SCVTV: As chief engineer for entry, descent and landing, you are in charge of doing what exactly?
Lee: I wouldn't say I'm in charge. My job really is to coordinate the team of engineers whose job it was to design the entry, descent and landing system, to test it, and actually to fly it, as you saw on Jan. 3.
SCVTV: How many people are — if not "under" you, then how many people do you work with?
Lee: Right now I coordinate a team of about 20 engineers. But at the height, when we had people from all across the country working on the system, it was a pretty difficult job. I think we had well over 150 engineers from various NASA centers (and) different companies around the country, all working toward the entry, descent and landing system.
SCVTV: Everything on your end is pretty much done at launch, isn't it?
Lee: That's the theory, that it should be done at launch. But what happens is, either fortunately or unfortunately, depending on how you look at it, when the spacecraft is en route to Mars, we're able to reprogram the computers on the spacecraft.
So when we launched, we knew that ... our jobs (were) pretty much done, but we had ideas on how we could improve the flight software for the landing system to be more robust to a wide variety of unknown conditions. So we lobbied management to let us keep working and to make these adjustments. In November, we transmitted these new computer programs up to the spacecraft.
SCVTV: Is that standard operating procedure?
Lee: It's not supposed to be standard operating procedure according to the policy that is officially put forth at (Jet Propulsion) Laboratory, but every mission does it. That's a dirty little secret in this business.
SCVTV: Almost like it's not quite done, but you launch anyway, and then you finish and send it up?
Lee: That's right.
SCVTV: When it comes to something like a dust storm getting in the way — can we predict dust storms?
Stevenson Ranch
resident Wayne Lee, chief engineer for entry, descent and landing, reacts to the signal
indicating the Spirit rover arrived in Gusev Crater on Jan. 3, 2004.
Photo/Associated Press.
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Lee: It's difficult to predict dust storms. On Earth we have a difficult time predicting things like tornadoes. But we have satellites in orbit around Mars, the Mars Global Surveyor spacecraft that was launched in 1996 and the Mars Odyssey that was launched in 2001
Both of those have instruments that monitor Mars on a daily basis. We use those as kind of like our weather satellites, our eyes and, well, not ears, but our eyes at Mars, and we have scientists who process this data every day and they report back to the entry, descent and landing team on what the predicted weather conditions are going to be at Mars, and then we react to those.
So what happened in December one day is, my parents came over for Christmas and my dad said, "Oh, I hear there's a dust storm on Mars. I read this thing in the paper." I looked at him and I said, "You're crazy. There's no dust storm on Mars."
Well, the next day I get this phone call saying, "You know, we're seeing some unusual atmospheric conditions. We need to come in and talk about this."
So ... a dust storm injects dust into the upper atmosphere on Mars, and without going into a thesis on atmospheric physics, it causes the atmosphere to warm up. When the atmosphere warms up, it gets thinner, and the thinner atmosphere is problematic because we use the air on Mars to slow us down.
What we did the last two weeks prior to landing the Spirit is, we had discussions around the clock on how we were going to compensate. Ultimately, our solution was that we asked the onboard computer to deploy the parachute at a higher altitude than we had originally planned. When we deploy the parachute at a higher altitude, it gives us more time to slow down to the surface.
SCVTV: With almost no air on Mars —
Lee: That's right, the air on Mars is extremely thin. It's less than 1 percent of what we'd have here in Santa Clarita. To find a point on Earth that has the same amount of air at Martian sea level, you'd have to be on top of a mountain 100,000 feet high...
SCVTV: Things drop like a rock.
Lee: Absolutely.
SCVTV: From the top of the atmosphere to the Martian surface takes how long?
Lee: About six minutes. In those six minutes, when we reach the top of the Martian atmosphere — it's about 80 miles above the surface — we're moving at 12,000 mph. To put that in perspective, 12,000 mph, you could go across the country in less than 15 minutes. And we have to bring it to a stop at the very end.
