NASA's Chandra mission went to space 25 years ago this week. And while the more spectacular visuals from Hubble and Webb might more easily grab our attention, Chandra has been plugging away all this time, completely blowing astrophysicists' minds. That is because Chandra revealed to humanity all sorts of information that we could never have seen from Earth before. And today, I get to speak to one of the astronomers working on it. Welcome to T-minus Deep Space from N2K Networks. I'm Maria Varmausis. Our guest today is astrophysicist Jonathan McDowell. In his day job, Jonathan is an astronomer at the Center for Astrophysics, Harvard M. Smithsonian, working on the Chandra X-ray Observatory Space Telescope. But it's his out-of-hours work that attracts a lot of attention too. Jonathan has become the leading voice in the United States for chronicling the history of the space program and keeping track of space debris. How does one become the keeper of all things space debris? Planet 4589 has the answers. I'm Jonathan McDowell. I'm an astronomer at the Center for Astrophysics, Harvard, and Smithsonian. And for my day job, I hunt for black holes and help with the running of the Chandra X-ray Observatory Space Telescope. But I have another life in which I have for decades been chronicling the history of the space program and maintaining the website with the list of all the rocket launchers and all the satellites and figuring out what they do and trying to provide an objective and global view of humanity's push into space, both with people and robots. And I find that a lot of the coverage, particularly in the US, is very US-centered and is very -- NASA talks about NASA, but it doesn't talk about non-NASA stuff and so on and so on. So, I felt there was a gap in both being objective and being global. Many people may also know you by your handle, Planet 4589. That's -- as soon as I see that handle anywhere in an article, I'm like, "Oh, I know who this is." My first question is, "How do you do all this?" You have in your bioorbital police, and you are the source of information. When all these different bits of debris were falling, like in Saskatchewan and whatever, I knew. I said, "Unless you have verified it, I don't know what it is." So, how do you do all this? Well, for a start, I depend very heavily on the work of the US Space Force and other agencies and on amateur observers who collect orbital data. My special skill is in putting it all together and doing some math to interpret and tie the strands together. And so, part of it is that I've been doing this for 50 years since I was a teenager. When an obscure old satellite comes up, "Oh, Cosmos 1408. Oh, I know that one." That's amazing. And so, it's having the information at my fingertips, having a mental map of all the stuff that goes on, having the math skills to do some relatively simple orbital mechanics to tie what people are saying to what's actually happening. And having about 100,000 lines of code, of C code that I use to do various tasks and automate various tasks. And everything I do is optimized, so it takes me the minimal amount of time to deal with something because I do have another day job. So I've got it down to a fine art where 95% of everything is automated, and then I can go in and run a specialized program to kind of plot up, for example, the ground track of a re-entering spacecraft over Canada and do that very quickly because I already have the code canned and I know what to do to make that plot. And so, it's really all about... People make fun of my website because it's so nice... I love your website! No, unironically, I love it. I'm glad. Yeah. And I think it's... The younger generation, right, they're like, "Well, you're barely using CSS." I mean, I diverted that a few years ago before then it was really 1994 type of web stuff. But the thing is that a lot of it is generated by C code and updated. And so, on the Jonathan Space Report itself, it's actually a text file that I type in and as I type, it appears on the web. And so, none of this, you know, intermediary. And all of that is just making it really, really fast for me to get the content out there. If you want pretty, my data is CCBY, it's Creative Commons. You can copy the data and put a pretty interface on it to make yourself happy. But I don't have time to make it pretty. I'm optimized for that. I don't have time. Yeah. No, I was going to say, I don't doubt it because to me, it is the sheer amount of information that you are putting out is... I'm not surprised it's automated. I would never imagine that was all manual. That would be, I think, impossible. Well, to be fair, the actual list of 60,000 satellites, each line there is typed by hand. At some point, yes. At some point since the 1980s when I was doing this. So it's not all of... There is a lot of manual. But it's kind of just... What do I do and what do I not do? Yeah. I imagine you must have many anecdotes over the course of years of how your information has proven helpful to people, not just randomness