National Space Society: Planetary Defense Library

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Abstract: This National Preparedness Strategy and Action Plan for Near-Earth Object Hazards and Planetary Defense (2023 Planetary Defense Strategy) updates the United States’ first comprehensive Near-Earth Object Preparedness Strategy and Action Plan, released in 2018. The 2023 Planetary Defense Strategy builds on existing efforts by Federal Departments and Agencies to address the hazard of NEO impacts, includes evaluation of where progress has been made since 2018, and focuses future work on planetary defense across the U.S. government.

Abstract: In April 2023 the United States released the National Preparedness Strategy and Action Plan for Near-Earth Object Hazards and Planetary Defense (National Planetary Defense Strategy). This NASA strategy responds to the U.S. National Planetary Defense Strategy, and focuses Agency-level activities within NASA, describing existing efforts to survey the Near-Earth Object (NEO) population, assess risks and develop approaches to prevent or mitigate NEO impacts on Earth. It provides guidance to improve current efforts and charts a robust yet realistic path forward for planetary defense activities at NASA.

Abstract: The National Near-Earth Object Preparedness Strategy and Action Plan (Strategy and Action Plan) will improve our Nation’s preparedness to address the hazard of near-Earth object (NEO) impacts over the next 10 years. Its primary role is to help organize and coordinate NEO-related efforts within Federal Departments and Agencies (agencies), with a particular focus on efforts that are already existing and resourced. It seeks to leverage and enhance existing assets and capabilities—National and international, public and private—to effectively manage the risks associated with NEOs. The Strategy and Action Plan builds on efforts by the National Aeronautics and Space Administration (NASA), Department of Homeland Security (DHS), and Department of Energy (DOE) to detect and characterize the NEO population and to prevent and respond to NEO impacts on Earth.

2015: READI: Roadmap for EArth Defense Initiatives. International Space University.

Abstract: Planetary Defense is a complex problem, not well understood by policy makers and the general public. The recent Chelyabinsk incident in Russia created temporary international attention but has failed to effectively stimulate public action. The lack of long-term attention to cosmic hazards has resulted in limited funding to defend our planet. Hence, it is hard to realistically address this challenge and achieve the high test and operational readiness needed for an effective Planetary Defense strategy. To address this problem, we have created a set of recommendations for the development of a Planetary Defense Program, for the purpose of contributing to the protection of Earth from asteroids and comets. The SSP15 READI Project focused on threats for which there is only a short-term warning, specifically a warning of two years or less from detection of the object to impact. We have provided recommendations in five areas of Planetary Defense including detection and tracking, deflection techniques, global collaboration, outreach and education, and evacuation and recovery. We have applied this set of recommendations in a narrative scenario to make our report more impactful and engaging. We contrast optimistic and pessimistic outcomes for a comet threat, differing from each other in terms of the level of readiness achieved during the years leading up to the discovery of the threat. In our optimistic scenario, the deflection system has achieved high test and operational readiness. The world’s governments have realized the importance of being prepared against cosmic hazards and put in place all of the necessary measures for a successful defense, leading to a positive deflection of the comet. In contrast, in the pessimistic scenario no preparation is done before the detection, and the comet strikes a heavily populated area releasing energy equivalent to 80 times the most powerful nuclear bomb ever detonated. The recommendations that we have identified in this report constitute a roadmap to avoid this horrible outcome, and we believe they should be taken seriously and swiftly implemented.

Abstract: With the NEOWISE portion of the Wide-Field Infrared Survey Explorer (WISE) project, we have carried out a highly uniform survey of the near-Earth object (NEO) population at thermal infrared wavelengths ranging from 3 to 22 µm, allowing us to refine estimates of their numbers, sizes, and albedos. The NEOWISE survey detected NEOs the same way whether they were previously known or not, subject to the availability of ground-based follow-up observations, resulting in the discovery of more than 130 new NEOs. The survey’s uniform sensitivity, observing cadence, and image quality have permitted extrapolation of the 428 near-Earth asteroids (NEAs) detected by NEOWISE during the fully cryogenic portion of the WISE mission to the larger population. We find that there are 981±19 NEAs larger than 1 km and 20,500±3000 NEAs larger than 100 m. We show that the Spaceguard goal of detecting 90% of all 1 km NEAs has been met, and that the cumulative size distribution is best represented by a broken power law with a slope of 1.32±0.14 below 1.5 km. This power law slope produces ~ 13,200±1,900 NEAs with D >140 m. Although previous studies predict another break in the cumulative size distribution below D ~50-100 m, resulting in an increase in the number of NEOs in this size range and smaller, we did not detect enough objects to comment on this increase. The overall number for the NEA population between 100-1000 m is lower than previous estimates. The numbers of near-Earth comets and potentially hazardous NEOs will be the subject of future work.

