Massimo Stiavelli

Zeron:

This is Montserrat Zeron, and this is an interview with Dr. Massimo Stiavelli. Today’s date is June 10th, 2024. We are recording this in Dr. Stiavelli’s office at Johns Hopkins University. To start, if you could please state your title and your institutional affiliation.

Stiavelli:

I’m an astronomer at the Space Telescope Science Institute. Until April 30th, I was the mission head for the James Webb Space Telescope at the Space Telescope Science Institute. On May 1st, I started a one-year sabbatical, and that’s why I’m at Johns Hopkins now.

Zeron:

Now, I would like to take it back to the beginning. I know you were born in Montecatini in Italy in 1961, but I don’t know anything else about your family. Who were your parents? What do they do?

Stiavelli:

My father was working for the railway company. My mother was mostly staying home. For my little branch of the family, I’m a first-generation graduate. We moved a little bit around in Tuscany because that’s typical for railway company employees to be stationed in different places. I was all around Tuscany. Then I heard about Scuola Normale Superiore in Pisa. It’s an elite institution in Italy. That became my goal. After high school, I applied and was admitted there. Students at the Scuola Normale Superiore have to be also enrolled at the University of Pisa. You do all the classes at the University of Pisa, plus additional classes at the Scuola Normale, and so that’s what I did. After the laurea, which is the first level in Italy at the time, I also applied for a PhD at the Scuola Normale Superiore and was admitted to the PhD program. I was admitted to that and got my PhD there in ’86.

Zeron:

I wonder if you could take it back a little bit more. Do you know how your parents met?

Stiavelli:

They were both living in Montecatini. I’m not sure how.

Zeron:

Do you know what they studied in school?

Stiavelli:

As I said, they didn’t go to college, so they just did mandatory education. My father was interested in technical stuff, so he would do—since the internet didn’t exist, they had, I think it’s called correspondence classes, so they would get material by mail and so on. You learn things about technical topics that way while working.

Zeron:

Was there a library in your house when you were growing up?

Stiavelli:

Yes. They both liked books very much.

Zeron:

What kind of books did you read when you were young?

Stiavelli:

All kinds. I was mostly interested in technical stuff. We also had magazines like Atlante, which was very similar to the National Geographic magazine. You see a lot of nice places in the world. I like books, occasionally literature but more if it was technical.

Zeron:

I’m trying to sense when your interest in science started. Was that something that your parents influenced, or was that through books?

Stiavelli:

It was probably through books, just looking at what was available. I was naturally attracted toward technical things. I’m also the generation that was influenced by the Moon landing. I was 8 years old when Armstrong set foot on the Moon. I remember seeing it on the black and white TV, live. That was an impressive moment for a child. I thought maybe I could be an astronomer or work for NASA or both, as it turns out. [laugh]

Zeron:

[laugh] When you went to school, the mandatory studies, as you mentioned, do you remember any of your science courses?

Stiavelli:

Yeah. I remember of course also high school, before going to college, to high school. I had some teachers that were really encouraging, in pursuing my interest in physics, and giving me advice. My high school teacher for physics and mathematics was a physicist. I remember asking her, you know, I like mathematics a lot, so I said, “I don’t know if to do mathematics or physics. Maybe I could go into applied mathematics.” She says, “No. Applied mathematicians don’t know neither math nor physics. [laugh] Just go to physics.”

Zeron:

[laugh]

Stiavelli:

That was her biased view. My father-in-law was actually an applied mathematician, so I didn’t tell him this story. [laugh]

Zeron:

[laugh] Did you have any hobbies during those years?

Stiavelli:

I have the little things that nerdy kids have. I had a little microscope, the chemistry set, a little telescope, all that kind of stuff, the mineral collections.

Zeron:

That’s amazing. At this point, after you finished your high school, how did you discuss your college options? Was it with your parents, with your teachers?

Stiavelli:

Yeah. As I mentioned, with the physics teacher particularly, I was pretty determined. I looked at engineering. I was more interested in finding out how things work. I was less attracted to engineering. Plus, at least in Italy in those days, engineering required, you know, technical drawing was a big part of it, and I was not particularly interested in spending time on that. That’s why it pretty quickly ended up being a choice between math and physics. Then I ended up in physics. My father, of course, who, if his family had the opportunity, he would’ve liked to be an engineer, but he couldn’t afford it. When I told him I was going for physics, he said, “Ah, physics, the philosophy of engineering.” [laugh] But he didn’t put any pressure of any sort.

Zeron:

That’s nice. How did your parents finance your school? Was there a scholarship?

Stiavelli:

In Italy, university particularly then was a lot cheaper than here. Since I was admitted to the Scuola Normale, that was actually a full ride.

Zeron:

How did you choose this specific school?

Stiavelli:

It was in Pisa. I was living near Pisa at the time, so that’s probably one of the reasons I knew about it. It was the only place—it was the most prestigious place in Italy. It’s where Enrico Fermi started. That was the main driver. Of course, the fact that you would get room and board and tuition payment and so on was also a factor.

Zeron:

I know you said you had a little conflict between physics and mathematics. What pulled you more towards physics, and astronomy for that matter?

Stiavelli:

At the time, it wasn’t necessarily astronomy; it was more physics. But I was attracted to explaining the world, so theoretical physics was the thing that was attracting me. You use mathematics to explain the world, so that was my interest at the time. I started as a theorist.

Zeron:

Do you remember, when you first started at the Scuola Normale Superiore, any professors that had a particularly strong influence on you?

Stiavelli:

The quality the professors there was very high, uniformly. The classes were very small. That helps. It was very non-hierarchical. Of course, some were much older. But particularly with the younger assistant professors and so on, in a year or two, we became friends, playing pool together, this kind of stuff. It was a very nice environment. One professor that was particularly influential was a theoretical physicist. I took some classes from him in my freshman year. I like his style. In the junior year, there was a small thesis project I wanted to carry out, so I did it with him. I also selected him for the thesis at the end of the four years. He pushed me to work with another person, too, who then ended up being my primary advisor for my PhD thesis. But I really liked this guy and his approach. The principle of authority didn’t exist. I remember, one year, I had been to some conference. This is before dark energy was discovered. I said, “There are some people who are starting to doubt that the universe is cold dark matter, omega 1, which means, in those days, we thought that the universe was flat, and all there was essentially cold dark matter. There was a lot of cold dark matter. That’s what we mean, closure achieved by cold dark matter. I said, “There are some people that are starting to find results that say that omega 1 doesn’t look right.” He says, “Why don’t you come in the afternoon, and we talk about it? There is also someone else who was at the conference, and he believes in omega 1, so we could have a little debate.” I went back to his office. I think I was already graduated at the time, so I was a junior.

Zeron:

This is 18, 19 years old?

Stiavelli:

No. I was 23.

Zeron:

Oh, at college, yes.

Stiavelli:

The other person to have a debate was Jack Steinberger who was a Nobel Laureate in physics. [laugh]

Zeron:

[laugh] That’s amazing.

Stiavelli:

I was a little bit [laugh]—

Stiavelli:

But they were perfectly comfortable having a discussion as peers in a situation like that. Jack Steinberger was affiliated with the Scuola Normale. After he left, I think he was at Fermilab. Anyway, after he left the US, he moved to Pisa. It was a very positive, constructive environment. The downside was that he was very demanding, you know, long hours of study. The same professor that I said I liked, when people complained that they had 40 hours of classes and stuff, he said “Nights are very long.” [laugh] I remember, for one of the classes who joined after me, he gave a little speech, saying, “Winston Churchill promised blood, tears”—what is it?—“toil, blood, and tears.” Something like that.

Zeron:

Yeah.

Stiavelli:

Yeah. He’d say, “I hope there is no blood. [laugh]

Zeron:

[laugh]

Stiavelli:

But the other two—

Zeron:

Are necessary for success.

Stiavelli:

People were working, everybody was working very hard. But, beyond that, the atmosphere was very nice.

Zeron:

You mentioned the small environment. It’s more about the close relationship with professors. Do you remember other students, other peers that had any influence on you?

Stiavelli:

Oh yeah. We are still in contact with some of them. Many had pretty successful careers.

Zeron:

When do you think you started to get more interested in astronomy specifically?

