...how engineers protect their spacecraft from failing?

Ever Wonder? / March 17, 2021

...how engineers protect their spacecraft from failing?

Tracy Drain, a JPL engineer, hugs a BB-8 robot
Image attribution
Courtesy of Tracy Drain
Tracy Drain and Nichelle Nichols both raise their hand in a Vulcan salute from Star Trek
Image attribution
Courtesy of Tracy Drain

Tracy Drain with one of her childhood inspirations: Nichelle Nichols, Star Trek’s Lt. Uhura. They took this photo in 2016, when Tracy was the deputy chief engineer for the Juno mission to Jupiter.

We are wrapping up our series on space exploration, with an inside look at what makes a mission to space successful. Have you ever been on a road trip, only to have your car break down and leave you stranded out in the middle of nowhere? Imagine how much worse that would be if you were on your way to the Moon, Mars, or even Jupiter! But going to space is hard, and even with teams of top engineers and scientists working together, sometimes things can go wrong.

Do you ever wonder how engineers protect their spacecraft from failing?

We spoke with Tracy Drain, a flight systems engineer at NASA’s Jet Propulsion Laboratory. She tells us how to use a “fault tree” to guard against failure, both before you put your spacecraft on a rocket for launch, and once it reaches its destination. Tracy has lots of experience doing this, working on teams like the Mars Reconnaissance Orbiter, the Juno mission to Jupiter, and most recently Europa Clipper. One of my favorite parts of this interview is when Tracy describes how the Juno and Europa Clipper spacecrafts have to survive in the intense and enormous donut of radiation around Jupiter.

Have a question you've been wondering about? Send an email or a voice recording to the podcast team to tell us what you'd like to hear in future episodes.

Subscribe to our show on Apple Podcasts, Spotify, or Google Podcasts. To see a full list of episodes, visit our show’s webpage.


Perry Roth-Johnson (00:06):

Hello! This is Ever Wonder? from the California Science Center. I'm Perry Roth-Johnson. We are wrapping up our series on space exploration, now with an inside look at what makes a mission to space successful. Have you ever been on a road trip only to have your car break down and leave you stranded out in the middle of nowhere? Imagine how much worse that would be if you were on your way to the moon, Mars or even Jupiter! But going to space is hard, and even with teams of top engineers and scientists working together, sometimes things can go wrong. Do you ever wonder how engineers protect their spacecraft from failing? We spoke with Tracy Drain, a flight systems engineer at NASA's Jet Propulsion Laboratory. She tells us how to use a "fault tree" to guard against failure, both before you put your spacecraft on a rocket for launch, and once it reaches its destination. Tracy has lots of experience doing this, working on teams like the Mars Reconnaissance Orbiter, the Juno mission to Jupiter, and most recently Europa Clipper. One of my favorite parts of this interview is when Tracy describes how the Juno and Europa Clipper spacecraft have to survive in the intense and enormous donut of radiation that surrounds Jupiter—it's wild! Tracy Drain, you're a flight systems engineer at NASA's Jet Propulsion Laboratory, welcome to the show!

Tracy Drain (01:32):

Thank you very much. Glad to be here.

Perry Roth-Johnson (01:34):

Yeah! And Devin Waller, my co-host at the California Science Center is also here today. Hi Devin!

Devin Waller (01:39):

Hey Perry, thanks for having me on. And hi Tracy, thanks so much for joining us!

Tracy Drain (01:43):

My pleasure. Absolutely.

Perry Roth-Johnson (01:45):

So Tracy, you've worked on some really cool missions to places like Mars and Jupiter while you've been at JPL. Uh, but before we dig into those cool stories, I just have to ask, what is a systems engineer? Are you kind of like, I don't know, a conductor in an orchestra or an executive producer for a movie, someone who's bringing lots of teams together to make a cohesive final product, but your final product is a spacecraft?

