Preflight Interview: Andrew Thomas

The STS-102 Crew Interviews with Andrew Thomas, Mission Specialist.

Q: Andy, tell me why it is that you wanted to become an astronaut in the first place?

A. Well, like many people in my generation, I grew up in the heyday of the space program, and I saw the early flights - Mercury, Gemini, and then the Apollo flights, the flights to the moon - and they were, of course, just absolutely captivating. They were just extraordinary spectacles and amazing events in human history, and I looked at that and I thought, "What a wonderful program it would be to be involved in. What a great opportunity." It sort of inspired my passions back at an early age, and that stayed with me and ultimately led me to seeking an application and trying to become an astronaut, which I successfully did.

Tell us about the steps along the way. Astronauts become astronauts in many different ways. For you, what was the way through education, through career?

Well, of course, as a young kid growing up in Australia, the likelihood of me being selected as an astronaut was pretty thin, and I didn't really consider it a very realistic possibility. But I'd always been interested in things technical and in engineering, and I took engineering courses at the university and ultimately [earned] a Ph.D. because of a natural interest in those kinds of things - in science and engineering. And then I was working in the United States in the aerospace community for some years when I realized, in fact, that I could develop the credentials that would be needed to put together a good application to become an astronaut. And once I'd made the decision to do that - quite a number of years ago now - I focused my career goals on that. In other words, I took steps in my career [that] I thought would give me exposure to the right kinds of technical problems and technical experiences which would make me a good candidate for an astronaut position. And, after I'd done that, I submitted an application and ultimately was selected.

As you look back at those steps along the way, who is it that you see as the people who were or perhaps still are the most significant influences in your life?

Well, there [are] significant influences in terms of people motivating me to take engineering and people motivating me to seek a Ph.D. and then to take career steps. But actually I think the most significant incidents in my life are not so much to do with people, but they are events in themselves. As a kid in the late '60s, [I] watched Stanley Kubrick's film "2001: A Space Odyssey," which is really interesting because that's a film about a spacecraft called Discovery, which in 2001 is making this mission. And here it is now 2001 and, lo and behold, I'm flying on a spacecraft called Discovery. Now, we're not going to Jupiter, of course, but it is a bona fide space flight nonetheless. If someone had told me when I first watched that movie thirty or more years ago that I would end up in this sort of metaphoric situation, I would have just said, "You're absolutely mad. You're out of your mind." But here it is. It's happened, and I think it's just been an extraordinary adventure.

This flight is coming a little more than two years since you returned to Earth from your four-month mission on board the Mir space station.

That's right. Yeah.

How was your readjustment to life on Earth after having spent so much time in the absence of gravity? How did it compare to your recovery from your first space flight, your short shuttle mission?

My first flight was a ten-day mission, and when you readjust to gravity it takes a few hours but the body adapts very quickly. By the next day or so, it seems to have lost all memory that it's been in zero-gravity for ten days. Now, when you do a long flight, the situation's completely different because one of the extraordinary things that happens on a long flight is your body adapts to the environment. And although the environment is totally alien and unnatural, your body starts to accept it as being natural, and psychologically you accept it as being natural. You start to feel that being weightless is just the normal way to be - that everything does float, and that you float. It's just the amazing adaptability of the human body, I suppose. And, of course, the downside to that is [that] when you come back, you have to reeducate your body to working in gravity. And suddenly you feel, when you get back, that this thing called gravity, which you've lived with all your life, is the most alien and unnatural thing. You feel all your internal organs being pulled down, your arms being pulled down, your head being pulled down, and you stand up and just feel this ponderous mass of your entire body. It gives you a perspective [on] gravity, I think, that people just generally never can get unless you go through that. You realize just what a demanding force it actually is. And it demands respect, as you find out after you've been back a few days and these muscles, which have been sort of on vacation for four months and you've put them back to work, start complaining. And after a few days back on the ground, although I was walking around and doing everything - functioning - I had lots of aches and pains. I felt like I'd run a marathon without training for it because all of these muscles were complaining at being put back to work. And it takes quite a while - a week or a couple of weeks - for those muscular aches and pains to really go away and probably a month or more before you really feel normal in terms of your physical responses.