Abstract: Recommendation 1: Organize for Effective Action on Planetary Defense. NASA should establish an organizational element to focus on the issues, activities and budget necessary for effective Planetary Defense planning; to acquire the required capabilities, to include development of identification and mitigation processes and technologies; and to prepare for leadership of the U.S. and international responses to the impact hazard. Recommendation 2: Acquire Essential Search, Track, and Warning Capabilities. NASA should significantly improve the nation’s discovery and tracking capabilities for early detection of potential NEO impactors, and for tracking them with the precision required for high confidence in potential impact assessments. Recommendation 3: Investigate the Nature of the Impact Threat. To guide development of effective impact mitigation techniques, NASA must acquire a better understanding of NEO characteristics by using existing and new science and exploration research capabilities, including ground-based observations, impact experiments, computer simulations, and in situ asteroid investigation. Recommendation 4: Prepare to Respond to Impact Threats. To prepare an adequate response to the range of potential impact scenarios, NASA should conduct a focused range of activities, from in-space testing of innovative NEO deflection technologies to providing assistance to those agencies responsible for civil defense and disaster response measures. Recommendation 5: Lead U.S. Planetary Defense Efforts in National and International Forums. NASA should provide leadership for the U.S. government to address Planetary Defense issues in interagency, public education, media, and international forums, including conduct of necessary impact research, informing the public of impact threats, working toward an internationally coordinated response, and understanding the societal effects of a potential NEO impact.

2010: Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies: Final Report. National Research Council Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies. PDF 132 pages (free download from National Academies Press website).

Abstract: The United States spends approximately $4 million each year searching for near-Earth objects (NEOs). The objective is to detect those that may collide with Earth. The majority of this funding supports the operation of several observatories that scan the sky searching for NEOs. This, however, is insufficient in detecting the majority of NEOs that may present a tangible threat to humanity. A significantly smaller amount of funding supports ways to protect the Earth from such a potential collision or “mitigation.” In 2005, a Congressional mandate called for NASA to detect 90 percent of NEOs with diameters of 140 meters of greater by 2020. Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies identifies the need for detection of objects as small as 30 to 50 meters as these can be highly destructive. The book explores four main types of mitigation including civil defense, “slow push” or “pull” methods, kinetic impactors and nuclear explosions. It also asserts that responding effectively to hazards posed by NEOs requires national and international cooperation. Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies is a useful guide for scientists, astronomers, policy makers and engineers.

2009: Impact Hazard Mitigation: Understanding the Effects of Nuclear Explosive Outputs on Comets and Asteroids. Clement, et. al., Los Alamos National Laboratory. Advanced Maui Optical and Space Surveillance Technologies Conference, September 2009.

Abstract: The NASA 2007 white paper “Near-Earth Object Survey and Deflection Analysis of Alternatives” affirms deflection as the safest and most effective means of potentially hazardous object (PHO) impact prevention. It also calls for further studies of object deflection. In principle, deflection of a PHO may be accomplished by using kinetic impactors, chemical explosives, gravity tractors, solar sails, or nuclear munitions. Of the sudden impulse options, nuclear munitions are by far the most efficient in terms of yield-per-unit-mass launched and are technically mature. However, there are still significant questions about the response of a comet or asteroid to a nuclear burst. Recent and ongoing observational and experimental work is revolutionizing our understanding of the physical and chemical properties of these bodies (e.g., Ryan (2000), Fujiwara et al. (2006), and Jedicke et al. (2006)). The combination of this improved understanding of small solar-system bodies combined with current state-of-the-art modeling and simulation capabilities, which have also improved dramatically in recent years, allow for a science-based, comprehensive study of PHO mitigation techniques. Here we present an examination of the effects of radiation from a nuclear explosion on potentially hazardous asteroids and comets through Monte Carlo N-Particle code (MCNP) simulation techniques. MCNP is a general-purpose particle transport code commonly used to model neutron, photon, and electron transport for medical physics, reactor design and safety, accelerator target and detector design, and a variety of other applications including modeling the propagation of epithermal neutrons through the Martian regolith (Prettyman 2002). It is a massively parallel code that can conduct simulations in 1-3 dimensions, complicated geometries, and with extremely powerful variance reduction techniques. It uses current nuclear cross section data, where available, and fills in the gaps with analytical models where data are not available. MCNP has undergone extensive verification and validation and is considered the gold-standard for particle transport. (Forrest B. Brown, et al., “MCNP Version 5,” Trans. Am. Nucl. Soc., 87, 273, November 2002.) Additionally, a new simulation capability using MCNP has become available to this collaboration. The first results of this new capability will also be presented. In particular, we will show results of neutron and gamma-ray energy deposition and flux as a function of material depth, composition, density, geometry, and distance from the source (nuclear burst). We will also discuss the benefits and shortcomings of linear Monte Carlo. Finally, we will set the stage for the correct usage and limitations of these results in coupled radiation-hydrodynamic calculations (see Plesko et al, this conference).

2009: Planning Ahead for Asteroid and Comet Hazard Mitigation, Phase 1: Parameter Space Exploration and Scenario Modeling. Plesko,, Los Alamos National Laboratory. Advanced Maui Optical and Space Surveillance Technologies Conference, September 2009.