Stiavelli:

The thesis at the end of the first four years, as I said, in Italy at the time, it was a two-step system. You have a kind of—you could call it a combined bachelor and master. [laugh] In order to complete that, you needed a research thesis, and then you could be admitted to graduate school for the PhD. The thesis at the end of the first part was already a pretty big job and intensive in terms of amount of work. During my junior year, I was starting to think about, you know, what do I really want to do? I had assumed I would go into particle physics, that type of theory.

I wasn’t enthusiastic about the directions that they were going into in those days. Supersymmetry, which was the idea developing in those years, didn’t appeal to me very much. I was looking around, and then I took a class on finite representation—sorry—representations of finite groups. This is a type of mathematics that theorists, in those days, particle physicists were using a lot. I realized that I didn’t have a natural intuitive comprehension of that type of math. For other things, I did, but not for the type of math that seemed to be essential for working in that field. Another student, a friend in those days was assuming he would go into astronomy, took the same class, and it clicked. We were talking to each other one day, and we said, “We could swap.” [laugh] We had always discussed the idea of not going into the same field, not to step on each other’s feet. We decided to swap, and I went into astronomy instead, and he went into particle physics.

Zeron:

That’s incredible. At this point, I know you still hadn’t gone to graduate school, but what was it about astronomy that caught your interest? Was it more research that attracted you, or being a teacher?

Stiavelli:

Research. I’ve had teaching experiences afterwards. I like teaching, but research was the driver, and I assumed that I would stay in research. [laugh]

Zeron:

After this, how did you select your PhD program?

Stiavelli:

The topic for my—let’s call it—undergraduate thesis, the laurea thesis, seemed to be promising. With my new advisor, we evaluated various options. But I pushed to keep working on that particular topic rather than starting something new. Essentially, there is a type of galaxies called elliptical galaxies. If you see the pictures, they tend to be more boring than the spiral galaxies that have those spiral-arms star formation. These are just balls of stars, essentially, with usually little gas. At least at the time, they thought that they had little gas. These are also the galaxies that tend to have supermassive black holes in their centers. At the time, we knew it for some, but that wasn’t known. I was interested in the structure of those objects and how they formed. That was the topic of my thesis.

Zeron:

How were you supported as a graduate student by the department? I assume, by that point, you knew some of the professors.

Stiavelli:

Again, it was the same institution, so I knew everybody. I always found the system very supportive. It was a different world. Among students, there was a little bit of what you would call hazing; not extreme. I don’t know if—friendly hazing. [laugh] But there was a little bit of that. But anything bad would not be tolerated. But as long as it was little pranks, or somebody gets a bucket of water in the summer [laugh], that was tolerated, more or less. I managed to be neither a perpetrator nor a victim too many times. [laugh] In fact, after I was pranked in this way, the older students said, “You reacted well. It’s no fun to do it.” They left me alone afterwards. [laugh] But with the professors, it was a very good relation. Keep in mind that in those days, this was a largely male business. In physics in my year, there were—in the previous and the following year, there were no women in it. It was small groups, like, in my year, there were 10 for physics, but all men. Things have changed now. I have visited that institute. [laugh]

Zeron:

[laugh] It’s different?

Stiavelli:

There is a lot more diversity. But, in those days, I don’t think there was necessarily any particular ill will by particularly the younger faculty. It’s a societal thing, because you needed to apply to that school, and many students across Italy didn’t even know it existed. Normally there would be some high school teachers somewhere that would advise somebody to apply. That’s why you say it’s a societal thing. If those high school teachers don’t recommend women to apply, women wouldn’t apply. If you don’t apply, it’s hard to get admitted. [laugh]

Zeron:

That’s very interesting. I know you mentioned your advisor, you said Professor Bertin?

Stiavelli:

He was my PhD thesis advisor, yes.

Zeron:

You mentioned your dissertation was on stellar dynamical models and statistical mechanics of elliptical galaxies.

Stiavelli:

Yes.

Zeron:

I know you’ve said a little bit about it, but could you go on?

Stiavelli:

This goes back to what I was saying. I was interested in these elliptical galaxies, how their structure worked, and how they formed. The structure is the stellar dynamics part of the title. An elliptical galaxy is the first order a collection of stars that is collision-less, so stars don’t feel each other’s gravity. They feel the mean gravity produced by all other stars. Their trajectories are not [bumping into each other]. Imagine the pictures that sometimes you see of atoms that are bumping into each other all the time. That’s a collisional system or a billiard or a pool table. [laugh] That’s a collisional system. Stars in elliptical galaxies, because their separation is very large, they essentially move on trajectories that are smooth, and they don’t feel too much the gravitation of an individual star. Occasionally it will happen, but mostly they move in the average gravitational field of the whole system. The field that studies this type of motion is called stellar dynamics. There are ways that you can build a model for an object that satisfies these characteristics. People look for distribution functions that’s essentially probability distributions to find the stars in a certain position and certain velocity. The name of the game was to find distribution functions that would describe elliptical galaxies as we see them, and also the associated gravitational potential because you want to make yourself a consistent model.

Of course, there are a lot of extra complications. The formation, we think, in order to get to an equilibrium that looks more or less the same for every galaxy, you need to have some kind of relaxation process that pushes you from the initial conditions when it forms toward something that looks similar. The idea for elliptical galaxies, the name of the process was a violent relaxation. [laugh] Essentially, I told you that those stars move under the mean field. They don’t feel each other directly, but they feel the mean gravitational field of the old system. During formation, the thought was that this mean gravitational field varies a lot, and that’s the violent part of the violent relaxation. These big fluctuations of the gravitational field will distribute stars into different orbits, and you get at the end to that. My interest was to people that started exploring this with numerical simulations. I did some numerical simulations myself, but I was interested in the statistical mechanics, so study the statistical processes that would lead to a certain configuration.

Zeron:

What was the influence of your thesis advisor? How did you come particularly to that interest? From a class?

Stiavelli:

Yeah, probably from a class. I was reading papers to follow up, and I found some papers that seemed interesting, and I did some calculations, and I discovered some results that seemed promising. That was my argument to do the thesis on that topic.

Zeron:

How long did it take you to do your thesis work?

Stiavelli:

The PhD?

Zeron:

Mm-hmm.

Stiavelli:

I started immediately when I was admit… I mean, we still had to do courses, but most of my time was devoted to the thesis, so three years.

Zeron:

Now this is 1987, and you’ve successfully defended your dissertation. What led you to enlist in the Italian army?

Stiavelli:

At the time, there was the draft, so I could choose to be drafted and do it as a soldier, or to enlist [laugh] and do it as an officer. As an officer, it would be longer by three months—three or five months, it depends on which—but after the first three or five months, you actually get paid [laugh], and you had a little bit more freedom, so I decided to go that route.

Zeron:

How long did you end up doing it?

Stiavelli:

Fifteen months.

Zeron:

What were your plans right after that?

Stiavelli:

I tried to continue keeping contact with the research world. It’s hard because you’re distracted by a lot of things, so I didn’t do much, despite trying. But after that, I had talked to some people that had seemed interested in hiring me, maybe as a postdoc first, and then with an entry-level position. Assistant professorships at the time were called ricercatore, researcher positions in Italy. The professors were the associate and the full, and the entry-level was the researcher in those days. The idea was I would do a postdoc, and then get one of these researcher positions. After I finished with the army, I contacted them, and this opportunity didn’t seem to be possible anymore. At the time, an English-American astronomer Linda Sparke was for a short period a postdoctoral fellow in Pisa. She said, “You need to find something, unexpectedly, and also a little bit out of phase. Why don’t you check people who have cited your work?” Essentially, today you would say “cold email” them. [laugh] That’s not the word we use. I don’t think it was in use at the time. Essentially, contact these people who I had met at conferences but didn’t know very well—but since they had cited my work—saying, “I actually don’t have a job,” and so on. I had also done other applications, but the first one would’ve started a year later, so I needed to cover a one-year period. One of the two that I contacted was interested, was really interested. That’s how I became a postdoctoral researcher at Rutgers University.

Zeron:

What was your experience as an international [postdoctoral] student there?

