At NRL, our main thrust during the war was for radar for the Navy.

Sullivan

Was the Army developing its radar through its own lab somewhere?

Hagen

Yes. The Army was doing their own up at Fort Monmouth. And that was quite a separate effort from what was going on at NRL.

Sullivan

During the war, did you learn about [James] Hey’s accidental discovery of solar emission?

Hagen

Yes. Somewhat late in the war- I've forgotten, of course, time doesn't mean anything it's hard to say- but we were aware of it.

Sullivan

Do you know of any experiments that might have been done in the U.S. radar labs that might never have gotten published but you might have heard about? There was [George] Southworth's thing which I know about but of any others?

Hagen

No, I think those that were done were published. There's work on detecting the Moon and work on atmospheric absorption.

Sullivan

By [Robert] Dicke. That was right at the end of the war. So, given the end of the war, what direction was your own work going to take?

Hagen

At the end of the war, we had a large group of people trained in these centimeter techniques and so we cast about for some useful scientific thing to do and radio astronomy looked like the right thing, and we then organized a group dedicated to radio astronomy. Our first thrust was to work with the solar radiation.

Sullivan

You were reading in Nature about the Australians and the British observations, I assume?

Hagen

Oh, yes. There were not many people involved in that kind of work at that time and everybody knew everybody else.

Sullivan

But was this immediately after the war?

Hagen

Oh yes, yes.

Sullivan

Because the first publication I have that you're involved in in any way is 1948, so that's a three year gap in there somehow.

Hagen

Well, the first thing that we did and published was to observe an eclipse of the Sun, which I think was done in either 1946 or 1947.

Sullivan

Yes, I have it here - May, 1947 eclipse and it was published actually in 1949 as part of a Symposium on Microwave Astronomy which I think the AAS [American Astronomical Society] organized. I'd like to hear about that.

Hagen

It was the results of that work were delivered at an URSI [International Union of Radio Science] meeting a couple of years prior to that time.

Sullivan

But that's still May, 1947. Did it take two years to sort of get things rolling?

Hagen

Oh yes. It takes time to get things rolling, to do the experiments, to write it - it takes a couple of years.

Sullivan

Can you tell me what was required in getting things rolling?

Hagen

What we had to do, of course, was to look about and to determine how much of the equipment that was available as a residue of the war could be used and how much we had to construct. And instead of using radar mounts, which many people did, the group at NRL constructed its own mounts specifically designed for solar observation.

Sullivan

Equatorial, therefore.

Hagen

Equatorial, right. One thing about NRL, which you know since you were there, they have an excellent shop. We felt we would have a much better experimental set-up if we started from scratch.

Sullivan

Okay, that helps to explain right away a couple of years. You weren't slopping together stuff in order to do some measurements. You decided to really build specifically the astronomical.

Hagen

That's right. And at that time, too, we also decided that we would do some work at millimeter wavelengths. So at the same time we were developing this 10 centimeter and 3 centimeter effort in radiometers, we were developing receivers and antennas to be used at millimeter wavelengths.

Sullivan

Right. 8 millimeters was, I guess, the shortest that you went, which, of course, is incredibly short for those days - it's still a short wavelength. But before we get up to that, that was 1949 when you gave a talk at an AAS meeting about that. Could you tell me a little bit more about what you needed to do during those two years after the war to get things rolling? You had to get this dish built...

Hagen

Well, that period, it was a transition period - we had a group of 80 people to begin with when the war ended and out of those, we selected the group that would stay on and work at radio astronomy. And then after that, we had, of course, to organize the laboratory and to get the equipment built and installed on the roof of the lab - all of which takes time. Then, concurrently with that, we were getting equipment ready to build for the eclipse.

Sullivan

But you were working 100% on this. It wasn't a matter of one project versus another.

Hagen

Oh yes. Well, part of my group was working 100% on it.

Sullivan

Now you said radio astronomy group- it wasn't called that at that time, I suspect.

Hagen

I believe it was called "Centimeter Wave Research," if I'm not mistaken [Sullivan: R. F. Research Branch, I believe]. I don’t know when radio astronomy appellation was put on, but it was somewhere around 1950 that it began to be called radio astronomy, but I’m not sure of the date [Sullivan: ~1953-4].

Sullivan

Can I just ask- was this a Branch [Sullivan: NRL organizational branch]?

Hagen

It was a Branch.

Sullivan

What the other groups in the Branch were doing?

Hagen

Some of them were doing things I can't tell you. The group was still working on this ground speed indicator, which used centimeter and millimeter readings. But a good deal of the work was being done by the rest of the group was classified, and unfortunately, I don't always remember what was and what wasn't. So I better just not talk about it.

Sullivan

Okay. Can you tell me who was in the radio astronomy group?

Hagen

Yes. And I hope I don't forget someone.

Sullivan

You can check the transcript and think about it later.

Hagen

[Fred T.] Haddock and [Cornell H.] Mayer, [Russell M.] Sloanaker, McCullough, a fellow named [E.] Sees...

Sullivan

[T.] Decker, I see here.

Hagen

Decker, [M.] Schulkin.

Sullivan

[Edward F.] McClain, was he there?

Hagen

McClain. This was immediately after the war. Now Schulkin was not there immediately after the war; I've forgotten when he came into the group. That was a little bit later, but it was soon after the war. [J. G.] Gibson, McKuen- I think those were the principal people in that group.

Sullivan

Okay, and another question that comes to mind is why was the Navy willing to support this kind of research? What was their interest in it?

Hagen

Well, NRL from the beginning was always interested in promoting basic scientific work. A certain portion of the NRL budget was set aside for basic scientific work, of course, that might possibly at some time benefit the Navy. But there was no pressure to show a direct use.

Sullivan

And this came under that heading?

Hagen

Yes. And we were able to convince them that radio astronomy was just a good effort to get into. Principally because it led to the development of the useful radio techniques that would not otherwise have been that early developed.

Sullivan

Can you name a couple of examples?

Hagen

Well yes, antennas. The whole matter of antennas for use at very short wavelengths really developed out of radio astronomy. The first big antenna that was useful at the centimeter and millimeter wavelengths was that 50 foot dish that we built at NRL. So that what was learned there made it much easier- not only there, but of course, don’t misunderstand me, in other radio installations- made it much easier for the communications satellite people, for example, to get on with their [?]. And then the development of receiver techniques, that's the most important part. In radio astronomy you must deal with the most sensitive and the most stable receivers. And so, the thrust for the development of very stable and very sensitive receivers was in those days pretty nearly all from radio astronomy.

Sullivan

I see, there wasn't really a commercial need for them.

Hagen

No, no commercial need at all.

Sullivan

That has developed since. That's an interesting comment.