You say, "drop like a rock." That's literally true. In the video, where we're coming down in the parachute right before we fire the retro rockets, we were dropping at 152 mph. To put that in perspective, if you were to jump out of an airplane on Earth without a parachute, you'd hit the Earth at 120 mph. So on Mars, with a gigantic parachute, you drop faster than somebody on Earth without a parachute. Pretty scary.
SCVTV: The signals you were calling out during the descent — were those something new?
Lee: Well, it's something that was tried on Mars Pathfinder without great success. It turns out that during entry, descent and landing, it's very difficult to transmit data back to Earth. However, we can send simple electronic tones.
For example, when you turn on a radio and hear this "beeeep, this is the emergency broadcast system" — that tone is a constant tone. It contains no data, no ones and zeros, no computer bits. But we can adjust the frequency of that tone, and the spacecraft will say, "OK, well, if I'm deploying the parachute I'll choose this frequency; if something else happens I'll choose another frequency." So by decoding these frequencies, we can tell what's going on.
An analogy to that is, imagine if somebody is in another room in your house (and) they can't talk to using words. But they have a piano, and if they hit different keys on the piano, they can tell you what's happening. A piano has 88 keys; it turns out here, we have 256 different tones. So it's kind of (like having) a 256-tone piano, if you will.
SCVTV: If a signal is sent at every milestone — with the separation of the heat shield a signal goes out, with the deployment of the parachute another signal, etc. — is the idea that if something goes wrong, you'll be able to isolate the problem?
Lee: That's exactly why we have it. Because we can't joystick the spacecraft down to a safe landing. It's on autopilot from two hours out. Nothing you can do but to watch the thing go down.
In the event that the spacecraft is lost, we would have used this data to try to figure out what went wrong, and to make Opportunity a better mission. So we could have said that had something gone wrong, God forbid, on the Spirit mission ... maybe we can reprogram Opportunity to be more robust to that. But fortunately we didn't have to exercise that contingency.
SCVTV: You mentioned that you had worked on Pathfinder.
Lee: I briefly worked on Mars Pathfinder as an understudy to Rob Manning toward the very end. I spent most of my time in those years working on the Mars Global Surveyor spacecraft, where I was the chief of mission planning.
SCVTV: That's one of the satellites —
Lee: That's right. So it's kind of interesting that we actually used Mars Global Surveyor to relay our signals back to Earth on landing night. It's very satisfying — got to use both the spacecraft that I've been involved with.
SCVTV: The signals went from the lander to the Global Surveyor?
Lee: It's kind of complicated. There were several sets of signals that we had. One set of signals went from the Spirit lander directly to Earth and was picked up with our tracking antennas at Goldstone out near Barstow. Those are the signals that we listen to during entry, descent and landing, the ones that we could hear in real time.
We also had another set of signals that was being transmitted by the Spirit lander to the Mars Global Surveyor spacecraft flying overhead as the Spirit lander came in for its entry. That was via a UHF transmitter, and we actually had data on that signal. We were transmitting telemetry on how well we were doing. And then Mars Global Surveyor, in turn, an hour later, relayed that telemetry back to Earth.
And then, later on that evening, the Spirit lander, once it was on the ground, sent more data through the Odyssey orbiter back to Earth. So there are many different paths to get data back to Earth.
SCVTV: Only 2 1/2 hours after the landing, the rover sent back thumbnail images. How were those sent?
Lee: They were relayed through the Odyssey orbiter and then back down to the Earth. It was really amazing: thumbnail images of the rover from the surface of Mars. It was a surreal feeling, seeing the rover for the first time in many months.
I remember being down at the Cape (Canaveral) in May of 2003. They were buttoning up the rover and they were putting it inside the entry capsule and I thought to myself, boy, you know, I wonder if that's the last time we're going to see this thing. And then all of a sudden, there it was.
SCVTV: What do you think about landing by remote control? Would you rather be there?
Lee: Me rather be there? The answer is no, because that would involve eating TV dinners for six months inside a cramped capsule. But in terms of having a human in the loop, I think that if you ignore all the disadvantages of sending people — like, you have to build a big life-support system and you have to find a way for them to exercise and drink their Tang and all that other good stuff — once you actually get to the landing phase, it is so much better to have a human in the loop because they can react to things in real time. They can account for idiosyncrasies that the computer cannot.
