A couple of weeks prior to scheduled launch, STS-93 Mission Specialist
Steven A. Hawley
took some time out from training to answer questions about the mission.
Click on the image to hear Steven's greeting.
Steve, you've been an astronaut for over twenty years. Why did you want to become an astronaut in the first place?
When I was young, I was interested in astronomy and the sky, but in those days a kid couldn't really plan to grow up and be an astronaut. The astronauts back then were all military test pilots, and I wanted to be a scientist. I dreamed that one day the world would have telescopes in space. To me, it made sense to get them above the atmosphere and away from the bright lights. I thought that I could be one of the astronomers who manned those observatories. I studied astronomy and that's what I wanted to do. It turned out that telescopes were sent into space, but I hadn't foreseen the development of digital technology that allows us to send all the data to the ground. On-site astronomers weren't really needed. I was getting my Ph.D. just about the time NASA began to look for space shuttle astronauts. The astronauts in the new class were not the professional test pilots, but more the scientists and engineers, such as I had grown up to be. One day I was walking down the hall at the Graduate Department looking at the bulletin board for jobs, and there was this announcement that had "NASA" on the top of it. I looked at it and it said "Astronauts," and I went, "Wow, that's really something." I realized that I met the qualifications they were soliciting, but there were probably ten million other people who did too. I did end up applying at that time, although I had no expectation of being picked. I knew that I didn't want to go through the rest of my life wondering, as we launched space shuttles and built space stations, if I could have had that job if I'd applied. They made a mistake and picked me, and here I am, twenty-one years later.
You said you were interested in astronomy as a boy. Do you know what sparked your interest in science?
Both of my grandparents were teachers. One was a physics teacher, and I remember when I would visit, I would read his textbooks. I really got interested in physics and astronomy. I grew up in Kansas, away from city lights, so the sky was dark at night and you could see stars. I think if I had been a kid in Houston, I never would've become an astronomer because I wouldn't have even known there were stars up there. There was something so fascinating about the sky, and about how astronomers did their business. They weren't able to do experiments like other scientists. They had to be clever and look at what nature revealed to see if they could figure out what was going on. Something about that process intrigued me. The fact that the things that they had deduced were so strange and esoteric. The possibility that there was life among those clusters of stars was intriguing. I was always a science fiction fan and I read lots of books about space flight and exploring other worlds. I guess all of that came together.
Were any of your school teachers key to your development?
There was my physics professor in 11th grade. I remember him very well. One thing that he did, which I didn't like much at the time, was force me to work at my capacity. I realize now how much that taught me. I was interested in science, and I generally got good grades in school. He recognized somehow that I was able to get by in his class without having to work a hundred percent, so at the beginning of the second semester, he told me that I was either going to get an A or an F at the end of the year. If I worked a hundred percent, I would get an A. If he thought I was slacking-off, I would get an F. I remember thinking how unfair I thought it was, but he didn't much care what I thought about it. He motivated me to work very hard in that class. I learned later that it's not important to meet other people's expectations, but to meet your own and do the best job you can do. When working with a crew, that's extremely important because the only person who knows if you're able to do the job is you. You're the only one who truly knows if you're adequately prepared, if you've learned enough, if you've studied enough, if your understanding is good enough, and if your operations skill is good enough. Nobody can make those judgments as well as you can. That lesson that he taught me back in 11th grade has been very important, and I've told him so since. I see him every once in a while. He's still teaching back in Kansas, and I've told his current students that same story, much to their dismay, I'm sure.
You were part of the crew that deployed the Hubble Space Telescope more than nine years ago. Any sense of deja vu about getting ready to go deploy another major astronomical facility?
This mission is very similar to others that I've flown. The deployment method is much different than the one we used when deploying Hubble. We used the robot arm that time. This time we'll be using a system of springs and a tilt table, and then Chandra will launch on a booster rocket. A lot of the other techniques are the same, like interaction with the ground, time-critical operations, thinking about how you can use the shuttle's capabilities to maximize the probability of mission success. Deploying on Day 1 is a bit unusual. Usually the activity doesn't pick up until Days 2, 3, and 4. I've been exposed to a lot throughout my career, so I feel very comfortable with this mission even though it's a little bit different from most.
