Giving the University of Arizona Mirror Lab a spin

Mat Kaplan: Crossing another item off my bucket list this week on Planetary Radio. Welcome. I'm Mat Kaplan of The Planetary Society with more of the human adventure across our solar system and beyond. Come with me deep below the University of Arizona's football stadium for a tour of the Caris Mirror Lab where tons of molten glass are spun and polished to become the primary mirrors for several of our world's largest telescopes. Our guide will be astronomer Buell Januzzi, head of UA's Department of Astronomy and the Steward Observatory. Sarah Al-Ahmed will stop by to help deliver a sampling of holiday gifts that any true space geek will go gaga over, and I'll have a gift for the winner of the new space trivia contest in this week's What's Up segment. We warned you, and it happened just as expected on or about November 17th. After three and a half years orbiting our planet, The Planetary Society's Light Sail 2 ended its mission in a fireball somewhere over Earth. We proved that a solar sail could be successfully deployed from a tiny cube sat and that it could maintain its orbit by turning to face the sun and then turn away from it on every one of approximately 18,000 orbits. Hats off to the entire Light Sail team and to the 50,000 society members and donors who made this triumph possible. Light Sail Program Manager, Bruce Betts, will have more to say when we reach What's Up? You can read more in the November 18 edition of The Downlink, our free weekly newsletter. You'll find it at planetary.org/downlink. Check out the gorgeous image of the Gulf of Aden with our sail above it. Let's see. What else? Oh, Artemis 1 launched successfully and spectacularly. It has already made its first pass by the moon. All is well on the uncrewed Orion spacecraft, but some of the cube sets carried by the Space Launch System rocket have not been heard from, as I speak. They include the Near-Earth Asteroid or NEA Scout Solar Sail. There's more, including the announcement of Canada's first lunar rover. The mission will be a collaboration with NASA. It's expected to launch as early as 2026. You have till November 30 to help us select winners of The Planetary Society's Best of 2022 Awards. Your ballot awaits at planetary.org/bestof2022. Sarah Al-Ahmed is The Planetary Society's Digital Community Manager. She's also barely a month away from becoming the host of this show. Happy holidays, Sarah. A little bit early, but not too early for The Planetary Society Gift Guide, which you, and I, and a lot of our colleagues have contributed to. I want to hear about some of the things that you had in mind, and then I'll share some of mine. You go first.

Sarah Al-Ahmed: Yeah. Well, anybody who knows me knows that I love to wear things that show off my love for space. It's a great conversation starter moment. So, as soon as those new James Webb Space Telescope images came out, my first thought was, "I need that Carina Nebula on a dress." Thankfully, the people at STARtorialist totally came up to bat for that and put out a wonderful Carina Nebula skater dress, which I bought and I wear all the time. So I had to add that one to the list.

Mat Kaplan: That is great, and that is so in the tradition of our former colleague and my good friend, Emily Lakdawalla, who is just like you that way. Okay. My first one. No surprise to a lot of people out there. It's The Moons Symphony. Amanda Lee Falkenberg, that terrific composer. I got, what? Three shows now out of this symphony leading up to it with the recording that was done just on synth, but then on my live show in London and that amazing recording session for the London Symphony Orchestra, and it's just great. I just love listening to it. You would think that I got paid for this. I did not. I just love it, love it, love it. Seven movements, each inspired by a different moon from Signum Classics. It's out there, and we have it in the guide. All right. Sarah, your turn.

Sarah Al-Ahmed: Well, another thing I really love giving to people, especially the younger people in my life or people that just need something to hug, are the Celestial Buddy plushies. They're these beautiful little plushies. You've got ones from all the different bodies in the solar system. So I personally want to collect all of them, but I can't, but you can get at least one for someone you love. So I threw that one up on the list.

Mat Kaplan: I like the Mars I have sitting behind me right now. Cosmos, not the Sagan Cosmos. A book that came out much more recently by the amazing Jay Pasachoff, a man who we have talked to on the show many times because eclipses chase him. He's not an eclipse chaser, and Roberta J. M. Olson, art historian. Jay, terrific astronomer. This is a beautiful coffee table book. It is at that intersection of art and science that I love so much, and I know you do, Sarah. In fact, the subtitle of the book, it's Cosmos: The Art and Science of the Universe, and it's the kind of book you can and will, if you're a space geek, just spend hours paging through, and the text is brilliant as well. Cosmos: The Art and Science of the Universe. Your turn.

Sarah Al-Ahmed: Yeah, something that blew my mind. I went to go visit my brother recently, and he's trying to deck out his place at home with some more beautiful lights since he's been shut inside by himself during this COVID era. So, to beautify his space, he got a Sega Homestar Planetarium. Now, I am very jealous because this thing projects beautiful images up on the ceiling. Just the quality of the stars, it's beautiful, and every time I go to his house, I have to turn it on and just lay back and feel like I'm looking up at the sky just because living in Los Angeles, there's a lot of light pollution. I miss the Milky Way. So that one is a little bit more on the pricier side, but if you want to fill your home with beautiful star light, I highly recommend the Sega Homestar Planetarium.

Mat Kaplan: That may be one that I will go for because I have wanted a home planetarium ever since I was a little kid. There was one that they sold at the Museum of Science and Industry in LA, and my parents would not loan me the money to buy it. I've never forgiven them. So, now, maybe I can make up for it. Okay. Here's my big close. It's not new. It's our friend, Andy Weir, Project Hail Mary. What an amazing book as I've said many times. I think every page has, A, a good laugh and B, a brilliant innovation from that amazing mind of Andy Weir, and Andy will be back on the show very soon with another amazing mind, Rob Manning, the Chief Engineer at JPL, the Jet Propulsion Lab. Have you read the book, Sarah?

Sarah Al-Ahmed: Yes. I had to after I heard the interview between you and Andy Weir on Planetary Radio. I know it did give away a lot of it, but just what a clever book.

Mat Kaplan: Yeah, yeah.

Sarah Al-Ahmed: Loved it.

Mat Kaplan: Well, that's our list, but there are so many more items for you to check out. They're all at planetary.org. You can get there right from that homepage. Have fun, and Sarah, like I said, happy holidays. Hope you get lots of great presents.

Sarah Al-Ahmed: You too, Mat.

Mat Kaplan: Many of you will remember that I was in Tucson, Arizona last September for the NASA Innovative Advanced Concept Symposium. The visit also gave me the opportunity to meet the leaders of the Catalina Sky Survey and Spacewatch. Both of these successful surveys are run out of the University of Arizona's Lunar and Planetary Lab. Next door to LPL is the Department of Astronomy that also runs the Steward Observatory and the Richard T. Caris Mirror Lab. All three of these are directed by astronomer Buell Januzzi. Buell and I met very early at the university's football stadium on the last day of my trip to fulfill a dream I've nurtured for a long time. Buell, as I was just telling you, this is a dream come true. I've been looking forward to visiting the Mirror Lab for at least 12 years now when we started to report on the Giant Magellan Telescope, so it is an honor and a pleasure to be here. Thanks for hosting us.