Hagen

Another point is in the matter of precise calibration. I mentioned a fellow named Sees in this list of people we worked with. Of course, we understood that we had to have very accurate measurements for flux of sources. And initially, we used essentially thermometers and oven techniques or so-called "hot-loads" to calibrate our receiver. But at about that time, which was in the late ‘40s, the use of discharge tubes was introduced and Sees, I think, made the first precise calibration of a discharge tube. Now those things are used all over. So there again, that's another one of the reasons why it was worth the Navy's while to back radio astronomy.

Sullivan

This is a very interesting list, can you think of any others? I was just wondering if interferometry- of course, NRL didn't get into interferometry until really VLBI in the 1960s, I don't think.

Hagen

No. We had a Michaelson interferometer operating in the laboratory in 1936 at 10 centimeters. We never made great use of it; one of the first things that we did do, and we did that internally and never did publish it, was to measure the dielectric constant of material, some materials that we were interested in.

Sullivan

I see, this is before the war now.

Hagen

Before the war when all this stuff was classified.

Sullivan

I was thinking of radio astronomy.

Hagen

No, in radio astronomy, no. We did not use interferometry at that time.

Sullivan

Which is actually sort of an interesting contrast to virtually every other radio astronomy group in the ‘40s and ‘50s. Was this because you were concentrating on the higher frequencies where resolution wasn't such a problem?

Hagen

Well, two reasons: 1) we were concentrating entirely on the higher frequencies. Until we started work on the hydrogen line, anything lower in frequency than 3,000 megahertz. The other reason why we didn't do interferometry was geographic. Our equipment was all on the roof of the building at NRL and had we gone into interferometry, we would have had to go out and find land somewhere where we could build an interferometer we would have to go out and find land somewhere to build interferometers. There was more of a problem with that than it looked to be worth. And furthermore, at that time, there was not a great push to develop interferometry techniques at centimeter wavelengths.

Sullivan

Why?

Hagen

Well, because the facilities for making very large antenna were not yet with us. It wasn't until 1950 or so that we got the 50 foot dish; and it's only with the very large antennas that you can see the weaker sources where you need the higher resolution.

Sullivan

I see.

Hagen

That statement is not entirely correct. There are some things on the Sun of interferometry techniques would have been useful. And we could have, of course, done that with the antenna that we had available, but we didn't.

Sullivan

Well, one can't do everything. Let's go back to the first experiment that was published anyway, is this the first one you did, in fact? There is a report of a burst in July of 1948 in Physical Review by Schulkin, Haddock, Decker and Mayer, and Hagen, at 9500 megahertz using a 10 foot dish. Was this your first real thing?

Hagen

Possibly that's right, yes.

Sullivan

When you got this system working, what did you do with it? Just monitor the Sun and this burst just happened to come along?

Hagen

That equipment we kept in daily operation so that we were able to amass data on the flux of the Sun and analyze that as a function of the sun spot activity. At that time, of course, not so much was known about the origin of the enhanced solar radiation and this was part of the early work in demonstrating that the excess solar radiation, is a function of, or has a very close relationship to the solar activity as evidenced by sunspots.

Sullivan

Right. Did you know about the work of [Arthur E.] Covington that was going on almost simultaneously with yours?

Hagen

I'm not sure when we first became aware of what Covington was doing. I can't give you the exact date, about that time - somewhere around then.

Sullivan

What about the [Sullivan: AAS] Symposium on Microwave Astronomy - it’s one of the earliest such meetings, I think. Where and when was this held? [Sullivan: New Haven- December 1948]

Hagen

Is this the one that was held under the National Academy [of Sciences]? It was held in Washington?

Sullivan

I'm not sure - a few papers were published in the Astronomical Journal and undoubtedly it says there where and when. That was in ‘49, I'm not sure of the meeting date.

Hagen

There was a separate publication on that thing.

Sullivan

Oh, no, you're thinking of the 1954 meeting that was in JGR [the Journal of Geophysical Research].

Hagen

Was it that late?

Sullivan

Yes, the one where virtually all the U.S. radio astronomers got together.

Hagen

Yes.

Sullivan

Yes, that's 1954. This is one that's in AJ in 1949 - the Symposium on Microwave Astronomy. I think it was part of a AAS meeting.

Hagen

Well, my memory's gone - I don't recall that. I'd have to go back and look at the journal.

Sullivan

And you had a paper on your eclipse, May '47 eclipse.

Hagen

Yeah. I'd have to go back and look that up.

Sullivan

Well, can you tell me about this eclipse?

Hagen

Well, the eclipse was a lot of fun. We had a fairly long series of eclipses that we went to and observed at centimeter and millimeter wavelengths. The principal purpose for the eclipse observations later on was to demonstrate the truth of the existence of limb brightening, but in this first eclipse, we had two- well we didn't have a preconceived notion, we hadn't worked up the theory by that time. We had no real prior knowledge of limb brightening, but we were aware of the need to correlate the excess flux with regions on the Sun. So we went to that eclipse to demonstrate that or to investigate whether the excess radiation was confined to small areas and whether they would be eclipsed. And that, in fact, was demonstrated.

Sullivan

In particular, these short wavelengths - this had been demonstrated in long wavelengths by that time. [Martin] Ryle and the Australians had found that spots were smaller than the Sun in the radio as well.

Hagen

Possibly again, I'd have to check the records. The other thing, of course, that came out of this was an indication that it was limb brightening.

Sullivan

When you say you hadn't worked out the theory, were you aware that, for instance, [David] Martyn had a paper in Nature in which he at several different frequencies showed [Sullivan: predicted] how limb brightening sets in as you go to higher frequency, on his theory anyway. That was ’46.

Hagen

Well, I was aware of Martyn's work, yes.

Sullivan

But that was just the results, he didn't go through the whole theory in the paper in Nature. I'm just wondering if your observations were in response to that same thing.

Hagen

Not specifically in response to that, no. Again, I'm not too clear in my memory about the events at that time and the particular sequence of events that led up to that. We were aware of Martyn's effort. That combined with the work of [Thomas George] Cowling in England really led to the theoretical work that was done by [Jean-François] Denisse and by me. Denisse put his effort mainly on the corona, the other part of the Sun; and I put the emphasis on the chromosphere. But the two things fitted together quite well, and my part of the work, at least, leaned heavily on the work of Cowling and the work of Martyn.

Sullivan

Now, was Cowling using radio data?

Hagen

No, no, no. Cowling was purely theoretical on the theory of the diffusion and the theory of impact, which was the basic part of this [?] radiation.

Sullivan

So he wasn't working on the Sun at all?

Hagen

Oh, no, no.

Sullivan

The name didn't ring a bell. Well that's right, finally you published this in 1951 in ApJ and I think also that this is your Ph.D. thesis at Georgetown, if I remember correctly.

Hagen

That's right, it was.

Sullivan

Did you go take time off to become a student or did you do it all part time?

Hagen

I did it part-time and at night.

Sullivan

This is rather interesting, because this is one of the earliest Ph.Ds in radio astronomy, I think.

Hagen

I'm told it is the earliest.

