Planetary Radio: Space Exploration, Astronomy and Science - Julie Webster and the Art of Spacecraft Endurance

Episode Date: June 14, 2017

How do you keep a dazzlingly complex spacecraft in good health after 20 years in space? That’s the challenge for Julie Webster and her team of engineers supporting the Cassini mission at Saturn.Learn more about your ad choices. Visit megaphone.fm/adchoicesSee omnystudio.com/listener for privacy information.See omnystudio.com/listener for privacy information.

Hi, podcast listeners. I bet a few of you looked for the link to the Chop Shop Planetary Society store that was mentioned during the break in last week's episode. Well, oops, we jumped the gun. But that store is now officially and proudly open. And wait till you see the brand new Planetary Radio shirt there. Check out the other great merch while you're there. It's at planet.ly forward slash

space shop. While I've got you all, respectfully ask that you consider posting a review of Planetary Radio in iTunes and telling your friends about us in your favorite social media. Thanks for listening and sharing. The Art of Spacecraft Endurance, this week on Planetary Radio. The Art of Spacecraft Endurance, 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. Julie Webster heads the team that has kept the Cassini spacecraft healthy and working hard for 20 years. I'll talk with her as we reach the last three months of this epic mission. Bruce Betts will have a few revelations about Cassini in What's Up.

Jupiter may not get around much anymore, but Bill Nye will talk about that big planet's early days when it may have cruised the inner solar system. We'll begin with a story of deep impact from the Planetary Society's digital editor, Jason Davis. Jason, fascinating story at planetary.org, and it's something of a detective story. Yeah, scientists know that a long time ago, this giant asteroid or comet hit near Chicxulub, which is off of the Mexican Yucatan Peninsula, and that was probably what killed all the dinosaurs. But that's actually just one of many extinction events that have occurred throughout Earth's history, the biggest of which happened about 250 million years ago, and that was like 96% of life on Earth was wiped out. But we never knew what happened,

possibly until now. So that's, there's the great mystery intro. It's a great story, great illustrations, showing some of the pictorial versions of the science that led to this. But it really comes down to the work by three guys, one of whom is not only not a scientist, he's a citizen scientist, I guess, but did this partly with support from the Planetary Society. Yeah, this guy Max Rocha, he's in Argentina, went to study geology, but then ended up as a systems analyst doing IT work. Anyway, he pours through all of this gravity data. So when something hits the Earth and forms a crater, you can actually see it in gravity anomalies that show up where the gravity isn't as strong there as it should be, where kind of the land got smushed down.

So that helps these guys find hidden impact craters where something has been buried over millions of years and you can no longer see it just by looking at the landforms. This detective story starts in the 90s. This one person found this little anomaly but had no other evidence to support it. Our guy, Max, who's getting some modest funding through our planetary defense program, he followed up on this, took him several years to get some supporting data. And they've recently published a paper and say that they may have found this giant 250 kilometer wide impact crater near the Falkland Islands off of South America. So it's really cool.

So what is the current status of this possible discovery, this find? I mean, the evidence looks really good. Yeah, it does. They just need one more piece of evidence to kind of tie it all together, and that is the most expensive one, unfortunately. They need a drilling sample. So they need a ship to go out in the middle of this supposed impact crater, drill down beneath the seafloor and pull up a giant sample

and look at it. And if they analyze the rocks and it looks like they've kind of formed through this violent collision, that would be really the smoking gun, as one of the scientists told me, that says this is definitely a giant impact crater. And that could prove to be a major scientific discovery if it pans out that way. Well, you can read about the evidence and see some of it just off the coast of the Falkland Islands. It's all in this blog post by Jason Davis, the Planetary Society's digital editor, and he posted it on June 12th at planetary.org. Thank you, Jason. Thanks, Matt. On now to the CEO of the Planetary Society, Bill Nye. Bill, great story in today's first look about Jupiter and its travels across the solar system.