Buell Januzzi: You're very welcome, and it's great to be able to share what we're doing with you and with your audience.

Mat Kaplan: So where are we headed?

Buell Januzzi: We're heading into the oldest part of the Richard F. Caris Mirror Lab. It's where we cast the mirrors. So you're going to get to see the spinning oven. It's not spinning at the moment, but it's the oven that's capable of spinning that is a unique aspect of how we make mirrors.

Mat Kaplan: I encourage everyone who may be listening as we head down here to go to the Mirror Lab site. You can check out a terrific video that shows you, thank you, as we go through a door, the entire process. Wow. You could probably tell now that we are in a big room, and what is this that we're standing in front of?

Buell Januzzi: So what you're looking at right now is a giant turntable that's capable of rotating an 8.4 meter mirror and its mold. If you look up to your right, you can see a large crane that is capable of lifting the lid of the oven and placing it in place after the mold has been constructed, and the glass loaded, and everything is ready to fire the next casting.

Mat Kaplan: I got to think that pretty much all of the hardware that we see in front of us here and in the rest of this huge lab is custom. This is not stuff that's off the shelf.

Buell Januzzi: No, this is not off the shelf. Roger Angel envisioned how to make these mirrors over a period of 10 years. The Mirror Lab has been in existence for about 40. It's the product of the students, and staff, and faculty of Steward Observatory and the College of Optical Sciences working together to do something that hasn't been done before, which is make large optics that are 80% hollow that enable us to then use really giant telescopes to learn about the universe.

Mat Kaplan: So, I'm a big fan, well, of telescopes first, but I love going to Palomar, Mount Palomar to see the Hale Telescope. It's a shrine to me, and I even have a t-shirt that has the pattern, the honeycomb pattern of that mirror on the back of the t-shirt. So, a similar construction where a lot of the glass is gone. It makes it a lot lighter, but that was ridiculously difficult to put together. They did not have the advantages of the sorts of technology and this basic technique that you have here.

Buell Januzzi: That's right. That's a lighter weighted mirror compared to mirrors of its day, but ours are much more lightweight or hollow. That's largely because the casting method includes taking up space with mold material. It later gets removed, washed out. So, Roger and his colleagues could minimize as much as possible how much glass goes into to this mirror. Now, this is not the only way that you can make a giant telescope. There are at least three different techniques, or technologies, or design, fabrication paths you can go down for making really giant mirrors, and each of them have advantages and disadvantages. One of the advantages of our mirrors is that once you actually get the surface to the accuracy that you want and you put in a relatively straightforward support system, you don't have to worry about whether or not you're going to be able to maintain your image quality. For the Giant Magellan Telescope, which requires seven of these 8.4 meter mirrors all phased together, which we know how to do now, it means that we only have to change out a mirror for recoding on a much more leisurely time scale than some of the telescopes that are using thousands of segments. But the thousands of segments have the advantage that if you break one, it's a very tiny fraction of your telescope. We have to make sure that that does not happen.

Mat Kaplan: I would also think and I have read that with telescopes like the TMT, the 30-meter telescope, one of those with thousands of segments, that each of those has to have a little mechanical actuator behind it, right, that has to react very quickly.

Buell Januzzi: They don't have to react that quickly. All of the primary mirrors, whether it's a thousand segments or seven, the time scale that we are adjusting the primaries is slow compared to what we do with other optical elements farther down the chain. So, for example, the University of Arizona pioneered what are called adaptive secondary mirrors. So the light comes from a distant star or galaxy, hits the primary or first reflective surface of the telescope, focuses the light, and you introduce a mirror that you can change its shape a thousand times a second. It's only a few millimeters in thickness, and that allows you to start correcting the wavefront right away with a minimum number of elements. The reason you want to minimize the number of elements is, especially when you're going into the thermal infrared, the more elements you have that aren't cooled, the greater the background is going to be in your measurement. If you're going to look for extrasolar planets near bright stars, you want to have the diffraction limit. We can reach that now from the ground thanks to adaptive optics because what we all want to do is go look for signs of life on exoplanets.

Mat Kaplan: Anyhow, you can say that again.

Buell Januzzi: Yeah.

Mat Kaplan: Adaptive optics have been a revolution maybe as big as using CCDs and getting away from old glass plates?

Buell Januzzi: Oh, that's a hard question. Which is much is more important, CCDs or adaptive mirrors? So, adaptive optics. I guess compared to the average person, I'm an expert on adaptive optics, but I'm not the right person to talk to about the history, but it goes way back. Certainly, Freeman Dyson had a lot of the early ideas, went into non-astronomy world, and then the government released what they developed, and a lot of pioneers, including people like Claire Max at UC, but also people here at University of Arizona and other institutions have developed it further. I think the unique contribution that we made here at the University of Arizona was trying to start having the adaptive element be as early in the optical train as possible with the adaptive secondaries. So, along with our colleagues at Arcetri in Italy, the MMT, the Multiple Mirror Telescope, which is misnamed at some level because it's now one big 6.5-meter mirror made from the Mirror Lab, had the first adaptive secondary. The CCD, I think I'm going to have to give the nod to barely.

Mat Kaplan: I'm not surprised.

Buell Januzzi: But the diffraction limit, the ability to have these giant telescopes to the diffraction limit depends on the adaptive of optics. If we didn't have it, we probably wouldn't be trying to build these giant telescopes because they still would do wonderful science, but there are other ways of collecting a lot of light. Roger Angel, for example, is working on an idea of using thousands of small telescopes, all fiber, feeding a spectrograph with a fiber in order to do a lot of interesting spectroscopy that the giant telescopes are also going to do, but Roger's idea will cost a lot less. His idea would not allow you to image an exoplanet next to a star because you're not creating an aperture that's phased that has the diameter of the giant telescopes. You're just duplicating the collecting power of collecting a lot of light.

Mat Kaplan: I did not know that Freeman Dyson had a role in the development of adaptive optics. He was a guest of mine a couple of times, and I would've asked him about that. You also mentioned though this other pioneer, Roger Angel, who was behind the lab and I guess was the first to develop this idea of spinning molten glass and letting centrifugal force do a lot of the work for you.

Buell Januzzi: I'm not going to say with absolute certainty that nobody else ever tried spinning glass because people also have had ideas of spinning mercury to make a mirror. Roger certainly and his colleagues were the first people to envision this complete fabrication method. It was inspired by the original MMT. So the original MMT used six mirrors that were originally intended for the Air Force's Manned Space Lab. Are you familiar with that?

