July 23, 2002 NEA 2002 MN and a U.S. Senate Roundtable Recently asteroid 2002 MN passed within one-fourth the distance to the Moon, inspiring wide news coverage and a U.S. Senate Roundtable on the impact hazard. For 6 stories, read more &.
(1) NEWS STORY: ON ALERT FOR ASTEROIDS By David Ballingrud, St Petersburg Times, Florida, 8 July 2002 If this were an old sci-fi movie, now would be the time for a somber gathering of the world's scientists to consider what to do about the approaching menace from outer space. Outlandish ideas would be suggested and rejected. A plan would emerge -- risky and with limited prospects for success -- but the only option available to a desperate world. In the real world, Earth is not menaced by anything in outer space -- at least so far as we know. But many scientists have developed an increasing sense of urgency about the threat posed by asteroids, if only in a cosmic time frame. Just last month, an asteroid the size of a football field missed earth by a mere 74,000 miles -- about one-third the distance to the moon. And we didn't even see it until it had passed us. At summer's end, NASA will conduct a workshop to try to figure out what we could do if we spotted a comet or asteroid on a collision course with our planet. "We're a little like cavemen getting together to decide what to do about a mysterious threat like forest fires," said Dan Scheeres, a professor of aerospace engineering. But before a specific plan can be developed, before decisions can be made, "we need to understand asteroids better; we need to do basic science so we can talk intelligently about what to do." Lucy McFadden, a member of the NASA team planning a mission to a comet in 2004, said scientists feel different degrees of urgency. "There's not the kind of urgency such as I'm concerned about my daughter flying into Dallas-Fort Worth in the rain. "But we can't predict the "when' or the "if' with asteroids so we can't ignore the issue either. "We need to find out what we need to know." Over the eons, the earth has had numerous run-ins with asteroids. A crater near Winslow, Ariz., caused by a relatively small asteroid, is about 4,000 feet across. In 1908, an asteroid flattened 800 acres of forest in Siberia. An asteroid crashing into Earth may have ended the reign of the dinosaurs millions of years ago. Worries about an asteroid collision with Earth have grown in part because better detection has revealed how many close calls our planet has had. The close call June 14 with the football-field sized asteroid was not detected till three days after it passed. Named 2002 MN, the object probably was large enough to have caused the kind of devastation Siberia experienced in 1908. On March 8, asteroid 2002 EM7 passed within about 288,000 miles of Earth. Like the June asteroid, it came from the "blind spot" near the sun and was not detected until several days after it passed. This is no cause for "doom and gloom," writes NASA asteroid expert David Morrison. Both were detected long before they threatened Earth, he said. "It makes no difference if an (asteroid) is discovered on approach or departure from the vicinity of the Earth," he said. "Objects in blind spots will be missed until they move into a more favorable geometry, sometimes within a few days, otherwise usually within a few years. Both of these asteroids were successfully found." Asteroids are relatively small, rocky bodies orbiting the sun like planets. There are many thousands of them in the so-called "asteroid belt" beyond the orbit of Mars. Some are enormous, hundreds of miles in diameter; some 30 feet across, or even smaller. Most asteroids stay put in the belt, but from time to time one gets loose -- perhaps jarred free by a collision with another asteroid, or pulled out by the gravitational tug from nearby Jupiter. Earth's atmosphere protects the surface from most small asteroids, also called meteorites when seen from Earth. They burn up before they strike the ground. Larger ones, though, could pose a threat. NASA researchers have found more than 350 near-Earth asteroids more than a half-mile in diameter. From this, they estimate anywhere from 500 to 1,000 similar-sized objects could be spinning around the solar system. None has an orbit that will bring it anywhere near Earth in the near future. But scientists haven't found them all. Then there are the surprise flybys, including those from March and June. If one were headed for a collision with Earth, mankind's only course would be to try to change its path somehow, or destroy it. The workshop scheduled for September, "Scientific Requirements for Mitigation of Hazardous Comets and Asteroids," mostly will deal with the science of asteroids. Some members of the military will be present. "There's a common misconception that we're going to sit around with a bunch of arms experts and discuss how to blow an asteroid up," said McFadden, a University of Maryland research professor. "But we may not ever even have to consider something like that." A smorgasbord of topics are on the agenda. Scheeres, who was on a NASA team that flew an unmanned spacecraft to an asteroid in February of last year, will talk about "Fancy maneuvers: Hovering, Hopping and Tethering." He explained: "I've been studying how to control a spacecraft when it is next to or close to an asteroid's surface." Because gravity is light and erratic, hovering near an asteroid will be difficult. Some have suggested a tether might do the trick. Putting a rover on the surface to gather soil samples will be a headache, too, because the light gravity might mean a rover's wheels would not gain traction. "So the most efficient way to move a rover would be to have it hop," Scheeres said, "to jump up and come down somewhere else to take more samples." "We'll have a lot of interests represented, a lot of mind-sets," said workshop organizer Erik Asphaug of the University of California at Santa Cruz. "It will be fun." Scheeres, from the University of Michigan, said more people are paying attention. "I think there is a change in awareness taking place. I think it began when Shoemaker-Levy hit Jupiter almost a decade ago." From July 16 through July 22, 1994, pieces of Comet Shoemaker-Levy slammed into Jupiter in a spectacular, much photographed collision -- the first between two solar bodies ever to be observed. "That single event," Scheeres said, "showed people that the solar system is a very dynamic place, that catastrophic events are still happening." © Copyright St. Petersburg Times. All rights reserved.
