2010 Space Symposium - Session 3: Space Situational Awareness - Debris Management and Mitigation Strategies

By Moderator: Mr. Nicholas Johnson | Omaha, Neb. | Nov. 2, 2010

MR. GANDY: Boss, I've got to tell you sir, talking about space communications, I got an e-mail just a minute ago from Santa. He said your first wish is granted. We're going to go ahead and press ahead on SSA, and this first panel is going to go ahead and work on that for you.

So the first session we have today is Space Situational Awareness - Debris Management and Mitigation Strategies. As the boss pointed out, it's going to be moderated by Mr. Nicholas Johnson, the Chief Scientist for NASA. Please welcome him to the panel.

MR. JOHNSON: Good morning. General Chilton, Governor, distinguished speakers, ladies and gentlemen; it's certainly going to be hard for me to live up to that introduction by General Chilton.

First, it's my honor to host this first panel here at the 2010 USSTRATCOM Space Symposium. Before I introduce our guest panelists and at the risk of turning the morning session into a well-deserved love fest for General Chilton, I would like to say a few remarks.

General Chilton has made the nation's space situational awareness capabilities and products during the past few years tremendously improved. We're doing things that no one thought that we could ever do before.

Under his leadership and direction, significant improvements have been made to the U.S. ability to observe, to track and to characterize resident space objects and to anticipate in situations which have not yet occurred.

Of particular importance, as the General noted, was the expansion of the satellite conjunction assessment process to include all operational satellites in earth orbit, regardless of country of ownership and the dissemination of the highest quality conjunction assessment information to owners and operators around the world. This is an activity which has actually only been in place for about six months now. The feedback that I received from the commercial and the foreign owner/operators has been extremely positive.

The graphics on the screens around me clearly depict the consequences of more than half a century of international space traffic, including over 200 satellite and rocket body explosions and collisions, as the General said, leading to approximately 1,000 operational spacecraft accompanied by 20 times that number of large debris and smaller but still hazardous debris that exceeds half a million objects.

The international community was once again reminded of the hazardous space debris just a week ago when the international space station had to execute a collision avoidance maneuver to avoid a piece of debris.

The rest of the story, as Paul Harvey used to say, is that piece of debris came off a 19-year-old NASA science satellite which had been nonoperational for five years. Moreover, that piece of debris had come off just a month earlier, four weeks prior to the conjunction with international space station. Had it not been for the tremendous capabilities of U.S. space surveillance network, we never would have known that.

Our panel today will first briefly address the congested state of the current near-Earth space environment and the necessary operational response. We'll also offer a brief status of the space debris population and its likely evolution in the near term and far term, and we'll pay particular attention to space debris management and mitigation measures as well as potential for debris removal. And we'll close out our remarks and give us ample time for questions and answers.

Now, we encourage you to sit back, to listen and take advantage of the opportunity to interact with our space situational awareness experts here today.

Unfortunately, Dr. Polowitch was waylaid by Hurricane Tomas over the weekend in the Caribbean. Nice place to be. I'm not sure what sent him to the Caribbean, but he's not there today. But we have the Special Intelligence Advisor to the Director of the Space Protection Program, Mr. Earl White. Earl?

MR. WHITE: Thank you, Nick. Dr. Polowitch did call me on Saturday afternoon from St. Lucia. He said the hurricane winds were a hundred miles an hour sustained. He had no electricity. The land lines were down. He saw a tree fly by the outside of his door, and he was having a wonderful time. He said, the bad news is I'm not going to make it to Omaha. You know that speech I'm going to give? And I said, no. What speech?

So I'm representing the Space Protection Program. And from the perspective of the space -- of space protection, we're concerned about debris because of mission assurance.

First, we're concerned with debris as a threat to safe satellite operations. And to manage the threat posed by debris, the first thing you have to do is understand the debris environment, and it's a surprisingly complex environment.

There are at least seven different classes, regimes of debris that all act differently, and have different behavior. And to my surprise, the community is still occasionally surprised by the behavior of debris that we see.

As new sensors come online, it's going to be like turning on the porch light in Alabama in the summer. You're going to see lots of objects up there that you weren't expecting to see or we have not yet characterized. And it's going to be important to be able to do that. I mean, we know of at least 2,000 objects at GEO that are there, but we don't track.

So one of the important questions that I have for people like the gentlemen sitting on this panel is what is the future of the debris environment? Because that future tells us what we have to do to assure the mission. Are we going to have to recommend changes to the way we build satellites or the way we operate satellites, or are we going to be able to manage the debris environment sufficiently to ensure the mission?

Second, debris is part of a larger threat environment, a threat environment that includes space weather, and it could include hostile acts. And we need to know the difference between anomalies created by those three things. Is it a weather-produced anomaly; is it a debris-produced anomaly or a hostile act? And there are tools available today that I would like to highlight two that would assist us quite a bit in making that determination.

The first one, today's complicated satellites have sensors on board already, hundreds of sensors for a simple satellite. And for a very complicated satellite, it can be in the tens of thousands of sensors. I'm talking about thermistors and voltmeters and information that are passed back down through the TTC [Telemetry, Tracking & Control] links.

Well, it's possible to look at that information and look for very subtle patterns, and sometimes not subtle patterns in the case of collisions, that will tell you the difference between those different things.

The program is called Satellite as a Sensor, or the Air Force version of its Blue Force Status. And that can distinguish between internal failures, collisions, weather events, perhaps RFI [Radio Frequency Interference]. And it's software that you put in the ground station so it makes no change to the satellite itself. So that's something that I would certainly recommend that we consider when you are looking at trying to distinguish between debris problems and other problems.

Secondly, there are a lot of commercial tools that have been developed in the last couple years that would assist us. For instance, this is one example of a real-time and all-in-all conjunction analysis software. In this case, this is an AGI [Advanced Geospatial Intelligence] piece of software.

It does the conjunction analysis in real-time between every object that we know of in space. Now, this one is operating off of the TLEs, the two-line elements sets. It's not highly accurate, but it's a great way to screen the environment for collisions.

Now, what they've done here is create a 5-kilometer -- really just a circle around LEO objects and a 50-kilometer circle around the GEO objects. And it shows that there is a collision in this case, a conjunction, about once every eight seconds.

Now, those are, of course, really large circles, and you wouldn't -- really wouldn't do that, except as a screen. And then you take the conjunctions and run them through the more accurate software, very similar to what NASA does in their conjunction analysis process.

