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On Episode 182, Chloe Sackier, entry, descent, and landing communications systems engineer at NASA’s Jet Propulsion Laboratory, illustrates the shortest and most intense phase of the Mars 2020 Perseverance rover mission. This episode was recorded on January 13, 2021.
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Gary Jordan (Host): Houston, we have a podcast. Welcome to the official podcast of the NASA Johnson Space Center, Episode 182, “Mars Perseverance Landing.” I’m Gary Jordan, and I’ll be your host today. On this podcast, we bring in the experts, scientists, engineers, astronauts, all to let you know what’s going on in the world of human spaceflight, space exploration, and today, landing a rover on Mars. On July 30th, 2020, NASA’s Mars Perseverance rover launched atop a ULA Atlas V-541 rocket from Cape Canaveral Air Force station in Florida. Since then, it’s been traveling at more than 50,000 miles per hour cruising towards Mars to make the near 300-million-mile trek through deep space for seven months and land on Jezero Crater on the Red Planet. That journey is nearing its end. On February 18th, 2021, Perseverance will make its way through the Martian atmosphere and enter into what is famously known as the seven minutes of terror. This is the phase of flight called entry, descent, and landing. And for Perseverance and the teams at the Jet Propulsion Laboratory in Pasadena, California, this may be the most critical seven minutes of the flight to the Martian surface. So, here to go into the details on entry, descent, and landing of Perseverance is Chloe Sackier, Entry, Descent, and Landing Communications Systems Engineer at the Jet Propulsion Laboratory. So, let’s get right into it. Enjoy.
Host: Chloe Sackier, thanks for coming on Houston We Have a Podcast.
Chloe Sackier: Thank you so much for having me.
Host: Hey, we’re in the home stretch here. We’re coming up on something I think you have been preparing for a very long time. How are you feeling in this moment right now, just being so close to the Perseverance landing?
Chloe Sackier: Very, very excited. A little nervous. I think the nerves, everyone is feeling as we get closer and closer. Right now, at the time of this recording, we are 30 some days away from February 18th, our big day.
Host: That’s right. And there’s a lot to do just beforehand and then what we’re going to dive into today is exactly what this — what this moment is that we’re talking about. The landing. And what’s going to go down. I want to give our listeners though a bit of background and kind of just start from the beginning to talk about what this thing is that is landing on Mars and why it’s such a big deal. Let’s just start there, Chloe, what is the Perseverance lander?
Chloe Sackier: Sure. So, the Perseverance rover is the most capable rover that NASA and JPL have ever built. And are sending to Mars. It’s tasked with some really exciting mission objectives. It’s searching for signs of ancient life, collecting rock and regolith samples for possible future sample returns. And it’s preparing for humans eventually traveling to Mars. The part that I’m most knowledgeable about is that it’s landing on Jezero Crater on the Red Planet on the 18th of February 2021. Jezero Crater is the site of an ancient river delta in a lake that used to fill this crater. And additionally, on top of all that exciting science, Perseverance also carries a smaller robotic buddy. A little helicopter named Ingenuity, which will be the very first aircraft to test controlled flight on another planet. So, lots of exciting firsts.
Host: Yeah, absolutely. Now this landing on Jezero Crater, this is — you said it’s a river delta, and that’s — it sounds very interesting. It sounds like that there’s a reason that we’re going to land in this area. What’s so special about Jezero?
Chloe Sackier: Yeah. So, Jezero Crater was identified as a really exciting site that had a lot of scientific potential. Because it is this ancient river delta location. There are all these fascinating and super rich mineral deposits that scientists think might be able to help us answer those questions about seeking signs of ancient life. And also, from an entry, descent, and landing perspective, it’s a safe enough site for us to touch the Perseverance rover down at a nice, safe, clean location.
Host: Yeah, right? You don’t want a lot of stuff in the way of that landing. And that journey, it sounds like a long ways, right? I think it’s like 300 million miles that the journey was from Earth to Mars. And it launched last year, July 30th I believe was the launch date. We kind of pushed it back but we were still within that window. Were you there? Were you there at the launch? Were you able to witness it?
Chloe Sackier: I was, yes. I was fortunate enough to travel to the launch at Cape Canaveral Air Force Station in Florida. Of course, due to the pandemic, the launch wasn’t quite the celebratory affair that we were all sort of expecting.
Host: Right, yeah.
Chloe Sackier: Several of us were able to travel safely along so we could watch in a socially distant beach setting, the launch, and listen along and support our friends and colleagues on console as they ensured a successful and safe launch.