(2) PROTECTING THE PLANET: SPACE.COM Q&A WITH ASTEROID HUNTER DAVID MORRISON By Robert Roy Britt, space.com, 02 July 2002 David Morrison figures his long effort to keep the world safe from asteroids has been very successful. "In 11 years of protecting the planet, not a single human has been killed," he pointed out to me recently. Morrison is of course not the only person working to save Earth from potentially deadly space rocks. But the sometimes outspoken, always affable space scientist at NASA's Ames Research Center was one of the first people involved. In the early 1990s, he chaired a committee that generated the Spaceguard Survey Report, which advised NASA and Congress to search for and determine the paths of all Near Earth Objects (NEOs), asteroids and comets larger than 1 kilometer (0.62 miles) that roam the region of space also occupied by Earth. Morrison is a moderating voice in a field whose most vocal members are sometimes accused of attempting to frighten the public. That doesn't mean he thinks we're entirely safe. "The impact hazard is real, and it is of a magnitude at least as great as many other natural hazards," Morrison testified before Congress in 1993. "Over long time spans, impact catastrophes are inevitable. What happened to the dinosaurs can happen to us." What happened to the dinosaurs, and many other species of their time, was that they were annihilated by the global effects of an impact by an asteroid the size of a city. Sixty-five million years later, the Spaceguard recommendations were adopted, and today a worldwide effort funded partly by NASA and involving several institutions has found about half of the roughly 1,000 large NEOs thought to exist. Today, Morrison chairs the working group on NEOs in the International Astronomical Union, a volunteer position. He also maintains a comprehensive Web page on the subject. He typifies the pieced-together nature of the overall effort to guard the planet, one dominated by part-time contributors, arguably underfunded programs and a league of amateurs who do much of the grunt work -- follow-up observations that help determine if a recently discovered NEO is on course to one day hit Earth. At a recent gathering of astrobiologists, where Morrison wore the hat he gets paid for as Senior Scientist at the NASA Astrobiology Institute, he told me he views his asteroid watch as a hobby. I sat down with the Harvard Ph.D. to discuss the often controversial state of his part-time industry, the search for NEOs and the question of what to do if we find one with our name on it. -------------------------------- SPACE.com: Why are asteroid impacts a hobby for you? David Morrison: Several of us who have been interested for 10 years or so in the question of whether Earth is at hazard from asteroids and what's the right way to handle this issue have, for the most part, not received any direct funding from NASA to do it. It is not our primary job. But I think it's fascinating science and an important policy issue, so I put some time into it. SPACE.com: In the search for potentially threatening asteroids, what are we doing right? DM: We are efficiently finding the NEOs 1 kilometer [0.62 miles] or larger in size, which is a range that includes anything that is a global threat; that is, that could produce a global environmental catastrophe. We're more than halfway there. In fact, we have reduced the risk from an unexpected asteroid strike by about a factor of two. We reduced this risk without actually having to move anything. We do not expect any of the remaining [undiscovered] objects to be on a collision course with Earth. It would be bad luck if they were. On the other hand, if one is on a collision course, we want to know it. I think probably by 2008, when we have 90 percent of the larger NEOs catalogued, we will have concluded that none of them is a risk. But the possibility that we're unlucky, that an impact might create a truly global catastrophe and kill hundreds of millions of people, motivates us to carry out the search and be concerned about this issue even though it's a low probability risk. We deal with such things in ordinary life. For instance, when you buy fire insurance on your house, you actually don't expect your house to burn down. Most people go through their entire lives without having a major fire in their house. But you still buy the insurance. SPACE.com: We always hear that eventually, Earth will be hit again, statistically speaking. When? DM: A large impact is not something we expect to happen in our lifetime, in our childrens' lifetime, or even our grandchildrens' lifetime. It would be very bad luck if it did happen. But it could happen at any time. Ultimately, the reason we can deal with this scientifically is that it's not a statistical random chance. Somebody doesn't throw the die every year and decide if we're going to be hit that year. If there's an object out there that's going to hit us, say, in the next thousand years, it is already on a collision course. So it can be found, its course can be determined. Asteroids don't change orbits capriciously, as is often depicted by Hollywood. SPACE.com: Scientists and journalist constantly spout statistics about the asteroid threat. But in some sense the statistics are meaningless and may fuel some apathy among the general public. DM: That's right. The issue is not one of refining the statistics. It's not whether it's a 1-in-a-million or a 1-in-2-million chance that it will happen this year. It's an absolute thing. Will it or won't it happen? SPACE.com: What are we doing wrong in the NEO search? DM: We have not yet seriously considered what the next step should be. In 2008, when we have found 90 percent of these larger NEOs, do we just keep going to get 95 percent or 99 percent? [The final few will be the toughest to track down, experts say.] Do we try to segue into larger telescopes so we can find fainter [and thus smaller] objects, those a