Planetary Radio • May 26, 2021

The New Great Space Observatories

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Grant Tremblay

Astrophysicist at the Harvard and Smithsonian Center for Astrophysics

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Bruce Betts

Chief Scientist / LightSail Program Manager for The Planetary Society

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Mat Kaplan

Senior Communications Adviser and former Host of Planetary Radio for The Planetary Society

The National Academies of Sciences, Engineering and Medicine will soon issue the Astro2020 Astronomy and Astrophysics Decadal Survey. It will rank four major proposals for exciting, expensive new space-based telescopes. Astrophysicist Grant Tremblay joins us to explain why all four competing instruments have been grouped as The New Great Observatories, hoping to repeat the marvelous success of a quartet of previous telescopes: Hubble, Spitzer, Chandra and Compton. Then we’ll join Bruce Betts on board the International Space Station for a space trivia contest about one of its commanders.

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LUVOIR Observatory Concept
LUVOIR Observatory Concept Illustration of the Large Ultraviolet Optical Infrared Surveyor (LUVOIR) space telescope.Image: NASA
Lynx X-ray Observatory
Lynx X-ray Observatory Artist's concept of the Lynx X-ray observatory.Image: NASA
Origins Space Telescope Concept
Origins Space Telescope Concept Artist illustration of the Origins Space Telescope (Origins) concept.Image: NASA

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Mat Kaplan: Four powerful new space telescopes, which of them will win? 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. Which of them will win? There's a tease line, if there ever was one, and it's the wrong question. It's not that one of these magnificent instruments will win in the soon to be issued Astro2020, Astronomy and Astrophysics Decadal Survey, but they will be ranked, and it's likely that not all of them will be funded by NASA. Astrophysicist Grant Tremblay hopes all will be recognized as the complimentary tools that could work together to answer those greatest of questions, where do we come from? And are we alone?

Mat Kaplan: Grant will join us for a conversation about The New Great Observatories right after we take a look at The Downlink and just before we welcome back Bruce Betts for another edition of What's Up. We can congratulate China yet again, its Zhurong rover has rolled down onto the surface of Mars. So, there are now three mobile robots exploring the surface of the Red Planet, with the InSight Lander continuing to peer beneath that surface. You can check out our coverage at Want to ride into space? Last I checked, the current bid for a seat on Blue Origin's New Shepard was up to $2.8 million. All those dollars will eventually go to the company's Club for the Future, a foundation that encourages young people to enter STEM careers.

Mat Kaplan: Can't quite compete at that level? Well, you could try out for Who Wants to Be An Astronaut? The new reality TV show that promises to put its winner on the International Space Station. I guess this is progress, right? Nearly 300 white papers were submitted to the National Academies of Sciences, Engineering, and Medicine, as part of the Astronomy and Astrophysics Decadal Survey. There are proposals for research and instruments, ranging from the relatively inexpensive to what used to be called flagships, projects that will cost billions and take many years to fulfill. There are four of these major projects, and Grant Tremblay loves all of them.

Mat Kaplan: Grant works at the Harvard & Smithsonian Center for Astrophysics, and is most closely associated with the proposal for Lynx, an amazing X-ray telescope that would be orders of magnitude more powerful than the Chandra instrument that has been in space since 1999. But Grant is also part of a grand coalition that unites all four proposals and teams. He joined me a few days ago.

Mat Kaplan: Grant, welcome to Planetary Radio. I'm very happy to have you on the show and you come highly recommended, including a recommendation from the great Heidi Hamel, who has been heard many times on the show, who said, "You got to talk to Grant Tremblay about The New Great Observatories," and here you are, welcome.

Grant Tremblay: Well, let me tell you about Heidi Hamel, Mat, Heidi Hamel is a personal hero of mine. I was in fourth grade, I think, when Shoemaker–Levy 9 hit Jupiter, Heidi, of course, rose to fame because she was the PI of those Hubble observations. And even though I was in fourth grade, I remember that very vividly, and I remember her storming into the Bahcall Auditorium at the Space Telescope Science Institute during a realtime press conference, showing the results live. And it was just an astonishing moment. And as a fourth grader, I remember that, and it was one of the things that inspired me to get into astronomy. So, to be able to talk with Heidi weekly is just the greatest honor.

Mat Kaplan: And I'm sure she's forgiven you for saying that this happened while you were in the fourth grade.

Grant Tremblay: Well, look, it's a testament to the longevity and the power of the great observatories to span decades, and also Heidi is a spring chicken.

Mat Kaplan: Yeah.

Grant Tremblay: Many more years of discovery ahead, Heidi.

Mat Kaplan: Well done. And now, not just a great scientist, but a fine administrator as well.

Grant Tremblay: Absolutely.

Mat Kaplan: As you know, as we've heard on this program. And you spent some time at the Space Telescope Science Institute, right?

Grant Tremblay: Yeah, I did about half of my PhD at the Space Telescope Science Institute, the operational heart of the Hubble Space Telescope. My office was actually in the former Hubble control room, which later moved to the Goddard Space Flight Center. But, yeah, it's pretty cool.

Mat Kaplan: That's exciting. Now, of course, among other things, you are involved with one of the four projects, or deeply involved with one of the four projects that we're going to be talking about, although we are going to talk about all four of them, because you have put your energy behind marketing. And that, I'm sorry to say, is the word, but it's a necessary word for what's going on right now because, as we have heard from many others on this show, we are in the midst of a new decadal survey, not the Planetary Science Decadal Survey, but a different one, and these four telescopes that make up what you are calling The New Great Observatories, and we'll explain why new in a moment for anybody who doesn't know about the old ones, no offense, man, why is this happening right now as part of the decadal survey?

