Planetary Radio: Space Exploration, Astronomy and Science - 7 More Minutes of Terror: Perseverance Arrives at Mars

Episode Date: January 20, 2021

The 2020 Mars Rover will reach the Red Planet on February 18th after many months in the relative quiet of space. It will then undergo a true trial by fire as it descends to the surface. Jet Propulsion Lab systems engineer and his colleagues hope it will arrive as successfully as its sister Curiosity did in 2012. He tells host Mat Kaplan what to expect. Planetary Radio listeners prove once again that they are awesome as they go to amazing and unnecessary lengths (oops!) to answer the space trivia quiz. There’s more to discover at https://www.planetary.org/planetary-radio/0120-2021-gregory-villar-perseverance-edlSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Looking forward to seven more minutes of terror as Perseverance reaches Mars, 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. Gregory Villar is a young engineer who will join his JPL colleagues and the rest of the world as Perseverance, the Mars 2020 rover, plunges toward the red planet's surface on February 18th. He'll help us understand that harrowing event on today's show. By the way, you'll be able to join the Planetary Society's celebration of Mars when we go online for PlanetFest21 beginning February 13th. Details are at planetary.org slash planetfest21. The time has come, the pod host said, to talk of

many things of solar sails and Kapton film, of misstatements and wings, which is my way of teasing this week's What's Up visit with Chief Scientist Bruce Betts. But before we get to any of this, let's visit the weekly newsletter from the Planetary Society. Headlines from the January 15 edition of the Downlink are led by something you heard Andrew Jones mention here a few weeks ago. China may send a lander to Jupiter's moon Callisto, arriving there in 2035. It's one of two proposed missions by China to our solar system's giant world. We're also happy to report the Jupiter orbiter, Juno, and the inside lander on Mars have been granted mission extensions by NASA.

Juno will examine the other Galilean moons. And NASA finally held that static test of the Space Launch System's core stage. It looked great for about a minute before shutting down well short of the planned eight minutes. We've just learned that computers ended the test when a, quote, intentionally conservative, unquote, pressure limit was reached in a hydraulic system. There was at least one other unexpected minor anomaly. Lastly, kudos to Virgin Galactic's sister company, Virgin Orbit. It put 10 CubeSats up there with the first successful air launch by its Launcher 1 system.

Gregory Villar is an entry, descent, and landing system engineer on the Mars 2020 rover mission. He has spent nearly eight years working toward what is about to happen on Mars. As you're about to hear, he got his start at the Jet Propulsion Lab several years earlier while he was just a college sophomore. Now he's a major contributor to what we hope will be another successful arrival at the red planet. Gregory, thanks so much for joining us on Planetary Radio. Matt, thanks for having me. I'm so excited to be here today. I was thrilled that you were recommended as somebody to talk to because your expertise is in exactly the area that we had in mind. But you also have an interesting

history there at JPL that has led you to this moment. I mean, as people hear this, about one month out from what we're calling seven more minutes of terror, as perseverance this time descends to the Martian surface. First of all, do I have that right? How much is this going to be like what we all experienced with such thrill when Curiosity made it down to the surface several years ago? You know, Matt, it's probably even more exciting in some way. This is basically the beginning of what we are calling the Mars sample return campaign.

With any Mars landing, it's very challenging. Although we always see the successful landing on Mars, everything is still very challenging about it. In that regard, it will be very exciting. It will still be very nail-biting. So let's all hope for the best here. Most of us who listen to this show anyway, and certainly I, remember those thrilling moments, bone-chilling moments as curiosity made its way down. We have seen the so-called landing ellipse, the area in which you expect the spacecraft to land, has been shrinking ever since we got into this game with Viking all those years ago. This is another leap in that direction, isn't it? I mean, you really are looking to make a pretty precise landing. Yeah, that's very true, Matt.