few hundred meters in size that could produce a tsunami and wipe out the coast around an ocean basin? We have been so focused on the immediate, higher-priority problem that there hasn't been much thought given yet to the next level. One group that has considered the next level is in the United Kingdom. The UK NEO Task Force recommended two years ago that we set another goal, that we raise the bar and focus on [smaller and thus dimmer] 300-meter [roughly equal to three football fields] objects, which requires a new generation of search telescopes. In the United States, we haven't done anything either to build such telescopes or even to plan for it. SPACE.com: Is this just because the plate is full? DM: It's partly because the plate is full. It depends on whether you think of the asteroid search funds as a fixed sum of money. If we are level-funded at $3.5 million a year, which is what NASA is now investing, then that pretty well all goes to the current search. On the other hand, the National Research Council has recommended that the U.S. build a Large-aperture Synoptic Survey Telescope (LSST), a new instrument that could in fact do the survey down to 300 meters, by itself, as well as a lot of other good astronomy. Astronomers at the National Science Foundation are looking at that. SPACE.com: If I promised you a billion dollars a year, where would you put it? DM: I would not know how to spend a billion dollars a year on asteroids. SPACE.com: But we keep hearing that it will be very expensive to find smaller asteroids. DM: The smaller you go, the more expensive it is. This LSST has been estimated at about $180 million to build plus roughly $20 million per year to operate. So if you found that kind of money you could build such a telescope. SPACE.com: So if I gave you a billion, you wouldn't put it all into NEO research? DM: That's right. I wouldn't. Because I don't think it could be justified. But there is another perspective that has to be seriously thought about. We always say that if we found an NEO on a collision course, we have the technology -- in principle -- to deflect it. But of course we've never actually done it. We've never done any experiments. The alternate perspective says we should develop and test such deflection technology, that we should take an innocent asteroid that's not on a collision course and try sending a spacecraft to deflect it. SPACE.com: A billion might come in handy for that. DM: Yeah, it would [laughs]. The space program doesn't normally operate this way, but you could set out a challenge, some sort of international prize for the first group that changes the velocity of an asteroid by 2 centimeters per second [0.04 mph]. They could do it with an explosion, nuclear or non-nuclear, by putting a solar sail on it, or whatever. [A minor velocity change would induce a change in trajectory as an asteroid interacted gravitationally with the Sun, planets and other objects, putting it on an entirely new course.] SPACE.com: Some vocal members of the NEO community are going to read this and say, "Here's the NASA voice again saying we're on track, we just have to worry about the big ones. But it's the small sucker punches we need to worry about, and we need to worry about them now." What do you say to those people? DM: I'm not sure what point they're trying to make, because they speak as though with a small one we're likely to have less warning. I don't understand that argument. Right now we catch any 1-kilometer or larger object that comes within a big volume of space -- within about 100 million kilometers [62 million miles] of Earth. To carry out a complete survey of 300-kilometer objects, you need to look at the same volume of space but detect fainter objects. The survey procedures and warning times are about the same. SPACE.com: But it's easier for a small asteroid to escape detection, and there are more of them. So the chances are greater we'll get surprised by one, at least until they have been catalogued. DM: That's right. But in that case you'll *really* be surprised. The first you'll know of it is when you see the sky light up as it enters the atmosphere. If we haven't started building new telescopes within the next year or two, they won't be ready to take over in 2008. So now is the time to go on to the next step. But I think the search philosophy remains the same. Whether it's big ones or little ones, you carry out a survey, make a catalogue, calculate orbits, and predict future encounters with the Earth. We can predict the impact of a 100-meter or 50-meter object just as far in advance as a kilometer object, once we find it. SPACE.com: Aside from this conversation, you're wearing your astrobiology hat today. In your mind, is there any connection between asteroids and astrobiology? DM: Yes, certainly. Astrobiology is more than just a search for life. Astrobiology is an effort to understand life as a planetary or astronomical phenomenon. We look at the long-term interaction of life, the environment, and the planet. In that context, asteroid impacts are very important. We don't know how important, but it's at least possible that on Earth, impacts have been a major driver in evolution, because by producing mass extinctions, you essentially open up a huge number of ecological niches. After a mass extinction the rate of speciation is huge, a very quick radiation of new species. Impacts and their environmental effects, both past and future, are one of the elements of astrobiology. To me, realizing that the end-Cretaceous extinction [dinosaurs, et al.] is due to an impact is illustrative of how fragile the biosphere is. That's a tiny impact compared to the planet as a whole. It's not enough to change orbit, or rotation, or magnetic fields or anything, yet it produced an ecological catastrophe, redirecting the course of biological evolution on our planet. It is trite but true: Without the end-Cretaceous impact, humans would not be here.
