Planetary Radio: Space Exploration, Astronomy and Science - A Space Station Crashes to Earth

Episode Date: March 28, 2018

By the time you hear this week’s episode, China’s Tiangong-1 may have spectacularly re-entered our planet’s atmosphere, raining metal on an unpredictable location.  The Aerospace Corporation’s Bill Ailor, an expert on space debris, tells us there’s little to worry about, but bigger challenges are ahead in low Earth orbit. Bruce Betts also has his mind on the small space station.  Emily Lakdawalla is back from the Lunar and Planetary Science Conference with much news to share. NASA finally has a budget for the year already underway!  Casey Dreier breaks it down.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

A space station crashes to Earth, this week on Planetary Radio. Welcome, I'm Matt Kaplan of the Planetary Society with more of the human adventure across our solar system and beyond. Has it happened yet? As we finished producing this week's show, Tiangong-1 had not yet re-entered Earth's atmosphere, creating a magnificent firework show that would leave souvenirs on the ground. No one knows more about space debris than the Aerospace Corporation's Bill Ehler, and we've got him on this week's show. He'll also tell us about the crowded sky

and will review the status of planetary defense against near-Earth objects. The Chinese space station is also on Bruce Bett's mind. We'll talk about it and much more on What's Up. NASA finally has a budget for the current fiscal year. Casey Dreyer will bring us the highlights. And we begin this big episode with Planetary Society Senior Editor Emily Lakdawalla. Emily, welcome back from LPSC. I know it's one of your favorites every year, the Lunar and Planetary Science Conference. How tough is it to decide what you're going to be able to report on?

Well, it doesn't help that I want to clone myself every year so that I can appear in multiple rooms. It does help that there are a lot of people who have the same problem. And so we all tweet for each other. We can follow notes. And this year, I actually started an effort to do collaborative note-taking. So one of the blog posts that I don't have up yet, but which I hope to have up soon, will be a link to some of those collaboratively taken notes. So you can actually see what people wrote down while they were in the sessions. And you've recruited some great guest bloggers too, haven't you? Yeah, that's right. I've already got a post up by Jake Robbins about Mars downslope mass wasting

processes. And I've got a few more in the pipeline, one on Galilean satellites, one on the moon. There's a lot of good stuff coming. Let's talk about your post that I just read a few minutes ago. Titan is terrific. And you give plenty of evidence for that. But even here, you had to sort of be picky about what you could report on. You know, when you have a mission that's operated for 14 years, like Cassini did at Saturn, a lot of the updates you see at conferences are kind of incremental reports on how a particular line of research has advanced a little bit since the last meeting. And so what I was really more drawn to were a couple of the more out there presentations in the Titan session. Two of them

started off whole new fields of study for Titan. So one of them was by Morgan Cable, and she was talking about molecular minerals on Titan. Now, if you're a geologist, a mineral is a naturally occurring crystalline substance with an orderly arrangement of its atoms and a fixed chemical composition. And on Earth, those are made with things like iron and oxygen and silica and magnesium. On Titan, they'd be made of small organic molecules. And she was doing experiments in the lab with molecules like ethane, acetylene, propane, hydrogen cyanide. These are all things that exist on Titan's surface and which make OSHA just throw up their hands and scream about all these materials that are in the laboratory.

But she's doing some pretty interesting work looking at the kinds of crystals that you'd expect to form the organic minerals on Titan and finding that some of them have some pretty interesting behavior, like how they might expand quite a lot when they warm up, which would cause tectonics on the surface. So that was really interesting. And maybe even forming rings around Titan lakes, rings around the bathtub, so to speak. That's right. We've seen these light deposits around lakes on Titan. We don't actually know if they're deposits, but they're these light rings around the lakes and they could be evaporate deposits maybe, or there might be something else, who knows. So that's Titan petrology. So now let's talk about a different

kind of science, Titan seismology. So Mark Panning gave a talk about what the Dragonfly mission might be able to do with a seismometer on Titan, listening for ice quakes caused by Titan being flexed as it goes around Saturn in its orbit, and what you could learn about Titan's interior and the thickness of its ice shell from the different kinds of waves that you'd expect to receive at a seismometer on a future landed mission. I guess that just could happen if the Dragonfly mission moves forward? It absolutely could. And Dragonfly is planning to take a seismometer. And one of the things that Mark was asking was, what would it detect? Would it be able to detect a seismometer, and one of the things that Mark was asking was,

what would it detect? Would it be able to detect ice quakes or would it only hear noise from the wind? Because Titan has a thick atmosphere and wind. And the answer turns out to be, yes, it should be able to detect ice quakes. You don't need a ridiculously sensitive seismometer like the one that Mars Insight has.