As we said, it's been a couple of years now. You're feeling fine now. You've had time to reflect on the whole Mir experience, from the training and the preparation to actually flying the mission. From this perspective - a couple of years off now - what are your thoughts? Was it a very positive experience?

Oh, absolutely!

One that made you a better astronaut?

Well, I certainly hope so. Yes, it was a very positive experience. I think the people that flew on the Mir spacecraft had different kinds of experiences, different quality of experiences. I didn't quite know what to expect when I first went on board. It was obviously a very unfamiliar environment. It was not just a space station, but it was a Russian space station, so it was with some sort of trepidation that I had about what the experience was going to be like. But now in hindsight, I can reiterate the feelings I had when I first landed, that it was a fascinating and unique experience. I consider myself especially fortunate that I am one of the few people who has actually done a long flight on the Mir space station. And I think if you look at space flight in the last decade of the 20th century and you ask yourself, "What would be, for the technology available then, the most unique space flight experience that you could have?" I think you would have to say it was flying on the Mir space station for an extended duration. And it was a unique and very personally rewarding experience.

What are the most important lessons you learned?

Oh, I learned that living in space and living in the confinement of space is something that I can do, that I'm comfortable with. I learned that you can adapt to it very easily. I learned how to function in that environment and to make use of the very limited resources available to keep myself motivated and to enjoy the experience. It just was a wholly fascinating experience. It's very hard to describe the quality of an experience like that because there's very little here on Earth that matches that kind of experience - of being weightless 24 hours a day, that everything you do is weightless. Seeing the entire Earth sixteen times a day as you go around in orbit and all those sunrises and sunsets. All the weather changes, the seasonal changes, seeing all the continents and all the oceans. It's kind of a humbling experience to think about it. It still has - even though I did it - an air of unreality. It is just so hard to sort of picture that environment. But I actually did it, and it was really a very fulfilling experience.

The Shuttle/Mir program was Phase 1 of the International Space Station Program. The flight you're preparing for now is [in] Phase 2. Do you see the value - the lessons learned - in Phase 1 being applied now?

Yeah, absolutely. In fact I think it would have been very hard to have imagined taking on the ISS program as we have now without having first [doing] the Phase 1 program. It taught us a lot. It taught us about how to work with our Russian colleagues, it taught us a lot about their systems - not just their technical systems but their organizational systems, their management systems their production systems, and all of that. It taught us how to fly to and from a space station to rendezvous with it, how to bring goods to it, how to bring crew and goods back from it. So there was an awful lot that we did learn, which I think has helped us with the International Space Station. It's also taught us from the lessons learned how to design the International Space Station, what kind of characteristics that vehicle [should] have in order to provide the kind of laboratory environment that we need. So, yes, we learned a great deal by doing the Phase 1 program. I think it's benefited the ISS program enormously.

Let's get on then to the details of the mission for which you are now preparing. If I could get you to summarize the goals of STS-102, what is this mission designed to do?

Oh, a number of things. Probably the most significant aspect of the mission is that it is the first crew rotation flight to the International Space Station. We'll be bringing up Expedition 2 and bringing back Expedition 1, who are up there now and have been up since October. So, that's a very historical event in terms of the development of the space station. So that's very exciting. We're also, of course, installing various components on the outside of the space station during a series of two or three EVAs, so those are tasks that are very important to the overall assembly of the space station. And we're also taking up the first Multipurpose Logistics Module, which will carry goods and equipment that the crew will need in order to bring the U.S. Lab, which has gone up on 5A, into full functional operation. That's also a very important facet of this flight. So, it's really a flight that's got a lot of very rich engineering activities in it.

Among the cargo inside this logistics module are what are called "racks" for use in the U.S. Lab module, Destiny. Can you [tell] us basically what a rack and then what kinds of racks are in the cargo on your mission?

