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Charlie Sobeck Talks About Kepler’s Upcoming End of Flight

Season 1Mar 15, 2018

A conversation with Charlie Sobeck, Kepler’s former mission manager and now system engineer at NASA’s Ames Research Center in Silicon Valley.

Charlie Sobeck

A conversation with Charlie Sobeck, Kepler’s former mission manager and now system engineer at NASA’s Ames Research Center in Silicon Valley.

Transcript:

Host (Matthew Buffington):Welcome to NASA in Silicon Valley episode 82. This week we’re talking to Charlie Sobeck, the system engineer for the Kepler space telescope — NASA’s first planet-hunting mission. Charlie has been working on this mission here at Ames since 2001 and has held various roles in getting this spacecraft off the ground and keeping it humming along in deep space. This month marks the 9th anniversary of Kepler’s launch, and it’s a bit of a bittersweet moment. Kepler is expected to run out of fuel within several months, and that will put an end to an amazing run of scientific data collection that has truly changed our view of the night skies.

But if you are a fan of the podcast, you might recognize Charlie’s voice from back in episode 54. You can check out that episode for his background on how he joined NASA. And also for next week, we’ll have another special Kepler episode with two of our podcast vetrans, Geert Barensten from episode 47 and Jessie Dotson from episode 40. So, stay tuned for that new episode next week. But for now, let’s jump into our conversation with Charlie Sobeck.

[Music]

Host:Happy to have you with us. Our returning Jeopardy champion, Mr. Charlie Sobeck. How’s it going?

Charlie Sobeck:It’s going great. How are you doing?

Host:I’m doing good. I think the last time that we had chatted I think you were still the project manager for Kepler at that time, I think.

Charlie Sobeck:I think I was, right.

Host:So, for folks who are listening if you weren’t aware, you can hop on to our landing page. And the first episode that we did with Charlie we did the whole background. How he joined NASA. How he got involved, and all of that fun stuff. But today we’re talking a little bit more about Kepler. We’re talking about, “What’s the final swan song for Kepler?” And I also have Alison.

Alison Hawkes:Hi. This is my debut.

Host:Exactly. And so, we’re not going to go in to depth on “everything Alison.” She’s on our communications team. And so, you’ll start hearing her voice more and more. Especially, as attention to Kepler and exoplanets starts ramping up. We can just touch base, Charlie, on what’s happened since we last chatted, or what’s going on in your world?

Charlie Sobeck:Well, you mentioned that my last time here I was the project manager, and I’ve stepped down from that role. We’re trying to build new project managers here at Ames so I’ve turned the reins over to my deputy, Maura Fujieh, and she’s managing the project.I’m still very much attached to Kepler so I’ve taken on the job of project system engineer helping to close out the mission as it winds down here.

Host:Let’s talk a little bit about that. We’ve chatted with a lot of people related to Kepler. People ought to be familiar with Jessie Dotson, and Geert Berentsen so what are we looking at in this future? And Alison specifically, you’ve been working with them hitting the ground running. Learning all things Kepler as well.

Alison Hawkes:Yeah, and we have an important date coming up. March 7th is the nine-year anniversary of Kepler which is so cool. It’s been up nine years, and this will probably be the last year that we celebrate a live spacecraft, right?

Host:And so, let’s talk a little bit about that. For folks who aren’t fully aware, I think most people if they’re listening to a NASA podcast, they’re interested. We’ve done a lot of content around Kepler so we all know it’s looking for the first space telescope from NASA confirmed exoplanets. It had the first mission finished out. We’re in the K2 mission now, but as all things eventually come to an end or really, I don’t know, even when it comes to it there’s still tons of science that come after that.

Charlie Sobeck:Oh, yeah, the spacecraft operations will come to an end. We think that the mission data is going to be used for decades. Oh, yeah, it’s going to be a wealth of information.

Host:So, it’s kind of like a weird misnomer where even when it’s over, it’s not really over.

Charlie Sobeck:Yeah, we’re using the term, “end of flight.” It’s not the end of the mission. It’s certainly not the end of the science, but we are approaching the end of the flight mission. The spacecraft itself can’t live forever.

Alison Hawkes:Could you say a little bit more about what that means, Charlie? What does “end of flight” mean, and where are we in this final phase of the life of the spacecraft?