The computer can only account for things that we tell it to expect. ... We would much rather have a pilot sitting in there.
SCVTV: President Bush says he wants to have a space station on the moon within a decade, and then, start sending people to Mars. What kind of focus does NASA need?
Lee: I think that NASA really needs a long-term, exciting goal that people can focus on.
I think the work we're doing with the space shuttle and building the International Space Station is extremely critical. These are baby steps that we have to take in order to learn more about how to send people to faraway places.
Don't get me wrong, it's a very important step that we're taking now. But unfortunately, the American public tends to be energized by excitement. We, as Americans, sometimes tend to have a short attention span on things that don't seem as exciting. It's not a criticism; I feel that way quite often. I think having something more exciting in terms of (enabling) people (to) say, "Oh, that's really cool," I think that's what we need to energize excitement for kids and science.
Let me tell you, my son, who is about to turn 4 in February, was watching NASA TV as this was unfolding, and he is now so excited. He took odds-and-end toys that he had in his room and started saying, "These are air bags, and here's how we bounce on the ground." And I've talked to other parents whose little kids really got into this. I've talked to parents who've said, "Now my kid would rather watch NASA TV than 'Scooby Doo.'" I think that tells you something about what a Mars program can do in terms of energizing kids to be excited about something positive.
SCVTV: It seemed telling that the president announced his space initiative after waiting for you to land the Spirit safely on Mars —
Lee: Let's get this straight. It's not me. It's really a team. I know the media likes to focus on people, but really, a lot of engineers worked on this. We had engineers from four NASA centers — Jet Propulsion Laboratory here in Southern California, the Ames Research Center in northern California, Langley Research Center in Virginia, and the Glenn Research Center in Ohio, and contractors from all across the country. It was a really big group of people, and I think that we really need to acknowledge those. There are a lot of people who put a lot of sweat into this, missed a lot of birthday parties, a lot of anniversaries, and they really need to get their share of the credit.
But with the space initiative that he put out there, I think that everybody at NASA is very excited about this, that hopefully this will go somewhere. On the other hand, I'm also a pragmatist because I know that these things don't come cheap. We have to figure out a way to pay for this. I think I'll become more excited once that becomes more clear.
SCVTV: The president made his announcement after the landing; how much do you think was riding on the success of the Mars Exploration Rover program?
Lee: I think that the timing was not a coincidence, to tell you the truth. That's my own personal opinion about that. In terms of how much the future of the space program (was riding on the success of the) Mars Exploration Rover program, that's difficult to say. I think there are some people who would say that a lot was riding on this mission. Because after the two failures that we had with the Mars 1998 missions — the Mars Climate Orbiter and Mars Polar Lander — I think there was a loss of confidence in, could NASA pull off a successful Mars program?
If Spirit had not worked, would that have doomed the Mars program? I don't think so. Would it have made things a lot more difficult, a lot more uncertain? I think the answer to that would be yes. But again, I'm only speculating as a private citizen. I don't have insight into what the policy makers are thinking.
SCVTV: What lessons were learned about the Polar Lander failure? What happened to it?
Lee: No one knows. And you asked the question, why do we send signals back during entry, descent and landing when we can't joystick it? And it's precisely for, if the vehicle fails, you know what happens and you can make the next one better.
Well, during the Mars Polar Lander era, their philosophy was that, "We're not going to transmit signals because it's going to cost us more money to do that and it doesn't help us any, as a project." As a result, they don't know what did in the Mars Polar Lander.
The best theory that they have, based on analyzing things on the ground, looking at test records and so forth, was that there was a glitch in the flight software that caused the main engines to shut down about 40 feet above the ground, so the thing then crashed after the engines were shut down. That's the best working theory, but no one's going to be able to prove that until many years from now if somebody goes and surveys the wreckage and they can see what it was.
SCVTV: Polar Lander used a different landing system, right?
Lee: That's right. There are two ways you can get on the surface of Mars. The way we did it was, we inflated air bags and we literally crashed onto the surface of Mars.