Your Commander on this mission had been the focus of a great deal of public interest because she's the first woman ever to command a space shuttle mission. How has Eileen Collins been doing in dealing with all that attention, and yet still keep you and your crewmates on course to fly this mission?
I think she's done well. She's
made it clear to us all along that our focus needs to be on the mission
and preparing to do the mission, and that's where her focus has been.
Of course, ever since we were assigned back in March of last year, we
knew that there would be a lot of attention on her and this mission,
but the whole crew has maintained focus on the mission. Every flight
has its own distractions for one reason or another, and they always
tend to become a little more intense the closer you get to launch. This
flight will be no exception. She's handled it very well.
I've worked with women all through my career. I was picked to be an astronaut in 1978 with the class that included the first six women astronauts, so there have been women astronauts since I've been here. I was also on the selection board in 1990 when we picked Eileen to be an Astronaut Candidate. At that time, we knew that she would potentially be the first woman to command a space shuttle. All of us that were part of that decision back in 1990 take pleasure in seeing it happen. As Eileen said herself, I think another opportunity is clearly available to young girls growing up. The fact that she has achieved her dream of flying in space as a mission Commander will help boys and girls alike realize that their dreams can come true too. I know that she sends out an important message, and I agree with it. It is very important to realize that dreams can come true.
The target launch date for your mission has slipped a few times due to problems with the primary payload hardware. Have you been able to put the "extra" training time to good use?
Yes. In my experience, those kinds of slips are not unusual. We've actually been fortunate in the last several years to have had a lot of manifest stability. Hubble was delayed for a variety of reasons. It gives the crew and the rest of the ops team a chance to review procedures, techniques, and rules, and to talk about technical things that perhaps we didn't have time to adequately address before. In the last several months, as we've been continuing our training with the crew and the Mission Control folks, we've had a chance to identify some new issues that people hadn't thought of before. These are not things that are likely to happen, but we still want to be prepared. We really don't expect any of these situations to develop, but your understanding of how the satellite works, your understanding of the dynamics of the deployment process, your understanding of what capabilities you might really have on board in the event of some off-nominal situations, gets refined. That gives the team much more confidence going into the mission.
The most recent delay in the target launch for this mission is related to the failure of an Inertial Upper Stage rocket during an unrelated satellite deployment in April. Can you explain what the cause of the problem on that April satellite deployment was? Why are you confident that the IUS on your mission is going to perform properly?
What happened in April was the failure of the two stages of the IUS booster to separate. When it works properly, the first stage fires and then separates and falls away, allowing the second stage to fire. It was reported that in the April Air Force mission, the stages did not separate properly. Therefore, the second stage wasn't able to fire properly and the satellite did not reach its intended orbit. They have inspected our IUS and have confidence that ours is not likely to have that problem. The investigation is still ongoing, and as we proceed to a launch date of the 20th, there will be several other opportunities to review the status, not only of the IUS, but also the Chandra and the orbiter. We're hopeful and confident that the investigation and the subsequent review of all of the facts and circumstances will say we're good to go. Chandra is a one-and-a-half-billion dollar satellite and has been in development for over twenty years. It's critical that it ends up where it's intended to be. If the right thing is not to launch on July 20th, then we won't. Hopefully everything will come together and we will be able to send Chandra and the IUS up with the confidence that they will do exactly what they're supposed to do.
Your primary payload, the Chandra X-ray Observatory, is described as "a highly sensitive x-ray telescope, which offers scientists a greater understanding of the forces that created the universe and continue to shape it." You're the astronomer. What exactly is an x-ray telescope?
I should make the point that astronomers are a little bit unique, in the sense that we're not able to do experiments in the conventional sense. Other scientists are allowed to create circumstances in the laboratory and then observe an outcome, and that's how they understand. Astronomers can only observe the circumstances that nature conspires to create. Based on those observations, we try to understand important questions like: How old is the universe? Is it expanding? Is it collapsing? Are there other planets? What's the ultimate fate of our galaxy? How do stars live and die? We do that by looking at clues very much like you would look at pieces of a picture puzzle in order to deduce the design. Unfortunately, nature provides its clues across the whole spectrum of wavelengths. X-rays are one of the forms of light where those clues are available, but the technology has not really been there to allow astronomers to get a good look at them. It's by combining the clues we see in x-rays with the clues we see in visible light, infrared light, ultraviolet light, radio waves, and microwaves, that allow us to see enough to figure out what's really going on. X-ray astronomy itself is a product of the Space Age. Since x-rays don't get through the Earth's atmosphere, it's not possible to build an x-ray telescope on the ground. We wouldn't be able to see anything because the atmosphere absorbs them. Until recently, it hasn't been possible to have an x-ray telescope to put in space. Chandra will be the first major facility that allows us to look at what we haven't seen before. Hopefully, combining that information with information provided by Hubble and the Compton Gamma Ray Observatory, we will be able to address some of these questions.