This is an amazing story. It's amazing, and it's amazing for Earthlings. current thinking by looking at asteroids is that Jupiter has crossed through the asteroid belt twice early on in the solar system's history. And that's how it got to be such a big influential gravitational body. But keep in mind, everybody, that Jupiter protects us earthlings from incoming meteors, meteorites and comets. So it's really a remarkable thing, a remarkable turn of events that Jupiter swept through the, if it's true, and it seems to be, Jupiter swept through the inner part of the solar system, picking up a lot more mass to give it these unique gravitational properties. And they call this the tack, like sailboat tacking. So apparently Jupiter tacked

through the asteroid belt, and that's how we're all here. So it's one more thing, Matt, when I think about the big picture of astrobiology, whether or not there's another living thing out there on another world. Other living things may have to be at an orbital distance, world, other living things may have to be at an orbital distance, orbital distance from their star that allows liquid water, and also have some big gravitational, can we say this word, badasses in their orbital vicinity, so that they are protected somewhat from incoming rocks. It's a really amazing thing. So this inference is not using data from the Juno

spacecraft. They're using data just from meteorites recovered here and observations of asteroids in nearby space. It's really an amazing thing. Science is cool. It's a good thing Jupiter doesn't charge us for this protection racket. Oh, I think it gets free food. It gets free material to add to its mass and influence. Happy to contribute. Thank you, Bill. Carry on, Matt. That's the CEO of the Planetary Society, Bill Nye, the science guy.

We're going to learn now from the person most in charge of doing it, how the Cassini spacecraft has managed to do such tremendous work for so many years. 20 years in space. 20 years of vacuum, extreme cold, radiation, and dust particle impacts. 20 years of valves opening and closing, rocket engines firing, reaction wheels spinning. Keeping the Cassini spacecraft healthy enough to do science through all of that is one of the greatest engineering successes we humans have ever achieved. It has been Julie Webster's job for two decades.

And she spent three years before launch helping to build the huge robotic probe. Julie manages the Cassini Spacecraft Operations Office. It was an honor to welcome her for a Planetary Radio conversation a few days ago. Julie Webster, thank you very much for coming on Planetary Radio and for visiting us at Planetary Society headquarters. You're welcome. This is the first time I've been down here. Although you said that you went to our old place. I have been to the old Green and Green Place when I was very new to Pasadena. Well, you're lucky because I love that old house, but we outgrew it.

As you could see, we kind of need the room. And I'm impressed with your new digs. And you have windows, which I don't have in my building. I'm impressed with your new digs. And you have windows, which I don't have in my building. I'm impressed with anybody that has windows. Yeah, somehow I think where you work still surpasses what we've got here. I mean, it's not bad what we've got. Aren't you like right next to, as you call it, the dark room? I'm about 40 feet from the dark room.

My office is about 40 feet from the darkroom. My office is about 40 feet from the darkroom. So I sit and listen. And if there's something that sounds a little honky, I'm in on top of them almost immediately. Because that's your job. Because that's my job. We're going to talk all about that. But first of all, pretty amazing times for Cassini. It is a pretty amazing time for Cassini. To be 98 or 97 and a half, however you count it, days from the end of the mission, it's exciting and it's scary at the same time. It's not scary. I'd be terrified. I'm glad you're not scared. No, I'm not.

Not terrified. No, I'm not. Not terrified. Was it scary when you went into this final phase and started diving between those rings and the planet? Well, you know, you talked a little bit about the science versus the engineers. So you have to remember that for the last four to five years, we've done nothing but, well, we've done a lot, but study this gap and make sure that the gap is there and that it's really clear and that it's not dusty and there's no atmosphere. So I was excited. I was nervous. I forgot to breathe several times on April 26th. And yet, it was truly exactly what engineers like it to be, a non-event for us.

It was right through in a clear space. Phew. And now, not that this mission hasn't been returning terrific science since even before it got to Saturn, because obviously there was the Jupiter flyby too. But now, holy cow, the stuff, the science that you are returning. The science is, you know, I don't do the science. I just keep the spacecraft safe for them to do the science for. But it's amazed and shocked me. When you step back and you look at it, and sometimes you look at the pictures and it's just utterly amazing. Say another word or two about your job. What do you do as part of this huge Cassini team? Well, I lead the team that's responsible for the health and safety of the

spacecraft. I've actually had four different titles, but I've had the same job for 23 years. That is take care of the spacecraft. Make sure that the spacecraft, power-wise, computer-wise, attitude-wise, everything thermally, everything you can think of, that it is ready to do the science that the scientists are asking it to do. That we're pointed in the right direction at the right time, that we're recording the data, that we're playing it back to Earth correctly, that we have the telecommunications link. And I have a team of about 25 engineers still that that's our job is to take care of the spacecraft

