NOTES FROM AIAA PLANETARY DEFENSE CONFERENCE 23-26 FEB 2004 By David Morrison The Planetary Defense Conference (Protecting the Earth from Asteroids) was held 23-26 February 2004 in Garden Grove, Orange County, California. The conference was sponsored by the AIAA (American Institute of Aeronautics and Astronautics) and the Aerospace Corporation, with 120 persons attending. The Chair was William Ailor and Technical Chair David Lynch, both of Aerospace Corp. ------------------------------------ PLANETARY DEFENSE CONFERENCE PART 1: DEFINING THE THREAT Congressman Dana Rohrabacher (R-Calif), one of the most influential members of the U.S. Congress in matters affecting space and science, gave the opening keynote address. Comparing the general apathy about the impact hazard with the public feeling about terrorism before 9/11, he expressed the hope that it would not require a similar catastrophe to alert people to the need to take action to protect the planet from impacts. He also compared the impact situation with global warming. He feels that the impact threat is better defined, and that real remedies are on the table, as opposed to global warming where it is not at clear what needs to be done or how to accomplish it. In addition to the current Spaceguard Survey to predict impacts that could cause a global catastrophe, Rohrabacher urged that we also deal with more frequent threats from smaller impacts. He feels that it is unacceptable for us to face the possibility of an impact that could kill millions without taking action to counter this threat. He asserted that the people in this room can save the planet, and that what we are starting is a long-term program that may not come to fruition for several decades. Congressmen Rohrabacher addressed the issue of gaining public support. He feels that an increased emphasis on the asteroid impact threat is consistent with the President's new space policy initiative. The Moon can provide a base of operations for dealing with asteroids as well as for future human flights to Mars. He stressed that the first imperative is to look up, to search for potential impactors, describing the legislation he recently introduced to authorize $20 million per year for NASA for each of the next two fiscal years to search for sub-km NEAs. He also advocated technology development to deflect NEAs, and work on a new heavy-lift launch system to enable such deflection missions. He urged his audience to become more involved with the political process, to work to make a better world in the future by defending our planet against this threat. We need idealism for saving the world. The first two papers in the opening session dealt with the basics of the impact hazard and current programs to deal with it. David Morrison (NASA Ames) summarized the hazard and the history of the Spaceguard Project. He made a rough analogy between protecting from asteroid impacts and other forms of defense. Dealing with the threat of asteroids larger than 1 km is a matter of national survival and deserves first priority. But we also need to be concerned about the smaller objects just as we are prepared to use limited military force to deal with small peacekeeping challenges. These are not a matter of national survival, but they are called for much more often. We hope never to have to deal with a civilization-threatening impact, but we can reasonably expect to face an impact by an asteroid 50 m in diameter. Don Yeomans (JPL) described the Spaceguard Survey and the excellent progress that is being made toward meeting the goal of finding 90% of the NEAs larger than 1 km by the end of 2008. He emphasized repeatedly the importance of early detection for any subsequent mitigation options to be realistic. The next three papers summarized the findings of the NASA Science Definition Team to study extending the survey to sub-km NEAs (published last August). Jenifer Evans (MIT) presented the main conclusions and described how the cost-effectiveness of various options was estimated. Even using a conservative approach to estimating the losses that would be expected from impacts by sub-km asteroids, the annualized losses are much greater than the costs of mitigating the hazard by a more capable survey. The sub-km hazard has two peaks, one for land impacts (near 200 m) and one for tsunamis from ocean impacts (nears 350 m). The total cost to carry out surveys that are 90% complete for NEAs larger than 140 m is less than $400 million, with both ground-based and space-based options possible. Steve Chesley (JPL) discussed the tsunami danger and described the methodology used for estimating the effect of tsunamis and the distribution of coastal populations that would be at risk. Because warning is possible of an impending tsunami, the risk of actual deaths is small but the destruction of economic infrastructure can be very large. Alan Harris (Space Science Institute) then described the search strategies that can be used for finding sub-km NEAs with the proposed Pan-STARRS and LSST next-generation search systems. An LSST-type telescope (8 m aperture with wide field of view) should be able to meet the requirements of an NEA survey while simultaneously satisfying the requirements for several exciting astrophysics programs. Two papers focused on the physical nature of NEAs. Steve Ostro (JPL) described the results of radar studies, which can determine size, shape, rotational state, and often detect binary objects or satellites. Today radar is