Chandra will be observing the x-ray portion of the electromagnetic spectrum. What can we learn from that information?
X-rays are produced in regions of the universe where there are intense magnetic fields, strong gravity, or extremely high temperatures. With the information that Chandra gathers, we'll be able to learn more about those regions. It's a new way of looking at objects we've seen before, and discovering some of the more esoteric objects we didn't know about. For example, if you look at a cluster of galaxies with something like Hubble, it is possible to see many different galaxies. If you're to look at it with something like Chandra, we expect that you'll see a big cloud of hot gas. That's another component of this cluster of galaxies that's invisible. There could be a very large amount of matter in that cloud that we wouldn't know about if we had only Hubble images to look at. In order to understand the nature of the universe and its evolution, it is important to know how much matter there is in the universe. We've found that a lot of it hadn't been visible to us until x-rays. There's probably a lot more that's still not visible to us. It's the ability to see these things that the existing facilities can't see that will allow us to put it all together and come up with the big answer.
Chandra is designed to gather and record x-ray information that can't come down to the ground. How is it going to get that data to the researchers who are here, and keep itself functioning over the course of it's life in orbit?
It's a very interesting design. People have seen x-rays used in medical applications, as security measures, and other things. Imagine trying to reflect x-rays, as a telescope would, when x-rays tend to want to penetrate. Normally, light would enter the telescope in one end, hit a mirror at a 90-degree [angle], and bounce back. X-rays would just penetrate this telescope. The engineers and scientists that made Chandra developed four cylindrical-looking mirrors that are nested on the telescope. When the x-rays enter, they hit the mirrors a very glancing blow, so rather than penetrating the mirrors, they actually do reflect. By nesting these mirrors just so, they can cause the x-rays that come into the telescope to be focused on detectors. Detecting x-rays is not as difficult as focusing x-rays. By having a large telescope with these four cylindrical-type mirrors, we were actually able to develop a telescope that has resolution almost as good as our best optical telescopes on the ground. That's a remarkable step forward. When I was a kid, I had a little 4 ½'' reflector in my backyard which I used. As I grew up and started to do astronomy professionally, I got to use the 200" telescope on Mount Palomar. That was a tremendous advance compared to what I'd had in my backyard. The x-ray telescopes we had before Chandra are like that little 4 ½'' telescope, and Chandra is like that 200". That's the kind of advance that x-ray astronomers are seeing. The telescope is run from a control center on the ground with a team of scientists and engineers. The scientists are responsible for the scientific program, and the engineers are responsible for the Chandra systems. Chandra will record the data on board, send it to the ground, and scientists will reduce the data. The operations over the lifetime of the telescope will be very similar to our experience with Hubble.
You mentioned that there are other x-ray telescopes already in orbit. They were all launched on expendable vehicles. Why is this x-ray telescope being brought to orbit on a space shuttle?
There are some advantages. The shuttle is one of the very few launch systems capable of carrying that heavy telescope into orbit. Having the crew present also gives us some more options. Chandra will go through a day-long checkout before we commit it to launch, and we expect all that will go well. If it doesn't go well for some reason, then the crew is there to go out and make repairs, or bring it back to do repairs if needed. Unlike Hubble, Chandra goes into an orbit that is no longer reachable by the space shuttle, so we don't have the option in subsequent years to go back and do upgrades or repairs to it. Its orbit will be a third of the way to the moon. In that kind orbit, it has the ability point at the same object continuously for up to two days. Hubble can't do that because the Earth gets in the way every orbit. To get long exposures, it has to take them a piece at a time and then add them all up. Chandra has the ability to do prolonged observations of a single source if the scientists choose to do that. Because it's not serviceable, we want to be confident that it's going to work properly.
Chandra deployment is scheduled during the first day of flight. What will you be doing as a group on board Columbia that first day and as you deploy Chandra?