and make sure that it can do the science. I want to get an idea of how complex this machine is. For example, I read that there are nearly 200 separate electrical circuits. There are over 200 different microprocessors on it. That's even more impressive than I thought. There's about 10 miles of wiring. It's an amazing ring harness. Of course, we are the largest outer

planetary spacecraft that's ever flown. You know, at the rate we're going, it could be that we will always be the largest outer planetary. But the fact that we carry 12 different science instruments, plus the separate Huygens probe built by the Europeans. We are a large complex mission that was designed to put all your eggs in one basket. We're totally redundant on the engineering side. We have all the bells and whistles and we've had the good fortune and luxury to have had the time and money and people to, if anything minor went wrong, we could usually take care of it. Well, what kinds of things do go wrong? I mean, what problems have taken place?

And I already know a couple of things, but I wonder, what were some of the biggest challenges that you've had to face over this long, long mission? Well, one of the things, probably going into Saturn orbit insertion, because it was a 90-minute burn, and you're an hour and a half away out of communication with the Earth. So by the time we saw that the signal worked, it's over and done. The spacecraft had to be oriented properly, right? The rockets had to be facing the right direction, so the big dish wasn't pointing our way. That's correct.

And it's kind of an irony that that was never planned for us. You always turn in the direction that you efficiently burn your kind of retro rockets to slow down to get captured by Saturn's gravity. So we launched in 1997. In 1999, there were a couple of mission losses in Mars Polar Lander and Mars Climate Orbiter. And the NASA headquarters came back and said, oh, this is really terrible to not have communications on your spacecraft, so thou shalt have communications.

One of the engineering challenges was to figure out how to satisfy that link without turning into an inefficient pointing for the engines and causing a lot more fuel burn. We finally worked it out that the people that are radio scientists that grab signals like 10 or 20 dB decibels above the noise floor of the universe, tracked the low gain signal. And they tracked it right through. And as long as we saw the Doppler change on the low gain signal, we convinced them that adding telemetry and engineering data was not an added feature. I was at JPL on that day, and it was amazing. Because you had, like, the Doppler, right? For the signal,

you could see the frequency change as the spacecraft changed its velocity. Yeah, as we slowed down. Yeah. As we slowed down to get captured by Saturn gravity. There's two things that were going on. One was that you do everything you can to make sure the spacecraft all interplanetary, well, all spacecraft have a mode called safing, where if they hiccup, your computer hiccups, your, you know, circuit breaker breaks, your lights go off, whatever, that they will safe themselves. They will stop what they're doing. They'll turn and go into their most robust communication modes, find the sun, if they're solar pattern, find the sun for attitude control.

So we call it sum-con power, turn everything off that's not necessary. If we had safe during this time, we wouldn't have finished the burn. So we had critical sequences going that would take care of the spacecraft, fix whatever was broken, restart the sequence, restart it again. We even carried complete plumbing in another engine in order to accomplish this burn. Had we gone 45 minutes into the burn and the engine flamed out for some reason, we had the ability, the sequence had the ability to switch over to complete plumbing. So just to be clear, this would have happened if it had been necessary autonomously. The spacecraft was smart enough to try and solve a problem because after all, like you said, you got that light travel problem.

If it was in big trouble, you wouldn't know it for an hour and a half. That's right. So we did everything we could. We went down every rabbit hole trying to figure out anything that could go wrong, how to fix it, how to come back, restart the sequence of events to make sure that this burn completed. And of course, we didn't have to. We didn't go down any issues, Of course, we didn't have to. We didn't go down any issues, but we were ready for it. We probably spent a good part of two years testing maybe 10,000 different variations on the theme of the sequence for this burn. People wonder why it takes so long to put together a spacecraft like this and why, among other reasons, they cost so much? And I think you've just partly answered that. You have to take care of yourself. It has to be able,