Charlie Sobeck:Well, the first thing I would do is to point out how fortunate we are because “end of flight” could mean anything. And for some spacecraft end of flight happens about 10 minutes after launch. There’s a big failure, and it never gets to orbit. Okay, we’ve passed that. Our original mission was supposed to be 3.5 years when we launched. The Kepler mission ran for four years, so that got finished, and then we lost a couple of reaction wheels, and we couldn’t continue the Kepler mission. We took a year off to figure out how to continue and do this fabulous K2 mission that we’ve done.

And we’ve been doing the K2 mission now for four years. So again, we’re really lucky. We’re nine years past launch. We’ve taken four years of Kepler data, four years of K2 data, and only now are we really seriously starting to talk about the end of flight where the spacecraft just can’t continue operating. If nothing else goes wrong we’re going to run out of fuel, but we’ve dodged a lot of bullets. We didn’t fail on the launch pad. We got to orbit. We haven’t been hit by a meteor — so let’s focus on the positives.

Host:It’s like we’ve been in overtime, and how rare is it that you’re sitting in overtime for almost the same duration of what the original game was?

Charlie Sobeck:Right.

Host:So, it’s all bonus from here on out.

Alison Hawkes:Yeah, it’s also curious. We’ve been talking a lot about fuel supply and the indeterminate aspect of it. Charlie, you have such a great way of explaining why it’s actually difficult to estimate fuel supply on a spacecraft and even in a car.

Charlie Sobeck:Yeah.

Host:Yeah.

Charlie Sobeck:Fuel is hard to quantify in any sense. Even your computer that shows you how much electric charge is left in your battery.

Host:It’s never quite accurate.

Charlie Sobeck:It’s never really very accurate because you just don’t know how much is left there. I make a point that in my car with a hundred years of technology behind it, I can look at the little needle. It goes to empty, and it will hover there for quite a while. After a while the little light goes on, and I’ve learned that when the light goes on I can pull in to a gas station, fill up the tank, and I have a 16-gallon tank, and it only takes 14 gallons to fill it. So, when that light comes on I’ve learned that there’s now two gallons left. I have some time.

For the spacecraft, there’s no gas station, so we can’t do that exercise. We can’t calibrate it. When the light comes on, when whatever indicators we have say things are getting low, the best we know is, “The end is approaching,” but we really can’t say when or how much fuel there is left. We have a number of ways we can estimate the fuel, but the answer is we’ve never emptied the tank so we never really know.

Host:So, I’m going to dig a little bit in to the weeds. What is the fuel? I’m guessing it’s not gas.

Charlie Sobeck:Technically, the fuel is hydrazine monopropellant.

Host:Oh, of course. At your local gas station.

Charlie Sobeck:Right, so it’s a fluid that doesn’t need oxidizers in our fuel. It’s just one fluid that when it goes through the thrusters it ignites, and it provides thrust. It’s pressurized in the tank, and that’s what drives it in to the thrusters, down fuel lines just like you have your lines in your car, and that is being pushed out by an air bladder within the tank which was pressurized. So, as we use the fuel, that bladder expands and keeps pushing the fuel out of the tank and down the lines.

Alison Hawkes:And where are we at right now with that? We’re pretty close to the edge, aren’t we?

Charlie Sobeck:We calculate we are. As I say, we’ve never been able to calibrate it. We’ve never been able to do this exercise of pulling in to the service station, refilling it and find out exactly how much we’ve used.

Alison Hawkes:And what does that look like when you run out of fuel? Why is that such a game-changer? Maybe this sounds like a dumb question, but what is the fuel used for? I know there’s solar panels on the spacecraft so could you just re-jigger those for a power supply?

Charlie Sobeck: Well, yeah, so we do have a solar panel, and it produces electricity. It’s used to run all the electronics onboard the spacecraft. In fact, those reaction wheels that we use to help point are electrically run. They spin up the masses, and so forth, to provide stability in pointing. We don’t actually move the spacecraft. We don’t, what we call, translate it. There’s no rocket engine to put it in a different orbit. It’s in whatever orbit it’s going to be in so what we use the fuel for is to change the pointing of the spacecraft. We want to point the spacecraft at a certain target. We want to point the antenna at the Earth at times. That’s what we’re using the fuel for.

Even when we use reaction wheels to point the spacecraft as the reaction wheels push against the solar pressure they are losing momentum, and we’ve got to refurbish the momentum. We’ve got to replenish the momentum in the reaction wheels, and that’s done with the thrusters as well. So, the fuel is all about keeping the spacecraft pointed where it’s supposed to be. That means when we run out of fuel we’re not going to be able to point the spacecraft anymore.