Flight Day 1 is going to be very busy. The first hour-and-a-half or so will be very much like any shuttle flight. Once we get safely into orbit, we reconfigure the computers and open the payload bay doors. After that, the focus turns to preparing Chandra and the IUS for the deployment scheduled about seven-and-a-half hours after launch. As we are doing that, we also have to be getting Columbia ready for the five-day flight. Cady and Michel will be spending their time on the Chandra and IUS in conjunction with the people in Sunnyvale, Cambridge, and Houston Mission Control. My job will be to help Jeff get the orbiter configured for the five days in orbit. We'll be doing a lot of the routine setup activities, but at the same time, we will be working on an important operation. As we get closer to the time of deployment, then all five of us will focus our attention on Chandra. We all look over each other's shoulders and make sure everything is going like it should. First we have to power up Chandra. After that is done, the control center at Cambridge will start to load the systems and do some IUS checks to make sure that everything's working properly. At about five-and-a-half hours into the flight, we'll begin to elevate the stack. The Chandra is attached to the IUS, which is attached to a tilt table, which is attached to the orbiter, and that is what we call the stack. As we prepare to deploy Chandra, we elevate it to an intermediate position, and perform some more checkouts. Assuming that everything is working, we will then raise it to the deployment elevation. When the ground gives us a "go", Cady will throw the "deploy" switch and a charge will fire that will separate the IUS from the tilt table. Chandra will be pushed out of the orbiter by springs, and it will be on its own.
I understand you're going to get a pretty good look at it.
Yes. It will go right over the overhead windows in the crew module, and it's a very big satellite. In fact, when you see it standing by itself in the processing facility in Florida, you're convinced it won't fit into the orbiter, but it does. As it comes out, it will head towards the crew module and we'll get a very good look at it through the overhead and forward windows as it departs. Unfortunately, the ground won't have that same view real time because we won't have television capability until the satellite's gone. Hopefully, we'll have recorded all of that and will be able to share it with people on the ground later on. During the deploy, I'll be sitting at what would normally be Eileen's seat helping Jeff with the orbiter systems and helping Eileen oversee the whole operation. There will be some other activities that are fairly routine and not directly associated with the deployment of the satellite that will take place during those times, and we'll make sure those get done properly.
What will you have to do once Chandra has cleared the crew cabin?
Initially Eileen will be at the aft station where she can control the orbiter. She'll fire a very short, eight-second maneuver that will basically fly the orbiter out from underneath Chandra. That will give us a little bit of separation initially. Because the IUS is a solid rocket motor and it's going to fire an hour after the deployment, we want to move the orbiter to a safe distance to protect the orbiter in case something should go wrong with the burn of the first stage motor. We don't expect that, but it is a routine precaution that we take on every IUS flight. Fifteen minutes after the deployment we'll fire one of the orbital maneuvering system engines for a thirty-foot-per-second burn that'll put us about forty miles away from the IUS. It's scheduled to burn forty-five minutes after our burn. It will coast along on its own with the timers counting down to its burn. After we separate, we will then point the overhead windows again at the IUS/Chandra. We have a radio antenna that is capable of receiving information from the IUS and relaying it to the ground. Basically, we'll be a communication station for the next several minutes, allowing the ground controllers to be able to see how the IUS is progressing on its way to doing its maneuver and its subsequent solid rocket motor burns. We'll provide that service until it's time to actually maneuver the belly of the orbiter to face the motor. That provides the most protection in the event that something should go wrong with the burn. For most of that time, we'll be relaying IUS data to the ground.
I'm sure you've trained for when things don't go as you've planned. What are some of the critical failure scenarios that you've trained for, and how have you and the rest of the crew trained to respond to them?
We tend to train for the most critical failures and not necessarily the most likely failures. The most hazardous failures have to do with the IUS motor firing while it's in proximity to the orbiter. It's very unlikely that we would ever get to a point where that would become hazardous, but those are the kinds of situations that we train for the most frequently because they pose the most risk and they demand the most immediate, correct, time-critical actions. The kinds of things that we do in the simulator are cases where failures in the Inertial Upper Stage make it more likely that something bad might happen. We practice fixing it as fast as we can and getting safely away so that, should that ever happen, we would be well prepared to do that. Again, that is very unlikely, but it is the most hazardous, the most time-critical, the [most] demanding scenario where you can't afford to be slow or do it wrong. Additionally, there are other failures in the tilt table mechanism itself where a jam or an electrical failure leaves the IUS/Chandra at an angle that would be unsafe to deploy it. In that case, we practice reconfiguring the electrical system or mechanical system, or in the worst case, having Cady and Michel manually crank the IUS/Chandra tilt table up to a safe elevation where we could deploy it. I can't remember the last time we ever did a deployment without failures.