Grant Tremblay: Yeah. So, every 10 years, on the decade, the National Academy of Science runs the so-called decadal survey. In order to build and fly these great observatories, these multi-billion dollar, multi-decade generational flagships that really push out word on the edges of human understanding, in order to get the money and the constituency and the drive to build them, you need the top recommendation of the decadal survey. So, as your listeners probably know, there are multiple decadal surveys. Astronomy was one of the first. Since 1960, there's been a decadal survey, and it is the top recommendation from that survey that gives life to the generational flagships of space astrophysics to come.

Grant Tremblay: So, the Hubble Space Telescope came out of the 1970 decadal survey, Chandra was the top recommendation of the 1980 decadal survey, Spitzer, 1990, JWST, 2000, Nancy Grace Roman Space Telescope, 2010, and here we are in 2020.

Mat Kaplan: Quite a process. And NASA pays close attention to the recommendations of the decadal survey, doesn't it?

Grant Tremblay: They're obligated to pay attention. It's literally hard-coded into law, Section 805, Public Law of the NASA Authorization Act of 2010, for example, literally requires NASA to follow the recommendation of the decadal survey to the best of their ability, of course, but absolutely, NASA is obligated to follow the decadal.

Mat Kaplan: By and large, it has proven to be a pretty good practice, right? Because, I mean, we have now this being steered, not that politics don't ever enter into it, but largely driven by the scientists who want to answer these great questions.

Grant Tremblay: Absolutely. Look, ultimately, these are engines of science, they're platforms of discovery, their design, their so-called level one science requirements, or the questions that they are built to pursue are defined by the scientific community. They are designed to pursue the most urgent astrophysical questions before us. These aren't niche science experiments, these astrophysical questions are literally like, are we alone? How does the universe work? How did we get here? They're the biggest questions before our species and the life that covers our little rock in the void. I love that the decadal survey effectively puts the science first, and it is the science that drives the requirements, and therefore, the mission design.

Mat Kaplan: And there are some pretty fierce competitions that frequently surface during the decadal surveys, all of the decadal surveys, and as we've said on this show, so many worthy proposals, and only a few that will receive the enormous amount of funding that it's going to take to make them a reality. You've already mentioned the great observatories that have done their work, a couple of them still doing that work, just taking them in order of electromagnetic wavelength, Spitzer starting at the bottom with infrared, Hubble, a little bit of infrared but largely optical, Chandra, X-ray, and topping it out, Compton, cosmic energy. And I mentioned that, cosmic rays, I mentioned that because we're looking in a sense at kind of the same spread across the spectrum with what you are calling, as we said, The New Great Observatories. Is that fair?

Grant Tremblay: Absolutely, yeah. Look, the Great Observatories program began in the mid '80s after a conversation between the head of NASA Astrophysics at the time, Charlie Pellerin, and someone named George Field, who actually ran the 1980 decadal. It began as a branding exercise. In the late '80s, the economy was in the tank, thanks to the savings and loan crisis in the U.S., we had just suffered an immense human, a national tragedy, the Challenger disaster, the Hubble Space Telescope was massively behind schedule, massively over budget, and following the Challenger tragedy was without a launch vehicle. We still had grand plans, right?

Grant Tremblay: And so, it began as a branding exercise in order to effectively market this constellation of space-born observatories literally in D.C., on the hill. A brochure was drawn up, they hired a great cartoonist, but that thing wasn't meant for the public, that was meant for Congress people and their staffers. And it turns out, here we are now three decades later, and Great Observatories is no longer just a piece of programmatic branding for four missions launched between 1990 and 2003, Great Observatory means a powerful, flexible, long-lived discovery platform that is flexible enough to pursue questions we literally haven't even thought of asking it, right?

Grant Tremblay: When the Hubble Space Telescope launched, we didn't know for sure that exoplanets existed. And now, some of the top level Hubble science comes from exoplanet observations. One of the level one science requirements for the Hubble was to measure the deceleration perimeter of the universe.

Mat Kaplan: I was hoping you'd get to this.

Grant Tremblay: The deceleration perimeter. And Hubble later found out, won the Nobel Prize a couple of years ago, that we had the design wrong, that it's an acceleration perimeter of the universe. Yeah, Great Observatories, it's not just branding anymore, it's a vision for these incredibly powerful platforms of discovery. So, that means that the great observatories aren't just those four missions, Hubble, Compton, Chandra, and Spitzer, it also applies to the James Webb Space Telescope, and the soon to come, Nancy Grace Roman Space Telescope, but it also applies to these four profound visions for discovery that are currently under competition at the decadal survey now.

Mat Kaplan: I think of these as investments with a good return on investment. And I also think of them, since it's a big word nowadays in Washington and elsewhere, as infrastructure. That might be a stretch for some people in Congress, maybe even for the administration, but I wonder if you agree with me in any sense.

Grant Tremblay: Oof, I'm bullish, Mat. I don't even think it's a stretch. This is a shovel-ready infrastructure of the highest order. It is infrastructure of discovery. It checks all of the jingoistic boxes on the hill. American-made tech, intellectual leadership. I find the comparison is really uncomfortable, but for a lot of our colleagues on the hill, it goes a long way that China can't build a JWST, and it hits at all this cold war, asks space racy stuff that I think is largely unhelpful, but does carry a lot of water on the hill. Look, I view these things as profoundly, profoundly worthy, and frankly, cheap or kind of a great deal investments in everything from soft power, national.