Host: So, there’s a lot that goes into that, right? There was a lot of prep work to get Perseverance into that rocket, you know, there was, you’ve already mentioned a few of the objectives of Perseverance. So, there’s quite a number of instruments on there. But your role, Chloe, is entry, descent, and landing. So, what have you been up to throughout the whole development of this, the Perseverance rover, what goes into preparing for entry, descent, and landing on Mars?
Chloe Sackier: So, entry, descent, and landing, I think is such a fascinating phase of the mission. Because it’s really just a handful of minutes. But it takes years and years and hundreds of thousands of man hours of effort to ensure that those few minutes go safely and smoothly. My personal role on the entry, descent, and landing team is ensuring that our spacecraft is talking to us. I’m the entry, descent, and landing communication systems engineer. So, I care about making sure that the rich set of data that we generate during entry, descent, and landing, or EDL, makes it off of our spacecraft, makes it to our orbiters at Mars. Makes it through the deep space network. And then eventually back to us at JPL so we can reconstruct exactly what is happening during those exciting minutes. We’re really invested and interested in knowing exactly what goes on during those minutes. So, we want to wrangle all of the ears that we can on the Earth side and all the ears we can on Mars and have them pointed towards Mars and listening into what the spacecraft is saying to us.
Host: So, what’s it saying, Chloe? What do you care about? When you’re getting this data, what is meaningful data that’s going to help you to be successful for the EDL phase?
Chloe Sackier: Yeah. So, we’re really invested in what she’s saying in part because we want to know that she’s OK, because those seven minutes of terror, as it’s often referred to, are really quite scary. And it’s easily the most dangerous part of the mission. So, we’re invested in just hearing from Perseverance as often as we can during entry, descent, and landing. But we also want to understand what decisions she’s making as she’s progressing throughout that flight, throughout EDL. So, we care about — she sends us little bit of telemetry that explain what decision she makes autonomously, and then of course, once she touches down safely, the rover lets us know that it’s alright and that EDL went well.
Host: Very cool. So, what has Perseverance been up to so far? We talked about launch last year. Since launch, you know, it was inserted into an orbit — around the Earth. And then eventually did a trans Mars injection burn to get all the way to that planet. What’s happened since then? What has it been doing?
Chloe Sackier: Yeah, so, as you mentioned earlier, it’s a nearly 300-million-mile journey to Mars. And at this point, we’ve traveled nearly 250 million miles. But that seven-month journey is anything but quiet. Engineers at JPL like to keep a close eye on the spacecraft while she’s cruising. We do all sorts of things to make sure that she is doing OK and that we’re prepared for eventually entry, descent, and landing, and then the following surface operations. So, we keep an eye on the health, we carry out general maintenance, and monitoring, calibrate a lot of subsystems and instruments. We perform some small attitude corrections to make sure that we keep antennas pointed back towards Earth so we can talk to the spacecraft. And then we want to keep our solar panels pointed towards the Sun, so we get power. And then on top of all that, we also do these Trajectory Correction Maneuvers to tweak the flight path and make sure we’re headed to the right target. And then of course, we do a lot of instrument check-outs for devices that we specifically care about during EDL. Make sure that everything’s ready to turn on.
Host: Now I was looking at some of those course correction maneuvers, and there weren’t many on the way to Mars. But from what I saw, they really picked up in the February time frame, like right before landing. So why do you need to make — at least these more major corrections, or significant milestones, why are they later in the flight?
Chloe Sackier: Yeah, so we have five opportunities plus one back-up and one contingency maneuver to adjust our flight path. And then when those maneuvers occurred, they all sort of have different — we get something different out of each one. So, the Trajectory Correction Maneuvers that we do earlier on, like a couple of weeks after launch, those help us point the spacecraft towards the general direction of Mars and fine tune the flight path after launch. And sort of help us get rid of any injection errors that might have come from our launch. And then the TCM, the Trajectory Correction Maneuvers in the middle of cruise, like the December-ish timeframe, really helped us fine tune that even more, even more precisely. Then the maneuvers that we do in February, leading up to entry, descent, and landing, are really more targeted. And then also a backup and contingency maneuver that we don’t plan to use but are available to us if we need to at the last minute.
Host: It’s really about making sure that, that trajectory is right on target. Because you got a tiny little area that you want to hit, right? And that’s Jezero Crater. And you have 300 million miles to make the arrow fly exactly where you want to, I guess is the way to think about it.