Tracy Drain (02:08):

That's not a bad way to think about it at all. Um, I also tend to think of systems engineers, both as a conductor and also kind of like the Swiss army knife of engineers. We kind of have to do everything. We have to know a little bit about how all the different parts of the spacecraft work together so that we can be helping the team make the right technical decisions on whether we should choose option A or option B if we have trades to do for example, or when things are not coming together exactly right on the spacecraft to make sure we get the right people in the room that we're asking the right questions in order to figure out how to resolve the problem.

Perry Roth-Johnson (02:43):

And when you tell people you're a systems engineer, do people ever have any funny ideas about what you actually do?

Tracy Drain (02:50):

They do. Just this past weekend, actually, a young lady asked me what my advice was in terms of doing a job that was more technical versus more managerial. And I'm like, whoa whoa ... I think people can get the idea that a systems engineer job is very heavily focused on things like cost and schedule. And while there is a little bit of an element to that, it is still way more about big picture technical problem solving. And so I find myself often giving people examples of some of the things that I've done as a systems engineer, which really helps make it a little more concrete for them. And one of the examples that I'll give you now for instance is say we are going to be flying a spacecraft all the way out to Jupiter, and you're trying to communicate back to the earth. Well, there are a few different options you can take in order to make sure you have a really good link to the earth and you can get all your data down. You can either have a ginormous antenna and lots and lots of power going through your telecom signal so that your signal is super loud from the spacecraft coming down to the ground, which makes it easier to pick up the link. Or you can have a somewhat smaller antenna, which is easier to launch the spacecraft and you can have a much more fine-tuned attitude control system. So you're pointing the center of that pattern much more directly at the antenna on the ground. That also helps you pick up your signal better. And so systems engineers would be working with people who focus on telecom and attitude control and mission design in order to make decisions like that on how we'll develop the spacecraft and the mission in order to have a good telecom link, for example.

Devin Waller (04:21):

So, Tracy, in your time at JPL, you've played a major role in some of the most exciting space missions that have explored the solar system. Um, you've worked on the Mars Reconnaissance Orbiter mission. That's still an orbit around Mars, the Kepler mission that discovered some of the, some of the first exoplanets, um, which are planets in orbit around other stars, the Juno mission, that's an orbit around Jupiter and you're working on the Europa Clipper mission, which is going to visit, in a few years, one of the, one of Jupiter's moons Europa. So I'd like to, you know, get a big picture question here and understand how does a space mission get created. And what's that relationship that push and pull between the scientists who want to get, you know, go out and explore those exciting new worlds and the engineers who have to develop the spacecraft and the hardware to make that happen?

Tracy Drain (05:14):

That's a really good question. So there's a couple of threads in there. There are multiple different ways that a space mission gets created, but it does always start with the science. What is it that scientists want to go off and learn, and what is the best way for us to get them the data that they need to be able to tease out the answers to those questions that they have. And the way things work at NASA, there are some missions which are just directed missions, where NASA says, we want you, a specific NASA center, to partner with these people and go off and do this mission. There are competitions that they have, like every couple of years, there's a Discovery Program announcement of opportunity where different NASA centers and different private aerospace companies partner together with scientists from the United States and around the world and put together concepts for missions. And they put together like just pages and pages and pages of documentation describing, what is the science we want to do? What is the basic idea around the spacecraft and the mission design? Are we going to send a spacecraft to orbit something? Is it going to be a telescope that's looking at something. And then, there's a big review board that goes over all those different proposals and down-selects to a handful to work on a little more and then selects a couple that actually become real. And there's multiple different competitions like that with different classes of money and different classes of, um, time that they have in order to do their projects. So a lot of different ways that those things come together.