Host: I think of my phone as it starts turning yellow. Your power is getting low. You put it into low-power mode. Or maybe you turn off some settings to try to save as much as you can. Even when you’re driving a car when that fuel light comes on maybe you’re a little more efficient as how you hit the gas.

Charlie Sobeck: No more jackrabbit starts. You’re going to try to coast as much as you can.

Host: Exactly. I guess it’s the same idea. You guys are trying to conserve as much as possible? As much as you can?

Charlie Sobeck: That’s been our guiding principle for four years now. Kepler itself was pretty efficient. We weren’t too worried about fuel at that time. We had launched. We had a full tank. Who cares when you have a full tank, right?

Host: Yeah.

Charlie Sobeck: When the reaction wheels failed, and we started to use more thrusters, we used more fuel, we were becoming more conscious of it, and we started instituting fuel efficiency measures and so forth. When we started the K2 mission we were pretty fuel-efficient. We weren’t as fuel-efficient as Kepler was because it was designed to operate in the Kepler mode, but in the four years that we’ve been operating we keep getting more and more efficient in our usage.

When we started K2, we have these campaigns where we look at part of the sky for three months at a time. We guessed that we could do maybe 10 campaigns. That was what we thought the fuel could accommodate. Well, here we are. We just finished campaign 16.

Host: Oh, that’s crazy.

Charlie Sobeck: And we’re still talking about, “When is the fuel going to end?” So, we’ve gotten better, and I think we’ve gotten as efficient as we can so I don’t expect further improvements at this point.

Host: I think from when we last talked a lot of your career has been juggling that science and also, the engineering as a project manager. You get to play in both of these worlds. How is that going? Because I love talking about these big machines. It’s fascinating. Human beings have put this stuff up in space, and we’re learning about the universe, but as cool as the big toy is — expensive toy — you’re doing it for a purpose. It’s all about the science. At the end of the day that’s the most important part of it all.

Charlie Sobeck: We’re all working just for the science. I consider myself an enabler. My goal is to enable the science. It’s interesting when you think back on the Kepler mission, because if we had not had these reaction wheels fail, we would be here in year nine of Kepler operations. Which would have been great because the longer you operate, and you’re looking for planets in larger orbits we’d be seeing planets around stars that are in Mars-like orbits. Not just Earth-like orbits. We’d have even more planets and more habitable-type planets, which would be great. On the other hand, what would we have lost? The K2 mission results have been stupendous. Looking at different parts of the sky. At different kinds of stars. At solar system objects. At supernovae. We would have lost all that because we would have been exploring the Kepler mission. So, I don’t know whether it’s been a net plus or a net minus. In the end, both missions have been really, really valuable and more than worth the cost that we’ve been paying for them.

Host: One thing I get a kick out of, and we had it before. We’ve spoken with Geert as he came in. Kepler, it’s not just a NASA thing. The data is out there. It’s the scientific community. It’s this huge group, and a big part of even the project itself is working with the scientific community to get them the data. To get it quickly. To let people know how stuff is going on. And so, an aspect of also, in our world, and I know something that Alison has been working on is, “How do we get that out to people?” You do, you let people know what’s to come and helping people understand, “This is what the lifespan looks like.” So, Alison, how has that been for you or how is that working out?

Alison Hawkes: Yeah, it feels like every day we field new discoveries and exciting things that we could be talking about, and communicating to the public about. It feels like there’s a real treasure trove here of material that keeps coming out of this data. It’s really exciting to see that.

Host: Yeah, and so, and I know even related to that — spoiler alert to people that we record the podcast in advance. So, looking in to the future running through, “This is what it looks like,” Charlie, you’d finished up a letter that we’re going to eventually have out there. And Alison, I know you’ve been working with him on that so is that basically, spelling out what we’re talking about here?

Alison Hawkes: Yeah, pretty much. We want to let the public know that we are at this final phase of the mission. Kepler has accomplished so many great things, and here we are. We’re in the end game right now, and we will be seeing that play out over the upcoming months and just give everyone a heads-up that this is where we are. Charlie, how do you see it?

Charlie Sobeck: Oh, yeah, I think that Kepler is a global phenomenon, the data that we get, and that’s true of a lot of missions that have survived a long time. The Hubble mission has been a global resource for people. So, whether you’re talking about the science community, which is working actively with the data from both missions, both Kepler and K2, and publishing at a dramatic rate, or you’re talking about the general public who follow these kinds of missions. All of this material we’re trying to be as transparent as we can. Put it all out there. Everybody should share in the excitement. This has been a terrific mission.