(3) IMPRESSIONS OF THE U.S. SENATE ROUNDTABLE ON JULY 10 David Morrison On July 10 a round-table discussion of the asteroid impact threat was held in one of the office buildings of the U.S. Senate. This discussion was sponsored by various pro-space organizations and did not have official status, as would a Congressional hearing. However, it included presentations by Representative Dana Rohrabacher, Chair of the House Space Subcommittee, Colleen Hartman, NASA Director of Solar System Exploration, and General Pete Worden, Deputy Director of the U.S. Space Command, so it was in fact a rather high-profile event Following is a listing of the program, my own summary based on the webcast (I did not attend in person). ------------------------------------------------------------ The Asteroid Threat: Identification and Mitigation Strategies (July 10, 2002) PRIMARY SPEAKERS
Marc Schlather, President, ProSpace
Colleen Hartman, Director, NASA Solar System Exploration Division
Dana Rohrabacher, Chair of House Space and Aeronautics Subcommittee
Brian Marsden, Director, Minor Planet Center, Harvard-Smithsonian CFA
Simon P. Worden, Brig Gen USAF, U.S. Space Command
Lee Valentine, Executive Vice President, Space Studies Institute
Evan Seamone, Articles Editor, Iowa Law Review OTHER PARTICIPANTS Richard Godwin, Executive Director, The Watch
Warren Greczyn, ANSER (AIAA representative)
Thomas Morgan, NASA Minor Planets Program Scientist
Rick Tumlinson, Executive Director, F.I.N.D.S.
------------------------------------------------------------- Schlachter introduced the topic and laid out the general issues of the NEO impact hazard, emphasizing that this is a real threat and deserves serious government consideration. Hartman spoke on "NASA's Near Earth Observations Program". She gave an overview of the impact hazard and the NASA program, which she said now receives approximately $4M per year. She explained the Spaceguard goal, the reason for dealing first with NEAs that are capable of causing global catastrophes, and the primarily NASA interest in science-driven investigations of NEAs. She noted that we will obtain long-lead-time warning as a result of a Spaceguard-type survey. Rohrabacher affirmed his strong interest in the NEO hazard issue and also in the development of dual-use space technologies that might allow DoD missile defense technologies to be used for planetary defense against asteroids. He derided global warming, stating that if only a small fraction of the funds spent on global warming were instead diverted to the impact hazard that would be a great thing. He feels that NEAs can be an opportunity, as well as a threat, and that we should be looking for ways to use NEAs as space resources. Marsden spoke on "Tracking Near Earth Objects In Practice", describing the work of the Minor Planet Center (MPC), including display of various data products (mostly dealing with the recent example of NEA 2002MN). He implied that he did not fully agree with the Spaceguard philosophy with respect to impactors smaller than 1 km, suggesting that as we move to smaller NEAs we are likely to find objects with much less warning, perhaps as little as a few days. He also called for a southern-hemisphere site to find objects that "come up at us from the south". He was the first on the panel to explicitly raise fear of a short-warning impact. Morgan responded to Marsden in later discussion by speaking favorably of international cooperation. He mentioned the IAU review procedure, emphasizing the value of ensuring that predictions are robust before releasing information. He was the only speaker to refer to issues of false warnings and general credibility of the prediction process. Worden spoke on "National Security Perspectives on the Asteroid Threat " (speaking for himself personally and not for the USAF). He began by noting the USAF observations of small (kiloton) atmospheric explosions and the potential of these to trigger a nuclear war in unstable areas of the globe. He suggested that the defense against NEAs be assigned to the USAF Space Command and that a coordinating and information office be set up at Cheyenne Mountain. As we move to dealing with smaller NEAs (down to 50m diameter) he stated that the new generation of ground-based USAF surveillance systems could find most of them within the next decade, but this will not happen unless the mission is specifically assigned to the USAF. See below for the full text of Wordens statement. Valentine discussed "Diversion and Mitigation Scenarios and Technologies", advocating a wide range of ideas from the immediate to the far future. He presented many options and did not try to prioritize them or estimate their costs. Seamone discussed "The Legal Basis for International Cooperation". He advocated establishing a system for dealing with NEA impact disasters within the framework of international law. He discussed international and legal issues in the context of the Skylab & Mir reentries, noting that more than 80 governments had in place plans in case Mir fragments fell on them. He suggested that under international law, it should be the first priority of all governments to take action to defend and protect their citizens against general environmental collapse, and this that is the kind of threat we face from NEAs. His position is discussed in detail under "NEOs and the Law" in this News Archive. Other discussion included mention by Greczyn of the new AIAA (American Institute of Aeronautics and Astronautics) position paper on planetary defense. This is summarized in Space News for July 1, 2002. Tumlinson presented an emotional appeal for action. He claimed that to the public, near misses like 2002MN are unacceptable -- as if there had actually been an impact and millions of casualties. He also asserted that it is unacceptable that we are finding some of these NEAs after closest approach rather than before. He compared defense against asteroids to defense against terrorists and proposed that asteroid defense be assigned to the new U.S. Office of Homeland Security. In final summaries, there were repeated calls for a coordinating body within the US government to deal with the threat, as suggested by Worden. Marsden asked for more funds for the MPC, addition of a southern search telescope, and formation of a coordination center so he will know to whom to report if a short-term threat is identified (e.g., "on a weekend"). NASA representatives Hartman and Morgan focused on the current search programs, affirming that NASA takes the issue seriously and is doing its job. Their