Grant Tremblay: Nations spend billions of dollars on soft power around the world. And the Great Observatory is something that is not designed to hurt anybody, something that's designed only to push outward on the edge of the human understanding, is a fantastic investment in global soft power, because that's real power that has the power to inspire a kid to get into space, to pursue their curiosity. Yeah, look, these things are not cheap, but they are phenomenal investments in discovery. And it absolutely is infrastructure. So, that includes everything from the upcoming Infrastructure Reconciliation Bill, yeah, that it's infrastructure.

Mat Kaplan: Grant, I begin to understand why Heidi and others recommended you so highly as someone that I should speak to, awareness of real politic while keeping your eyes on the stars, I think. These are inevitably international projects, right? Certainly, the European Space Agency would have a deep interest in these.

Grant Tremblay: Absolutely. These are global projects. These are observatories for everybody. Literally, anyone around the world can write a proposal to use the Chandra X-ray Observatory right now, right? Does not matter your affiliation, if you even have an affiliation, the data is free for all. There's a one-year proprietary period on a lot of the data to allow the scientists to write their paper and have their student write their PhD thesis, but the data is completely public after a year. Anyone can download it. You can't pay for the data, you can't buy the data. Yeah, these are absolutely global projects.

Grant Tremblay: First of all, the Hubble is a NASA/ESA observatory with immense participation from the CSA, but astronomers and scientists all around the world use these observatories, design these observatories, work on these observatories. They're global projects.

Mat Kaplan: Normally, I might provide the individual web addresses of each project on this week's episode page,, but you've made that much easier, because you've collected this under the, .org. And so, we will definitely put that up on the page. But let's start to talk a little bit about these four telescopes that you've brought together under this single brand, and in this case, instead of doing it by order of spectrum covered, let's do it alphabetically, which is also the way you list them on the website.

Grant Tremblay: Let me just give you a little bit of context first about why we're doing this. I'm in the leadership of the Lynx X-ray Observatory team. I've dedicated years of my career, an enormous amount of blood, sweat, and tears, a lot of emotion, a lot of love for something that I've never been more proud of professionally, and that's the Lynx's final report. So, you might think that when on August, I think it was August 18th or 19th of 2019, all of our final reports were submitted to NASA and became public, you might think that I immediately went to our so-called competitors and downloaded their reports and just read their reports with scorn or fury, or, "We're better than them," or some negative feeling.

Grant Tremblay: So, I've read all four reports cover to cover, well, three competitors, and then I helped write substantial parts of our final report, the only thing that I took away with them is that these are just profound visions for discovery. I don't view them as competitors. They are four missions, but they really are one vision that absolutely carries the legacy of the Great Observatories forward. I want to do them all, literally.

Grant Tremblay: And so, we created to try to manifest that, to give something to talk around, to move the Overton window from talking about how each of these projects is so expensive, "Oh, boy, what a lot of risk, what a lot of technology maturation that needs to happen," to, "Yeah, let's just do them all. We've already done it. We did it in the '90s, right? Yeah, these projects are more complex and more expensive, but so are the questions that we're asking about the universe, and so are the technologies that are required to pursue those questions."

Mat Kaplan: You went where I was going to go when we got to Lynx, to talk about why anybody would think that you could be fair to the other three of these proposals, because you have been so deeply involved with Lynx, and still are, but I think that you've demonstrated that more than adequately. All right, now, let's start that alphabetical review, beginning with this instrument called HabEx.

Grant Tremblay: I hate using the term holy grail because it's such a cliche, but one of the holy grails of astronomy is to not only observe Earth-like planets around sun-like stars in solar systems beyond our own, but it's to do, for example, spectroscopy of, it's so-called transit spectroscopy of an exoplanet atmosphere. A host star will shine through the limb of the atmosphere of a transiting planet. As a planet eclipses, its host star transits our line of sight, the star will shine through its atmosphere, and we can do something called transit spectroscopy, and literally do spectroscopy of the blanket of gas that hugs this planet, just like our atmosphere does around the Earth, and measure its elemental abundances.

Grant Tremblay: So, the sort of holy grail, for example, is to observe potential biosignatures in the atmosphere of an exoplanet, HabEx enables that with just an extraordinary coupling of two technologies. One is a light bucket, you need a large aperture sensitive telescope, i.e., a big piece of glass in space. You need at the focus of that glass to put really exquisite instruments, but HabEx is special because it flies in formation with this beautiful flower 80,000 kilometers away that we call a starshade. It literally looks like a flower because it has petals that are for reasons related to things like the Bessel function, which we won't get into here, it is designed to block out the star, the light of the star of distant solar systems, so that we can more easily observe small rocky terrestrial planets orbiting them.

Grant Tremblay: This is ultimately designed to beat down what is ultimately a giant dynamic range problems. So, observing an Earth-like planet around a sun-like star in a distant solar system is equivalent to like trying to observe a firefly next to a Hollywood searchlight when you are standing in Massachusetts. So, it's an immense problem of contrast, of dynamical range, because the planet is literally millions of times fainter than the star. The starshade is the ultimate expression of coronagraphy, of blocking out the light of a star. And you just look at the thing and it's just exquisite. And the science that it will pursue is so remarkable. It is not just exoplanets, it's not just are we alone? It's not just biosignatures, but it's astrophysics across the epics of cosmic time from solar system stuff to high redshift galaxies and everything in between. I'm incredibly excited by it.

