KYLE HERRING: Good afternoon, everybody, and welcome to the Johnson Space Center for today's briefing. Once again, as the Shuttle's Program Manager, Ron Dittemore, he'll have some comments updating us on the timeline that occurred on Saturday of the re-entry of Columbia and some other items for you, and then we'll throw it open for questions. I have one hour for today's briefing, so we'll try to get to as many questions as we can today. With that, I'll turn it over to Ron.

RON DITTEMORE: As you know, our recovery efforts are beginning to really pick up steam. The coordination amongst all the engineering teams and outside agencies is really looking good; it's beginning to come together. We are making progress, but it's a massive job and it takes all of our attention on a daily basis. We are still working twenty-four hours a day in many areas gathering information, reviewing our engineering analysis and planning for the future on what we need to do both in the coming days and coming weeks.

Identifying the items that are being recovered is time consuming. It's difficult, but as we met with our people in the field today, we understand that the process of collecting the debris and relocating it to our staging areas is really picking up steam and I think that's going to progress rapidly over the next couple of days.

As of yet, I still do not have any recovered items of any special significance. However, we have put in place a process whereby if we identify something that we believe to be significant, we will red tag that particular piece of debris and immediately send our engineering technical people to review it.

Literally hundreds of people are involved around the state and hundreds supporting in many different locations. I mention to you again the National Guard, the local law enforcement, state officials, FEMA, EPA, FBI, NASA officials, just a large cooperative effort that is working well to try to help us understand the cause of the loss of the Columbia and its precious crew.

Today I intend to give you additional updates and technical data. I know there's a lot of information or a lot of interest in the analysis that we performed during the mission on the debris impact to the wing and I will talk to you a little bit more about that today. I also have some information that -- some additional information on the timeline as far as what happened and when and I'll update you on those -- those events.

But before I get into that, I would like to take some time and talk about the members of this team. As I've watched them respond to the events that unfolded on Saturday morning, at all times it was a group of individuals certainly with sadness and disbelief in their eyes, but never a hint of panic. These men and women performed flawlessly, recognizing that they had lost members of their family, as we treat the crew members in this community. They continue to stay at their posts and do the jobs that we needed them to do. I'm extremely proud of the members of our team all across the country.

A wise person told me a long time ago that true character is revealed when you come face-to-face with reality and when you come face-to-face with adversity. And certainly these last few days have been a real challenge on his personally. But I couldn't be more proud of the team. Under difficult and adverse circumstances, they have performed in the highest manner and they continue to do so.

Tomorrow, as you know, we're going to pause and reflect upon the crew of Columbia, their lives, their contributions, their memory. And although we cannot stop our investigation and the recovery effort, we will pause in this location to take the time to reflect upon their lives, their sacrifice. It's a day of remembering, it's a day of remembering our friends, and for us it's a day of mourning.

Out of respect for the crew and their families, I will not do a press conference tomorrow. I will meet again with you the day following. If there is any significant events that occur, we will alert you to those events; that will be done out at NASA Headquarters. But for us, tomorrow is a day for our reflection and a day for us to pause from these activities for a small time.

Let me talk to you a little bit about the timeline and update you on some of the changes from yesterday. I'm going to run right down the timeline as I did yesterday and I'll try to identify the specific engineering information that has changed.

At 7:52 a.m. Central Standard Time -- I believe I started yesterday at 7:53, I'm going to back up one minute -- at 7:52 a.m., we have identified that three left main gear brake line temperatures showed an unusual temperature rise. This was the first event, the first occurrence of a significant thermal event in the wheel well on the left-hand side.

At 7:53, as we were passing over California, we've identified that a fourth left brake line strut actuator and uplock actuator temperature measurements rose significantly. Yesterday I reported twenty to thirty degrees increase in five minutes, now we believe it's more on the order of thirty to forty degrees.

At 7:55, a fifth left main gear brake line temperature showed unusual temperature rise. 7:57, as we were passing over Arizona and New Mexico, the upper and lower left wing skin temperatures failed off-scale low. At 7:59, as we were passing over West Texas, I mentioned yesterday that we had evidence of increasing drag on the left wing, that the aerosurfaces were reacting to that drag to maintain our attitude and trim. We also now have identified that in addition to the aerosurfaces, that the yaw jets on the right-hand side, two of the four yaw jets were firing, they fired for one and a half seconds, again trying to help aileron and the elevon surfaces counteract what we believe is the increasing drag.

And although I said yesterday that it was well within our capability to maintain attitude, it was well within the flight control system's capability to handle the excursion. As we have continued to pour over the data, it's not the absolute value of the attitude change that is interesting, what is becoming interesting to us now is the rate of change.

The aerosurfaces were doing what they needed to do to counteract the drag on the left side of the vehicle. The right yaw jets had to kick in to help the aerosurfaces and it appears that we were losing ground as far as the rate of attitude excursion. It was not long after that point that we lost all data and communication with the crew.