You could get by with a good quality, but not insane quality seismometer and get some good results on the ice thickness on Titan. Great artist concept of Dragonfly doing its thing, this drone on the surface of this moon with a thick atmosphere and such interesting surface chemistry. surface chemistry in Emily's blog, which is a March 21 entry at planetary.org. Let's go ahead and mention the one other story that you had room for here. And this seems to indicate that hydrogen cyanide, that nasty stuff, which is in Titan's atmosphere, might have something to tell us about the origin of life on Earth. Yeah. So this is kind of a complicated and interested and speculative story, but I'll try to explain it. So hydrogen cyanide is a very simple gas. It's hydrogen, carbon, and nitrogen all bonded together. And it exists in Titan's atmosphere. All the nitrogen stuff in

Titan's atmosphere, in order to make it, the sun has to break up molecular nitrogen. If you remember from your high school chemistry, nitrogen bonds to itself with a triple bond. It's a very strong bond and it's hard to break up. It turns out that it's easier or it's more likely to break up if you have two different isotopes of nitrogen bound together, nitrogen-14 and nitrogen-15, than if you have the same more common isotope. And what that means is that hydrogen cyanide is heavy. It has more nitrogen-15, more of a heavy isotope. And because hydrogen cyanide is implicated in some of the chemical reactions that are thought to happen in a prebiotic atmosphere where the kinds of things that would make

the primordial soup that you would imagine would be a place for life to begin, you would expect the earliest kind of life that used hydrogen cyanide to also be isotopically heavy, would have heavy nitrogen. And so what does this all have to do with Earth? Well, if Earth had the same kind of early atmosphere, which we think it might very well have, and life got started in the very early Earth with a lot of heavy hydrogen cyanide in the atmosphere, then in fossil records of the Earth, even if there's no evidence whatsoever left of any kind of life form that existed, it's all been crushed and formed into minerals. But still, any nitrogen in those minerals would have that isotopic signature, would have that heavy hydrogen. Chris Glein was suggesting that maybe if we look at Earth's very earliest rocks and we go hunting

for this heavy nitrogen signature, that might be a sign that early life existed at the time of those very ancient rocks. There's a lot of if, if, if, if there, but if the signal existed, it could be a very strong signal potentially. So it's worth looking for. More indications that by exploring the solar system and beyond, we are potentially learning more about ourselves. Emily, thank you. There's so much more at planetary.org than this one blog post that you put there on March 21st. And we'll look for more from you and from those guest bloggers that you mentioned. That's right. I'll have many posts up this week. Emily Lakdawale is the senior editor for the Planetary Society, and she joins us from time to time here on the show. On now to Casey Dreyer, the director of space policy for the Planetary Society,

with an update on what looks to be a really good NASA budget. Casey, welcome back. Big news about the budget that has just been signed by President Trump within the last few days. Is this may be the best year for US investment in science in a decade, if not more. Very impressive. All right. Now, let's stick to NASA, although Noah and others you point out do pretty well as well. What are you most happy about in the NASA budget? Where do I begin? Big picture, NASA got $20.7 billion. That was the compromise. The House had originally proposed $19.8 billion for NASA, $19.9. The Senate had proposed $19.6, and the compromise was $20.7. Now, that's a compromise everyone can get behind. The pie got bigger, so everyone's slice got to grow, and no one really had to pay the price. got to grow and no one really had to pay the price. Planetary science, obviously our main focus here at the Planetary Society grew to its largest budget, I think in history, it gets a little hard to go out way back in time to the 70s just because of the programmatic differences

between the programs. $2.2 billion for planetary science. It was not that long ago that we were talking about 1.5 and just struggling to get to that after a decade of cuts to planetary science. So a spectacular number for planetary science. It supports Europa. It supports Mars. They have a lot of planetary society priorities are included in there, including recommendations that we made last year for investing in Mars sample return and a science orbiter, extra $75 million for that. NEOCAM, that asteroid hunting space telescope, lives to develop another year. It gets a minimal amount of funding to keep that mission alive.

Support that was an important win for us. And then, of course, there's just broad support in all of the sciences grew. NASA science grew to over $6 billion this year. It's just a spectacular number. What else surprised you in this? Earth science. The Trump administration and the Trump campaign was not exactly a welcoming place for earth science and climate research. They had proposed, I would even say, an unexpectedly modest cut to earth science for this year in the 2018 budget. And what ended up happening was Earth science got exactly what it did last year,

did not lose a penny. And of the five missions that they proposed to cancel, four of them were fully funded for 2018. The fifth one was actually just canceled by NASA on its own due to cost overruns, basically. So Earth Science did great, kind of maintains its peak funding for the third year in a row at $1.9 billion. We also saw a second kind of surprise mobile launcher, a new mobile launch tower for the Space Launch System that had been recommended by an aerospace safety advisory board to NASA, and it would help minimize the time between the first launch of the SLS in 2020 and the second launch of the SLS,