Chloe Sackier: Yeah. That’s absolutely right. And we like to joke around a lot that the spacecraft flies itself, the EDL flies itself, but we have to — our job leading up to EDL is to make sure that she has all the information about her — the way that she’s coming into the planet. Because that really helps ensure that EDL comes off more successfully.
Host: So, this is not going to be just like a new thing for you guys. I’m sure that the Jet Propulsion Laboratory has put together simulations and programs and run through and tested what you guys believe is going to be the EDL environmental. What’s going to happen during those phases of flight. How do you construct those sims, how did they go? Just more about, I guess, practicing for the ultimate entry, descent, and landing phase of this flight.
Chloe Sackier: Yeah. So, we have definitely spent a long time preparing. And as the saying goes, “practice makes perfect.” And we have many different ways that we essential dry run or practice EDL to make sure that we understand everything about the system, and we’re prepared for anything that Mars might throw at us. So, like many other people on the EDL team, I’m also a member of the EDL testing team in our mission system test bed, which is essentially, I like to compare it to a car. Because it’s this amazingly — the test bed is an amazingly complex vehicle in its own right. It’s basically all the guts and brains of the real-life spacecraft laid out on a table. And you can send commands to it and send it through these different simulated environments. So, in this test bed, we basically get to dry run EDL over and over and over. And ensure that the flight software’s interfacing correctly with the hardware, I like to say that we’re essentially rehearsing the choreography of EDL and oftentimes in off-nominal situations. To make sure that the flight system is really robust. So, sometimes we might do a simulation with an atmosphere that is different from what our models tell us to expect. Or we’ll do a simulation with some important devices not functioning the way we would expect them to. And then we study the response of the flight system to those fault injections.
Host: So, all of this was just making sure that before you sent Perseverance into space for that ultimate landing, that you had the confidence necessary, because you’ve gone through all of these different simulated environments to make sure that Perseverance, she can stand up to the test. And that’s really the goal there was that’s why you were doing all of this repetitious, you mentioned over and over and over, all these repetitious sims.
Chloe Sackier: Yeah. And I think the interesting thing that people may not always appreciate about this phase is that there’s no way really for us to test this system in an end to end manner on the ground. Because we can’t — on the ground meaning on Earth, here, on this planet. We can’t simulate Mars in the exact same way that we’re going to be sending the spacecraft through. So, we sort of have to address — we have to test the whole system in bits and pieces. So, we can test our flight software and flight hardware. We can go through these specific bits of hardware in the system. Like parachute tests. Or like tests specific to the rover. But we can’t test it all together in an environment just like what we’ll see in February on Mars until we’re actually doing the real thing.
Host: Now, this February landing, February 18th. From what I understand, this, you know, I talked about in the beginning, you know, ultimately the launch was July 30th but there was this window. And I guess because of the way orbital mechanics works, February 18th is your day, right? There’s no — circle around and retry, like this is your moment, right?
Chloe Sackier: Yep. There’s no go around.
Host: So, it’s got to work, right? That’s why you do all the — another reason you do all of the tests is because you really only have one shot. There’s no redo, there’s no start over, this is it — is one moment, one shot.
Chloe Sackier: Yes. Yes. That’s absolutely right. And like I mentioned earlier, this thing does land itself, but we need to help it. So, we care about, in our final approach phase prior to EDL, we want to get the spacecraft ready for EDL, so we monitor all of these activities that the spacecraft is doing, these reconfigurations and mode transitions and conditioning and turning everything on. We want to make sure we get to the right place to start EDL at the right time so that we’re really on target and we make sure that our entry guidance that’s run inside the spacecraft’s computers, we’re not stressing it too much and it’s able to do the job that we’re asking it. And then we also want to tell the spacecraft what it needs to know. So, when I mentioned all those Trajectory Correction Maneuvers, and these parameter updates that we’re doing in these last few weeks, that’s what we’re doing and really preparing the spacecraft to hit that exact point, that exact location at that exact point in time.
Host: So, I want to get a picture of just what’s flying through space right now. Because we all saw the launch, but it was this rocket, you know, and there was a shell on top of it. So, we couldn’t see kind of the construction of what this things looks like flying through space. Give us a picture of what it looks like in the cruise phase right now.
Chloe Sackier: Sure. So, there’s the Perseverance and tiny little Ingenuity hanging on underneath. The rover is wrapped up in the heat shield in the descent stage in the back shell. And that, all of those critical pieces right there are essentially the main players in EDL. So, the heat shield will protect us during entry. The back shell is what we deploy our parachute from. And that’s sort of behind the rover. And then the descent stages is what flies us to our actual — it’s sort of like our rover jetpack. So, all of that is packaged up and held by the cruise stage, which is the vehicle that takes us all the way to Mars. It has all of the fuel tanks and the radio equipment and antennas and everything. And that cruise stage takes us all the way until just ten minutes before entry. And then at that point, we separate from the cruise stage.