We are still looking and processing for -- we are still looking for additional information. I talked to you yesterday about thirty-two seconds. Retrieving that data is not as easy as we originally thought and so it may take us another day or so to extract that information and determine whether it's going to be useful to us.

We also hope to go out directly to the White Sands terminal where the data comes down from the satellite directly into White Sands. It's then relayed from White Sands over to the Johnson Space Center. We're going to go directly to the White Sands equipment and see if we can extract additional data, and so that's -- that effort is continuing.

So again, there is certainly an interest in the wheel well. I caution you about conclusions. A temperature increase of thirty to forty degrees in five minutes within the wheel well does not indicate that we have something structurally going on. The outside temperature's above two thousand degrees. You see an increase in the wheel well of thirty to forty degrees seems to indicate that that's not the point of any large thermal excursion, that's reflecting something else.

Remember I told you yesterday we had an increase of temperature on the left side of the vehicle, on the mid fuselage, I believe I told you sixty degrees in five minutes, but a delta change in temperature of sixty degrees again does not represent a structural problem. So even though these things are interesting to us, we're still trying to find what caused these temperatures to increase. And given the fact that the outside temperature on the wing leading edge is two thousand degrees, these relatively small increases in temperature are telling us something, we're just trying to find out exactly what they're trying to tell us. Did we have some type of penetration in the wing that the left main landing gear and the left mid fuselage were just reflecting an overall increase in temperature but were not the exact point of the penetration? That's what we're trying to figure out.

So you can't draw the conclusions that the left main gear of the wheel well we had a breach there. If you had a breach there, it seems logical that the temperature would be higher than just thirty or forty degrees from what we normally expect. But, again, we're early in this investigation and we're still poring over the data, and this is the fluid nature of the business. So be cautious about those conclusions. We are certainly trying to be cautious ourselves.

I'm going to talk to you a little bit now about the tile analysis. I know there are a lot of questions about that. I'll try to go through that in a fair amount of detail to help you understand what occurred. The first thing I'm going to do is talk to you a little bit about the timeline, the events, when we did certain things, and when we finally concurred on it not being a problem.

Launch occurred on the 16th of January. The first film review occurred the following day on the 17th. The first engineering meetings occurred on the 20th. We reported to the Debris Assessment Team on the 21st, which means the engineering teams were starting to do their work; they were trying to understand exactly what this debris was and so they spent a day reflecting upon it, identifying the assumptions that they needed to utilize in their analysis, and they reported to our Debris Assessment Team on the 21st. They completed an engineering analysis on the 22nd, final engineering reviews on the 23rd and the 24th, reported to the Mission Management Team on the 24th and again on the 27th. Both those times reporting to the Mission Management Team, the conclusion was that the debris that impacted the vehicle did not represent a threat to the safety of the crew or the vehicle.

Now I'm going to talk to you a little bit about the assumptions used in our analysis, because I've heard a lot of discussion in the last day concerning those assumptions. The size of the debris utilized in our assumptions was twenty inches by sixteen inches by six inches and the weight was two point six seven pounds. The size was determined in two ways: One, we looked at the film and we estimated to the best of our ability the size of the debris. Secondly, we utilized the information that we gained on STS-112 where we had debris from the same area shed from the tank. The difference on 112 was that we had the film that the flight crew shot of the tank after the main engine cut off and after ET separation, and as the ET was separating away from the orbiter, the crew was able to take pictures of the tank and we clearly identified where the debris came from. And because of those photographs, we were able to understand the size of the debris that departed from the tank. We knew the size and location and that's why we could tell you it was from that bipod region and based upon those photographs, we determined that the size of the debris being somewhat conservative was what I told you, twenty inches by sixteen by six, and the mass of that particular piece of debris again determined based on the density of that size of debris.

As we performed the analysis, we looked at different incident angles. The debris is not going to hit the underside of the wing at a ninety degree angle, it's coming from the tank and the orbiter relationship. If I can use this model for a second, the tank debris is coming from here, it's transporting down to the bottom of the vehicle at a slight incident angle and it's going to impact a wing and come off. It's not going to hit directly ninety degrees. So as it comes into the wing, you have to calculate how much energy it has depending on the mass and the size, so that's very important to us. We looked at incident angles varying from ten degrees, thirteen, and sixteen degrees, again, trying to bound our analysis. We varied the weight of the debris, again, trying to bound it.

We utilized a program, a tool that we have that we've used many, many times to predict the penetration of any coating or the penetration of any tile based upon this debris. And this, we know from tests and we know from previous flight experience that this particular tool overpredicts damage to the bottom of the vehicle, the tile or to the wing leading edge. We've used it in the past when we have shed debris, we have used this results, its predictions and compared it to actual flight experience when the vehicle returned and we were able to measure the debris, so we know that it overpredicts. It also has some conservative -- some conservatism in the model itself. I won't go into those details; I haven't got those all captured for you yet. But I wanted to give you that background.

As we completed the analysis, trying, again, to understand as we normally do the worst case, we looked at two primary -- well, we looked at more than two, but the two worst cases were the loss of a single tile near the main landing gear door and we also looked at the loss of multiple tile, not that we lost the entire tile, but we lost a portion of the tile in a larger area, and the area we looked at was thirty-two inches by approximately seven inches approximately two inches.