Mat Kaplan: Like the rest of these tools, something that will help us to answer what our boss calls the two great questions, where do we come from? And are we alone?

Grant Tremblay: Absolutely. Look, I think that the discovery of life beyond Earth would be the greatest confirmatory result in all of human history. By confirmatory result, I mean that if you talk to professional scientists, astrophysicists, astronomers, the vast majority of them, including me, would tell you that, yeah, it's basically obvious or with almost beyond doubt that there's life relatively abundant in the universe, even if it's spectacularly rare. The numbers involved are just so unbelievably huge. It doesn't matter if you believe the Drake equation or not, or you add immense uncertainties to it, you're talking 10,000 advanced alien civilizations in our galaxy alone.

Grant Tremblay: I take a little bit of a dark existential view of it. I find it overwhelmingly likely that our civilization will live out its brief, brief moment in cosmic time from beginning to end, never truly knowing about any of it, just because the universe is really, really big. And the one over r squared rule for a drop-off in flexor, a drop-off in signal, which is purely a function of geometry-

Mat Kaplan: Talking about inverse-square law.

Grant Tremblay: The inverse-square law is really damned hard to break. Extraterrestrial communication or finding signatures of life beyond Earth is incredibly, incredibly, that's a really big challenge. And so, our best chance at finding life beyond Earth is getting really lucky and finding, for example, potentially life in a subsurface ocean in Europa or Enceladus, or maybe evidence of past microbial life on Mars, a really, really outside chance. The sort of like cosmic horror aspect of it is that it's probably pretty unlikely, if we're honest. Another way we can do it is if we can observe large numbers of planets, because we know that they are just everywhere, more planets than stars, just everywhere.

Grant Tremblay: And I have absolutely no doubt that we have looked at a star with your naked eye or with a telescope, and around that star is a planet that hosts life. And we might very likely never know about it because small planets are hard to observe, you have to get lucky with transits or radio velocity or et cetera, but there's just no doubt in my mind. So, yeah, the greatest confirmatory result in all of human history would be to actually confirm the question that we all basically assume is true, are we alone?

Mat Kaplan: I hope that you and I are both around to discover that you are wrong about our solar system, but-

Grant Tremblay: I really hope so too.

Mat Kaplan: ... right now, the jury's out, and we certainly need to be looking across all those billions of other worlds just in our own galaxy. We neglected to say HabEx, it's the Habitable Exoplanet Observatory, they're proposing to launch in 2035. And that's roughly the range we're talking about for all four of these instruments, right?

Grant Tremblay: That's right. These observatories, these giant multi-billion dollar discovery platforms take decades to build. Look, people are shocked that the James Webb Space Telescope is at least 14 years behind schedule, depending on the notional schedule you're choosing to use as your baseline, I'm not that surprised at all. JWST is the most complex piece of civil space robotics in all of human history. It takes time. These things are not easy. There's a lot of risk to buy down. There's a lot of technology to mature. Yeah, all of these, all four missions are immensely ambitious designs. They will take decades to build.

Grant Tremblay: So, we have notional schedules that we use to design our reference missions. And all of us would be launching in the late 2030s, maybe early 2040s. Yeah, that it takes a while.

Mat Kaplan: And along the way, you discover all kinds of new technologies or refine them that help us here on Earth. It should be said, spinoff supply to development of instruments like this as well as we heard just recently on this show from Jim Gunn and the development of the Wide Field Camera for the-

Grant Tremblay: Absolutely.

Mat Kaplan: ... for the Hubble Space Telescope. Let's go onto another one of these, and you will hear some commonality among some of the goals of these instruments, even though they look very different and they examine, in large part, different parts of the electromagnetic spectrum. I think next, if we keep up our alphabetical order, would be Large Ultraviolet Optical Infrared Surveyor, also known as LUVOIR.

Grant Tremblay: Exactly, LUVOIR. Yeah, LUVOIR has been a dream decades in the making. LUVOIR has had many names in the past, it's had many incarnations. It was once HDST, the High Definition Space Telescope. It was once ATLAST, which I can't even remember what that acronym stood for. But it goes back to the early era drawings of very, very large space telescopes. That's the sort of intellectual precursor to what ultimately became the Hubble Space Telescope. This is Lyman Spitzer's vision writ large. This is the ultimate vision of the great, great, great space telescope.

Grant Tremblay: These four mission concepts, to be clear, were basically defined a little bit by what we call the Astrophysics Roadmap, which formed in 2013 and it formed in the wake of the 2010 decadal, that committee was trying to establish a sort of direction for NASA and preparing ultimately for the 2020 decadal. So, these four mission concepts, some of them have a little bit of overlap. So, HabEx and LUVOIR have pretty, pretty substantially, the Venn diagram between the two, especially in terms of the exoplanet science case, is pretty large. But they designed it, they designed both missions really intelligently, I think, to tackle the issue from sort of two as a pincer movement on ultimately the one big question.

Grant Tremblay: One of the ways they did that was LUVOIR is the grand vision. What do we need? And what do we want? What is our greatest dreams in our UV optical infrared observatory manifest? They didn't just take it as a cost to be damned approach. Yeah, LUVOIR is not cheap, none of us are cheap, but they did it in this incredibly inspiring way by having level one requirements that really are designed to be absolutely transformative in almost every aspect, while being achievable. Look, you can do LUVOIR for less than Apple made on AirPods in 2018 alone. I'm a little bit bullish on the cost, astronomers bucket the costs, but I think these things are absolutely worth it.

Mat Kaplan: It's the one among the four of these that looks like the James Webb Space Telescope on a whole lot of steroids.