Host: You guys have got a cool website where you can kind of see, it’s like a map of where this is. This whole setup that you’re talking about, where it is in space and how fast it’s going. And last time I looked, it was traveling at 50,000 miles per hour. Is that how fast it’s going to get 300 million miles away?
Chloe Sackier: Yes, yes, 50,000 miles per hour. Quite a speeding ticket.
Host: Yeah. [Laughter]
Chloe Sackier: Well it’s got a long ways to go, so we have no time to waste. [Laughter]
Host: Well, Chloe, let’s go into the entry, descent, and landing phase. This is the seven minutes of terror as you called it. What — I’m curious to hear why it is called that. But let’s go through step by step this, you know, what’s going to happen as it gets closer to Mars and gets into this phase?
Chloe Sackier: Sure. So, as I mentioned just before we separate from our cruise stage, that vehicle that safely escorted us all the way to Mars, about ten minutes before entry, and then at entry, we hit the atmosphere of Mars. We use the atmosphere of Mars to start slowing down. It’s thinner than the atmosphere of Earth. So, we can’t slow down completely using it. But there’s enough atmosphere there that it does help us bleed off a little bit of velocity. And during that time, we’re protected by that heat shield. About 80 seconds after entry, we hit a period called peak heating. At that point, the temperature on the outside of the heat shield is around 2,300 degrees Fahrenheit, or 1,300 degrees Celsius. Really, really hot. And during that time, while we’re doing entry, we’re steering towards our target using this principle called guided entry, that was essentially adapted from the Apollo era. And this approach helps us stay on target while we might be hitting pockets of air that would maybe bump us around a little bit. While we’re on that heat shield, we slow down to just under 1,000 miles per hour. And then at that point, we deploy the largest supersonic planetary parachute that has ever been used. It’s about 70 and a half feet or 21 and a half meters in diameter. And we deploy it at about mock 1.75. Also, really, really fast. At that point, we’re about seven miles high in altitude and going 940 miles per hour. And then shortly after that, we jettison our heat shield at about mock 0.7. This uncovers the radar that we use to start searching for the ground. And this is where the Terrain Relative Navigation concept takes the stage. And starts searching for the ground. We use this concept, TRN, to take pictures of where we are and match those pictures up to an onboard map. So it’s sort of like an — like if you’re driving in your car and you use a GPS instead of just looking out the window, you see pictures of where you are and you match those up to your map to help you figure out and localize yourself. So then around this point, we drop out, our descent stage, that rover jetpack, drops out of the back shell. Because we don’t want to recontact that back shell and parachute. We execute a divert maneuver to quickly get out of the way. At this point, we’re just under 7000 feet above the surface. And then while we’re at that descent stage, that takes us down to a velocity of I think .75 meters per second. So, way, way slower than we’ve been traveling before. And when we’re traveling this fast, we’re about 20 meters off the ground. And then at this point, we execute the sky crane maneuver. So, this is what was originally debuted on the Curiosity rover. Separates the rover from the descent stage, from that rocket jetpack, and touches Perseverance down safely and slowly on her wheels. And then as soon as we have confirmation of — as soon as the rover has confirmed that she’s touched down, we separate the descent stage connection and fly the descent stage away to a safe distance. And that’s all there is to it. We’re on Mars.
Host: All there is to it. But when you think about it, all of that, everything you just described happens in seven minutes. And the challenge there is, I think, one of the challenges at least, there’s a lot of challenges, you just went over a lot of them. But one of them is, like you said, this is all happening by itself. Because Mars is so far away that by the time it actually communicates what’s happening to you on Earth, at the Jet Propulsion Laboratory, real time on Mars, it has already happened because of the communication delay, right?
Chloe Sackier: Yes, that’s true. Our one-way light time at this point in the mission is over 11 minutes. So, it takes 11 minutes for information to travel from Mars back to us at Earth. And because of that massive distance and massive delay, we can’t joystick the rover through landing. We can’t fly it ourselves. It has to happen completely autonomously.
Host: That’s incredible. Chloe, I want to go through and kind of ask questions about every phase of this flight from beginning to end. We did actually have a subtle dropout. You were talking about, you talked about slowing down and entering into the atmosphere. We kind of missed that part of it. But I think the question about that phase was how do we get down from 50,000 miles an hour to the 10,000 miles an hour? Is that what you said? Was it 10,000 miles an hour when you actually hit the atmosphere?