Stiavelli:

As a postdoc, it was interesting. Rutgers had a little booklet that many Americans found very annoying when they saw it. It was a booklet explaining American culture for non-Americans. [laugh] I was given a copy, and then I showed it to my friends. They were pretty annoyed [laugh] by how the university was describing American culture. But, aside from this, they had at least thought about it, and tried to explain the cultural differences that were and are pretty significant between Europe in general, or Italy, and the US. One of the things that was striking is that—and I saw an American woman living in France that was complaining about it on LinkedIn [laugh] about some of these things that she misses living in France. That’s the fact that in the US, it’s easy to become a friend with somebody. The bar for becoming friends is pretty low. There is maybe a level of trust, that is, people trust other people more. While in Europe, to become a friend, it tends to be you need to know people a little bit more. There is more of a barrier. But my Rutgers booklet was saying you find out that it’s easy to make friends, but a lot of those friendships are not a meaningful, serious, lifelong friendship [laugh], so a little bit more superficial friendship. Maybe there is a truth in that, too. All the people that were in my class in college, I’m in contact with many of them, and, in some cases, I haven’t talked to them in 15 years. It happened recently. I had a question about general relativity, and I remembered a guy in my class that went into general relativity. I hadn’t talked to him in probably at least 15 years, if not more. I found out his email address and emailed the guy. “Hey, how are you doing? Oh, by the way,” [laugh] and I asked my question. He immediately responded as if we had seen each other the previous day. That’s what I mean by deeper friendships that survive even if you hadn’t seen the person for a long time. Anyway, there are cultural differences. There is more food variety here, which can be interesting.

Zeron:

What was your focus as a doctoral student at Rutgers?

Stiavelli:

Not doctor; postdoc.

Zeron:

Postdoc, yes, I’m sorry. [laugh]

Stiavelli:

The professor who hired me there was particularly interested in a numerical code that I had access to, and he wanted to apply it to a problem he was interested in, so that was the focus. Since I would stay only a little less than a year, he was really interested in doing this particular project that had to do with the stability of certain models of galaxies. I was a hired gun. [laugh] I had the tool to solve his problem, and he had the problem. That’s where I spent most of the time. We ended up with a paper on that particular issue.

Zeron:

Then from Rutgers, how did you decide what you would do next?

Stiavelli:

When I went to Rutgers, I already had an offer from ESO, because I had applied, and I had gone on that ESO Fellowship. It’s another type of postdoctoral position. But the start would be many months later. I went to Rutgers for a certain time, and then I knew that I would end up at ESO afterwards.

Zeron:

Once you got to the European Southern Observatory, were there any particular specialties that were encouraged, or was there a specific focus there?

Stiavelli:

The European Southern Observatory is an observatory, so most of the astronomers there are observers, not theorists. I was one of the few theorists there. First of all, I got interested in observations a little bit because as a theorist, you often struggle understanding how much do you trust a certain result? What’s behind it, and so on? I started being involved in observational projects at the beginning as the theorist of the collaborations, but then more and more also on the observational side. I essentially broadened my interest while at ESO. I brought them both in terms of techniques, going into observations, and in terms of problems. I continued working on elliptical galaxies, but I started working on globular clusters, and other types of things.

Zeron:

I know the Hubble Space Telescope was launched in 1990, right?

Stiavelli:

Yes.

Zeron:

How were you interested in going into that kind of work at that point?

Stiavelli:

ESO was developing their own New Technology Telescope that was supposed to be with a very sharp vision for a ground-based telescope. There was less excitement than in the US. But then Hubble was launched, and it had spherical aberration, and so the Europeans kept mostly working on their ground-based data. At ESO, there was a little group, the Space Telescope-European Coordinating Facility, and it was a joint venture by the European Space Agency and the European Southern Observatory to support the Europeans working on Hubble. I had gotten myself into getting experience with a technique called deconvolution, which essentially was used to sharpen your data. I was using it for ground-based data to try to see what would I have seen if my telescope was, in effect, too sharper than it is? I was using those techniques. When the spherical aberrations on Hubble was discovered, those are exactly the same techniques that people were using on Hubble. One of the folks that was working at the European Coordinating Facility had time on Hubble, had data on Hubble, so asked me if I was interested in working with him, trying to recover those data. That’s how I started working on Hubble. This was the aberrated data, trying to derive signs from the aberrated Hubble data.

Zeron:

I understand that after ESO, you returned to your alma mater for a little bit. That was 1992?

Stiavelli:

Yeah.

Zeron:

What was your research focus then? What were you doing there? It was the same?

Stiavelli:

All of the above [laugh] because since I had brought into some observations, others, some theory. I was still working on the Hubble data. Black holes in galaxies had become popular, so I was working a little bit on that topic. I was trying to maintain all bases. At the time, I was assuming I would do the rest of my career in Italy. For instance, when I was there, I managed to obtain some internal funding to provide a camera for a telescope that a university in Italy had developed. It was a telescope for students training, mostly, so a relatively small telescope, 28 inches. We provided this camera to work with this telescope. I went there, trying to get it started, to commission the camera. But I thought we would go there with students and so on. But then things ended up developing in a different direction.

Zeron:

Were you teaching at the time?

Stiavelli:

Yes, cosmology or dynamics and these kind of things.

Zeron:

Now I’d like to focus on your career with the Space Telescope Science Institute. This is 1995.

Stiavelli:

Yeah.

Zeron:

What was your initial experience as a member of the European Space Agency personnel?

Stiavelli:

I can actually make a connection and tell you why I ended up here. I applied for an associate astronomer position, associate professor in astronomy in Italy. In Italy, they do these nationwide competitions, and then supposedly the best are selected. People can listen to interviews of the other guys. I remember I was pretty upbeat. I don’t suffer from imposter syndrome. Let’s put it that’s way. [laugh] I was pretty upbeat. Then I listened to some of the other guys and other people, and I thought, wow, these are good. These folks are good, too, so I may not win. I realized that I might not get it, and that’s fine. Somebody that could be better than you gets the job: that’s life. But then a person that, in my view, was much less qualified than me and another three or four guys got the job. That annoyed me [laugh] a lot. That’s why I decided to apply for a European Space Agency position [laugh], and I got that. I came to Baltimore in ’95.

Zeron:

That’s incredible. What was your initial experience here at a host location like STScI?

Stiavelli:

Oh, it’s great. I had been at the institute for a short visit in ’91, before spherical aberration was fixed, and the institute was not a great place. People were very tense, very worried. If it didn’t work, they would lose their job. It wasn’t a happy place. When I came here, oh, there is another thing that happened that convinced me to apply. In ’94, I came here for two months to work with a collaborator. Somebody who I knew from ESO obtained a job here with ESA. I was very impressed by the institute, the science atmosphere. There were a lot of young, great, young folks—very, very active. It was a great place to be. The advantage, the plus [laugh], how attractive the institute was convinced me to apply. I luckily got the job, and I arrived in ’95. It was a known quantity, the place, when I came a year later. It was great. It was the place to be, a lot of activity. You would get to see everybody in the astronomical community.

The colloquium season was very rich, so you would have all the famous astronomers passing by to give talks. It was a great place. When I arrived, it was just after the Hubble [Deep] Field had been done, because it was being prepared during my visit in ’94. When I came in ’95, it had been done. Of course, again, that changed astronomy because people didn’t know what to expect. There were papers predicting what it would see, and those papers were very wrong. [laugh] Whenever something like that happens, you have a lot of enthusiasm and eagerness to understand what’s actually going on. It was a great place. One of the things that happened a few months after I arrived, there was a conference on the Next Generation Space Telescope, because that effort had been started in ’89 with the conference here, because the then-director Riccardo Giacconi knew that it takes forever to do a flagship mission. He organized the conference about the successor of Hubble one year before Hubble was actually launched. But when Hubble was launched with spherical aberration, of course, it froze the enthusiasm for starting anything new. But after the repair mission, after Servicing Mission 1, and the Hubble Deep Field, everybody was ready for the Next Generation Space Telescope.

Zeron:

What was your impression of Riccardo Giacconi?

Stiavelli:

I knew him less. I didn’t know him as much at the time. He was this distant [laugh] figure. I only knew what people were saying about him. I got to know him better after he returned from ESO, and he was hanging around here for many years, and so I got to interact with him a lot more at that point. He’s an incredibly visionary person. I remember a talk he gave for the 15th anniversary of the Space Telescope [Institute], I think it was, and he said that he had created the institute in such a way that the institute would change the way astronomy was done, even if Hubble had exploded on the launchpad. He gave examples: creating pipeline software that automatically processes the data coming from the instrument so that even non-black-belt experts can use those data.