it had to last seven years. We didn't even start the science. I mean, yes, we took pictures at Jupiter. Yes, we took some data at the two Venus flybys, but we didn't even get to Saturn for seven years, so it had to last longer than a lot of missions have to last total just to get to the science mission. So you make sure that you've got everything ready. What's the current health of Cassini? It's amazing. We are on backup thrusters because we had an early failure of a couple of the eight little small attitude control thrusters because we had an early failure of a couple of the eight little small attitude control

thrusters. We are on a backup reaction wheel because one of them got really squeaky. We do have a couple of other things that we've swapped, but in general, the spacecraft is completely healthy. And we should remind people, this is kind of, I forget how many extensions, it's at least the extended, extended mission. You are way past what was originally thought would be necessary to say this was a successful mission. Well, the prime mission ended in 2008. And then we had lots of spacecraft, lots of fuel, lots of power. Everything was working. So we did another two-year extension, and NASA typically does two-year, two-year, two-year, two-year.

But the scientists were smart enough to come in and say, well, two-year missions of what you want to do when you're doing unique orbits. Every orbit is unique. We weren't going around and around like on mars or like on venus we were doing a unique orbit every every single orbit so you had to kind of design it in toto it can't be broken up in pieces and so the scientists said well the only thing that makes sense is to take a seven-year extension go go into another Saturn season because of the 29-year Saturn orbit, the Saturn year, to go all the way into another season. So we did a seven-year extension, which is unprecedented in the history of NASA and interplanetary missions. And Linda Spilker has several times on this show talked about the tremendous advantages

to scientists like herself of being out there through so much of a Saturnian year, because it becomes a very different place as that planet makes its way around the sun. What it's meant, though, is that you've had to keep this machine running all this time. The spacecraft flying, yeah. My first thought in 29, when they said we'd like to do a seven-year extension, my first thought was, oh, that's great. I can take it to retirement. My second thought is, oh, my God, the spacecraft has to stay alive. It's just amazing how belt and suspenders this program is.

So we've done a lot of things to make sure. One of the things that we worried about the most is the biprop fuel. And that's probably the thing that we're almost out of, the bipropellant. The bipropellant? The large main engines. And that's why the mission's going to end, right? Because you'll just run out of gas. Well, we could have gone into some sort of Titan resident orbit. We could have gone into, there were different choices to be made. Actually, we could have gotten out of Saturn orbit and gone to another planet. You could have done this Titan resident, where kind of like they do around Mars,

where you fly around basically around the same pointing profile. Mars where you fly around basically around the same pointing profile there were there were options but the option of hey we'd like to fly through this gap inside the rings next to Saturn was so compelling and so different and such a new mission that in the end, the other ones were kind of a no-brainer. It's an expensive spacecraft to fly, to have 12 science teams keep the science going for 40 years as you fly to Neptune didn't make any sense. It made sense to do the best bang for the buck. Although I bet there were a couple of Neptune or outer planet scientists who were making their best argument to leave Saturn. I didn't even know that that was an option that had been considered until you mentioned it just now. Yeah, that was an option.

It wasn't a very big option. I would say that was a one percenter, but there were some options studied. But in the end, doing the grand finale was the thing that made the most sense. Yeah, it's very hard to argue with what is happening right now. in doing the grand finale was the thing that made the most sense. Yeah, it's very hard to argue with what is happening right now. You brought it up first because we had talked about it for a moment or two before we started recording this tug of war that is so often talked about in the media between the scientists on the mission and the engineers, the people like you, who obviously you know that it's out there to gather science, but it's your job to protect the spacecraft. I mean,

did you get any scientists who said, hey, how about when we're really close to the end, why don't we fly right through one of the rings? There were a lot of different proposals about how to do different things. And you just have to go back and argue back. But it's interesting, this started very early because as soon as we launched, we engineers, we were kind of a low cost operation. So we thought we were going to, quote, fly a rock, unquote. And we were just going to do engineering basically for at least the first four years. And as soon as the scientists saw that the spacecraft was stable and healthy, there weren't any thermal problems, there weren't any power problems, that everything was good,

they started clamoring for the science. Immediately, oh, let's do science at Venus. And then, you know, and we're going, the high gain has to point at the sun to keep the rest of the spacecraft cool while we're going by Venus. So we compromised. We worked some science at Venus 1. We worked some science at Venus 2. Jupiter really gave us the how to work together, how to let the scientists, we actually created a pointing control program

for them and then say, okay, here, design your pointing and we'll check it with our tools. But if you're good, you're good. There were a lot of things early on. And then you just get more and more comfortable. You try something out. If it works, you let it go. Julie Webster of the Cassini mission.