Alison Hawkes: It’s always amazing to see how much attention and interest this mission really gets. And how the public really craves this kind of amazing discovery that we’ve seen. That’s just so gratifying to be able to put that out there, and generate that kind of interest, and explain this kind of science. And really hold up the scientists and the work that they’re doing and the mission is doing. It’s really quite incredible.

Host: I know at least in my world of trying to communicate the cool stuff that people at NASA are doing, it’s like whether it’s social media, it’s live events, no matter what it is, you can guarantee that there’s questions about exoplanets. There’s questions about this stuff. It’s just one of the highest points that, like everybody is just frothing. Any time we do any kind of an announcement or a thing people are like, “Oh, my gosh. What’s going on?”

Alison Hawkes: I was at the American Astronomical Society meeting earlier this year, and I was talking to some folks there about how, just 10 years ago, you would go to these meetings and exoplanets was totally fringe. You were not among big company to be an exoplanet researcher. And now, it’s like every panel has exoplanet discussions and papers, and it has totally blown open the field of this particular field in astronomy. That’s just so exciting to see.

Host: And it’s not over because they have TESS [Transiting Exoplanet Survey Satellite] that’s launching. You have JWST [James Webb Space Telescope]. Almost all of the time we’re talking about new space telescopes. Exoplanets are in there.

Charlie Sobeck: Yeah, and whether it’s exoplanets or other discoveries that the Kepler mission has made our project scientist for Kepler, Natalie Batalha has long said that, “We went from this backwater branch of science in to the forefront,” where she claimed that, “Every astronomer in the world in some way is using Kepler data.” This summer we had a Kepler Science Conference, Kepler/K2 Science Conference. And on the final day of that conference she did a little experiment which I thought was really interesting with 300 people or so in the audience there.

She got up in front, and took a microphone, and asked, “Could everybody who has published a paper using Kepler data please stand up?” And half or two-thirds of the audience stood up. “Will everybody who has received their Ph.D. by using Kepler or K2 data stand up?” And she just added these more and more things. “Have you used Kepler this way? Have you used Kepler that way?” At the end of which there may have been have a dozen people that were still sitting and Natalie said, “I could continue and eventually, I’d get everybody to stand up.” But it proved her point. Everybody is using Kepler data.

Host: Yeah, and I remember recently chatting with Jessie Dotson about the follow-up of the crazy thing about even K2, it’s not even about just exoplanets. There’s nebulas. There’s other space stuff. There’s so much stuff that’s even beyond what we thought that the telescope would eventually be able to do.

Charlie Sobeck: Absolutely.

Host: So, it’s above and beyond all of that. It’s just crazy.

Charlie Sobeck: It shows you the serendipity-ness of having lost those reaction wheels. Bad news for Kepler. Wonderful news for the science of K2. We never would have been able to do that mission without that failure.

Alison Hawkes: Yeah, and Charlie, I remember we’ve had a lot of discussions about what, in terms of the end game here. Collecting that last — squeezing every bit of science data as possible from the spacecraft before it runs out of fuel. Can you tell us a little bit about how you do that, and how do you bring as much data home as possible at this stage of the mission when it could run out of fuel at any point in time? I know you’re monitoring the fuel supplies and looking for signs that it’s going in to a very low-fuel state.

Charlie Sobeck: Yeah, so bringing data back from the spacecraft is a really challenging job these days because it’s so far away. It’s more than 90 million miles from Earth. It is as far from the Earth as the Sun is from the Earth.

Host: Oh, wow.

Charlie Sobeck: In a different direction, but it’s the same time. So just as it takes light 8.5 minutes to get from the Sun to the Earth, it takes radio waves 8.5 minutes to get from the spacecraft to the ground or visa-versa. It takes 17 minutes when we send a command before we’re going to see the spacecraft respond to it. So, it’s a long ways away, and the signals are now very weak.

What we do with the K2 mission is that when we’re gathering science data for three months, we’re not bringing it to the ground. We’re storing it onboard in a recorder because the spacecraft isn’t turned towards the Earth, and we can’t bring down data at a high rate. So, at the end of the campaign we turn the spacecraft, and it’s got one high-gain antennae with a dish. A parabolic dish that focuses the beam, and it can focus it on Earth. We can bring that data down that’s stored on the recorder. That’s how we get data down from the spacecraft.