Mat Kaplan: I am. The one that was going to be... They didn't talk about it much at the time, but the one that was going to be, basically, a military space station.

Buell Januzzi: That's right.

Mat Kaplan: Then, they realized, "We don't need people up there, we can do it with robots."

Buell Januzzi: That's right, or satellites, and so the...

Mat Kaplan: That is what I meant. You just automate it.

Buell Januzzi: That's right. So this is where the connection to the University of Arizona gets strong is one of the fathers of space telescopes, Nancy Roman, Lyman Spitzer, all those people deserve all the credit they get for the Hubble Space Telescope, but a less well-known story is the role that Aden Meinel played in the development of all of our space capabilities and our ground-based telescopes. Aden Meinel was the first director of Kitt Peak National Observatory, and the first technical publication of Kitt Peak was concept for a space telescope, and this was in 1958. He worked out how you're going to have to do the remote control and lots of other challenges of doing a space telescope. He was also heavily involved in working with the government on developing reconnaissance satellites, and so at some level, he had a role in helping to make the Manned Space Lab not necessary because one of the things that that was going to do was use telescopes to look down, and the astronauts, the Air Force astronauts were going to take photographs. Well, when that got canceled, there had already been made mirrors, 72 inches in diameter, and Aden was able to convince the government to give them to the University of Arizona and the Smithsonian Astrophysical Observatory to build a ground-based telescope with effective aperture of around 4.5 meters in collecting area. Six mirrors, all working together on a common mount. When that telescope first came online, and the construction of that telescope was led by a bunch of people. I forget somebody, but Nick Wolf, Nat Carlton, Bill Hoffman. When that telescope first came online, it was making sharper images than comparable telescopes of the day, and they quickly realized it was because the mirrors were coming into thermal equilibrium to the same temperature as the surrounding air more quickly than most mirrors, even the Palomar 5 meter. That was because the mirrors had been lightweighted too because the dominant cost of going into space is lifting things off the earth.

Mat Kaplan: Yeah, yeah.

Buell Januzzi: So these mirrors that Aden had obtained were lightweighted because they were supposed to go into space, and now they weren't. Roger quickly realized, "Well, okay. It'd be wonderful to make mirrors that are bigger than this," and he went to industry, and industry listened to what he was suggesting, and they said, "No, this is not possible." So that's what set Roger off on trying to develop the techniques. You asked or said earlier, "Is everything here custom?" Almost everything in the lab is custom. The real genius of what Roger did was to think very deeply and carefully about every simple step that you're going through and extracting the important meaning of how to do it right, but there are other people like John Hill, Peter Strittmatter, Buddy Martin who've played major roles in the early days of the lab, and almost everybody is still connected here in one way or another. Although I sometimes say that building GMT is a little bit like modern cathedral building because those of us that are working to build it aren't going to get to use it for very long, so.

Mat Kaplan: It sounds like sending missions to the outer solar system. Yeah.

Buell Januzzi: Yeah, that would be another one, except I think we'll at least know whether it's all working.

Mat Kaplan: Yeah.

Buell Januzzi: So.

Mat Kaplan: So Roger is still active obviously as well from what you've said.

Buell Januzzi: Yeah. Roger is not retired yet. He's still working on new concepts for telescopes. I was talking to him yesterday. He's working on a paper for a conference that's coming up on science from the Moon, so.

Mat Kaplan: I heard just before we started to talk, you and I, that you've got someone here who started as a student and is now getting ready to retire. Really, has made a career at the Mirror Lab.

Buell Januzzi: Sure. I don't know who Stewart was thinking of. We actually have several people, but I suspect he's thinking about Karen Kenagy. Karen was a student here at the U of A, has had her whole career here. A lot of the people that work at the Mirror Lab came here from very diverse backgrounds, our students, or the military, or engineering, or you name it, but they have to be inquisitive, they have to be good at working as part of a team, and they have to not be intimidated about trying to do something that hasn't been done before, and they also need to be very patient. We are not a short-order cook in a fast-food restaurant. The casting process takes a year to 14 months, whether it's a 6.5-meter or an 8.4-meter, and those are the two sizes we do right now. Then, the polishing, it's going to take, right now, although we're working to speed this up, it takes two to four years to complete the polishing.

Mat Kaplan: I'm going to recommend, again, that people watch the video on the Mirror Lab website because it will show you just how complex this process is. I mean, there may be people who think this is, "Oh, what's the big deal? You melt some glass and spin it, and then you grind it down for a little bit longer." It's far more than that. In fact, watching that video and then being in this huge facility reminded me of when I went to visit the JWST, the James Webb Space Telescope, and watching that and how it was being worked on it, it's that level of complexity and detail.

Buell Januzzi: Yes. I mean, I think most of the mirrors that we're making here, we do have the luxury that we're not launching them into space. Although we are now starting to work... Well, for about a decade, we've been working on concepts for premiers for large space telescopes. One of the things you saw for James Webb is that they had to fit inside a fairing or a housing for the whole spacecraft that was smaller in diameter than the diameter of their primary mirror, but there's a new generation of large rockets coming, you know some of them already, that have much larger fairings. So it is and much more ability to lift a lot of weight. So we can now start making mirrors the way we make mirrors or meniscus mirrors, which is the third. The three types of making mirrors: meniscus, array, and segments, small segments. Small segments worked for James Webb spectacularly as we all know, but there is a different set of risks with that kind of telescope and a lot of testing required on the ground. So we're exploring using our mirrors as a possible lower cost way of doing space telescopes, but here, you can see the most recent mirror that we've cast. It's for a wide-field spectroscopic survey telescope. So that hole in the mirror is the largest hole we've ever had in one of our mirrors, and you're looking at the backside that's in the turning ring. So this mirror has had all the mold material washed out of it. Unfortunately, we have a queue. Fortunately, for us, there's a lot of desire for these mirrors. But unfortunately, for this mirror, it's going to have to wait probably about a year and a half before we can even get started on polishing it.

Mat Kaplan: I suppose that's a good problem to have. A lot of work.

Buell Januzzi: It's a good problem for us, but not a good problem for the people that want the mirror as fast as they can get it so they can make their telescope.

Mat Kaplan: Is this the 6.5-meter that you were talking...

Buell Januzzi: This is a 6.5-meter telescope.

Mat Kaplan: Where is this going?

Buell Januzzi: The people that are building that are still trying to decide, so I can't tell you yet, but what I can tell you is that it's going to be a spectroscopic survey telescope. The dominant cost for ground-based telescopes, unfortunately, is the building, not the telescope. So the bigger the telescope gets, the building goes up, and it goes roughly as the 2.5 power of the diameter, the primary mirror. So the 30-meter that they're trying to build or the 25-meter that we're building, those are billion-plus projects. A 6.5-meter can be built for around $70 to $80 million. Still a lot of money, but is much more realisable for a university or a small group of universities to raise on their own. Whereas the billion-plus projects require involvement of governments and many institutions.

