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NASA Engineer Molly Bittner Explains the Science Behind Cassini and Why It Had to Crash Into Saturn

On ‘Achievement Oriented,’ Bittner details her history with the project and provides some insight into what NASA has learned from Cassini’s 20-year journey

Saturn And Its Rings Photo by NASA/JPL-Caltech/Space Science Institute via Getty Images

After a 20-year journey throughout our known universe, on Friday the Cassini spacecraft made its grand finale and burned up in Saturn’s atmosphere. The mission gave the world new insights about Saturn’s moons, further reason to believe that life is possible in other areas of space, and some stunning photographs along the way. NASA engineer Molly Bittner joined Ben Lindbergh and Jason Concepcion on Achievement Oriented to talk about the end of the mission and some of its most amazing discoveries.

Listen to the full podcast here. This transcript has been edited and condensed.

Ben Lindbergh: Did you kill Cassini? Are you responsible? Did you send this order? Did you calculate this trajectory?

Molly Bittner: I wish I could take credit for all of that, but I can't. There's been a lot of planning. There were a bunch of different ways we could have ended the mission. We could have put the spacecraft into this really large orbit around [Saturn’s] rings such that we [wouldn’t have impacted] any protected body in like 500 years. We could escape from the Saturnian system ... and just drift off into space. And then there was this idea: Why not just plummet into Saturn itself and collect some data on the way down? ... And it's a nice way to collect some really cool science at the end. It's really just a fun engineering problem too, to plummet a spacecraft into a planet, right? Who wants to do that? I do. I can check that off the bucket list. People decided that before I even joined their project.

There are two important points to keep in mind. One is protecting bodies in the Saturnian system—so Titan and Enceladus are two moons of Saturn that could potentially harbor life. We have not found any life, but they could potentially harbor life because they have water, and we don't want the spacecraft to crash into those things in the future. … We have great models at NASA, so we could put [Cassini] in an orbit that would limit the chances of that happening, but we like to be safe at NASA, too. We want to guarantee it. … And then the other important point was that we can get some really great science [out of the crash]. Some in situ science, meaning that we can get science in the environment; we can actually pull gas into some of our instruments and collect things in the actual atmosphere rather than from afar.

Jason Concepcion: You touched on it just now, but what are some of the things that we've learned about our solar system from Cassini?

Bittner: We've learned a lot about our solar system. Mostly about Saturn, but on the way out to Saturn, we had to fly by a couple of planets. So we do that as a gravity assist [for Cassini]—we flew by Venus twice, and Earth, and Jupiter to get all the way out [to Saturn]. It took us a long time to get out there. We did science at both of those Venus flybys and at Jupiter. We originally planned to maybe not do that—to concentrate on making sure the spacecraft was healthy for its prime mission, but of course, we're building the spacecraft and operating the spacecraft for the scientists. We learned a lot about those planets, and the biggest things we've learned are actually at Saturn itself.

The first thing we did was we dropped off the probe onto Titan in 2004. You can see some really cool pictures of the surface of Titan. So for all of you playing Destiny 2 out there on Titan, Saturn's moon, we have actual pictures of the surface of that moon from Cassini, thank you very much. We've learned a lot about Titan, and we've learned a lot about Enceladus. One of my favorite things was that we discovered Enceladus isn't just a block of ice—it has a liquid water ocean underneath the surface, and ... open geysers shoot out of [the cracks in the surface], which is a really cool finding.

Concepcion: How long does it take to send an update … when you're steering the spacecraft? So you send a message, “OK, turn 45 degrees,” whatever. How long does that message take to go to Cassini’s last position around Saturn?

Bittner: Yeah, so the approximation I always use is an hour and a half. I think at the end of mission on Friday, it'll be 83 minutes, but an hour and a half is usually a good approximation for that time. And that varies depending on how far the spacecraft is from Earth, where Saturn is, and sort of where Earth is in its orbit. But an hour and a half is a good approximation. So I sit at my console any time of the day, could be the middle of the night, send a command, it takes an hour and a half to get there. And then I have to wait another hour and a half to get signal back from the spacecraft that everything went as planned. So imagine texting someone and taking three hours to get there and be like, "Are you OK?"