Yes. The racks are essentially large containers about three feet wide and about six or so feet high, that essentially, like a cupboard, if you will - you could almost think of it in those terms -can contain equipment. It can contain scientific equipment, or it can contain bags for stowage or anything like that. So it can be configured in a whole lot of different ways. And, by having them in the MPLM, the Multipurpose Logistics Module, once that's mated to the station, we can then take a rack, as an integral whole unit, out and float it through into the space station and install it in the Lab, ready to go. Rather than having to take a whole lot of individual and small components, piecemeal, across, we could take a whole integral unit across, and that makes transfer a lot more efficient. And, of course, it means that the equipment that you're transferring can be pre-configured on the ground, checked out on the ground, and made operational. So, it greatly improves your probability of successful operations.

And throughout the life of the Lab, it allows for racks to be exchanged and different things to be done.

That's correct. You can exchange racks, and of course, we're taking racks up but we can, over the course of the flight program, bring racks back so that equipment can be brought back. That was one of the things that came out of the Mir program - the problem of not having a good down-mass capability, as you would call it. In the operations of the Mir, with the very small Soyuz, there was not much opportunity to bring equipment back. So the first time I floated on board the Mir space station I was kind of overwhelmed by the volume of equipment that was stowed off in every nook and cranny on the space station because they had nowhere to put it. We will have the capability to bring equipment back in these racks within the MPLM, and that equipment can be serviced and repaired, if necessary, on the ground and then reflown at a later date if, if so desired. So, that gives us a lot of flexibility.

And as I understand it, it's equipment that can be for scientific experiment purposes as well as operational purposes.

Oh, the racks can be configured to contain a whole variety of things. You can configure a rack so that it just contains bags, and within those bags you can have logistics, supplies, consumables, anything you want. Or you can configure a rack so that it actually contains boxes of electronic instrumentation, pre-wired together to perform certain scientific experiments. It just depends on what the user requirement is.

You mentioned earlier that these racks are riding to orbit inside a Multipurpose Logistics Module out in the payload bay. Tell us a bit about the background of this "moving van" module and how it's going to be used in the future to move cargo back and forth.

It's probably about the size of a minivan in length, perhaps a little bit wider. It's circular, and it contains sixteen of these racks - four on each side, four on the floor and, of course, in zero-gravity, it can have four in the ceiling just as easily. And it rides up in the payload bay of the orbiter. We don't have access to it through a tunnel or anything, so it's not like Spacelab or SPACEHAB, where we could physically go into it. It's closed off. It is pressurized, but it's in the payload bay. And what we will do is when we get on orbit and we're docked with the space station [is] lift this MPLM up, using the robotic arm, out of the payload bay and mate it to the side of the station. Once they perform leak checks, they will then be able to open the hatch between the MPLM and the station and have access to it and access to all the equipment on board, which will then be transferred into the station. Then, whatever needs to come back will be transferred into the MPLM. The hatch will be closed. It will be demated using the robotic arm from the station and reinstalled into the payload bay of the orbiter for the flight home. So, all that equipment can be brought home with integrity.

The module is the first of three of them [that] are the contribution of the Italian Space Agency.

That's correct, yes.

Did they just build it, or did they have the idea for this reusable, plug-in module?

I do not know when the original idea came from, but certainly, it has been built by the Italians according to the specifications of hardware required to fly on the space station. They've done a good job of it. Ours is called Leonardo. It's a nice piece of engineering. I've seen it down at the Cape, and I'm looking forward very much to floating into it and seeing it mated to the space station.

There's other cargo on your mission that's going up in an unpressurized state out in the payload bay for use during the space walks, and we can talk about the particular pieces as we get to the space walks. I want to get you to talk a little bit about what's going to happen when the shuttle first docks to the station. That day, the hatches are to open for a few hours in order to accommodate the transfer of one new for one old station crewmember. What's necessary in order to complete a transfer, to make it "official?"