like me going on Twitter and going, "Oh, what was that?" I mean, you are cited all the time. Again, and this is not your day job. It's just amazing. Any anecdotes come to mind because I'm just really curious. Well, for example, there was the time when the Space Command lost a European astronomy satellite for a few months and they were putting out extrapolated positions for it. And then the asteroid observers found a new object in Earth orbit. "Oh, this isn't an asteroid. We don't want this." And I figured out that it was actually this integral astronomy satellite and it had made a maneuver and Space Force hadn't noticed it made a maneuver. They were still looking for it in the old orbit and issuing data as if it were still in the old orbit. And so I was able to put the right people in touch with the right people and clear up the error. So there's a few like that. There's been a few cases where, again, things that were originally catalogued as asteroids and then they maneuvered. Give me more of that too. I was able to figure out which lost spacecraft it actually was. So that's some of the stuff that's most fun. And then I get informal contacts from various bits of the government who go, "Yeah, we can't say it, but we use your stuff." So that's very gratifying. And I think if people like to be able to quote my open source stuff, even if they have insider knowledge that they're not allowed to, they can at least quote me. So that helps. I respect that. The fact that it's open source is just such a service truly. And I'm a big fan of open source, so I'm just kudos for that. So okay, I want to switch gears to the pub question of where does space begin? You sent a really very pertinent piece of research or your own work, I should say, about that very question, which people like to argue all the time. So can we put this one to bed finally once and for all? I wish. I mean, the Elba thing is, I'm fascinated by boundaries. And this is not the only boundary that I, you know, where to draw lines, right? Because as humans, we need to categorize things. We need words for them. And we need to define those words. But also, you know, the English language is a word doesn't have a single definition. There are multiple senses of every word. And so it's okay for space to be used in multiple senses, and indeed it is, right? We have like non-space senses of space, like I need some spaceman and, you know, living space and so that kind of thing, right? So, but even outer space, right? How you choose to define it may depend on what purpose you have. And so it's not important to go, this is the definition of space. What's important to go, this is the definition of space I'm going to use. You and I are both going to use for this purpose, right? And so for the purpose of talking about satellites, I made the argument that the boundary of space should be at 80 kilometers, not at 100 kilometers as some people have suggested. And what's interesting about that is maybe a lot of people talk about the Karman line and talk about the Karman line being 100 kilometers. But in fact, when Karman first calculated it, he got 84 kilometers. So, so, and then the 100 was just a round number picked up later because I think because in the context of the 60s, people were not confident that the upper atmosphere was stable enough to make it a well-defined boundary using Karman's argument, which is when does lift or drag become more important than orbital dynamics? And so, you know, I went back and looked at that with modern atmospheric models. I went, oh, well, actually, no, although, you know, the atmosphere at 300 kilometers is bumping up and down a lot, the atmosphere at 80, 90, 100 kilometers is actually pretty stable. And so for a lot of different atmospheric conditions, when you ask this question, where is gravity or atmosphere more important? It comes in the like 70 to 90 range at worst and never goes out to 100. And so then if you look at where the satellites actually go, there are a few satellites in elliptical orbits which dip down to 85, 80 kilometers. But whenever they dip down to 70 kilometers, they don't come out again. And so that's a pretty hard lower boundary from the empirical data. And so the fact that the empirical data and the theoretical data agreed meant that, okay, this is nice, right? It's coming at it from two different angles, and they're both giving me the same answer. And so that gave me some confidence that, okay, this is a pretty solid result, that multiple lines of argument are leading me to, it's more like 80 than 100. And if you arm wrestle me, I mean, if you want 85 or even 90, okay, I can't argue against that. But 80 is sort of the middle of the range. And 100 is too high, in my opinion. Other people have different opinions, and that's fine. And I think, as I said, the most important thing is to say which definition you're going to use. And if you want to use 100, that's fine. But don't say that some other definition is absolutely wrong, even though I think 100 is kind of wrong. Don't say