So our model was predicting that we could have damage to the bottom of the wing near the left main gear door and on other areas most predominantly outboard from the main landing gear door to the tip of the wing, depending on the incident angle and depending on the size or mass of the debris, so it varies.

For the loss of a single tile at the main landing gear door and for the other case where you had more acreage damaged, the thirty-two by seven by two inch area, in both those cases the analysis predicted that even though you might have structural damage, and what I mean by structural damage is localized heating where you may have some effect on the basic structure in that area, even though you might have localized structural damage, you would not have damage sufficient to cause a catastrophic event nor impact the flying qualities of the vehicle.

Now, today we are also going to release to you our daily mission evaluation room reports. I believe we have fifteen reports and you can read through those reports and it will reflect a lot about what I have just told you probably in less detail than what I just shared with you.

So why don't we stop at that point and give you a chance to ask me some questions. And again, I'm sharing with you information, as much information as I have available, and again ask for your indulgence as we change this information from day-to-day.

KYLE HERRING: Let's start over here with Bill, please.

NEWS MEDIA: Bill Harwood with CBS News. Ron, I'm curious. I agree, I was kind of looking at the wheel well, but from yesterday I was kind of baffled by that sensor up on the side of the fuselage and trying to figure out how you get heating effects above the wing if something's going on in the wheel well, and a physicist told me that you don't conduct heat up the side of the fuselage fast enough to reflect what's going on here. And when you're talking about possible other penetration areas, I want to make sure I don't misinterpret what you're saying.

You're saying, I guess, it's possible that you could have a penetration somewhere besides the main landing gear wheel well, get some heating going on in some of the structural boxes of the wing itself, and then perhaps have something happening in that nature, but you're still talking about heat from below that would be somehow in the wing structure itself, then manifest itself somewhere else.

RON DITTEMORE: Yes, that's exactly my thinking also. I'm speculating a little bit here, because I have no data or evidence to really say that's what happened, but I'm trying to think in my own mind how would the temperature increase in the wheel well and on the side of the fuselage and still end up with an event that lost the vehicle. It does not seem logical that the wheel well is the source of the problem, because the temperature does not reflect it. We've had now five different temperature sensors all showing forty, fifty degree increase over five minutes; the side of the fuselage showing an increase. There's some other event, there's some other missing link that we don't have yet that is contributing to this temperature increase and we've got to go find that.

KYLE HERRING: Let's go right here to Cherise.

NEWS MEDIA: Cherise Donte with the Palm Beach Post. Mr. Dittemore, I'm wondering, is there any type of contingency entry scenario in which you would be able to by, say, inducing a yaw during descent protect one wing over the other even if it's by a little bit? And also, did you see any increase in skin temperatures on the left wing near the leading edge?

RON DITTEMORE: We have not seen any increase in skin temperatures that I am aware of. I'm reporting to you all the information I have. I mean, you've got everything I know. And if we do, I'll tell you as soon as I find out.

I'm not aware of any other scenarios, any other techniques that would have allowed me to favor one wing over the other. And obviously, you know, think about that for a second. If you favor one wing over the other, the wing that's not being favored is getting really hot. And so I'm sure that we didn't develop those scenarios, but I don't know for a fact that we couldn't have. I don't know for a fact that the analysis -- the analysis would have showed that it was not feasible. I can certainly ask some of our engineers and talk to you in the coming days, but I'm doubtful that that's the case, just from my knowledge of the thermal conditions.

You would also have had to make a judgment that you wanted to fly that way and sacrifice the vehicle, because you cannot meet your landing conditions by protecting one wing over the other. What you're really trying to say is can I enter through the atmosphere, preserve one wing, because you think it might have some damage, and still make my landing conditions way down range. That's not going to happen. You would have had to make the decision that you knew so much information about the damage on the wing that it was going to fail if you didn't protect it, and then you would have had to make the decision that you were going to sacrifice the vehicle and get to a certain altitude and ask the crew to bail out. That's the scenario that you're asking me about.

And I'm sure you understand that for us to have made that type of decision, we would have to have absolute sure knowledge, and I don't believe that there is going to be any sensors or any pictures or any photographs or any video that would have got us there. So we can speculate all day long about what we could have done, but I just don't believe that we would ever have had enough information to make those type of risk traits. So be cautious about that line of thinking.

KYLE HERRING: Okay. Let's go to Mike and then right here.

NEWS MEDIA: Mike Cabbage with the Orlando Sentinel. Ron, as you continue the process of recovering and sifting through the debris, what are the two or three items that you are most anxious to find that you think are the most crucial to helping you unlock what happened?

RON DITTEMORE: We are extremely interested in any debris upstream of the primary impact area. We've all seen the debris map as it stretches from Fort Worth through -- down through Lufkin and even to -- into Louisiana. We are primarily interested and certainly if we can find wing debris structure tile, but if we find any tile or structure upstream of Fort Worth, New Mexico, Arizona, if that exists that is extremely important to us, because that's going to be a real key in the puzzle.