Abstract: The mitigation of impact hazards resulting from Earth-approaching asteroids and comets has received much attention in the popular press. However, many questions remain about the near-term and long-term feasibility and appropriate application of all proposed methods. Recent and ongoing ground- and space-based observations of small solar-system body composition and dynamics have revolutionized our understanding of these bodies (e.g., Ryan (2000), Fujiwara et al. (2006), and Jedicke et al. (2006)). Ongoing increases in computing power and algorithm sophistication make it possible to calculate the response of these inhomogeneous objects to proposed mitigation techniques. Here we present the first phase of a comprehensive hazard mitigation planning effort undertaken by Southwest Research Institute and Los Alamos National Laboratory. We begin by reviewing the parameter space of the object’s physical and chemical composition and trajectory. We then use the radiation hydrocode RAGE (Gittings et al. 2008), Monte Carlo N-Particle (MCNP) radiation transport (see Clement et al., this conference), and N-body dynamics codes to explore the effects these variations in object properties have on the coupling of energy into the object from a variety of mitigation techniques, including deflection and disruption by nuclear and conventional munitions, and a kinetic impactor.

Abstract: Primary recommendations from the meeting were: A concerted effort must be made to discover and track objects of 140 meters in size and larger. Funding for Arecibo and other instruments capable of providing precise dynamical and physical characterization data for objects that pose a threat to Earth must be maintained. International participation in funding and research related to NEO discovery, tracking, and mitigation must increase. Deflection-related testing should be included as part of science missions to asteroids and comets to increase information relevant to the mitigation process. Simulations of NEO atmospheric entries and land and water impacts should be funded in order to develop reliable relationships between NEO energies and impact consequences. Additional studies should be conducted to understand and quantify the momentum transferred to comets and asteroids by impulsive deflection techniques (kinetic impact and standoff, contact, and sub-surface explosions). Protocols and assigned responsibilities must be developed for a global response to a NEO threat.

2009: Dealing with the Threat to Earth from Asteroids and Comets. International Academy of Astronautics. Ivan Bekey, Editor.

Abstract: The Earth has been struck by asteroids and comets (Near-Earth Objects, NEOs) many times throughout its history. The largest of these impacts have led to mass life extinctions, such as the one 65 million years ago which caused the disappearance of the dinosaurs. Humans are not dinosaurs and we possess technological tools that could deflect NEOs and avoid catastrophic impacts if we but develop the necessary plans and means. This report of the International Academy of Astronautics addresses the nature of the threat, expected future impacts, and the consequences of impacts from various size NEOs. It reviews current programs to detect, track, and characterize NEOs, and the future improvements required in order to take responsible and timely action. It identifies a number of techniques that could alter an incoming NEO’s orbit so as to avoid an impact. It addresses the organizational aspects that will have to be dealt with if a serious international capability is to be developed and employed to mitigate the threat. It then addresses behavioral factors and the sociological and psychological aspects of the threat and attempts at its mitigation before, during, and after an intercept attempt, whether successful or not. Lastly the report examines some of the principal international policy implications that must be dealt with if the world is to act in a timely, unified, and effective way with the very real threat due to NEOs. The report presents a number of principal findings and recommendations in each of these areas to be considered by the world community in addressing this truly international threat in a truly international manner. The International Academy of Astronautics could facilitate this process, beyond the hoped-for contributions of this report, by supporting the international community’s activities with international workshops; and through the technical, policy, social, and legal expertise of its members acting as consultants wherever beneficial.

2008: Asteroid Threats: A Call for Global Response. Association of Space Explorers International Panel on Asteroid Threat Mitigation.

Abstract: A report on the need to develop an international decision-making program for global response to Near Earth Object threats. Submitted for consideration and subsequent action by the United Nations, its goal is to assist the international community in preventing loss of life and property resulting from an asteroid impact on Earth. Within 10-15 years, the United Nations, through its appropriate organs, will face decisions about whether and how to act to prevent a threatened impact. To counter a threat of global dimension, information-sharing and communications capabilities must be harnessed to identify and warn society of hazardous NEOs. To prevent an actual impact, an international decision-making program, including necessary institutional requirements, must be agreed upon and implemented within the framework of the United Nations. This report, prepared by the Association of Space Explorers and its International Panel on Asteroid Threat Mitigation, proposes the following program for action.

2008: Natural Impact Hazard (Asteroid Strike) Interagency Deliberate Planning Exercise After Action Report. Directorate of Strategic Planning, Headquarters, United States Air Force.