But my point is that there are tools available today that would help us quite a bit.

Now, third, when it comes to mitigating the debris environment, we recommend doing the simple things first. The simplest thing is to stop producing it and adhere to the voluntary guidelines on preventing new debris generation. And that means to either, you know, supersync at the end of the mission or to de-orbit or to don't intentionally drop off parts, for instance, lens covers that have been known to be dropped off a satellite.

When it comes to removing debris, one recommendation we have is that you don't develop technology, weapons technology, to remove the debris. That's problematic.

Second, we suggest getting rid of the big pieces first. If you get rid of the larger objects up there, then there's no chance for them to become small objects.

And the commercial world has proposed recently several very reasonable space tugs, either for GEO operation or for LEO operation that would be able to grab onto those things and supersync or tug to de-orbit. And in at least one case, the mission would be commercially funded.

So we would very much like to see an international program that would consider flying that kind of service to remove the large pieces, and that would go a long way towards mitigating the debris problem for space protection.

MR. JOHNSON: Our next panelist is Dr. Heiner Klinkrad. He's the Head of ESA [European Space Agency] Space Debris Office. I've had the pleasure of working with Heiner for many, many years. He first got into the space debris business by being concerned about the re-entry of large, hazardous objects in the 1970s and 1980s. We worked together in the UN, the IADC [Inter-Agency Space Debris Coordination Committee].

DR. KLINKRAD: Thank you very much. I believe the task that I have in this panel is to alert you a bit, to scare you a bit on the existing space debris environment and to give you a perspective of its future evolution.

This chart shows you the spatial distribution versus altitude of space debris. One's for 10-centimeter and larger objects, and one is for 1-centimeter and larger objects.

The scale on the left-hand side is the same from both of these charts, so you see that the peak concentrations are about a little more than one order of magnitude apart, so the peaks common in these both charts at 800 to 1000 kilometers, 1,500 kilometers at the semi synchronous altitudes of 20,000 kilometers and at the geosynchronous reading of 20 of 38,786 kilometers.

For the left-hand side, we talk about a number of objects, a little more than 20,000. They have a total mass of about 8,000 [pounds] of about 5,800 tons. If you would squeeze all of that into an aluminum cube, it would have a side length of 13 meters.

Now, if you lower the threshold to 1 centimeter, you'll find that the number of objects is drastically increasing. So we end up with an additional 600,000 objects. However, these additional 600,000 objects just make up for a few extra tons, which would fit in an aluminum cube of a little more than a meter side length.

For the forthcoming slides, it's important to understand some assumptions that we made. We talk about critical size space debris, and critical size space debris is anything that imposes impact energies that lead to a catastrophic break-up. And this, you could say, we have for anything that's larger than 10 centimeter in size when it hits a spacecraft of normal masses.

Such critical size debris, number wise almost corresponding to the objects that we have in the U.S. space surveillance network catalog. As mentioned before, they amount to a total mass of about 5,800 metric tons. The distributions of these critical sized debris is by no means uniform across the used orbits. We have by far the highest concentration of these objects in the lowest orbit regime, where we have more than 76 percent of them, where about 20 percent of those are intact objects. And we have about 40 percent of the mass that is residing in the lowest orbit region.

This lowest orbit region, on the other side, is only making up for about one-third of a percent of the overall volume that we use with spacecraft orbits.

Another important orbit is the GEO stationary ring, which is a sort of (inaudible) of 2,000 kilometers height and width of 20 degrees.

Here we have about one-third of the total mass in a volume which is less than 10 percent of the overall used volume. The count is just a little more than 6 percent, of which most of them are intact. This is because the catalog cannot easily get a hold of fragments which have been created in GEO. And we know that several fragmentations have occurred. Apart from two that we are definitely aware about, there might be another six or eight.

Then we have other orbits which have about 27 percent of the mass and that's distributed over 90 percent of the volume and the count is about 17 percent. Next slide, please.

One metric of the risk we have is spatial density, so concentration of objects in a certain volume. And this slide -- this slide shows such concentrations in a grid of inclination versus altitude.

Of the 16,000 critical seize LEO objects that we have, we have up to 14 percent in a single 50-kilometer altitude bin, around 800 kilometers, and we have up to 36 in a single 2-degree inclination bin. And that would in semi-synchronous orbits at around 100-degree inclination.

You'll see this -- combined in this 3-D chart on the left. Keep an eye on this sub maximum at 72 degrees, 800 kilometers. That's going to be playing a major role in the forthcoming slides. Next one, please.

And a metric for consequences that we have from collisions is the mass that's involved, and up to 2,300 metric tons of mass in LEO. We have up to 16 percent in a single 50-kilometer altitude bin, again, at about 800 kilometers, and up to 30 percent in a single 2-degree inclination bin, and that's about 80 degrees inclinations.

Again, we have this 3-D chart on the left, and you'll see the bar that you ought to have an eye on at 72 degrees, 800 kilometers. That is starting to catch up.

When we go to the next slide, this is a metric that shows us the short-term consequences. The short-term consequences are resulting from the collision probability, which is the product of collision flux times cross-section involved, and what also makes up for the consequence is the mass that's involved.

So here we see that this 72-degree inclination, 800-kilometer altitude bin is starting to prevail. Next one, please.

If we look at long-term consequences, then on top of collision flux, cross-section times mass, which was the short-term consequence, we also have to consider the orbit lifetime. And then apart from this 72-degree, 800-kilometer bin that we were focusing on, there are others emerging in the background from the 1,500-kilometer altitude bin. This is because of the sustained orbit lifetimes that they have there.

However, in the latter two charts we saw, that if we concentrate our efforts on the 72-degree, 800-kilometer bins, we have the chance to remove quite a bit of mass and remove quite a bit of risk within a fairly short volume, which means within reachable domains as far as Delta V for maneuvering spacecraft is concerned. The next one, please.

And that takes me to the conclusions. We can say that the highest count was 73 percent and the highest mass concentration was 40 percent of critical size space objects is in the LEO regime below 2,000 kilometers, which makes up for only one-third of a percent of the populated orbital space.

The bad news is that models for the long-time evolution tell us that a catastrophic collision, such as Iridium-Cosmos is likely to reoccur within less than ten years from now. There are no catastrophic collisions predicted outside LEO regime for the next 100 years.