Grant Tremblay: On a whole lot of steroids, right. So, LUVOIR, they designed it on beautifully to have the scalable architecture. So, there are many ways that you can scale the size of LUVOIR up and down. You can scale the primary mirror, the size of the sunshade. But, yeah, LUVOIR-A has a sunshade that is 79 meters across. We're talking football fields here. The James Webb Space Telescope is of order the size of a tennis court. Yeah, this puts James Webb, this makes it look tiny in comparison.

Mat Kaplan: Sports analogy is always welcome. There's an interesting term used in the description of LUVOIR, exo-cartography, which, I assume, means that we're talking not just about examining, analyzing the atmospheres of exoplanets, but possibly revealing details of their surface.

Grant Tremblay: So, ultimately, we can talk about complex technical trades in these missions, all of them really boil down to sensitivity and angular resolution, and their given wavelength regime. And LUVOIR has that in spades. LUVOIR is exquisitely sensitive. We're talking more than a hundred times more sensitive than Hubble and James Webb in their respective wavelength regimes, and just astonishing spatial resolution. So, spatial resolution scales with the size of your aperture. 1.22 lambda over D, where lambda is your wavelength.

Mat Kaplan: If you say so.

Grant Tremblay: And D is your aperture diameter, so, that's the diffraction limit of your telescope. LUVOIR would have not only the sensitivity, but the angular resolution to literally do exo-cartography, where you could almost literally map landmasses, oceans, cloud structures, storms, hurricanes on alien worlds. Pretty incredible.

Mat Kaplan: Absolutely incredible. Star Trek stuff.

Grant Tremblay: Star Trek stuff.

Mat Kaplan: I will mention that an old friend of this show, Deborah Fisher of Yale, is a big part of the science and technology definition team for LUVOIR, and they're looking at a 2039 launch date. As we know, and as you've said, these things can slip. Grant Tremblay has more to tell us about The New Great Observatories right after this break.

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Mat Kaplan: Let's go on to the one that you have devoted years and years to, and that's Lynx, the Lynx X-ray Observatory.

Grant Tremblay: Lynx is, by orders of magnitude, the best thing I've ever worked on professionally. I think, frankly, it's all downhill from here. And it was just an unbelievable honor to work on this project with this incredible team. So, to give you a sense of what Lynx is, Lynx takes the legacy of the Chandra X-ray Observatory and carries it forward literally into the next epic of discovery. So, we're orders of magnitude more powerful than Chandra across multiple dimensions. We do science from the shining poles of Jupiter to black holes at the edge of time, and everything in between. Most of the universe is hot.

Grant Tremblay: Across all of cosmic time, this is the so-called missing baryons problem, it turns out the solution is that the baryons are really hot. And the high energy realms of the universe shine in X-rays. These hot realms in the universe shine brightest in X-rays through something called bremsstrahlung emission, through thermal radiation. And so, the way to map most of the universe over most of cosmic time is to design an exquisitely sensitive X-ray observatory. The X-ray universe is a fractal nesting doll. It's fractal. So, it goes from literally the shape of the expanse itself, the pillars of cosmic structure, what we call the cosmic web, shine in X-rays.

Grant Tremblay: So, for the first time, we would be able to see literally the pillars of our universe, so-called cosmic web filaments, which are exquisitely hard to map in emission because they're immensely faint in X-rays and completely invisible in other wavelengths. They're overwhelmingly dark matter. So, it's the hot baryons that are the beacons to observe this spider web of dark matter. So, we would observe that in something called the Lynx Legacy Field, and in that map would be this beautiful fractal, hyperdimensional data cube, because you zoom way down and you would see thousands of galaxies.

Grant Tremblay: And you would see the atmospheres of galaxies, the hot baryonic fountains that cycle from not only star formation, but also stellar death, and also you'd see down to literally the doomed matter that's spiraling around the event horizon of the supermassive black hole in that galaxy center. Because X-rays not only trace the largest scale structures in the universe, they also trace matter that's literally at the ISCO, the innermost stable circular orbit, a couple of Schwarzschild radii from the event horizon of the black hole.

Mat Kaplan: Just outside the edge, if we can call it, out of the black hole.

Grant Tremblay: Just outside the edge of the black hole.

Mat Kaplan: Yeah.

Grant Tremblay: So, it's fractal, it's the largest scale structures in the universe, to the aurora around Jovian-like planets, to stellar birth, all the way through to stellar death, and doomed matter around black holes at the edge of cosmic time. We would see the first black holes in the universe. The best thing I've ever worked on.

Mat Kaplan: What was that phrase you used? I've forgotten the first word already, but it was a phrase for the ages about baryonic fountains.

Grant Tremblay: Yeah. Look, one of my favorite things about nature is that the laws that describe nature are largely scale invariant. And that means that hydrodynamics works the same in your kitchen sink as it does on literally megaparsec scales in galaxy cluster. So, we're talking millions of light years. So, there are Chandra X-ray images of bubbles in galaxy clusters. And if I were to change the color map on that X-ray image and compare it to an image of a water bubble in a pot of boiling water, or a vapor bubble in a pot of boiling water, you literally would not be able to tell the difference, because hydrodynamics works exactly the same way on all scales. Yeah, you have magnetic fields and so on, but the laws of nature are largely scale invariant.

Mat Kaplan: I love this stuff. And someday, we should talk about your colleagues at UC Santa Cruz that I had on the show who looked at the trails left by giant banana slugs and found similar structures stringing the galaxies together across the universe.

Grant Tremblay: Absolutely, absolutely.