Tracy Drain (06:36):

And the push and pull between scientists and engineers really makes my job very exciting because a lot of times the scientists will be focused on one particular area of inquiry for their entire career. And sometimes they will wait 20 years, 30 years in order to get an instrument selected, to go on a spacecraft, to go out and get some real data for them to have first crack at, as opposed to having to use data that comes from other people, who've had missions over the years. And so there's always this desire to do as much as possible to collect as much data as possible to like really push the edges of the capability of the spacecraft to get it all done. But on the engineering side, we like margin and we like to have redundancy. And we like to be very careful to make sure that what we're doing is going to work. And it makes us very nervous when we are, um, shaving margin or life doing fancy things that we hadn't necessarily originally envisioned with the stagecraft in order to eke out that last extra kind of data. So it's interesting. It, it fosters some really good conversations back and forth between the engineers and the scientists. And ultimately we all wind up doing a far better job than if we were like doing a purely tech demo mission without trying to get any science or, um, trying to push things so far that we end up breaking something in an effort to get all the science we possibly can.

Devin Waller (07:56):

So it's this, it's this tug of war a little bit between being conservative and keeping the spacecraft healthy and safe, but then also having, you know, going out and being a little risky because you want to get those most exciting discoveries and you want to find the really new, fun stuff.

Tracy Drain (08:14):

That's right. And the way we tend to do it is that when we design the primary mission, like when your spacecraft first gets to where it's going, and then you spend two or three or however many years, the mission is then we have a lot of rules that we all follow diligently about the way we're using the spacecraft to get the primary science that we're after. But then once you've finished all of that and you've accomplished your science goals, then we can start to push the envelope a little bit. And there have been missions for instance, that have like flown closer to their target because they are able to take a little bit more risks since they've gotten all their primary science. There have been missions that were never initially built to like fly through a plume on Enceladus, for example, but they might be able to do that when you're deep into your secondary missions and you've met all your science goals. And so you can take a little bit of risk in order to get some extra data.

Perry Roth-Johnson (09:03):

And, uh, like no matter where you're going, all these different spacecrafts, uh, need to guard against failure, especially, you know, before you've achieved those primary objectives. Cause like, uh, you know, there's no Home Depot on Mars or Jupiter to fix your spaceship if your breaks? Right. So, so help me understand, uh, like the work that you and your team do. How do you prepare for these possible failures before you put your spacecraft on a rocket for lunch?

Tracy Drain (09:29):

Yeah. We have this great thought process, um, which you can sum up in two words, 'fault trees.' And that's where you think about, you kind of start from the success-oriented thing. What are some major things that really have to go right in order for my mission to be successful and an easy one is launch. Launch needs to be successful and for a launch to ultimately be successful at the end of that launch period, you need to be on the right trajectory to where you're going. Your spacecraft needs to be generating power and not just draining your batteries 'til you die. You need to have all the thermal things across your spacecraft need to be at the right temperature. And nothing's like starting to get way, way too hot or way, way too cold. You need to have established communication with the ground so that you can send more command and the spacecraft can tell you how it's doing. So there are these high level success criteria. Launch is successful if this, this, this, this. And then you pick each one of those things and you say, well, let's take power, for example. What are the things that can happen to make my spacecraft not be power stable? And if you're a solar powered spacecraft, like all the missions that I've worked on, a lot of them have deployable solar arrays that have to be folded up to fit inside the launch vehicle, but then deploy on their own so that they can be pointed at the sun and start generating power. And so, okay. What if my solar rays don't deploy? Probably not going to be power positive. And then you go down that thread, what are all the things that can keep my solar rays from deploying? Or maybe the command didn't go out, maybe my computer rebooted, maybe a hinge got stuck and so on and so on. And then you take each of those things and you keep going. Well, what can make that happen? And you can think about it as building a tree. You start with the main branch and then you have bigger branches and more branches all the way down to the leaves on the end, which are specific faults that can occur. And then you go through and think about, well, how do I either make the design be such that that fault literally cannot occur? Check! Or, if that fault occurs, how will the spacecraft recover and still do the things that it needs to? And in that second case, a lot of times we have a backup component. So say I really need my star tracker to work so that my spacecraft knows the orientation and then can point the solar rays at the sun, or sun sensors we'll say. Oftentimes we use sun sensors when we first launch the spacecraft instead of star trackers. And then, well if that one doesn't work, you're toast! We'll have a backup and the spacecraft will figure out that the first one wasn't working and swapped to the backup. And so you'll still be on your merry little way. And then once you have the whole fall tree filled out, you've got your work cut out for you to go and prove to yourself, before you launch that, all the things you said were going to deal with the problem, will actually work and so you've got lots of analyses and tests and inspections to do to make sure it all hangs together. And so you can think about people who work on that whole aspect of the mission, fault protection engineers, which is a very heavily systems engineering flavor thing. We like our, the, the worst case failure scenario people to try to go and think of all the things that can and will go wrong and then do something about it. And the thing that is, well how shall I put this? We all know that we will never, ever, literally ever identify every single thing that could happen. It is our goal to find all the major things that can really end up being mission-ending, and then figure out how to leave ourselves some flexibility. So that if new and interesting things came up, that we weren't, uh, imaginative enough to come up with ahead of a time, we can still deal with them. There's either robustness on the spacecraft side, or we have contingency plans ready on the ground to go and like, deal with things in real time.