Nowadays every facility has a pipeline. In those days, they didn’t exist, archiving all the data, and making them public after a certain amount of time. The Guide Star Catalog, in order to guide Hubble, they scanned essentially on a computer-controlled scanner photographic plates of the whole sky in two colors. This became the digitized Guide Star Catalog that is used to point Hubble. Now the [HST] Guide Star Catalog is used by every telescope. A lot of things in astronomy—and he had another couple of examples [laugh] that I don’t remember—a lot of things in astronomy changed because of the things that they did in order to enable Hubble. He’s a very incredibly visionary guy.

Zeron:

Going back a little bit on your specific work on Hubble, I know you were instrument scientist and leader, the imaging branch lead. Could you tell me more about that?

Stiavelli:

I started out by being an instrument scientist on Wide Field Planetary Camera 2, which is the instrument that looks like the stealth bomber, where there is, like, one corner missing in one of the instruments. That redesign happened because they were working on that camera, but when spherical aberration was discovered, they decided to change the design to do the correction in the instrument itself, probably for cost saving. They ended up mixing the part that has higher resolution and the part that has low resolution into a single camera instead of having two different cameras. We get one detector from the high resolution, and three from the low resolution. I was instrument scientist for that. Always impressed by the level of knowledge about instrumentation and understanding of data that my colleagues had. Initially for me, particularly as a theorist that was doing some observation, there was a lot of learning involved. Then I became involved with the Advanced Camera for Surveys.

That was like the new camera that was coming, that was being built. I was part of that team before it was actually installed on Hubble. But before it was installed on Hubble, I had the chance to become involved with the Wide Field Camera 3, which is yet another camera but this time with also an infrared channel. I left the ACS team before ACS was actually installed on Hubble, to work on Wide Field Camera 3. Then, at some point, there was the opportunity of getting into management. Management was the last thing I was interested in doing. I didn’t like it. My attitude was, leave me alone. Let me do my job. [laugh] I didn’t want to manage. The division head at the time came to me to encourage me to apply. I said, “No way. Not interested.” Then he said, “You should think who you might end up working for [laugh] if you don’t apply.” He provided some hints. I said, “Oh boy,” [laugh] and I applied, and got the job myself.

Zeron:

Who was the branch lead at that point?

Stiavelli:

This was a new branch. It didn’t exist before.

Zeron:

I mean, sorry, the person that encouraged you to apply.

Stiavelli:

Oh, the division head was Chris Blades, who, by the way, had a similar career as me. He had arrived here with a European Space Agency, and then transitioned to the US side. A lot of people did that because as Hubble was approaching the 15 years, the end of the agreed life, ESA didn’t want to give people permanent positions for staying in Baltimore when Hubble might be terminated. They started giving only six-years-long contracts. That’s the one I had. At the end of the six years, you either have to go back to Europe or find another job. There are a lot of people even today at the institute that arrive at ESA, and then they transition to—AURA—to the US side for that reason.

Zeron:

You talked a little bit about the first time you heard about the Next Generation Space Telescope, and we know it had its early beginnings at the Space Telescope Institute. Do you remember anything else about the early developments?

Stiavelli:

Oh, yeah. I was super interested, for two reasons. First of all, the Hubble Deep Field was images. I wanted to know the properties of those objects. I wanted to take spectra. Even the large ground-based telescopes, like Keck, were struggling, and they will struggle even more with the Ultra Deep Field and other surveys. We needed something new. I was really interested scientifically in what a Next Generation Space Telescope could do, and I decided that it was worth investing a good chunk of my time.

There was, at the beginning, a volunteer science working group. I was part of that. I started working with the people at the institute that were working on it. Essentially, from then, I never stopped working on that telescope, initially for free [laugh], just out of my time. But then, at some point, I started working on it in a more official fashion. Some of the players at the time, like John Mather, he became the senior project scientist for JWST. But he had been contacted by the head of science at NASA, [Edward] Weiler, to start the effort to get NGST on the drawing board. There were also people here, like Pierre Bely, who was another ESA person who started working on a notional design for the telescope. He’s the person that came out with what is basically the design of JWST, the sunshield and the telescope on the other side open without—I got a chance to work with all these people from the beginning. I was young enough too, a lot of these early folks retired [laugh], like Pierre Bely. We are still in contact [laugh] with Pierre. Pete Stockman was another senior person from the institute, also retired.

Zeron:

Conceptualizing the Next Generation Space Telescope as a successor for Hubble, what was the reputation of Hubble at the time?

Stiavelli:

Post-repair, it was great. That’s what led to JWST—or NGST first, and then JWST after the name change—being what it is. The idea was, there isn’t much to gain by taking a picture in the visible, like Hubble does, so you want to go somewhere else. The places where you want to go is infrared. We are seeing galaxies that are so distant that they are redshift, the light is shifted toward the red and infrared more than we might have thought in the past, so we want an infrared telescope to study them, and we want a telescope that is able to take spectra. A spectrum is where you disperse the light in its constituent colors or wavelengths to see what it’s made of, what the object is made of. It’s like a sophisticated rainbow. [laugh]

The idea is that JWST would need to do spectroscopy, and so it needed to be cold in order to do infrared observations because something that is warm emits… Heat is detected as infrared radiation, so you don’t want the telescope to be blinded by its own temperature. It has to be large too, because once you do spectroscopy, and you split the light into many beams to see the wavelength, you need a lot of light to go in. It needed to be large, it needed to be cold, and so it needed to be shielded from heat sources like the Sun, the Earth, and the Moon. That more or less led to the design that we had.

Zeron:

What were some of the lessons learned from the development and the operation of the Hubble that you later applied to the Webb telescope?

Stiavelli:

I don’t know. Sometimes I wish we had learned more. Hubble was designed to be serviceable, so the instruments were easily swappable. The fact that an instrument is swappable and it could be serviced in orbit means that there was a simulator on the ground that you could insert your instrument and test it, and that each instrument could be tested separately from everything else. The instrument module for Webb is a single box, and if you had to swap out one of the instruments, it would’ve been very complicated. It would’ve been a hit on schedule, particularly depending on which one, because something goes in first. [laugh] If that’s the one that you need to change, you need to remove everything too. Luckily, we didn’t have that problem. But if we had had that problem, we sure would’ve wished to have a more modular set up.

Nothing happened that impacted us, but we were also a little bit lucky. A modular telescope, I think, would simplify… a modular instrument set would’ve simplified testing. It’s not obvious that it would’ve really cost more because a lot of the cost when you build these things is in the testing. It’s never the materials; it’s humans [laugh], the time of the engineers that work on it. The trajectory is different, and we thought the telescope could be very efficient because you can see the sky at all times, where Hubble every 96 minutes is eclipsed by the Earth for most observations, since it revolves around the Earth. Even that is true. On the other hand, there is a lot of housekeeping, maintenance that can happen while your object is occulted by the Earth, because the telescope doesn’t have anything better to do, so it can do some housekeeping things. While for us, for James Webb, everything needs to be accounted for because you don’t have free time for housekeeping. [laugh] If you need to do something, you’ll pay for it in terms of reduced efficiency. They’re very, very different. One lesson learned from Hubble is that Hubble has a fixed time schedule. At 9:00 I’m doing this, at 9:30 I’m doing this, at 10:05 this other thing, and so on. If one of these things doesn’t work for whatever reason—the guide star that helps you point fails the acquisition, so you cannot do that observation—Hubble sits for the whole duration of the observations until the next time starts. If you were to do a one-hour observation at a certain point, and for whatever reason that observation cannot happen, Hubble sits for an hour without doing anything until the next observation comes in. We decided, ah, we are smarter than that. We created the event-driven observation where every observation has a start time and an end time. They’re still scheduling the same way, but if one fails, you can slide the next one to fill in, so the telescope has no gaps.

Zeron:

You never waste time.

Stiavelli:

That was the idea that we had initially. What we hadn’t planned for is that exoplanets would become so hot. We have a lot of exoplanet science on JWST, which is very exciting. A lot of the exoplanet transits are observations that need to happen at exactly the specific time, because you don’t want to slide there because it needs to happen when you have the transit. You don’t want to get there before the transit. Those are now fixed-time observations, and they get in the way of this event-driven because you need special tricks to fill in the gaps. It’s not as easy as we had thought early on. We use the lessons learned but, in some cases—

Zeron:

You learn as you do?