Mat Kaplan: Now, this is huge, 6.5 meters. That much larger for the GMT mirrors.

Buell Januzzi: Right.

Mat Kaplan: Just amazing to see.

Buell Januzzi: This mirror is not that much smaller, although it is smaller than a single segment for the GMT, but the GMT will have seven of them. So as we continue to go through the lab, the casting hall that we're in right now can barely fit three of these mirrors in a line, and you're going to see that in the integration hall too. Then, imagine how big the building has to be to hold seven.

Mat Kaplan: Lead on because I know your time is limited. There's so much more to see here. We're going down a little spiral staircase now. Okay, deeper into the bowels of the Mirror Lab here, and here is a work area with lots of benches and equipment. Oh, we're under the turntable now?

Buell Januzzi: That's right. We're under the turntable. What you're looking at, it looks like a merry-go-round, and if they look at the mirror at the movie, I think there's a picture that shows the bottom. This is not the very first oven, but it is... This oven has been used for the majority of the large 8.4-meter mirrors, all the 8.4-meter mirrors that we've cast. The information that all the sensors and computers on here get, all the temperatures, then get sent to a control room that's over there on the left. During the initial high-temp casting and then cooling for three months, everything is being monitored 24/7. We have backup power. It's all to make sure that the glass anneals without having any stress left in the blank.

Mat Kaplan: Three degrees centigrade per day for cooling for how long?

Buell Januzzi: About three months.

Mat Kaplan: Wow.

Buell Januzzi: Yeah.

Mat Kaplan: An enormous amount of power. Oh my god. All right. Another huge room, and we haven't said yet where we are, the location on this campus.

Buell Januzzi: Yeah. So we're underneath the east stands portion of the U of A football stadium. This football stadium has been here since the 1930s. Brian Schmidt, who was an undergraduate here and went on to win a Nobel Prize in 2011 for discovering that the expansion of the universe is accelerating along with his colleagues and a competing team, actually had his freshman dorm room was inside the stadium here.

Mat Kaplan: Wow.

Buell Januzzi: On the southern edge there, their dorms. People ask, "Why are you underneath the football stadium? Is it because Chicago did astronomy in their football stadium?" No, or physics in their football stadium.

Mat Kaplan: First fission reaction, right?

Buell Januzzi: That's right. So there is a positive relationship between football and innovative science, but the reason we're here is because it's close to the Astronomy Department and Optical Sciences, and there were big pillars of concrete that you could attach walls to and cranes. So, it's that simple.

Mat Kaplan: Everything in here is incredibly heavy-duty. I mean, we'll put some pictures on this week's episode page at planetary.org/radio so that you can get a feel for it, but I suspect it's a little like the Grand Canyon. If you're not standing here, you're not really going to get the scale of it.

Buell Januzzi: Yeah. That's a nice analogy. I might use that sometime.

Mat Kaplan: Yeah, feel free.

Buell Januzzi: Yeah. You're up close to something that's really big, and so if you try to think a picture, your brain is doing a better job helping you have a mental map of what you're looking at.

Mat Kaplan: Yeah.

Buell Januzzi: What you're looking at right now in the center here is what's called the Test Tower. We named it after Dan Neff, who's one of the founding engineers of a company in town called M3 Engineering. They primarily work with mining companies around the world to build complex facilities out in remote areas, and they have worked with us in the past in building big telescopes like the large binocular telescope on that ground.

Mat Kaplan: Yeah, yeah.

Buell Januzzi: Dan was one of the people that helped design the Test Tower. So what's the Test Tower? The Test Tower is what holds the mirror that you're testing isolated from vibration. So these three big pillars that you see here are the corners of a triangular part of the floor here that's sitting on giant airbags so that we don't end up having vibrations from trucks or other people going by. Then, above it is a tower that, in this case, you can look up and see. There's a 4-meter fold sphere up at the top, that mirror that was also...

Mat Kaplan: Yeah, and we're looking up through a very high tower, I don't know how distant that is, with different levels. It's almost as if we were at a launchpad at Kennedy Space Center.

Buell Januzzi: It's not quite that big, but I'm glad you're inspired by it, but it is not big enough to test a segment of the Giant Magellan Telescope. For your audience, the whole point of a mirror is to collect a lot of light... these primary mirrors, collect a lot of light, but then bring it to a focus to make an image. If you want to test the surface, you can't just use your eye and look at the surface and say, "Oh, that's right. That's the surface we want." You have to have a way of measuring it, and we need to have the accuracy to be a fraction of the wavelengths that you're trying to actually focus. So you need to actually shine light on the mirror and measure where that light goes, and when you can show that it's not exactly right, use math and computers to create understanding of where the errors are in the surface, and then you go rub on any high points, and you have to be careful not to overcorrect or polish too much because there's no way to add glass back. So if you take away too much, you have to remove more glass from the rest of the surface to get the whole surface the way you want it.

Mat Kaplan: It reminds me of when I was sanding an old wooden floor in my old house. Of course, if you know go too far in any one spot, you're going to have a little divot there for the rest of the life of that floor.

Buell Januzzi: That's exactly right. So the Test Tower was originally sized for testing where the light would come to focus for an 8.4-meter telescope. But now, we're testing a segment of a 25-meter telescope. So we want to focus the light where the light of a 25-meter telescope would focus. That's going to be three times higher than where the 8.4-meter telescope was focusing it, and that would run into this football stadium. So we had to put that fold sphere to bend the light back so that we have a total path length, total distance of the light from the primary travels that is long enough that we can test the image quality from the mirror. We have multiple different tests, and then we need all of them to agree. They all have slightly different strengths in what they can test, so they are not a perfect substitute for each other, but you can require that they all be giving a consistent answer, and that's what we do. The mirror you're looking at right now is the third segment for GMT. We've just completed it. We're going through the formal acceptance testing, and we have cast three others. So we've cast a total of six, and we're casting the seventh this coming year in 2023.

Mat Kaplan: That will be it.

Buell Januzzi: So we're hoping to make one more, the eighth, that would be swapped in to help just with logistics when we're recoating mirrors, but one reason I'm excited about getting the seventh cast, and then finished is that is the minimum number, and then we'd be ready to go.

Mat Kaplan: Cannot wait, of course, to see that telescope reach first light, and it says right here, "Giant Magellan Telescope Segment 3."