emphasis was on peer-reviewed science, not the larger societal and mitigation issues raised by other speakers. Schlather as moderator ended on the note that we must act now -- with this kind of low probability threat we cannot wait (as we usually do) for an actual occurrence before taking action. ----------------------------------------------------------------- Further Comments on a Proposed Warning Center Several participants in the NEO Roundtable called for establishing a NEO coordination and warning center. It was not clear to me to me to what is meant by such a warning center. I think everyone can share Worden's concern about misidentification of meteors that hit the atmosphere and explode with kiloton-scale energies. I certainly support his proposal that this information be disseminated more widely and quickly. However, these are not what I call "warnings" -- they are timely reports on events that have already happened and been observed from space. The only warnings I know of would concern asteroids or comets discovered to be on possible impact trajectories. Over the past 6 years there have been several short-lived "warnings" of possible future impacts that were quickly withdrawn as new data and/or better orbital calculations became available. Today with multiple international centers for calculating orbits and improved data sharing, it is likely that there will be fewer such public warnings. As the NEA surveys increase in power, there will almost certainly be additional cases of newly-discovered NEAs that appear for a short time to have a possibility of colliding with the Earth. These will all be predictions for far in the future, probably at least several decades. Some will be reported in the press, but most will be quietly checked out and their orbits refined without the glare of publicity. Astronomers in several countries today have this computational capability. I therefore wonder what is the purpose of the proposed warning center, and just what sort of warnings it anticipates issuing? Perhaps it is worth repeating that none of the proposed surveys is designed to look for any NEA on its final plunge to collision with the Earth. The approach first articulated a decade ago is to survey the sky, discover NEAs, determine their orbits, and predict their future paths. Any potential impactor should be picked up decades (or more) in advance. We can do this because orbital dynamics is an exact science, and asteroids do not change orbits capriciously. This approach will apply as well to the smaller NEAs that are discovered in the future as it does to those being found today. "Warning" is a word that conveys the wrong impression: In my opinion, what we should be talking about are long-term predictions, based on a comprehensive survey of NEAs.
(4) GEN PETE WORDEN'S STATEMENT ON THE NEO THREAT Military Perspectives on the NEO Threat
Simon P. Worden, Brig General, USAF
Deputy Director for Operations, United States Space Command
July 10, 2002 The opinions and concepts expressed are those of the author and do not necessarily represent the position of the Department of Defense or the United States Space Command Introduction A few weeks ago the world almost saw a nuclear war. Pakistan and India were at full alert and poised for a large-scale war - which both sides appeared ready to escalate into nuclear war. The situation was defused - for now! Most of the world knew about this situation and watched and worried. But few know of an event over the Mediterranean in early June of this year that could have had a serious bearing on that outcome. U.S. early warning satellites detected a flash that indicated an energy release comparable to the Hiroshima burst. We see about 30 such bursts per year, but this one was one of the largest we've ever seen. The event was caused by the impact of a small asteroid - probably about 5-10 meters in diameter on the earth's atmosphere. Had you been situated on a vessel directly underneath the intensely bright flash would have been followed by a shock wave that would have rattled the entire ship and possibly caused minor damage. The event of this June caused little or no notice as far as we can tell. But had it occurred at the same latitude, but a few hours earlier, the result on human affairs might have been much worse. Imagine that the bright flash accompanied by a damaging shock wave had occurred over Delhi, India or Islamabad, Pakistan? Neither of those nations have the sophisticated sensors we do that can determine the difference between a natural NEO impact and a nuclear detonation. The resulting panic in the nuclear-armed and hair-trigger militaries there could have been the spark that would have ignited the nuclear horror we'd avoided for over a half-century. This situation alone should be sufficient to get the world to take notice of the threat of asteroid impact. The Threat I've just relayed the aspect of the near-earth objects (NEO) that should worry us all. As more and more nations acquire nuclear weapons - nations without the sophisticated controls and capabilities build up by the United States over the 40 years of Cold War - we must first and foremost ensure that the 30-odd impacts on the upper atmosphere are well understood by all to be just what they are. A few years ago those of us charged with protecting this nations vital space system, such as the Global Positioning System (GPS) became aware of another aspect of the NEO problem. This was the Leonid meteor storm. This particular storm occurs every 33 years. It is caused by the debris from a different type of NEO - a comet. When the earth passes through the path of a comet, it can encounter the dust thrown off by that comet through its progressive passes by the Sun. This dust is visible on the Earth as a spectacular meteor storm. But our satellites in space can experience the storm as a series of intensely damaging micrometeorite strikes. We know about many of these storms and we've figured out their parent comet sources. But there are some storms arising from comets that are too dim or spent for us to have seen that can produce "surprise" events. One of these meteor storms has the potential of knocking out some or even most of our earth-orbiting systems. If just one random satellite failure in a pager communications satellite a few years ago seriously disrupted our lives, imagine what losing dozens of satellites could do! Most people know of the Tunguska NEO strike in Siberia in 1908. An object probably less than 100 meters in diameter struck over Siberia releasing the equivalent energy of up to 10 