Interview with William E. Gordon
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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.
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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Sullivan
Ok, this is talking with William Gordon at URSI [International Union of Radio Science] in Helsinki on 4 August ’78. Could you tell me when you first came into contact with radio astronomy?
Gordon
The early contact was in 1947 when I earned my stipend at Cornell as a graduate student using a rig that Charlie [Charles L.] Seeger had put together to monitor solar radio noise at a couple hundred megahertz.
Sullivan
This is in the Electrical Engineering Department?
Gordon
This was the Electrical Engineering Department; I was a graduate student and at that stage, Charlie [Charles E.] Burrows was and throughout my degree was my major professor. Henry Booker arrived a year or two after I did and was very influential in my career. With Henry, we looked at the propagation of radio waves beyond the horizon by scattering, now called tropospheric forward scattering. And it became a big business and it produced a thesis for me.
Sullivan
What was Burrows' area of expertise if I may ask?
Gordon
He was a radio wave propagation man who had been at Bell Labs for a number of years and during the war was very much involved in the war effort and radio waves and what happens to radars as they are influenced by weather. After the war he went to Cornell where he was director of the department.
Sullivan
Do you remember what his motivation was for setting up the small radio astronomy program?
Gordon
I suspect he was just aware that the war had produced interference to radar which turned out...
Sullivan
Something to find out about.
Gordon
Not quite begin with radio astronomy, [Grote] Reber and [Karl] Jansky had previously done something with it. Well, my motivation that led to the Arecibo dish was really radio scattering. I did a thesis in the troposphere which was successful. I did some work on stratospheric scattering of radio waves, which produced communication links of the order of 600 miles compared to the 200 for the tropospheric scattering. Henry did the ionosphere forward scatter, which produced communication over 1,000 miles or so and was a big part of the military DEW-line communication operation. We were really, we were electrical engineers involved in communication. And we were exploiting radio scattering...
Sullivan
But also ionospheric physicists...
Gordon
Well, it was working its way up, you see. It started in troposphere because there were problems to deal with and we got them at least theoretically what we thought was a reasonable statement. And then simply said, "Well, if it happens there, wouldn't it happen higher up?" And of course, the effects were there and they could be predicted and got I think a significant use of communication channels. It was, let's seem I got a degree in 1953, my Ph.D. from Cornell. In 1958 I was still going along the same lines. I was wondering we had the forward scatter by ionospheric propagation Henry had done, and I wondered was there not any other kind of scattering that might occur in the ionosphere because by then we were beginning to think about ionospheric- I was beginning to think about ionospheric physics. And I did the classical calculation of the scattering from a single electron- it’s been done that many times before, but in the past I did it and could push it through, which most graduate students could also do, but then I put that together with the availability of hardware in those days you could say there is scattering from individual electrons. It's extremely small, but hardware has come a long way since the war and if you put together the best transmitter that was available and made some selection of wavelength to minimize the sky noise versus the equipment noise, found your way into an appropriate wavelength region.
Sullivan
What region was it?
Gordon
That brought us dawn to about 1 meter in the final selection process and the final selection from Arecibo was 70 cm but it was a fairly flat minimum. What it said was that you could detect in the ionosphere the number of electrons, the electron density is a function of heights, the kind of thing that an ionogram produces on the bottom side and the alouettes now are the top side [?]. But you could do it from the ground that a frequency that normally would have said that the ionosphere was transparent- you could do it all the way through. But when you just put it all in the radar equation which was appropriate for a being filled situation, like the ionosphere, it then turned out that you needed a very large antenna - in round numbers, it was 1,000 feet, that was a nice number to settle on. It was big and challenging. It was a very exciting time for us, to run around to the civil engineers and the mechanical engineers and see what they thought about, "Could you build 1,000 foot dish?" The spring of 1958 at Cornell was a very exciting time. It had nothing to do with radio astronomy.
Sullivan
Right.
Gordon
It wasn't difficult to get study money to look into it. The ONR [Office of Naval Research] almost within a week produced money that we could...
Sullivan
Those were the days.
Gordon
Exactly. And in those days, if you thought about the NSF [National Science Foundation] as a source, you quickly said, "They're not a possibility," because the amount of money we're talking about was in the millions and they were really just getting started. Well they weren’t just getting started but they weren't very far along.
Sullivan
A very low level compared to the military, yes.