Devin Waller (12:57):

That's amazing to even think about what the fault systems engineers have to think about, that could go wrong. How many different things are we actually talking about?

Tracy Drain (13:06):

Oh, hundreds, hundreds of things. Yeah. It's and one of the things that is that makes the job not completely intractable is that from mission to mission to mission, a lot of those kinds of things are very similar. And so you can learn a lot from your past historical missions that you've been on, that your colleagues have been on, that we read about, right? We like to share lessons learned from other missions, and then you can spend some extra brain power thinking about, well, how are the ways, what are the ways in which this mission that I'm working on now differs from previous missions and try to make sure you're like squeezing out those areas extra hard, because there might be some of those new surprising things crop up in those areas.

Devin Waller (13:48):

Yeah, absolutely. How do you know when you've exhausted that list of what if's? Where's the end point to that, to which you can positively say, I know that we can't, you know, things do go wrong, but we've accounted for everything in our power and we're ready.

Tracy Drain (14:05):

Yeah. If I had a really crisp answer for that, I would ask for such a big raise. There's a, there's a few different things we do in order to try to, to try to gain some confidence that we have explored all the different areas. Um, but there are still, like if, if, if you hear about a spacecraft launching and someone offers to bet you $20, that nothing unusual will happen in that entire mission, like take the bet. Yes it willI will double it to $40 because, um, we all have lots of interesting experiences when spacecraft launch and on their cruise to where they're going and once they get to where they're going. Like all sorts of weird things happen because these, the robotic spacecraft that we build are so incredibly complex that they just, things can happen just at the right time or just in the right order or, you know, this thing happens. And simultaneously we never thought that X and Y would happen at the same time, but they do. And therefore this emergent behavior comes up. So it, uh, there's yeah. If I met someone who was capable of coming up with all the weird little things that would happen, like I would want to attach them to myself at the hip, never go to work without them again.

Devin Waller (15:19):

So, I want to dive in a little bit into the work that you're working on now. I know you've recently joined the Europa Clipper mission. What is its main mission goals? What are you going to be preparing the spacecraft to do?

Tracy Drain (15:30):