our primary source of information about NEAs, with results obtained form both the Goldstone and Arecibo planetary radar systems. Keith Holsapple (U. Washington) discussed the possible internal states of NEAs, dealing with not only their composition but also possible high porosity. It is likely that many of the NEAs are rubble piles, but it is not clear how much strength such rubble piles would have. It is also possible that some NEAs have soft or fluffy surfaces, in which case they would respond to a deflection impulse very differently from solid rock or metal. Four papers dealt with various scenarios that we might face in attempting to defend the earth from NEA impacts. Paul Chodas (JPL) followed the history of 6 hypothetical objects, 4 NEAs and 2 comets, with orbits that would hit the Earth. In each case, the object was identified as a possible impactor (Torino scale 3) within a few months of its discovery, but it was a couple of years before the estimated probability of impact rose above 99%. For the two comet examples, the impact did not rise above 99% until the last few months. Without radar (which was not an option for these 4 examples) or the delivery of a transponder by spacecraft, it would not likely be possible to improve much on these orbital determinations. Clark Chapman (Southwest Research Institute) analyzed several scenarios primarily from the perspective of public perceptions, noting that we will face many more cases of false alarms or media misunderstanding than we will of actual impacts. We have had several such media scares already. He spent considerable time on the events of January 13, 2004, described in a previous news note (January 18, 2004). David Lynch (Aerospace Corporation) described four impact scenarios (3 NEAs and one comet) that had been selected by the conference organizers as a sample of the different situations we might face. The mission designers at this meeting were challenged to suggest how we might organize a defense mission to deal with these diverse cases. Andrea Carusi (Spaceguard Foundation) discussed strategies for deflection, emphasizing the value of early intervention. Two of the suggested case studies involve close passages to Earth decades before the impact. Asteroids that impact the Earth often have such resonant returns. If a force is applied before the close passages, much less energy is required - sometimes with a saving of several orders of magnitude. In one example, an early intervention that changes the velocity along the track by only a few microns/sec is enough to make the asteroid miss the "keyhole" that leads to a later impact with the Earth. A proposed ESA mission called Don Quijote would use a kinetic impact to test the application of such small impulses to change an asteroid orbit. Of course, such cases of resonant return are also very sensitive to the initial orbit and require extremely precise tracking to predict the future impact with confidence, probably demanding that a transponder be placed on the asteroid. If the future impact could not be predicted with confidence (because of such resonant returns), then it would be difficult to justify a deflection mission. The easiest deflection situation in energy terms is at the same time the most difficult to justify. Dennis Byrnes (JPL) reviewed spacecraft visits to comets and asteroids under the title "Asteroids and Comets I Have Loved". The list is quite impressive, with 11 comets and asteroids explored by spacecraft, as follows: ICE flyby of Comet Giacobini-Zinner. Multiple flyby missions to Comet Halley. Giotto (retarget) to Comet Grigg-Skellerup. Galileo flybys of asteroids Gaspra and Ida (and Ida satellite Dactyl). NEAR-Shoemaker flyby of asteroid Mathilde on the way to orbit and land on Eros. DS-1 flybys of asteroid Braille and Comet Borrelly. Stardust flyby of asteroid Annefrank and recent sample collection from Comet Wild 2. For the future we can expect: Hayabusa (MUSES-C) to asteroid Itokawa, Rosetta to Comet Churyumov-Gerasmenko, Deep Impact to Comet Tempel 1, and Dawn to orbit asteroids Vesta and Ceres. -------------------------------------- PLANETARY DEFENSE CONFERENCE PART 2: MITIGATION PROPOSALS Mike Belton (Tucson) described the results of the NASA-sponsored Arlington workshop on mitigation held in September 2002, focusing on what needs to be done now to ensure that an adequate base of scientific knowledge is created to allow efficient development of a reliable mitigation system when needed in the future. We should do early experiments to test mitigation approaches. The prime impediment is the lack of assigned responsibility or authority to any person or organization either to plan for mitigation or to deal with a specific threat if one develops in other words, nobody is in charge of protecting the planet against impacts. Policy makers should formulate a chain of responsibility for action in the event a threat becomes known, and the organizers of the Arlington workshop recommend that this responsibility be assigned to NASA. Alan Harris (Space Science Institute) spoke on Deflection Techniques: What Makes Sense? For asteroid deflection, a 10 yr lead time requires delta v of a bit less than 1 cm/s. The upper limit on impulsive delta v is escape v, which is of order the diameter in km (1 km asteroid has escape v about 1 m/s). For disruption, weeks to months are required for debris to disperse so only small fraction hits the earth. With short lead time no technique works well, while