I'm glad you've done your homework here. But basically, between Curiosity and Perseverance, the landing architecture is mostly the same, with some improvements here. And some of these improvements have been able to get us to reduce the size of our ellipse, one of which is this technology called Range Trigger. So basically, we are deploying our parachute based on our range to target, which helps us kind of shrink in that ellipse. And also the more popular thing, as you probably people have heard about, is terrain relative navigation, which is a really cool new technology we have on Perseverance Landing. Basically, the way that works is, you know, when we release our heat shield, we have visibility to

the ground with a camera. As we're on our parachute, we'll be taking images with this camera and correlating that with an onboard map we have. We will be able to better understand where we are at that point in time. And then with predetermined safe spots on the map we have on board, we will be able to be able to say, look, this is where we currently are. And here are all the safe places we can go to. So therefore, let's go to one of those dedicated safe spots. Those are two of the new things on the entry, descent, and landing system that enables us to have a much smaller ellipse. I'm going to put up a link on this week's show page at planetary.org slash radio to

a show that we did months and months ago where I went to JPL, back when we could actually do that kind of thing, pre-pandemic, and was in one of the labs there looking at some hardware, four tiny little radar dishes, only a few centimeters or inches across, which are going to be doing some of this work that you're talking about. I got to tell you, it was thrilling to be standing there looking at this hardware in front of me on a workbench. Right. I mean, that's, it was thrilling to be standing there looking at this hardware in front of me on a workbench. Right. I mean, that's one of the kind of benefits of us being local to Pasadena, right? It's just being able to visit places like JPL before, of course, the pandemic

and being able to see all of this really firsthand technology that is going to be at Mars at some point in the future. And I think that's a very fortunate thing we have for us. at some point in the future. And I think that's a very fortunate thing we have for us. You very kindly gave me a link to a page on the Perseverance site, and we will link to this page as well, of course, from the show site, the episode page. It is a diagram showing the descent of Perseverance, all the different steps. Why don't you take us through this? I mean, first of all, it does look remarkably like what Curiosity did. Oh, absolutely. Just as scary, but just as exciting as Curiosity. So basically, this is what we call the entry, descent, and landing phase of our mission.

For short, we call it EDL, or as popularized back in Curiosity, the seven minutes of terror. You know, when we launched from Florida, this spacecraft has basically traveled over 300 million miles. And by the time it reaches Mars, it's going to be traveling really, really fast, on the order of like 12,000 miles per hour. Before we get to the atmosphere, we're actually attached to this thing called the cruise stage.

You can think of the cruise stage as like our Uber driver, right? The rover is in the aeroshell capsule, and this capsule is attached to the crew stage, which is kind of taking us to Mars through space. So about 10 minutes before we get into the Martian atmosphere, we separate from our driver, this crew stage, and this aeroshell that we're in, it kind of maneuvers towards the right orientation that it's going to use to go through an EDL. And so the first thing that happens is we use our aeroshell and we kind of break through the atmosphere. The analogy I like to use is imagine you're driving in a car and you're going really, really fast on the highway and you just let go of the gas, right? You don't even push the brake.

You're kind of slowing down because of air resistance, right? And that's basically kind of the first part of EDL where we use the Martian atmosphere to slow down. As we're slowing down, we're generating a lot of heat from the friction of going through the atmosphere. And that's why we have this heat shield protecting us and protecting the rover and everything else from burning up. And we're going through this atmosphere at close to 12 Gs. And then we enter a portion called entry guidance. This is the maneuver that kind of the Apollo capsules use as they re-enter dirt. But what happens here is we kind of have an ideal of where we want to go, our target. So we have these little thrusters on the capsule that helps us maneuver through

the atmosphere to get us to that point in time and space. When we reach supersonic speeds, we deploy what's called a supersonic parachute. That gets us down to about 900 miles per hour. But 900 miles an hour is still super fast, right? You wouldn't want to touch the surface of Mars at 900 miles an hour. So the next thing we do is we release our heat shield. So when we release our heat shield, we now have visibility to the ground. So now there are two things we can do here, terrain relative navigation, which I mentioned earlier, but also we are now able to use our landing radar, which we also had on Curiosity. And this landing radar helps us understand our velocity and our altitude.

When we're at a right velocity altitude pair, that is our signal for us to separate from our backshell parachute configuration and come down on these thrusters. So at this point, we have our rover on what's called the descent stage, or as I like to refer it as its own jetpack. And it's coming down on these thrusters, right? When it's about 60, 70 feet from the ground,

the jetpack lowers the rover on these cables slowly. As it's coming down, the rover releases its wheels like a landing gear for an airplane. On the order of, you know, a little less than a mile per hour, we hopefully softly touch down on the ground. When that jetpack senses that the rover has softly touched the ground, we cut those cables and the jetpack or the descent stage flies away from the rover, further away from where the rover is supposed to drive because we wouldn't want this jetpack

to contaminate that site. And then we're on the surface of Mars. Makes it almost sound easy. You didn't use the term that so many of us came to know during that harrowing landing of Curiosity, the sky crane, which is that rocket platform, that jet pack that actually winches the rover down to the surface. That was the thing I think that made so many of us lay people think, oh my God, is this nuts? Or is JPL as good as they usually are? That's funny you mentioned that because early in the history of Curiosity, people were very pessimistic about Skycrane, right? There was years of design and proving it to an external review board and to NASA headquarters. It's like, come on, is this actually going to work?