megatons. It leveled a forest 50 miles across. But most people don't know that we have evidence of two other strikes during last Century. One occurred over the Amazon in the 1930s and another over central Asia in the 1940s. Had any of these struck over a populated area, thousands and perhaps hundreds of thousands might have perished. Experts now tell us that an even worse catastrophe that a land impact of a Tunguska-size event would be an ocean impact near a heavily populated shore. The resulting tidal wave could inundate shorelines for hundreds of miles and potentially kill millions. There are hundreds of thousands of objects the size of the Tunguska NEO that come near the earth. We know the orbits of but a handful. Finally, just about everyone knows of the "dinosaur killer" asteroids. These are those objects a few kilometers across that strike on timescales of tens of millions of years. While the prospect of such strikes grab people's attention - and make great catastrophe movies - too much focus on these events has in my opinion been counterproductive. In my organization, the Department of Defense, I have tried to raise our concern and interest in addressing the very real threats outlined above. However I get the predictable response. "General, if this threat only hits every 50 million years, I think we can focus our attention of more immediate threats!" In short the "giggle factor" in the professional scientific and national security community has meant that we have gotten little done on this problem. What Should We Do? First and foremost we must know when an objects strikes the earth exactly what it is and where it hit. Fortunately our early warning satellites already do a good job of this task. And our next generation system, the Space-Based Infrared System (SBIRS) will be even better. The primary difficulty here is that this data is also used for vital early warning purposes and its detailed performance is classified. However, in recent years the U.S. DoD has been working to provide extracts of this data to nations potentially under missile attack with cooperative programs known as "Shared Early Warning." Some data about asteroid strikes has also been released to the scientific community. Unfortunately this data takes several weeks to get released. Thus my first recommendation is that the United States DoD make provision to assess and release this data a soon as possible to all interested parties - exercising proper cautions of course to ensure that sensitive performance data is safeguarded. We have begun to scope what an NEO warning center might look like. We believe adding a modest number of people, probably less than 10 all told, to current early warning centers and supporting staffs within Cheyenne Mountain could accomplish this. A Natural Impact Warning Clearinghouse has been scoped to do this job. Perhaps the most urgent mid-term task has already been begun. This is the systematic observation and cataloguing of close to all potentially threatening NEOS. We are probably about halfway through cataloging "large" NEOS (greater than a kilometer in diameter). It's interesting to note that the most effective sensor has been the MIT Lincoln Lab LINEAR facility in New Mexico. This is a test bed for the next generation of military ground-based space surveillance sensors. But this ground-based system, however effective, can only really address the "large", highly unlikely threats. We find out every few weeks about "modest" asteroids a few hundred meters in diameter. These are often caught as they sail by the earth, often closer than the Moon, unnoticed until they have nearly passed. Most recently the object 2002MN had just this sort of near miss - this time only a few tens of thousands of kilometers from the earth! Moreover, ground-based systems such as LINEAR are unable to detect one of the potentially most damaging classes of objects, those such as comets that come at us from the direction of the sun. New space-surveillance systems capable of scanning the entire sky every few days are what's needed. New technologies for both space-based and ground based surveys of the entire space near the earth are available. These technologies could enable us to completely catalog and warn of objects as small as the Tunguska meteor (less than 100 meters in diameter). The LINEAR system is limited primarily by the size of its main optics - about 1 meter in diameter. By building a set of three-meter diameter telescopes equipped with new large-format CCD-devices, the entire sky could be scanned every few weeks. But more important the follow-up observations necessary to accurately define orbits, particularly for small objects could be done. The most promising systems for wide-area survey - particularly to observe close to the sun to see objects coming at up from that direction - are space-based surveillance systems. Today the only space-based space surveillance system is the DoD's "MSX" Satellite. This was a late 1990s missile defense test satellite and most of its sensors have now failed. However one small package weighing about 20 kg and called the "SBV" sensor is able to search and track satellites in Geosynchronous orbit using visible light. This has been a phenomenally successful mission having lowered the number of "lost" objects in GEO orbit by over a factor of two. MSX is not used for imaging asteroids, but a similar sensor could be. The Canadian Space Agency, in concert with the Canadian Department of National Defense is considering a "microsatellite" experiment with the entire satellite and payload weighing just kg. This Near-Earth Surveillance System (NESS) would track satellites in GEO orbit, as MSX does today. However, it would also be able to search the critical region near the sun for NEOs that would be missed by conventional surveys. The U.S. DoD is planning a constellation of somewhat larger satellites to perform our basic satellite-tracking mission. Today our ground-based radars and telescopes, and even MSX only track objects that we already know about. These systems are not true outer-space search instruments as the LINEAR system is. However, the future military space surveillance system would be able to search the entire sky. As an almost "free" byproduct it could also perform the NEO search mission. Corresponding, larger aperture ground based systems could then be used to follow up to get accurate orbits for the NEOs discovered by the space-based search satellites. Again, I believe there is considerable synergy between national security requirements related to man-made satellites