In spite of that, we do mitigation measures for the GEO region by re-orbiting objects at the end of life to GEO graveyard orbits, and such measures are also undertaken for the MEO region to protect the operation altitudes of the constellation satellites.

Then major contributions to collision risk and to derive metrics of short- and long-term consequences correlated with a few distinct classes of LEO inclinations and altitudes. Highest mass removal rates and most efficient debris control can hence be accomplished by servicing these orbit regions.

Now, these orbit regions, I should probably address in a different context because they are almost exclusively populated by Russian orbital stages and Russian payloads, which raises another issue that even if we have the technical means and the competencies to do so, there might be other obstacles to remove critical mass from orbit.

Thank you.

MR. JOHNSON: Thank you, Heiner.

Our next panelist is Dr. Bill Ailor. He's the Director for the Center for Orbital and Re-entry Debris Studies for the Aerospace Corporation. Like Dr. Klinkrad, Bill got his start in doing reentry risk assessments, but has broadened out to real orbital debris since then. Bill?

DR. AILOR: Thank you, Nick. What I wanted to do was kind of give you a little bit different perspective or something to help sort of frame the debate here.

One of the things you might think about as we go, as you look at the space debris issue is how much of a problem is it, how fast do we have to move, what is it really going to mean to a satellite operator?

And so what we were trying to do was to do a study that would address some of those issues and look at the cost of space debris, how much it's going to affect space operations over about the next 50 years.

And then one of the things you also hear about in these types of discussions is who is going to pay for this. And so the question that you might want to draw from this is; is cost going to be a real driver for developing some mitigation techniques, and then based on those results, what would be a possible strategy. Next chart.

Okay. The way we did this is we basically have models that will look at constellations and how frequently they have to be replenished given the environments and so forth, and we actually used those in this particular case.

We hypothesized three different constellations. One was a government constellation, the second was a commercial, and the third was also a commercial of different types of satellites. These are actually based on actual satellites now, so we tried to make this as realistic as we could.

You can see we have 5 government, 20 in our first commercial and 70 in our second one. And the unit costs vary. The government satellite, as you might guess, is a tad more expensive, typically because government satellites have and carry multiple missions. The launch cost, you can see there, and also the second commercial satellite was a situation where you'd launch five satellites per launch.

And also I might mention the models that we use were already used for assessing things like piece part failures, component wear out, solar ray power degradation and so forth. Next chart.

This just shows, consistent with what Heiner talked about, we wanted to look at sort of a worst case here, so we decided to put our constellations at an altitude where that would be; where we'd expect to see the most number of impacts. Next chart.

And we used a model now that we actually modified. We modified it to include the Chinese ASAT test, debris from that, and also that Iridium-Cosmos debris. That blue line there, as you see, is the one that we were using for this study, and we also modeled three different debris size ranges, 1 millimeter, 1 centimeter and 10 centimeters. The 10-centimeter ones are the ones that you could avoid. Those are the big ones that we've talked about. They're tracked objects. The 1 millimeter and 1 centimeter are objects that you can't avoid because we can't see right now. Next chart.

This shows you the satellite and debris damage models that we used and the rough size of the satellites. For these small debris objects, we assume that these 1-millimeter particles, if they hit a satellite, would basically not cause any major damage unless they happen to hit a really bad place, but generally would degrade solar panels. And you'll see the effect of that shortly.

The 1-centimeter and larger particles, well 1-centimeter to 10-centimeter particles would kill a satellite if it hit it in the wrong place. Think of it as a bullet hitting a spacecraft in a propulsion system or critical electronic component, and anything bigger than 10 centimeters would kill it. Next chart.

So the effects on satellite reliability, and you can see on that left column there it says, Mean lifetime, no debris. That's what the lifetime would be, given the other types of problems that we see with component wear-out and solar panel degradation and so forth. You can see what that looks like.

And then you can see what happens if you put fatal impacts in and you load the launch year there for your constellation and you can see that you do see some degradation in the government satellite but not nearly as much as you do see it with a commercial satellite.

One reason for that we'll see later is the fact that, by the way, you'll also notice on that bottom line that there's a big difference between the fatal impacts and all impacts. And that beginning to show now, that solar panels and these small debris objects can be a major contributor to satellite problems. Next.

This one talks about the replenishment results. And again, the idea here was that you want to maintain your constellations fully configured for a 20-year period. And you can see the number of replenishment launches that are for no debris, with fatal impacts only, and then all impacts. And you'll notice that the replenishment launches vary from, with fatal impacts only from 2 to 8 percent increase, but a much more substantial increase if you look at all of the impacts. Next chart.

And then using the launch costs and the satellite costs to estimate what the costs might be to this debris environment, you can see that again you get a 3 to 18 percent increase if you include all of the impacts, but a 1 to 9 percent increase if you look at fatal only. Next chart.

So in summary, how does it affect the cost of space operations over the next 50 years? We'd expect to see a small, slowly increasing cost due to environment at the high-flux altitude over the next 30 to 50 years, that you'd have a higher increase for commercial satellites due to lower solar panel margins. But increasing solar panel robustness reduces the cost increase by about 50 percent, so that's one thing you could look to do in the future.

Now, the minimal cost increase if you're operating an altitude arranges away from the peak flux. So again, we were looking at the peak flux range, and we'd expect to see minimal cost increase if you move your constellations away from that.

The collision avoidance service, we also looked at the effect of that, and it would reduce the cost increase by about 10 percent.

So is cost likely to be a driver? We don't think it's likely that the increase in operating costs will be a driver in the short term. That would be over the next 50 years or so. So we have some time to start developing these capabilities. Next chart.

And a possible way ahead, then, would be to basically increase the robustness of satellites that impacts the small debris, continue efforts to reduce creation of debris by imposing mitigation standards and requirements and verifying compliance with those, reduce hazards posed by disposal techniques.

And I'm sure you'll be hearing about different types of techniques, so we want to make sure that our collision avoidance services can actually avoid those things being an additional hazard.

Develop capabilities required to remove large debris from high flux regions, and that's something that Heiner talked a little bit about, this idea of getting some of the big objects down.

And lastly, continue the research on the cost effectiveness of debris removal versus cost of operating as a way of assigning and figuring out how you'd actually pay for mitigation in the future.

Thank you.

MR. JOHNSON: Our final panelist here this morning is Dr. Darren McKnight. He's the Technical Director for Integrity Applications, Inc., based in Chantilly, Virginia. I've had the pleasure of working with Darren for over 25 years on a variety of orbital debris topics, and we co-authored the first technical text on orbital debris back in the 1980s. Darren?