Abstract: Air Force Future Concepts and Transformation Division (AF/A8XC) hosted a Natural Impact Event Interagency Planning Exercise, 4 Dec 2008, in Alexandria, Virginia. Twenty Seven Subject Matter Experts from across US Government, including DOD, DOE, DOS, DHS, NASA, and NSC participated in a single day tabletop exercise to explore whole of government response to an impending asteroid strike. The specific scenario involved a mythical asteroid, 2008 Innoculatus. It was a binary asteroid consisting of a 270m rocky rubble pile projected to strike the Gulf of Guinea and a 50m metallic companion asteroid projected to strike in the National Capital Region (NCR). The scenario was selected to maximize exposure to the diversity of threat (variation in size, composition, land/water strike), stress both national and international notification, and provide useful pre-planning should an actual effort need to be mounted against the asteroid Apophis when it has a small probability to pass through a gravitational keyhole in 2029 and perhaps return to strike the Earth seven years later in 2036. Participants were broken into two teams. The first team focused on disaster response and was told the asteroid was discovered 72 hrs from impact. The second team focused on deflection/mitigation and was told the asteroid had been discovered seven years from impact, and to design a strawman deflection plan using existing capabilities. The major insights from this exercise are presented.

Abstract: Near-Earth objects pose a serious and credible threat to humankind. Within 2 years after the date of enactment of this Act, the Director of the OSTP shall — (1) develop a policy for notifying Federal agencies and relevant emergency response institutions of an impending near-Earth object threat, if near-term public safety is at risk; and (2) recommend a Federal agency or agencies to be responsible for (A) protecting the United States from a near-Earth object that is expected to collide with Earth; and (B) implementing a deflection campaign, in consultation with international bodies, should one be necessary.

2008: Planetary Defense: Potential Mitigation Roles of the Department of Defense. Lt Col Peter Garretson, USAF, and Maj Douglas Kaupa, USAF. Air and Space Power Journal, 22:3, pp34-41, Fall 2008.

Abstract: The first and most important step in creating a planetary-defense plan is to find a home in the US government for such a program—preferably US STRATCOM. Other organizations would prove dysfunctional or suboptimal for US security. We would enhance our national-defense capabilities by working under STRATCOM auspices to pursue technology that might not be available or easily transitioned if developed by another agency. The United States doesn’t need a new dedicated agency or the inevitable duplication of effort that it would create. Once we decide upon a lead agency, we would then turn to developing a CONOPS, including the creation of interagency lines of communication. STRATCOM will not be the lone actor because mitigation policies will demand capabilities found in other organizations. After modifying existing search programs, we would identify the mitigation options that need development and testing. Massive extinctions have occurred in the past and can certainly occur again. Earth is not immune to collisions with asteroids and comets, but we can prepare for these events by establishing a solid planetary-defense plan.

Abstract: The collision of a moderately large asteroid or comet, also referred to as a Near-Earth Object (NEO) with Earth would have catastrophic consequences. To address this threat, we present a completely generalized hazardous NEO scenario timeline and associated spacecraft mission design architecture for hazardous NEO response that is intended to provide a means for designing missions to successfully deflect any arbitrary NEO predicted to have a significant likelihood of future collision with Earth. A generalized algorithm for optimizing the deflection of a NEO via a single impulse is presented and applied to the case of the asteroid Apophis, an asteroid that will closely approach Earth at an altitude of approximately 32000 km on April 13th, 2029 and may pass through a gravitational keyhole at that time, which would cause Apophis to collide with Earth in 2036. The case study performed on Apophis includes preliminary trajectory design that identifies the most favorable launch windows between 2008 and 2036 and computes how much spacecraft mass can be efficiently brought to rendezvous with the asteroid at each launch opportunity for two possible spacecraft launch vehicle and thruster combinations. The use of nuclear explosives as NEO deflection mechanisms is discussed in terms of the underlying theory, advantages, and disadvantages. The Apophis case study concludes with the presentation of optimal deflection results for the asteroid indicating by how much it can be optimally deflected at any time between the current time and shortly before the 2029 close approach. Trends in the optimal deflection data and the sensitivity of the optimal solutions are identified and discussed. An outline of a campaign of missions to Apophis for the purposes of characterization and, if necessary, deflection is presented. Paths for future research and algorithm development indicated by the current results are also discussed.

2007: On NEO Threat Mitigation. Jean-Luc Cambier and Frank Mead. Air Force Research Laboratory.

Abstract: It is well known that Near-Earth Objects (NEO) and other celestial bodies can be a threat to human existence and civilization. While impacts with large objects occur with very low probability, the consequences can be so catastrophic and irremediable that a program to alleviate this type of threat would seem a very prudent decision. Currently, NASA has been tasked with detecting and characterizing NEOs. However, the role of mitigating these threats is yet to be defined, and may be suitable for USAF responsibility. Mitigation approaches are varied and require further study, but of particular concern are the most difficult scenarios of interception, involving objects with large mass and little advance warning. Although threat mitigation will require important decisions, authorizations, multi-agency coordination and likely international collaboration, some essential long-term planning steps are required to develop and mature key technologies in order to defeat these threats. These steps can be part of an overall long-term strategy for space exploration and utilization that can be part of a global peace-time DOD activity, and that can also greatly increase the welfare of mankind.