and global security related to NEO impacts. Regardless of how well we know NEO orbits and how well we can predict their impacts the fact remains that today we have insufficient information to contemplate mitigating an impact. We do not know the internal structure of these objects. Indeed, we have reason to believe that many, if not most are more in the nature of "rubble piles" than coherent objects. This structure suggests that any effort to "push" or divert a NEO might simply fragment it - and perhaps turn a single dangerous asteroid into hundreds of objects that could damage a much larger area. What are needed are in-situ measurements across the many classes of NEOs, including both asteroids and comets. This is particularly the case of small (100meter) class objects of the type we would most likely be called upon to divert. Until recently missions to gather these data would have taken up to a decade to develop and launch and cost 100s of millions of dollars. However, with the rise of so-called "microsatellites" weighing between 50-200 kg and which are launchable as almost "free" auxiliary payloads on large commercial and other flights to GEO orbit, the situation looks much better. These missions can be prepared in one-two years for about $5-10M and launched for a few million dollars as an auxiliary payload. Such auxiliary accommodation is a standard feature on the European Ariane launched and should be, with proper attention, here in the United States on our new EELV launcher systems. With a capable microsatellite with several kilometers per second "delta-V" (maneuver capacity) launched into a GEO transfer orbit (the standard initial launch orbit for placing systems into GEO) the satellite could easily reach some NEOs and perform in-situ research. This could include sample return and direct impact to determine the internal structure and potential to physically move a small object. Indeed, NASA is planning several small satellite missions. The key point here, however, is that with missions costing $10M each, we can sample many types of objects in the next decade or so to gain a full understanding of the type of objects we face. There is an interesting concept to consider. If we can find the right small object in the right orbit we might be able to nudge it into an orbit "captured" by the earth. This would make a NEO a second natural satellite of earth. Indeed, there is at least one NEO that is close to being trapped by the Earth now, 2002 AA29. If such an object were more permanently in earth orbit it could not only be more closely studied but might form the basis for long-term commercial exploitation of space. Moreover, a very interesting next manned space flight mission after the Space Station would be to an asteroid, maybe even one we put into earth's gravity sphere. The key of each of these proposed actions on developing the ability to mitigate NEO impacts is that they are all items our national security community and we in the United States are likely to do for other reasons. If these efforts can be adapted to the NEO threat problem, this would add minimal additional expense. One of the most important aspects of NEO mitigation is often overlooked. Most experts prefer to focus on the glamorous "mitigation" technologies - diverting or destroying objects. In fact, as the military well knows the much harder part is what we call "command and control." Who will determine if a threat exists? Who will decide on the course of action? Who will direct the mission and determine when mission changes are to be made? Who will determine if the mission was successful? And there are hosts more. These command and control issues are those that the military has long struggled with. The NEO community has not faced this essential issue. Indeed, the United States Space Command has just completed a concept of operations for the first step in NEO mitigation - a Natural Impact Warning Clearinghouse. This operation is a command and control function. It would be able to catalog and provide credible warning information on future NEO impact problems as well as rapidly provide information on the nature of an impact. International Issues Much discussion has been expended suggesting that any NEO impact mitigation should be an international operation. I would respectfully disagree. International space programs such as the International Space Station fill many functions. An NEO mitigation program would have only one objective. In the latter case a single responsible nation and organization would have the best chance of a successful mission. Moreover, the nation responsible would not need to worry about giving up national security sensitive information and technology as it would build and control the entire mission itself. For as pointed out the means to identify threats and mitigate them overlap considerably with other national security objectives. It does, however make considerable sense that the data gathered from surveys and in-situ measurements be fully shared among all. This will maximize the possibility that the nation best positioned to perform a mitigation mission would come forward. One of the first tasks of the Natural Impact Warning Clearinghouse noted above would be to collect and provide a distribution point for such data. Summary NEO Mitigation is a topic whose time has come. Various aspects related to NEO impacts, including the possibility than an impact would be misidentified as a nuclear attack, are critical national and international security issues. The focus of NEO mitigation efforts - both in finding and tracking them and in exploring and moving some should shift to smaller objects. Not only are the near-term threats much more likely to come from these "small" objects (100 meters in diameter or so), but we might also be able to divert such objects without recourse to nuclear devices. After a suitable class of NEOs are found, microsatellite missions to fully explore and perhaps perform test divert operations should commence. The technologies for low-cost NEO missions exist today. The necessary command and control, sensor and space operations technologies and equipment are all "dual use" to the military. We have similar, and in some cases almost identical requirements. It thus stands to reason that strong military involvement and even lead in the decades ahead on NEO mitigation is in order. As the U.S. Government considers how to proceed on this critical issue, the major role that the military and the technologies it controls should be carefully integrated into our overall national work.