Chloe Sackier: Yeah. So, it’s a little complicated, orbital mechanics wise. But basically, in cruise, we are traveling 50,000 miles per hour relative to the Sun. But then once we actually hit the atmosphere for entry, at that point, we’re going about 12,000 miles per hour, a little over 12,000 miles per hour.
Host: OK. So, it’s not really slowing down, it’s just kind of relative to how fast Mars is traveling or something like that?
Chloe Sackier: Yeah, that’s true. The 50,000 is relative to the position of the Sun and then when we hit atmosphere, that 12,000 number, that’s relative to Mars.
Host: Got it.
Chloe Sackier: But we do use the atmosphere to slow down significantly before we deploy our heat shield. We bleed off a lot of velocity.
Host: Right, it goes from 10,000 to 1,000 miles an hour, right?
Chloe Sackier: We deploy our parachute — yeah. Just about around 1,000 miles an hour. A little under.
Host: Now — I got it. You were talking about some, you know, some of the sims you were running. And these parachutes, you’re deploying them at supersonic speeds, right? I mean I feel like if you were to deploy anything at that speed it would just kind of snap. So how does that work, you know? How does a supersonic — how are you able to deploy a supersonic parachute that’s able to, you know, perform that job and not snap?
Chloe Sackier: Carefully. Yeah, no, that’s true. It’s a blistering high speed. And to have a soft goods material that’s capable of withstanding that, we basically built a really, really strong parachute. And test it in all of these different stressing conditions. So, we — when I mentioned earlier about testing EDL in bits and pieces, the parachute is obviously this critical component, this sort of quarterback of the team that our safe EDL is dependent and reliant on. So, we test our parachute in big wind tunnels. We do sounding rocket tests to simulate what that supersonic deployment might look like and feel like to the parachute. And then all sorts of lower level tests as well.
Host: So, what’s challenging, you talked about the heat shield heating up to I think it was 1300 degrees. You have supersonic parachutes that are deploying here. What are the challenges here with just Mars being the planet that it is? It’s got an atmosphere, so you have to deal with that atmosphere, so you have to have a heat shield. But you don’t have enough, you know, a thick enough atmosphere where parachutes aren’t going to do the whole, you know, as much as they do on Earth, for any missions that we have. We deploy parachutes and they land safely, either on land and water. What are some of the challenges here with just dealing with Mars?
Chloe Sackier: Yeah, so as you mentioned, there’s the common expression is that there’s not fear to really use it enough to ever break to the point where we’ve, you know, have slowed down enough. But there’s just enough atmosphere that you have to pay attention to it and take it into consideration. There’s all of these, you know, it’s always fascinating to learn about Mars’ weather and to even think about what weather looks like on another planet. But Mars is a planet, just like our own. It has weather, it has winds, it has dust storms, all of these components that we have to study and understand a little bit about so we can plan how they might impact us and affect us. There’s the parachute, we already discussed the excitement of the parachute. When we get to the stage where we have jettisoned our heat shield and we’re using our radar to search for the ground, that’s a really fascinating point in the mission as well because we — we’re looking to land in Jezero Crater, which is this scientifically exciting location. But also, from an entry, descent, and landing perspective, we need a landing site that is safe enough to touch down. So, the things that we’re looking for is an altitude of the landing site that’s not too high, it gives us enough time to stop. And not too dangerous to land on. So, not completely full of sand dunes or rocks or slopes or really rough terrain. We want it to be radar reflective to a certain extent. And that the atmospheric conditions, like I mentioned, are OK. Not too dusty, not too windy. So, Jezero Crater’s really this interesting spot. Because it’s, from a terrain perspective, most exciting that we’ve ever attempted a landing on for EDL. But we want to get there for the science. And our new — new technological functionality of TRN allows us to travel to that little bit more rocky, little bit more sandy crater that we care about visiting.
Host: Well let’s go into that. Let’s go into Terrain Relative Navigation. This is a critical technology that was put on Perseverance. What is this technology?