with more than a decade lead-time, either disruption or deflection can work. None of above takes resonant returns into account; such passages allow much smaller delta v to be applied before the earth swing-by - needs deflection of only hundreds of km, and delta v of order a mm/sec. The problem is to understand the NEA orbit well enough before the keyhole is encountered. For intersecting orbits, the delta v to rendezvous is comparable to impact velocity, e.g., 10-20 km/s. (For example, the B612 scenario below requires 15 times more fuel to get to the asteroid than to make 0.2 cm/s velocity change). Dealing with spinning asteroid can be difficult; non-principle axis rotation may be common among small asteroids. What makes sense for us to work on now: (1) heavy lift launch vehicles (2) high efficiency space propulsion systems (3) well documented impact experiments (4) theoretical studies of nuclear options. Harris emphasized that asteroid mitigation is not a job for leftover ICBMs and warheads, that experimental nuclear explosions in space are politically difficult, and of course the cost of risk prevention should not exceed its value. Several speakers discussed the use of nuclear explosives either for destruction or deflection. David Dearborn (Livermore National Lab) discussed coupling of nuclear blast energy into NEOs. Nuclear explosives provide by far the most efficient packaging of energy (a million times more energy than the same mass of chemical explosive). For deflection, he noted that only by applying the force vector along the trajectory do we change the total angular momentum of the NEA and provide a shift that is cumulative over many orbits. Forces applied in other directions to change inclination or eccentricity do not produce cumulative effects (except in unusual resonant return cases). With conservation of momentum, we can readily calculate how much reaction mass must be ejected based on mass of asteroid, velocity of material ejected, and required change in asteroid velocity. For deflection, must keep delta v much less than escape velocity. Standoff explosion heats rock and vaporizes material to exert reaction force. The explosion needs to be within 1 radius or we lose most of energy. For a delta-v of 1 cm/sec on kilometer-scale object, we need to vaporize the top 2 cm. X-rays dont penetrate deep enough, but neutrons are more penetrating and give centimeters of heating. We could deflect a 1 km object by cm/s with a few megatons explosion of a neutron-rich nuclear device. Vadim Simonenko (Russian Federal Nuclear Center, Snezhinsk) spoke of the use of nuclear detonation, for either dispersion or deflection. Sub-km objects can be dispersed (blown apart) by nuclear explosions without detailed knowledge of their material properties, but larger objects are more challenging. For deflection we would probably use multiple explosions. Oleg Shubin (also of the Russian Federal Nuclear Center) discussed legal and political issues. He argues that before we implement a nuclear defense system, we need to study the efficiency of nuclear explosion effects on NEAs. We will also need experimental modeling, culminating in full-scale space testing. Are such tests consistent with Nuclear Test Ban treaties? Although these are not weapons of mass destruction (not bombs), the current international treaties ban all tests in space, whether for weapons or peaceful purposes. Most restrictive is the Comprehensive Test Ban Treaty, which completely prohibits nuclear explosions in space. Shubin concluded that the chances to change the CTBT are insignificant until the world community changes its attitude so that peaceful explosions are decoupled from concerns about a new generation of nuclear weapons. Mark Barrera (Aerospace Corp) presented results of a study of using nuclear explosions for Deflecting a NEO with Todays Space Technology. One of the example scenarios was a 200 m asteroid with only 11 yr warning, discovered in 2005, requiring use of current technology. Assume the USAF has task to deflect it using standoff nuclear (neutron-rich) explosions and existing launch vehicles. The goal is to reduce probability of impact below 1 in 100,000. To achieve this goal we must deflect the error ellipsoid, which requires more than deflecting the centerline of the predicted orbit. Requires delta v of several cm/s depending on how early we can reach the asteroid and apply impulse. For nominal coupling of blast to object this plan requires a 1500 kg explosive package. He assumes 2-3 years to develop the spacecraft. Several launch windows (2008-2012) all require heavy-lift launch vehicle, with multiple interceptors to improve system reliability. In this study, mission reliability is the key factor that drives us to multiple designs and launches. Ed Lu (NASA JSC) discussed deflection using high-efficiency plasma engines, noting that we can only learn how to build and operate spacecraft by doing it. Thus the B612 Foundation's demo mission (described in their Scientific American article 4 months ago) proposes to change the orbit of a small NEA in a measurable way by 2015. The nominal approach is to dock and push or pull with a tether. Emphasis is on controllable deflection that does not risk breakup. What we will learn will be applicable to most any methods of controlled deflection. To rendezvous with the asteroid we need to plan for spacecraft delta v of at least 10 km/s beyond the range of chemical rockets. Since we need a high ISP plasma