Sullivan

I'm not sure I can think of a counter example, now that you bring it up.

Hagen

I'd be interested if you could. [Donald H.] Menzel, who was on my committee, thinks that it was the first.

Sullivan

Okay. I just talked to him a couple of days ago, by the way. But what I wanted to ask was that this probably meant that you took a lot of courses in optical astronomy and so forth.

Hagen

Well, you see, I started out in physics and astronomy and then the Depression came along and then the war. The Depression led me to NRL and then I stayed on when the war came on and I had previously done graduate work at Yale, so that I didn't have too much to finish off- the graduate work I did at Yale was in Physics, but I didn't have too much to finish off at Georgetown for a Ph.D.

Sullivan

I see.

Hagen

I had, I did have quite a bit of course work.

Sullivan

When you say astronomy as an undergraduate - you took a number of astronomy courses?

Hagen

Yes, and at that time, my intention was to go into astronomy.

Sullivan

Oh really?

Hagen

Oh, yes, after I got into graduate school, but I really entered graduate school in physics.

Sullivan

This explains a little bit more about why you were eager to latch on to this new radio astronomy.

Hagen

Oh, yes.

Sullivan

It combined two of your real interests.

Hagen

That's right. It got me back on the track.

Sullivan

May I ask what undergraduate school you attended?

Hagen

Boston University. And then I did a Master's at Wesleyan working on the properties of quartz by using radio techniques- looking at the decay of oscillation.

Sullivan

Well, to go back to your thesis work on the theory of the solar radiation and radiative transfer, as it’s called now anyway, and so forth, there was similar work going on by, I think, [Stefan F.] Smerd and so forth, but you probably weren't aware of this at the time - this was all just brand new as you were working on it?

Hagen

It was brand new and what his name- [Joseph L.] Pawsey visited the laboratory at one time just as I was about ready to publish this- not to publish it, to put the thesis into Georgetown, this was before I condensed it for publication. I told him at that time of the contents of the theory and what it led to and subsequent to that time, [John "Jack" Hobart] Piddington down in Australia published a paper, which I think actually was published before my paper, dealing with the same topic, but in much more general ways - he just assumed an exponential decay and pressure, which is easy to do. The Australians were working at that time. Also, Smerd and I forget.

Sullivan

[Kevin C.] Westfold, was it?

Hagen

Westfold and there was another fellow, but Smerd and Westfold in particular had been working in this area, but their interest was in the other part of the Sun’s atmosphere.

Sullivan

Because they lower frequencies, basically?

Hagen

Yes. And they did some very excellent work. The work that they did on synchrotron radiation is still good.

Sullivan

Synchrotron you say? That would not be the quiet corona then?

Hagen

No, no.

Sullivan

You weren't dealing with bursts....

Hagen

No, no, I was dealing with the quiet Sun. And the process that I dealt with specifically was [?] radiation.

Sullivan

Right. I notice, also in 1949, that you gave a AAS talk about the microwave observations of the Sun and what brightness temperatures implied at the various frequencies, going from 6700 to two million and so forth. But the important thing I see here is that you're talking at a AAS meeting - in other words, you're talking with astronomers. Does this come out of the fact that you were a student at Georgetown and really felt being part of the astronomical community as opposed to going to an IRE [the Institute of Radio Engineers] meeting?

Hagen

Yes. The important thing here is that at this period in time radio astronomy was a nasty word in the astronomical community. And...

Sullivan

Why was this?

Hagen

Well, astronomers are, don't quote me on this, they’re a peculiar breed of people - they resist what is new. They weren't ready to accept the fact that radio astronomy was telling them things which they couldn't find out by any other means. This is the American Astronomical Society. This is not true so much in Europe nor was it true so much in Australia. But in the United States, this was true. One well known American astronomer, whose name I won't give you, said one time when some work was being considered here on developing equipment for observation of the hydrogen line...

Sullivan

Being considered where?

Hagen

In the United States, "You don't need to do that, why do it, the Dutch have got it all done." So the point - I'm getting back to your question, is that I felt that what we were doing in radio astronomy was astronomy and therefore it ought to be reported to the American Astronomical Society. That’s why I gave the paper there.

Sullivan

That was really an exception, I think.

Hagen

At that time, yes.

Sullivan

And for quite a while, actually. Or maybe I should be careful.

Hagen

Well, I think it's something that gradually came on; most of the time the people in the AAS didn't know what you were talking about. They just didn't know. But they gradually became more receptive.

Sullivan

What you're saying is that you don't mind so much that they don't know what you're talking about, but that they didn't really care to make the effort either.

Hagen

Yeah. At that time.

Sullivan

Can you tell me a little bit about the model that you worked out for your thesis work? What light it shed as opposed to what was known before?

Hagen

One of the big problems in working with the Sun is that optically you cut off at about a height of about 1-2,000 kilometers. Above that the optical depth is so small that observations are just impossible, and so the principal information about the Sun gained through optical observation at that time cut off at about 1,000 kilometers or so. What I did was to take the everybody's radio observations, not only my own, and put them together to show the variation in flux or in effective temperature of the Sun as a function of frequency and then set about using the [?] radiation process as the efficient radiation process to put together an atmosphere that would predict the observed flux as a function of wavelength. And it was questionable in the beginning whether this has any uniqueness to it, but I think by testing the model, I satisfied myself that it is unique. There are not a hundred different ways you can put an atmosphere together and still satisfy the criteria you set up. This also explains our great interest in eclipses. The eclipse measurement gives you a means of establishing height and once you put that measurement in, then the whole question of uniqueness is set to rest. You know that if your heights are right then everything else is okay. So the outcome of this was a model of the sun's atmosphere giving temperature as a function of height and electron density as a function of height. And there have been other models since then. I still, up until very recently, used that same model and it worked quite well. I am on the verge of publishing a much more up-to-date version of this which shows a unique feature, but that is not a part of this story. But based on the same assumptions there are much better observations now on flux, at least 20 or 30 years.

Sullivan

Yes, but what you're saying is that after 25 years, this model basically still holds.

Hagen

It still holds except for the lower part of it. There's a problem here - the radio evidence tends to show the temperature of the Sun's atmosphere falls very steeply as you go in the transition region between the corona and the chromosphere. The solar observations from way back when, back in the ‘30's and then again some made in the ‘40's, show that perhaps without question, that the height is not awfully sure- somewhere 2,000-3,000 kilometers above the limb, the temperature has to be on the order of, depending on the person you talked with and the...

Sullivan

So continuing with John Hagen on 27 August ’76. So you're saying the temperature has to be?

Hagen

Somewhere you've got to accommodate these spectroscopic observations that show that there are, fairly deep in the solar atmosphere, temperatures on the order of 20,000°-30,000°. That was not accommodated in this early theory of the Sun's atmosphere that I had and that we were talking about.

Sullivan

Right. Well, let me ask about these eclipse expeditions. First of all, where was that May, 1947 eclipse - the first one?