And so we have received a large amount of information from the public on what they have seen, and based upon those reports, we are methodically following up on each one of those reports to try to understand whether they were fooled by a phenomena that is natural or whether they actually saw something that would be of concern to us as far as the health of the vehicle.

And then you have to think about this for a second. Let's go through this scenario in your mind: Let's say we did shed a couple of tiles. You're at two hundred and twenty thousand feet or so, because now we're at California, Arizona, we're descending rapidly, we're going through mock twenty, nineteen, eighteen fairly quickly, and you shed a piece of tile or two that are six inches by six inches. Where are they? That's a difficult problem. But we have people seeing if we can solve that problem.

You have to know the characteristics of the tile or piece of material that you're looking for, it's traveling at high speed and it's at high altitude. And we have tools that will help us predict where that type of debris may land, but it's like looking for a needle in a haystack. But that's not a -- that is not going to keep us from trying to look for it, and so we have a special team that's following up on each one of those reports, we are analyzing the potential where the debris might have landed if there really is debris and searching for any key perimeter that might unlock the mystery to this tragedy.

KYLE HERRING: Okay. Right here and then right here.

NEWS MEDIA: Mr. Dittemore, Jenny Blankenship with KI News out of Austin, Texas. Have you reviewed the ascent telemetry data to see if anything hit the left elevon? And also, you mentioned the dimensions and the possible weight of the debris that came off of the external fuel tank. Once again, do you have any way of measuring or of at least estimating the mass of that?

RON DITTEMORE: The mass is going to be the weight, it's going to be two point six seven pounds. That's going to be the striking energy. The mass or weight of that amount of pounds combined with the velocity as it impacts the wing is all going to be converted to energy. And you saw some of that, if you saw the video on the film that I know that you have, as it struck the wing, it basically disintegrated into a cloud of smaller particles, so it went from a mass of two point six seven pounds into the wing, dissipated its energy into a cloud of dust, basically, and what we're trying to understand is because of that dissipation of energy, what impact did it have on the tile. And that's what our analysts tried to do during the flight by assuming one tile completely missing and damaged and then assuming another scenario where you -- instead of removing the tile, you actually scooped out material representing several tiles. And then we looked at the thermal properties to see if that would represent a safety concern. And in both cases, they did not. In both cases, what we believe the worst case to be was perhaps a local penetration, local structural damage, perhaps some local yielding of the structure because of the temperature, but not to the degree that it would violate the structural integrity of the wing or its structure, just in very local areas.

KYLE HERRING: Right here and then right here.

NEWS MEDIA: Charles Galvin with CNN. If we can explore just a bit this missing link that you're looking for, and I recognize this is a fluid situation for you, but it seems as if what you're saying now is you're not really comfortable with the notion that there was an event that began in the wheel well itself or the door of the wheel well, you don't seem comfortable with the notion that the debris that fell off the booster would have been of sufficient impact to have caused the catastrophic event that we saw on Saturday. Can you give us a sense of what are some of the operating theories that are being explored that you think are logical that you feel comfortable with that in your mind might help explain to your satisfaction what could have caused this kind of event?

RON DITTEMORE: Well, it's a mystery to us. And we seem to have some conflicting information. But the information of the temperature increase in the wheel well, even though it's small, it's unusual, it's not normal. The mid fuselage is not normal. That seems to indicate that we have some type of thermal event going on. Where that thermal environment is coming from, we don't know. It does not seem plausible to me and to our engineers right now that the genesis of the problem to be in the wheel well. That does not seem plausible to us, just because the temperature should have reflected a greater rate of increase if you were getting the plasma into the wheel well. So there must be something else and we don't know what that something else is, and so that missing link is out there, and here we are forty-eight hours from the event. So we're still struggling with it.

We've made significant progress from Saturday to today, and I think over time we're going to make more progress. If we can get our hands on that piece of debris that really helps us indicate where the genesis of the problem is, that would be very important. If we find a piece of tile, each tile is individually coded and if we find that tile and can decipher the code, we'll know exactly where it came from on the wing. And that's the missing link that we're trying to find. Once we piece that together, then we can map it and then make it fit the scenario. We have pieces of information, but I think it's around the edges, and that missing link is out there and we just need to be persistent and go find it.

I'm confident that we'll get more information that will help us come up with a plausible scenario. But we may never know the exact root cause because we may never gather all of the evidence to pinpoint it happened at this location for this cause. We may never know that, and so we're going to have to use our best judgment as to root cause. But we're going to -- we're going to work our darnedest to figure that out and fix it.

KYLE HERRING: Okay. We'll get Marcia and then Mark.

NEWS MEDIA: Marcia Dunn, Associated Press. Ron, all these meetings that were held between the 20th and the 27th, do you have any idea of how many engineers were involved in all these various meetings? And during this time and even after that, was there any concern expressed by even a single individual, any reservations to the conclusion that ultimately was made?