Abstract: This work documents the advancements in MSFC threat modeling and mitigation technology research completed since our last major publication in this field. Most of the work enclosed here are refinements of our work documented in NASA TP-2004-213089. Very long development times from start of funding (10-20 years) can be expected for any mitigation system which suggests that delaying consideration of mitigation technologies could leave the Earth in an unprotected state for a significant period of time. Fortunately there is the potential for strong synergy between architecture requirements for some threat mitigators and crewed deep space exploration. Thus planetary defense has the potential to be integrated into the current U.S. space exploration effort. The number of possible options available for protection against the NEO threat was too numerous for them to all be addressed within the study; instead, a representative selection were modeled and evaluated. A summary of the major lessons learned during this study is presented, as are recommendations for future work.

2007: Near-Earth Object Survey and Deflection Analysis of Alternatives. NASA Report to Congress. March, 2007.

Abstract: The study team assessed a series of approaches that could be used to divert a NEO potentially on a collision course with Earth. Nuclear explosives, as well as non-nuclear options, were assessed. • Nuclear standoff explosions are assessed to be 10-100 times more effective than the non-nuclear alternatives analyzed in this study. Other techniques involving the surface or subsurface use of nuclear explosives may be more efficient, but they run an increased risk of fracturing the target NEO. They also carry higher development and operations risks. • Non-nuclear kinetic impactors are the most mature approach and could be used in some deflection/mitigation scenarios, especially for NEOs that consist of a single small, solid body. • “Slow push” mitigation techniques are the most expensive, have the lowest level of technical readiness, and their ability to both travel to and divert a threatening NEO would be limited unless mission durations of many years to decades are possible. • 30-80 percent of potentially hazardous NEOs are in orbits that are beyond the capability of current or planned launch systems. Therefore, planetary gravity assist swingby trajectories or on-orbit assembly of modular propulsion systems may be needed to augment launch vehicle performance, if these objects need to be deflected.

2006: 2006 Near-Earth Object Survey and Deflection Study. NASA Headquarters Office of Program Analysis and Evaluation. December 28, 2006.

Abstract: In the 2005 Budget Authorization Act, the U.S. Congress directed the NASA Administrator to provide an analysis of alternatives to detect, track, catalogue, and characterize potentially hazardous near-Earth objects (NEO). Congress required that the Administrator submit a program by December 28, 2006 to survey 90% of the potentially hazardous objects measuring at least 140 meters in diameter by the end of 2020. In addition, the legislation required the Administrator to submit an analysis of alternatives that NASA could employ to divert an object on a likely collision course with Earth. A study team, led by the Office of Program Analysis and Evaluation (PA&E), derived requirements and figures of merit from the Act, and used these factors to evaluate the alternatives. The team developed a range of options from public and private sources and then analyzed their capabilities, levels of performance, life-cycle costs, schedules, and, development and operations risks. This document presents the detailed results of these analyses.

2006: Critical System Engineering Analysis for Planetary Defense. Warren G. Greczyn. Doctoral Dissertation, George Washington University.

Abstract: The deflection of asteroid and comet Earth-impact threats is studied, and the kinematic requirements for threat object deflections that prevent Earth impact are characterized. This paper uses direct solutions of Kepler’s equation coupled to an Earth gravitational model to determine threat object pre- and post-deflection orbital behaviors. The primary defense scenario considered is the deflection of asteroid threats through the application of a 1 cm/s velocity change, a level generally accepted by the planetary defense community as achievable in the near term. Threat displacement at Earth passage is assessed as the primary metric of deflection success. Key characteristics of defense system performance are analyzed, including optimal selection of the timing, direction, and required directional accuracy of successful deflections, along with duration of the threat engagement window and the effects of variations in deflection velocity. Deflected threat behaviors are developed parametrically for a representative threat set that spans the full range of observed hazardous threat orbits. The resulting trends are presented in conjunction with a broad-based treatment of the threat itself, including its origins, populations, general behaviors, and the history of both Earth impact and of efforts to develop an understanding of potential impactors. This is done with the aim of capturing the motivation for planetary defense in general and of making this paper a more complete and useful tool in the design of planetary defense systems, missions, and programs.

2005: Mission Planning for the Mitigation of Hazardous Near Earth Objects. Brent William Barbee. Masters Thesis, University of Texas at Austin.

Abstract: The problem of mitigating the threat posed by hazardous Near Earth Objects (NEOs) is examined and addressed. The concept of hazardous NEO mitigation is presented, along with background on the NEO population and its characteristics. A set of philosophies and hierarchies of decision-making principles and protocols are devised to aid in the design of spacecraft missions to mitigate threatening NEOs, leading to the construction of a generalized approach to NEO mitigation mission planning. The orbital mechanics involved in rendezvousing with a NEO and performing proximity operations in its vicinity for the purposes of science and deflection system deployment are studied. The need and opportunity to perform rigorous asteroid/comet science in the context of NEO mitigation missions is also discussed. The construction of optimal NEO deflection maneuvers is also examined and the particular case of impulsive deflection maneuvers is given more thorough treatment. NEO deflection systems, both practical and theoretical, are analyzed and discussed. In particular, the standoff nuclear detonation deflection method is examined in detail. A case study is conducted in which a fictitious threatening Near Earth Asteroid (NEA) is mitigated using the techniques developed within.