system to get there, we might as well use the same system to move the asteroid. He argues for a single spacecraft launch, with no space assembly required, and a test target near 200 m (10 million tons mass). Delta v of 0.2 cm/s (enough to measure) requires several months of thrusting; this same approach would change velocity enough to prevent a collision given 50 yr warning (thrust of order 1N, with ISP of several thousand). Plasma drive power requirement is 200 kw (reasonable for nuclear electric power, consistent with NASA Prometheus Program.) Continuing with various aspects of the B612 proposal, Mike Houts (Los Alamos National Lab) discussed Near-term Fission Power Systems for spacecraft. As an illustration, he noted that fissioning 12 fl oz (a soda can) of uranium releases 50 times the energy contained in a Shuttle external tank. Current designs for Prometheus use U-235 fueled, 1200 kWt electric power, Beryllium neutron reflector, but with different cooling (heat transport) modes under study. The reactor will be launched cold so that there is no danger of radioactive contamination even if there is a launch accident. Dan Scheeres (University of Michigan) presented a paper on Close Proximity Operations at Small Bodies, which will be a necessary part of all mitigation approaches. The situation of orbiting or operating near a very small body is complex, depending on size, shape, internal structure, spin state (relative to orbit plane), and satellites. Scheeres also discussed The Mechanics of Moving an Asteroid (the Asteroid Tug). The requirement is to alter the asteroid trajectory in a controlled way. Must control asteroid and thrusting spacecraft as a unit in order to apply thrust along orbit trajectory. Delta v of 1 cm/s velocity change shifts asteroid by about 1000 km/yr at encounter. Dan Durda (SWRI) further discussed the B612 Mission, including the new idea of Lu gravitational "tractor beam" to link spacecraft with asteroid, so that no landing is required and we dont need to worry about asteroid physical properties or spin state. Jay Melosh (U. Arizona) presented a paper on the Mirror Ablation Mission. He told how a decade age, he and I. Nemchinov began to work on non-nuclear options in reaction to suggestions by Edward Teller and others to build bigger nuclear bombs to defend against asteroids. His case study focused on a 1 km asteroid: requires 5000 N applied for one year. Needs mass flow rate of few kg/s to mimic comet jets. Evaporation of solids into near-vacuum is well understood. Requires temperature as high as 3000 K. Entrained solids dont matter as long as the mass flows away from the asteroid; solids give more mass but lower ejection velocity. Temperature rise time is of order 1 min, so we may not need to worry about rotation unless they rotation rate is high. Large inflatable mirrors have been designed, but the biggest unsolved problem is degradation of the optical system by outflowing hot gas and dust. Theoretical performance is very high, but there are many practical problems to be overcome. ---------------------------------------------- PLANETARY DEFENSE CONFERENCE PART 3: SOCIETAL ISSUES Lee Clarke (Rutgers University) provided a keynote talk on Some Human Questions in Planetary Defense. What will people and institutions do if a strike is announced? What will people and institutions do if we predict a strike that will happen far in the future? What will people and institutions do after a strike? Conventional wisdom is that panic is supposed to be a major issue. But we have a robust finding from historical examples of disasters in U.S. that is it very hard to induce panic (e.g., disorganized flight, anti-social behavior). We should jettison panic as an issue for NEOs, especially when it is used as an excuse for withholding information. We should also consider that planetary defense might be difficult to deal with internationally, since international competition and conflict are historically just as real as international cooperation. Meanwhile we have challenges in communicating the risk. We need to communicate down, up, and sideways (multiple audiences need multiple messages). These are difficult issues it may require a strike (by a small NEA, we hope) as a wake-up call before a major mitigation program can be implemented. In another keynote, Oliver Morton (London) provided historical context. The current interest in impacts represents a real change. Astronomy is the most predictive science but is disassociated from terrestrial affairs. From the 18th century, astronomers have emphasized this distance. Special efforts were made to demystify comets and allay public fear of comets. From the mid ninetieth century, geologists adopted a strictly uniformitarian approach in which catastrophic events were not considered. These ideas have persisted until recently, for example in the New York Times editorial (April 7 1985) which said in the context of the proposed KT impact: Astronomers should leave to astrologers the task of seeking the cause of earthly events in the stars. Not until well into the second half of 20th century were either astronomers or geologists willing to consider possible role of impacts. Science fiction was slightly ahead (Heinlein: The Moon is a Harsh Mistress, 1966. Blish & Knight: A Torrent of Faces, 1967. Clarke: Rendezvous with Rama, 1973. Niven & Pournelle: Lucifers Hammer, 1977). Only after the Alvarez paper on the KT impact (1980) did these ideas start to become