In your time as an astronaut, you've deployed five satellites. Does the experience of having been part of a deployment before help you get prepared to do it this time?
It really does. The things that are common are things like the ability to operate in a dynamic environment where the clock is counting down to a deployment event, where time-critical actions are required. You reach points in the timeline where there are major steps that are unrecoverable. You're going to take a step that you cannot back out of and you need to make sure that it's done properly. Even though the techniques are a little different, the thought process of how to deal with that type situation are common. My experience with Hubble and the other satellites I deployed is very useful. Also, I think the experience with Hubble allows me to understand what the investigators need for their satellite. My knowledge of their requirements and of the orbiter allows me to suggest ways that I know we can use our capability to enhance their chances for mission success. That's something we went through with Hubble, and that technique and ability is useful in this application as well.
Chandra is the third telescope of four that are envisioned in NASA's Great Observatories Program. How does what Chandra observes in the x-ray portion of the spectrum complement the observation and research of Hubble and the Gamma Ray Observatory?
The whole point of the Great Observatories Program is to have facilities that will provide the world-class ability to look into distinctly different regions of the spectrum that preferentially highlight different physical processes taking place. The x-rays come from very energetic areas and infrared comes from cooler regions. Compton Gamma Ray Observatory looks at even more energetic phenomena than Chandra can see and Hubble bridges the gap between the infrared and x-rays. Nature conspires to show what it's up to in a variety of ways, but never in the same form of light. It's through this combination of information gathered by these different facilities that enables us to put it all together. It isn't just having access to these different wavelength regions, but it's also having access in a very sophisticated way. We have had access at some level or other in these regions for a long time, and we've made great progress as a result. To have a world-class facility, such as each of the Great Observatories is, in each of these regions is the real step. If Hubble is a guide to what we can expect, our understanding will increase dramatically. Hubble has revolutionized a lot of our understanding of the universe in the wavelength regions we can see with Hubble and so I think it's fair to anticipate that the advances will be as great when Chandra's in orbit.
How have Hubble and the Gamma Ray Observatory helped provide lessons to the engineers and the scientists that are developing and building the hardware of Chandra? Did the difficulty with the mirrors on Hubble give them a leg up on making sure they wouldn't have similar problems?
The mirrors on Chandra have been tested in a facility that was built at Marshall where they actually can shine x-ray light into the telescope and confirm that it focuses properly and it all works according to the design. That uncertainty is not an issue for Chandra. There have also been some other lessons learned, certainly in software. We knew from our experience with Hubble that one of the things it did very early in its life was go into safe mode a lot. Safe mode is designed specifically to assure that the telescope is safe in the event that it suffers failures that somehow compromise its ability to do its mission or point accurately. Early in Hubble's career, it did go into safe mode and the control center had to recover and command it out of that mode. I think it's probably fair, based on that experience, to expect that Chandra may also go into the safe modes that it has available to it. I know one of the things that the control center people have done is to make sure all of those commands are understood and work so that they're well prepared to deal with that in the event that it happens. My recollection is that the Hubble controllers very rarely go into safe mode anymore, but they're very good at recovering it if it does. I expect the Chandra people will have benefited from that experience as well.
How has the field of astronomy advanced since Hubble and Compton have been put into orbit?