So it took a lot of convincing to headquarters and our external review board that this would actually work. It was just such an elegant solution for such a different problem compared to previous rovers like Spirit and Opportunity and Pathfinder. It has to be something of a relief to know that this worked once before. And I assume you got lots of good data from that entry to Stanton Landing. I would say yes and no. At the time, I believe I was, let's see, 2012. I was about two or three years into my JPL career and only one year of experience on the EDL team at the time. I just kind of on the surface knew that it was complicated. And so when we landed, I was like, oh, sweet. Like that was really awesome. But I've been working on this landing system now on Perseverance for the past seven and a half

years. And I look back and think, wow, I did not know how complicated this actually was and how frightening this was. But I know that I'm confident in kind of all the people that I've worked on this project with. And everyone's so very smart, so very diligent. And we do our due diligence, right? Whether it's like all the testing or analysis, we're going to do everything we can up to the point where we can't do anything. So that whatever happens on landing day, we will hopefully be sure that we did what we can do. Still very, very nerve-wracking, but I'm also very excited. Let me bring up another element that you mentioned, that parachute, that supersonic parachute.

No small achievement in itself. I mean, your colleague, he's now JPL's chief engineer, Rob Manning, has talked with us on this show several times. He is such fun to talk to about this because he seems to have been almost as entertained by the failures as the parachute was developed as by its success. This is no small feat. No, absolutely not. In fact, there were several. I think it was a very hot topic at the beginning of the Mars 2020 project. Between Curiosity and Perseverance, there was this other project called LDSD, the Low Density Supersonic Decelerator Campaign.

And basically, on one of their tests, one of their parachutes failed. And that really brought into question kind of our understanding of parachutes, right? Like, did we just get lucky on Curiosity? So that spun up years of just kind of debates and testing, building a new parachute. I was actually fortunate enough that part of my experience on Perseverance was to lead the parachute test campaign in the world's largest wind tunnel,

at the wind tunnel at NASA Ames. So that was really cool. We got to test some parachutes in there and ultimately bringing that to our sounding rocket program called the SPIRE. It's another acronym. I could probably send you what that means. But basically, we put our parachutes on these sounding rockets to test them at supersonic conditions as well. It was something that really put us into question and be like, we need to open that book back up because parachutes

are not an exact science here. So we have to do as best as we can in terms of analyzing and testing them. But, you know, it's also really, really cool. With anything that's as interesting as that, people tend to like really keep their focus and make sure that they're doing their due diligence. Not only did you have to get this parachute up to a really high rate of speed using the sounding rocket,

wasn't part of this also, or I hope I have this right, obviously if you're going to test a parachute and try to simulate the Martian atmosphere, there's a heck of a lot less of it than you're going to find at the surface of Earth. Was this also to get you up high in Earth's atmosphere where it was somewhat similar to Mars? Very good, yes. I love how educated you are.

And that's exactly right, right? We're big fans. You've got to know that, right? I do. I do. I mean, I would have been a big fan as well, right? And that's why I get to do what I do today. But you're right. There are a lot of things on the EDL system that basically cannot be tested end to end because Earth is not Mars, right? So we basically have to do these testing in pieces. And a piece of this is parachute testing. And you're correct. The deployment altitude that we chose for the sounding rockets was to somewhat mimic the atmosphere conditions on Mars as much as possible, right? Of course, it's not going to be exactly the same on Mars. But because the atmosphere on Mars is less than Earth, we have to go higher up into Earth's atmosphere to get somewhat comparable environments. More of my conversation

with Perseverance rover engineer Gregory Villar is coming up after this break. I'm a big believer in the benefits of counseling. Lord knows I'd have benefited from it during a couple of long ago periods in my life when I suffered from depression. Is there something getting in the way of your happiness? BetterHelp is not a crisis line, and it's not self-help. It is professional counseling provided securely, online and worldwide. You can find a great, caring counselor in less than 48 hours and join the over 1 million people who have taken charge of their