respectable. The KT provided a colorful story about breaking a paradigm, catastrophes, dinosaurs and environmental change. Now we are in a new situation, trying to popularize the idea of the hazard of impacts. As public interest grows it naturally focuses not on what is the greatest danger but on what is the most likely event. Also, the post 9/11 world is concerned with what are very small events by astronomical standards. We should accept this and use it. Geoff Sommer (RAND) discussed policy issues associated with a NEO mitigation system, using economic policy analysis approaches. A strong case can be made for finding NEAs larger than 1 km, since there is a compelling qualitative incentive for protecting against the end of civilization. However, the issue is more complex for sub-km impacts. Most of the scenarios proposed for this meeting skip the most critical issue uncertainty about whether the hit will take place. In reality the uncertainty may dominate thinking. We should try to maximize net social benefit. In reality, the purpose of Spaceguard (to retire the risk) is to reduce dread . Warning has little social value by itself; indeed the purpose of warning is vitiated without an ability to mitigate. In addition, false warnings (false positives) impose social costs that are not counterweighted by benefits. It is difficult to model the expected NEO alarm rate for any search program (How often will Earth be in an uncertainty ellipse, for how long, etc.) We have not adequately considered the social costs of warning. Note that even a minuscule reduction in percent global GDP resulting from false alarms will swamp any direct benefits in NEO hazard reduction. Possible ways to reduce the costs of false warnings (1) control or manage information (2) restrict surveys (3) demonstrate a mitigation capability. Mitigation systems have positive social value if they increase public confidence. In some cases a technically ineffectual mitigation system can still be very effective (for example, the Patriot missile defense system deployed to Israel in the 1991 Gulf War reduced fear and kept Israel out of the war even though it never successfully intercepted any incoming Iraqi missiles). Even a small start on a mitigation system may be sufficient to negate alarms and will thus will be seen as having positive social and economic value. John Lodgson (George Washington U.) noted that historically, it takes a long time for new issues to lead to policy action. Do we need to wait for an impact to get public action? Perhaps there is a window of opportunity open for planetary defense through the new U.S. Presidents space policy. This NASA policy is much broader than the usual media characterization. It includes strong science and security issues that are related to asteroid defense. But there are no specific asteroid missions in the new NASA Roadmap. We need to market asteroid missions to NASA. Rusty Schweickart (B612 Foundation) addressed The Real Deflection Dilemma. The deflection dilemma was posed by Carl Sagan a decade ago, when he expressed concern that the defense systems against asteroids would be used so rarely that there is a larger chance of misuse -- specifically of an asteroid being deflected toward the earth as a weapon. Schweickart argues that the only precision deflection systems that we are likely to build will not have excess capability only enough to move the impact point off the earth. The probability of finding a NEA that comes close enough to earth to use as a weapon is just as small as the probability of being hit of order once in a millennium even for Tunguska class impacts. The real dilemma is associated with controlled deflection, where the impact point is slowly migrated across the earth in the process of being moved off the planet. Who decides on the path, and who can be trusted to implement the deflection? Morrison noted that we could imagine nations sending their own spacecraft to make sure the path did not cross their territory, and even of different groups trying to push the asteroid in different directions. Evan Seamone (US Army) spoke on The Precautionary Principle as the Law of Planetary Protection. He touched upon a number of legal issues and urged us to learn from existing law concerning obligations to warn of or mitigate dangers on an international level. We need to understand the binding legal obligations influencing planetary protection. Liability can be incurred for either inaction or negligent rescue. The greater the threat, and hence the greater the risk of inaction, the more compelling is the case for taking anticipatory action even if uncertainty remains as to the time and place of the enemys attack. The are precedents in the current legal framework for dealing with terrorist threats under Homeland Security Presidential Directive HSPD-5. The HSPD-5 also requires consolidation of major national disaster plans into a single all-discipline all-hazards plan. This makes the Department of Homeland Security the Lead Agency in the U.S. when more than one federal department or agency has become substantially involved, although to date they have shown no interest in the impact hazard. Mike Belton (Tucson). Toward a National Program to Remove the Threat of Hazardous NEOs. We need a government champion for new programs such as NEO defense. Public support is not required, but negative public opinion can kill the initiative. Big rare impacts are the greatest risk but they are not a suitable basis for