She'll be back after the break with much more, including her memory of sitting inside the spacecraft. This is Planetary Radio. Hey, Planetary Radio listeners. The Planetary Society now has an official online store. We've teamed up with Chop Shop, known for their space mission posters, to bring you space-inspired art and merchandise.

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Julie Webster manages the Cassini Spacecraft Operations Office. It's her team that makes sure the great spacecraft keeps delivering the images and other science data that have revolutionized our understanding of Saturn, its rings, and its mysterious, beautiful moons. So how do you go into a negotiation? You know, you're going to sit down with the science team, and they're going to say, we propose doing this. And the engineers have to explain, not a great idea. How do you approach that kind of thing?

Well, I start out with no. And then we go off and look at it and study it. And then we either come back and say, here's no and here's why, or yes, we can do this. Most of the time, it's been, yes, we can do this. I know there have been times in the media where they sort of play up this battle, this back and forth. And I'm sure it gets heated at times. It has to. But what I have always heard from the scientists, not just on this mission but every mission, is the amount of respect they have for the engineers

because they know that they're depending on you and your team to keep the spacecraft running. I think that's the trick. Engineers want to solve problems. They want to fix it for you. And things go wrong on the spacecraft, every spacecraft, as they inevitably do. And so the engineers will fix it. The scientists will come back with a good idea. And it's like, engineers like to fly kind of right down the middle of their comfort zone. And so the scientists will push you one way or the other. And we'll start out with no. And then we come back to, well, maybe.

And we'll start out with no, and then we come back to, well, maybe. And then we come back to, okay, if you compromise this, you can have that. There's some pitched battles, but it's less tugging back and forth than you would think. It's more negotiation. It's more negotiation. Yeah, makes sense. Before we go on, you said something about what had to happen as you were doing the flybys past venus using that big dish as a heat shield basically that's correct did the navigation people have to take into account going back close to the sun as the messenger mission people did the pressure

of sunlight absolutely solar pressure well solar we we still measure solar pressure today at 0.01 suns at Saturn. But there's the heat from the radio thermal isotope generators, the nuclear batteries. There's some heat there. There's heat from the sun. There's solar pressure. There's all kinds of small forces files that the navigators have had to compensate for all the years. And our navigation team is probably, not probably, is world class at doing this. They've done some amazing. We fly by Titan at, let's say, 1,000 kilometers. You fly in kind of a circle or an oval of approximate. We hit within a football

field of where we expect to be. And that's an amazing thing, just using a Doppler signal as your navigation. Yeah, it is a whole subset of the wonder of this mission and something JPL has a deservedly wonderful reputation for. It is one of our premier things. What happens on a day-to-day basis? What are the kinds of things that you, when you arrive at the lab in the morning, that you know you're going to have to take care of on a typical day? Well, it's interesting.

On Sunday, for example, which was the downlink for the last seventh flyby. We started the downlink. The station at Canberra could not find the signal. So my team got called in. We go through. We have an anomaly response process. We sort it out. Is it us?

Is it the ground? So we spent about five hours on Sunday looking for the spacecraft. It was not our problem. It was a ground problem at Canberra. But that's what we do. We come in. We find the spacecraft. If the spacecraft has had a glitch, we fix it.

We clean it up. We restart the sequence. We go from there. There's other things. Like right now, we're flying closer to the D-ring now. So we were lower in the gap. Now we're higher up, closer to the D-ring now. So we were lower in the gap. Now we're higher up, closer to the D-ring. And because we didn't know about the dust closer to the D-ring,

we turned our high gain to the dust ram. And we found it clear. So there's two of these, and then there's two more orbits that were lower, and then we're going back up into the D-ring. The very first thing the scientists asked for us, saying, back up into the D-ring. The very first thing the scientists asked for us saying, it's clear. Can you change the pointing profile for the next two orbits, which is literally over the 4th of July? Can you change and move it out so you can show more dust? Yes. Okay. We'll overlay the sequences we've got. So my team has to come up with a way to interrupt a turn, make a turn to the place they want to go, interrupt that turn, come back, and do it all in the well-timed choreograph of getting back to the next science objective.