2005: A Call to (Considered) Action. Russell L. Schweickart, Chairman, B612 Foundation. National Space Society International Space Development Conference, Washington, DC, May 20, 2005.

Abstract: The purpose of this paper is to call upon the Congress of the United States to initiate, via the National Research Council or other appropriate body, a formal analysis of the circumstances presented by the close encounter between the Earth and asteroid 2004MN4 in April 2029, and the potential for a subsequent collision with Earth in 2036. Informal analysis indicates that the accuracy of our knowledge of the asteroid?s trajectory using optical and radar tracking is likely to be inadequate to make a timely deflection decision in the improbable event that one should be needed. Should this claim prove to be correct after formal analysis serious consideration should be given to placing a radio transponder on 2004MN4, perhaps as one of several scientific objectives. This mission should be launched in the near future in order to provide adequately accurate trajectory information about the asteroid by 2014, the approximate date by which a deflection mission decision, if required, would have to be made.

Abstract: There exists an infrequent, but significant hazard to life and property due to impacting asteroids and comets. There is currently no specific search for long-period comets, smaller near-Earth asteroids, or smaller short-period comets. These objects represent a threat with potentially little or no warning time using conventional ground-based telescopes. These planetary bodies also represent a significant resource for commercial exploitation, long-term sustained space exploration, and scientific research. The Comet/Asteroid Protection System (CAPS) is a future space-based system concept that provides permanent, continuous asteroid and comet monitoring, and rapid, controlled modification of the orbital trajectories of selected bodies. CAPS would expand the current detection effort to include long-period comets, as well as small asteroids and short-period comets capable of regional destruction. A space-based detection system, despite being more costly and complex than Earth-based initiatives, is the most promising way of expanding the range of detectable objects, and surveying the entire celestial sky on a regular basis. CAPS would provide an orbit modification system capable of diverting kilometer class objects, and modifying the orbits of smaller asteroids for impact defense and resource utilization. This Technical Memorandum provides a compilation of key related topics and analyses performed during the CAPS study, which was performed under the Revolutionary Aerospace Systems Concepts (RASC) program, and discusses technologies that could enable the implementation of this future system.

2004: Protecting Earth from Asteroids and Comets: An AIAA Position Paper. American Institute of Aeronautics and Astronautics, October, 2004.

Abstract: AIAA recommends that the following steps be taken to protect the Earth from NEO impacts: • Create an organization within the U.S. government responsible for planetary defense. • Extend the Spaceguard Survey, currently focused on finding and cataloging 1-km class objects and larger, to include finding and cataloging 100-m-class NEOs and larger. • Develop and fund ground-based techniques as well as missions to several asteroids to gather information that contributes to designing deflection missions. • Conduct mission design studies to characterize requirements for short-, medium-, and long-term missions. • Conduct flight tests to demonstrate our ability to change a NEO’s orbit. • Sponsor research to assess the political, social, legal, and disaster relief consequences of a serious NEO threat, mitigation effort, or possible impact.

Abstract: The threat posed by NEOs should be taken very seriously. It is well within humanity’s ability to effectively defend itself against this threat. Development of the necessary technologies would also offer considerable synergy with NASA’s other missions aimed at understanding the universe and exploring space. The planetary defense mission is also one for which NASA is uniquely suited and could potentially offer the Agency a goal that both fires the public imagination and creates a sense of urgency comparable to that during the Apollo program in the 1960’s. The goal is to persuade those in positions of authority to continue the efforts presented here.

2004: The League of Extraordinary Machines: A Rapid and Scalable Approach to Planetary Defense against Asteroid Impactors. NASA Institute for Advanced Concepts (NIAC) Phase I Final Report, April 30, 2004.

Abstract: A new approach to mitigate and protect against planetary impactor events is proposed. The primary objective of this systems concept is to apply small perturbations to Near-Earth Objects (NEOs) in an attempt to divert them from their path toward Earth impact. Unlike past proposals from other individuals or organizations, this project concept proposes a rapid and scalable solution consisting of tens, hundreds, or thousands of small, nearly identical spacecraft that will intercept the target body and conduct mass driver/ejector operations to perturb the target body’s trajectory to the point where an impact with Earth can be avoided. There have been many ideas woven together to develop the asteroid concept presented herin. From mass driver technology to notions of swarm intelligence, various technologies and approaches have been combined to develop a potentially unique approach to planetary defense against asteroids and comets.

2003: Decision Model for Potential Asteroid Impacts. Brad R. Blair. Research Paper EB560. Decision Analysis Division of Economics and Business, Colorado School of Mines.