Yeah, this is so cool. So one of the reasons why the Europa is, is, uh, is a lovely, juicy science target is because it is one of the places in our solar system that might have all the right ingredients for life. When we think about life here on earth, life needs three kind of main things, water, chemistry, and energy to drive the chemistry, right? And on Europa that the moon scientists are, are pretty certain, it has a shell of ice and underneath that ice there's liquid water, like more than twice the oceans of the earth combined under the ice. So water? Check! And we think that it may have all the essential molecules that are necessary for life. There's this really lovely, hard to pronounce acronym called CHNOPS carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. And it's possible that comets and asteroids might've carried some of those chemicals to Europa when it was forming and over its history and other chemicals might've been deposited too. So chemistry, maybe. Check! That's one of the things that Europa [Clipper] is going to be exploring, and then energy right here on the earth. We think mostly about energy coming in the form of sunlight, bathing the planet. Well on Europa, the sunlight is all hitting the surface of the moon, and it was way less of it available out there. Like five times farther from the sun than the earth is you only get about like 4% of the light out there. And then most of the stuff that we would be interested in going on is way below the surface of the ice. Now, the reason that the water is liquid down there is because titled forces resulting in Europa, orbiting around Jupiter, kind of act to squish and pull and squish and pull the planet. And that creates a lot of stress and friction. If you think about holding a paperclip that you unbend, and then you bend it back and forth and back and forth until it breaks and you touch the end and it's hot. That's because of the friction of the material moving together. That's what happens to the moon as its orbiting Jupiter. And so it stays heated inside, which is what keeps the water melted under the surface of the ice. And maybe just like we have hydrothermal vents on the earth, there's enough heat mixing water and molecules with, you know, all those different, um, chemicals down there that that might be enough to drive life. Maybe I don't know, but it's exciting to think about. And I know that's one of the things that they, um, scientists are interested in, in probing it. So, I mean, Europa [Clipper] is not going to land. We're not going to dig through the ice. We're not going to send a little camera down there in order to be able to see it. But what we are doing is we have, um, magnetometers on board, which will help understand kind of the way that the moon is, how shall I say, organized inside. It's too bad I couldn't grab my friend and scientist Kevin Han to come and talk to you guys cause he has a really great explanation about why magnetometers help you understand that there is water and that it's salty water, for example. And we also have imagers on board, which will, which is a pretty straightforward way of just seeing what the surface looks like. And they'd be able to tell one of the things that's cool about Europa is that it's, it doesn't have that many craters on the surface. When you look at it, it's, it's quite smooth. It has these long streaks across it. Um, which I think the scientists are pretty sure cracks in the ice. And one of the things we'll be able to tell from getting really good images all around the planet is things like where you have tectonic plates that have slipped and you can see that they've moved relative to each other, might be able to see places where things have cracked and then maybe water has welled up and filled in the cracks. Um, we'll also be able to, to study the surface composition by spectrometers, where you can kind of look at the light, that's bouncing off the surface and break that into its components to tell what the surface is composed of. The spacecraft has like nine different instruments that are going to measure a variety of things in order to give us a lot of information about the moon.

Devin Waller (19:30):

I'd like to talk a little bit about your previous mission. You worked on the Juno spacecraft, that's been a few years in orbit around Jupiter studying its system. How did you prepare Juno for that environment and how is that influencing the way that you are planning for the Europa Clipper mission?

Tracy Drain (19:48):

Yeah, it's interesting because one of the things that I think is a little odd about the way engineers move around from project to project versus the way scientists do, at least my understanding of how scientist careers work, is that engineers can move from mission-to-mission sort of in the middle of the development process, right. Um, Juno, started off as a proposal, I think way back in like, 2003. Uh, as a New Frontiers mission being proposed. And it was selected and then the team was working up the design. It was a partnership between JPL and Lockheed Martin. And I joined the mission in 2009, which was just two years before lunch, after they had already done a huge amount of development work and already made a lot of the engineering choices on how to deal with the radiation environment at Jupiter. And so I was able to learn what was going on and then dive in with the team to work on maturing the fault tree and helping to do some of the testing associated with ensuring that all of our mitigations for all those faults, we're going to work among a bunch of other things. And it was interesting to me to learn about the way that that spacecraft was designed in order to deal with Jupiter's radiation. If you don't know much about the radiation field, I will kind of explain it in layman's terms. And in here I'm totally a layman myself as the engineer, not a scientist. And I think about it like this, Jupiter is like just an insanely huge planet. You can fit like 11 Earths across the middle of it. It's that big. And it doesn't have any solid ground, the way we think of ground. It's made mostly of hydrogen and then the next major component is helium. And as you go below the clouds deeper and deeper and deeper, there's just so much of it that it creates such a huge gravitational field that it just squeezes everything together so hard that eventually you reach a layer where it's liquid hydrogen and you keep going and the pressure and the temperatures are so intense that the little electrons that go orbit around the nucleus at the hydrogen atom kind of gets squeezed off and they're free to flow around. And the planet rotates so fast. Like our earth rotates once on its axis, every 24 hours. Jupiter, even though it's so much bigger, rotates once every 10 hours. And so now you've got these flowing electrons spinning, which creates a magnetic field. Like it's way more complicated than that. But in general, it makes this huge magnetic dynamo, which then extends out way past it. It's huge. It's way bigger than the planet. I think on the side facing away from the sun because the solar wind distorts it, it like blows out past the orbit of Saturn and this magnetic. Yeah. Like everyone go find some pictures, like go on Google and type in Jupiter magnetic field. It's just, it's insane.