Buell Januzzi: Here, there's also a sign that says, "Interface," and that's the company that Richard F. Caris founded. It makes load cells for lots of applications, predominantly the oil industry. The woman that we were talking about earlier, Karen Kenagy, who is about to retire after having a long career here and many roles, including helping us maintain and develop a culture of safety, she is responsible for our connection to Richard F. Caris. She was our procurement officer, and Richard F. Caris, who was the head of the company, he founded to Interface, called us up to say, "Why are you guys at the University of Arizona buying load cells at weird times of the year in small numbers?" Compared to what he was used to, and Karen was smart enough to tell my predecessor, Peter Strittmatter, that the head of Interface had called up wanting to know what we're doing with his load cells, and that started a connection with Richard. Richard had no prior connection to the University of Arizona, but he was very interested in doing things that were exciting and new, and fell in love with what we're doing here at the Mirror Lab. Over a 15-year relationship, he helped support the start of the Large Synoptic Survey Telescope. Now, they're in Rubin Observatory. He was the second philanthropist to help contribute to that project, allowed us to buy the glass that made the primary mirror for that observatory, and then he made a very generous contribution to our involvement in the Giant Magellan Telescope. That's why we renamed Mirror Lab in his honor. You can see. I can show you a picture of him and Roger Angel turned the lab on one of his visits, but that's why we honor Interface with their signup.

Mat Kaplan: Right next to the University of Arizona, the big A there.

Buell Januzzi: Next to the big A and the Giant Magellan Telescope logo.

Mat Kaplan: Yeah. I guess we better move along if we want to get back upstairs.

Buell Januzzi: Yeah. This is the what's called the Large Optical Generator. It's basically a turntable with a beam and a tool, a generating tool where you can actually do the polishing of the back of surface. Then, we attached the load spreaders. They can see this in the video you're referencing. Then, the mirror gets flipped over so that the front side is up, and then the initial stages of generating the surface are done on this machine. Then, it gets moved over to the large polishing machine, which is in the other end of the hall. Then, it spins a year or two moving back and forth from being polished, and then being tested, polished and tested.

Mat Kaplan: Each time that move, I mean, you're moving many tons of glass and support structure.

Buell Januzzi: Yeah. Yeah, about 17 tons plus a few more tons.

Mat Kaplan: We're squeezing through a little spot here to go over to the other end of this long room. Here's a big laser for your interferometer.

Buell Januzzi: Yeah. This is actually monitoring the fold sphere because every element that's helping to test the mirror surface needs to also be monitored.

Mat Kaplan: We've just stepped through a doorway into yet another room and yet another amazing assembly here. What's happening here?

Buell Januzzi: So this is what we call the Integration Hall. So the Mirror Lab now has three big rooms: casting, polishing, and integration. Integration is where we put load cells on the back of the mirror, ways of supporting the mirror when it's in a polishing cell. It's also where we store mirrors while they're waiting for the next step, and what you're looking at here is a relatively new thing that Jeff Kingsley and I came up with when we were realizing that we're running out of space, and I said, "Can we have a CD rack?" That's what our engineers were able to come up with.

Mat Kaplan: I mean you got three mirrors here stacked on this, again, very heavy-duty monster girders, and it is like a little CD storage system.

Buell Januzzi: Old enough to still use CDs then. It's like a CD rack storage, and so you can see here the fourth segment, which is the one that has the central hole in it. The central hole of that mirror is 2.4 meters, which is the size of the Hubble Space Telescope, and then the fifth segment, and the sixth segment.

Mat Kaplan: Behind us, a huge gantry that's going to slide those gigantic CDs in and out.

Buell Januzzi: That's right. That crane, which can lift 55 tons, and these mirrors are around 17 to 20, is the way we get them in and out, and then that doorway is how the mirrors leave the lab. I know it doesn't look like a door because it's the whole wall. The whole wall slides open.

Mat Kaplan: Absolutely magnificent. Sign on the wall, "Crane lift in progress. Do not enter." Not at the moment, but it's there.

Buell Januzzi: Yeah, so it's safe. Safety is important, incredibly important for our people and also for all the equipment and the mirrors. People sometimes say, "Why aren't you wearing hard hats all the time?" Well, we are wearing hard hats when we're like doing crane lifts or moving and things like that, but we don't want hard hats falling on top of our mirrors if we're moving anything.

Mat Kaplan: Oh, yes. Right.

Buell Januzzi: So if we were polishing a mirror right now and we're not, we're testing, it would be on this turntable. Over on the upper right there is the stress lap, which is one of the laps that we have. That's the largest one. Its shape can actually be changed by applying forces on the back of it, and then over on the left...

Mat Kaplan: Almost like a mirror that's being deformed.

Buell Januzzi: A little bit like a deformed mirror, except that the technology is very different, but I'm sure that in Roger and other people's thinking, it's not a coincidence. That polishing lap is on the other end of this beam. You can see that everything in the lab was designed for making mirrors that are symmetric around their own center. If you think of a circle, your brain says, "Well, of course, a circle is the point equidistant from the center," and you say, "Is a circle symmetric?" Of course, it is. Then, you look at a circular mirror. If you ask, "Is that symmetric around its center?" For most telescopes, the answer would be yes. But for the Giant Magellan Telescope, it is not because the mirrors out on the petals, the six outer mirrors, are symmetric around the center of a 25-meter mirror. That means that each of these mirrors depart by 11 millimeters from being symmetric around their own center. They look more like a potato chip, and you can't see that with your eye, but that makes them much harder to polish. To me, what Buddy Martin, and Steve West, and their groups do to accurately measure where the surface is, and then compute where they need to polish, and then polish it is one of those really amazing things that's done here at the lab.

Mat Kaplan: Almost miraculous. Do you remember the analogy that you used or if you took a GMT mirror, and it was as wide as the United States?

Buell Januzzi: Yeah. So, Buddy likes to... when he's describing this, Buddy says that if you were trying to make a mirror that is as accurate in terms of its surface as the GMT mirrors or the ones we made for the LBT and you thought of the mirror as being as big as North America, the biggest mountain range or valley that you could have would be about one to two inches.

Mat Kaplan: That's incredible.

Buell Januzzi: So the surface isn't flat, but it has to match what we want it to be through an accuracy of 20 nanometers, and Buddy's analogy just gives you a more intuitive sense. We can't internalize what 20 nanometers means, but we understand what one inch is compared to North America.

Mat Kaplan: Yeah. Absolutely. When we return, I'll sit down with Buell to learn more about the University of Arizona's very accomplished Department of Astronomy and the equally distinguished Steward Observatory.

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Mat Kaplan: We're back now up above the lab to talk a little bit more about how this fits in to the Department of Astronomy, the Steward Observatory. You had all of this. You're basically the chair, right, of the Department of Astronomy, but also the director of the Steward Observatory.