With the fuel starting to show signs of running out, the worry is that you start a campaign. Let’s say you get two months in to the campaign when you run out of fuel. Well, you’ve filled the recorder two-thirds full, and you have all that wonderful science data. It was there onboard, but you didn’t get a chance to bring it to the ground.

So right now, our challenge is to monitor the fuel closely enough that when it shows signs of really not doing what it’s supposed to do, that we’re not getting the pointing that we wanted, that we’re not able to spin up the reaction wheels, something like that, that we raise a flag so that whatever fuel we have left we can bring down the data we’ve recorded. The data that we’ve spent so much time and effort to get, we want to get it to the ground. It doesn’t help us if it lives on the spacecraft forever. We’ve got to get it to the ground.

Alison Hawkes: One of the really cool points that you made in your letter, Charlie, was how we can afford to operate this way with Kepler being in deep space. Whereas, more Earth-circling satellites and spacecraft can’t. You have to use up your remaining fuel supplies to get it out of orbit so it doesn’t land on somebody’s house. Or the planetary missions like Cassini.

They were really worried about it crashing into [Saturn’s] moon, so they had to use remaining fuel supplies to send it in to Saturn. But Kepler is a special spacecraft. It has a special mission in the sense that you can let the fuel run dry, and that’s not something that other missions can afford to do which is interesting, I think.

Charlie Sobeck: Yeah, there are different types of NASA missions and so, they all end in different ways. There are near-Earth missions where you have to worry about the final end of the spacecraft collision. It could collide with a satellite. You don’t want it to collide with the International Space Station. You don’t want it falling uncontrolled in to Earth’s atmosphere and landing on somebody’s head. So, they have to have fuel remaining at the end of their mission to put themselves in a safe orbit and not let those kinds of bad things happen.

There are another class of missions that are planetary kinds of missions. Missions at Mars. Missions at Jupiter. We recently saw Cassini where they purposely sent the spacecraft hurtling into the atmosphere of Saturn rather than risk running out of fuel and having it collide with one of the moons that could harbor life, contaminating that moon.

A third class of spacecraft — and Kepler resides in this third class — don’t pose any particular risk to Earth or satellites or to habitable environments. We can afford to run until the thing just doesn’t work anymore. Whether it’s because it runs out of fuel or because an electronic component finally fails — another reaction wheel fails in our case — or whether we just run out of funds, and it’s just not worth pursuing anymore. We can run to the very end.

In Kepler’s case the very end is likely to be the fuel, and that’s not something that commonly ends the spacecraft mission — a NASA mission. So, in some sense, this is new territory for us. We’ve asked around, and not a lot of people have any experience in running a spacecraft to the end of fuel.

Alison Hawkes: You don’t even have to send the final commands to shut it down. That’s not even required in a situation like this, right?

Charlie Sobeck: No, we can just let it go until it quits working on its own. It’s like driving your car down the freeway until it runs out of gas, and you don’t have to worry about anything. As long as it’s an empty freeway, if you’re on the Salt Flats in Utah you can do this kind of a thing, but the spacecraft is in no-man’s land. It’s out in the middle of nowhere, and we can let it just go until it dies. We can leave it in whatever state it happens to be in. That’s okay.

Host: Out of curiosity, back in 2009 we were looking at launching — or even just the inception of coming up with this. The end of flight had to be in that process. You guys were planning this even before launch. There had to have been some assumptions or thoughts about, “This is how it would look like.” Is it completely different? I’m just wondering what our knowledge now compared to what we knew before launch — how that shook out?

Charlie Sobeck: I think that the answer is we’re exactly where we expected we would be.

Host: Okay.

Charlie Sobeck: We didn’t have to make it clear at launch because we were in this third class of missions. If you’re in one of these other classes part of the launch certification is to say, “You’ve got to know how this thing is going to end. What’s your end game plan?” For our mission our end game plan was, “We’re going to be out in no-man’s land. It doesn’t matter what happens to the spacecraft so we don’t need to plan it now.” Everybody knew that, and agreed to it, and that was one of the criteria for launch.

And now, here we are. It hasn’t really changed. We don’t really care how it ends. We can leave it in whatever state we want so we hadn’t given it a lot of thought. Now that we are here most of our thought is going in to, “How do we get the most final science off the spacecraft and down into the hands of scientists before it goes in to that final resting spot?”