This is, of course, something we learned a lot from the Mir program, about how to do crew transfer. It's not sufficient to just have someone say, "All right, I'm going to float over into the shuttle right now, I'm a shuttle crew person." It's somewhat more complicated than that because you have to consider contingency cases. And you have to say, "All right, now, if something was to happen, this person, instead of coming home in the shuttle, would need to stay on the station or go home in the Soyuz that's parked there as a lifeboat in the event of an emergency on the station." Now, if they're going to fly in the Soyuz they need specialized pressure suits. They need a [specially designed] chair that fits in the Soyuz and which is contoured to their body and things like that. And so, we don't just transfer a person. When the person goes onto the space station, we have to change out all of this equipment from the old crewmember for the corresponding equipment for the new crewmember. And so there's a very large package of equipment that goes with the crew person, which is part of the transfer, and it's not really until that equipment is transferred and that Soyuz capability is provided for the new crew person that we can say that person has transferred. But once that's been done, then that person is now a member of the station crew, and the person they've changed out with is now a member of the shuttle crew. We have suits and, of course, clothing and equipment on board the shuttle for them.

In this case, this first transfer, Yury Usachev, the Expedition 2 Commander, will be moving on to the station but not in exchange for the current station Commander; instead for the Soyuz pilot, Yuri Gidzenko.

That's correct.

What's the thinking behind that?

Well, it actually works out quite well. Yury Usachev and Yuri Gidzenko both fly the center seat of the Soyuz, so it's very logical that they change at the same time so that the seat allocations in the Soyuz are preserved. But the main thing, of course, is that Yury Usachev will be the Commander, and he needs to work directly with the Expedition 1 Commander, Bill Shepherd, on what we call handover. He needs to learn about all the systems that Bill Shepherd's been operating and been responsible for during the first increment, and so it's very important that he get a lot of time, one-on-one, with Bill Shepherd. That's why he's exchanging first, and Yuri Gidzenko will come to the shuttle and then Yury Usachev can spend this very important time doing handover operations with Bill Shepherd.

On STS-89, you were in the same position at this point that Yury Usachev is of moving from one crew to another and onto another vessel. Any sense of what the emotion [is] that goes along with that?

Well, it's very interesting, you know. When that happened to me on 89, people said, "Oh, you're going to be sorry to see the shuttle go. You're going to feel lonely, you know. You're not going to want to see the shuttle go." Couldn't be further from the truth because what you are there to do is fly this long-duration mission. You've been training for it for a long time, and finally you're getting on with it. And so, the reaction you have is, like, "At last! I can go and do what I'm here to do." So, you actually kind of look forward to getting to that point because it lets you start what you really want to be doing and getting involved with it. On 89, when the shuttle left, my colleagues left, you know, I was sorry to see them go, but on the other hand I was kind of pleased to be getting on with the task that I was there to do. While the shuttle is there you're sort of in this halfway state. You may have completed the technical aspect of the transfer, but the shuttle's still there and your colleagues are still there. And it's not until the shuttle actually leaves that you really can accept and function as a station crew person and become involved with the long-duration space flight. Until the shuttle goes, you don't do that. So I think Yury Usachev's going to be excited to be transferring. I think he's going to be very busy. He's going to have a lot of work, and when we ultimately leave, I think he's going to be very pleased that he's getting on with the task that he's been sent there to do.

As we said, this is the transfer that occurs on docking day. The others will come later because the following day is the first space walk of this mission, and the other Expedition crew members, Susan Helms and Jim Voss, are the ones who are going to go outside to do the space walk. Tell us what you're going to be doing during this first space walk, and then, talk us through the sequence of events. What happens outside the shuttle on that day?