mental health through BetterHelp. You'll schedule your weekly video or phone sessions, and you can log in anytime to message your counselor. It's also more affordable than traditional counseling. Get started by visiting BetterHelp.com slash planet. That's BetterHelp.com slash planet. That's better H E L P.com slash planet. I hope you'll find the joy we all crave. This podcast is sponsored by better help and planetary radio listeners will get 10% off their first month by visiting better H E L P.com slash planet. You have this complicated sequence, and I really do hope that people will go and take a look at this diagram that traces this seven minutes of terror. Remind us, how much control will you folks at JPL have over this process as perseverance descends? That's a very good question. And actually a very interesting

question for those who don't know. So in the diagram that you see, basically from this point on, there is zero human control. We do a lot of preparation before this diagram that you see even hours or days before. But all of this that you see on the diagram is completely automated. So we're just going to be hoping that all of our testing that we've done on the spacecraft will be able to come to fruition. And it's up to the spacecraft and its sensors and its algorithms and everything to kind of land safely on its own. And, you know, again, it has to be somewhat reassuring, right? That Curiosity managed to do this just right, as did, in slightly different fashion, Spirit, Opportunity, and earlier spacecraft. But still, the fact that you basically are, during this time,

just spectators, like the rest of us, has to add to that atmosphere of nail-biting. Oh, absolutely. I need to share a story that we had on Curiosity. I think most people who probably watched the Curiosity landing remember kind of someone, his name is Al Chen. He's basically our lead EDL person right now on Perseverance. But he was a person kind of narrating Curiosity landing. And kind of the notable moment was when Al said, touchdown confirmed, and then everyone starts celebrating, right? What most people don't know, actually, is there's a backstory here, which I like to share in my talks. There are actually three indicators that we have internally that we're kind of, you can actually hear it on the net, but people really didn't know what we were saying.

We don't want to just say touchdown confirmed without really being sure that that's the case, right? And we'll do something similar for Perseverance. But basically, those call signs were one, Tango Delta Nominal, which basically means we received signal from the rover that it sensed that it touched the ground, right? The next one, you could probably hear it said Rimu Stable. That meant basically we have an IMU, an inertial measurement unit, which kind of measures if something is moving. You can imagine the rover touching down, but maybe it's sliding or maybe it's rolling, right? If it's sliding or rolling, we're like, well, that was not a safe landing. So when we say rim-use stable, we're basically saying the rover is just steady, like it's not moving. And then the third indication was calm was still good or something like that. The reason we had that was because you can imagine

that a rover touches down, it's stable, but this jetpack or the sky crane kind of smashes on the rover, right? It just doesn't communicate anymore. So we want to wait a certain period of time to confirm like, yes, the send stage kind of flew away and we're still getting signals from the rover. And so in Curiosity, the EDL team,

we knew these three indicators coming along, but they told us do not react, right? Like do not react until you hear Al Chen say touchdown confirmed. It's funny when you hear some of us, when you see some of us in the video, when we hear some of these indicators, we're basically holding back our excitement as much as we can, because to us, we're ready to, you know, just jump up with joy. It was kind of boiling up by the time Al said touchdown confirmed, and it really amplified kind of the celebration at that point. That is absolutely fascinating. And I probably should have been aware of these extras. But yeah, of course. I mean, my God, if you God forbid, you should land on the side of a cliff. You know, the one, and I hesitate to bring it up,

but maybe bringing it up will help make sure it doesn't happen. The one that scared me so badly about Curiosity was not getting down to the surface, but I had this morbid paranoid fear that one of the pyros would not fire. It would separate the cables from Perseverance and let the sky crane fly off to the side and crash, as it did. Pyros are pretty well-proven technology, right?

Yes, they are. You know, that's also a fair concern for a lot of us. I mean, there are 70-plus pyros through this whole EVL sequence. We don't just use the pyros to cut the cables, right? All the way from the beginning of separating from the crew stage, there are pyros there. There are pyros involved with deploying the parachute. There are pyros involved with separating the heat shield. There are pyros involved for separating the tent stage from the back shell. There are pyros everywhere, right? Although the pyros are very reliable technology,

another way we kind of mitigate that is by we fire two signals for every set of pyros, right? So as long as one of these signals gets to those pyros, hopefully that will ignite and that will be enough to kind of ignite it and fulfill its function for that purpose of the sequence. All right, Gregory, thanks a lot. Now I have to try not to be 70 times as worried. That's all right.