Abstract: Research in asteroid detection and orbital characterization has identified a new class of possible natural disaster. Asteroids are the only known type of natural disaster that could potentially destroy civilization. The societal importance of asteroid detection is assumed to be high, given the destructive capacity of Potentially Hazardous Asteroids (PHAs). This paper offers a decision analysis framework to aid in decision making regarding what to do when confronted by a particular PHA of a given size with a given probability of impact. Three decisions are modeled: (1) Study the PHA with a large telescope to further refine orbital estimates; (2) Send a small reconnaissance spacecraft to survey the PHA; and/or (3) Send a large spacecraft mission to disrupt the orbit of the PHA using nuclear explosives.

2003: Study to Determine the Feasibility of Extending the Search for Near-Earth Objects to Smaller Limiting Diameters. Report of the Near-Earth Object Science Definition Team, NASA Office of Space Science.

Abstract: The Team evaluated the capability and performance of a large number of ground-based and space-based sensor systems in the context of a cost/benefit analysis. Based on this analysis, the Team recommends that the next generation search system be constructed to eliminate 90% of the risk posed by collisions with sub-kilometer diameter potentially hazardous objects (PHOs). Such a system would also eliminate essentially all of the global risk remaining after the Spaceguard efforts are complete in 2008. The implementation of this recommendation will result in a substantial reduction in risk to a total of less than 30 casualties per year plus attendant property damage and destruction. A number of search system approaches identified by the Team could be employed to reach this recommended goal, all of which have highly favorable cost/benefit characteristics. The final choice of sensors will depend on factors such as the time allotted to accomplish the search and the available investment.

Abstract: For the first time in human history, we have the potential to protect ourselves from a catastrophe of truly cosmic proportions. If we do not act now, and we subsequently learn too late of an impending collision against which we cannot defend, it will not matter who should have moved to prevent the catastrophe . . . only that they failed to do so when they had the opportunity to prevent it. To address this potential threat, we strongly urge that each of you take steps within your respective committee jurisdictions to implement immediately the following recommendations: 1. NEO Detection: Expand and enhance this nation’s capability to detect and to determine the orbits and physical characteristics of NEOs. 2. NEO Exploration: Expand robotic exploration of asteroids and Earth-approaching comets. Obtain crucial follow up information on NEOs (required to develop an effective deflection capability) by directing that U.S. astronauts again leave low-Earth orbit . . . this time to protect life on Earth. 3. NEO Contingency and Response Planning: Initiate comprehensive contingency and response planning for deflecting any NEO found to pose a potential threat to Earth.

2000: Using Lasers in Space: Laser Orbital Debris Removal and Asteroid Deflection. Jonathan W. Campbell. Occasional Paper No. 20, Center for Strategy and Technology, Air University.

Abstract: Orbital debris in low-Earth orbit ranging in size from 1 to 10 centimeters (cm) in diameter, poses a significant problem for space vehicles. While this debris can he detected, it cannot he tracked with sufficient reliability to permit spacecraft to avoid these objects. Such debris can cause catastrophic damage even to a shielded spacecraft. Given the technological advances associated with adaptive optics, a ground-based pulsed laser could ablate or vaporize the surface of orbital debris, thereby producing enough cumulative thrust to cause debris to reenter the atmosphere. One laser facility could remove all of the one-ten centimeter debris in three years or less. This study proposes that the United States develop a technology demonstration of this laser space propulsion in order to implement a system for removing debris from earth orbit. The cost of this proposed demonstration is favorable in comparison with the typical costs for spacecraft operations. Orbital debris is not the only form of ?space junk? that is deleterious to the Earth. Since collisions with asteroids have caused major havoc to the Earth?s biosphere on several occasions in the geological past, the reality is that the Earth will probably experience another impact in the future. For this reason, this study also considers the possibilities of scaling up a system for removing orbital debris to a system that could prevent these catastrophic collisions if we have sufficient warning.

1999: SHIELD: A Comprehensive Earth Protection System. R. E. Gold. Phase I Report to the NASA Institute for Advanced Concepts, May 28, 1999.

Abstract: A complete planet impact hazard protection system must address the full range of problems including the detection of potentially threatening bodies, the assessment and characterization of those threats, and the protection of Earth from the threat by deflection or fragmentation. The basic concept of SHIELD was developed under a grant from the NASA Institute for Advanced Concepts in 1999. SHIELD is a four-fold defense system with: 1) Sentry, to accurately identify threatening bodies very early — years before impact; 2) Scout, to assess the threat and select an approach to protect the Earth; 3) Soldier to mitigate the threat if it can not be eliminated by improved knowledge of its orbit; and 4) the Earth Control Center to organize, coordinate, and operate the other three components. The 1999 SHIELD report is still the only comprehensive analysis of an end-to-end Earth Protection system done to date.

1996: ORION: Clearing Near-Earth Space Debris Using a 20-kW, 530-nm, Earth-Based, Repetitively Pulsed Laser. C. R. Phipps, Laser and Particle Beams 14 no. 1 pp. 1-44 (1996). Updated February 2007. See also Using Lasers in Space: Laser Orbital Debris Removal and Asteroid Deflection.