Devin Waller (22:35):

We'll definitely have to do that. So it's because of it's the size, it's a, it's a big gaseous planet. And as you get deeper within its atmosphere, that gas becomes denser and denser and it becomes a sort of a liquidity metallic, hydrogen ocean, if you will.

Tracy Drain (22:52):

Yes. Look at you. Liquid metallic hydrogen. That is exactly what it is.

Devin Waller (22:56):

And it's the spinning of that, that creates this gigantic magnetic field.

Tracy Drain (23:00):

That's what I think. Now part of Juno plan, and the magnetometer scientists would be like, "well, actually, Tracy." Part of the reason why Juno went there is to study the details of this magnetic field and help the scientists understand, with a greater level of accuracy, like exactly what is going on in there. But this magnetic field traps, charged particles that are coming from the solar wind and that are getting blown around in the Jupiter system, like Io, the moon, spews out all that sulfur in its volcanoes, that stuff gets trapped in the magnetic field lines and accelerated along the field lines and then go crashing into the poles at the north and south and, and all of those relativistic particles, um, create the radiation field that surrounds the planet actually. So go fact check name to your own Google. There's a way better explanation out there. But, uh, but that, like, if you think of Jupiter, the planet sitting in a donut hole and a donut of radiation, that's, what's bathing that area. And so the spacecraft actually doesn't ... When, when Juno went it didn't orbit around the equator of the planet. It kind of goes in this big, you can think of it like a big flower pedal where one end is like tucked in inside the donut hole between Jupiter and the edge of that radiation field, trying to like thread that little needle and then kicks out which way, way, way out for a while, and then comes back in and it's in this 53½ day orbit. It doesn't spend a lot of time kind of grazing the edges of the radiation field. That's part of why we were able to keep the radiation dose on that spacecraft low, just in the mission design. And it also had a vault made of titanium that the sensitive electronics are inside of in order to protect it from the radiation field. And it, it takes the environment inside the vault down to more like what you see around Mars, which we're pretty used to building spacecraft for. But then there are things outside the vault, like there there's special coding on the solar arrays and there's special shielding on some of the other sensors that have to be outside of the vault in order to deal with that radiation. Now, Europa is a, is a more complicated story for the radiation field because while technically the Europa Clipper mission is still orbiting Jupiter, the point of the spacecraft is to do a lot of really close flybys of the moon Europa, which is embedded in that lovely donut of radiation and so that spacecraft ends up spending way more time in a higher radiation area. And so it also uses a vault for the sensitive electronics and just has to have more shielding in a lot of different places in order to deal with the increased radiation dose it's going to get over time.

Devin Waller (25:35):

Well, we understand that Jupiter has just many, many moons. I mean, we're talking like, I don't know, over 60 or 70 moons, the inner most moons and Europa is one of the bigger it's closer to the planet. It's sits inside that radiation belt. And so this, this mission is actually going to be bathed in a lot of radiation. This one you're going to have to do a lot of preparation to ensure that the spacecraft is safe.