Buell Januzzi: Yes. I'm the seventh director of Steward Observatory and head of the department. Peter Strittmatter, my predecessor, served for 37 years. I am not going to be doing that, but I am in my 11th year. Most department heads or chairs will serve three to five years, and that I think is an adequate sentence for misbehavior. The role of a chair or department head is working on helping to run the academic affairs, the graduate program, the undergraduate program, hiring, review of faculty. Directors of observatories, and I was director of Kitt Peak National Observatory before I came to Stewart, were working on projects like telescope building or new instruments that last on a longer time scale. That's why we need both jobs, and the reason one person has it here and not two, and someday it might be two, is more historical accident. I know when I was being hired, I asked my dean, Dean Joaquin Ruiz, "Why don't you split these jobs? University of Texas has the director of McDonald Observatory, Taft Armandroff, and someone else as the department head." He said, "Well, the budgets for the two units here are so intertwined that the director and the department head would be arguing with each other and would need to come to me to resolve the dispute. That's your job." But I really enjoy the mix for me personally because I was at the National Observatory. I spent a lot of my career helping to develop capabilities for the whole country, so I love doing the kinds of work that you do as a director of an observatory, but I also love working with students and sharing what we're learning with the world through our outreach program. So, for me, it works out pretty well. We are an unusually large department. We have currently 341 undergraduate majors. We have 80 graduate students. Of those 80 graduate students, 55 are getting their PhDs in astronomy and astrophysics, and the others are students in the College of Optical Science, or Physics, or Electrical Engineering who are working with our faculty. Then, we have 70 faculty. 35 of them are tenure track, and we have a large number of research faculty. We are involved in a lot of exciting missions like the James Webb Space Telescope. The infrared camera was led by Marcia Rieke, former associate head in our department and Regents' Professor here. Also, we're celebrating the 100th anniversary of our public lecture series on September 28th with Marcia as a speaker, and she's also our very first holder of an endowed chair in honor of Elizabeth Roemer. Elizabeth was an expert on comets on our faculty here in the '60s, '70s, and '80s. She also played a major role in helping to get the Department of Planetary Science, our sister department, created.

Mat Kaplan: There are a lot of busy astronomy departments, but I don't know that there are any that have their hands in more diverse areas of development and observation than steward, and what you've just said is more evidence of that. Talk about some of the ground-based telescopes that are part of the observatory.

Buell Januzzi: Sure. No, you're right. I mean, along with our sister department, LPL take us together. The University of Arizona has ranked number one in the NSF HERD rankings. Sounds like cattle, but what it actually is, is a tracking of research dollars expended in an area or activity. So we have been spending more money, and that gets us a number one ranking. The fact that we keep winning our grants from NASA, DEO, NSF, and other groups to do the work is a sign that we have a lot of talent, and talented staff, and experience doing really big missions. You're right. That includes telescopes like the Large Binocular Telescope, the Giant Magellan Telescope, but we also help others build telescopes. The University of Tokyo is building a telescope called the Tokyo Atacama Observatory. It is going to be at an altitude of over 5,000 meters, 18,000 feet on Chajnantor in Chile. It will be the highest observatory on the planet, and it will be able to observe at mid infrared wave lengths that no other observatory can reach without going to space. We just shipped their mirror this past Monday on the 19th.

Mat Kaplan: Wow.

Buell Januzzi: It's making its way to California right now, and then down to Chile. So, in the next two years, it will be integrated into their telescope. The Large Synoptic Survey Telescope for Rubin Observatory was delayed. The construction was delayed by the pandemic, but that should be coming online very soon. It's going to be operated by NOIRLab, the National Observatory, in partnership with DOE.

Mat Kaplan: By the way, that is one a lot of us at The Planetary Society very excited to see finally coming online.

Buell Januzzi: Yeah. No. It's going to be an amazing facility. It's got four major science themes. U of A was one of the four institutions that got that going. We're still part of the LSST Corporation, which is transitioned from trying to get the project started, which they did successfully, to raising funding to help do the science that will be done. Then, we're also very involved in smaller space missions, things that are still exciting, but not as well known as James Webb. We have a new faculty member, Carlos Vargas who, as a postdoc here, won a $20 million award from NASA for a project called Aspera. It's going to map the warm gas around nearby galaxies, learn more about feedback and star formation.

Mat Kaplan: That, by the way, came up here because it was also supported, I believe, by a NIAC award, Aspera. Yeah, it was good. Very interesting. I didn't know there was a relationship there.

Buell Januzzi: Yeah. I haven't finished researching this. We think he's the youngest person ever to be selected as a PI for a NASA mission, and one of the reasons I think he's able to do that is because we provide an environment. One, we don't say no to a postdoc when they come to us and say, "I want to do a space mission." We do say, "Are you sure?" and then we try to help them out. Chris Walker, a member of our faculty, has a high-altitude balloon mission that will be going up in December of 2023 called GUSTO. So this is NASA's program to use high-altitude balloons to get as close to space as you can get without actually going to space, and that enables things like UV astronomy and terahertz or far-infrared astronomy at a much lower cost than space. You just couldn't do it at sea level or on a mountain top. So we are involved in... and then we have one of the largest groups of theoretical astrophysicists of any university. We're known more for things like the Mirror Lab, but in the modern era, our students are working not only to understand how to make innovative new measurements, but also how to model the problems they're trying to understand using the most sophisticated techniques, high-performance computing as well as simulations. So we need to have the world's experts and those kinds of techniques to train our students as well.

Mat Kaplan: Training as the astronomers of tomorrow, the ones who will be taking on these instruments.

Buell Januzzi: Absolutely. You'll often hear people say, "Oh, I got to live in the golden age of astronomy," and I think it turns out that the reason that's true is it's a very human endeavor. So the more people who are doing it, the more people you have to share what you're doing with, and it stimulates each other to do more, and you can collectively do more. When Andrew Ellicott Douglass, the first director of Steward about a hundred years ago, was dedicating our first research telescope, which was a 36-inch telescope. It was called the All-American Telescope because it was the first telescope made of entirely American-made parts in North America, and it was dedicated on April 23, 1923. He was the whole department. Now, we have 450 some odd people. The staff are incredibly important. It's not just the astronomers and the students, and then you've got another few hundred people over in planetary science. So we went from one person doing astronomical research to over 600.

Mat Kaplan: You run a medium-sized corporation or the equivalent of that, but you're an astronomer and a cosmologist. Do you get to do much anymore?

Buell Januzzi: I actually survived maintaining what I was doing for the first seven years that I was here. I, basically, am mostly doing administration now, but I still am the PI of the current GMT mirror contracts. That's not necessarily what I would've called research 10 years ago, but they're elements of that. I'm also part of the Event Horizon Telescope Collaboration, which uses a bunch of radio telescopes to make images of the Event Horizon Black Hole, which I didn't even get to mention. That project is something that about 20 faculty and 20 of our faculty and students, graduate students are involved in here.