Mat Kaplan: And just one more thing about Lynx, you've said it, but I just want you to repeat it. As I looked at the description, you were talking about, in some areas, two orders of magnitude improvement over Chandra, in other areas, close to three orders or a thousand times better performance.

Grant Tremblay: Yeah, that's right. Lynx takes Chandra, it's not just an incremental advance over Chandra, it is a transformational advance. Lynx has over 100 times the sensitivity of Chandra, but it has 800 times the survey speed, a thousand times the spectroscopic power. Chandra has a high spatial resolution, but only on axis. This is a consequence of something called Wolter-Schwarzschild X-Ray grading incidents.

Mat Kaplan: Again, I'll take your word for it.

Grant Tremblay: Take my word for it. So, what that means is that the point spread function or the spatial resolution that's delivered by your high resolution mirror assembly blooms very dramatically off axis. So, that means that Chandra's vision gets very blurry very quickly off axis, Lynx would have that exquisite point spread function across the entire field of view, which would be much wider than Chandra. So, we're talking orders of magnitude more powerful across multiple dimensions. Yeah.

Mat Kaplan: Last for us to consider, and only because it is last in alphabetical order, is the Origins Space Telescope, often, apparently, just referred to as Origins, which takes us back to, I think if I've got it right, the mid and far infrared, but also has some overlap with other instruments that we've been talking about.

Grant Tremblay: I was just blown away by Origins, just like all three of our so-called competitors. Origins is an absolutely beautiful mission. Really, really inspiring stuff. Yeah. So, Origins take a James Webb Space Telescope sized mirror, and cool it to 4.5 Kelvin, barely above absolute zero. That's a technical challenge, but it enables so much advancement. So, ultimately, that drives down your sensitivity curve to enable just orders of magnitude advancement in everything from how galaxies form stars, how they build up metals, how they grow their supermassive black holes, to literally the story of water in the universe.

Grant Tremblay: So, it's a little bit of an oversimplification to say that Origins pursues the coldest aspects of our universe, but in some ways, it's true. So, if Lynx pursues the hot universe, Origins, in many ways, pursues not only the cold universe, but the story of the things that enable biology in the cosmos.

Mat Kaplan: Let me see if I'm putting this correctly as my understanding of it, by getting the temperature of this instrument that low, you have, signal to noise ratio is always so important. If your signal is also very low, something coming from a very low temperature object or structure, then your noise floor better be a lot lower than that signal.

Grant Tremblay: Exactly right. This is fundamentally a far infrared observatory, so, the problem with observing in the far infrared, even if you're in space, is that your telescope is a giant light bulb. Because at that temperature, basically, the blackbody curve or the Wien temperature would give you a lot of light output from the observatory itself. So, all matter with energy shines light. We're shining light right now, you just can't see it, because we shine in the infrared. But, yeah, so, the way to fix that is to make your observatory unbelievably cold. This is one of the reasons why James Webb will only observe sitting in its own shadow, cast by the sunshade.

Grant Tremblay: Origins not only has its own sunshade to keep it in a permanent umbra, but also has a mirror black plane that is orders of magnitude colder than what we'll have for James Webb Space Telescope. And that just enables just orders of magnitude improvement in sensitivity at far infrared wavelengths.

Mat Kaplan: Well, those are the four. Another thing that struck me as I looked at the four websites, all of which you can get to as we said, from, I love to look at the people, the teams behind each one of these. They're big teams in all four cases, and they are all stars. It's just amazing to see how much of the astrophysics community, and for that matter, the planetary science community is a part of at least one of each of these projects. It's an impressive commitment by all these people.

Grant Tremblay: These missions are the culmination of decades of dreams from so many around the world. It's not just a mission concept that NASA decided to fund starting in 2015, these each have decades of history behind them. And that means it's not just mission trades and level one requirements, it's human pursuit, it's human stories. It's loss. I've no doubt that some of us, maybe all of us will so-called "lose" at the decadal. But that's not just a mission being shot down, that's dreams being deferred for another decade or another two decades. The Lynx X-ray Observatory was previously had an incarnation in the International X-ray Observatory that so-called lost at the 2010 decadal. Before that, it was Constellation-X that lost in 2000.

Grant Tremblay: These are dreams from so many explorers around the world, and they have devoted so much of their careers and so much work to something that they might never see launch. I hope they all launch one day, but I could be retired, hopefully with my grandkids on a beach when Lynx launches one day. Who knows? These are not just observatories, they are human pursuits. I think they're some of the best things that our species does or can do, and each mission has an enormous history and story behind it. And ultimately, that story is a human story, it's not a technological story.

Mat Kaplan: Grant, I hope you're at this for a very long time because there are some fourth graders out there who I think need to hear from you. What is the status? When will we know the results of the 2020 decadal survey?

Grant Tremblay: Yeah. So, you and I are chatting on May 20th, I think this episode comes out next week, so, May 26th, 27th, right?

Mat Kaplan: Yes, on 26th.

Grant Tremblay: So, that means we are almost exactly one month away from the release of the decadal. I know that the decadal, the top level report is in final stages of referee from some incredibly accomplished luminaries who have been chosen as referees for that very important document, and on the day the decadal drops, the community, the astrophysics community around the world will hold their collective breaths and watch their press conference and open that PDF on the National Academies' website and go to the executive summary and read the top recommendations for the large and medium and small ground and space-based projects. And we will know what the future of discovery looks like.