Hagen

About 20° longitude in the Atlantic.

Sullivan

In the Atlantic, so you went on a Navy ship?

Hagen

We were on a ship.

Sullivan

Oh, I see, can you tell me about that? That's rather interesting.

Hagen

We had a destroyer escort vessel and put a radiometer up on the top of the mast of the thing and I've forgotten now how many of us went on this expedition. But one of the fellows, whose name by the way you should have had earlier and I didn't mention it, [Sullivan: C.B.] Strang, who was elected to go up and be on the top of the mast with the controls to keep that antenna pointed at the Sun as the ship rolled around. It was the most difficult eclipse operation that we undertook because of this lack of stability in the platform. As a consequence, we didn't have a nice, continuous record that we were able to obtain later. But we did have enough to give us a good curve.

Sullivan

And what size dish was it?

Hagen

As I recall, this is from memory, I'd say about six feet.

Sullivan

And you brought this dish along also?

Hagen

Oh, yes. We put a regular fire control mount and put the dish on it up on top of the mast.

Sullivan

Did you know that the Russians were also observing this?

Hagen

I don't think we knew that until afterwards. They were in a port in South America.

Sullivan

Yes, Baya Bay or something like that in Brazil.

Hagen

I can and I've forgotten the other port’s name.

Sullivan

[Chica?]

Hagen

[Chica?] that sounds right.

Sullivan

They had the same problems though. Even though they were in a port, they had to steer the whole ship by moving the ropes.

Hagen

They had a little easier problem though than we did, cause they observed at a lower frequency where their machine was [?]. But nevertheless, that was a good observation.

Sullivan

Sort of interesting to have the U.S. and the Russian Navy...

Hagen

But in all this time, I've never talked with [?].

Sullivan

And the second eclipse, is that the one in Alaska in September, 1950?

Hagen

That was at Attu, yes.

Sullivan

In which there's a very nice, from my point of view, Sky & Telescope article. Was this the one that [Grote] Reber went along on?

Hagen

Yes, Reber was along to do a 50 centimeter experiment. He'd been, there was another fellow with him from the Bureau of Standards, his name was Beck.

Sullivan

That's not the same Beck that was at Bell Labs and worked with Jansky?

Hagen

No, this was a young fellow.

Sullivan

And what did you find, you had several different wave lengths - you had 65, 10, 3 and .8 cm.

Hagen

Yes, and we had very bad luck on that thing because a very, very severe storm came through on eclipse day. We had, in addition to the radio, we also had a large optical telescope there. Of course, that was completely washed out. The 8 mm results were completely ruined. I have forgotten about the 3 cm, whether anything useful came out of that or not. We did salvage the 10 cm I know, and I think Reber’s results on 50 were not too much affected by the rain. There was a very, very heavy - it was a typhoon.

Sullivan

Really, I normally don't think of them in Alaska. Let's just follow through this whole eclipse business. The next one was...

Hagen

In Khartoum.

Sullivan

In Khartoum. Was that February, 1952?

Hagen

Yes. That was beautiful; that was the best eclipse experiment I think we ever ran. Again, we took a large optical telescope and got good photographs of the corona and the inner corona. We had a 10 cm radiometer and an 8 mm radiometer. Unfortunately, we didn't take a 3 cm along and it's turning out now that that was a real oversight because one of the most important experiments you can do today is to get a good eclipse observation at 3 cm wavelength.

Sullivan

Because that level is important in theory?

Hagen

Yes, yes.

Sullivan

And why is that?

Hagen

Because of the- this will come out of the paper I’m about to publish. It's the 3 cm flux from the quiet Sun is symptomatic of a very, very interesting part of the solar atmosphere which is right below 10,000 kilometers height above the [?]. And a 3 centimeter eclipse observation, a good one, will answer a lot of questions.

Sullivan

I see. And I think there's still one more, is that right?

Hagen

Yes.

Sullivan

You reported on one at the Jodrell Bank Symposium in 1955.

Hagen

That eclipse was in [?], Sweden. And there again, we didn't have the best weather, but we did get good results at both 8 millimeters and 10 centimeters.

Sullivan

What is the purpose of going to an eclipse after you've been to Khartoum, to go to Sweden? What can you learn new?

Hagen

Well, it's not what you learn new; it's what you learn better. The Sun is never absolutely quiet - there's always some small active region somewhere on it, and the existence of the active region, especially if it’s anywhere near the limb, makes it difficult to reduce the eclipse observation and introduce a degree of question in your mind as to the validity of what you're seeing. And therefore, you do like to have two or three good eclipse observations with the distribution of the activity over the surface of the Sun is different from what it was before. This would confirm the conclusions that you drew. So we went to Sweden essentially to confirm what we did in Sudan.

Sullivan

Was there anyone else observing eclipses in centimeter wavelengths through these years?

Hagen

Not significantly.

Sullivan

Or doing work that could really be compared with yours? Maybe interferometric, no, that's not true.

Hagen

Well, interferometry, yes. Covington had a new and large array of sensitive can call it an array - we can call it an array- which he used at 10 centimeters, and that allowed him to confirm limb brightening at 10 centimeters. But I don't think of any group doing the same kind of eclipse work.

Sullivan

I don't think of any. Is that all of the eclipses? Have we hit them all?

Hagen

All the NRL eclipses, I think.

Sullivan

Right. Well, while this was going on, this was obviously one of your main interests, but there were other interests that were developing in the branch. Could you tell me what these were and who was really the force behind them?

Hagen

Yes. Last night I mentioned notes here. Let’s see what we covered. We did refer to the design and construction of that 50 foot antenna.

Sullivan

Yes tell me a lot more about that - how that came about.

Hagen

I've forgotten the exact date, but in the late 1940's we became convinced that a large steerable antenna was needed, for centimeter and millimeter work. We looked at many different designs and finally settled on a particular design and let a contract with Collins Radio Company to build the antenna. It was constructed in [?] segments which could be unbolted. So they machined the thing in Iowa using a template and then a milling cutter which was on a beam and could be programmed to follow a parabolic curve. They machined the thing there and disassembled it, drove it to NRL and reassembled the thing on the roof where we of course, went through a long series of mechanical checks to bring the thing back to the proper parabolic configuration. Once we had that up...

Sullivan

Was that more difficult than you thought it would be?

Hagen

Well, the testing was a difficult thing, yes. When you get something that big, and you have to measure things as small as you have, because we tested that to, I believe, either a tenth or twentieth of a wavelength, and I can't remember whether it was 8 or 5 millimeter, so that we were dealing with...

Sullivan

Oh, you wanted to use it at 8 millimeters.

Hagen

Oh, yes.

Sullivan

It never was, actually, though.

Hagen

Yes it was.

Sullivan

Oh, okay. You’ll have to tell me about that.

Hagen

And so carrying out those tests was difficult, we used a combination of mechanical and optical techniques to do it.