which is an upgraded version, the Block 1B, which needed significant tower upgrades to handle the taller rocket, the new umbilical connections, all that kind of good stuff. So instead of upgrading the existing tower, NASA gets a second one. Casey, it was only this morning as we speak that we learned from NASA that the JWST, the James Webb Space Telescope, is going to be delayed even further. Do you see that having any effect on spending this year and in the next few years? Well, spending this year is now set. So this budget that just passed actually kind of retroactively applies to the fiscal year that began in October of 2017. So we're already halfway through it. In that budget, they gave the requested amount to James Webb, about half a billion dollars. And they also gave money to what is meant to be the

successor of James Webb, the WFIRST space telescope. Let me see if I can do this off the top of my head. The Wide Field Infrared Survey Telescope. Well done. That's it. That's what I get paid to do, Matt. And this has been actually proposed to be canceled next year in the 2019 fiscal year by the White House. Now, there's been a campaign to try to restate that funding, and Congress notably included $150 million for 2018 this year

to continue that mission. So not exactly a big statement of support for cancellation by Congress. But now that James Webb is blowing its budget again, that difference, the idea that James Webb, the cost of that would diminish over time to just transfer into operations, that would open up this new funding wedge, as they call it in NASA parlance, to be used by WFIRST. Now that James Webb will likely not give up that funding for at least the next couple of years, James Webb will likely not give up that funding for at least the next couple of years. That makes it a lot harder to begin working on WFIRST in earnest, even if it weren't going to be canceled. space telescope while they rush to try to fix the issues with their upcoming space telescope that they need to get up, launched, and getting data as soon as they can. Wow.

The one sour note in all of this. If you'd like to read about all of the great news that Casey has just talked about and much more, it's in his blog entry for March 22 of this year. It's even been updated to indicate how the White House has signed it into law. It's all there at planetary.org, including a terrific table that traces the development of this budget. Casey, thanks very much. I look forward to talking to you next week, the first Friday of April, when we'll be joined by Jason Callahan for that month's Space Policy Edition. Absolutely, Matt. Let's accentuate the positive until that point.

Casey Dreyer, he is the Director of Space Policy for the Planetary Society. Stay with us in just a few moments. We'll talk about a big piece of metal that's coming down really soon, if it hasn't already. It isn't every day that a space station crashes back to Earth. But avoiding space junk that is still in low Earth orbit is a daily concern for everyone from the operators of the smallest CubeSats up to the astronauts and cosmonauts on the International Space Station, where something as small as a loose screw could ruin your whole day. Bill Ehler has been studying our crowded skies at the Aerospace Corporation for 44 years. He was chief engineer for the company's Center for Orbital and

Reentry Debris Studies and continues his long tenure as an aerospace fellow. Some of you will remember him because of his parallel involvement with planetary defense, making sure we find, track, and, when it becomes necessary, deflect a comet or asteroid on a collision path with our world. Bill recently spoke to me from his office on the sprawling aerospace campus in Southern California. Bill, welcome back to Planetary Radio. It is great to get you back on the show. I'm only sorry that we're not doing this from a planetary defense conference because you know I've had the best time at the two of those that I've attended. Matt, it's good talking to

you too, and I'm glad you've enjoyed the conferences. We'll get back to that, the PDC. I didn't make it to the last one, but I sure hope to get to the next one. Because there's something much more immediate for us to talk about. Something is going to be falling out of orbit in just the next few days. In fact, by the time a lot of people hear this program, it may have already happened. Tell us what we should expect by the re-entry of this Chinese space station. It certainly is coming down, that much we know. And it will re-enter the atmosphere at some place we don't know where exactly and probably won't know very well, even when it does come in. So it'll be quite a spectacular view for some lucky people if they have to see it. It's a reasonable chance nobody will see it at all. So there's going to be quite

a show in the sky for the people who are not far away. Oh, it'd be magnificent. The way these things work is, you know, it hits the atmosphere, the friction with the atmosphere at those high altitudes that gradually heats it up. It comes apart into big pieces first and then little pieces and things shed off. And it's like a firework show. It's really a beautiful thing to see in the last couple of minutes. That's what sort of makes it different than a meteor shower. Should I be hoping that I'll be under this to catch that show? Or would it be much better if it happens far away from any place inhabited? We hope it happens somewhere where there's nobody around. I mean, if you happen to see it,

there's a real good chance that the debris isn't going to fall on your head. So that's one good thing. But clearly on these kinds of things, there may be some hazardous fragments that come down and survive. So it'd be better not to be under the final footprint. So I've read differing accounts in the media, some that say, yes, some fragments are likely to survive and others that say, no, we probably will see it all burn up in the atmosphere. It sounds like you're saying the former is the case that probably some of this space station is going to make it down to terra firma. Oh, yes, I think so.