Grant Tremblay: Look, I want to make something clear before we hang up because I don't want or The New Great Observatories movement to be seen as trying to tell the decadal what to do. The decadal is populated by a bunch of stone cold pros who are just phenomenally brilliant people, who will do right by our community. And I absolutely mean that even if Lynx is bottom ranked, or even if the idea of New Great Observatories, a constellation, is shot down. Or even if they recommend, "Let's take the decade off and do some tech dev to enable something really big for 2030." They will make the right decision for our community. I want to thank them all genuinely from the bottom of my heart for their effort, because it's, in many ways, a thankless but incredibly important job.

Grant Tremblay: Yeah, thank you to all the members of the community, but also thank you to every single human being who put so much blood, sweat, and tears into these four exquisitely beautiful final reports, which you can read on And let me just leave you with this, flagships die a hundred deaths. The Chandra X-ray Observatory, which I work on flight operations for, one of the greatest scientific missions in all of history has died a hundred deaths. It was canceled in the 1988 president's request, Reagan's budget totally zeroed it out. We had one chance to save the mission, that came down to a meeting between the NASA administrator and Ronald Reagan.

Grant Tremblay: It never ended up going to Reagan himself during a five-minute conversation between then NASA administrator, James Fletcher and James Baker, yes, that James Baker, Ronald Reagan's chief of staff, in the Eisenhower Executive Office Building, the NASA administrator said, "Look, we shouldn't cancel," what was then called AXAF, Chandra's sort of code name prior to lunch, "We can't cancel AXAF. Who will lead the world in X-ray astrophysics?" And that was appealing to the very cold war nature at the time. And with literally less than a minute of thought, Baker said, "Yeah, okay, all right, we'll just add it back in." Flagships die a hundred deaths. If one or all of us don't make it past this decadal, we'll be back again because these dreams don't die.

Grant Tremblay: Sometimes you got to plant trees whose shade you're never going to sit in, or whose shade you're never going to see for a long time. You need to invest in distant horizons. These are complex projects, these are scientific pursuits that aren't going to go away. This is not just momentary fashion. Are we alone in the universe? How does our universe work? These are persistent questions that will continue to lie before us, and so, I have no doubt that all four of us in some way will see the sky one day, and I just hope that I get to see it because what a new epic of discovery that would be.

Mat Kaplan: Grant, I hope that all four of these teams, including your own with the Lynx X-ray Observatory, recognize that they have in you a very fine spokesperson. You have joined the passionate spokesperson hall of fame here on Planetary Radio, and I think that should guarantee you a return visit before too long. Best of success in realizing these dreams that you share with these four magnificent teams for these four magnificent instruments. And I guess we will know in a matter of weeks. Thank you so much for coming here on Planetary Radio to share the dreams with us.

Grant Tremblay: Really fun to be here, Mat. Thanks so much.

Mat Kaplan: Astrophysicist and leader of The New Great Observatories coalition, Grant Tremblay. Stay with us for this week's What's Up.

Mat Kaplan: Time for What's Up on Planetary Radio. Here is the chief scientist of The Planetary Society, Dr. Bruce Betts. And he has been evaluating STEP Grant proposals as we hit the deadline for that brand new grant program for The Planetary Society. I guess now it goes into evaluation?

Bruce Betts: Yes. So, we're just, as this is coming out, the pre-proposals are due, so, all I've been doing so far is assessing to make sure that are all readable and such, now it'll go into an evaluation phase and figure out from whom we want to solicit full proposals for the science and technology, empowered by the public new grant program.

Mat Kaplan: Glad to hear it's moving along. What's moving up there on the night sky?

Bruce Betts: Ooh, nice segue.

Mat Kaplan: Yeah.

Bruce Betts: In the evening sky, we've got Venus and Mercury looking quite spectacular, but you'll need a clear view to the western horizon. And you want to look as soon after sunset as possible, just as it starts to darken, and Venus is super bright as always, and mercury is a bright star, but nothing compared to Venus. They will be only a half degree apart on May 28th. That's one full moon's width basically. So, it'll be a cool sight, Venus much brighter, Mars still up in the evening southwest looking like a kind of mostly brightish reddish star, and in the pre-dawn, we've got Jupiter and Saturn. Jupiter much brighter, Saturn, yellowish up in the east-southeast in the pre-dawn hours.

Bruce Betts: We move on to this week in space history, it was 50 years ago that Mariner 9 launched, Mariner 9, the first Mars orbiter would revolutionize our understanding of the Red Planet.

Mat Kaplan: Yeah, thank goodness, after getting all the bad views of Mars from its predecessors.

Bruce Betts: Yeah, it really showed the advantage of an orbiter versus fly-by, particularly when your fly-buys all happen to pass by the heavily crated region that looks kind of like the moon, and not the parts with giant volcanoes and giant canyons and outflow and blah, blah, blah. Cool stuff. We move on to the space fact.

Mat Kaplan: I'm glad you started to cough because I was about to head down to the bomb shelter.

Bruce Betts: So, anyway, the International Space Station has a commander at any given time, and the commanders rotate. A Russian national has commanded the station 29 times as of now, U.S. national, 28 times, Japanese national, as we'll come back to, commanded twice, and once for Belgium, British, Canadian, German, and Italian nationals.

Mat Kaplan: So, one for each of those at the end.

Bruce Betts: One for each of those, and acting as commander of the station.

Mat Kaplan: It's an international space station.

Bruce Betts: It is an international space station, I think, based upon their financial contribution to the program, it affects who's commander presumably.

Mat Kaplan: Seems fair.

Bruce Betts: Now, when did you command, Mat? And was that under your Martian citizenship?