During this first space walk, I will be working with our Pilot, Jim Kelly, and both of us will be operating the robotic arm because a large part of the space walk will be done using the arm. He and I will both be operating that arm to help the crew persons outside doing the EVA tasks. There [are] a number of tasks they're doing. Because we're going to mate the Multipurpose Logistics Module to the station, we have to clear a site for it. The site that we want to mate it to actually has, right now, a Pressurized Mating Adapter on it, a PMA. That PMA's going to be moved at the end of the first day EVA. So Jim and Susan will go out to that PMA, and they'll disconnect all the cables from it that join it to the Node so that we can actually then move it without the cables interfering. So, they will do that. Then, we're going to move it to a site on the Node which has an antenna on it - what we call the Early Comm antenna - which is no longer needed. So Jim and Susan will go to that site, and they will remove that Early Comm antenna and install that and bring it back. We'll bring it back in the airlock. When those tasks are done, the next task they're going to do is to do with the Lab Cradle Assembly, the LCA. This is a unit that's mounted on a pallet in the payload bay of the orbiter, and it needs to be installed on the face of the Lab module. This is a system that will ultimately clamp the truss segments to the space station as the build cycle continues, so it's a very important piece of hardware. It's actually what we will use to bolt the clamps the trusses to the station. So they're going to retrieve that from the payload bay and ride up on the arm to the forward face of the Lab, where it will be installed and bolted to the side of the Lab itself in preparation for the task coming, in later flights, where the robotic arm, the station robotic arm, and ultimately, truss segments will be mated there. So this is a very important piece of hardware, it has to be installed and they will be doing that. The next part of the EVA will be to do with the PMA move that I talked about. We have to move this Pressurized Mating Adapter from one face of the Node, around 90° to another face. Normally, when we do things like this we have lots of systems that provide the alignment and visual cues to do the mating. It turns out that, with this particular configuration, we don't have a lot of those cues, so we're going to be using the EVA crew persons potentially to help us with that task. If it turns out that we can in fact do the mating using the on board systems that we have - cameras and so on - then we will mate it, and we will use a system called Space Vision System, which will help us do that alignment. But if that proves not to be accurate enough, we will actually have Jim and Susan on site there, and they will give us verbal commands as to how to guide the PMA and mate it. I'll be operating the robotic arm during that phase of the operations. I'll be listening to them, and they will be telling me, "Left, right, port, starboard, up, down" and so on, in order to get it perfectly aligned so that we can mate it to the Node to clear the site so that the MPLM can subsequently be mated to it. The [fourth] task of that EVA is to do with a piece of hardware called a Rigid Umbilical. Essentially, it's a long, thin pallet that contains some cables. It's in the payload bay of the orbiter, and they will take that up to the side of the Lab and bolt that to the side of the Lab and take the cables that are on it and hook into a panel on the side of the Lab. And this is actually a very important set of cables because it provides power and data to connections that will be used in a later flight, 6A, for the space station robotic arm. So, if we're going to run the space station robotic arm properly, it's very important these cables get routed and connected, and that's what they'll be doing.

If I could take you back briefly to the task of moving the Pressurized Mating Adapter - from where you will be, on Discovery's flight deck, will you be able to see the PMA with your eyes at any point in this movement?

No, we will not. We will be mated to the Lab, which will be in effect coming up out of the payload bay, and it will obscure our view of these operations completely, which will be on the other side of it. That's why we have a very heavy reliance on cameras and things like that. And that's another reason why we'll be making use of the EV crew persons: because I have no visual cues that give me direct sight to it. So it's very important that I have good guidance commands, and if some of the camera systems fail, that's why we will use the EVA crew persons.

During this space walk and all these activities that you've discussed, what are the station crew members doing?

During that first space walk, the new Commander, Yury Usachev, and the older Commander, Bill Shepherd, [will] be doing handover - exchanging information on operating procedures of the station. They will also be doing transfer of equipment and preparing for the arrival of the two new crew members, who will be coming on board in subsequent days.

The first of those other two crew members comes the following day, along with the installation of Leonardo onto the Unity module. Tell me about what's going to happen that day.

That'll be a busy day because there will be a crew exchange so all that equipment that goes with the crew person will have to be transferred to ensure that it's a proper crew exchange. When the MPLM task is taken up, what we're going to do there is lift the MPLM up out of the payload bay and mate it to the side of the station. It's quite a demanding task. It weighs something like twenty-thousand pounds, so it's, we have to do it fairly carefully because it does require a certain amount of precision in alignment and orientation to make sure it mates properly to the station. But once it's mated and the hatches are open, the station crew now [has] access to all the equipment on board, so they're going to have to go to work transferring the various items on board into the Lab. And some of that equipment's very important. For example, within Leonardo, we're carrying the robotics workstation for the International Space Station. This is the system of video monitors, computers and hand controls that will enable operators to actually run the space station robotic arm when it comes up on 6A, so it's a very important piece of equipment, as you can imagine. They will be transferring that and doing some checkout of that equipment. They'll be transferring a DC-to-DC Converter Unit that's in one of the racks that will be providing power for the Lab module. Obviously, that's a very important thing to have. There [are] a lot of tools, logistics, water transfer equipment. There's a cycle ergometer exercise system that has to go across and things like that. So, they're going to be very busy getting all of that equipment across. And some of it needs to be done fairly promptly because we want them to have it on board for a while and operational so that we can confirm that the equipment we've brought is functional and that it is able to be left there. And were it not functional, of course, we'd want to bring it back, and if that was the case, we'd want to know it fairly early on in the flight.