Sullivan

Can you tell me about these techniques, because this was all new territory, I think. This was the largest dish of its kind, wasn't it?

Hagen

Well what we did to test the thing out was to build a template, which could be mounted on a post coming through the center of the antenna and then swung around and measurements made between the template and the antenna. That was the primary method of measurement. We also used a- what did surveyors call it?

Sullivan

A theodolite?

Hagen

No, it wasn't a theodolite- it was a thing made by the Wilde Company in Switzerland; it's really what amounts to an optical lever. With that you can measure precisely at a distance, using a rod, and we used that to probe all over the surface. And the net effect was that we were able to confine the measurements of the template and measurements by the optical techniques or really surveying techniques, to measure the nature of the surface of the antenna. Following that, of course, we did the more practical thing of checking the pattern and the gain of the antenna at short wavelengths. That was no easy task, because you had to go a great many miles to get out into the front upper region. To really accomplish that we attempted to use a blimp which would fly through the beam way out to north of us, between us and [?] where it came from. And that was a very interesting series of events. We did get pattern measurements out of it, but a good deal of the time the blimp didn't know where it was.

Sullivan

You were plotting the right place, but they weren't there?

Hagen

We found out a lot about blimp navigation.

Sullivan

Now how far away was this blimp actually?

Hagen

Thirty or forty miles.

Sullivan

I see. And so that was actually the means by which you tried to gain...

Hagen

Initially. And then after that we used point radio sources.

Sullivan

You haven't told me about the mount. The Collins Company did the surface.

Hagen

The work on the mount we did ourselves, along with, and I'm a little bit foggy on the help that we had here. We had help from another Division in the laboratory prior to the fire control division. What we did was to use an old Navy gun mount, and then we had Collins build a computer that was really an analog computer.

Sullivan

Yes, I've seen that.

Hagen

Oh, you've seen it?

Sullivan

Oh, yes.

Hagen

To go from earth coordinates to celestial coordinates. And that was a very well made device - it worked quite well. Our biggest difficulty with the mount was one of stability. That was the mount was designed and built to operate a massive gun, but the gun didn't have the moment of inertia that an antenna has, and so we had to use [?] devices in the mount to squelch the oscillation. That was our biggest problem in quieting down the operation of the mount to get rid of these oscillations.

Sullivan

Was this especially after slewing or was this even when you were tracking?

Hagen

No, especially after slewing, but once you started tracking, it was all right. But if you moved the antenna rapidly, then that was very difficult.

Sullivan

Just for the record, what size gun was it mounted to?

Hagen

I can't put it on the record, because I don't recall if it was an 8 inch gun or big 16 inch.

Sullivan

I think I remember twin 8 inch someone else may have told me that.

Hagen

That may well be.

Sullivan

Now, how long was this whole process - calibrating the dish and so forth? It must have been quite a while?

Hagen

I would think, I don't remember, but I would say certainly all of one year. It took us a long time.

Sullivan

And when was it finished - can you recall?

Hagen

It must have been around 1952.

Sullivan

And then what do you do when you have such a nice, new toy?

Hagen

We did several things. We, of course, investigated the possibility for use at 8 millimeters, and we did make quite a few observations of the Sun at 8 mm. We never did carry that through to the point where we published them, but we had contour maps of the Sun. We had hoped with the resolution that we would get with that, that we would see the limb brightening at 8 mm. However, if you look closely at the problem- if you want to see limb brightening, you have to have a beam that's much, much more narrow than we could get with a 50 foot dish. To really see limb brightening at 8 mm, you'd need a dish that's couple of hundred feet in diameter at least.

Sullivan

What was it - a couple of arc minute beam or something like that?

Hagen

The beam on this dish at 8 mm, I think, was about two arc minutes, if I'm not mistaken.

Sullivan

Why wasn't this work published?

Hagen

We had so many other things we had that we were doing, we just didn't see the real advantage of publishing it.

Sullivan

When you say 'we', was this Gibson that was working on this?

Hagen

With me on this 8 mm, it was Gibson and Sees, I believe, and myself.

Sullivan

Was there an internal report or anything like that?

Hagen

I don't remember. I rather remember that we didn't even write an internal report, when we did not observe, and began to realize that we shouldn’t observe, the limb brightening. What we did observe was the uneven contour of the Sun due to the active regions. However, we had other things that we wanted to do with the dish, so we couldn’t see using it at millimeter waves for the Sun. We thought it would be much better to do some of the centimeter work where we saw a chance to make a real quick breakthrough. We looked for the distribution of radiation along the galactic plane, for example, and observed the X-2 region.

Sullivan

Let me ask about that experiment because that's a rather important one. You'd been working on free-free theory and so forth so you must have been well aware that HII regions would be detectable at certain level, was this in your mind as you were building the dish that this was going to be...

Hagen

Yes.

Sullivan

So I guess it wasn't a surprise then that you detected these things.

Hagen

Oh no, not at all.

Sullivan

But nevertheless, it was a first, and I guess it was published in 1954?

Hagen

Thereabouts.

Sullivan

And you also measured the flux of some other things besides H II regions at 21 cm.

Hagen

That's right. We measured the flux of some of the brighter radio sources at 10 cm and I believe, at 3 cm. That's an interesting point. We, this group that I had, were well indoctrinated on precise calibrations and so we had very good measurements on the flux of several, five or six, of the brighter radio sources. If you look back through the records, you'll find that if you extrapolated our results, they didn't meet the results of the people in England who had been doing work on flux of sources, and so you're led to a necessary curve. Over a period of years, the S has gone out of that curve, and the lower frequency fluxes have gone down to the point where they jive with these early NRL centimeters.

Sullivan

I see; that's interesting. I hadn't realized; I'll have to do some checking on that. Now what about the 21 cm hydrogen line?

Hagen

At that time, we decided that we had an excellent opportunity to do work at 21 cm and so we got a 21 cm receiver, purchased it from [Harold Irving "Doc"] Ewen, and the very first thing, as I recall, that we did with that, was to begin to investigate some of these bright sources. And I believe it was Taurus that we first observed and observed for the first time absorption of radiation by the hydrogen clouds.

Sullivan

This was not what you were looking for, this was just...

Hagen

We were not looking for that; it was just chance.

Sullivan

Right. Let me just ask you a question before we go on. The 21 cm line was not part of the original impetus to build the dish. It just came along in the process while the dish was being built.

Hagen

That's right.

Sullivan

Okay, now back to this story. I'd be interested in an account of this discovery, because when the line went the wrong way, there must have been a lot of checking.

Hagen

There certainly was. And a lot of back of the envelope work, trying to understand why the thing did go the way they did go, and we finally convinced ourselves that 'yes' we were seeing absorption. We then went and looked at Cassiopeia and found the same thing. And we then began to realize that there was more than an intellectual interest in this thing because by that time we had a foggy notion of what the spiral arms were like. The fact that we had this absorption showing up as it did with the velocities of Cassiopeia, we were able to say that Cassiopeia was a lot closer than astronomers earlier had thought. So I think, for the first time, did a rough measurement of the distance of Cassiopeia.