Chloe Sackier: Yes. So, Terrain Relative Navigation, quite simply put, it gives us eyes. So instead of just taking pictures, on the way down, we’re taking those pictures and matching them up to a map that is onboard the spacecraft, like I mentioned earlier, just like you or I could look out the window while we’re driving our car, and match up landmarks or things that we’re seeing to a map. So TRN helps Perseverance figure out where it is and once the spacecraft knows where it is, it can use its engines to fly to a safe landing spot that it picks and decides upon. So, we, the humans behind the scenes, have done the work over the last few years to map out and really understand every little nook and cranny of this landing site. And identify, using some fascinating algorithms and sometimes just our eyes, the spots that we think are safe to land in and the spots that we don’t want Perseverance to choose. And then we give all of that information to the spacecraft in the form of that onboard map, and then while she’s flying EDL, she takes those pictures, checks those pictures, and where she thinks she is against at onboard map and says, “OK, this is where I want to fly, this is safe, I’m going to turn on my engines and lean over and fly that way.”
Host: So those engines, are they, are they in the back shell and they’re just kind of little pulses to guide it the right way?
Chloe Sackier: We have a bunch of different engines in different places. There are — there’s the thrusters that we use to sort of reorient ourselves as we’re coming in for entry. But the descent stage is what flies us to the safe landing spot that we pick.
Host: Now what’s interesting, this is what I read, that Terrain Relative Navigation jumps up the chance of successful landing exactly where you want it from 80% or 85% to about 99%. So, that’s how good this technology is at guiding down based on all the sims that you’ve done and used it with?
Chloe Sackier: Yeah. It’s really incredible. As I mentioned earlier, what we’re looking for in a safe landing site for EDL, slopes, craters, rocks, none of those things we really like. Those all really equate to landing death for EDL. But they’re so interesting. They’re massive science targets for the scientists. And at the end of the day, that’s why we’re doing this mission. We want to enable some really, really exciting science. And so, Curiosity and all the previous Mars missions had to ensure that anywhere that we could possibly touchdown was basically a parking lot. No sand dunes, nothing like that. But we don’t have to do that with Perseverance, mostly in part due to Terrain Relative Navigation. There can be and will be rocks and slopes and craters in Jezero, Jezero Crater. Actually, the middle of the landing eclipse is a cliff base that’s like 60 to 80 meters tall right on the edge of the river delta. So, it’s — I feel like if you were standing in the middle of Jezero Crater and looking around, it would be quite, quite beautiful but it’s exciting and a little more risky than has previously been attempted. But all of that is enabled because of the TRN technology.
Host: So, Chloe, I believe like me, and I’m sure thousands if not millions of others, are going to be glued to the TV trying to watch everything go down. What are we going to see? Are we going to get — are we going to be able to see some of the things that Perseverance is seeing? Like the Terrain Relative Navigation providing a video feed. Are we going to be looking at the control room? What are we going to see?
Chloe Sackier: So, yes, so me and my whole team will be at JPL monitoring telemetry and anxiously awaiting with the rest of the world hearing confirmation that Perseverance has touched down safely. And we’ll be doing our best to share everything that she’s telling us with the world in real time as that’s happening. We have multiple different ways of relaying the rich dataset that the spacecraft generates during EDL back to us on Earth during that timeframe. We have tones of the X band that are sent directly to Earth. I like to say it’s sort of like the spacecraft singing us a little song as she flies EDL. So, these tones, each tone indicates a different critical event has happened. So, we might get a tone for the deployment of the parachute. Or a tone indicating that we just completed a bank reversal. These tones just sort of provide markers of events that the spacecraft has checked off. We also get a tone, a pretty persistent tone all the way throughout EDL that we call the heartbeat tone. And that’s basically just the spacecraft giving us a thumbs up from Mars and saying like “yep, I’m still alive, I’m still trucking.” So, we love to see that intermittently and make sure that everything is OK. We also receive — the spacecraft communicates UHF data to our orbiters, to the Mars Reconnaissance Orbiters, and the [Mars Atmosphere and Volatile Evolution Mission] MAVEN spacecraft during EDL. And those orbiters are at Mars. And those orbiters relay that information to the deep space network, which has stations in California and Spain and Australia. So, all over the world. And those stations relay that data back to us at JPL. And the dataset we get from the orbiters is a little bit richer than what the tones indicate. So, it tells us a bit more information about the decisions that the spacecraft is making and the environment that it’s experiencing throughout EDL.
Host: And so, you will be in that control room during the EDL phase. And you’ve mentioned it before but make sure — correct me if I’m summarizing this incorrectly, is your job is to make sure all of these connections, this pathway of how Perseverance is communicating to you guys in that control room, that those pathways are all functioning normally and properly and you’re getting all the data you need?