Stiavelli:

Yeah. [laugh]

Zeron:

Do you know, how did NASA come to select the science working group members for JWST?

Stiavelli:

There were at least three science working groups selected by NASA. Early on—I don’t remember if it was ’96 or ’97—there was the ad-hoc science working group. These were the first. I was lucky to be selected for all three. The ad-hoc science working group was a group of astronomers that started guiding what this telescope science had to be, what observational capabilities it would have in a broad sense. Then this group was disbanded. But it turns out that NASA wasn’t ready yet to select the flight, and so they created the interim science working group who provided additional advice and provided comments on the calls for proposals. This is the group that really made the case that maybe we should have moving target capabilities. Initially, JWST didn’t have the ability to study solar system targets. This group pushed a lot to add moving targets, which means we can observe Neptune and other planets in the solar system, comets, etc.

The interim lasted only about a year. Then after that, there was this call which was more formal than the others. The others were what NASA calls the “Dear Colleague letter,” where they state that you can apply. The flight science working group was a real proposal because the US investigator was coming up with telescope time and money. This was a real proposal selection. I spent two months writing my proposal for that. [laugh] At the same time, they were selecting the prime contractor who would build the telescope, and the instrument teams that would be the instruments. When all these things were happening, we had the first flight science working group—just called SWG without the flight in front, but I’m using it to separate it from the others—in Baltimore, and so the teams building the instrument describe the basics of their instruments. Then there were presentations by Northrop Grumman, who was the prime contractor for the telescope. At the time it was Ball Aerospace who was building the mirror, essentially, and leading the development of the mirror.

Zeron:

Why do you think it was recommended that JWST be conceived as an international project?

Stiavelli:

I think for multiple reasons. A lot of people thought it was natural. Hubble was international, with the European participation. In the meantime, there had been other missions where the Canadians had provided components. There was a good relation, so the opportunity was offered to Canada to be a partner. Early at the time of the ASWG, the first science working group, one of the members was from Japan, because the idea is that Japan could also be a partner. But then the Japanese Space Agency was interested in another mission, and so they dropped out, which is sad to see them go. On the other hand, it made our telecons a lot easier because finding the time for a telecon that works in Japan, Europe, US wasn’t easy. [laugh]

Japan dropped, and we remained with the Europeans and the Canadians. So, custom is one. There was the realization that this would be a big thing, a major flagship observatory, so we wanted it to be open to the international community. It was going to be expensive, so even contributions from the partners are certainly welcome. Then the way things were going, the heavy-lift vehicles from the US—the Delta 4 Heavy and the Atlas 5 that had been considered—were lagging behind, where the Ariane 5 had launched with success, so the Ariane 5 became the natural choice for the launch vehicle.

Zeron:

In your experience as a member of the science working group, did that impact the collaboration between NASA, CSA, and ESA? The members of the working group, was there any sort of coordination between the international partners, or was that more of a headquarters effort?

Stiavelli:

There were little problems, but the personal relations within the science working group were great. It didn’t matter which flag one had. In fact, a member of the science working group moved from Canada to Europe, retaining his science working group affiliation. An international project of this nature has some difficulties due to US legislation, export regulation. There is in particular a set of rules called ITAR, International Traffic in Arms Regulations, and a chapter of that has to do with dual-use technologies having to do with spacecrafts and guidance and so on. Even things that had to do with JWST for many years were covered with ITAR. This means that the European partners or the Canadians could not get easy visibility in these things unless there was paperwork made. You’re required to get an export license. When the project became official, a lot was covered because the European Space Agency became a partner. Europeans working through the European Space Agency were covered by this interagency agreement. There was a lot of red tape involved to make sure that people could be told what they needed to know without violating any laws. We had to be constantly careful about this, and there were document repositories that had to be designed so as to preserve ITAR, and so on. It was a nuisance more than a big obstacle.

Zeron:

From your perspective, how different was that collaboration between Hubble and then moving on to JWST?

Stiavelli:

They were all great. I wasn’t really involved during the development of Hubble, so I cannot make the development comparison. But initially the European Space Agency staff at the institute working on James Webb were separated from the ones working on Hubble, because Hubble was an operational mission, and James Webb was a mission in development. Those are different organizational structures within ESA. But after the end of commissioning, after launch and commissioning, those two have merged. Now there is a single management structure on the European Space Agency side here for both missions.

Zeron:

I understand that you took a sabbatical year in 2007.

Stiavelli:

Yeah.

Zeron:

Could you talk a little bit more about that?

Stiavelli:

I was due [laugh] because every seven years, in principle, one is. The functional job I had was the imaging branch manager, and I didn’t think it was a very constructive job. I had the team leads, the leads of the various instrument teams, advanced camera, etc., that would lead the technical work for their instruments. I was there essentially transferring information from the people who did it to management. Once I said—I’m pretty proud of this—I said that my role was that of cholesterol, clogging the arteries of communication. [laugh] I always liked the technical angle more than pure management. In that role, I was isolated from the technical—relatively isolated, because there were 22 people I think in the branch. If you manage 22 people, it takes a lot of time.

On the one hand, the job I was doing wasn’t particularly interesting. I was due for a sabbatical. I had plans to do science. I thought [laugh], I’ll focus on science for a year, and I’ll see what happens afterwards. I went on sabbatical. I had the bad idea of writing a book, so I spent half of my time doing research, during the sabbatical, and half my time writing a book for graduate student level, for Wiley, From First Light to Reionization, so more or less the topics of JWST. That was interesting but very time-consuming, so I’m not sure it was a great idea. You’ve probably heard this, but there is some truth in it that when you teach something, it’s when you really learn it. [laugh] Writing a book is similar to teaching because you have to come up with cogent arguments and reasons for things. That was the thing. In the meantime, while I was on sabbatical, the person who led JWST at the institute, Pete Stockman, went into half-retirement, and they hired a new mission head, Kathy Flanagan, from outside. She was looking for a project scientist. That was in my desirability [laugh] as a job, and so I applied and got it, and became the project scientist in 2008, I think, at the end of [the sabbatical].

Zeron:

What was the shift in responsibilities from what you had before to now, being a project scientist?

Stiavelli:

A project scientist, in my opinion, was the best job you could have. During the interview, they asked me, “What do you see the role of the project scientist?” I said, “You can think of it in terms of Hegelian dialectic. You have the project manager, who is worried about money and schedule; the project scientist, who worries about doing the best science out of the telescope. The two talk to the mission head, who synthesizes the Hegelian part.” [laugh] I thought the project scientist was the best job I’ve ever had because you are free to think about science, just on science, how to do the best for the telescope.

Of course, you have to keep the community informed about the science that it will do. It’s not just science alone; it’s also communicating the science to the scientific community, and so on and so forth. But it was the most fulfilling job. When Kathy Flanagan became deputy director, she asked me to be acting mission head. Then I knew that there would be a search, and that created a lot of soul searching, because I was very happy with project scientist, but I was very, you know, part of my happiness, whether I was working for somebody like Kathy who created a system that people could thrive in. I went through essentially a similar thought process. Nobody pushed me to apply for mission head, but I went through the thought process. If I don’t apply, who I might end up working for? Hmm. [laugh] I will apply.

Zeron:

How is your relationship with the rest of the team?

Stiavelli:

My daily relations are with the mission office team, which is 10—sort of, you know, a varied size but of the order of 10 people. That’s great. We had a great relationship. We had people with always different personalities. I always had people where if they didn’t like something I was doing, would tell me. I like to receive feedback, because nobody is smarter than 10 people combined or 100 people combined, so you want to receive feedback. With a lot of these people, we remain friends. Some of them had great opportunities and left; one as a senior position at the Applied Physics Lab; one as a senior position at first Northrop, then Ball, now it’s called British, you know, Ball was acquired by… I’ve forgotten the name of the company. Anyway, it’s a European company. We are still friends even though we have lost contact, you know, daily contact. I think I had good relationships with everybody. There were about probably more than 300 people that were charging JWST or are still charging JWST probably. I looked at it some time ago, and it was 330 people, but not everybody full-time, so on the order of a little more than 300 full-time equivalent.