SCVTV: Like Pathfinder.
Lee: That's right. It's the same theory as Pathfinder. We had to beef things up a little bit, but quite the same theory.
The other theory, which was employed with the Viking landers in 1976, is that you can use retro rockets to gently slow the vehicle to a nice touchdown. That has its advantages and disadvantages. The advantage is, you don't come crashing to the surface. The disadvantage is that you have to carry all that rocket fuel and you have to slow down on that rocket fuel.
Also, there are rocks on the surface of Mars. Air bags protect us from the rocks, whereas a system that uses retro rockets to slow down to a safe landing has to watch out that it doesn't land on big rocks and tip over — where we are designed to fly into the rocks.
SCVTV: Is the air bag system something we can expect to see every time?
Lee: I don't know. I think that engineers at JPL, we have a big debate on which is better, retro rockets or air bags. I can tell you that the jury's still out on that question. I mean, it would seem obvious that we've landed Pathfinder successfully, we've landed Spirit with air bags, and I think we're going to have a real safe Opportunity landing with air bags. So I've got my fingers crossed, but I think we're going to be 3-for-3 with air bags.
But I still think the jury is out on which one is better.
SCVTV: Do you have a favorite?
Lee: I still think my mind is not made up on that. If it weren't for some of the inherent difficulties in the flight software, tipping over on rocks, I think that the retro rockets is slightly a better idea. It all depends on the application.
I can say for certain, though, regardless of my opinion, that our air bags are among the most robust ever designed. I told you that the rocks on Mars are extremely sharp; these air bags are made out of six layers of Kevlar. Kevlar is the same material they use to make bulletproof vests here in Los Angeles. We need six layers of Kevlar just to keep the rocks from tearing through the air bags. This is the most robust set of air bags engineers have ever built.
SCVTV: If the scientists say where they want to go and engineers have to figure out how to get them there, is there a rivalry between scientists and engineers?
Lee: You know, we have a joking rivalry. It's not really a true rivalry. The thing is, the scientists always like to play this up in he news, like, "Well, we want to go to exciting places on Mars, but the engineers tell us we have to go to somewhere flat, bland and boring because of safety." Really, my philosophy wasn't that. I tried to tell the scientists this, but they kept trying to play up this fake rivalry. I said, "Hey, listen, the viewpoint of the entry, descent and landing team is not that we need to go to somewhere flat, safe and boring."
What I tried to instill on our team members is that our job is not necessarily to land the spacecraft on Mars, (not) just to do that. Because if we just do that, and we land in a safe, boring place, but there's no science there, the mission is equally a failure as if you crash into the ground.
So we tell them, "Hey, we have to design a system that can go to some interesting places." I've told the scientists, "Listen here, you can take the system wherever you want to go. We're not going to say you can't go there. But if you're going to go somewhere dangerous, we're going to tell you what the dangers are."
SCVTV: Ultimately it's you guys, the engineers, who are in charge.
Lee: In terms of flying the vehicle there.
SCVTV: And driving it on the ground.
Lee: And driving it on the ground. But you know, I wouldn't say that the engineers are totally in charge. For example, if the engineers decide to say, "OK, we're going to take the rover out for a joy ride today and we're not going to analyze any rocks," I think that we would get a nasty phone call from Washington, D.C.
SCVTV: So it's a nice, symbiotic relationship.
Lee: It's a very good working relationship. I think that with our engineers and Dr. Steve Squyres, who is the principal investigator of the mission, this has probably been the best working relationship I've ever seen between engineers and scientists.
SCVTV: Opportunity will be coming down for its six minutes Saturday night.
Lee: That's right. I can't predict the future, because obviously there are these acts of God that we keep talking about, but my team and I — we feel really confident that we're going to have a great result.
See this interview in its entirety, with NASA footage, today at 8:30 a.m., and watch for another "Newsmaker of the Week" on Wednesday at 9:30 p.m. on SCVTV Channel 20, available to Comcast and Time Warner Cable subscribers throughout the Santa Clarita Valley.