DR. McKNIGHT: Thank you, Nick. You got me as an elementary school intern, that would be 25 years ago. I couldn't have been any older than that. Thanks for the opportunity of speaking today.

The most important thing I want to do today is to try and give you one clear message, and that is that I believe that now is the time to start thinking about active debris removal.

Earl did a great job talking about the operational concerns about orbital debris. Heiner showed you a lot of the numbers that are very sobering to look at the growth and the mass. Bill talked about specific mission impact and how we could try to control this. But I really believe that for us to do this right; we have to start thinking now.

I'm going to tell you a few things that you may say, I don't know if I believe him. Trust me, but you can also verify, I have copies of a technical paper I just published in the back of the room on the way out. If they run out, you can give me a business card. I also believe they're going to post the paper. So trust but verify.

First question is what's going to trigger real action? Just as worrying about the terrorist threat to the United States, not much was done until we actually had a terrorist attack. The question is, what's going to make us say we have to do something, have to start active debris removal?

So what I tried to do in this paper is evolve sort of looking at potentially when you might have the hazard growing to the point it might be a concern.

And the first thing I picked was space insurance because that's the first it's going to hit the pocketbook, when actually the hazard is going to increase to the point that it's going to affect your space insurance rates.

And as you see on this chart, some of these things may start kicking in the next couple decades. The problem is, if we try to correct by going after a large object removal type technology, we have to do a number of things.

The “P” on here stands for doing prototyping. Then we have to get regulations and policies. And “O” is for operational testing, and then “E”, where we finally go execute. Unfortunately, as I'll show you in a moment, just having capability doesn't mean that we're safer. It takes a while to get the benefit.

Other people have talked about let's get the medium debris, the 1-centimeter, 5-millimeter. We'll just clean it up after the mess is made. It's very difficult, very, very difficult to do, and it will take a much longer time frame for any of those technologies to actually be able to be fielded and be effective.

So yeah, I know this shows my age as I noticed after I did it, it looked like Pac-man. I didn't mean for it to look that way.

So the real answer is pay me now or pay me more later. We can look at a number of things. We can look at altitude regimes we should go after, debris sizes or what kind of removal techniques we might use.

From that paper I can tell you that really the focus needs to be on, it's a tough call between the tightly-populated region, 850 to 950 kilometers in LEO and GEO. There's a lot of strange stuff going on, as Earl mentioned, in geosynchronous orbit, GEO potential wells that really are counterintuitive to folks that how so few objects can pose such a high risk.

And so it was a tough call for me to say which of these we should go after. But the current collision hazard is much higher at LEO, so I wanted to drill down on looking at the large objects in LEO and active debris removal.

So how do we go about doing this? If you take a look at some work that NASA has done recently, excellent work about looking at the impact of removing, say, five objects each year for the next hundred years and how it could reduce the amount of risk in and control in the stability of the environment, of the debris environment long term. We found it was very, very effective.

What was also interesting to note is that you have to remove about 35 large objects for every 1 break-up event, 1 collision that was prevented. So a lot of people may have first thought if I take out one big object, then I've prevented a collision. If you go back and look at Kosmos-2251, if we were to take a look at a very viable metric right now, which is probative collision times the mass of the object. That's kind of a risk. The overall consequence if that event occurs, that's how we sort of look as the best way to figure out what we're going to take out.

If we went by that metric, Kosmos-2251 as shown on this chart was No. 882. And, Heiner, I hate to tell you this, but (inaudible) about 14 is always up in the double, in the teens. It's high risk. It's an object that when it's not operational anymore, it's in harm's way.

So you can look at some things like this but it may take decades for the impact to be done. If we just do it randomly, it may take -- we need to remove a lot more objects and still take decades for us to get the result.

It would be nice if we were God, right, if we could go down there at the very lower left-hand corner and say, I'm going to know exactly what's going to happen next. I'm going to grab that one because I know.

What can we do to get our numbers a little lower? We could have much more responsive launch capabilities. [That's] Very expensive, [and it] doesn't look like that's in the cards. That's one thing that's very important. We can have enhanced long-term conjunction accuracy.

I know these derelict objects aren't going to be moving, but we can predict better what might occur long term. Again, [it's] very difficult. There are physics problems here that are probably not really viable, but from an academic perspective it's good to put on the chart.

Technology for rapid capture and removal, we don't have great capabilities of doing that right now. When we go grab the Hubble, it's quite a difficult chore. We know the fixtures. We know how to grab things. I know there's many astronauts out there that know -- who have been on the shuttle, when you grab something, it's not that easy. So many, many of these objects we are going to have to do some technology development and testing.

And lastly are optimized selection criteria. As I just mentioned before, the probability of collision times mass is a great way of looking at it, but it's not the only way. The probability of collision times mass is sort of the overall risk, but we also need to look where the objects are because clearly going up and getting one object. It would be nice if there were two or three that were right near each other that you could get. It would be much more effective, much more efficient. Obviously if they're clumped together, there's probably a high probability of collision of those derelict objects coming at each other.

So simplistic here, obviously we don't want to go after the low risk and the things that are far apart. We want to go down in the lower right-hand corner where things are very highly risky, very cluttered but also we might be able to grab a bunch of them on a single mix or single type of technology.

For a specific clump that we looked at, and there were many of these. As a matter of fact, NASA did a fine paper at the recent Prague conference. I asked Congress about the same thing, about where we could look at these clumped objects.

This is one in particular that's very good. Inclination of less than two-tenths of a degree off of each other, 50-kilometer range, and there's 40 derelict objects that amount to a quarter of a million kilograms of mass.

Every one of these are included in if you look at the top hundred objects, derelict objects, on orbit for probative collision times mass, all of them are in that area, in that category.

So the whole point here is if we go after those objects, it's going to take a long time, one, to get a system going, number two, it's going to take a long time for the actual benefit to occur. Because just going and grabbing all those right now is not possible. It's going to take a lot of work.

And by the time that we do get that capability, it may have gone to the point that we have to do everything that Bill just mentioned. We may have to harden spacecraft, we may have to remove the large objects, and we may also have to remove the medium-sized objects.

So again, my final thing is pay me now or pay me more later.

Thank you very much.

MR. JOHNSON: Well, that concludes the initial presentations for this panel.