Chloe Sackier: Yes. That’s exactly correct. I think the most fascinating thing about the communications and the telemetry side of the world is just like it is in EDL, it takes so much effort, so much orchestration and conducting of so many people and so many teams for such a small number of minutes to go off smoothly and successfully. So, everything has to go right. Nothing can go wrong for one bit of data to make it — the spacecraft computer out of the spacecraft antenna, be received by the Mars orbiters, make it from the orbiters back to the dishes of the deep space network, and then all the way back to our computer monitors at JPL. So, there’s not a lot of room for errors. It’s very exciting.
Host: Well, you know, I think you’ve kind of mentioned this throughout our conversation today. But you’ve referred to Perseverance as she. And I think — you know, correct me if I’m wrong, but it seems like, you know, because of that pressure, because of all of the — all of your work going towards this one moment, you all in your own kind of special way have developed a connection to the rover. And in a way of kind of personifying it and making it into some kind — instead of just a piece of hardware, something that you as a team can connect with and really engage with throughout this critical moment.
Chloe Sackier: Yeah. I think that’s fair. There’s definitely a significant amount of personification going on. But I’ve heard teammates refer to this spacecraft as like their baby or their child. Some people think of it as an old friend. Or maybe a dog. But everyone relates to it in a different way. But it goes without saying that it is incredibly meaningful to every scientist and engineer who’s gotten the amazing opportunity to work on this project. So, it’s, you know, it manifests itself in different ways.
Host: So, you came to JPL after Curiosity, that’s correct?
Chloe Sackier: That’s correct, yes. Actually, I remember watching the Curiosity, the entry, descent, and landing in my bedroom, in high school. And thinking like “wow, those people are really cool. I wonder how I figure out how to do what they’re doing.”
Host: I watched it too. I was watching it during an internship, and I watched it live. And I’ll remember, you know, one of the highlights of the whole thing was, you know, you were just watching, you were just watching the control room and all these faces just glued to their monitors. And of course, the big moment that I think everybody that watched that live remembers was the celebration. Jumping up and down, the high fives. That’s something that you get to be a part of now.
Chloe Sackier: It will of course, look a little different than the jubilant celebrations of the past, and what the celebrations in mission control looked like for Curiosity due to the pandemic. So, you know, our first and foremost priority is to keep each other safe. So, it’s heartbreaking, but no hugs this time. We’ll have to make do with elbow bumps. But that certainly, doesn’t diminish the incredible feeling of successfully landing something on Mars. And the pure joy and disbelief I think we’ll all feel accompanying that.
Host: Well you did — I’m sure you did get to learn a lot from the folks who have been a part of that moment before, during Curiosity, right? I mean, the landing looks very, very familiar to Curiosity. So, you have a lot of folks who worked hard on that. And that you learned from. And I’m sure, I’m sure you got to learn from, you know, what to do differently this time around, what to make sure we do consistently that was successful on Curiosity. I’m sure you got to hear a lot of those stories.
Chloe Sackier: Oh, yes, absolutely. I think that’s easily the best part of the job is the people that we get to work with. And some of these people have been doing it not just since Curiosity, but decades ago. So, they’ve been involved with so many successful missions. Their stories are unparalleled. Their wisdom is infinite. Knows no bounds. So, there’s a lot of important technical knowledge that gets passed along throughout the generations. But also, just like ways of doing things that you know, you can really only learn firsthand.
Host: Yeah. So, Chloe, what’s — we’re recording this, like you said, you know, just about a month ahead of the actual scheduled landing. So, what’s on your agenda from now until landing day on the 18th?
Chloe Sackier: Right now, as we are recording, we are in the middle of our final operational readiness test, which we also call our EDL dress rehearsal. Up until this point, we’ve been, as we talked about, simulating and practicing on the spacecraft all sorts of different situations and scenarios. But now, we’re at the point in the mission where we have to train ourselves. We have to train the team to make sure that we are ready to deal with any sort of situation we might encounter. So, we’re stepping through all the motions of those final few days before EDL. So, getting the spacecraft ready for EDL, getting to the right place to start at the right time. Telling the spacecraft what it needs to know. So that’s that process of Trajectory Correction Maneuvers and parameter dates. And that cyclical sort of undertaking. And then of course, in a few weeks, we won’t be practicing anymore, we’ll be doing that process for real.
Host: There you go. Now you’re going to have your celebratory, you know, elbow bumps as you mentioned. Socially distant celebration. I’m curious, what’s your role after — you know, you’ve been working up to this moment, right? Entry, descent, and landing. What’s your role after EDL?
Chloe Sackier: We go through a process where we try and make sure we understood exactly everything that happened. And piece together the whole story. This helps us prepare and understand things better for future missions and really understand how our technology works. So, we’ll be piecing together all those little bits of telemetry and really trying to make sure we flush out every single detail. And then of course, the science will kick off on Perseverance. And the rover will start firing up all those instruments and turning out the mission to search for signs of past life.