Wow. Sounds challenging. It has been. It has been. It's been an amazing ride. Prior to Cassini, my average lasting on a job was two years. So I would go two years, two years, two years, sometimes four years. Now I've been on Cassini 23 years and it just seems amazing when I look back on it as to compared to the first 20 years of my career versus the last 20 years of my career. So you've been on this, I don't know, I guess almost as long as Linda Spilker and some of the other team. I didn't start on the science. So she started developing the program. I started when we

went into what we call ATLO, assembly test and launch operations. So when the spacecraft comes together as a system, I was down in the spacecraft assembly facility as a test conductor running the test as we put the spacecraft together. I went down to the Cape ready for launch, and then I came back as the spacecraft engineer at launch. And then I've just continued that job ever since. But it's been basically your professional life for over two decades now. Well, 30 years, 30 years on interplanetary. And I accidentally got there. I'm always amazed when you describe some of the things that people have built for you, that the people that started out as kids, as children, knowing they, oh, they want to work at JPL, they want to work at JPL.

I'm a chemist. So I'm totally out of my field. I'm a chemist. I have a little bit of master's work in mechanical engineering. I chased radionuclides around power plants. I was a chemist for a marine research lab. I did geothermal well water down in Magma, California. I accidentally got into aerospace and they didn't know where to put me. So they put me in telecommunications. How you may go from chemistry to telecom, I'm not real sure. But I found mentors along the way. And then I got fascinated with putting the spacecraft together. And I just was in the right place at the right time. So I'm one of those that accidentally fell into this. And then the first time I saw, I was a telecommunications engineer on Magellan after launch.

The first time we sent a command to the spacecraft and it worked, I was hooked. That was it. But I was in my 30s when I found my profession. Have you been thinking much about where you'll be and what you'll be thinking on that last day and when that signal disappears? I know myself well enough now to say I have no idea. I've gone through, it's already been a process of mourning of the actual end of this. I don't think that I wanted to prolong it much more. I think if we'd have gone into a Titan resonant orbiter,

it would have been time for somebody else to take this job. But to end it and to actually watch it burn into the planet, I just don't even know. I'll be in the dark room. I'll be in the mission support area. My team will be there watching it right to the bitter end. And up until one and a half hours before it's over, we could actually send commands if something didn't go right. You're going to be trying to keep that data stream coming as long as you can, right? That's absolutely correct. The spacecraft was not designed to send data back immediately. It was

designed to record the data, put it into, and then turn back to Earth and play it back. So we were not designed for real-time. So we've had to go in and design a special telemetry mode to do real time as fast as we can so that we can get the last bit of spectrophotometer data that we can before we lose. And we will actually lose the ability to hold the Earth in the signal before the spacecraft ends. So the spacecraft will actually, seconds to a couple of minutes later, disintegrate, but we'll lose the connection with Earth before that happens. What also strikes me about that is that even in these last days of this long mission, it is still evolving. It is still evolving. Like I said, these turns, you know, in three more orbits,

we want to turn and point the spacecraft differently than we designed. We are incredibly highly choreographed. Because all the science is body-fixed mounted, because it's all attached, bolted to the spacecraft, you don't have an antenna relaying to Earth while you're nadir-pointed with instruments. So the whole spacecraft has to point where the cameras want to point. The whole spacecraft has to point where the antenna wants to go. And it was timed in the early mission when everybody needed their science all at

once. It was timed down to the second. I've read that you have been to schools. You like to talk to kids about this. Tell them about your job and Cassini still happening. Yes, I love to talk to kids. I love to talk to schools. I actually quit a master's program. I walked out of the University of Utah many years ago, and I finally got over my embarrassment and called the University of Utah early last year. My master professor was still there. And I said, I just want to come back and give you a seminar on Cassini. I just want to tell you that I got a good education in spite of myself.