I want to get you to talk a little bit more about the job of mating the MPLM to the station. If you think about the geometry of how that's set up, it seems like it's a pretty clear shot from the payload bay to Unity. Is it a very complex maneuver to grapple that and remove it and install it?

It's a little more complicated than you might think because you lift it up out of the payload bay, and it's held in by four trunnions, which run in guides. So you have to lift it carefully so that they come up smoothly between the guides, [and] it doesn't twist around or anything like that. Once you get it well clear of the payload bay, you actually have to rotate it slightly to match its orientation to the orientation it needs on the station, and then you have to bring it up to the station. And you can't just bring it in a straight line there, you actually have to follow a sort of a curved trajectory or you can run into problems with the arm and what are called singularities in the joints. It's where you're trying to move the joints the wrong way. The arm is called an arm for a reason. It's very much like a human arm, and just like a human arm you have certain degrees of freedom, certain motions that you can do. But there [are] some motions you can't do, and if you try and do them, you just can't. Well, that's true of the robotic arm as well, and so there's a trajectory that we have to follow to keep away from those regions to get a smooth flight up. Then once we get near to the mating interface, we have to have very careful alignment of the MPLM as it comes in. And to do that, we're using what's called a centerline camera, which is a camera that's actually on the station that'll look out at the MPLM. With the motion that the camera sees, we will be able to determine whether the MPLM is too far starboard, too far port, pitched, yawed or something like that, and we'll be able to make corrections to bring it in and mate it.

When - I'm skipping ahead, I realize - but when this module is demated from Unity, is it just a reverse of the same steps, or are there other complications in putting it back in the payload bay?

It is a reverse of the steps, but of course, demating it from the station's easy. You just back away. You don't have to follow this very careful sort of alignment bringing it in. You can just back away and clear the structure. But then when you get down into the payload bay, and you're reinstalling it in the payload bay, these four trunnions, which latch it to the payload bay, have to be lined up fairly precisely with the guide rails so that you come down between them. And the catch for all of this is that I won't be able to directly see it. I'll have to rely on cameras once more to tell me where it is, and I'll have to infer its position from camera cues. And so you have to sort of keep your wits about you as you do it to make sure that what you're seeing - and what you think is happening - is indeed what is happening, so that it comes in smoothly and evenly and settles in at all four points simultaneously.

Let's get back to the point where we've jumped off our story. The day after you have successfully mated Leonardo to the station is the day that the second space walk of this mission is scheduled to occur, but the roles being played by crew members will have changed dramatically.

That's right.

Starting with yourself - you're going outside. Tell us about the second space walk.