Mat Kaplan: I didn't know the UA had such involvement in the EHT. That's great.

Buell Januzzi: We have two millimeter wave telescopes. One of them, the Submillimeter Telescope on Mount Graham, has been involved in the EHT from the very beginning. It was one of the first telescopes that was used to demonstrate that these kinds of observations might be possible. That got started under Lucy Ziurys, a member of our faculty, and Peter Strittmatter, and then Dimitrios Psaltis and Feryal Özel, and Dan Marrone, and others here. Dimitrios and Feryal have recently moved to Georgia Tech, but Dan Marrone is still here. CK Chan and others. We have been involved since 2012. When the Event Horizon Telescope Collaboration was being formed, we were part of that, and we now support two telescopes, one instrument, also a lot of the simulations. So we have a lot of faculty and students that play a major role in that project.

Mat Kaplan: Just one more question. I will mention in passing, you talked about your sister department, the LPL, Lunar Planetary Lab, which I'm also talking to folks, some of the folks from there.

Buell Januzzi: Yeah. We like to say that they get the solar system. We get everything outside the solar system, and we fight over the exoplanets.

Mat Kaplan: With any luck, pretty soon, we may be identifying some of those exoplanets as being earth-like. Thanks to a lot of the work that's being done here. The outreach side of what you do. We're very close to a planetarium, which is one of the most popular attractions in Tucson, Arizona. Is that also under your department or no?

Buell Januzzi: It's a fantastic planetarium. I'm very grateful I'm not in charge of running it. They do a great job. It was originally part of the Astronomy Department back when it was first built, but it's become a standalone, broader than just astronomy. IT's part of the College of Science, College of Science Outreach. The outreach that we run, that Astronomy runs includes the Mt. Lemmon Sky Center, which is a nighttime observing program for the public. Its director, Alan Strauss, also does a great job of working. There are multiple educational and outreach programs that they support. Some of high school students, some elementary school kids. They're a wide variety, and it's part of our mission because if you're not sharing what we're learning with the public, then you're failing.

Mat Kaplan: Sharing what our boss, Bill Nye, likes to call the PB&J, the Passion, Beauty, and Joy of space and science. Thank you for sharing this, all of this with us today, Buell. It has been a realization of one of my dreams as host of this show. Thanks for sharing it with our audience as well, and I will just say one more thing. On a cabinet near us is the cardboard model of the GMT that I built with my grandson, and so it's great to see that. I cannot wait to see the actual GMT.

Buell Januzzi: I agree. Our colleagues in Korea. So one of the partners in the GMT is the Korean Astronomy and Space Institute. Yeah. I'm ready. I love this model, but I'm ready to move on to the real thing.

Mat Kaplan: Maybe we'll come up with one or two more that we can give away as part of this week's What's Up Space Trivia contest.

Buell Januzzi: Yeah, we'd be happy to give you some.

Mat Kaplan: Ah, thank you.

Buell Januzzi: Right.

Mat Kaplan: Thanks very much for all of this.

Buell Januzzi: You're very welcome.

Mat Kaplan: Time for What's Up on Planetary Radio. Here is the Chief scientist of The Planetary Society, Dr. Bruce Betts. He is also the program manager for the Light Sail program. Bruce, just as you predicted last week, Light Sail 2 is no more, except in our very fond memories.

Bruce Betts: Yes, yes. Light Sail 2, as you probably mentioned, deorbited, burned up after three and a half years. On November 17th-ish, the spacecraft is done, but the mission is not over as we continue to analyze data over the coming months and years.

Mat Kaplan: I think it will be a legacy for many, many, many years to come.

Bruce Betts: Cool.

Mat Kaplan: That's just my opinion. Don't go by me.

Bruce Betts: I mean, frankly, that's all that matters, Mat.

Mat Kaplan: Well, we'll have more. In fact, we will hear from the CEO, Bill Nye, about this topic next week when we also celebrate the 20th anniversary of Planetary Radio. There's still stuff up there, right? It didn't all fall and burn up.

Bruce Betts: No, but it's surprising how much stuff is falling down and burning on a regular basis. No. There are planets that are nowhere near us, so they don't have much of a chance. Although Mars is coming closer and closer. It will still be a really, really, really, really long ways away, but it will have its closest approach, so to speak, to Earth for the next 26 months on December 8th. What does that mean? It means it is really bright. I'm sorry. December 8th is when it's on the opposite side of the Earth from the Sun. Opposition technically usually shifted by a few days due to elliptic orbits from the actual closest point. Anyway, it's going to be bright, and when something is in opposition, it means it rises around sunset and sets around sunrise. So you'll be looking in the very early evening over in the East, later in the evening, higher up. It's really bright. It's almost as bright as Jupiter now. It's reddish because it's Mars, and it's cool. So, Jupiter, also up higher in the sky over in the South or just high up in the North if you're in the Southern Hemisphere, and Saturn farther towards the West looking yellowish and not as bright. one more thing, we're getting to the winter hexagon, which I've mentioned before, but I'll mention it again. Later in the evening, if you look over in the East, and it is, one, not winter in either hemisphere, but it will be soon, and it's named for the Northern Hemisphere Winter. Sorry. Surprisingly enough, six stars form a hexagon. Really bright stars over a big part of the sky, including Rigel, and Orion, and the brightest star in the sky, Sirius, and that will be up in the East. Mars is inside the hexagon right at the moment, in between, but not quite Aldebaran and Capella. You can find more information, including a graphic of that at planetary.org/night-sky. You look like you have a question.

Mat Kaplan: Is it true that it used to be an octagon, but two of the stars were kicked out for unbecoming conduct? I'm just asking.

Bruce Betts: I can neither confirm nor deny that. I'll have to check with them, the appropriate sources. Moving on, how about this week in space history?

Mat Kaplan: Sure.

Bruce Betts: It was four years ago that NASA's InSight mission landed on Mars, given us Mars quake information and other information about the surface and the interior of Mars, and is about to be decommissioned due to dust on solar panels.

Mat Kaplan: Onto "Random Space Fact." That was the deliverance version of Random Space Fact, I think. I'm waiting for the Dueling Banjos.

Bruce Betts: Random, Random, Random Space Fact. Random, Random, Random Space Fact.

Mat Kaplan: Okay.

Bruce Betts: Random, Random, Random Space Fact.

Mat Kaplan: That's the idea.

Bruce Betts: Oh, I'll stop. Artemis 1 SLS launched, launching Orion towards the Moon. Orion will fly farther than any spacecraft built for humans, although doesn't actually have humans in it yet, any farther than any spacecraft built for humans has ever flown away from earth. Over the course of the mission, it will travel about a half million kilometers from Earth or about 64,000 kilometers beyond the far side of the moon, which puts it farther away than any other human-designed spacecraft. There will be humans in there eventually.