Alison Hawkes: And I know probably a lot of people will ask this question — what does happen to the spacecraft in the end? You lose contact. It’s like space junk out there. Does it ever come back?

Host: Can you go out and get it?

Alison Hawkes: Can you go out and get it? Will it ever come and crash on Earth? What is the trajectory of this thing?

Charlie Sobeck: So, the spacecraft will become a piece of space junk. It’s in orbit around the Sun. Sort of like an asteroid or a meteor and such, and it’s a two-meter long piece of space junk. The solar pressure of the Sun will make it rock and tumble a little bit, and so forth. It will continue falling farther and farther behind the Earth. In another 40-50 years the Earth is going to lap the spacecraft. We’ll catch up to it from behind.

When that happens, as best we understand it right now — and we’re trying to forecast out 50 years, and we don’t have the final orbits. But as best we can tell, what’s going to happen is the Earth is going to get close enough to it — within about a million miles so it’s still farther away than the Moon — when the Earth’s gravity is going to start affecting the spacecraft. It’s going to start tugging on the spacecraft.

And the result of that is the spacecraft is going to get a gravity assist from the Earth, and it’s going to turn around, and start going faster than the Earth. So as the Earth laps it, and we start catching up from behind we’re going to give it a push, and it will start going faster. And it will start speeding up in front of us, and in 50 years after that it will catch up from behind. It will get a negative gravity assist, and the Earth will push it backwards. As best we can tell it’s just going to start ping-ponging back and forth, and back and forth.

In reality, it’s still always in orbit around the Sun, but that’s the kind of orbit it’s going to be in with the Earth affecting it. We don’t foresee that it’s ever actually going to hit the Earth or enter the atmosphere.

Host: I remember chatting with somebody and I was like, “Oh, well, in 50 years then we could go out, and capture it, and bring it, and put it in a museum.” And I remember the person I was talking to was like, “Yeah, but I would rather that money of that mission to go and grab it to be used and spent on a new thing to learn new information.” So, it was like, “The value at the end of the day isn’t the machine. It is the science.”

Charlie Sobeck: In the end it is, but the machine is part of history.

Host: It’s really cool.

Charlie Sobeck: I know that Bill Borucki, the Kepler PI [principle investigator] really thinks that somebody ought to go and get that machine. Bring the spacecraft back, and put it in the Smithsonian someday. If the answer is today the priorities would probably be against that because of the cost.

Host: Who knows what it looks like in 50 years?

Charlie Sobeck: That’s right. In 50 years who knows what the technology is going to be? Maybe it will be worth it. Maybe it won’t. It will be for another generation to ask that question. To answer that question.

Host: Even if you think of the early days of aviation when it was heavily government-funded and NASA or NACA [the National Advisory Committee for Aeronautics] before that had a role. And then eventually aviation came in to this big public/private — then the whole private sector economy. Hopefully, the way things are going 50 years from now we could have a whole space economy that doing something like that isn’t going to be a big deal.

Charlie Sobeck: It may well be a private salvage effort that brings that back to the ground 50 years from now, right?

Host: You never know.

Alison Hawkes: Charlie, you’ve been around this mission a long time, and have had a number of different roles in the mission, and very critical roles. How are you feeling at this point that we’re in this final phase here of the flight of the spacecraft?

Charlie Sobeck: Yeah, I’ve been with the mission since 2001, so I’ve been with it for 17-18 years now. I have had a lot of roles, and I’ve got a new role in this last year. Stepping down from the position of project manager. I’m feeling very, very privileged for having the opportunity of working this project. I started my career here at NASA Ames working on the Galileo spacecraft and was really thrilled at that opportunity. I said to myself, “I’m never going to be able to top that.” And now, here I am towards the end of my career, and I’ve been working on this marvelous project called Kepler. I just feel so good about having had that opportunity.

Host: So for folks who are listening, if you have any questions for Charlie, we are @NASAAmes and also @NASAKepler. We’re using #NASASiliconValley. So, you can send us your questions and comments and we’ll get them to Charlie and them on get back to you. Also, we’re a NASA podcast but we’re not the only NASA podcast. Don’t forget to check out our friends “Houston We Have a Podcast” and “Gravity Assist”. The best way to hear all the NASA content is to subscribe to our omnibus RSS feed called NASAcasts, or you can just visit the NASA App. Charlie and Alison, thanks for coming over this has been way fun!

And to all our listeners, thanks for joining us.

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