starting a program (times are too long, also requires doing the hardest things first in terms of mitigation). Indefinite waiting or lack of an application surely invites low priority and neglect. His proposed new goal is to reliably mitigate or avoid the most probable kind of impact that can cause serious damage to the social infrastructure in the lifetime of the current population. The expected program cost must be consistent with the expected losses incurred in the impact. Program should be defined for what it is, a technical goal, not science, and he suggests a mitigation budget within NASA of order $10B over the next 25 years. Pete Worden (BG USAF, on his last week of active duty in the Air Force) spoke on The NEO Threat and Mitigation Issues: An Air Force (barely) Perspective. A wide range of related concerns for the military include orbital debris, meteor storms, small (Tunguska class) NEOs, and civilization threatening NEOs. One major issue is Command and Control (e.g., need for a NEO Warning Center). Also national vs. international, civil vs. military. He finds that it is useful in briefings to emphasize recent events (atmospheric impacts). The focus for planetary defense should be on small objects (10 m to 500 m). We are making progress with the NEO hazard issue, but there is still a giggle factor within the Pentagon. DoD may have interest in developing dual-use technology but not in assuming responsibility for NEOs. Neither NASA or the DoD seems willing to take on this responsibility. ============================ PART 4: TWO ARTICLES BY LEONARD DAVID FROM SPACE.COM PLANETARY DEFENSE: PLANNING WITH PHANTOM ASTEROIDS By Leonard David, Space.com, 24 February 2004 GARDEN GROVE, CALIF. - Authorities in defending the Earth from a cosmic run-in with an asteroid or comet have gathered here to detail ways to thwart future impacts and deal with the calamity if our planet is struck. An international group of scientists, engineers, space policy makers, and others are taking on the task of improving our ability to successfully defend our planet from possible impact threats. Attention is focused on four fictitious Defined Threat (DEFT) scenarios that endanger the Earth. The approaching virtual asteroids have been dubbed D'Artagnon, Athos, Aramis, and a long-period comet called Porthos. At this time, none of these names is assigned to a real asteroid or comet. The DEFT scenarios -- which include various trajectories and time-to-impact assumptions -- are meant to spur designs of rendezvous, intercept and deflection missions and spark discussion of how the world community might prepare for mitigation efforts or possible disaster from policy, public education, and other perspectives. No known comets or asteroids are presently on a collision course with Earth, but scientists say a regionally devastating impact -- perhaps within a hundred years, more likely not for a thousand or more -- is eventually inevitable. Yet there are no governmental plans to deal with diverting or destroying an asteroid, managing regional evacuations or dealing with the chaos that might ensue from a collision. The Planetary Defense Conference: Protecting Earth from Asteroids held here Feb. 23-26 is sponsored by the Aerospace Corporation and the American Institute of Aeronautics and Astronautics (AIAA). "We're looking at the entire issue ...from the hazard itself through the political and policy issues, as well as disaster mitigation," said William Ailor of Aerospace Corporation and general chair of the conference. Ailor told SPACE.com the meeting will recur every four years. "That way we can assess changes that have, hopefully, increased our abilities to deal with these kinds of threats ... and assess current political realities," he said. "We've got the capability to do something about a threat now -- at least we may have," Ailor said. "Certainly we could, over a period of time, develop some expertise that would allow us to mitigate a reasonably sized threat. But if we don't start thinking about this, it's not going to happen. So that's the purpose here ... to start the process of being prepared." A session chair at the conference is Rusty Schweickart, former NASA astronaut and now director of the B612 Foundation, a nonprofit group dedicated to developing and demonstrating the capability to sidetrack asteroids that might smack into Earth. "The fact that a devastating asteroid impact with Earth is a low probability event, it is not zero. It has happened before. If we do not prevent such an occurrence when we have the capability to do so, it would be the greatest crime in human history," Schweickart said. Planetary defense advocates don't need to dig too far into history to make their case for being better prepared. For example, on the night of Jan. 13-14 of this year, the asteroid detection community faced an unprecedented real-world situation. Preliminary predictions of the trajectory of newly-spotted asteroid AL00667 showed it on a course to possibly hit Earth within a few days. The object was roughly 100 feet (30 meters) in diameter -- big enough that ground damage, even public injury, could not be ruled out. The distinct possibility of AL00667 striking Earth remained uncertain for several hours. Follow-up observations of where the asteroid should have been if it was on a heading to mess up Earth proved negative. The rock's true orbit was found not to intersect with our planet. A behind-the-scene drama played out among a tight group of