(5) NEWS STORY: HUNT FOR POTENTIALLY DEADLY ASTEROIDS UNDERFUNDED, U.S. PANEL SAYS Jason Bates, Space.com, 10 July 2002 WASHINGTON D.C. - The U.S. government should invest more money in tracking near-Earth objects that might threaten Earth, said members of a space roundtable on Capitol Hill Wednesday. While the Air Force is not tasked with tracking near-Earth objects, U.S. Air Force Brig. Gen. S. Pete Worden said such a mission would be appropriate for the service and an assignment could occur "in the next few years," he said. A warning center could be run by the Air Force and coordinate with non-military groups that currently track objects, Worden said during the roundtable, which was titled "The Asteroid Threat: Identification and Mitigation Strategies" and sponsored by an organization called ProSpace. Worden, deputy director of operations for U.S. Space Command, Peterson Air Force Base, Colo., was not attending the panel as an official representative of the U.S. Department of Defense. He has in the past spoken often about the need to widen the search for potentially threatening asteroids. Currently, NASA spends about $4 million per year on programs that track space objects larger than a kilometer in diameter (0.62 miles), said Colleen Hartman, director of NASA's Solar System Exploration Division. NASA, however, does not track objects the size of the recently discovered 2002 MN2, an object between 50-100 meters in diameter (roughly 50-100 yards) that passed within 75,000 miles of Earth in June, the panelists said. The rock was found three days after it flew by. Increased funding should be used to track these smaller objects as well, the panelists said. Some vocal advocates of increased asteroid monitoring around the globe have long called for similar changes, whether funded by NASA or some other agency or institution. If the U.S. government were to take a more active role in tracking all space objects, the Air Force could be responsible for tracking and cataloguing, while NASA could be responsible for scientific investigation, Worden said. Rep. Dana Rohrabacher (R-Calif.), chairman of the space and aeronautics subcommittee of the House Science Committee, said the potential danger to Earth from space objects is greater than that posed by global warming. He suggested that some of the money spent on global warming research could be used to fund more work on tracking space objects. Such funding could be used to first locate and track asteroids and comets, and later to find ways to defend Earth against the threats and eventually to use the space objects for the benefits of the Earth's population, Rohrbacher said. Other researchers in the past have suggested mining asteroids for valuable metals and minerals as one way to make them useful to humanity. Some have even suggested setting up small colonies on larger asteroids. Copyright 2002, Space.com
(6) NEWS STORY: EARLY WARNING CENTER FOR ASTEROIDS NEEDED, U.S. SPACE OFFICIAL SAYS Marc Selinger, Aerospace Daily, 11 July 2002 The Department of Defense should set up an early warning center so the information it collects about asteroids, comets and other near-Earth objects (NEOs) can quickly be shared with other countries, according to Air Force Brig. Gen. Simon "Pete" Worden, deputy director for operations at U.S. Space Command. Worden said July 10 at a Capitol Hill space round-table that a June incident involving an asteroid over the Mediterranean Sea underscored the need for a center to warn about natural objects that could cross Earth's orbit. When the asteroid, estimated at five to 10 meters in diameter, collided with the Earth's atmosphere, it released a burst of energy comparable to the nuclear bomb dropped on Hiroshima, Japan, in World War II. If the June 6 burst had occurred over India or Pakistan, which were on the brink of war at the time, it could have been mistaken for a military attack, pushing the two countries into a full-scale conflict, he said. "Neither of those nations has the sophisticated sensors we do that can determine the difference between a natural NEO impact and a nuclear detonation," Worden said. "The resulting panic in the nuclear-armed and hair-trigger militaries there could have been the spark" for a nuclear war. DOD currently gives NEO information to foreign countries on an informal basis, a process that can take weeks. Formalizing the process with a new early warning center could expedite that process, Worden said. A recent study concluded that such a center could be formed with just five to 10 people at U.S. space facilities in Cheyenne Mountain, Colo., Worden added. While the center would need only a modest amount of equipment to get started, it likely would influence the requirements for the next-generation space surveillance system now under development. At the moment, DOD has not given anyone the go-ahead to set up such a center. Worden also said that the U.S. should step up efforts to develop microsatellites, which can be produced and launched with far less money and time than regular satellites. Microsatellites could collect detailed information about a specific NEO, including its internal structure. Such information could be critical to figuring out how to divert the NEO from Earth's path. Building a new set of ground-based telescopes that are three meters in diameter also would be helpful because it would allow the U.S. to scan the entire sky every few weeks, according to Worden. The nation's most effective NEO sensor, MIT's Lincoln Lab LINEAR facility in New Mexico, misses many NEOs because its main optics are only one meter in diameter. Another roundtable speaker, Colleen Hartman, director of NASA's solar system exploration division, said 602 NEOs with a diameter of one kilometer or more have been identified, a number that could grow to as many as 1,080 with further study. The U.S. has focused its detection efforts on such large NEOs because they could cause a global catastrophe. NASA is studying ways to detect smaller ones, which could number in the hundreds of thousands, because they still could cause serious devastation, Hartman said. |