it's wrong, even though something might be wrong. Let's say it's not a physically motivated choice. But for some purposes, it may be the sensible choice to use. I'm open to that. We'll be right back after this quick break. I think that's a very fair answer. I often think people say 100 because it's a number that's easy to remember. I think it really comes down to that for a lot of people linguistically anyway. It's just 100. It's a round number. Here's my thing, Maria. Now the question is, what do you pick on Mars? Oh, my goodness. What a great question. What do you pick on Mars? What is the common line for my right? And so if you just go with round numbers, you know, you're not really helped. Whereas if you have a physical argument, right, then you can go, well, let's do the same calculation for Mars that we did for Earth. Where does gravity and air dynamics, you know, and it's a little like, I don't remember the number, but it's like 60 or something like that. So you can do an equivalent calculation for any planet with an atmosphere. Right? The moon's a little harder. So if you are standing on the moon, are you still in space? Well, arguably, yes. Did you lightly jump on both feet? Even if you don't, right? Yeah. So that's a bit, so I'm still struggling with what to do about that. But I think that having a physically motivated definition for Earth lets you extend that definition to other worlds. And so it's more robust in that sense. Okay. I love that answer. It is, it is, it's also a framework answer. So it's setting us up for success in other worlds. It doesn't let people argue about whether or not these space turds and flights are space or not. That's everybody's favorite plub arguments. But I feel like I like your answer better, to be honest with you. So I think it's very fair. And to be clear, yeah. I pick AD for all my work. And so I do count these space tourists on Virgin Galactic as having been in space. And I call them astronauts in that particular sense of the word. I think that's great to hear. I'm always curious where people fall on that one. Again, it's just a pub question, really. I'm always fascinated by it. That's the important thing, right? Is answering the pub questions. Yeah. That's true. It's true. All right. So I'm going to switch to the other thing that you do all day, which is Chandra. So I imagine things are still very busy at this wonderful institution. I mean, it feels a little overly simplistic to say, well, what's going on right now? Given that I'm sure a lot of things are going on at once. Any sense of what you can tell me what's happening right now? So Chandra is the x-ray cousin to the Hubble. And it was launched in 1999. And I remember standing at the pad, next to the pad, watching it go up on a pillar of flame going, please don't blow up. And it was, you know, I've been working on it several years before that. So I've been working on Chandra for a long time. It sees the hot universe that Hubble and James Webb can't see. And so if you want to study some region of space, you need both the Hubble and James Webb data and the Chandra data to get the full picture of what's going on. If you don't have both, then you're really, you know, you're missing a significant part of the story. So we have, you know, the particular things that Chandra is excellent at seeing are the freshly baked elements from supernova explosions. And we can, so here's a couple of solar masses of newly made iron. Here's some silicon. We can see it in the shock wave as it expands outwards at 20,000 kilometers a second and glows at a million degrees. The other thing we're really great at is looking at what I call gravity reactors. When you have a large source of gravity and gas falling into that, it gets squeezed by that gravity and gets hot. Now if the thing at the middle is a supermassive black hole, we'll say, once the matter goes into the black hole, you can't see it famously. But you can see it when it's being squeezed on the way in. And it gets squeezed to millions of degrees. And so it puts out X-rays instead of ordinary light. And so we can very easily spot where all the black holes are. We've released a catalog. It's mostly an updated version of our source catalog that has about 300,000 black holes. And so that's been really great to be able to map out where are the energetic events in the universe, basically. And we've been pushing that further and further. When I started on channel, we never thought we'd be able to see quasars black holes at early stages in the universe. We thought we'd have to look at the nearby ones. But now with some good tricks, we've been able to see ones at Regis of Six, which is not long after the Big Bang. And so, again, we're being complimentary to the discoveries that James Webb is making about that early phase in the universe. One of the big questions, right, is when did the lights turn on? And were the lights that turned on first, the fusion reactors, the stars, or the gravity reactors, the quasars? And so that's an ongoing question that we're