Gordon
It then became apparent that if you could measure things like electron density and there was some development, some thoughts going into the theory of what was going on as well as the hardware side of it, you could not only measure the electron density, you could measure the electron temperature, the ion temperature and maybe something of that proposition- all of these as functions of height, essentially continuously. It quickly developed that that was the kind of information that the military people were interested in because they were thinking in terms of, at that stage, of missiles in the upper atmosphere and not long after that. And so ARPA, the Advanced Research Projects Agency was the only source that had the courage and the resources to look at a project of that size. So we spent a lot of time commuting from Ithaca to Washington, selling them on the project. Ward Low, who was the man who was responsible, who was in IDA, the Institute for Defense Analysis, was one of the advisors of ARPA, was quite influential in the following sense, that when we went in, we said, "If we could build a thousand foot parabola and it would have almost no motion of the beam but it would do all of these things about the ionosphere." And Ward knew that some people at Cambridge, the Air Force Cambridge Research Lab, who were experimenting with spherical antennas. And they had built a 10 foot dish and had built a line feed to correct the spherical aberration. He knew that was going on, so he challenged us in a sense by saying, "You really don't want to build a thousand foot dish with a one degree scan, you want to build it with some tens of degrees of scan." And he said, "Why don't you go talk to the [Phil] Blacksmith and his colleagues at Cambridge?" So we did.
Sullivan
This Low, is that L-O-W?
Gordon
Yes, Ward Low. And Blacksmith and well, several, Bouche and Schell who's here and Allen [?] who's here, all had been either in-house or under contract producing the feed which was the critical problem, not the spherical dish are a little but easier to produce but they had produced some line feeds which were moderately successful.
Sullivan
What was their motivation?
Gordon
Their motivation was to get a situation in which you could have a fixed dish and by scanning a feed, you could get a...
Sullivan
So once again, you could do a large dish.
Gordon
Yes, instead of picking a dish up...
Sullivan
I assume that you didn't really spend any serious time thinking about a movable dish of that size.
Gordon
No. At 1,000 feet it was clear that we needed, well, CE told us what you need is a hole in the ground of the right size and you're going to shape it a little and sit it in the hole and you’re not going to pick that up. But it was also clear that the style of the spherical dish, you could conceived of building a super structure on which you supported the line feed and moved it from one radius to another, and as you move it from one radius to another you moved the beam, which was parallel to that radius. So the Air Force Cambridge got into the business with us through ARPA. And between the summer of 1958 and the summer of 1960, we had hired, well, we had developed the idea to the point that ARPA said they would be willing to invest substantial amounts of money. We'd hired A & Es, Architect/Engineering firm, through a competition. It was a cooperative thing at Cornell of EEs and CEs primarily. Bill McGuire in Civil Engineering and George Winter was the principal CE and Henry Booker, Ben Nichols, Marshall Cohen were involved on the EE side. And so we put together a proposal and then the detail work had to be done externally. So what we have at this stage is a facility which would not only see all of the properties that I mentioned earlier straight overhead, but would see them in a cone. And the cone angle turned out to be 20° half-angle which we felt was marvelous but difficult. The structure...
Sullivan
Difficult to make something that would move around.
Gordon
Yes. And the line feed was a separate problem, and Allen [Kay?] had a company of his own.
Sullivan
Were there problems that it just wouldn't scale up or was it just a matter of supporting the line feed?
Gordon
No, supporting. You're talking about roughly a 100 foot long slim column of wave guide and it had to be self-supporting. There were interesting challenges all through it.
Sullivan
None of you had done that before.
Gordon
No, the biggest one was 10 feet - the 10 foot dish before. So in a sense we were scaling up two orders of magnitude in a linear dimension. And that was a big scale. But with the encouragement of the Cambridge people and support of the ARPA people, we were able to get on with the design of 1,000 foot spherical dish which would give us 20° scanability. It became clear then that if you built the radar of that size, you could not only see things in the upper atmosphere but you could see the Moon which had only just begun to be marginally detected in those days, in ‘58. And you could make calculations which showed that you could easily see the nearby planets, the limit there was going to be the scanability- would they go out of your field of view with the Earth sweeping by them before the echo came back. That was an interesting limit.
Sullivan
Which now, of course, is limiting things as far as Saturn goes.
Gordon
That sort of puts a Saturn limit up if you stay in one station. So it was clear that you could not only study the ionosphere but you could do some things in radar astronomy and so that influenced very much the site. To do the radar astronomy on the planets, at least, you had to be in the tropics. That pushed us. Well, as our civil engineer friends said, "Where do you want to go? You can put holes in the ground in Mexico, Bahamas, Cuba would have been crazy. Puerto Rico, Hawaii. We can look in the other half of the world if you want me too." All he was saying is there's [?] topography in lots of places and that just what you want to get the hole you're looking for.
Sullivan
So the tropical location was not dictated by ionospheric requirements.