asteroid experts and professional as well as amateur astronomers -- all without the doom and gloom of scary newspaper headlines and TV reports that have plagued asteroid observations in past years. The event, nonetheless, left a small group of experts arguing vehemently about what should and should not have been done with the initial observations of AL00667. In recent days, the scientists have traded barbs and accusations over how to properly evaluate and release data on space rocks that might be headed our way. Among their concerns is how the public might react to an impending threat, and how they might not react if scientists cry wolf too many times. While a small asteroid like AL00667 could hit Earth with only a few days' notice, larger planet-rattlers would likely be spotted years or decades before impact. Social scientists have been studying disasters for 50 years, but only recently has any of that knowledge been brought to bear on the NEO problem. While delving into the technical and operational details of deflecting or destroying threatening asteroids is critical, the "human aspects" of the problem are crucial too, said Dan Durda, a space scientist from the Southwest Research Institute in Boulder, Colorado. "How would responsible officials and the public actually react to the prospect of a major impact three or four decades in the future?" Durda wonders. "What would we do if we had very short notice of an impending, very small scale event? Is there enough redundancy in the critical programs that monitor the impact hazard and connect the network of observers and orbit calculators? These issues are as important, and perhaps even more difficult to deal with, as the technical ones involving the physical act of deflecting or destroying a threatening asteroid." Durda said the recently announced White House space vision is redefining and refocusing NASA's space exploration and human spaceflight priorities. "I believe that the near-Earth asteroids can and should play an important role in this process," Durda explained. "The same technologies and techniques that we will need to develop to routinely explore the Moon and Mars and to extract resources from near-Earth asteroids are the same ones that we could one day need to employ to ward off an impending impact." Durda added: "I'm sure we'll be doing the former long before we'll ever need to do the latter, but it'll sure be nice to have had the practice first!" "I think this is the first [meeting] that promises to get the scientists and the engineers together in a really meaningful way. And the social scientists and policy makers are here too," said Clark Chapman, an asteroid expert from Southwest Research Institute. "I am personally hopeful that this will be a venue for really serious consideration of the B612 concept -- and other equivalent or competing ideas -- because the aerospace companies will be mixing with the rest of us." Furthermore, Chapman said, there are new opportunities in the new environment at NASA after President Bush set a course in January to put humans back on the Moon. Those opportunities, he added, could go in the wrong direction as far as asteroid researchers are concerned. "But at the moment there is reason for some optimism that this may be a better environment, from this parochial perspective," he said. Chapman said that he hoped attention to the recent AL00667 incident "may finally nudge some people into seriously developing protocols for dealing with these mini-crises, which many scientists believe are bound to recur. ----------------------------------------- EARTH AT RISK: NEW CALLS FOR PLANETARY DEFENSE By Leonard David, Space.com, February 25, 2004 GARDEN GROVE, California - It is past time to get serious about planetary defense, experts say. The threat of Earth being on the receiving end of a cosmic calling card in the form of an asteroid or comet is real. Despite increasing scientific agreement regarding the danger posed by near-Earth objects smashing into our planet, governmental steps to deal with the issue are missing-in-action. At present, only patchwork and under-funded research efforts are underway to robustly detect, track, catalog and plot out strategies to thwart menacing asteroids and comets that place Earth at risk. An international confab of experts is taking part in The Planetary Defense Conference: Protecting Earth from Asteroids here this week and sponsored by The Aerospace Corporation and the American Institute of Aeronautics and Astronautics (AIAA). The four-days of discussion were kicked off by Congressman Dana Rohrabacher, Chairman of the House Science Committee's Space and Aeronautics Subcommittee Rohrabacher noted that it took the attacks of Sept. 11 for the country to focus on global terrorism. "I hope that it won't take that type of catastrophe for us to start paying attention to the threats of near-Earth objects," he said. The lawmaker said the political reaction to the worries over space rocks has garnered "a very tepid response" to date, noting that money spent so far on the issue has been "a pittance." President George W. Bush's new visionary blueprint for NASA - including a human return to the Moon and sending astronauts to Mars - was saluted by Rohrabacher. That plan, he added, can also support planetary defense objectives. "The Moon could well be a base of operations that we could use as a means to defend this planet in a timely way, and a more effective way, against near Earth objects," Rohrabacher