Generally, objects this size, we would expect to see anywhere from, say, 10 to 40 percent of its mass on orbit to reenter and survive. It just depends on what it's made of and so forth. But there's a lot of evidence that these kinds of things, that fragments of these things survive and will hit the ground. of these things survive and will hit the ground. This is not the first space station or large object in orbit that has come back in, well, in this case, in kind of an uncontrolled way, right? I mean, what have we seen in the past? Oh, that's correct. This is an uncontrolled reentry, which means that the atmosphere just sort of drags it down and it comes in wherever it pleases. A control reentry would be one that brings an object down into an area where it's definitely not going to be a hazard. Uncontrolled reentry is probably the

largest one that's ever occurred was the United States Skylab, which came down in 1979. And that one weighed about 69,000 kilograms. That's a big object. So Taoyang Gong is around 8,000 to 9,000 kilograms. That's a big object. So Taoyang Gung is around 8,000 to 9,000 kilograms, so much smaller. But generally, a control reentry would be, say, for example, a space shuttle. Space shuttle was designed to land in a particular place. And so basically, you command a rocket on board that object to execute a deorbit burn, and that will place it in a particular area on the planet. And a general place for dumping things is in the South Pacific. Just because it's big and wide open and not very many things for it to fall on other than water and fish.

That's exactly right. That's exactly right. Why would China not have had this re-enter in a controlled way. I've read that they may have lost control or lost contact with the space station. Yes, that's what I've heard as well. So basically, if having a controlled re-entry requires a couple of things. Number one, you need to know what attitude your vehicle is so you can make sure when you fire that rocket, it's fired in the right direction. And then secondly, you need to have a rocket on board that you can fire. It's not clear exactly what happened, but it looks like they lost control of this particular one. So you can't, they couldn't control the attitude to do a burn, which would mean that if they did one,

it would still come down some random place so that it doesn't buy you much. Also, you would need some propellant on board to do that. We really don't know what the circumstance is right now. Talk more about the factors that make it so difficult to determine when and where an uncontrolled object like this will return to Earth. For an uncontrolled object like this that's coming down, even up at the altitudes where the space station is, for example, there is just a little bit of atmosphere up there. And that is slowly bringing down the space station. And if we didn't do a burn every now and then to raise it up a little bit,

it would come back down in some period of time. And same thing for this particular one. It just slowly coming down. It's coming down through the upper levels of the layers of the atmosphere. And you start getting in a little closer, the atmospheric density variations begin to have a greater impact or a greater effect on the eventual reentry time and so forth. And if you have a solar storm or any kind of solar activity like that, or there are other physical things that can happen that will affect the atmosphere. So anything like that will change the eventual reentry time. For example, if you have a solar storm, it actually causes the atmosphere to bloom a little bit. It sort of rises up.

It becomes a little bit more dense at some of these higher altitudes. And those kinds of changes will, of course, affect the object that is coming down. This thing's traveling about four miles a second. It does see a little bit of drag and those accumulative effects will affect where it comes in. Space stations are, of course, not aerodynamically designed because they don't have to deal with aerodynamics. So they tend to have bits and pieces all over them, and they're odd shapes. How much does the shape of an object affect this atmospheric drag? That's an excellent point, and more, the orientation also affects

where something's going to come down. For example, if you can imagine an arrow in space, if you had the arrow pointing into the wind, it doesn't see so much. Even down on Earth, it will go a fairly good distance. But if you turn the arrow broadside, then that means that it'll slow down much quicker. Same thing happens in space. And as a matter of fact, Skylab, when it was coming down, there was a little bit of control at that time of the attitude. And so the body was actually rotated to make it slow down more in some areas.

And that was used as a way of controlling what orbit it came down in so that you could have a reentry that came down with more inclined to come in over water. So with this object, Tiangong-1, how long before actual reentry will we know more? I mean, we'll be able to say, yes, it looks like it's coming down in the South Pacific or the Indian Ocean or, for that matter, Kansas? We may not be quite as precise as that even, I hate to say. What's required to do a good job of predicting is to get information or have some observations, shall we say, late in the reentry.

So as many observations as you can get is helpful. And then, of course, as you get one that's, say, a day or a few hours away from the actual reentry point, that can help you refine it even more. And then even then, there's a certain amount of uncertainty. And, you know, again, how the object is going to, you know, how it's going to be oriented. It may be tumbling. It may be coming in broadside. You just don't know. And then also there are atmospheric variations that will affect things. So getting a very precise impact location is nearly impossible. And let me mention that the reentry location is one thing. The second thing is that there's a lot of uncertainty in how that the eventual footprint, how the object breaks up, where those pieces will be distributed on the ground. So there's even more uncertainty in that.