Gordon
No, the point there, I think was that there was a great deal to do in the ionosphere no matter where you were. And there was only one region in which you could do the planets as long as you had this limit on the scan, and so it roughly said the tropics.
Sullivan
Was there anyone who particularly pushed the radar astronomy side or was it just sort of everyone agreed that...
Gordon
At that stage, it was simply a fringe benefit of the, and I think at Cornell in those days, we didn't really have a radar astronomer.
Sullivan
I don't think so, no.
Gordon
No, we didn't. So it was simply a fringe benefit of the system and it was also obvious that if you have a collecting area of 1,000 feet, there were going to be some radio astronomers who would have some interest also.
Sullivan
Right. That's what I wanted to ask, it seems to me that that could be argued at that point to be even more beneficial than the radar astronomy side. Was that so or was it just even more minor than the radar astronomy?
Gordon
I think it went in that order, that it was developed to do ionospheric things but it was apparent that that powerful a radar would be useful as a radar and radio astronomy and the collector without the transmitter would have some use in radio astronomy. So those were kind of fringe benefits of building it.
Sullivan
But there was nothing that happened, for instance, like the U.S. radio astronomical community coming and saying, "Well, gee, this is fantastic."
Gordon
You know, in many ways, we can say those were the good old days. There were no committees - we had to convince and continually sell and resell the people in ARPA and they would get uneasy, they didn't really know whether any coherent scatter was just a crazy idea or whether it had some substance. They would come up, they'd get uneasy and call me down and say, "You know, there's a plasma physicist at Princeton, why don't you go tell him what you're thinking about and then I'll talk to him"- it was sort of a test. That was repeated in many different ways at many different times. But we never had the community of [?] or the community of astronomers who voted and said this is a high priority [?] proceed. It was proceeding as a very small part of the ARPA budget, of course.
Sullivan
Yes, but a very big part of ionospheric science.
Gordon
Of course.
Sullivan
Were the ionospheric physicists...
Gordon
Yes, they were excited. In a sense, they didn't feel threatened because we weren't going after NSF money, we weren't going after ONR money or Air Force money which were the sources at that time, and they could see that it was kind of a big boost for everyone. It’s kind of a nice side comment on the support of science. In a sense, we were diverting a bit of the military funding for science and were happy to do that. But on the other hand, I must say, it did what we wanted to do at Cornell and what the military needed to know - it did coincide.
Sullivan
That's what I was going to ask you. Did you have to make any compromises for the military sake?
Gordon
No, I don't think so. And we, their interests frequently were of a classified nature. I'm not sure for a good reason, but they were, it doesn't matter. And our interests were in discovering something, learning about the upper atmosphere. I think it’s fair to say they needed to learn more about the upper atmosphere and so they were willing to go along with us in effect.
Sullivan
But in fact, there were no secret projects that were done with the thing.
Gordon
The project was never classified; we were out in the open. Well, in the '50s you could have done classified work on the campus, but you couldn't in the '60s.
Sullivan
Well, only till the late '60s really.
Gordon
Well, there was some sensitivity in Puerto Rico, too. The Puerto Ricans were, I suppose, a bit suspicious that we were some big military thing coming in like all of the bases.
Sullivan
Well, they still are, of course. But what about the final choice of Puerto Rico. What led you there?
Gordon
That was an interesting choice. By accident, we had had a professor from the University of Puerto Rico at Mayagüez who was a student at Cornell. He was sent there to get his Ph.D. and he worked with Henry Booker and me and got a degree. He got it in, must have been, middle '50s. And that gave us a lead into Puerto Rico. His name was Dueno, D-U-E-N-O and Dueno was most cooperative. And Puerto Rico was a freely associated state, it was in a sense, part of the U.S.
Sullivan
You didn't have diplomatic problems.
Gordon
No. It removed a whole series of problems. As soon as we contacted Dueno and said, "We'd like to come down and look at sites and come down and do radio surveys on where the noise levels and so on." We had a warm reception. Though you could say the same thing about Hawaii, I think, except it was much further away from Cornell. The choice was pretty simple. I think our civil engineer man looked at the aerial photographs of Puerto Rico and said, "Here are a dozen possibilities of holes in the ground in roughly the dimensions you need." And we looked at some and said, "Well, that's too close to a town or a city or something." Very, very quickly he reduced it to three and he and I went down and looked at them and picked one.
Sullivan
When you mentioned this size, I noticed in one of these abstracts for 1960 Cornell Report it mentioned a 1500 foot dish, did that get dwindled down?