trying to figure out. Did the formation of the stars in the galaxies then cause matter to fall into the middle of the galaxy and feed the black hole and turn them on? Or did the black holes form early and the energy input they put into the surrounding galaxy trigger star formation or affect it? And so that interaction is very complicated. And we've got the first few objects that we've studied and we need hundreds more. So there's a lot of really groundbreaking science still to be done with this 25-year-old telescope. And it's got a lot of life left in it, at least another decade I've heard. So lots more to be done. That's right. So the thermal insulation is getting a little crinkly and there's a bit of fog on the lens and so on. But I know exactly. I'm definitely crazier than I was 25 years ago. And so, but we're still doing the demand for Chandriss as high as ever. We're doing several observations a day. So each two-day orbit of the Earth, it looks at maybe four or five different things. And so the results just keep rolling out. And there's nothing obvious that's going to break, that's going to stop it working. One day, right, it'll stop talking to us. Some power supply will blow or something like that. But there's no reason for that to happen in the next few years, I think. So I'm hoping that we're hoping that as long as the funding support is provided, we can carry on delivering great science. And I think we run a leading mission and we're very proud of the work that we do with Chandriss. Is there anything else that we should make sure that we -- you've got an audience right now, I'm sure you're used to it. But if there's anything that you wanted to say to the audience before we close out, the floor is yours. Anything you want to mention? Well, I think one thing, there's a couple of things that I'm really pushing on right now on the space side. One is the risks associated with uncontrolled re-entries. And so we've seen that with the dragon trunks crashing down. We've seen that with the piece of the ISS that hit the house in Florida. And I think we really need to look at the regulation of these re-entries. And so, you know, let's not do that. Let's bring them down under control, even if it costs a little more money. The other thing I'm really pushing on is regulation of deep space activities. So we're entering a new era in space exploration, where the frontier is moving at. And the frontier used to be kind of lower-thorbit and beyond that, you know, only the super power has played. And now the frontier is moving out to the asteroid belt. And everyone from developing countries to startup companies is going to be sending stuff to the moon and Mars. And it's going to become just part of the general playground. But it's much less regulated than Earth orbit. And so we need to require things like make public your trajectory, you know, say what you're doing, say, you know, have some kind of flight plan, right, in the public domain so that, so that there's transparency, again, go back to this open source thing, right? Let's have some transparency in the process here. And the commercial companies don't want that, of course. They want to do things like, I want to go to an asteroid, but I'm not going to tell you which asteroid I'm going to. And yeah, space is big, but no, let's at least have a public flight plan. So I'm making that argument in various forms. And the other area that I think people should know about, and that plays into both of those other two ones, is the development of the commercial space activity in China. We hear a lot about, you know, SpaceX and commercial stuff in the US, but China has really made a shift in the last five years or so towards lots and lots of startups that are not, you know, associated with the government. They're really going capitalism in a big way. And so you have all these new players that are not then used to the norms we have. They're not going to send their identifications of which satellite they are to the US Space Force because, you know, China. And so we need some better international way of coordinating space activities that brings the Chinese commercial sector on board. And that's absolutely critical to safe use of space, sustainable use of space in the decade to time. That's it for T-Minus Deep Space, brought to you by N2K Cyberwire. We'd love to know what you think of this podcast. You can email us at space@n2k.com or submit the survey in the show notes. Your feedback ensures we deliver the information that keeps you a step ahead in the rapidly changing space industry. T-Minus Deep Space is produced by Alice Carruth. Our associate producer is Liz Stokes. We are mixed by Elliot Peltzman and Trey Hester with original music by Elliot Peltzman. Our executive producer is Jennifer Iben. Our executive editor is Brandon Karp. Simone Petrella is our president. Peter Kilpey is our publisher. And I'm your host, Maria Varmasus. Thanks for listening. We'll see you next time. [MUSIC PLAYING] . 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