I'm sure it's all in hand. We're down on the surface. What happens? I mean, obviously the celebration takes place and I will be part of that. You can count on that. What happens in those first few minutes after Perseverance is safely on the surface? We touch down safely, hopefully softly. That's the plan. Whenever you're new to an environment, whether it's getting off a plane in a different country or maybe imagine yourself being on the moon one day, you kind of have to orient yourself, right? Like things doesn't just happen right away. So in the first few seconds or minutes, basically one of the first things we do is we take some

pictures with what are called hazcams or hazard cameras. Those also get sent to Earth so that we can, another means of confirming that we touched down safely. And then we'll continue to get information from the rover and do things like activate our antennas for communication and just give time for the rover to kind of assess itself and produce all the data it needs or data that it needs to send to us so we can assess it on the coming communication passes we get from the orbiters around Mars. Also, not just in the next few seconds or minutes, but in the

first few days, we're doing a bunch of things like getting this data from the rover and just assessing the health, power systems, the thermal systems, all those things to make sure that we have a healthy rover. We're not going to rush through it. We're also not, we'll be very efficient about just understanding kind of how that rover is doing on Mars before doing any major activities. I would say kind of the first major activity is what's called a software transition from launch to the journey to Mars through entry, descent, and landing. There's kind of one major software suite that's on the rover. And, you know, that really fulfilled its purpose for that journey.

But once we get to the surface of Mars, that's a completely different set of expertise that's needed. So we have to kind of switch out our operating system. And that activity takes place, a little over a week after we land on Mars. That's another big moment, I'm sure. Almost like not a new operating system, but all new apps. I mean, is that a fair analogy? I like the way that, yeah, that's a great analogy, actually. I mean, not just an operating system, but also apps, right? For example, like one app is driving, right? The rover doesn't really need to drive while it's in its spaceship in space. So like we'll have to do that and things for most of the instruments. You could say there were a toned down version of these instrument apps during

the cruise phase of the mission, but now we need to use their full capabilities. That's great. I'm going to start using that. New operating system and new apps. So when does the mass get raised? And we get those beautiful Mastcam-Z images will start to come back to Earth. Depending how things go, I'm not quite sure when the mask gets raised, but I would imagine it's in the first week or so, if all goes well. I believe the drive, again, if all things go well, is planned within the first two weeks. So hopefully by that point, we will need the mast, obviously, to the drives as well. So I would say around two to three weeks just to be conservative here.

Through all of this, it has been up to you and your fellow engineers, the other men and women who designed, built and got Perseverance to Mars. But through all of this, you've had that other key group involved with this mission, the scientists, who have been egging you on and waiting for you to finish your work so that they can start to learn about this exciting portion of Mars that we've never been to before, Jezero Crater. Do you have much interaction with the science team? We do for specific things. Two things that come to mind, maybe more relevant for the general audience. There's this whole process called the landing site selection. Over the course of the project, we've had landing site workshops. And part of these workshops is to assess kind of

where to go. Ultimately, we obviously decided on going to Jezero Crater, but that required a balance of engineering assessments and scientific interest. So part of the EDL team's job is to say, hey, are these landing sites safe to go to, or are we capable of going to these landing sites? So in that regard, yes, we do interact with the scientists, but more so feeding into that process, I run this group called the Council of Atmospheres, which sounds pretty fun, like the Council of Elrond, I guess. But basically, this group are a group of atmospheric scientists and a group of EDL engineers, whose job it is to characterize the Martian environment during the timeframe of EDL,

because understanding the environment feeds into our physical simulations of EDL. And so we need to feed that into those and to understand what the challenges we will have, if any, with a Martian environment. So yes and no, I mean, we do have to interact with scientists for specific things for entry, descent, and landing. But I would say the bulk of the science interaction is with the surface team, right? The surface engineers. I know this from my experience on Curiosity, where I was able to work for, I believe, the first 200 sols, which was also a completely different and amazing experience working on Mars time. I won't ask you which group, the engineers or the scientists or the elves or the hobbits, but that's fascinating.