RON DITTEMORE: At the time, I'm not -- I was not aware of any reservations by any individual on our team. Certainly if you -- if you extrapolate out our analysis and look at the worst case and say "but what if we're wrong?" that is not uncommon in our business. In fact, we encourage that. If people are -- they're not satisfied with the results or the analysis or if there's something in their gut that tells them there's more work to be done, we encourage them to come forward and talk about it. And at the time I was not aware of anybody that had those feelings, at least to the point where they would want to come forward and identify that there's still something that they think remains undone.

We also have a system, we have a reporting system, a safety reporting system agency-wide that any individual can identify a concern, a safety concern. They can identify their concerns, their thoughts. They could do it anonymously, it's input into the system and we immediately react to it. We received none of those types of alerts.

So even though there -- I can't say for certainty, Marcia, that there weren't people out there that had some reservations. In fact, I would think it unusual that we had a hundred percent of seventeen thousand people that work on this program to have a hundred percent consensus and no reservations. That doesn't happen on even the easiest problems. So I would suspect there were some that had some reservations, but I was not aware of that. And if they did have reservations, at least they weren't brought to my attention.

Now, I am aware, here two days later, that there have been some reservations expressed by certain individuals, and it goes back in time, and so we're reviewing those reservations again as part of our data base. They weren't part of our play book at the time, because they didn't surface, they didn't come forward. But now that the event happened and now that this data has come forward concerning some reservations or even their belief of the worst case "what if?" Situation, we're going to look at that, we're going to pay attention to it.

KYLE HERRING: Okay. I have time for two more here. Mark, and then right here.

NEWS MEDIA: Mark Garreau from the Houston Chronicle. How did you deal with the possibility that this foam was actually more massive because it had ice in it or on it? How did you eliminate that possibility? Or did you consider it? And I'm just wondering, you know, altogether are you now taking this off your list of possible contributions to the accident?

RON DITTEMORE: I don't think I'm smart enough today, Mark, to talk to you about the ice contribution to the mass of the debris. I may have to work on that a day or two, and ask me that question on Wednesday. I'll go off and learn some more about that relationship. I don't know that today.

But certainly this debris is one of our primary areas of emphasis. We are completely redoing the analysis from scratch. We want to know if we made any erroneous assumptions. We want to know if we weren't conservative enough. We want to know if we made any mistakes, and so we are redoing the complete analysis.

Secondarily, we have a team of engineers and managers and technicians that are working to understand the shedding of the debris itself from the external tank. And this is how we're approaching it: We're making the assumption from the start that the external tank was the root cause of the problem that lost Columbia. That's our starting point when we look at the tank. And based on that assumption, what is the fault tree that would substantiate that particular assumption. And so we are attacking that.

That's a fairly drastic assumption and it's sobering, but we've asked our ET, our external tank project, management and their personnel, and our contractor to make that assumption and see where that leads us. And so even though that's a drastic assumption, I think that's what we need to do.

KYLE HERRING: Okay. Right here.

NEWS MEDIA: Samantha Levine, U.S. News and World Report. Is there any expectation that all these pieces of debris that you're finding scattered over this large area are ever going to be pieced together as a way to possibly reconstruct what happened? And if so, where that might occur? Would that be at Barksdale or would that be in some other location?

RON DITTEMORE: Well, I'm hopeful that the areas that we are most interested in we will find enough debris to reconstruct. I'm really hopeful that's the case, because if that's not the case, then identifying the missing link is going to be much harder.

As far as the staging area, all that debris that we gather is going up to Barksdale Air Force Base and that's going to stay there for the immediate future. We are discussing where the final resting place of this debris will be, and I believe by the time I talk with you again on Wednesday, we'll have that nailed down and agreed to and I'll be able to let you know where we think the final resting place of all this debris will be.

KYLE HERRING: Okay. Let's go to Florida for five questions from the Kennedy Space Center, please.

NEWS MEDIA: Ron, this is Craig Covault with Aviation Week. Viewing from the drag side of the equation, are you equating loss of specific tile acreage to the drag figures you're seeing? And relative to the overall Columbia tile picture, not the debris hit issue, did Columbia have any unusual tile pull data either at Palmdale or here at KSC after the HST flight?

RON DITTEMORE: That's a good question, and because we've asked that same question and one of the teams that we have established of many teams is to go back and review the inspection work, the modification work, and any tile work that was performed at the Palmdale facility in California, and so that's an action for us to go complete. That's just one of many teams. We're looking at our commit-to-flight process, we're looking at our inspections, we're looking at flight control systems, we're looking at our aero and thermal environments, many others, and so that's just one of several that we are looking at. And hopefully as we work ourselves through this investigation, we'll be able to, in some cases, rule out certain areas, because we'll have enough information that clearly points to the fact that it is not a problem, does not -- it does not represent a contributing factor. And there might be other subsystems that are in the gray area that we don't have enough information to rule them out, and then there are clearly others, like I mentioned to Mark, on the external tank and the tile systems that are more in the higher area of focus than some others.