Host: A really important thing. Now, Chloe, this is, it’s been a whole lot of work for you. And I know, I can sense your excitement through for getting ready for this moment. You know, kind of, let us in on some of the culture. Some of the, you know, not necessarily secrets, but just the behind the scenes of just working at JPL, you know, working with the teams that are working on this rover. And just the culture that you have there to put together a mission like this.
Chloe Sackier: Yeah. I think it’s an amazing culture. There’s an expression at JPL that we “Dare mighty things.” And I think to accompany that sort of mission philosophy, you have to have a tight knit culture. And a group of people that are really supportive, but also really push each other to do our best and put forth our best ideas. It’s a little cliché to say, but I truly feel like the EDL team itself is so much more than just a team. It’s a family in every sense of the word. It’s a group of very interesting, very diverse, very wonderfully weird people. But I feel like we all complement each other so well. Of course, in the pre-pandemic days, we used to get up to all sorts of hijinks. We had goat yoga and axe throwing and laser tag. I remember one holiday season, we all acquired NERF guns for some reason and then there was a solid two or three weeks where we were just chasing each other in circles around our floor, our cubicle area. And being very productive. [Laughter] But it’s a very tight-knit team. It’s been the honor of a lifetime to work with them and learn from these incredibly accomplished people.
Host: Yeah. I think you need that, right? Because you’re working so hard on something so complicated. And to have — and to have that kind of culture that brings you all together to make sure you’re getting the job done I think is a wonderful thing.
Chloe Sackier: Exactly. You have so many late nights in the test bed. It really helps to actually like the people that you’re working with. It makes a difference.
Host: Well, Chloe, from here at the Johnson Space Center, we’re going to be watching intently for the landing itself. We’ll be rooting for you and of course for Perseverance and all the great science that it’s going to do after this critical seven minutes of terror, the entry, descent, and landing phase. Looking forward to everything we’re going to be learning when that rover actually starts doing its mission. Chloe Sackier, thank you so much for coming on Houston We Have a Podcast. And describing in detail all the wonderful things that we get to look forward to. I know I feel prepped and ready and know what to expect for when I’m watching the real deal live on the 18th. So, best of luck to you and of course to your team.
Chloe Sackier: Thank you so much. It’s been really fun hanging out.
Host: Hey, thanks for sticking around. I really hope you enjoyed this conversation with Chloe Sackier on what’s going to happen during the entry, descent, and landing phase of Perseverance’s journey to the Martian surface. Now, we are doing this podcast specifically on EDL for Perseverance. In fact, you can check out another one of our episodes, 174, we — that one’s called “Sticking the Landing on Mars.” We talked with some experts about what happens when you add the human element to landing on Mars. But we are just one episode of many through all of the different NASA podcasts we have across the agency. Check out some of their episodes as well. We’ve got “Curious Universe,” we got “Gravity Assist,” and they’re going to be talking about different elements of the — of Perseverance, some of the science, and some of the sounds, some interesting parts of the mission. This is EDL. So, make sure you check out some of those podcasts. You can go to NASA.gov/podcasts to check out any of those episodes. If you’re curious about the Perseverance rover itself or want to learn more about Mars or its objectives, there’s a good website for that. Mars.NASA.gov. And of course, click on the Perseverance rover. Now, if you want to watch the landing live, we talked about watching it live, we’re putting this out ahead so that we can tell you exactly when it’s going to land it is landing 3:30pm Eastern time, 12:30pm Pacific. And the broadcast is going to start 30 minutes before landing, 3pm Eastern, and noon Pacific. So, make sure you tune in right on time and watch the whole thing, especially those seven minutes of terror. You can follow us, Houston We Have a Podcast, on social media. We’re on Facebook, Twitter, and Instagram. Go to the NASA Johnson Space Center pages of any one of those. And if you want to talk to us, use the hashtag #AskNASA on your favorite platform to submit an idea for the show. And make sure to mention it’s for us at Houston We Have a Podcast. Now this episode was recorded on January 13th, 2021. Thanks to Alex Perryman, Pat Ryan, Norah Moran, Belinda Pulido, Jennifer Hernandez, and Andrew Good. Thanks again to Chloe Sackier for taking the time to come on the show. Even in the middle of some of her preparations for this — for this mission. Thank you so much for coming on. Give us a rating and some feedback on whatever platform you are listening to us on and tell us what you think of the show. We’ll be back next week.