Yeah, the second space walk is one that will be performed by myself and Paul Richards. Jim Voss, who would've done the first at this point, will have become a crew person on the International Space Station. Susan Helms, who also did the first, is now our IV crew person. She will actually be directing Paul and myself throughout the course of the space walk. We have a number of tasks that we're going to perform. The first of these is that we are carrying a unit called the Early Ammonia Servicer, which is a large set of ammonia tanks in an installation about the size of a large office desk, if you like. It weighs about fourteen-hundred pounds. It's in the payload bay on a pallet. We have to take that, lift it up out of the payload bay with the robotic arm, and install it on a trunnion on the P6 truss on the station. That would not be too difficult a task were it not for the fact that the robotic arm can't reach this particular trunnion. So, what we're going to do is unbolt it, lift it up, and get it as close as we can to the work site, which is well above the nose of the shuttle, up and forward. It's a very interesting place, where Paul and I will be, and we will take it from the arm and move it down and manually install this fourteen-hundred-pound mass of tanks onto this trunnion pin. So that's going to be a fairly delicate operation because, although it's weightless in space, it still has mass, and fourteen-hundred pounds of mass is a lot of mass. It's three-quarters of a ton, so we're going to have to very carefully, by hand, move this mass down from the arm and install it on this trunnion pin and lock it in place. Once we've done that, we will run some cables to it to provide power to its on board systems - its heaters - and then we'll be done with that. The next task concerns what we call the early stowage platform, or ESP. This is a platform that's designed to be installed on the outside of the Lab, and it provides you a place to install equipment that you might need for future operations. This platform is about six feet long and about a foot wide, and it's on a pallet in the payload bay. What we're going to do is manually unbolt it. At this point, I will be riding on the robotic arm. Paul will pass it to me, and I will take it as the arm flies me with this platform up to the side of the Lab, where I will install it on one of the trunnion pins on the Lab and bolt it in. And then we will run some heater cables to it to complete the connections. The third task that we're doing also involves that stowage platform, but there's another unit that we need to install on it, and this is called the Pump Flow Control System. And this is a system that's a backup to the Pump Flow Control Systems that are already on the P6 truss. The photovoltaic system uses [a] flow of ammonia to provide cooling to itself. In the event that the ammonia system was to fail, we have the Early Ammonia Servicer that provides backup ammonia. We also have this Pump Flow Control System that provides a backup capability to pump it around the loops should that be necessary. So we're leaving this Pump Flow Control System there for contingencies, and were it needed, the Expedition crews would go outside and bring it up to operation. So we're going to take this from the payload bay. I'll be riding the arm once more, and I will hand-hold this unit and carry it up to the stowage platform that we installed an hour or so before and basically mate it to the stowage platform and leave it there so it's available as a backup system should the primary system fail at some point.

And we should say at the time you and I are having this discussion, [it] looks like there could very well be a third space walk on the flight to give you more time to accomplish some of the same tasks.

Yes. The question has been raised - I think fairly - that these tasks from these two EVAs… Would it be better in fact to spread them out over three EVAs? That would give more time for us to deal with the move of the PMA in the first EVA, which is a very important task, and free up the EVA crew persons to support that task. That means some of the other tasks would roll into a third EVA, and we're going to look closely at that and see how to script it.

And assuming that third EVA is the way the timeline finally lays out, it's followed by another day's worth of exchanges, including that of the final crewmembers in which Bill Shepherd leaves the space station.

That's correct. At this point, Susan Helms will [change] positions with Bill Shepherd, who will have, by then, completed his handover as Commander, and he will come on board the shuttle, completing the entire crew transfer. Of course, there's still a lot of work to be done. There's still equipment on board that needs to be transferred between the two vehicles mostly from the MPLM. There's still a lot of discussion between the two Expedition crews about day-to-day operations - what we call handover - to make sure that the new crew persons understand where everything is and what the day-to-day operational procedures require and things like that.

And you've already discussed, I think, about how on the following day, the Leonardo module will be removed from the station and put back in the payload bay. [This] brings you, for all intents and purposes, to the end of the docked operations - about a solid week's worth of time together. [Will there be] a farewell ceremony? What kind of mood is there on board a spaceship like this when two crews are about to part?

Well, you know, I experienced that myself when I flew on the Mir space station. It's a mixed feeling. After you've had a long flight, you are, of course, keen to get home and tell people about it and just get back into your normal life again. You look forward to that. But on the other hand, you look at the experience, and you say, "This has been a wonderful experience. I've enjoyed it, and it's coming to an end," and you feel a certain sense of loss that it is coming to an end, that it's over, that you may not get to experience that unique opportunity again. So it is sort of mixed feelings to have the excitement of coming home with the fact that you know your mission is, in fact, coming to its conclusion.

The hatches will be closed. Discovery will undock, and, in fact, fly around the station a bit before leaving. Tell me about what's happening there.

Yeah. We typically do flyarounds after we do the undocking. A large part of the reason for that is to get good photo-documentation of the state of the station, of all the external systems. We'll be able to see all the equipment that we've installed. It's actually going to be a very interesting time because we'll get to see all the work sites that we were clambering over during the EVAs. For the Expedition One crew persons, it'll be a particularly interesting moment because they're going to see a station that's going to look very different from what they saw when they first arrived. It now has the P6 truss on it. It has the solar arrays. It has the Lab. It's going to look a completely different vehicle, which they will not have seen. And so it's going to be very interesting for them to look up and see the vehicle that they've been living in for four months and see how it's evolved during those four months of their tenure there.