I assume that these could be spread over quite a wide area. Yes, indeed, they can. As a matter of fact, they're generally spread right along the ground track of this thing. So namely, if you look on these maps, you see there's a line that says this is where it is over the earth. So the debris will fall somewhere along that ground track. And it'll be basically a long, thin thing, maybe 400 or 500 miles long and maybe 30 miles wide. The width sort of depends on what winds are happening and doing to debris as it falls. The length depends on how much material is in the particular object

and what the breakup sequence is. You mentioned observations a moment ago. I'd love to hear more about how we know where this space station is at any point in its orbit. I mean, what are the tools that you and others are using to keep track of it? and for that matter, to keep track of all of the other thousands upon thousands of objects that are now circling the Earth. We keep track of these things by generally using radar for these kinds of objects. There are radar sites around the world. Various nations have objects, have sites that are watching, basically be gathering data that they can use to predict the orbit as it progresses. So it's radar. Is there anything done with optical telescopes for an object like this that I would think would be big enough that you might be able to track it? Well, one thing that you can do with an object like this, you can certainly see it,

but radar gives you more precise information for these kinds of objects. You can also use optical telescopes to tell you whether or not it's tumbling, what its orientation is, and so forth, and that can be done, and that is useful. Generally, optical telescopes are used for the ones out at geosynchronous orbit to look at those and provide orbit information for those. The radar that you mentioned, is that mostly being operated by the Air Force of the United States and other militaries around the world? I think it's generally recognized that the United States has the most complete catalog, but there are others around that track data as well. And there are commercial companies coming online now that provide data as well. So this is

an area where changes will be happening over the next decades. Bill Ehler of the Aerospace Corporation. He has more to share with us about our crowded skies and space debris. Let's talk more about that and orbital debris in general. One of the very first interviews we did on Planetary Radio about 15 years ago, you came on to talk about the inherent dangers that we face with so much space junk, not just the stuff that makes it back down to Earth, but the danger for other objects in space, including ones that are carrying humans, because we have put so much stuff up there, most of it intentionally, but not all of it. I mean, I think back to that Chinese anti-satellite test, I think, that spread a whole bunch of debris across orbit. What's the current

status? Is this situation as serious as ever? Well, it's getting to be a lot more interesting these days. Back in those days, we were sort of at a, I'll say, kind of a continuum of launching the same kinds of satellites, launch frequencies were fairly constant. But what we're seeing as we look forward now is we're seeing commercial companies and universities and others putting up smaller satellites. Cube sats are coming along or being used. And you see, a matter of fact, we had a satellite launch from India that put up over 100 satellites, whereas in the old days we put up much fewer for the launch. And these CubeSats are things that some high schools are even building these days.

And they can do some amazing things. The technologies are just like they shrunk technologies for a cell phone. The technologies you can use in a satellite are really getting very small and sophisticated. you can use in a satellite are really getting very small and sophisticated. Planetary Society may be a small piece of the problem because, of course, we've got our LightSail CubeSat, LightSail 2, that we're hoping is going to be launched on the Falcon Heavy, next Falcon Heavy launch later this year with a whole bunch of others, these small CubeSats. These CubeSats, depending on how high they go, they can be a long-term problem, and that is an issue. So the CubeSats are being encouraged to come down within, certainly within

25 years, and the sooner the better, I think. So low altitude is not such a bad thing with those. They're difficult to track is part of the problem. A maneuverable satellite would have to get out of the way of one of those things if it sees it coming. You could have quite a smash up. Think of the velocities of these two objects coming at each other in space. I bet a lot of people in the audience for this show have seen pictures of those space shuttle windshields that had pits in them from tiny, almost microscopic strikes of objects in orbit. Yes. In fact, there's one famous picture that you can find online that shows a picture of a little pit in the shuttle windshield that was made by a fleck of white paint. So even these little pieces of material that sort of age off of old spacecraft,

for example, you know, these little bits of material that we put up and then ultimately, for some reason, they get hit by a piece of a micrometeoroid or something and they flake off or just they go through some kind of weathering and they come off as well. Those things, traveling those kinds of speeds can be a problem for a satellite. That's right. Does it complicate the problem further that these objects, these CubeSats, Picosats, Picosats are so much smaller? these CubeSats, PicoSats, PicoSats are so much smaller. I assume they're harder to track with radar than the more traditional satellites that might weigh thousands of kilograms. Yes, these CubeSats are harder to track and they're being encouraged now to put laser reflectors on them or reflectors to make them more trackable so people can see them. CubeSats are only part of the issue. One of the other

things is you're seeing commercial companies now where they're proposing to put thousands of satellites in low Earth orbit, say 4,000, 5,000 satellites per constellation. Just the number of objects and their maintenance activities will certainly increase traffic. Would you expect, therefore, I mean, it seems to be pretty simple math or probability that we probably should expect to see more collisions on orbit, more impacts than we've seen than ever before? Well, I think that's the challenge, is how do we deal with the fact that we're going to have more objects flying around up there, but keep the collision rates down? It's interesting. It's one