So at this stage with only forty-eight hours behind us, it's all open, we haven't ruled out anything, but eventually we're going to be able to rule some subsystems out as a root cause.

NEWS MEDIA: This is Chris Kridler from Florida Today. A few years ago the Southwest Research Institute did a report for NASA on the impact of foam on tiles and what that meant, and NASA told us today that that report was impounded and I wondered why it was and if we could actually see the results of that.

RON DITTEMORE: Well, I think generally we have impounded information that we believe would be helpful to our investigation. I don't -- I don't know for a fact whether that particular report is impounded or not. And if it is, I don't know the reason why that would be at this point. Certainly that type of information is going to be useful to us. We'll just have to work our way through this period of time.

But I should share with you that we have more things impounded today than we really need to have impounded, because we're overreacting at this point to make sure we don't lose any evidence or any piece of information that might be an important contribution for the future. So we are being conservative, we are overreacting, and over time you're going to see us back away from the current state of affairs, you're going to have to give us a little bit of latitude there and work with us, but we're going to share with you as much as we know.

I've got a special team. Their entire objective twenty-four hours a day is data and record handling, and there are many people, even in our engineering teams, that want access to certain pieces of information that is embargoed. And we have a team that allows the release of information. That's their specific assignment and duty. So even in our own teams we're struggling with getting some access to data and we're working through it, again, reacting to our over conservatism. But give us some time, we'll get to the right level, you'll get the information.

NEWS MEDIA: Ron, this is Stefano Coledan for the New York Times. I have a question which is a follow-up to Mark Garreau's question earlier. The debris I saw in the ice team film clip is not orange, it actually looks white, so I was wondering how sure can we be that it's actually foam or is it maybe the other side of the foam with ice on it?

RON DITTEMORE: Well, if you read the mission evaluation report that we're releasing today, it also says that as it impacted the wing, there was a white cloud that formed. I don't know what to do with that yet. I don't know if that's a poor choice of words and a better choice of words should have been "light" rather than "white," because we're dealing with something that we're trying to visualize from a long-range camera and it had an impact. And it certainly was light colored, whether it was white or whether it was very small particles with the sun reflection, I can't tell you today. And I'm not sure that when we wrote the report that we really understood what we were talking about. And I'm not sure that it was white or light colored, and that's one thing we need to recognize as we go back and reanalyze, we're going to get to the bottom of that particular description.

Even when I read the report ten days ago, whenever that particular event, approximately ten days ago, even before the end of the mission, I read that particular report with "white" description and circled it and wrote "light," to ask the question "Are you sure it was white or just a light and a reflection?" So we're digging in to that. I'm not sure that means anything today.

NEWS MEDIA: Ron, it's Jim Banke with Space.com. Some questions related to debris. First of all, in what you said earlier about modeling debris falling off, are you suggesting that there may be debris, albeit single tiles, west of Texas on the way down? And have you heard anything in the field yet, I know you said you didn't actually look at anything yet, about the state of debris? Is there any early reports that even suggests that what debris has fallen is in a condition that could be helpful? And finally, real quick, have you correlated that observers in California with the timeline like you mentioned the other day that you might have by today?

RON DITTEMORE: Well, the observation that was forwarded to us from California is important to us, because this particular observer described as he was watching the Columbia pass overhead, he describes what he believed was, in his mind, tile falling off the vehicle. Now, whether it was tile or not, I don't know, but we're talking to him and trying to understand from his description what that could have been.

I don't know if there's any debris in California or Arizona or New Mexico. I do know that we found tile in Fort Worth, and so the fact that we found a tile in the Fort Worth area largely upstream of the debris field may be significant. I don't know yet.

Again, because the tile is light, its ability to travel downstream with the rest of the heavy material may have limited it to land into the Fort Worth, Dallas area rather than go all the way down into Lufkin and farther. We're still looking at that.

I'm speculating a little bit if this observation on the West Coast was correct in his interpretation and if we judge it to be the case, if we truly were shedding some material as early as California, that's going to be significant to us. Again, I don't know that to be a fact, and that's why we have a special team whose sole purpose is to investigate those reports and to interview the proper -- or to interview the observers so that we can understand exactly what they're saying.

Now, we get reports from all over the country, so some of the reports are going to not be fruitful to us and others might be, so we're going through the process of eliminating those that aren't going to pay any dividends and we're trying to isolate those that we think are more interesting. And it's still too early for us to tell whether there's any findings in there that could be useful to us.

NEWS MEDIA: Phil Long, Miami Herald. Ron, could you share some more specifics about those meetings immediately following or the day after launch, the engineering meetings, who participated in them, what companies at least, how long did they last, what kind of discussion it was. Anything to just shed some more light on how that came about.

RON DITTEMORE: Well, I wasn't a direct participant, so -- but let me answer the question based on my experience having been in that environment for many years. You would generally have a team of individuals I would say probably less than thirty and that would narrow down to maybe less than ten depending on the real area of expertise and then maybe even down to one or two experts as you start working your way from materials to environment to a bigger picture and all those things come together. And then adding to that team would be our operational personnel, those that operate the vehicle, our flight crew representatives, our safety and quality representatives. And as you start building the scenario and reviewing the analysis, it continues to grow until the point where you brief it at the Mission Management Team.