Lindbergh: [Laughs]

Concepcion: Do you watch the little typing balloon and sit there forever?

Lindbergh: The images are just incredible… And some of the people that you joined, they've been on [the] Cassini [project] for decades—since the very beginning, and I can't even imagine what this feels like. I mean I'm sure it is a happy feeling, it's a job well done, but at the same time this is the life's work for a lot of people.

Bittner: Yeah it is. We had a press briefing this morning, and the project manager Earl Maize spoke, and he started to get a little bit emotional, I could see it in his face. But the people that have been in this project for 20 or 30 years, it's like a part of them. You know? And as I've been asked “What are your feelings like on ending this mission” over the past year, usually my response is "Ah, I've only been on the project for four years, it's a great learning experience, I have the rest of my career ahead of me." And while all those things are true and I can carry on some of the knowledge that I've gained, this last week it's really started to hit me that it's ending. And even though I haven't been on the project for 20 years like some of these people have who are really attached, I've still come in at three o'clock in the morning to send commands up to this thing floating around Saturn—this machine. And I hear back from it in the form of data. So I'm talking to this machine at Saturn, and I will no longer be able to talk to it. And the only thing I'll have left are these memories and these pictures. And I think it started to hit me on Monday morning—we had an event at the Griffith Observatory [in Los Angeles], sort of a farewell, and I sat there thinking, “Wow, I'll never be able to talk to that spacecraft again.” And I got a little bit sad.

Lindbergh: [Laughs] Yes, there will be other spacecraft ...

Concepcion: Talk about how one becomes a flight engineer for spacecraft. … What a thing to say. What a string of words to put together there.

Bittner: What a daunting task. How can I ever do that?

As a kid, I wasn't one of those people who was like, "I really wanna work at NASA. I have to." I was one of those kids that was running around in the woods by myself being a weirdo and playing my Super Nintendo and playing with Legos and doing things that kids do, right? I really just loved to explore things, but as I started to go through school I was just really good at math. And I remember sitting on the couch with mother in high school as I started to apply for colleges, thinking about "I'm really good at math," and we pull out an article that says women are needed to be engineers. So I started looking at the list, and I actually started as a civil engineer and I only lasted one semester. Then, I switched to aerospace engineering and I loved it. It's hard. It's challenging. There's lots of math. There's lots of physics. There's lots of nights with no sleep. There's a lot of homework and study sessions and getting help after school, and there were times where I was like, "Why am I doing this? This is really hard." But looking back on it, it was all worth it because now I am where I am today. So between my junior and senior years in college ... I got an internship at NASA’s Ames [Research Center] which is in Northern California. And I did pretty well there, and I got recruited … out of college and went straight here right after I graduated.

Concepcion: So, you're talking about math and physics and all the things you need. So describe [this in] layman’s [terms]: You need to slingshot Cassini around Venus in order to get it moving toward Saturn. What is involved in that? What do you have to do?

Bittner: There is a lot of background. We all had to take classes in aerospace engineering on orbital mechanics, and that's basically what that problem is. It's an orbital mechanics problem, all a function of gravity and speed and mass of the spacecraft and mass of the bodies that you're floating around. But the great thing about NASA is that they've been doing this for a while and a lot is in models and computers. In particular, this Venus fly-by obviously happened well before I was [here], but as we're going around the Saturnian system now, in all of the orbits that Cassini has taken the last four years I've been there, we have a navigation team. And they have a bunch of tools that guide the spacecraft around Saturn, and it's all based in orbital mechanics equations. My job is basically to design maneuvers for when we fire the engines on the spacecraft, and that gets us in a certain orbit. Then navigators are sort of like Google Maps for the spacecraft, and they direct us in the certain path that we take. [Underneath] all that are the equations, but I’m not like Hidden Figures writing on a white board. Like, I am not a human computer. We have real computers nowadays, thank goodness.