And I'd forgotten, of course, that engineers were a key part of that decision about where to go, which of these landing sites. Are you satisfied from the engineering standpoint that Jezero is not just very scientifically promising, but a safe place for Perseverance to explore? Right. Absolutely. You know, the way this landing systems progress through history is in the beginning, it was really just the engineering that drove the selection of the landing site, right? It's just like, well, let's just go to somewhere safe, somewhere flat, like a landing strip. And so like, there's no hazards or anything. Part of this kind of makes me nerd out a little bit because compared to past landing sites,

Jezero is a little more challenging in terms of hazards and terrain and all that. But we have that technology now, right? That's the cool thing about innovation and technology development is we're now able to utilize these things that we've developed on Earth to be able to go to more exciting places on Mars. So I am happy because it's a cool thing to be able to say, look, we're using this technology to be able to go to these cooler places on Mars. And that's something that wasn't possible before. What wonderful progress. I wonder if you think of yourself now, now that you've been there for over 12 years as sort of an old timer at JPL, in spite of the fact that, I mean, when you got your start, you were still an undergrad at Cal

Poly Pomona, part of the California State University system. That's right. Yeah. I mean, when you got your start, you were still an undergrad at Cal Poly Pomona, part of the California State University system. That's right. Yeah. I mean, I was very, very fortunate. It's kind of an interesting path I took here. But basically, when I was an undergrad at Cal Poly, I was majoring in physics and I was a sophomore. I was a sophomore in physics and my advisor approached me and a classmate saying, hey, one of my old students is now doing a postdoc at JPL. Do you guys want to help him? And I didn't really know what I was getting into. But fortunately, it was looking for brown dwarfs using the Palomar Observatory. I was like, sure, this sounds like good experience. JPL, what's JPL? Whatever, I don't know what that is, but sure. And it all started with me going to Palomar Observatory.

I still remember driving up at night and it was just, the sky was so clear. The moon was a little bit bright, but when we got into the dome of the Palomar Observatory, I remember being inside the dome, pitch black, and just kind of like, where am I? All of a sudden, I hear this humming sound, which were the motors to open up the dome. Slowly, this humming sound keeps going, and I see the slit of the domes kind of slightly open up. And seconds later, the moonlight just

illuminates the entire dome, and I see this huge 200-inch telescope. I'm hooked. That was a really quite fortunate experience where basically I was able to kind of attach my name to a paper and apply to a NASA scholarship. And that NASA scholarship came with an internship at a NASA center of my choice. It was really cool because I was kind of a baby at the time and I didn't want to leave LA. So I just chose JPL because it was in LA. But I ended up loving it, right? So I interned there for two years, and I eventually turned that internship into a job. And one of my first jobs was fortunately being able to work on Curiosity. And you spent some time on Cassini as well, right? Not too long, but got a little exposure

to that mission. Yeah, that's also a super cool mission. I mean, people kind of talk a lot about Mars, but Cassini was such an amazing feat. Hopefully most people saw the culmination a few years ago. But the way that worked was between Curiosity and Perseverance, I had a little downtime. And so I was kind of looking around JPL to see what else people needed help with. And there was a group, they were the radio science operation group. So I believe I spent about a year, a year or so helping the radio science group kind of do their observations with the Cassini spacecraft. So we would look at observations from the radio instruments and how they're interacting with Saturn's atmosphere. And so that was a really cool experience as well, because it's a different mission aside from something on Mars. was a really cool experience as well, because it's a different mission aside from something on Mars. You have picked up quite a spectrum of experience across your time. Well, beginning, I suppose, at Palomar, but extending right through today. I feel very fortunate. I think it was the ideal of just taking initiative and really realizing that there's so much that GPL has to offer. To be honest, when I was an intern for

two years, I basically was only interacting with my mentor and the students who are also assigned to my mentor. And embarrassingly, when I started in 2008, I didn't really know about Mars missions. I know Phoenix was landing at the time, but I was like, what is this Phoenix thing? Okay, whatever. And it wasn't until I was actually employed in 2010 where I'm like, wow, there are like flight projects at JPL. One of the cool things about working there is just like the diversity of experiences you can get there. What do you say to, because I know you do this, you do some outreach work. What do you say to undergraduates who maybe are intrigued, inspired by your career and others and would like to follow in your footsteps? That's a very common question that I get. And I guess there are a lot of pieces

of advice that I give. I think in the context of interns, I believe kind of the best advice is finding something that you like and networking appropriately. People tend to kind of chase a certain goal or ambition. But I think if you just find something that you actually love doing, that is a much better way to go. Because I say this, but over the past 12 years, I go to work. But for the most part, it really doesn't feel like I'm going to work, if you know what I mean. And another big thing is, as I mentioned, my first two years at JPL was in a little cubicle, basically, and not interacting with the rest of JPL. And so another piece of advice I give is just kind of get out there, right?