Independent of the Mission Management Team meetings, we hold additional side meetings with experienced technical managers to review the information, and so it's kind of a check and balance. If we didn't get all of the information presented to us perhaps in the Mission Management Team, we have a check and balance that says did the right technical work get done? Was it reviewed by the appropriate technical management? And do they agree? And so we -- so we have a check and balance system going that says in both cases in case we missed something one way or the other, the combination of the process will allow us to be satisfied that we worked through the process properly.

NEWS MEDIA: Elliott Klineberg, Palm Beach Post. How therapeutic was it for everybody to come back to work today after -- I'm talking about here at the Space Center -- after such a wrenching weekend? And when will you decide the pace at which you're going to continue on the two orbiters or if you're going to stop it while you investigate it?

RON DITTEMORE: I haven't talked to a lot of people and asked them the question "How do they feel." Let me give you some personal experience. As long as I am at work, as long as I am focused on the job that I have to do, as long as I'm reviewing data or reviewing the results of teams, I can stay pretty well focused on what I need to do. The hardest thing that I've had to do over the past two days was drive home in my car Saturday afternoon alone with my own thoughts. I've talked to several others that had the same experience.

As long as we are together, as long as we are trying to solve the problem, we can stay focused, we can keep our energy directed in the right direction. But when we're alone and on our way home or to different places, many have commented that that's the worst environment and that has been our most difficult moment, and it's happened to several of us. And so I would think that many that have come back to work today will find it therapeutic to rub shoulders, to talk about it, to work themselves through the difficulties. I've had many that have sent me e-mails commenting on one thing or another over the last couple days. I've received many phone calls, and for me personally that's made a lot of difference.

When I go home at night and sit there and think about the events and I'm left with my own thoughts, what has been therapeutic to me is to get on my computer at home and have the opportunity to read some of these e-mails where people have expressed their thoughts and their concerns, giving us support, helping us through difficult situations. And I'm sure that's true in many other cases. So it varies with the individual.

Things are getting better. Each day is better. Tomorrow's a day for us to pause and reflect. Tomorrow's a day for us to commemorate. In reality, it's the day for us to celebrate the lives of seven heroes, and so we're going to pause and do that and I think that day is going to be a tremendous benefit to many people and we're looking forward to it.

KYLE HERRING: Okay. Let's go to NASA Headquarters for a question, please.

NEWS MEDIA: Tracy Watson with USA Today. When you first saw the videotape of the debris hitting the wing, was it immediately something of grave concern? Was it ever something of grave concern?

RON DITTEMORE: I'm sorry, I'm going to ask you to repeat that; there was a little bit of static on the line and if you'd repeat it, that would help me.

NEWS MEDIA: Okay. I'm wondering when did -- when you and other managers saw debris hitting the wing, did you think it was a matter of grave concern? Was that something that really posed a lot of worries for you at that time?

RON DITTEMORE: From my position in the Mission Control Center where I viewed the Flight Control Team controlling the re-entry and talking with the crew, I did not have any access to any physical evidence. Our focus was looking at navigation charts, radar tracking charts. Our focus was listening to the flight crew and the Flight Control Team, and we did not have any physical evidence that would lead us to believe that anything was wrong other than the instrumentation dropouts that I talked to you about. But certainly when the instrumentation dropouts occurred combined with loss of data and loss of tracking, even then we weren't very anxious. But as time went on and that time grew without any communication from the crew, and that would be very unusual, then that was very anxious -- that was a very anxious timeframe. And you can only imagine how it felt when someone comes up to tell you that you've lost the vehicle and the crew. I don't think you can imagine that, for us that sit there and work with these individuals. It's not something that I would want you to go through. It's not something I want my team to go through ever again.

But we will recover from this. As I mentioned to you, we're getting stronger by the day. And just as the Phoenix rose from the ashes, we're going to do the same. We're going to find the problem, we're going to fix it, we're going to get back to space flight, human space flight, and we're going to have tremendous successes in the years ahead. And we're going to learn from these events. Our character will be stronger, our resolve will be stronger. We'll be the better for this terrible tragedy. But we have work to do first. But we are getting better.

KYLE HERRING: Okay. That's all at Headquarters. Let's go to the Marshall Space Flight Center, please.

NEWS MEDIA: Ken Falk with Birmingham (CK*) News. There's been discussions about external tank foam striking the orbiter on previous missions. How many times and can you give us specific missions? And was there ever a time when the debris was suspected of causing all or part of the tile to come off?