Sullivan

Right. I want to talk about that quite a bit. Let me ask, this probably wasn't right at the beginning, the distance method came upon you, or was it? The first thing was just sort of to figure out what this absorption meant.

Hagen

That's right. The first effort was on the Taurus experiment to really understand what the absorption meant and how you could explain it away theoretically. Then we went, I don't know, I say then- after that time, we went to Cassiopeia and saw absorption again and then set about to really explain what we saw and when we did, we did two things: one of them was to get a model of what the hydrogen cloud must be like in order to provide that kind of line picture that we saw. And also as an added thing, we realized that this tells you that Cassiopeia cannot be as far away, it was just [?].

Sullivan

Based on the Dutch work on galactic structure and emission.

Hagen

Yes, exactly.

Sullivan

Do you remember specifically how this idea of using it as a distance method came about?

Hagen

No. The people, [A. Edward] Lilley, McClain, and I were working together on that thing and I could not tell you frankly who came up first with that idea. It was a team effort, and when you think back, you don't know who did it.

Sullivan

But now there is another question relevant to this, there were two papers published as you probably remember, Hagen and McClain in ApJ in 1954, and then Hagen, Lilley, and McClain in in 1955, which is a much more extended paper going into all of the theory of absorption and such. Did Lilley join the group?

Hagen

Lilley joined the group at about that time.

Sullivan

Just after your discovery?

Hagen

Yes.

Sullivan

And it seems from a reading of the paper that you and McClain did not have quite today's idea anyway, I want to avoid saying the "right" idea, about the nature of this absorption - namely that, it's only a couple of sentences that’s relevant but it seems like you were thinking of the source actually blocking the hydrogen behind the source. Is that a fair interpretation?

Hagen

No. I think McClain and I felt- I how you arrived at that but McClain and I, I think if you look at the paper, said that the hydrogen was in front of the source. Initially, when we first ran into this, our early-off-the-cuff discussions were, "Could it possibly be the source blocking the hydrogen?" But by the time we reported the paper I think we had that straightened out.

Sullivan

Well, I have it in my room, so are you at [URSI] Commission 40 tomorrow morning?

Hagen

Yeah.

Sullivan

I'll bring it along and we can take a look at it.

Hagen

I'd like to see that.

Sullivan

It seems it’s the other way, but I don't have it.

Hagen

You're dealing with a memory of way-back-when.

Sullivan

So what you're saying is that, in any case, it wasn't clear which way it was.

Hagen

To begin with, we had certainly suspected it both ways. But my recollection is that by the time we had published that first paper, that we had sorted that out.

Sullivan

Is it fair to say that Lilley did most of the- I haven't talked to him yet- that Lilley did most of the modeling in the second paper? That's what it looks like from the outside because he is the different person.

Hagen

I think you'd say that- I wouldn’t want to take credit away from McClain actually. We did work awfully closely together as a group, and again, it's awfully difficult to say, "Yes, this fellow did that and that fellow did that," because things were going back and forth. But there's no question but that Lilley was the spark plug there, there's no question about that.

Sullivan

Was he one of the first people who joined besides the original group? I guess Nan Hepburn [Nannielou H. Dieter], as she was called then, also...

Hagen

Oh, I had forgot about Nan.

Sullivan

Was that true that you didn't really have a lot of new people until about this era?

Hagen

We had people, Nancy Roman worked with us for a while, you know.

Sullivan

But that was a little later.

Hagen

Yes, that was a little later, late ‘50s. The group was pretty stable, there weren't too many people coming and going. Few people came and few people left.

Sullivan

Of course, that's been true for the last ten or twenty years also. But it's also interesting that no one else bothered to get a Ph.D. in astronomy. Do you have any thoughts as to why, did it just seem like an unnecessary thing to learn astronomy or was it that the best way to learn astronomy was by doing it?

Hagen

When you say nobody else, do you mean in the...

Sullivan

In the NRL group.

Hagen

In the NRL group? Well, that's awfully hard to explain. First, it takes a tremendous amount of effort to work at a place like NRL and then at the same time go out and get a Ph.D. Now did [Robert J.] Coates did. Coates did and he's the only one I think that did. It just...

Sullivan

No, you're right and once you've got a family...

Hagen

It's more than a lot of people want to do.

Sullivan

Okay. Now you've brought up this meeting that was held in January of 1954 which was held in Washington, D.C. And you actually gave in Science that year, you gave a report of that meeting, this was a rather important meeting I think, especially for American radio astronomy. Could you tell me about that?

Hagen

I wish I could tell you - I didn't know I was going to be talking with you or I would have looked at some of these things.

Sullivan

Well, once again, when the transcript comes, maybe you can...

Hagen

Memory is a horrible thing. I was afraid that I would say things that I think are true, but really aren't. You know, it's awfully hard to remember some of these things.

Sullivan

I have a lot of other cross-checks. Other people tell me about the meeting, too.

Hagen

As I recall it, the reporting of that meeting was pretty thorough, and I think your best way of finding out what went on at that meeting is to read the report.

Sullivan

You don't remember particularly the atmosphere of the meeting, or maybe something that couldn't be garnered from the report?

Hagen

No, I was too damned busy at that time to really go around feeling for atmosphere. I couldn't tell you.

Sullivan

But now a national observatory at that time was a new concept.

Hagen

Brookhaven.

Sullivan

But in astronomy, I mean.

Hagen

In astronomy, that's right.

Sullivan

And certainly no other radio groups were operating along these lines. So how did this - did it come out of Brookhaven, basically?

Hagen

It came out of the notion, the idea of Brookhaven, yes.

Sullivan

And...

Hagen

We had been talking, we'd built the 50 foot dish and so Siece and I spent endless hours looking at bigger dishes. We thought about 400 foot dishes and had all sorts of schemes as to how to build them, but behind that was the tremendous amount of financial support that would be required. We knew that we couldn't get that out of the Navy, so I talked with Menzel for example and with Berkner and out of that came, we thought, "Maybe if we had a joint effort, we could do something like that." And again, it's hard to trace it step-by-step, but that led to the meetings that we held under the auspices of the Associated Universities, where we discussed the possibility of some kind of joint effort to build a large facility and discussed what that large facility should be.

Sullivan

And what did you think it should be at that stage?

Hagen

At that stage of the game, we were just thinking in terms of one big antenna, as large an antenna as the techniques of the time would allow us to build, and the funds, the financial situation would allow us to build. And we realized in the meetings that the antenna would have a dual purpose, that possibly it would be used both for solar and for galactic work. But evolution took over and what went on, of course, at the National Observatory when it was built, was that there was very little of any solar work done. But in the beginning, solar and galactic were both...