You don’t interact daily with everyone, but you try to go to meetings. Particularly during commissioning, it was a very intense period of six months, particularly at the beginning, very intense. I tried to be very visible and play my role. Once you do these kind of things, and you have operations, you have people that are in the control room for Christmas, New Year’s Eve. There is no holiday. I would try to go there, bring some chocolate, talk to them, at least provide support. I wasn’t the only one. I remember one day, it may have been Christmas maybe last year, that they told me, “We’ll get fat,” because apparently other managers had also visited them and brought them chocolate. [laugh] They had a lot of chocolate. I think it was a great team, and we worked very well together.

Zeron:

Like you said STScI had a thriving environment, and that impacted positively in the development.

Stiavelli:

Yeah. Also, when you are in a position of influence, you can do little tweaks to help people. I remember that my first day as mission head, we had a meeting of all the team leads. One of the things that is big when you are a project like this is requirements. You do the things to meet requirements. Somebody brought up requirements, and I said, “Remember the zero level requirements.” We have levels. Level one are the most important. Then level two are the ones that derive from level one and so on. It’s like a tree where we have more and more details. I said, “Remember the level zero requirement.” They looked at me [laugh] because there is no level zero. “Do the right thing.” [laugh] One of the project managers said, “I really didn’t like that you said that.” [laugh] “Do the right thing.” If you see that something would meet the requirement but doesn’t feel right—we were still years from launch—we have time to correct, so bring it up to management, either to your management or to us in the mission office, so that we can avoid…

Zeron:

A catastrophe.

Stiavelli:

…doing something wrong. Many people would visit me. Some called me. Others are very excited because [laugh] something wasn’t working. Over the years, people listen to that. Unfortunately, the way things are, you cannot always fix every problem, but at least you know what you’re getting into. Another thing that I’m pretty proud of that I did, we had an event where a mistake happened. It wasn’t anything irrecoverable, but we wasted a little bit of time. I was online, I wasn’t physically in the room, because of course we were doing commission during COVID, so we tried to minimize in-person presence. I heard this junior person saying—I don’t remember the exact words—“It was my fault.” I was very impressed, particularly for a junior person in a room full of people saying that. I wrote her an email, cc’ing her manager, saying, “I want to thank you [laugh] because everybody can make a mistake, but not everybody has what it takes to admit it publicly”.

Zeron:

Oh yeah, it takes a lot.

Stiavelli:

I try to nudge people, and recognize good work, and so on, which is almost impossible because, with an effort like this, the number of people that have done good work is so large, but at least I try to.

Zeron:

Now we’re getting closer to 2010. What was your perspective on the growing budget and schedule delays, concerns?

Stiavelli:

When the project started, and people were talking about half a billion dollars and so on, I don’t think anybody believed it. We all thought, “This is going to cost $3 billion, $3.5 billion.” A lot of people didn’t understand the complexity of what we had set out to do. While I think there may have been some gaming, getting from the half to the three and a half, going beyond that was partly just not full appreciation of the complexity of what you’re doing. I remember somebody saying, “If I buy a Toyota, I know exactly how much it’s going to cost.” I said, “Yes, because they build millions of them. If you were buying [laugh] the first prototype of a Toyota, they wouldn’t know the cost either.” Here we are building prototypes, so it’s very hard to assess the cost.

I think some of it was unavoidable. Some of it is probably due to the way funding works. If you realize that in a certain year you need $400 million, but the government budget only gives you $300 million, you have to move away $100 million worth of work. It’s not a mathematical rule, but experience shows that when you do that, it normally creates effects that cause you to increase the price by three times as much as you bought the first order. That $100 million dollars that you needed then would become $300 million in the total cost. We have suffered from that too. You may remember that there was a committee that looked at the price and looked at the project and came out with an estimate that it would take $6.5 billion to build a telescope. But the funding levels that they recommend were not provided right away. It took a year, and when we finally got the budget, it was $8 billion instead of $6.5 billion. Of course, they could have been wrong with the $6.5 billion, but certainly not increasing the funding level right away within a year also played a role. Then again, when you go from 8 to 10, there are human errors. There are a lot of things that can happen. One of the things that happened was that when you have something that is so challenging, everybody’s attention is on the challenging part. Everybody looks at the part that is the most difficult. Some of the problems happen in trivial things like the screws were not tight and right, or the thrusters that were cleaned with the wrong solvent. These are very basic mistakes. But management was all focused on the difficult things that nobody spent time looking at the easy ones, or at least maybe not enough people. The easy ones were the ones that created problems, and they produced further delays.

Zeron:

What was the general feeling at STScI leading up to and after the Committee on Science, Space, and Technology hearing at the House of Representatives in December of 2011?

Stiavelli:

People were worried because, I mean, this was following earlier. I think our budget had been zeroed out by the authorization committee. People get worried in those cases. I was confident we would survive, which is odd because, by nature, I’m a pessimist. But here I wasn’t because I thought we had a good story, with the support of the scientific community and the public, because even the public was starting to be aware about JWST.

Zeron:

Was that potential cancellation fear felt by the international partners?

Stiavelli:

Yeah. I believe there were pressures from the international partners not to cancel. I should say, Senator Mikulski being present in the Senate also was a major factor, because she has always supported science, she helped save Hubble, and she was able to construct bipartisan alliances to preserve the science. She was a powerful ally.

Zeron:

Did you experience anything else within the science working group or the scientific community itself in efforts to save JWST?

Stiavelli:

Some activities that happened before this time, NASA had asked us to look at the descope option, maybe a smaller mirror and removing the medium infrared instrument, one of the instruments. At the time when they asked to consider us, the savings would’ve been probably a lot less, you know, not very significant, and the loss of science opportunities would’ve been major. The science working group unanimously said, “No, the MIRI instrument cannot go.” We were less definite on the diameter of the mirror. Partly because of the segments, it wouldn’t make sense to descope the mirror. That was a theoretical opportunity, because if you started developing a different mirror, you would’ve spent more money, not less.

Zeron:

At this point, after the budget issue was reinstated, how much pressure was felt at STScI to get things done?

Stiavelli:

We were never on the critical path, so the mission schedule was never dependent. Never is a big word. But I cannot remember an instance where the mission schedule was dependent on something happening at STScI, so this makes you be a little more relaxed. You can focus on trying to do as best as you can with the resources you have. Of course, the delays give you an opportunity to do more, to do better, because if you have the staff ready to support commissioning, and there is a delay, you cannot fire people and then rehire them a year later. You need to keep the staff, the knowledgeable staff on board, and so you find useful things for them to do. The delays, in a way, helped us be more ready for launch and commission.

Zeron:

You mentioned you were the mission head for JWST at STScI. Could you talk about a little bit more of your day-to-day roles and occupation?

Stiavelli:

My plan was to set up a system where, in principle, I had nothing to do [laugh], so that I could focus on the fires. Whatever crisis happened, I would be able to deal with it. That was a good thing because there wasn’t a single day where I didn’t have anything to do [laugh] because there was always a small or big crisis of one type or another. You have the whole spectrum. Somebody finds a new way of doing something, and you have to understand, if we change the known road for a new one, are the benefits worth the risk? There were these type of decisions. There were decisions of problems because somebody, you know, we have to work closely with NASA, and not just one person but a bunch of people, and we have a lot of people on our side. Sometimes personalities clash.

You have to look at issues, and figure out, beyond the clash of personality, what is the thing that seems right, and try to be a little bit diplomatic, working with our partners at NASA but also sometimes Northrop Grumman and Ball. We all needed to work together, so it requires a lot of diplomacy, understanding various things. Then, of course, throughout the years, there are modifications, negotiations that have to take place. For many years, we had three meetings organized by the mission office. One was a 45-minute meeting where we would talk internally; then a one-hour meeting, which I tried to shrink to half an hour, with the team leads. The rule of that was that each lead was asked to say what’s their successes, what’s their failures, and what are the things that they think other people would need to know? One of the problems when you have so many groups working separately is that sometimes what one person does could impact another group, and they don’t want any disconnect. That was one of the things we did. Then we had a little half an hour science meeting also. Try to keep the number of meetings in the mission office to a minimum, but then, of course, we have a lot of meetings with other parts of the institute and NASA and so on and so forth. Go over everything, ranging from planning the next meeting at the American Astronomical Society, our presence there, to developments in the future.