RON DITTEMORE: This is not the first time that we have had debris generated from the external tank that has struck the underside of the wing. It's not the first time that we have had debris from the bipod area of the tank come loose; it's happened several times. I mentioned to you STS-112. I'm aware of some of the details of STS-50 where we had some debris shed from a similar area on the tank, and when we got the vehicle home, we had some damage to the underside of the wing. It wasn't significant damage, but it was several inches long and maybe an inch or two wide and less than an inch deep. So you can understand some of our data base and some of our thinking that when this has happened before, yes, it could impact the tile, yes, it could take some of the coding off, yes, it could even gouge out some of the tile. But it has never represented anything more than that.

And so when you're an engineer or a manager and you have that data base and you're faced with a similar type of circumstance on STS-107, you draw upon your experience, you draw upon the data available to you, you analyze what's new in the equation and you make your best judgment on what the risk is to the vehicle and the crew.

So yes, there have been some previous occurrences. I don't have all those at my fingertips today. We are gathering that information, and perhaps in future conferences I can share that with you.

NEWS MEDIA: After looking at all the reports from engineers that conclude there wouldn't be a problem, who is the final person who signed off on it?

RON DITTEMORE: The person with the authority to judge whether it's -- represents a risk or not ultimately is the chairman of the Mission Management Team. However, I'm the accountable individual. Anything that happens at the Mission Management Team, I am made aware of. And it's my personal commitment that I don't do anything that would jeopardize the crew or the vehicle. If that means grounding the fleet, we'll do it. If that means scrubbing the launch, we'll do it. Safety of the crew and the vehicle is absolutely paramount. So ultimately it's my decision. And it doesn't matter what anybody else thinks, if I believe it's not a safe thing to do, then we won't proceed.

In this case I did not chair the Mission Management Team, it was delegated to the manager of the program -- the manager for Program Integration who is also serving as the launch integration manager for launch. But I was kept informed and knowledgeable at all times.

NEWS MEDIA: Could you explain the process taken to impound data and hardware and stock work at the External Tank Facility at Michaud and who ordered it?

RON DITTEMORE: I asked that -- for the facilities around the country, I asked that we impound data, that we stop work, and that we determine whether or not there were processes, procedures, or hardware that we wanted to take a look at before we continued to proceed with either manufacturing or production. That was just part of the process. I didn't invent that, it was part of the contingency action plan that we have written down that tells us in these types of circumstances, these are the steps that you take. But we implemented those plans.

That was the very first action, impound the data, preserve the evidence, stop what you're doing and concentrate on preserving what may be important for the future. We have since taken some steps to start back processing vehicles in Florida. For instance, I told you we're doing the maintenance down period on Discovery. I've asked the teams in Florida to continue to process Discovery. There's nothing in that processing that should hinder our investigation.

I've also asked them to continue to process Endeavour, OV-105, so that we can continue to gain in our schedule as far as the work and try to get some things behind us, try not to keep everything in front of us so we don't have this huge bow wave of activity when we get to the point where we're ready to start preparations for resuming flight.

So we have backed off already on some activities. Even at the Michaud plant in Louisiana, we have come to an agreement on what hardware will remain impounded and what manufacturing can begin to start up again. And so we're continuing to pull back and to release certain activities, but we're doing it very diligently, we're doing it with knowledge, we're doing it with forethought, and all that is being done with the consensus in the team.

KYLE HERRING: Okay. Our final two questions are going to be from Lufkin, Texas at the Command Center.

NEWS MEDIA: This is Joe Veringio from the Associated Press. Can you provide us with an update on the collection and identification of human remains?

RON DITTEMORE: Well, as you can imagine, that's probably our most sensitive subject. All I'm going to comment on is the fact that we continue to recover crew remains and we are handling that process with the utmost care, the utmost respect and dignity.

NEWS MEDIA: This is Fernando Sanders from the New York Daily News. My question is I wonder whether there are any plans in place to scan the bodies -- the several bodies of water located within the debris field for any debris that may have fallen in there.

RON DITTEMORE: We had some reports that some observers actually witnessed large pieces of debris going into a lake, a stream, I'm not sure. Certainly we're going to investigate and whether that means we're going to use divers or any other type of equipment or tools, I don't know yet. That's going to be the call of the Mishap Investigation Team and those people that are located on the scene.

KYLE HERRING: Okay. Thanks, Ron.

A couple of closing remarks. As I did yesterday, I'd like to pass on the information for folks who may mind some items, they want to pass that along to the Emergency Operation Center. The phone number is (281) 483-3388. There's also an e-mail address for images that can be sent to columbiaimages@nasa.gov. There's also a physical address for any video or larger photographic items, that is at the Emergency Operations Center, Mail Code JA17, Johnson Space Center, Houston Texas, 77058. So please help us out by getting that information out.

As Ron mentioned, we will not have a briefing from here tomorrow at 4:30, but Headquarters is planning to have one at the same time, 4:30 Eastern Time.

There are two memorial services planned this week, the first tomorrow will be from here at the Johnson Space Center, that will be at 1:00 o'clock Eastern Time and that will air on NASA Television. On Thursday, a memorial service also is planned at the Washington National Cathedral, that, too, at 1:00 p.m. Eastern Time and that also will be shown on NASA Television.

Thank you all for coming.