All right. Space situational awareness. The first speaker mentioned we should not develop methods of addressing space debris that could be a dual-use weapon. Of course, that's in the eye of the beholder. However, he also mentioned that there were several promising space tugs being proposed. The question is how is a space tug not a dual-use weapon? Earl?

MR. WHITE: Yeah, thanks for that question. When I'm talking about dual-use technology, we had proposed a one-point laser technology to ground-based laser technology that would be able to slow down debris and lower at the orbit and let it re-enter.

That's problematic from the point of view of developing laser technology, and it's also problematic from the point of view of the trust me card. There are other nations who wouldn't trust that if we developed that technology that we wouldn't use it, and I'm not sure we'd trust if some other nations develop that technology as well.

I see space tugs in a different class. I mean, almost any technology that you build, there could be a weapons application to it. But, I mean, space tugs are things that you can watch, you can control, perhaps, internationally.

The danger, of course, in picking a solution right now is this is a dynamic field. As you heard from the papers down at the end of the table, the scholarship is changing on it. And of course, my solution, I picked from an earlier paper that Darren McKnight had presented.

So I think the answer is there are different classes of technologies and different classes that can be considered dangerous.

MR. JOHNSON: Okay. The second question is for the debris management panel in general.

Since debris mitigation guidelines are voluntary, what U.S. government strategies would you suggest to facilitate greater adherence to the guidelines?

Let me take this one first.

We spent ten years in the Interagency Space Debris Coordination Committee and the United Nations in developing what are called now the International Space Debris Mitigation Guidelines. They are not voluntary. They are not voluntary in the United States. They're not voluntary in most of the major space-faring nations.

At the UN, they are voluntary, but they are devised and agreed to by every nation (inaudible) and by the majority of the general assembly to be implemented in the individual nation's regulations or law, however, they do it in the individual countries.

So in United States, the U.S. government orbital debris mitigation standard practices are not voluntary. The space debris, orbital debris -- the Space Orbital Debris Mitigation Guidelines are not voluntary at NASA. They're not voluntary at DoD. We have specific requirements.

So I think there's a bit of a misnomer. That's a legal issue in terms of the UN, but in practice, these are not voluntary.

I'll turn this over to Heiner. He can speak for our European colleagues.

DR. KLINKRAD: Yes, they are not voluntary. This I can confirm for the European Space Agency [ESA] since April 1, 2008. We have ESA requirements on debris mitigation, and every single ESA project that's newly put on stage has to adhere to these ESA requirements, which are basically reflecting the core requirements of the UN (inaudible) guidelines, which again reflect the core requirements of the IADC (inaudible) guidelines.

And IADC, with a most likely addition of the Canadian Space Agency, has 12 members now, which includes really all major space-faring nations with just the very, very few exceptions that you might think of.

And all of those are adhering to these requirements. Now, I must say, in the United States you are very well-organized between civilians and military entities. This may be not so the case all over the world.

And I think with our Russian colleagues, we had a little bit of a problem that the military community was starting to voice their opinion after the civilian community basically had, to a large extent, agreed to the IADC guidelines until they reached the UN (inaudible) scientific subcommittee. And only then there was some concerns raised.

So I think the United States is certainly leading the club, but I think anyone else is trying to adhere to mitigation guidelines. But probably we're going to hear that that's not enough.

MR. JOHNSON: All right. Our next question is for Dr. Ailor. Historically, satellite and launch vehicle designers have been responsive to requests to curtail the release of large debris. They have been less responsive regarding small debris, for example, the Delta 4 Second Stage. How can we improve this situation?

DR. AILOR: I think what needs to be done and basically I said this in my talk [and that is to] basically verify or hold organizations accountable for these things. And the first thing you need to do is be looking for it. And so I would say that as data comes in from the tracking network that indicates some bad actors, that we ought to make those actors aware they're a problem and basically give them the light of day as been used in the past and can be used in the future to try to improve these things.

So as you say, the small debris is a problem, and I pointed that out. Large debris also can be. And as was pointed out earlier, there have been efforts made to not release lens covers and those types of things. And so people are being responsible, but it doesn't mean that the job is done yet.

MR. JOHNSON: Okay. Thank you.

Next question from the audience, Calculations discussed in the panel suggest no Iridium-Cosmos type collisions in LEO for ten years.

I'm not sure that's exactly what was said, but it's close.

Does the likelihood of collision expand rapidly after the first catastrophic collision, that is, do debris clouds rapidly propagate themselves, and how many collisions have to occur before this order of regime becomes very dangerous? DR. KLINKRAD: Yeah. Let me answer to that from an ESA perspective.

Now, we had the Chinese anti-satellite test, which was happening at 862 kilometers. We had the Cosmos-Iridium collision that was happening at 780-some kilometers. And we have our ESA satellites (inaudible) operating at basically 780 kilometers semi-synchronous.

And I can tell you that for our (inaudible) and [the] ERS [European Remote-sensing Satellite], the risk of catastrophic collisions with catalog objects has dramatically increased. Nowadays, about two-thirds of all that (inaudible) that we see are coming from the Iridium-Cosmos collision and from the Chinese anti-satellite test. So I think this to some extent might answer your question.


DR. AILOR: I would just say that if you were looking at some of the data on our charts when you look at it. I might say the models that we use, we basically found there were two to three collisions every ten years or so which seems to be the what most models predicting these days, but you can see the cost increases due to that, even the small debris and so forth at least over the short term doesn't manifest itself. I mean, there are ways of defending against that for the collision avoidance business. If you can track the objects, and you've got a maneuverable satellite, then you can avoid them.

But even [if] that doesn't, the effects of collision avoidance would only reduce the cost by say about 10 percent, the cost increase by about 10 percent.

So these collisions, that was one of the things we were particularly interested in is the fact that you're creating a large cloud of debris when you have a collision and we model that. And the effects over the short term are not huge even in a bad area.

MR. JOHNSON: I think this was for Dr. McKnight. What criteria do you suggest we use to formulate our definition of acceptable risk and develop subsequent risk mitigation strategies?

DR. McKNIGHT: Well, as I mentioned in my presentation, that's a really hard question because, you know, where is the pain going to be felt? And there are some people who believe that an unstable environment is a point we need to be concerned with, and I think that's not really critical because a non-stable, and you maybe have an operational risk to your satellites that's already too great for you to manage before you have an unstable environment.