explained. Taking a "let's get going," roll-up-your sleeves attitude, Rohrabacher said there is need to start now in readying the technologies necessary to deflect an Earth-threatening object. "What we need to do is build from right here...this moment. The people in this room can save the planet." There is no question that an asteroid has Earth's name on it, astronomers agree. But where the rock is and when that impact is going to occur is unknown, said David Morrison of the NASA Astrobiology Institute at the space agency's Ames Research Center at Moffett Field, California. NASA now supports -- in collaboration with the United States Air Force -- the Spaceguard Survey and its goal of discovering and tracking 90 percent of the Near Earth Asteroids (NEAs) with a diameter greater than about one-half mile (1 kilometer) by 2008. If one of these big bruisers were to strike our planet, it would spark catastrophic global effects that would include severe regional devastation and global climate change. By charting the whereabouts of these celestial objects, it is anticipated that decades of warning time is likely if one of the large-sized space boulders was found to be on a heading that intersects Earth. But a uniform message from the experts attending this week's planetary defense gathering is extending the survey to spot smaller objects, down to some 500 feet (150 meters) in diameter. These asteroids can wreak havoc too, but on a more localized scale. For instance, if one of these smaller asteroids were to strike along the California coast, millions of people might be killed, Morrison said. A little further to the east, he added, "a nice crater out in the desert" would become a tourist attraction. In identifying ways to deal with hazardous asteroids, a first order of business is gaining a better understanding of the enemy. That is, are they fluffy stuff, constituting a rubble pile, or are they tough-as-nails slabs of iron? Along with these physical properties, astronomers want to know more about their overall shape, rotation rate, and whether an object might play host to a smaller companion body. Developing a robust deflection scheme so an asteroid doesn't hit Earth means taking into account these factors and a host of other issues, said Don Yeomans, a leading asteroid and comet scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California. Developing a viable mitigation campaign, Yeomans explained, demands three prerequisites: "You need to find them early. You need to find them early. And we need to find them early." Now being discussed is a way to flex, test, and calibrate present day computer and hardware tools to first detect and then keep a trained eye on a potential Earth impactor. There are currently three Earth-impactors en route. But don't worry. It's all friendly fire. NASA's Genesis spacecraft is headed this way in September of this year. So too is the Stardust spacecraft in January 2006, as will be a Japanese asteroid sample mission in June 2007. All three are designed to reenter the Earth's atmosphere and touch down on terra firma, each carrying a precious cargo of scooped-up specimens. "So we do have current impactors coming back," Yeomans said. While still in the preliminary discussion stage, the idea is to use these incoming spacecraft to shake out coordinated observations, sharpen orbit calculation skills, and help fine-tune procedures now in place for detecting and tracking asteroids and comets, he told SPACE.com. Yeomans said about 40 objects at least 3 feet (1 meter) in size enter the Earth's atmosphere every year. Some of these incoming objects have been observed by space-based infrared and visible sensors and other ground-based detection devices operated by the U.S. military and other government agencies, he said. "They have indeed made many of these observations available to scientific investigators," Yeomans said. "It would be nicer to get these things [the data] a little more quickly than 3-4 months down the road,' he added, with near-simultaneous flow of information about such events seen as ideal. A clear and present danger for those studying planetary defense is the lack of any chain-of-command to take on the duties of dealing with the prospect of disruptive collisions from asteroids and comets. This "who do you call?" factor deserves immediate attention, said Michael Belton of Belton Space Exploration Initiatives in Tucson, Arizona. Belton detailed the findings of a NASA-sponsored 2002 workshop. It brought together over 75 top scientists, engineers and military experts from the United States, Europe, and Japan to review the science behind mitigating hazardous comets and asteroids. The 2002 workshop did recommend that NASA be assigned the duty to advance work in beefing up the science and ability to respond to an imminent collision with an asteroid or comet nucleus. Furthermore, the now-in progress Spaceguard Survey should be extended to scope out possible impactors down to 655 feet (200 meters) in size. In addition, Belton said that there is need for the Defense Department to more rapidly communicate surveillance data on natural airbursts. And lastly, there's need for governmental policy makers to formulate a chain of responsibility for action in the event a threat to the Earth becomes known. "In other words...there isn't anybody to call. There is nobody there. And there's nobody with authority...nobody with any resources," Belton said. "And we need to correct that." |