Wow. Yeah. And you got to do it. And I got to do it. And I've had multiple people come out for tours of JPL as a result. I am one of the millions, maybe hundreds of millions, who will not be in the dark room with you, but will be right there as this fantastic historic mission comes to an end. Best of continued success as we head toward that big day in, what is it, September? September 15th, 5.30 in the morning. I'll be up. That's okay. Our time. Yes, our time. It'll be

better for some people. Pacific daylight. Yeah. You Europeans listening to the show, you're going to be a little bit better off. And congratulations to you and your team for keeping this spacecraft doing what it has been doing for so long. And it is my team. It truly is my team that has figured out how some of the new young kids that come in with different skills and different fresh set of eyes that have kept this spacecraft really alive. Who hopefully are going to be able to go on to other missions and use this experience on those. Well, that's what we like to say. We trained them right on Cassini. Yeah. Thanks again, Julie. You're welcome. That's Julie Webster. She is the manager of the Cassini Spacecraft Operations Office, keeping that spacecraft going for so many years now, right up until the end, which is, as we speak, only about three months away. But my conversation

with Julie didn't quite end there. When I asked her if we'd missed anything, she told me three more stories. We have time to share them here in the podcast version of the show. I'm not the last person that sat inside Cassini, but I'm the last person still on the team that actually sat inside the spacecraft before we put the propulsion unit up where I was watching the engineering. So part of the feel of the spacecraft, part of understanding how it's doing and its idiosyncrasies and how it's working, was the ability to just sit there and listen as we turned on reaction wheels, as we moved things, as we articulated things.

I can close my eyes and I can see the spacecraft. I can see the inside of it. I can see how it functions. So this is you inside one of the big clean rooms at JPL, the high bay. Yes. Sitting inside the spacecraft. Spitting in where the electronics base. In the bus.

In the bus. Were you thinking at the time, oh, my God, this is going to be going to Saturn, and here I am sitting inside it right now? Probably I knew that better than I did on Magellan, because I have to tell you, I got certified to mate a connector because I had integrated the radar with the Magellan unit, and I convinced the technicians at the time that they should let me mate the radar. I did not know that that was going to cause me four months of no sleep until we turned on the

radar and it came on. I never tried to mate another connector. I let the technicians do that. Yes, I think by the time I got to Cassini, I knew that this was going to be an amazing spacecraft, an amazing experience. So, silly question. You didn't scratch your initials inside the bus there? I did that on Magellan. I bumped a—I ran a work platform into the corner of the high gain, which was a Voyager spare, by the way, on Magellan one night. And I had to go underneath the bright lights and all the management sitting there staring at you going, what were you doing? And what were you thinking? And why were you on the floor? And the high gain antenna engineer came out and he says, oh, Julie, it looks like you just carved a J in the back. So, no, I didn't have to do that this time.

Well, thank goodness. And that was a long time ago. That was a long time ago. And I told you the story about the university, which I'm very embarrassed about, or I was for a long time. I put that in all my talks. I tell people that I did not have a traditional route to JPL. I bounced around. I did a lot of different things.

I accidentally got on a NASA project, which was Magellan. It's not that you have to have a path that's so carved out. And when I talk to young kids, just keep up your math and eventually keep up your math and physics, and you can do anything. Time for What's Up on Planetary Radio. Bruce Fetz is once again on the Skype line. He is the Director of Science and Technology for the Planetary Society. In addition to his duties informing us about the night sky and random space facts and all the other good stuff he does.

So how are things up there? It's beautiful down here. It's beautiful up here. A lovely night to go observing. And wonderful things to observe include Saturn, which is at opposition on June 14th or 15th, depending on your time zone. That means it's on the opposite side of the Earth from the Sun, which in a practical sense means it's rising in the east around sunset

and setting in the west around sunrise. Good time to check out Saturn looking yellowish. And then we've got Jupiter still dominating the evening sky high up in the south, brightest star-like object up there. And then Venus dominating in the early morning in the pre-dawn east. We move on to this week in space history. It was 1963, Valentina Tereshkova became the first woman in space. And 20 years later, 1983, Sallyva became the first woman in space and 20 years later, 1983 Sally Ride became the second woman in space and first American woman in space.

And somebody that I still dearly miss. Yes, indeed. We move on to Your old guy voice did strange things to the internet. It's broken the Internet before. Turned it right off everywhere. The Cassini spacecraft, you know, I hear you learn things about that. Oh, you bet.