I also talked about the probability of where space insurance is going to have an impact. I believe that everybody has their own pain. I think that's one of the real difficult problems is about the trigger.

So my feeling is that it takes some strong action on a policy level right now to say we need to not let it get worse than it is now, and set some line in the sand whether it be semi-arbitrary to say we are not going to let it increase by a certain amount because every amount it does go up, it is going to have a cumulative effect on operational impact.

I do want to comment just back on that last question because it kind of wraps into this is we actually don't know too much about when the next collision is going to occur. Let's be honest. I mean one of the things I think is really critical to understand is we have a lot of laws that say lots of things. And when one event occurs, we change all the models around and say, wow, that was pretty bad. Now what do we say? As I mentioned Kosmos-2251 if we look at many of the models, that's not the one we thought would have collided.

An interesting analogy is go buy a lottery ticket. How many of you get a pool of people and go buy a hundred lottery tickets? You're more likely to win the lottery than that farmer who bought one ticket.

But I tell you, the most likely event is not usually the next event. So one of the things we all have to deal with is a certain amount of uncertainty, not because of lack of modeling, not because of a lack of space surveillance capabilities, not because of lack of communication, it's just the way it is right now until there's a number of events to really be able to model and sequence, we are going to be living with some uncertainty.

MR. WHITE: I would be willing to accept more risk if I had confidence I could tell the difference between an anomaly that was caused by debris and an anomaly caused by another reason. So as Darren said, the definition of risk differs depending who you are.

And back on the previous question, also on that MVSAT was launched before the voluntary guidelines were in place, so MVSAT's not going to de-orbited. It's in that 790-kilometer orbit that's very congested. So it's another candidate for causing a large amount of debris in case of a collision.

MR. JOHNSON: Okay. This next question is going to pit Dr. Ailor against Dr. McKnight here. Giving the seemingly low cost impacts of debris presented by Dr. Ailor, is there really a cost business case to be made for debris removal program as proposed by Dr. McKnight?

MR. WHITE: I think that's sort of the question that he was trying to raise. When does the business case present itself?

A couple things we might look for would be when the insurance people decide there's an issue there relative [enough] that they need to include in their insurance programs things for debris mitigation, possible debris impact.

For example, if an operator is doing a good job of avoiding collisions, should that reduce the insurance premium even if the spacecraft is made more robust should that do that?

But at the present time, if you talk to the insurance community, they don't include risks from debris in the premiums, so that will be an indicator I think.

And again, at the present time the challenge is going to be who is going to pay for this? If you talk to an operator right now, he'll tell you what are the risks to my spacecraft? And you'll basically say, well, the risks are small if you look at all the data. Then why should I be taxed to do that?

Although there are programs, there are some people who have suggested that there be a pool of funds set up like an insurance policy that would say if you've got a spacecraft in a particular orbit and the requirements are that you de-orbit it, and you're not going to de-orbit it, then the insurance would basically pay the cost of doing that.

But it also says maybe one role that government needs to take right now is to develop some of these technologies we've talked about [and] about how to remove these things, tethers and things and (inaudible) altitudes, for example, and do the research that would lead to the point where we actually have some confidence in our ability to remove debris. DR. McKNIGHT: [I don't want to] disappoint the person who asked the question and not disagree with Bill but go down in a little more detail. When you talked about the space insurance, I specifically took a look at space insurance because if you look in the region of around 800-kilometer altitude north orbit, the probability of collision, annual probability of collision looking down to 1 centimeter which would be mission terminating is about 8 times 10 to minus 3. If you double that, that's about 1.6 percent.

1.5 percent is the number right now the space insurance folks insure for after the first year on orbit. So if the collision asks for a mission terminating event, goes over 1.5 percent, they are going to charge you more money if you want space insurance. So we're not that far away from that, from a doubling of the mission terminating collision hazards.

So what's interesting is the models, again, I don't mean to poke at the models from aerospace, but any models that say it's going to happen this number of time it's the average. And speaking as a physics professor, which I was, that is sometimes often useless. It's high half of the time and it's low half the time.

Unfortunately, in this business we like to deal with the mean because it's a good number to understand. But the mean isn't really what's going to happen most of the time until we have a lot of space systems events.

That's why the (inaudible) on distribution that we use but never like to say those words, right, it sounds very technical. It's called the law of our events. That's why they call it that. They don't happen any more often, we're not going to have a good understanding.

So I just [said] that Bill and I completely agree, but I think numbers we look [at] specifically and -- how many have read the book Black Swan? Show of hands. Black Swan? Excellent. There are some intellectual powerhouses out there. That's a really important book to read because it helps you understand some of these technical issues about probability.

Sometimes you look really brilliant after events occur, and sometimes we need to make sure we're honest with ourselves before the events occur how well we could predict it.

MR. JOHNSON: Thank you. Related question, it was said that choosing objects to clear was difficult. Do you see improvements in measurements like for the space fence or modeling overcoming this? Heiner?

DR. KLINKRAD: Could you repeat?

MR. JOHNSON: It says objects to clear was difficult. Do you ever see improving measurement in modeling overcoming this?

DR.KLINKRAD: If you look into these charts that were presented earlier, of course there are very distinct inclination altitude bins, 72 degrees, 850, 800 kilometers where you have very high concentrations of mass which are sort of reachable if you try to remove them by means of removal missions that you launch into this orbit region.

And of course, if you remove big masses, that's the best way of reducing risk because mass is really what keeps the mechanism going and what's ultimately merging into what's called the Kessler Syndrome after Don Kessler where you have a runaway situation. But fragments are generated from collisions, and these fragments are large enough to cause another catastrophic collision. That's ending in an (inaudible) process. And I think our long-term environment models predict that we have (inaudible) 40-such collisions in the next 100 years.

So coming back to the question, I would say there are some orbit regions where one would have an easier situation of removing mass and being more efficient than other orbit regimes.

But as I mentioned before, the one that I was sort of singling out is one that almost exclusively populated by Russian payloads and rocket bodies. So there may be other obstacles to remove them.

DR. AILOR: I was going to say basically talking about the measurement side. On our study and most of the studies these days look at this idea of missing the tract objects which are 10 centimeters and larger. But as you know, the number of objects that could actually kill us on satellite are much larger than that, maybe a factor of 30 times.