It's been really remarkable. Recently, a group of scientists announced a new, more accurate value for the Hubble constant, which is key to understanding the age and evolution of the universe. It was remarkable because that was the project that caused something like Hubble to be developed in the first place. The opportunity to be able to uniquely address the question of what is the Hubble constant, what is the age of the universe, and to have that project reveal an answer is truly exciting. I think that sums up how Hubble has changed the way we look at the universe. People have seen the pictures for a number of years and they're fascinating just by themselves. We've had new insights into black holes and where they exist, into stellar nurseries and how young stars are created, and we've had a look at what could very possibly be precursors to planets developing around other stars. It is very similar to what we had theorized the solar system looked like before the planets had actually coalesced out of the gas and dust that was left over after the sun was born. In many ways, some of the pictures we've seen have confirmed exactly what we thought was going on. In other ways, the pictures have confused us in such a profound way that we have no idea what's going on in other areas. The field has changed so much since I was a graduate student. I remember thinking about and discussing many of the questions, and I think those of us back in those days felt that if we could contribute a little bit to the furthering of our understanding of some of these questions, that would be a tremendous accomplishment. I don't know that any of us felt there was a chance in our lifetimes that questions like "How old is the universe?" would actually be answered with any degree of certainty. These tools give us the capability to actually know the answer to some of these questions, which is really remarkable. So it's profoundly different than it was ten years ago, even.
The Southwest Ultraviolet Imaging System is another telescope that will be with you on the mission. What is an ultraviolet telescope, and what do you hope to learn from these observations?
As the name would imply, an ultraviolet telescope is designed specifically to take data in the ultraviolet part of the spectrum. Ultraviolet light, much like x-rays, doesn't penetrate the atmosphere well, so our ability to look in that wavelength region from the ground is highly limited. We have had ultraviolet telescopes in space before. In fact, Hubble itself has some ultraviolet sensitivity. The SWUIS is actually very much like a moderate sized telescope you could have in your backyard. It will be with us in the crew module, so I actually get to use it like a real astronomer looking through a telescope in the old-fashioned way. We can actually point this telescope closer to the sun than we can with a large, sophisticated telescope like Hubble. Hubble has constraints because the sun is so bright and it focuses so close. It's never looked at Mercury. Assuming that we fly at a time of year when Mercury's available, we can take ultraviolet imagery of Mercury. That would be exciting. In general, the main focuses will be solar system objects like Mercury, Venus, Jupiter, Saturn, and the moon. Many of these objects, surprisingly, have not been studied in this mid-ultraviolet frequency range. A lot of this data will be unique. We're also going to try to look for asteroid-type objects called Vulcanoids that we think reside close to the sun inside of Mercury's orbit. They aren't known to exist, but we think they do, so we're going to take ultraviolet exposures very close to the sun to see if we can detect any of these bodies. We have the advantage of being able to do this above the Earth's atmosphere with a decent-sized telescope, and it could reveal objects we've never seen before. We don't know that it's going to work, but we're going to give it a try. We also have the capability with this telescope to downlink some of these images live, and if the moon is well-placed when we fly, we might get some very nice images of it that we can send down for people to see. There will be very interesting pictures of the planets and hopefully of the moon.
Now that assembly of the International Space Station is underway, most of the space shuttle flights for the next four or five years will be devoted to building it. How do you think basic scientific investigation in astronomy, or other disciplines, is going to fare as we enter the space station era?
The Great Observatories will continue for a long period of time. We still have another Great Observatory to go, the SIRTF, which is the infrared telescope facility. It won't launch on the shuttle, but it's scheduled to launch in the next couple of years all of these facilities are scheduled to operate for a decade or more. That'll be very important for the next ten or twenty years. Additionally, we're looking at what the Next Generation Space Telescope might look like. There are studies underway to try to determine how big it should be, what the design should be, and what sort of problems it should attempt to solve. There's a lot of excitement over what comes even after the Great Observatories Program. The station will provide a platform that will enable us to continue to use astronomical facilities above the Earth's atmosphere. We benefit by being above the Earth's atmosphere in a lot of ways. We have access to some wavelengths that can't penetrate the atmosphere, and we don't get the smearing effect that the atmosphere has on objects that we're trying to study from the ground. We'll have this permanent platform in orbit where those conditions will always be favorable for us. I'm very hopeful that ten years from now we'll be talking about things that we had no idea about in 1999.
There are quite a few other secondary experiments that are going along with you on your mission. Tell me about one or two of these other payloads and the kinds of investigations that'll be conducted during this five-day flight.