Like once you're in a system, in this case, JPL, kind of explore your surroundings, right? Talk to other people, like use the resources that you have where you are now. So at JPL, you know, I did on my breaks, I'd be if I was interested in, for example, black holes, I would find a black hole expert at JPL and ask that person if they would want to grab coffee. Or if I heard about Mars landings, I would try to find someone who's willing to talk to me over lunch about Mars flight projects. So things like that, you know, just really focus on your goal, but also don't

forget to kind of explore your surroundings as well. Excellent advice. And who would have thought, not you, I bet, from the sound of it, that you would start out helping to learn about brown dwarf stars and end up helping us get back to Mars. If you asked me at the time when I was studying brown dwarfs, if I would be involved in what I am today, I would definitely have not seen that coming. I have a recommendation for you as somebody who worked in that field. A book called Cosmic Odyssey. It's about the work that has taken place at Palomar for decades by Linda Schweitzer, an astronomer. We're going to have her on the show before too long. It is a wonderful, wonderful book

about all of the knowledge of our solar system and the universe that we have gained from the Palomar Observatory, which is a very special place to me as well, really kind of a shrine of science. I love going there, and I can understand how it got you started with the romance of all this. It covers the work that you were doing

on Brown Dwarfs as well. Oh, awesome. That's a chapter in the book. So a little preview for the rest of you out there. Gregory, I'll leave you with this. Where will you be on February 18th during those seven minutes of terror? I will be with the rest of my colleagues, specifically at JPL in what's called the EDL War Room. It'll be a bittersweet considering that we're in the kind of COVID era here, but we've been working on this. I've been working on this for the past seven and a half years, and I don't think there's any other place I'd want to be than with the people who've also done just as much work or more than I have. So that's where I'll be on landing day.

Gregory, I wish you and the entire team and all of us the greatest of success with this next arrival on Mars, the Perseverance rover coming down in Jezero crater on, as we said, February 18th. Best of luck. Matt, thank you so much for having me. I really enjoyed this interview. Me too. JPL Entry, Descent, and Landing Systems Engineer Gregory Villar. Bruce Betts joins us next. Time for What's Up on Planetary Radio. We are joined by the Chief Scientist of the Planetary Society. Bruce Betts is here to tell us about the night sky and resolve some confusion that I caused with the quiz question that you put out there two weeks ago. We'll get to that.

Welcome. Thank you. Looking forward to it. Yeah. Well, distract me. What's up? What's up? Well, I've also gotten rid of several planets in the last week or two.

Oh, good. It was clogging up the system. It really was. So you won't be able to see Saturn. You probably can't see Jupiter or Venus. They're respectively in the sun setting and sun rising glare. You can, however, see Mars. And I've brought in an extra planet just to help out. So Mars in the evening sky, high in the south, looking reddish, pretty bright. And near Mars for the next little bit, Uranus. Uranus, which is from most sites, not visible with just your eyes, unless you have really good eyes and really dark sight. But with binoculars, you can see it as a blue dot. With a telescope, you may even be able to resolve it as a little

bit of a disk. Well, Mars is clipping through the sky. So what you're going to want to do for Uranus is dig out a finder chart from the internet. It's tricky to find because, you know, it's Uranus, but it's near Mars. So it gives you a nice spot in the sky to look for it in the evening sky. That's very cool. I always like it when Uranus comes back into view and you tell us that, you know, if you've got great eyesight and really dark skies, you might not need any assistance to pick it out. That's something for a bucket list, I guess. Great eyesight. Yeah, right. Great hearing would be even better for me. We'll put that on the bucket list. Okay. All right,

we move on to this week in space history. In 1986, Voyager 2 flew past Uranus. Speaking of which, got a much better view than you will in the night sky, but only a brief view, whereas you get to see it frequently if you look for it. 2004, Opportunity landed successfully on the red planet and did some Mars roving for many, many years. Going on 17 years ago. Just amazing. I mean, it is 17 years ago. That makes me feel elderly.

The older we get, the more I think we should use Mars years, possibly even Jupiter years. Maybe Saturn. I'm not quite to Saturn years yet, you know, like 30 Earth years. We need an app for that. I'm sure there probably is one. Let us move on to... You know, you don't have to random space fact. You know, you don't have to fake the echo. I add it for you. Oh, well, then random space fact.

The surface area of Ganymede, Jupiter's moon, which you may recall is the solar system's largest moon, its surface area is bigger than the combined surface areas of Asia, Europe, and Africa. It's a lot of surface area. You're talking about combined, right? Those three continents combined. Those three continents combined, still not quite as large as what we have to explore, that is the surface area of Ganymede. Remember, Titan's not that much smaller. So you can think of Titans about those three continents worth as well.