Tracy Drain (26:00):

That's right. And it's great that we like a lot of the lessons that we learned from Juno and other missions in terms of how to build the shielding, how to do radiation testing and advanced analysis that you do in order to make sure you kind of understand how things are going to behave. We're putting all of that hard knowledge to use and designing and building the spacecraft.

Devin Waller (26:21):

So Tracy, we saw that, okay, you've met some of the actors from the TV show Star Trek. Now this got us excited too. Nichelle Nichols, who played Lieutenant Uhura, um, and William Shatner, Captain Kirk himself, um, we were excited to see this and we wanted to know, um, were you a big science fiction fan?

Tracy Drain (26:41):

I was!

Devin Waller (26:41):

And did that help to influence your path?

Tracy Drain (26:46):

A hundred percent. Yeah, my little mom, who's my favorite person on the planet. She is the person who got me addicted to science fiction shows when I was a kid. And because she's a little bit older than I am, her Star Trek was the original series, of course. And so we watched that a lot. And then when next generation came, we watched that together too. And the really, even though there were a lot of different things that I was interested in when I was a kid and from middle school, when it came time for me to choose what I wanted to do as a career, and I was trying to think like, what would actually be interesting for a good 30, 40 years? That's where, um, the idea of something involving space exploration really stuck, like to be able to do some things, to nudge the world more in the direction of those futures that I saw in Star Trek and Battlestar Galactica and all those cool shows is, is really something that I wanted to do. And so when I got the opportunity, because JPL is a really cool place and we're just fortunate to have people visit, um, both, um, William Shatner visited, he's visited a lot of multiple times and the Nichelle Nichols as well. When I had the opportunity to meet them, I was like super fan girl and sending pictures to my mom.

Tracy Drain (27:56):

Really, really fantastic.

Perry Roth-Johnson (27:58):

Awesome. Well, Tracy, thanks for going long along with us, uh, before we, we end it, uh, where can people follow you online and find your work?

Tracy Drain (28:06):

Folks can find information about all the missions that we talked about. If they go to nasa.gov websites, or if you just put in like, Juno mission or Mars Reconnaissance Orbiter, or Kepler or Europa Clipper. Psyche, we didn't mention but that's another great mission that I spent a couple of years on that's going to launch in 2022. So lots of places where you can find general info about the mission.

Perry Roth-Johnson (28:26):

It's been a pleasure talking to you, Tracy. Thank you so much for joining us on the show.

Tracy Drain (28:31):

My pleasure. Thanks for having me. It's been great spending time with you guys.

Devin Waller (28:33):

Thanks Tracy. Great talking to you.

Perry Roth-Johnson (28:36):

Well, that's our show, and thanks for listening! Until next time, keep wondering.

Perry Roth-Johnson (28:45):

Ever wonder? from the California Science Center is produced by me, Perry Roth-Johnson, along with Jennifer Castillo. Liz Roth-Johnson is our editor. Theme music provided by Michael Nickolas and Pond5. Special thanks to Devin Waller for producing and hosting this series. As we wrap up this series, we have two quick announcements. First, a big shoutout and thank you to Jennifer Castillo! This is the last episode that she'll be producing with us, as she begins a new chapter in her career. We're of course sad to lose our amazing associate producer, because we couldn't have launched this show without all of Jennifer's hard work to find and book us amazing guests. But we're also excited for her as she starts a new adventure, and we wish her all the best. Second, we are thrilled to officially welcome Devin Waller on as a producer for the show going forward! It's been so much fun co-hosting and recording these space exploration episodes with Devin, and we're really excited to have her be part of the production team. We'll drop new episodes every other Wednesday. If you're a fan of the show, be sure to subscribe and leave us a rating or review on Apple Podcasts—it really helps other people discover our show.

Perry Roth-Johnson (29:56):

Have a question you've been wondering about? Send an email or a voice recording to everwonder@californiasciencecenter.org to tell us what you'd like to hear in future episodes.