thing to have a constellation of 4,000 satellites, but it's also, you have to keep that constellation fed. For example, if a satellite dies, you have to put new ones up. These satellites have lifetimes. So if you're going to replenish constellations, you have to send up new satellites. You have to dispose of the dead ones or dying satellites, or at the end of their life, you want to bring them down. All that can be traffic through these satellites below. So we're going to need really good tracking information on these types of objects so we can prevent collisions with other operating satellites. to manage this, including ways to build in systems or to put systems in space that would de-orbit or bring down old satellites in the controlled way that everybody would want to

see that happen in. Aerospace has looked at that, and we've actually done some, we'll say uncontrolled ways of bringing CubeSats down, and I think others have done this as well. For example, one common approach is to basically have something like a little balloon that would increase the size of the object. It puts out like a sail or something like that that slows down or that makes it so that it sees more drag. That'll bring it in earlier. And as far as bringing down a larger object, I think the industry certainly has ways of doing that. What's happening worldwide? Are space agencies, do they generally recognize this

danger? And do you see collaboration or cooperation to try and make sure that the skies above us don't become just a dangerous junkyard? Oh, yes. I think there are entities that have been in place now since the 90s that can sort of continually look at the space debris issue. And these are international entities where they bring together space agencies worldwide to discuss these particular topics. Something called the Interagency Space Debris Coordinating Committee is probably the most famous. That's IADC. So you can go online and look at that. They put together guidelines for what should be done to minimize the growth of space debris. For example, this idea that you need to reenter your spacecraft within 25 years, or if it's a big spacecraft, to put it in a safe area were suggested as recommendations that are now part of policy and regulations in some countries. Bill, I can't let a conversation with you end without talking about those other objects up there in space, the ones that we didn't put there on purpose. Because of course, you have been a

leader as well in how we study and will hopefully successfully deal with near-Earth objects, and particularly a rock, an asteroid, or a comet that has our name on it. You know, our boss, Bill Nye, likes to, well, he likes to ask, why did the dinosaurs die out? Because they didn't have a space program to find and stop that rock that took them out. What's the current status? Are you seeing progress in that area as well? We are definitely seeing progress. We started these conferences back in 2004. And over that period of time, the topic itself has gained recognition as not really a laughing matter anymore.

Back in 2004, there was a giggle factor associated with working in this business. But that's gone away. And I think nations are really taking this much more seriously. One of the things I particularly like about planetary defense is any solution, any real solution requires planetary effort, not a nation effort. It would require coordination of all the spacefaring countries to be able to put up a really good and effective mitigation technique. So there's a lot going on, a lot of good research is happening, and the conferences really bring a lot of that together. Research is happening and the conferences really bring a lot of that together. One of the other things that I found so fascinating attending the conferences is that the political challenges, the problems that you face between nations may be as serious or as great as the technological challenges of finding and especially deflecting that rock that's headed our way. I mean, have you noticed that as well?

Oh, yes. I think the political aspect of this is a very real part of the problem. In a sense, we have the ability to deflect an object, but the issue is going to be making the decision, a timely decision to actually do that if a threat's detected. And what that means is you have to have the public behind what you're doing. And so we probe that at the conferences. We also look at the political issues that will come up, and there will be quite a few. For example, using a nuclear explosive may be the most effective way for deflecting an object, but it always gets a lot of interest and discussion as to whether or not that's something that humanity really wants to use. What are your feelings about our progress in finding and tracking the objects,

the biggest ones, the ones that are going to be the most important for us to know exactly where they are and where they are and where they're going? Back in the late 90s, the U.S. Congress basically authorized or directed NASA to go forward and try to find all those really big objects that are a threat to our planet, the same anything over a kilometer in size. And we know where over 90% of those are now. So I think there's been a lot of worldwide effort to try to find those. We're finding that the smaller objects down to say 50 meters can destroy a city, or a little bit larger than that can destroy something the size of a county. The idea is it isn't going to take out the planet, but it could take out some, you know, significant infrastructure and cause a lot of trouble on the planet.

So that's something that's where we don't have quite the record of success, although the efforts are increasing and we're discovering more of these things every day. Do you remember offhand how big the estimates are that that object was that exploded over Chelyabinsk a few years ago? Yes, Chelyabinsk was about 17 meters. And there was another object that came down in 1908 called Tunguska, which was about estimated between 40 and 50 meters. That one leveled about 600 square miles of forest. That's a big area.