All of these other experiments are trying to understand fundamentally what happens to different systems, in many cases physical systems, when they experience weightlessness. One of the experiments is called STL-B, Space Tissue Loss. We will fly some plant cells and they will be caused to begin to mature. What happens on the ground is that the nucleus in this plant cell will migrate around for about twenty-four hours and then under the influence of gravity will drift to the bottom of the cell where it'll split. Half of it will become the root and the other half will become the plant. The question is what will happen to the nucleus without the influence of gravity? What will happen to the plant? Will it know what to do? Nobody knows. That plant by itself is not necessarily all that important, but the fundamental understanding of how these physical processes take advantage of gravity is important to know. We have a couple of other experiments that have to do with similar kinds of physical processes. We know that the immune system in the human body is somehow suppressed by being in weightlessness. We don't really understand why that happens. We're flying some experiments that will hopefully address some of the possible causes of what suppresses the immune system. Being able to understand and potentially control that would be important for human well being in long-term spaceflight. All of the experiments are designed to try to understand physically what is behind some of the phenomena that we've observed to be the case in weightlessness.
It seems like it's going to be a very busy five-day mission. If you are talking to people outside of NASA who don't have any special knowledge about what's going on, how do you explain STS-93's role in advancing the goals of space exploration?
Primarily there's our involvement with Chandra. The ability to put [up] the third facility in our Great Observatories will be a major contribution, and that is the main goal of the mission. Besides that, we will be conducting a number of experiments to incrementally improve our understanding of basic physical processes that happen in outer space. One thing that we're doing is a treadmill experiment that will have implications on International Space Station. The exercise that you do for long-duration spaceflight is known to be very important to your physical well being and your ability to recover once you come back to the ground. We're striving to make the exercise more Earth-like for a variety of reasons, including the effectiveness of the exercise on maintaining bone mass and other physiological attributes that will help us recover when we come back from missions. We understand after ninety-four space flights on the shuttle that exercise is very important, and we understand to some extent how it effects the human body. We're still trying to improve it. We know that the human immune system is suppressed, but we don't understand all the physical reasons for that and we don't know how to control it. We also know that bacterial control in water systems in zero gravity is more difficult than it is on the ground, but we don't know why and we don't know how to control it. If you could characterize our contribution, I think it would be to help us move forward in our understanding and our ability to deal with the things that we now understand are products of being in space. We'll add our little pieces together to hopefully resolve some of these things.
Give us your perspective on having been a part of the American space program for more than twenty years. You and Shannon Lucid are the only astronauts out of that first class that are still active. Tell us how NASA and the manned space program have changed during your time here and in the time since the Challenger.
I think that one thing that's changed is our understanding of how the hardware performs. We have taken advantage of the fact that we've got almost twenty years experience of flying the space shuttle. We have an understanding of how the hardware works that is probably much better than what NASA had in a program like Mercury, Gemini, or Apollo. That by itself is interesting, but the important consequence of that understanding is that over time, we are able to devote more of the shuttle's capability to the accomplishment of the mission objectives rather than to assure a safe launch and return. As we got more comfortable with the reliability of the systems, we were able to focus more on the accomplishment of the mission. We could never have done something like Hubble servicing in the early days because it would have been too risky. Now we're able to accomplish missions like space station assembly and Mir docking missions as a consequence of our understanding of how the system works, our confidence in how to train, our ability to simulate, and our ability to develop software and hardware products. Additionally, I think we have learned how to manage an open-ended program. One of the things that I thought was the case around the time of Challenger was that we had not really learned how to evolve from managing a program with a clear beginning and clear end point to a program with no clear end point. I think it took us a while to migrate our management approach to how to deal with an ongoing program when many of us had been used to a finite program that we knew was going to come to an end. Now we do that very well and we make investments in our infrastructure. We recognize that orbiters need to be periodically maintained in a more major way than what we do between flights in Florida. Now we have maintenance periods for each orbiter that we do out in California at Palmdale. We've come a long way in being able to maintain an ongoing program.
Now Americans, Russians, Canadians, French, Japanese, and others are flying in space together and building a brand new space station. Is this where you expected space exploration to be when you showed up at the Johnson Space Center twenty-one years ago?
It certainly is where I dreamed it would be. There were times early in the program when I would never have imagined that we'd really be repairing satellites in orbit, building space stations, flying international crews, docking to Russian space stations, and launching Great Observatories. Those were all things that we dreamed of doing, but seemed unachievable. The fact that we're actually able to do it is an amazing tribute to the people that have been part of this program for all those years. Dreams do come true in that sense as well. That's what we thought we'd be able to do, and that's what we did.