Mat Kaplan: It only lasted three days because they pretty quickly realized it was just an Alexa device that I was talking through, that I'd stuffed into a jumpsuit and...

Bruce Betts: Well, that is an image that's weird. So, let's move on to the trivia contest. I asked you to name all the near-Earth asteroids that spacecraft have touched. How did we do, Mat?

Mat Kaplan: Some people missed the first one because I guess it was so long ago, and as you've pointed out many times on this show, wasn't intended to touch the asteroid, but did. Here's the answer from our poet laureate, Dave Fairchild in Kansas, "Eros started off the visits roughly 20 years ago, also stopped and saw Ryugu, who shot it like a wild west show. Itokawa got a touchdown from the Hayabusa craft. Bennu is the fourth of them, and of the four, it is the last." Correct, right? We got four?

Bruce Betts: Correct. Nicely done, nicely phrased.

Mat Kaplan: The first one, Eros, that one that happened so long ago that a lot of people missed, right? That was what spacecraft?

Bruce Betts: The NEAR Shoemaker spacecraft, Near Earth Asteroid Rendezvous, and it was designed as an orbiter, and indeed did orbit the Asteroid Eros, but at the end of mission as they were running out of fuel, they thought, "Hey, let's see if we can set our orbiter down on the asteroid," gave them better data on particularly fields experiments that require being up close and personal. And indeed, they succeeded, and the spacecraft survived after landing.

Mat Kaplan: Way ahead of its time. A couple more here, and then we'll mention our winner. Darren Richie in the state of Washington, he says he's looking forward to adding Dimorphos to the list next year, "But it will always be Didymoon to me," he adds.

Bruce Betts: Yes, to the target for the DART spacecraft, with its original nickname, Didymoon, and its official name, Dimorphos.

Mat Kaplan: Here's something I was completely unaware of, mentioned by Carlos Perez in Germany, Brazil is planning an asteroid mission called ASTER, and they're hoping to launch it later this year. It's really hard to find out anything about this. It is in the Wikipedia. I tried to go to the website of the Brazilian National Space Agency, didn't work. It's either doesn't exist or I had a bad URL or something, but apparently, yeah, they have this plan to send a small spacecraft, largely as the UAE sent Hope kind of as a inspirational mission and to give a lot of students some experience, but it's tough learn about. But, yeah, thank you for mentioning that, Carlos, and you had not heard of this either, had you?

Bruce Betts: Not that I recall.

Mat Kaplan: Laura Dodd in California, "My space imaginings of youth are being realized. Such an exciting era." Here's our winner, I was surprised, it's John Barille. He's been listening for ages, listening and supporting Planetary Radio, but he's a first time winner, and he got all four of them right. Eros, visited by NEAR Shoemaker 2001, Itokawa, visited by Hayabusa 1 in 2005, Bennu, OSIRIS-Rex, 2020, and of course, Ryugu, which was reached by Hayabusa 2 in 2019. Congratulations, John.

Bruce Betts: Yay.

Mat Kaplan: It's about time. We are going to send you a Planetary Society KickAsteroid rubber asteroid. And what could be more appropriate?

Bruce Betts: Nothing.

Mat Kaplan: True enough. I have two more. Perry Metzger in New Hampshire, "Touchdown missions on rubber asteroids are substantially easier than those on near-Earth asteroids. It's also possible to use rubber asteroids for touchdowns in living room football games."

Bruce Betts: Indeed, they are flexible that way.

Mat Kaplan: Jean Louin, our other pretty much weekly submitter of poems. I don't have time, we don't have time to read the entire thing, but here's the last stanza from Jean, "That list is of the ones we touched, but there are many more, to twist a phrase from Obi-Wan, 'Those are not the roids we are looking for.'" I like that. I like it. We're ready to move on.

Bruce Betts: Back to space station commanders, on April 27th, 2021, Akihiko Hoshide assumed command of the ISS, becoming the second Japanese astronaut to command the station. Who was the first? Go to

Mat Kaplan: You know how this works, you've got until Wednesday, June 2nd, at 8:00 A.M. Pacific Time to get us this answer, and I wish you luck because somebody's going to get another Planetary Radio T-shirt, and they're cool. I was wearing the first-generation shirt earlier today, this is the third, third and a half, anyway, the current shirt is easily the best. And Bruce is wearing the first generation shirt as well. What a nice coincidence.

Bruce Betts: Yay.

Mat Kaplan: Yeah, I got a special place in my heart for that first one.

Bruce Betts: Nostalgia.

Mat Kaplan: We're done. Get us out of here.

Bruce Betts: All right, everybody, go out there and look up at the night sky and think about the longest book you ever pretended to read. Thank you, and good night.

Mat Kaplan: Oh, there were several in high school especially. I'm really sorry, Mr. Tobin, for giving books, but thank you so much, CliffsNotes.

Bruce Betts: Oh, I love Uncle Cliffs.

Mat Kaplan: That's Bruce Betts, the chief scientist of The Planetary Society, who would never have considered not reading the assigned book back in high school or any other time, because he joins us every week here for What's Up.

Bruce Betts: You know it, CliffsNotes' aficionado when they refer to Cliff's Notes, which is the proper term rather than Cliff Notes.

Mat Kaplan: Planetary Radio is produced by The Planetary Society in Pasadena, California, and it's made possible by its members who want to see far beyond the limits of their eyes. It will all become clear at Mark Hilverda is our associate producer, Josh Doyle composed our theme, which is arranged and performed by Pieter Schlosser. Ad astra.