And it kind of gives you an example that a small object can do a lot of damage. Yeah, and maybe we need, maybe not one that breaks a lot of windows all the time, but maybe one of these objects going off where it can be experienced now and then might provide a little bit of a dramatic reminder of how important this issue is. And that while one that kills a city or a continent may be a very, very rare occurrence, it has happened. We just have to look back to that

example of the dinosaurs some hundreds of millions of years ago. That's right. I think you're absolutely right. And that's one of the challenges with planetary defense is we know the planet's going to be hit by these things, but we don't know when. And humans have this nasty habit of not dealing with something until they've seen a really good example. We hope we have an opportunity to deflect one before that ever happens. Looking forward to the next Planetary Defense Conference? Yes, indeed. It'll be held in the Washington, D.C. area, so it should be a good one. Oh, good. And that will make it easier for me to get to than the last one that you had in Japan, which I know we had a few people there. Our Bruce Betts attended, and we'll be talking to him in

just a few minutes as part of the regular segment he does with me on this show, What's Up? And we love to talk about near-Earth objects, of course. We just talked recently on the program to a couple of our amateur astronomers who received Shoemaker-Neo grants from the Planetary Society. Maybe I'll leave with that. Society. Maybe I'll leave with that. I mean, the contributions that so-called amateur astronomers make to this search for and the tracking of near-Earth objects that we found, is it pretty significant in your view? Well, you know, as we start looking for these smaller objects, it's getting to be more of a challenge for amateurs to play as much of a role as they have. The small ones are hard to see. You need to have fairly sophisticated equipment to do that.

But I do think there's a real role for amateurs to be involved. If an object is detected that's small and coming towards Earth and you need verification, I think the amateurs can certainly help with that. We have some very sophisticated amateurs as well, and various programs have been set up to involve amateurs in these processes. So I think that would be excellent to have them remain involved and to keep looking. So looking across both of these challenges, both the objects we put up there into orbit and the ones that find us that we had nothing to do with putting up there, are you optimistic about the

progress we're making? I definitely am. I think if you look like, say, on the planetary defense side, where we've come since 2004, progress has been remarkable. On the space debris side, I think we've got work to do there because we're going into a new era where we'll be seeing lots of new satellites that are proposed, constellations going up that are going to change the environment in low Earth orbit. So we've got work to do there to get ready for that and to be able to make sure that can be done safely. Bill, you've been at this for 44 years there at the Aerospace Corporation.

Is this something that is going to continue to be a priority for aerospace? Oh, I'm sure it is. You know, aerospace does a lot of work on what's going to potentially be a threat to satellites and humans on the ground. That's why we got into the reentry side. We'll be continuing to do this for a long time. Both of these issues are long-term issues. Bill, there is a great photo of you that we'll put up a link to, and maybe we'll be able to put that photo separately up on the show page for this show that people can find at planetary.org slash radio. And it's you actually looking through a piece of space debris that I have seen

on the aerospace campus in the Los Angeles area. I just want to thank you for spending so many years trying to protect us and objects in space from each other and from disaster. Well, thank you. It's been a lot of fun. I've enjoyed it. You know, it's one thing about the aerospace business. There's always something new and exciting going on. I've been happy to be part of it.

Thanks again, Bill. Bill Ehler, he is an aerospace fellow now at the Aerospace Corporation. One time principal engineer for the Center for Orbital and Reentry Debris Study. The acronym is CORDS. He's done a lot of other great work during his time there. And he is also, as far as I can tell, the primary power behind the biannual Planetary Defense Conference that brings together experts in really every field from across the world

to talk about the danger that our planet faces, that our civilization faces from near-Earth objects. We'll be back in just a moment, as promised, with Bruce Betts for this week's edition of What's Up. Time for What's Up on Planetary Radio for this end of March episode of our program. We have Bruce Betts, the chief scientist of the Planetary Society, on the other end of this line. I wanted to share with you up front. Hello, first of all. Hello.

Stanley Furtig in Brooklyn, Brooklyn, New York. Loved your show on Planet Vax. in Brooklyn, Brooklyn, New York. Loved your show on PlanetVac. He says he was fortunate enough to visit Honeybee Robotics Brooklyn headquarters a couple of years ago. Now he wants to get a PlanetVac to clean up his basement.

Well, we'll work on that. The commercial spinoff. Robots in Brooklyn. I can't do the accent. I'm not even going to try. Just tell us about the night sky. The big groovy cool thing happening is that Mars and Saturn I can't do the accent. I'm not even going to try. Just tell us about the night sky. The big groovy cool thing happening is that Mars and Saturn are getting really snugly and close in the night sky.

They're actually coming up at 2 in the morning or so. But if you go on the pre-dawn, you can look in the east, southeast. Two objects, both bright, similar brightness. Mars is the reddish one. Saturn's the yellowish one. They will be particularly close on April 2nd, then grow apart again. So you can watch them come together and then separate. It's very exciting, Matt.

Very exciting. Evening sky, we've got Venus looking super bright low in the west shortly after sunset. And Jupiter hanging out coming up around 10, 11 p.m. in the east, looking super bright. We move on to this week in space history. It was 1974. We had the first ever spacecraft flyby of Mercury with Mariner 10. Gave us our first close-up looks at the inner planet. And not repeated for so many years. How much of it did we still need to see? About half. Mariner 10 did three flybys, but the way the orbit,

orbital dynamics worked, it basically saw the same side every time. So we had to wait for messenger to go by in 2008 and then orbit in 2011. And then we got the whole planet. Yeah. And until then, who knows what we would have, were to find on the other half of that planet.