Abstract: Almost a million pieces of debris have been generated by 35 years of spaceflight, and now threaten long-term space missions. The most economical solution to this problem is to cause space debris items to re-enter and burn up in the atmosphere. For safe handling of large objects, it is desired to do this on a pre-computed trajectory. Due to the number, speed and spacial distribution of the objects, a highly agile source of mechanical impulse, as well as a quantum leap in detection capability are required. The system we propose here uses a ground-based laser system and active beam phase error correcting beam director to provide the impulse, together with a new, computer-intensive, very-high-resolution optical detection system to locate objects as small as 1 cm at 500km range. Illumination of the objects by the repetitively-pulsed laser produces a laser-ablation jet which gives the impulse to de-orbit the object. A laser of just 20 kW average power and state-of-the-art detection capabilities could clear near-Earth space below 1000 km altitude of all space debris larger than 1 cm but less massive than 100 kg in about 4 years, and all debris in the threatening 1 to 20-cm size range in about 2 years of continuous operation. The ORION laser would be sited near the Equator at a high altitude location [e.g., the Uhuru site on Kilimanjaro], minimizing turbulence correction, conversion by stimulated Raman scattering, and absorption of the 530-nm wavelength laser beam. ORION is a special case of Laser Impulse Space Propulsion (LISP), studied extensively by Los Alamos and others over the past four years.

1996: Planetary Defense: Catastrophic Health Insurance for Planet Earth. John M. Urias, et. al. Study for Air Force 2025.

Abstract: Collectively as a global community, no current viable capability exists to defend the Earth-Moon system (EMS) against a large Earth-crossing object (ECO), leaving its inhabitants vulnerable to possible death and destruction of untold proportion and even possible extinction of the human race. In this regard, a planetary defense system (PDS) capability should be resourced, developed, and deployed. At this time Planetary Defense is not an assigned or approved mission of the Department of Defense or the Air Force. Such a system would consist of a detection subsystem, command, control, communications, computer, and intelligence (C4I) subsystem and a mitigation subsystem. There are many potential variations of these subsystems which, with advances in novel technologies, will be available by 2025 to develop a credible PDS. We propose a three-tier system developed sequentially in time and space. Such a system would serve not only as a means to preserve life on earth, but also help to unite the global community in a common effort that would promote peaceful cooperation and economic prosperity as related spin-offs and dual uses of novel technologies evolve.

1995: Adroitly Avoiding Asteroids: Clobber, Coax or Consume? Alan J. Willoughby and Melissa L. McGuire. Space Manufacturing 10: Pathway to the High Frontier. Proceedings of the Twelfth SSI-Princeton Conference, May 4-7, 1995, pp. 103-113.

Abstract: The idea of turning threatening asteroids into useful products to prevent them from colliding with Earth has been reinforced by recent analysis of the tremendous profit potential of their precious metals. “Consumption” is a third major option for preventing asteroid disasters. The other options are to use nuclear weapons (“clobber”) or to gradually propel (“coax”) the threatening body into a slightly different orbit. Our objective is to put the asteroid threat, it’s potential solutions and space resources into a clear perspective. Even the better solutions have some uncertainty; and none seems universally applicable. Our most urgent recommendation is to robotically explore every type of near earth object (NEO). Based on our current limited knowledge, however, we believe that: (1) nuclear weapons approaches entail an unacceptable risk of compounding the threat; (2) propulsive remedies must often use extraterrestrial materials as propellant; (3) propulsive remedies must be applied carefully to deal with spinning and fracturing the asteroids; (4) consumptive remedies may not be well motivated by profits; (5) consumptive remedies beg the question of propulsive deflection; and (6) space resources may play their biggest role in providing the infrastructure for an asteroid protection. For now, we strongly lean towards “coaxing” threatening objects off harm’s path.

1994: Preparing for Planetary Defense: Detection and Interception of Asteroids on Collision Course with Earth. White Paper on Planetary Defense of the Air University Spacecast 2020 Study Group.

Abstract: This paper first investigates the magnitude and frequency of the threat by reviewing the extensive research by the scientific community on this subject over the last several years. Then it looks at some of the technologies and methods for detecting, cataloging, and tracking planetary debris objects that may be on a collision course with Earth. The focus then shifts to issues associated with mitigation efforts and technology for interception and deflection or destruction of these objects. Finally, it examines the potential cost and benefits of a Department of Defense (DoD) role in an international planetary defense effort.

1990: Dealing with the Threat of an Asteroid Striking the Earth: An AIAA Position Paper. American Institute of Aeronautics and Astronautics, April, 1990.

Abstract: Although the probability of such an occurrence is very small, its consequences (i.e., the casualty rate) could be enormous. The risk to Earth’s inhabitants is therefore finite, warranting action to improve and expand our ability to detect Earth orbit-crossing objects and to analyze and predict their orbits. It would also be useful to explore methods and technologies for deflecting or destroying any such objects that are predicted to impact the Earth and to alter their orbits sufficiently to preclude impact.

Additional papers, presentations, and videos on planetary defense can be found at these links:

Planetary Defense Home Page.