Sullivan

And so it was going to be a 300, 400 foot antenna good to- what sort of wavelength were you...

Hagen

Well, we wanted to get down to a short centimeter wavelength if possible.

Sullivan

So this might be called sort Jodrell Bank sort of outlook, that a big dish was the way to go.

Hagen

That's it.

Sullivan

Well, this pops in my mind and leads to another question. And then it might seem that once NRAO didn't quite get all the funding in the beginning, and so forth, that might have been hoped for and that for several years, there was only a single 85 foot and so forth, was Sugar Grove then at all, is it fair to say, seized upon as possibly a way one could realize what hadn't worked at NRAO in terms of getting a big steerable dish?

Hagen

Well, I don't know the whole of that Sugar Grove story, and part of it you couldn't tell if you knew it. That Sugar Grove came out of really the NRL work; but to get to the Sugar Grove stage outside of the radio astronomy group at NRL.

Sullivan

For military purposes?

Hagen

Yes. And well, I guess the less said about that Sugar Grove thing, the better.

Sullivan

Well, it's part of the history.

Hagen

It was obviously a- the problem there was not technical. It was management problem. If technical people had full control over what was going on, at least if I were one of the technical people, that thing would have been built.

Sullivan

Yes. Some other people have told me some aspects of this thing and apparently, the Bureau of Yards and Docks felt that they were the ones that had to get involved and they may have known how to build yards and docks, but antennas are something else.

Hagen

That's right.

Sullivan

When did you leave NRL?

Hagen

I left NRL in- oh gee you see in 1955, I by that time, I had become head of the Atmosphere and Astrophysics Division.

Sullivan

I see, you were head of the whole division.

Hagen

And we had all this rocket work going on and we had developed the idea of a satellite capability, and so when the IGY came along, and the Vanguard program was started, I resigned the directorship of that, and that was in 1955. I think NASA was born in 1958, and Vanguard was one of the building blocks of NASA. So Vanguard was transferred over to NASA and I went over to NASA.

Sullivan

I see.

Hagen

So I sort of walked out the back door of NRL.

Sullivan

Okay, I'd like to ask you a couple of things about that and we can finish up the radio astronomy before then. You mentioned about the distance of Cas, which indeed, was a controversy for a couple of years because people with great authority like [Rudolph] Minkowski said that the thing must be at such-and-such a distance, let's see, how did the thing go? You wanted to have it at around 3 kiloparsecs, just between the what we call the Orion and the Perseus arms and Minkowski was saying that the proper motion study said that it must be much more distant. Or no, did they say it had to be very close?

Hagen

No, further away.

Sullivan

And Ed McClain actually showed me a letter that he had from [Walter] Baade saying that you were right, essentially, after this whole thing settled down. He was very proud of that letter, sort of explaining how they went wrong. Were you involved in this at all?

Hagen

Oh, yes.

Sullivan

Can you remember from the meetings of that time, what went on?

Hagen

Not really.

Sullivan

Perhaps the Jodrell Symposium in 1955.

Hagen

Well, I was going to say, the thing, we didn't treat that thing as at all contentious. I reported it in a very matter-of-fact way with Minkowski sitting ten feet away from Ed at this Jodrell Bank meeting, and as I recall it, there was no...

Sullivan

Continuing with John Hagen on 27 August ’76.

Hagen

I was going to say that subsequent or shortly after that, and I don't recall the exact date, I was invited out to Caltech to spend a month or so, and while I was there, I of course, gave a symposium or colloquium on this matter of the hydrogen line and absorption and what one could learn by using these techniques. And I was not really questioned on the accuracy of the conclusions that we drew about Cas. So I think they had accepted it.

Sullivan

And what year was that?

Hagen

That was very shortly, I think, after the Jodrell Bank meeting, that it had to be before 1955. I don't know the exact date. Must have been 1954, perhaps.

Sullivan

Do you remember any other things about this Jodrell meeting as to the state of radio astronomy at that time? How it struck you?

Hagen

At that time radio astronomy was carried out by a- when you stop to think of it- a very small group of people worldwide, and everybody working in radio astronomy knew everybody else and knew them well. And so these meetings were always very pleasant occasions where people got together and reported their results and had very good discussions on the results and the techniques. So you think back, you wish that today things were the way they were then.

Sullivan

A much different sort of science.

Hagen

A much different sort of science, yes.

Sullivan

I was thinking also of scientific issues. Things that you might have learned at that meeting that you weren't aware of?

Hagen

Yeah, but I can't tell you what they were. At that time, things were moving so fast that every meeting you went to, you found something new, something that you hadn't known before. It was a very exciting time in the history of radio astronomy.

Sullivan

You actually gave several talks at that meeting according to my records here, about the 8 mm eclipse observations, the S-shaped Cas A spectrum that you mentioned...

Hagen

Yeah that thing I talked to you about.

Sullivan

The Cygnus A spectrum, the 9 cm eclipse observation in Sweden, your 21 cm absorption. So that was quite a bit. I guess you were the NRL representative, is that the idea for all these different things?

Hagen

Yeah, I don't know who else from NRL was at that meeting. I'm not sure. My memory is not good.

Sullivan

Let's see, do I have any other papers here that I haven't gotten? The only other one that I might like to ask you about is that this apparently was what you got for your brightness temperature versus radius curve from the 1954 eclipse at 8.6 mm.

Hagen

Oh, yes.

Sullivan

You got a dip before the limb. Could you tell me about that?

Hagen

I’m glad you brought it up. That's an important thing. That bothered me for a long time, because it didn't fit the model that I had constructed, and so I set it back to see what one could do to explain that away, and that led me to think in terms of the spicule, and so if you assume a spicule model of the chromosphere, then you can demonstrate that you can have this, what looks like a double peak with the inner peak not being sharp, at these millimeter wave lengths with penetrations deep enough so you see the spicules. That was the first demonstration that I had of the effect of spicules on radio radiation. And from that I derived or evolved a spicule model, but any further work there has to wait until a more accurate 8 mm eclipse observation is possible. Now we've had recently two eclipse observations at 8 mm and I think by the time they're completely analyzed, maybe you can say more about these spicules.

Sullivan

I was just noticing that at this Jodrell Bank meeting, that after you gave your talk about the 21 cm absorption, there were some comments by Lilley and [Jesse L.] Greenstein on a possible reinterpretation of the data for Cas A in view of the distance discrepancy between radio and optical data. It doesn't say specifically how they want to do that, but I gather they...

Hagen

So Lilley was there.

Sullivan

I gather that they wanted to probably reinterpret the radio data to make it come in line with the more reliable optical, do you remember this at all?

Hagen

No. I don't remember Greenstein discussing it at all.

Sullivan

Maybe it's actually recorded in the symposium itself. This is just an abstract.

Hagen

It may be.

Sullivan

It probably is. I'll have to check that. Okay, now if you could just expand a little bit on your work with the Vanguard, it was a very different field, it got you into space radio- well, no I've got you mixed up with Haddock. Haddock did a space radio astronomy experiment in the early 1960s. I don't think you did any space radio astronomy, did you?