During the time that the two crews are together and during the time that you're all coming home, the returning crew members are going to be heading back toward a one-gravity environment that they've been away from for four months - something you're very familiar with. Talk about what it is that they'll be doing and how you and your crewmates will be working to try to help prepare them for what's going to happen to their bodies as the shuttle lands.

We actually don't have much time after the undocking. We have basically one free day where we'll be together. That'll be a day for us on board the shuttle to do a lot of housecleaning, a lot of stowage of equipment on board, tidying up, hopefully get a bit of time at the window, too, to enjoy the view. The Expedition crew persons will be exercising. That'll be important to them. We will also be going over with them the operation of the suits and the seats and things. This is equipment that they're familiar with, but, of course, they won't have seen it for four or five months. So we will give them some little training sessions on all of that so that they're familiar with it - particularly the use of the recumbent seats and how that's going to work. We will prepare the vehicle for its last day and go over now, as a group, what we're going to do on the final day - for deorbit - and who's got what responsibilities, to make sure that everyone understands what needs to be done, when it needs to be done. We have planned all those activities, but, of course, we've not been able to do them in detail with the Expedition One crew persons since they're not on the planet. But this'll be a chance for us to go over all of that activity with them and make sure that they're ready for it and that they know what's going to be coming.

And you are going to have the - I don't know whether it's the special job or what - of being down on the middeck with the three of them on the way in. What is it that you will be able to offer?

I think I would have to say to them, "When you land, and you finally reach wheel stop, and you're back in this gravitational field, you'll be lying down, and you might think that everything's fine because you're going to feel remarkably comfortable when you're lying down." But, I would say to them, "Don't let that fool you, [because] the moment you stand up or move your head, you're going to have the most bizarre responses." And so, I will encourage them to stay in their seats until everyone else is off the vehicle - until I'm gone, too - to make sure that we're not in their way. And then, I would say, "Let the technicians coming on board help you. Don't try and be a hero or anything. Let them help you. Just stay in your seat - and you can loosen your belts and so on, of course - but stay in your seat until it's time to go. And then there'll be plenty of people there who'll be experienced and know exactly what to do. Let them take care of you.

Sergei and Yuri have both experienced this before, both having had long-duration missions. It'll be a first for Commander Shepherd.

Yes, it will. And, of course, Sergei and Yuri, when they came home from their long missions, they come home in a Soyuz, which is a very different kind of vehicle. And they'll be quite a bit more comfortable in the shuttle. It is a bit misleading because you're lying there and you feel very comfortable until you move. The first time you move your head or you sit up you, you just can't imagine what it's like. The first time I sat up on the runway and moved my head, I just couldn't believe how fast the cabin was spinning around! It was just a very strange sensation, and you just don't want to push it too hard.

Andy, we've talked a lot about the "what" and the "how" of this mission. I'd like to end by asking you, "Why?" What do you see as the goal of the International Space Station Program?

There [are] lots of goals, and you hear these talked about a lot - about the scientific return and some interesting science investigations. And these are all noteworthy goals. But, to me, personally, the ultimate purpose of the International Space Station is to teach us how to live and function on a long-duration basis in space - how to deal with the problems that of that environment, how to deal with transfer of logistics, how to make systems operational so that they don't require a lot of maintenance, or that if they do they can be repaired on orbit by crews. This is all information that we want to know because, one day, we're going to go beyond Earth orbit to Mars and the Moon, and if we're going to do that properly, then we need this stepping-stone. We need to understand the environment we're in and how to make these spacecraft work. And to my personal way of thinking that's the great benefit of the International Space Station. Aside from the human benefits on Earth and the international collaboration, it's going to give us the means, the knowledge and the wherewithal to step out into the solar system and answer some profoundly important questions about the origin of life and the origin of the solar system. I think those questions are probably some of the deepest philosophical questions that remain to be answered, and it will help us get to that point.