You'll want to hear this one. The Cassini spacecraft has two identical main engines that is used for large changes to the spacecraft's trajectory, and 16 smaller engines called thrusters, which control the orientation and make small changes to the spacecraft's flight path. Well, that fits perfectly with Julie's conversation with us, because she talked about how they went to their backup set of thrusters, and thank goodness for redundancy, right? Yep, yep. Cassini had all sorts of good redundancy, thankfully. We move on to the trivia contest. And I asked you, what star has the largest proper motion? So basically observe changes in the position of a star relative to the background stars. How'd we do? I'm going to start not with the winner, but with the description of this star from Nathan Hunter in Portland, Oregon.

He said, it's the greyhound of the skies. Would it be Barnard's star? Not very far away. Has the largest proper motion of all stars. That's what we heard from Dave Kirkland in Plymouth, Michigan. Long-time listener. Corresponds with me now and then. Sends notes.

But I think a first-time winner. He's got it right. Yes, indeed he does. Thank you. Thank you. And Dave, congratulations. You have won a Planetary Radio t-shirt and a 200 point itelescope.net astronomy account. You can use it to do astronomy all over the world because they've got telescopes all over the world. Let us know how it goes. Was there anything else you wanted to tell us about Barnard's star? As you mentioned, it's relatively close.

It's six light years, which to have a large proper motion, you pretty much have to be comparatively close. So after the sun and Alpha Centauri system, it's the nearest star to Earth that's known. How fast is it moving? Well, it's moving so fast. 10 arcseconds per year is what we heard from most people. And Ron Bask of Milford, Connecticut, put it in the kinds of terms that we like on this show. 10 arcseconds is equivalent to a human hair at one meter, or roughly two arm lengths on average. Does that sound about right?

Sure. I got to stare. Just a second. I got to pluck a hair. No, it's a small angle, but it's not small relative to watching stars as they move from one year to the next. It's going to be so tempting to drop a little, you know, plink hair removal sound effect in there. Clem Unger. Here's a random space fact. Barnard star got officially named only in, well, early this year, he says,

being known for over 100 years. I didn't check on this, so we'll have to take Clem's word for it, unless you know for sure. No, I do not. Well, Torsten Zimmer, out of Germany, he said, yeah, this is the star with the greatest proper motion. Other stars, like Madonna and Beyonce,

are better known for their improper motions. Oh! I know, that one hurt. But here's my favorite, from Casey Mishlevy. Come on, baby, do the proper motion. Come on, come on and do. Come on, sing along. Do the proper motion with me. You've got to swing your corona now, Casey. Take it. Thank you, Casey. We're sorry and we apologize to Motown Records. Please take us to the next contest.

I don't know if you may have discussed this in your interview, but what fuel do the Cassini spacecraft's 16 thrusters, not the main engines, the thrusters, what fuel do they use? Go to planetary.org slash radio contest. I am fairly certain that did not come up, so it should be a perfect question. And if it did, then none of you have any excuse for not getting your entry to us by the 21st. June 21st, that'd be Wednesday at 8 a.m. on the 21st.

We're going to pick somebody, or random.org's going to pick somebody with the right answer, and give them a Planetary Radio t-shirt about which there is going to be huge news and a 200.itelescope.net account, and we'll throw on a Planetary Radio sticker. How's that? That sounds excellent. Can I have that? I'll give it to you for the staff price.

Oh. All right, everybody, go out there, look up at the night sky, and think about pillowcases. Thank you, and good night. So you just pick out whatever you see in the room at the moment you need to come up with something, don't you? I cannot give away my secrets to the advanced way in which I come up with those things. Well, I'll tell you what. Sometimes I come up with clever things. You do. You do indeed.

Not so much this time. Well, you know, I think people don't think enough about pillowcases. They serve a valuable function, and yet all we do is just stick our head on them. You know what? That is so profound, I think I'm going to sleep on it. Yay! Nice. That's Bruce Betts. He's the Director of Science and Technology for the Planetary Society, who joins us every week here, right after his nap, for What's Up.

Planetary Radio is produced by the Planetary Society in Pasadena, California, and is made possible by its enduring members. Danielle Gunn is our associate producer. Josh Doyle composed our theme, which was arranged and performed by Peter Schlosser. I'm Matt Kaplan. Clear skies!