Could have been giant billboards or flying saucers or anything unlikely. Well, yeah. But fortunately, they were all moved before 2008. They saw us coming. Exactly. Clever, clever alien creature, Mercurians. We move on. But seriously, folks, we move

on to a random space fact. Well played. You've been talking this show about Tiangang-1 seems rather big when it's going to re-enter the Earth's atmosphere but really was a very small space station. For reference, NASA's

Orion capsule that's currently under development has a larger pressurized volume than Tiangong-1 does. Almost 20 cubic meters compared to 15, though only about half of Orion's pressurized volume is said by NASA to be habitable. By which I assume they mean where humans can hang out, but maybe there are flesh-eating aliens in the other half. I don't know. From Mercury, no doubt. They had to go somewhere. Boy, I'm sorry for the guys who had to live there.

Guys and girls who had to live there for a while. All right, we move on to the trivia contest. I asked you, of the 88 modern constellations, which is the smallest in area? So solid angles subtended, to say it more formally. How'd we do, Matt? We got a really nice response for this with our standard prize package, and it was a brand new listener, someone who just wrote to me a couple of weeks ago to say he's so glad that he has found the show. He's loving it. He regrets it took him this long to discover it.

It also delayed his opportunity to win. That's Jeremy Zuccarello in State College, Pennsylvania. He says that that smallest of the 88 constellations, recognized constellations, is the crux. Or as so many people pointed out to us, fans of Crosby, Stills, and Nash, the Southern Cross, correct? Yes, although you don't have to be a fan of Crosby, Stills, and Nash to still appreciate Southern Cross. Doesn't hurt. He said area of roughly 68 and a half square degrees, or about 5% of the biggest of those 88, hydra. So it is little and it's really

cute and it's hard to miss too, since I've actually been down there in the Southern Hemisphere exactly once and it's pretty pretty up in the sky. Pretty pretty. You want to hear about some other people? Oh, I do. Of course. A whole bunch of people pointed out, while the Southern Cross is, duh, southern, if you go back to the fourth millennium BC, Crux or the Southern Cross was visible as far north as Great Britain, thanks to procession, which is also hidden from us once again. Huh. I'll try that. Do you want to give us, what's a one-sentence explanation of procession?

It's like when a top is spinning and slowing down and the top of the top points different directions. That's kind of like procession. Okay. Martin Hujovsky, who can often be counted on to contribute good stuff in Houston, Texas, or from Houston, Texas, the flags of no fewer than five countries feature crux.

Australia, Brazil, Papua New Guinea, and Samoa, or Samoa, as my Samoan friend says. That's about 245 million people. So it carries with it a lot of pop-ulation, he says. That would have been a great random space fact. Oh, it is. Good job. Yeah. Dave Fairchild, our poet laureate. Though some may say the Southern Cross, like Crosby, Stills, and Nash, an asterism doesn't count. It's simply balderdash.

Instead, I'll put my vote on Crux, the smallest to our eyes, and track its coal-sack nebula across the austral skies. We're ready to move on. So back to Tiangong-1. What missions visited the Tiangong-1 space station? Name all the missions that visited it. Go to planetary.org slash radio contest. And no, we did not mention that, or at least Bill Ehler didn't mention that. So good on you. That's a great follow up to the contest. And you have this time until Wednesday, April 4th at 8 a.m. Pacific time to get us your answer.

And if you are chosen by random.org and have got the right answer, you might just win yourself something very special. We got a note from Perry Metzger in New York, New York. He says, did you know that rubber asteroids aren't even available for purchase online? Even Alibaba, China's largest source of random products for sale, doesn't list any. Well, that's because we took rubber rocks and relabeled them rubber asteroids. But if you get them back in stock, he says, planetary society would dominate the market. It's a huge market for rubber asteroids.

I decided, based on Perry's note, to go into my secret and very small stash of remaining rubber asteroids. I knew it. I knew you had a secret stash. Stay out of my desk. We will award the winner this time a Planetary Society rubber asteroid, the rarest asteroid type in the world,

in the universe, and... Is that an R-type asteroid? Yeah, it's either that or B for bounce. It's that and an itelescope.net account, a 200-point account on that nonprofit network, a worldwide network of telescopes you can use to look all over that same universe.

Maybe you'll find a rubber asteroid out there somewhere. All right, everybody, go out there, look up the night sky, and think about, in general, what is the crux of the matter? Thank you, and good night. I think you have hit upon it. He's Bruce Betts, the chief scientist, the crux of all science at the Planetary Society, who joins us every week for What's Up. Hey, let us know if a piece of Tiangong-1 lands in your backyard.

Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its watchful members. Mary-Louise Bender is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan, Ad Astra.