Zeron:

What was your experience with the major software development at first once STScI was set up as the mission operations center?

Stiavelli:

When I arrived, some of the basic structures for development had already been put in place. We had a basic contract that wasn’t enough to cover all we needed to do, so we had to submit additional modifications. But we were working closely with the developers. We have a system at the institute that is called matrix management, where the mission office provides the priorities and access and interface with NASA, and then technical direction, but the choices of which staff does what resides in the division, and they also have a degree of freedom about technical solutions to adopt. Any metrics manager requires a lot of conversation, so that’s what the name of the game was.

Normally, I don’t think we have had a lot of issues on that side. Sure, sometimes we have had problems, like, we had to deliver a piece of software on our schedule that, in order to be tested, required another piece of software that we needed to get from Northrop, but we hadn’t gotten yet. You have these type of problems, because it’s not just us, it’s also the other partners. We would work, you know, common sense is the most powerful management tool. [laugh] Sticking to a schedule that doesn’t make sense is not helpful, so we would try to provide a margin where it was possible. In all this, the support from other people in the mission office was essential. My deputy David Hunter is the project manager and the deputy mission head. He’s a super-black-belt [laugh] project manager, and also a very steady personality. He doesn’t get excited easily, which to some extent is true also for me. He has been a partner for all these years, and he had been in that position even before, with the previous mission head. Other people, the project scientists, the mission scientists and so on, each of their areas of expertise, and so they are the first interface with different areas of the institute or the community and so on. But we tend to work together whenever there is an issue.

Zeron:

What was the impact of the COVID-19 pandemic on the last stages of development and operation?

Stiavelli:

It is different for different partners because they have different regulations, local regulations. Northrop was working in California. We are in Maryland. There are different rules. But it was major. We had plans for commissioning that had like 100 people in the mission operation center at all times, and we couldn’t do that. The institute management wanted to make sure that we enabled what had to be done with JWST, but at the same time we didn’t endanger people. During that time, I ended up also negotiating with my management of the institute [laugh] about what we could do, how many offices we could have, occupancy of those offices, how many people were really needed in the mission operations center. Work was done to restructure the air conditioning. It was modified to increase the air flow.

There were a lot of steps. A system was put in place to avoid the people who were COVID-positive who would come to the office, which poses its own threat. We wanted, by preference, to have people that were vaccinated. This all poses interesting issues because our HR can legitimately ask us whether we are vaccinated, but they have no authority to ask people who are Northrop employees or NASA employees and so on. They needed to talk to the HRs of these other organizations and find deals. Anyway, it worked out. In fact, in January, which is essentially a month after launch, we had the COVID peak of [the] Delta [variant], I think, you know, a lot of cases. We managed to keep the impact to a minimum. We expanded actually the footprint of the MOC [mission operation center] too, because most people were not coming to the office in those days, so there were offices available. We expanded the rooms where people doing commissioning could be, to a number of offices. This required adding another door that could be locked, and laying network because the computer network in the mission operations center is not the one of the institute, so doing real work in preparation for that. That allowed more social distancing for doing commissioning. That was also, I think, one of the ingredients. Everybody worked hard to make it possible. We had a bunch of rehearsals and exercises, LREs, launch rehearsal exercises. The first one was descoped, because this was the first one with COVID, so we didn’t want to be too ambitious. But then they started being more and more ambitious. The last exercises were interesting because there was a team managing the telescope. The observatory simulators would introduce problems, and these problems were not known to the crew that was actually operating the observatory doing the simulation. They see wrong telemetry, wrong signals, and they have to figure out what’s going wrong, and correct it, because the people who injected it…

Zeron:

That’s a great way to be prepared.

Stiavelli:

…keep it as a secret. Some of the anomalies that we encountered during the simulations are worse than anything we saw. [laugh] We had some other surprises, but the team was ready to deal with everything.

Zeron:

The James Webb Space Telescope was launched on Christmas Day of 2021. Could you walk me through your recollection of that day?

Stiavelli:

Normally, there would’ve been a VIP event, which was downsized because of COVID. The day for me was essentially modulated by both my role as mission head and by being one of those that had to be at the VIP event. Launch was, I think, at 7:30 in the morning, local time. I arrived at the institute at 5 a.m. to make sure we were prepared. Then we were in the big conference room—the auditorium—to watch launch on the big screen. I was watching that, and also watching on the phone for any email [laugh], anything happening. There were a few senior management from the partner companies. The deputy administrator from NASA was here. Then after that, I went to my office to check that everything was good. If you recall, for the first time, ESA—Ariane—put a camera on the upper stage, and so we saw the deployment of the solar panel, which was something that was not necessarily expected. Everything went very well with the launch. The conditions for deploying the solar panel had been a minute or two early compared to what we thought. We saw it deploying, which a good thing. But as soon as I could, I got to my office. I wanted to check that the [solar panel] not only was deployed but was working as intended. Then I came down for some interviews, and then I stayed around a little longer, checking telemetry from my office. Then I went home to sleep for a few hours because at 12-and-a-half hours after launch—so I think that’s eight o’clock, roughly—we were supposed to do MCC1a, which is a burn.

Ariane has done its job. But this time, the thrusters on James Webb itself would be turned on to inject us on the transfer orbit to L2. The 12-and-a-half hours is a magical time in the sense that—by the way, MCC means Mid-Course Correction—is a magical time because you cannot do it too early or you don’t know the position of the telescope well enough. As the telescope is flying, and as we talk to it, the telemetry from the ground station helps us refine the position so we can determine very well where it is so we can determine where it needs to go. If you wait too much, it will take more fuel to do it. You want to do it as soon as you can, not earlier, not later. If you delay by hours, it can cost you months of mission lifetime. I was there early. I think I came back at 5:00 to be ready for the MCC1a. It started on time, and it went well. At that point, I knew that we would have fuel for 20 years. NASA didn’t say for a month [laugh] because there were other burns that we had to do—minor. What’s the probability that we messed them up? Low. Even if you mess them up, what’s the impact? Low. I guess they wanted to be safe, and say it at the end. But because the launch data been very good for us, the Ariane had performed very well for us, and the MCC1a happened on time and exactly as we wanted, that told us that we had a lot of fuel left. I went to sleep [laugh] after a pretty long day, around midnight. [laugh]

Zeron:

Oh my god. [laugh]

Stiavelli:

The first few days were intense. We needed somebody from the mission office available at all times. In case we run into an anomaly, there is an anomaly management board that needs to review what it is and what to do about it. One person from the mission office is one of the mandatory seats in that board. We needed to have somebody available in case there was any anomaly. We had the rotation. We had a system to call our cell phones.

Zeron:

Be ready.

Stiavelli:

Yeah.

Zeron:

What was your reaction when you saw the first data from JWST come through?

Stiavelli:

Of course, it wasn’t just an event in July. I’d seen some data before. [laugh] The first thing that really made me pretty confident that this would be great is when the first images were taken to identify stars that would be used to then align the segments. When you do this, each segment acts as a separate telescope. Essentially, if you’re taking an image of one star, you would see 18 images or, in fact, you could see fewer if one of the segments is so tilted that its image falls off the field of the instrument. You would see some number of stars. The fact that all the segments were roughly where we expected them to be, and in relatively small areas, and searching for them wasn’t too complicated, gave confidence that the whole process, that the alignment that had been done on the ground was messed up, but not completely, on orbit. That’s the first thing. Then, while the telescope wasn’t aligned, all the segments were looking in different parts of the sky, we took a spectrum with NIRSpec, the European spectrograph, to see if there was any evidence of ice, because one of the things that are worries for space telescopes is ice. You can have water vapor that you carry up somewhere, or some of your hardware could release water vapor, and then water vapor looks at a cold surface, and it goes there, and forms a thin layer of ice. This is a problem with Euclid, the European mission, that they have a thin layer of ice. We spent a lot of time planning for avoiding this, with a very detailed cool-down plan. Essentially, the thing that you want the least to get ice on, you cool it down last [laugh] so that any water would freeze on other surfaces instead of the ones that you need. We took a spectrum to see if there was any ice.