Mat Kaplan: Someday soon.

Bruce Betts: Also, it will stay in space longer than any human spacecraft without being a space station, docking to a space station, but also, it's going to be hotter. It's going to return faster and hotter than ever before when it hits that atmosphere.

Mat Kaplan: I hope to be there when it is brought ashore at the San Diego Naval Station, which is five minutes from where I live. So I hope to make another trip down there, and this time, watch them pull in a real one.

Bruce Betts: Is it true that they picked San Diego because you were down there?

Mat Kaplan: I hate to say that I used my influence, so I won't.

Bruce Betts: Let us go onto the tribute contest where I still managed to confuse people accidentally apparently. Sometimes I do it on purpose. Usually, it's not. I'm confused by this one, but I suppose it was. I asked you for whom are the two Viking lander sites named? Tell us how we did, Mat.

Mat Kaplan: It was quite clear to me. There were a number of people who sent in entries with the names of the regions on Mars that the two spacecraft landed in back in 1976. Thank you to those of you who went to the trouble of looking that up. I have the answer, I believe.

Bruce Betts: Please share.

Mat Kaplan: It's from Dave Fairchild in Kansas, our poet laureate. "If you want some images from Mars of rocks and stuff, then look to find the landing spot that's named for Thomas Mutch, and then your project scientist at Gerald Soffen Station, it's no surprise we emphasize their Martian exploration. "Stuff" and "Mutch" is a little bit of a stretch for a rhyme, but I get it. I get it. It was a tough one.

Bruce Betts: And such?

Mat Kaplan: For rocks and such. You're absolutely right. Bruce, you are the new poet laureate for Planetary Radio.

Bruce Betts: I'm the poet editor, a strange little known...

Mat Kaplan: "From Mars of rocks and such." You're right. You're absolutely right. Dave is slapping his forehead as he hears this. I have no doubt. This person has not won in 15 years, almost exactly 15 years.

Bruce Betts: One, that is amazing, and way to go, persistence. Two, it is amazing that you have those records. Well-played, sir.

Mat Kaplan: I don't this time. I'm not sure I would if I didn't have to check because Mike told me himself, Mike Tate in Texas. He said his last win was November 26th, 2007 when we gave him a little piece of a Martian meteorite. Remember when we did that?

Bruce Betts: I do. I do. That was a very fine prize. Well, anyway, then nevermind. I'm the compliment to you just to compliment to him.

Mat Kaplan: Congratulations, Mike. You're back. He also says, "Thank you for the many years of delivering the universe each week. Planetary Radio is and has been my favorite podcast since they were invented. You're a trailblazer. You have my eternal gratitude for teaching and forming, and bringing the PB&J of this in every world to myself and the many fans of Plan Rad. I wish you the best for what comes next." Thank you, Mike. That's very nice, and thank you to all of you. I continue to get so many of these wonderful messages from those of you who have enjoyed the show. I love every one of them. Thank you so much.

Bruce Betts: The poem mentioned Gerald Soffen was indeed the project scientist of Viking. Thomas Mutch was the head of the Lander Imaging Team, who unfortunately much passed away while the mission was still going along.

Mat Kaplan: Mike, before I forget, we should remind everybody that we're going to send you a signed CD copy of The Moons Symphony, composed by Amanda Lee Falkenberg and available from Signum Classics. Seven movements, each inspired by different moon in the solar system. Highly recommended. It's on my Christmas gift list that people heard me mention. Sarah and I talked about our choices on The Planetary Society Holiday Gift List, not just Christmas, of course. I do have a couple of others. I'll just do this really fast. Mel Powell. "If we ever find the landing side for the Mars Polar Lander, I assume it will be named for Wile E. Coyote's Splat. Poor thing. Too soon?" Robert Klein in Arizona. "Going to miss you 'Mutchly,' Mat, but you have 'Soffened' the blow by hiring such a great replacement." Bruce is holding his head in his hands.

Bruce Betts: Shall we move on?

Mat Kaplan: Yeah. It's time.

Bruce Betts: The Artemis program is launched. First SLS rocket. They named it Artemis partly because Artemis was the twin sister of Apollo, the whole Apollo program. You may have heard of it, Mat. It went to the moon with humans. So here's something for you mythology fans out there. We all know... Okay. Maybe we all don't know, but a lot of people know Zeus was the father of Artemis and Apollo. Who is the mother in Greek mythology? Who is the mother of Artemis and Apollo? Go to planetary.org/radiocontest.

Mat Kaplan: Love these mythological questions. You have until the 30th. That will be November 30th at 8:00 AM Pacific time, and some of you may have heard me mention that model of the Giant Magellan Telescope that I built with my grandson. I told Dr. Januzzi about that during our tour of the Mirror Lab. I've got several of these to give away.

Bruce Betts: Cool.

Mat Kaplan: It's from SCOLA. SCOLA is a Korean company. Buell mentioned that it came out of their Korean partners on the Giant Magellan Telescope. It's really fun. It's a neat thing to build. Four out of seven stars in terms of difficulty. It's a little bit of a challenge, but it's fun.

Bruce Betts: I can tell, but I want you to be clear. You're not giving away the one you and your grandson made together.

Mat Kaplan: No. Oh, gosh. I guess I should clarify. No. These are in the package, brand new, unbuilt GMT model kits.

Bruce Betts: Ooh, new and unopened. Nice. All right. Everybody go out there. Look up the night sky, and if a moon symphony is too much for you to create, to write as it would be for me, what would your moon jingle sound like? Thank you. Good night.

Mat Kaplan: The dish ran away with the spoon. I guess there's no music to go with that, but you can come up with a jingle for us.

Bruce Betts: Music. We're looking for the music. All right. Nevermind.

Mat Kaplan: Music. Yeah. Okay. I got the lyrics. He's Bruce Betts, the Chief Scientist of The Planetary Society who joins us every week here on What's Up. Congratulations on the completion of a three and a half year solar sail journey around the earth.

Bruce Betts: Thank you, and thanks to all who made it possible, including the 50,000 individuals who gave to it and all of the staff, all the people that... I'm going to name every one of them, if that's okay, Mat. I'll just...

Mat Kaplan: We're going to go now, Bruce.

Bruce Betts: Okay. There was Bruce, and Mat was there for some stuff. Oh, yeah, the project manager for operations, Dave Spencer, and John Bellardo from Cal Poly San Luis Obispo handling ground communication and software. Barbara Plante...

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California and is made possible by its farsighted members. Catch your reflection at planetary.org/join. Mark Hilverda and Rae Paoletta are our associate producers. Josh Doyle composed our theme, which was arranged and performed by Pieter Schlosser. Ad astra.