Hagen

No.

Sullivan

But, nevertheless, while we've got the recorder here, and so forth, could you just tell me a little bit about that Vanguard program?

Hagen

Well, the Vanguard Program came out of originated in a resolution that was passed by URSI, probably about 1953 or 1954, and it was agreed, finally, that an Earth satellite, or an attempt would be made to put a satellite in Earth orbit during the IGY [International Geophysical Year]. The National Academy [of Sciences] picked that up and gave its support, and the thing through the National Science Foundation got Congressional approval and some financial support. There was a great deal of fuss about who would do this, and a committee was established to choose between a proposal put out by the Navy, which came out of my group, a proposal from the Army, and a proposal from the Air Force. The committee looked at the observable information, and on the basis of that, decided that support should be given to the Navy's proposal, and so Project Vanguard was started in the Naval Research Laboratory. Since the work came out of my division, they requested me to take over the responsibility for directing the effort. The commitment that we made to the Academy was that we would have a satellite in orbit before the end of the IGY and the Vanguard met that commitment. As you know, it wasn't as simple as all that, however. There was a great furor after the Russians, who unbeknownst to us, had set out to use their military equipment to really launch a satellite and they preceded us. The point I think we ought to make here is that we were very straight-laced about this thing. Every effort made in the United States that the Vanguard effort be purely a non-military thing. We were not allowed to use military techniques. We weren't allowed to use military vehicles. So we set out and developed our own vehicles, developed our own stages of the rocket.

Sullivan

And you mentioned before that you actually when NASA was formed in 1958 that- this was after the first launch. So it was done at NRL, so it must have looked military to the outsider anyway.

Hagen

Yes, it looked that way, but it really wasn't.

Sullivan

And you didn't know, at all, that the Russians were...

Hagen

There was no indication to us that the Russians were preparing a satellite. I think that if you look at the record, it certainly was true that it was known to our intelligence people, but it was not known to us.

Sullivan

The usual trouble with a big government. Nevertheless, did you feel some pressure in terms that they might do it and it'd be nice if the U.S. did it first?

Hagen

Not really. If we had felt that way, our program would have been accelerated because we wouldn't have attempted to do as professional a job as we thought we were doing [???]. We actually changed the design of the rocket to accommodate a larger sphere than we had proposed which set us back six months or a year. Had we had an inkling that the Russians were pressing, we wouldn't have done that.

Sullivan

Just to get something up there.

Hagen

It's probably just as well that it happened the way it did.

Sullivan

Did you think the Russians were inspired by this resolution that you mentioned at all?

Hagen

Oh, yes. Oh, yes. They did it as part of their IGY. But they went at it, I think, a little different way. They said, "We'll just use the military technology we still have."

Sullivan

Why was there this U.S. philosophy? I mean, why couldn't you just buy a rocket from the military and stick your payload in it?

Hagen

It's hard to explain. You get into a lot of odd...

[Interruption]

Hagen

They wanted this to be an effort of the scientific community and not an effort of the Department of Defense.

Sullivan

I see. Since it was IGY...

Hagen

It was IGY, yes. Had the military done it, well it would have been, the nature of the thing would have been quite different.

Sullivan

Yes. I gather you were not in favor of the military doing it, either.

Hagen

That's right.

Sullivan

And now I must admit that I'm a little bit fuzzy as to the Vanguard went up in January 1958, is that right?

Hagen

In March.

Sullivan

March. After what two Sputniks had gone up?

Hagen

I believe it was two. Two, I think.

Sullivan

And the Vanguard was the first U.S. one?

Hagen

Well, no it was not.

Sullivan

That’s where I’m getting mixed up.

Hagen

No, a Redstone vehicle, which was an Army device, put up the first U.S. satellite, which was an Explorer. I think that one went up in January or February, something like that.

Sullivan

So what happened is that once Sputnik went up, the U.S. people said you've got to get something going.

Hagen

Once Sputnik went up people went crazy, and they were not prepared for the problems that any rocket program has in the development stage and they saw Vanguard actually had a launch failure in a test vehicle. The very first failure the program had after a long series of tests. And that was seen, these people started tearing their hair out, and a fast sell was made.

Sullivan

I see. Did anyone at that time have any notion- I mean, in retrospect one would say that whoever put up the first rocket would have a tremendous amount of prestige in terms of being number one in science and all this sort of thing. I mean, of course, it influenced the whole U.S. educational system and everything after that.

Hagen

Well, not really. We were so damned busy getting the job done, I don't think...

Sullivan

You didn't see it as particularly more influential than other important scientific projects?

Hagen

That's right. After the fact, you can look back and think, "Yes, you're might have," but at that time, we were really busy night and day.

Sullivan

Okay, in my study I'm going through these early ‘60s. Did you get back into radio astronomy at all?

Hagen

Oh, yes.

Sullivan

Can you tell me about that please?

Hagen

I retired from NASA in 1963 and took a job at the Pennsylvania State University as a professor of astronomy, and started a new program in radio astronomy there, with again, total emphasis on the Sun. So we had over a period of 13 or 14 years, a long series of accurate measurement of solar flux at wideband frequencies, plus two eclipse experiments at 3 millimeters and 8 millimeters.

Sullivan

I see. Well, what did you do right at the-very beginning before 1965?

Hagen

Got a bunch of graduate students together and taught them about radio astronomy and had them build equipment. And so we got some equipment going on the Sun right away.

Sullivan

And what sort of project was it?

Hagen

By that what do you mean?

Sullivan

I mean, were you looking at bursts?

Hagen

Oh. Well, we were looking at bursts but also were getting data so that over a long period of time, one could extract flux information on the quiet Sun. That's the important thing theoretically; what is the flux of the quiet Sun? You can't do that by going out today and just making a measurement. You have to measure over a period of 10 or 15 years.

Sullivan

Right. So that's what you'd been doing at Penn State ever since. So in closing can you think of any comments you'd like to make about the development of radio astronomy at NRL or how it compares with other laboratories and so forth?

Hagen

The only thing I'd say is that I was very pleased with the group at NRL. They kept on going as successfully as they did after I walked out on them. I think they’ve done a good job under the circumstances against their will. It just makes me happy to see them do it. It's a good thing to see that some of the fellows that are there now go way back to the beginning.

Sullivan

It is true, I would say, that up until 1960 or whatever, 15 years almost, of all of this microwave stuff, there was very little competition really. You were by yourself in this field, weren't you?

Hagen

Yeah and the only thing that was lacking was money. We never did have the financial backing to build the larger equipment that really was needed to make NRL stand very a far out.

Sullivan

Hagen also told me that he went up at an early stage, 1946-47, and visited Covington's new antenna and knew about its operation even as the NRL one was beginning. So that ends the interview with John Hagen on 27 August ’76.