Lots more to see out there. We move on to the trivia contest. Oh, the trivia contest. I asked you, what is the approximate mass of NEA Scout, Near Earth Asteroid Scout? Matt, what did you ask those people who weren't listening carefully to the radio show, but going to our website, which are not the people, ironically, who are listening to our radio show right now? Nea culpa, that you heard Bruce's emphasis on the first person singular there. That's because he got it right. I added extra words when I put it on the web page. I asked, what is the approximate mass of the NEA Scout

solar sail? And a whole bunch of you resourceful geeks out there decided that what we probably wanted was the mass of just the sail, which was not the case. But my gosh, did a bunch of you do a great job. We can't go through all of these, but we got answers from everybody who calculated because nobody found it online anywhere. They ranged from an estimate of 22.9 grams up to about a kilogram. They centered, though, around the low 300s, the low 300 grams. the low 300 grams, like Hudson Ansley in New Jersey, he said like 325 grams, assuming the density of the film was about one and a half grams per cubic centimeter. Ed Lupin in California went a little bit further.

He said, I calculated the mass from the manufacturer's data sheet. Nice. And so he took the, you know, the area of the sail, two and a half microns by 1.54 grams per centimeter equals 331 grams plus. Anyway, it goes on from there. And then he figured in the aluminum coating as well. Well, yeah. This is great that people did this.

I'm so sorry. I hope you found it an edifying experience. And we will accept either in terms of what random.org chooses Kumeysha also came up with about 300 grams. But he added, if the sail were made of graphene and one atom thick, the sail would weigh about a quarter of a kilogram less. In other words, the sail would only be about 50 grams. A little harder to get a hold of one atom thick graphene so far. But we look forward to the future. Yeah. Won't that be great? Enough fooling around. The winner, and he's a first time winner, is Brett Kruger in Kansas with 14 kilograms or about 31 pounds if you want those imperial

units. First time entering the contest. Hope I'm right. Enjoy listening each week. Welcome, Brett. We're very glad to have you on board. And now you've not only won, but we're going to be sending you a copy of Stellaris, People of the Stars, edited by Robert E. Hampson and the guy who's the principal investigator for Nia Scout, Les Johnson. So congratulations, Brett. Congratulations. Well, that was exciting. You got any more? I got two more funny ones here from perennial favorite Mel Powell in California. He says, 14 kilograms, a bit less than my favorite object, the Stanley Cup, which comes in at 15 and a half kilograms. I've never seen an NHL hockey player skate a lap while lifting a CubeSat over his head yet.

And finally, one we can all agree on from Thomas Ancillary in New York. Woohoo, solar sailing. Gnarly, my dudes. Righteous. All right, we can move on. We shall move on to this trivia question. We talked about Ganymede and of course there are three other so-called Galilean moons of Jupiter, Galilean satellites, Io, Europa, Ganymede, and Callisto. What did Galileo, who discovered them, what did Galileo want to name them after? Hint, it's not what they ended up being named go to planetary.org slash radio contest doesn't happen all the time but i know this one yes i'm gonna need to do a new one arch

all right well you enter the contest legally like everyone else i hope i win you've got until wednesday january 27th that'd be wednesday the 27th at 8 a.m. Pacific time. And if you win, we will award you a Planetary Radio t-shirt that you can see being modeled at chopshopstore.com or just go to planetary.org slash store. And you can check out all the merch from the Society. I apologize. Yours was a really good question and showed our audience is capable of advanced calculations. So now I can really let my mind wander. Look what I've created. Say goodnight, Bruce.

Goodnight, Bruce. All right, everybody. Go out there. Look up in the night sky and think about what you would name four moons. Thank you and good night. I'm going to get one out of the way right now so that none of you can do this really obvious one. Groucho, Chico, Harpo, and Zeppo. And Gummo would have been there if there was a fifth moon, but Gummo dropped out of the act, so to heck with him.

Maybe we'll find a small moon to name after Gummo dropped out of the act, so to heck with him. Maybe we'll find a small moon to name after Gummo. Planetary Radio is produced by the Planetary Society in Pasadena, California and is made possible by its very smart members. Learn how to join them at planetary.org slash membership. Mark Hilverda is our associate producer. Josh Doyle composed our theme, which is arranged and performed by Peter Schlosser at Astra.