So the idea of getting better data on these objects, in other words, tracking more objects and smaller objects might be something that could have some real benefit in the long term. DR. KLINKRAD: Maybe I should add to that. It was asked if data can help improve the situation, and I think we see this emerging with the initiative by JSpOC [Joint Space Operations Center] who submit the conjunctive summary message to anyone who is operating a space craft and who is signing up to that space craft Web page.

The accuracy and the extent of information they provide enables basically any operator today to do evasive maneuvers with any norm catalog object and do this with a very good reliability because the orbit precision is really very good.

We had encountered such an experience earlier this year when in January 21 our (inaudible) had a fly-by by a Chinese CZ-2 upper stage at an orbital distance less than 50 meters of which less than 20 was in the critical radial direction. And the CSM message that informed us was confirmed later from German radar data, and we made sure we got out of the way.

So I think data helps us get out of the situation. However, maneuverable space craft, that's just 5 percent of the catalog, so it does not remedy the overall risk.

DR. AILOR: Let me say one more thing. If you actually did increase the catalog by tracking smaller objects, that makes the collision conjunction assessment business even harder because the tools have to be able to handle these large numbers of objects.

Right now, we have 22,000 or something like that. Multiply that by a factor of ten, say, the computer tools and so forth are going to be more substantial.

And of course, from an operator's perspective, operators don't want to be dancing all over the sky having to duck things, so they'd like to have their predictions be as accurate as possible. I think your point is pretty good about it.

MR. JOHNSON: We want to take a question from the floor. General Chilton?

GEN. CHILTON: For those of you who are technically challenged like me and didn't bring your Blackberry, don't hesitate to raise your hand. I'm reminded when we started the Blackberry Q and A two years ago nobody texted in. Everybody raised their hand. Now we've gone to the other extreme.

So if I could lead off with a question, could you maybe review for us what the disposal criteria are that everyone has agreed to for particularly helio, end of life criteria, but also I'd be interested in MEO and GEO.

And then the question is do we have it right given if you look at the mass as something we'd like to control and not give more weight, if you will, more opportunities for collision in LEO, is our criteria good enough that would allow us to stabilize where we are as we start considering maybe removal activities or de-boost activities in the future? Thank you.

MR. JOHNSON: To answer the question first about what are the current guidelines, for those of you who may not be familiar, spacecraft and upper stages which operate in low earth orbit, that's below 2000 kilometers.

Then the guidelines say at the end of your mission, your mission may be a year long. It may be five years long or twenty years long. At the end of mission, a clock starts and you've got 25 years to come out, however you want to do that.

If you're, for example, operating below 600 kilometers you probably don't have to do anything. You'll come out naturally. If you're at 800 kilometers or 850 like the DMSP [Defense Meteorological Satellite Program], what you need to do is lower your (inaudible) down to some value, maybe 500 kilometers, a little bit lower to take advantage of natural drag to get you out within 25 years.

Now NASA came up with that recommendation back in the early '90s. We have re-verified or revalidated it several times recently, and 25 years still seems to be the right number.

However, we did go one step further at least at NASA, this has not been nationally or internationally accepted. We now say 25 years is fine, but there's also got to be [an] upper limit. We were looking at the fact that longevity of the larger spacecraft in LEO continues to increase. This is a good thing. This is not true for small sat[ellites] and nanosats and picosats. They typically last six months or a year.

But the larger spacecraft like the DMSP or something is lasting longer. So if you have an operational life of 20 years and then you've got 25 years more to get out of the environment, we found that really is starting to stress the environment.

So within NASA we now have a new amendment we adopted a couple years ago that says you've got 25 years after intermission, but you have a maximum of 30 years. You cannot be in LEO longer than 30 years. So if you're going to operate for 15, you've only got 15 years after that to come down.

You have to obviously think about that in advance. You've got to have substantial propulsion capability or drag augmentation device or some other technique to get you out within that allotted time. Eventually we may convince our European and other international colleagues that this is perhaps the way to go.

For GEO, the guideline is simply at the end of mission -- however long it may be, the guideline is to boost up to what we call a safe disposal orbit, which you can calculate but in general is about 300 kilometers above GEO.

Now, is that a long-term solution? No. All you're doing is moving everything up 300 kilometers. But it turns out people don't just go up 300 kilometers. One satellite will go up 300 kilometers, another will satellite will go 350, 400, 450. You'll be surprised that some of the spacecraft really do have a lot of propulsion capability at the end of mission. Remember, it takes very little propellant to go a great distance when you're in GEO already.

So it turns out the so-called disposal orbit in GEO is really not an orbit. It's a very large region. So the spatial density, that concentration of derelict rocket bodies and spacecraft above GEO is very sparse. So we can continue to do that for actually many decades before we have to come up with a more sophisticated solution.

The answer to the last part, in MEO there really is no guideline at all. We've looked at that. Very few systems operate in MEO. Obviously exceptions are the navigation satellites. We have GPS and GLONASS and Galileo and the new Chinese (inaudible) constellation which are all about 1,000 kilometers apart which is actually very convenient.

Unfortunately the disposal orbit of one constellation sometimes can intersect the operational orbit of another. So there is some work that these constellations need to do among themselves, but at this point we don't think there is a requirement for an international guideline.

I hope I answered all your questions, General. Anybody else like to say anything?

These are all anonymous, and they have to give their name if they stand up. The next question we have here is vent boosters present a problem it seems in the addressable term. What's your opinion of the effectiveness of drag devices to speed reentry?

I'll give you the classic NASA answer. Well, it's an okay idea, but the problem is to increase drag you increase cross-sectional area. And when you increase cross-sectional area, you increase your probability of collision. And in fact, it's a one for one.

The only thing that sometimes works in your favor is if your drag augmentation device, whether it's a balloon or sail or something, is normally much lower mass by definition so you can carry it with you. And so a collision with a low mass balloon and a derelict spacecraft rocket body might not be quite as disastrous as a body-to-body contact. But it turns out it's probably not going to be a good day either.

So drag augmentation devices may be a good solution for some, but a real problem is not future launches because we have other options. Our real problem is the resident space object which in some areas as we already talked about is already unstable. We know these collisions would occur even if we quit launching anything.

So we need to look not only at missions that have yet to come, but what do we do about the debris populations which are already there? Darren?

DR. McKNIGHT: One quick comment. I just finished working on a DARPA [Defense Advanced Research Projects Agency] study that looked at debris removal options, and for low earth orbit electrodynamic tether is actually an interesting object. Same problem if the object's already up there, it's hard to get the tether on there. But from the point of view of area to mass, collision hazard and how quickly things can be brought down, how flexible it can be used to remove objects, it was a fairly good option beyond drag augmentation.