This spectrum was of a non-aligned telescope, not in focus, and so on. We didn’t see ice, but there was a feature that we called a poly-aromatic hydrocarbon feature in the infrared at three microns from interstellar space. This is something that we know is there, but it had been with previous telescopes very hard to see. We took like a two-minute spectrum, just a random direction, and you see it. I remember the project scientist who was working with me, Klaus Pontoppidan—who is now at JPL—showed me this spectrum, and we were both impressed. Wow, this thing is going to work very well, because it was inconceivable. My expectations were very high because of this. Then I looked at some data to check that our pipeline wasn’t too bad, and so I could see things. [laugh] Then Klaus was one of those involved with the early release observations, and he led the data reduction of those. He was embedded in that process a lot more. I didn’t have a lot of visibility because we try to keep the teams minimal to avoid leaks. I didn’t have the need to know, so I only saw them a little earlier than the public. But it was certainly pretty impressive.

Zeron:

I wonder, given your experience with this project from the beginning, what can you say about the impact of having international partnerships on the success of really extremely complex scientific missions?

Stiavelli:

One of the things that is helpful is that you get to interact with a set of engineers that are used to work in different ways, so you get different perspectives. One of the dangers in developing something very complex is that you start believing your own propaganda. [laugh] The fact that you have an international partner that have their own competencies and their own views, and so on, can help keeping you better anchored to the ground. I’m not sure we had many examples where this played a major role on JWST, but in many small things, it played a role. Also, the instruments were also multi-international, like the detectors and this lead selection, the thing that decides which object you’re going to get a spectrum for. In NIRSpec, the European instrument, there is an instrument made in the US, so even the instruments themselves were all built in partnership.

Zeron:

Now, on its third year of operation, what can you say about what Webb has already achieved, and the potential for the future?

Stiavelli:

For exoplanets, which is not my science but it’s one of the things that I’m really interested in, the capabilities of Webb I think more or less kept the promise. The science that we wanted to do seems to be more challenging than some of us were thinking. The experts believe that, no, they always thought it would be challenging. [laugh] One of the problems is that Webb is really powerful to study the atmospheres of planets around red dwarfs, stars smaller than the Sun, and less luminous. These red dwarfs are more active than the Sun, so even though they are less luminous, they have more activity. A lot of this activity messes up the signature of the atmospheres we want to study. Whenever you see something, you don’t know if it’s really a molecule in the atmosphere of the planet, or is it the star that is doing something crazy. It requires some more sophisticated methods, and some of these are being proposed. There are groups that have in mind techniques to study, to correct, maybe monitoring multiple planets in a star system that has more than one. The community has made a recommendation to the institute director to look at a number of planets to see if there is thermal evidence for an atmosphere, because if measuring the composition of an atmosphere is more complicated than we thought, then maybe you don’t want to just go straight for that. First look at a bunch of planets to see which one has an atmosphere so that you can then look at the atmosphere of those that are confirmed. I called it thermal because if a planet has an atmosphere, as the phase that is illuminated by the star moves, if it’s without an atmosphere, it would cool down very fast. I’m oversimplifying. While if you have an atmosphere, it redistributes the heat, so the planet, when it’s no longer illuminated, will cool down slower.

This can be used to constrain the presence of atmospheres. Then once you know it has one, you can study it. I was more optimistic on that. I would’ve thought maybe we’ll get an exoplanet. The holy grail in that field would be to find a rocky world, a rocky exoplanet with an atmosphere, because a lot of atmospheres have been measured on gas giants, on larger planets. But a rocky world, like the Earth, with an atmosphere, we don’t know any outside the Solar System. Even if we looked at the Solar System from another star, using Webb, there are four rocky worlds: Mercury, Venus, the Earth, and Mars. Mercury has no atmosphere to speak of. It’s baked, so we wouldn’t see it. Venus has a very dense atmosphere—again, I’m not an expert—but some of our techniques require us to get a view close in in the atmosphere. Venus is very dense that maybe, in a transit study, we would see just haze. However, in that thermal study that I told you, we would see that there is lack, that there is a dense atmosphere. The Earth presumably we could detect if things are good. Mars is again iffy because it’s a thin atmosphere, so in the end, the product is small, so it may or may not. It’s not surprising, if you think about it in these terms, that we haven’t found one around another star, but I’d be surprised if it doesn’t happen. It’s just harder than we thought it would be.

Zeron:

Yeah, with time.

Stiavelli:

In terms of cosmology, distant galaxies, which is more my science, I wrote a paper in 1998, saying that NGST will be able to measure accurately metallicities of galaxies using a technique that is more precise. I was calling it in the paper “the fancy method,” maybe galaxies up to redshift 5. My excuse is that the highest-ratio galaxy known when I wrote that paper was a 5.3, so saying 5 was going pretty much to the edge of what was known at the time. The ERO [early release observation] that was released in July two years ago showed this line, and enabled the measurement of metallicity for a galaxy at redshift 8.5. [laugh] What I was hoping would be possible at 5 actually was done on the first trial [laugh] at 8.5. Now there are tens of galaxies where we are trying to do these measurements to determine the chemical composition of these galaxies.

There are some surprises because we thought that there would be—this is one of the papers that I gave you—that at some point, this type of redshift, you would see the metallicity, that mean, that the content and the chemical composition to approach the primordial one, to have fewer and fewer of the heavier elements, getting closer to just hydrogen and helium, which is what comes out essentially from the Big Bang. But, no, the galaxies we see, where we can do the measurements, have metallicities that are low but not super low; that are as low as some of the dwarf galaxies in our neighborhood, in our galactic neighborhood. That’s a little bit surprising. Then, of course, people made a lot of noise about galaxies seen in higher redshift than expected, and whether this breaks or doesn’t break cosmology, and so on. I think it’s earlier to make a statement on that. It’s probably likely that our models for galaxy formation need to be revised, but before throwing away cosmology, it’s a little bit early. Another area where I am hopeful that Webb will contribute is the area of the cosmological tension. You may have heard that people that are using the local distance scale to measure the expansion rate of the universe are finding a value that is in disagreement with those who use the cosmic microwave background as the basis. The difference is not huge, but the measurements today are accurate enough that it’s a significant, meaningful difference. Does it mean that there is something in cosmology we don’t understand, or is it something else? There is a technique that the group is using on Webb where they look at quasars that are lensed, and the lens is producing four images of the same quasar. These four images, because of the way the gravitational lens warp, have different paths. These paths have different lens.

But the quasars are not steady, they’re variable, so you can measure that, you know, image 1 is, I don’t know, a month ahead of image 2, and two months ahead of image 3, and so on. You measure that difference in time that one image is ahead because it has a shorter path, so we see it sooner. But we also have the paths, so by measuring—and it depends a little bit on the lens model—by measuring these delays, we can derive the cosmological parameters for just one source. If you have several, you reduce the error bars. This is a completely different way to measure the cosmological parameters from the other two methods. It suffers from different errors, and so it’s potentially very promising. So far, they fall more or less in the middle with an error bar that is compatible with both. But James Webb will be able to refine the model of the lens, and so that will shrink the error bar. Depending on where the measurement lands, we’ll know, we’ll understand, hopefully, where the tension originates. That’s a way where JWST could address the fundamental structure of the universe. There are other groups that are using Webb. This is a harder measurement to do. When you have these quasars, these lenses, the difference in flux from the various images is predictable by the model of the gravitational lens. But if you have a flux anomaly… so, if the flux is not what it should be, it may mean that there is a distribution of mass that we don’t see that is producing additional lensing. By doing the experiment very carefully and looking at certain bands so that you can restrict what’s affecting your measurement, you can in principle test whether dark matter is cold dark matter or is some other form of dark matter. We believe that most of the matter in the universe is dark matter, but we don’t know what it’s made of. Most people think it’s cold dark matter, which has a certain type of properties, but there are other, like, we think it could be a certain type of neutrinos. This experiment would confirm or rule out, potentially, whether it’s these neutrinos. It could investigate, it could help us investigate the nature of dark matter using Webb. This is an ongoing study. They published their first paper on the first set of observations. The potential of JWST is enormous.

Zeron:

Dr. Stiavelli, thank you so much for this very long session. [laugh] We will not release the tape or its transcript without your express approval, in terms of the forms that you will be receiving for this project. Thank you so much for your time.

Stiavelli:

Sure.