Gordon
Okay. There was an early stage when there was an option that we would build the 1,000 foot dish, but if you- the choice was the following: you could build a feed that would illuminate the full 1,000 feet when you look straight up. Then if you look anywhere off of the vertical, you have some [?] and some loss of gain. You could avoid that if you built something like a 1500 foot dish and illuminated the 1,000. So we proposed that as an option at one stage for some additional funding, I've forgotten the details at the moment, it was not sold. We were not pushing it very hard. From the ionosphere point of view, we were mostly interested in looking straight up anyway. And so it didn't succeed, it was tried but not successfully. It's interesting to note that the S band feed that is currently in use, does illuminate only 200 meters.
Sullivan
Right and so do radio astronomy feeds also.
Gordon
300 and [?] when we do the scan.
Sullivan
So, in fact, if it had been 1,500, we would have a wider - no, that's not true, you still have to have more track upstairs to go further than 20°.
Gordon
Yes, you'd have to extend the track. You use fully the track that's there to do the 20° scan.
Sullivan
Okay, so when was this project finally approved and what was the budget for it?
Gordon
The idea first occurred to me in the spring of 1958, the scattering from electrons, although terribly weak, was measurable with high technology, but more or less available equipment, leading up to the 1000 foot dish as an off the shelf item. By the middle of 1960, from Cornell there were five families who moved to Puerto Rico to seriously begin the construction. Two years and a couple of months later. Three years later, the facility was dedicated. It still needed a lot of tuning up, but it was up.
Sullivan
Up in 1963?
Gordon
Yes, November of 1963. And it's been going great ever since. With more money being poured in - a new surface, new meeting facilities.
Sullivan
What was the cost in 1960?
Gordon
Well, the delivered cost was something like $9 million in 1963.
Sullivan
And were there any difficulties or did it all go pretty smoothly?
Gordon
Oh, there were lots of difficulties. Looking back on them, they all sort of fell into place, but you never knew from one day to the next whether they were going to collapse on you.
Sullivan
Can you tell me what the major ones were?
Gordon
One of the major ones was our difficulties with managing a dozen subcontractors each with major contracts and were getting in each other’s way - trying to keep them from running up the bill. There were difficulties in, well, Sugar Grove was being turned off while we were building. That had some impact.
Sullivan
Maybe you were also a big white elephant?
Gordon
Of course, yeah. There were lots of people who said you couldn't build 1,000 foot dish to the specs that we were talking about. As it turned out, Cavanaugh and his designers produced a scheme for the surface which has just been repeated again in the new surface. The support if Cavanaugh's original technique - just used more often. Well, the problems did get solved. People like Merle [?] who was the chief engineer, a remarkable fellow, could get these people working together.
Sullivan
[?] was the chief engineer for the whole project?
Gordon
Yes.
Sullivan
I know him only recently from the [?].
Gordon
And unfortunately, he died recently. He's the one who built the feeds.
Sullivan
But did, were there any surprises in terms of the performance of either the surface or the line feeds?
Gordon
Oh, sure. The line feed didn't perform nearly as well as we'd hoped. The efficiency was 30-35% or something like that.
Sullivan
And you were shooting for...
Gordon
We were hoping for 60%.
Sullivan
I see. What was the cause of that?
Gordon
There was the difficulties were trying to feed the center of the dish for this long structure, and the structure was viewed as a wave guide, as a leaky wave guide, and in effect, it was an integrated structure which waves were not only traveling down the inside of the guide, but down the outside. They weren't being delivered to the center of the dish and if you put a big hole in the center then you are in trouble. That was improved enormously, of course, by Merle [?] by Allen Love who contributed a great deal to the second generation of use.
Sullivan
This took a couple of years to get straightened out then? After the '63 formal opening?
Gordon
Oh, yes, it was quite a few years. The new feed- five or six years.
Sullivan
Just one last question, during this period 1960-65, did the radio astronomy potentialities come to the fore anymore or did they still stay in third place?
Gordon
They were still pretty much in the background; I've forgotten at what stage Gold came to Cornell and he sort of spearheaded the radio astronomy side of it. If you know the dates, you can begin to see...
Sullivan
Yes, I've talked with him and I can't remember exactly the dates but he's told me his side of the story.
Gordon
We were in Puerto Rico, I was in Puerto Rico from 1960-65 and over my head were the first things to do and first thing after construction and the trying to get it all working.
Sullivan
Oh, one last thing I presume that the incoherent scatter worked out exactly as planned?
Gordon
No, it didn't.
Sullivan
No, it didn't, I see.
Gordon
The bandwidth turned out to be different than had been predicted, but that even made it more interesting. The levels were right, but the bandwidths were wrong.
Sullivan
You mean the cross section...
Gordon
The cross section was correct, and it had been done correct back by Thompson.
Sullivan
Okay, thank you very much. That ends the interview with Bill Gordon on 4 August ’78.