DR. AILOR: I was going to say not relative to launch stages and things, but you hear a lot about or you're hearing more about cube sats, these four-by-four-by-four-inch satellites that are being used by universities and others that are sort of check payloads that are carried into orbit and just released.

And that's another one where these guys are at the very threshold of being tracked in the first place. And so doing some drag augmentation where you could actually increase the trafficability of it might not be a bad thing.

And secondly, the idea of bringing those things down too because they're also hazard for larger satellites, that needs to be considered. So again it's a drag augmentation, and those types of things as it may be developing some standard package they can carry would be a reasonable thing to consider.

MR. JOHNSON: Okay. Next question we have is who in U.S. government has mission responsibility in budget, end budget for space debris removal? I could answer that, but the president in the new space policy which General Chilton mentioned earlier this morning directed both the Secretary of Defense and the NASA administrator to start devoting research and development into debris removal concepts.

So we are both doing that, both organizations. We're just getting started obviously since the directive only came out in June. But right now no U.S. government agency, be it NASA or DoD or anyone else, has a actual responsibility to start removing debris. We're not quite there yet.

As I think Darren alluded to, there are technical challenges, there are financial challenges. NASA and DARPA cosponsored a debris removal conference 11 months ago in the Washington area, [and] had international participation. I think Dr. Klinkrad was at the conference. [There were] lots of good ideas. Maybe not all of them are viable. So we need to separate the weak from the chaff, and we're in that process right now.

And of course there are issues. There are concepts that are good for small debris. There are other concepts which were more appropriate for larger debris.

So no one has the responsibility just yet. I think as we get smarter, we'll get further direction from up high, and there will be some assignment of responsibility.

But in reality this is going to have to be an international activity. United States is not responsible for the current environment. Only about a third of the objects currently cataloged belong to the United States, so we can't go clean up the environment. We can't keep it clean by ourselves. This will clearly be an international effort.

So once we find solutions which are both technically and financially compatible. Then we need to have to go to the international community and see if we can't make a truly global undertaking.

Next question: Is there a legal issue regarding who owns the debris and who has the right to remove it? What is meant by holding accountable those who created debris? [Are there] any lawyers on the panel here?

I can take this as well. We talked about this a lot in the United Nations. In the Committee on the Peaceful Uses of Outer Space, COPUOS, there are two subcommittees: There's a scientific and technical subcommittee where virtually all the work has been done on space debris today, and there's a legal subcommittee where we worked very hard to keep it out of the lawyer's hands.

The Outerspace Treaty which was written in 1967 basically says if you put it up you own it for perpetuity. It's not like the law of the sea where if you abandon something anyone can go salvage it. So there are some issues associated with having the legal authority to go up [there] and remove a piece of debris which is not your own. So we -- we have to address that.

I think Dr. Klinkrad alluded to that where a lot of the most threatening debris actually is Russian, former Soviet origin. So we need to work with our Russian colleagues on how to remove that debris. If not by them, at least with their permission. Bill?

DR. AILOR: I just want to say some of the problems here. The hard problems aren't just technical. There are these legal issues as well, and I think one thing that can help move the removal process along would be to identify and work the problems with certain pieces of debris, for example, to identify some where the process is in place for shifting the liability, if you will, from the owner nation to an entity that wants to take responsibility for removing that.

But again, those are the kind of things where if you were going to do something like I say X PRIZE or something like that for debris removal concepts, some ideas like that might help move those along.

DR. KLINKRAD: I think what an obstacle to removal of mass from orbit is is that you're not compelled to do it. There is no legal requirement to take the things out of the way because the lawyers, somebody could claim that an intact satellite has damaged its piece of debris. It can work that way.

But you start to become liable when you de-orbit your spacecraft (inaudible) upper stage because then a fairly large fraction might survive to ground impact, so typically like 20 to 40 percent of large structures of the massive large structures is going to impact.

And if that happens, then there are treaties by the United Nations that make you liable of any consequences as you might have noticed for all the reentry of Kosmos-954 when it fell down over Canada and the Great Lakes area.

MR. JOHNSON: Still no questions from the floor? Okay [Here's one]. What do you foresee as the impact on LEO debris from the next solar maximum? That actually is a very good question, and I guess this will be my fourth solar maximum that I've had to deal with.

In general it's very good. You can get a lot of debris during solar max. It may be really rough on the guys at JSpOC, but it's a good thing. Unfortunately the prediction for this solar max is well below the average. So we do expect to see a washing out of a lot of the debris from the Chinese ASAT test and from the Iridium Cosmos collision. Right now only about 3 percent of both of those events debris have come out. But over the next five years or so, we should see a dramatic increase in that, again, which is a good thing.

DR. KLINKRAD: Maybe one can say that the current solar cycle is unprecedented I would say. It doesn't fit into any pattern. The start of its increased activity was not fitting into the phasing predictions, and the probable maximum is way below anything we've seen in the recent past. So the question is really are we going to have a maximum?

MR. JOHNSON: But with the current prediction, even though it's lower than we've seen for many decades, we will have a substantial effect because a lot of debris created during the Chinese ASAT test and the collision between the U.S. and Russian spacecraft are relatively lightweight. So they will come out with just a little bit of help from the sun.

All right, next question. At what point will space debris be a threat to launch vehicle delivery of future satellite missions to the desired orbit?

DR. McKNIGHT: I'll take the easy one. It's going to be a long, long time. Really when we're looking at the probability of collision, you're looking at the time of exposure, the spatial density, the relative velocity in the cross-sectional area and honestly for one trip up it's very, very small, and it's going to be a very long time. We're going to have much bigger problems before that's ever going to be an issue.

DR. AILOR: I just might say that the launch collision avoidance is done for certain high value systems so that is something that is factored into the process now for some cases.

MR. JOHNSON: But the good news and we're going to end this particular panel session on a positive note. It's not like the movies and actually what was the most recent animated one? WALL E. Thank you. It's not like that. There's not going to be so much debris you can't launch. Now, what happens to your spacecraft after you get in orbit may be something else.

I'd like to thank our panelists. I think we've had a very interesting exchange. We appreciate all the questions. Please continue to do this throughout the two days of the symposium, and thank you for your attention.