Origins, Worlds, and Life A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (2022) / Chapter Skim
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18 Planetary Defense: Defending Earth through Applied Planetary Science Planetary defense is an international cooperative enterprise aimed at providing protection to the nations of the world from devastating asteroid and comet impacts. By using the knowledge and tools gained through planetary science and exploration, it is now possible to develop realistic and cost-effective detection and mitigation strategies against these natural disasters.
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being struck by a larger asteroid or comet is small, the consequences of such a collision are so serious that prudence dictates that society assess the nature of the threat and be prepared to respond. To date, numerous NEOs have been found, mainly by U.S.-funded surveys, and cataloged by NASA (see Figures.
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The public has consistently ranked planetary defense (henceforward, "PD") as one of NASA's top priorities, supported in 2019 by 62 percent of poll respondents (Pew Research Center, 2019)
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developing the Near-Earth Object Surveyor (NEO Surveyor) infrared space telescope to complete the congressionally mandated 140 m NEO survey; a 2026 launch is planned.
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to lead such activities and directs NSF to provide support. The plan's five strategic goals underpin the nation's effort to enhance preparedness for dealing with the threat of future NEO impacts (NSTC 2018)
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medium to large (>140 m in diameter) NEOs, optimizes the use of facilities and trained personnel, and obtains maximum benefit from the lessons provided by other current space-based detection tools, e.g., NEOWISE.
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Finding: The first priority in planetary defense is early detection, tracking, and characterization, of NEOs, whose impact may cause widespread regional damage. NEO Surveyor, in development by NASA for this purpose, is the most timely and effective means to complete the survey goal of detecting 90 percent of NEOs greater than 140 m in diameter.
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Finding: The data pipeline for detection, tracking, impact assessment, and reporting to the public will be tested by the ten-fold increase in NEO detection rates when VCRO and NEO Surveyor become operational. Both facilities will benefit from coordinated rehearsals and operational readiness reviews well-prior to achieving their full operational capabilities.
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NEO Characterization Policy makers, scientists, and engineers require knowledge of the physical characteristics of a NEO to determine the safest and most efficient measures to deflect a threatening object away from Earth. The most important factor in NEO characterization is determining the object's orbit.
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Finding: Because NEOs are best observed closest to Earth, when optically bright (usually soon after discovery) , ground-based characterization efforts depend upon obtaining scarce telescope observing time, along with availability of favorable observing geometry and sky conditions.
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Finding: Meteorites provide samples of NEOs for investigation in state-of-the-art laboratories, adding to our understanding of compositional and mechanical properties and variations among the NEO population. The rapid recovery of meteorite falls linked to atmospheric entry events is uniquely valuable to combined meteorite and bolide studies.
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twice as many NEOs as GSSR (Naidu et al.
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Finding: NASA and NSF have largely informally cooperated at shared-use facilities, such as Arecibo and GBT, by leveraging their grantees and contractors as intermediaries. A more formalized agreement is required to ensure appropriate collaborations for planetary defense.
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it passes by on either its inbound or outbound leg. This type of flyby space mission would not require the observing spacecraft to leave Earth's gravitational influence.
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in November 2019. The second and third objectives, "Establish an integrated suite of computational tools for modeling NEO impact risks and mitigation techniques" and "Exercise, evaluate, and continually improve modeling and analysis capabilities" are currently in development within the MWG.
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making and to enhance public awareness in a NEO emergency. While early efforts have focused on code comparisons and probabilistic risk assessments for specific problems of interest, future work will include validation and verification of computational tools against experimental and observational data.
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and damage models representing asteroidal material, and simulation of a wider range of three-dimensional NEO shapes. Further, new and rapidly developing computational capabilities are now regularly incorporated into both kinetic and nuclear deflection modeling.
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and the University of Rochester's OMEGA laser. Experiments also frequently reveal fruitful new research directions.
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Finding: Integrated modeling assessment across all aspects of planetary defense, including characterization data, modeling parameters, validation data, calculation results, and analysis tools, using uncertainty-aware methods, is needed to establish an operations-ready suite of computational tools for evaluating NEO impact risks and mitigation techniques. Recommendation: To achieve the modeling, prediction, and information integration objectives listed under Goal 2, NASA should allocate resources for the establishment of a planetary defense modeling pipeline, including support for collaboration between modeling teams and software developers to establish initial requirements.
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Finding: The recommendation of the 2019 NASEM report, Finding Hazardous Asteroids Using Infrared and Visible Wavelength Telescopes, remains valid and important to follow for the next decade and beyond: "Missions meeting high-priority planetary defense objectives should not be required to compete against missions meeting high-priority science objectives." Double Asteroid Redirection Test Mission NASA's DART mission is scheduled to impact the 160-m asteroid Dimorphos in 2022, demonstrating kinetic impact technology as one approach to accomplish asteroid deflection. ESA's Hera mission is scheduled to rendezvous with the Didymos-Dimorphos system in 2026, providing further insight into the results of DART's kinetic impact demonstration.
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Both mission types would collect information designed to fulfill planetary defense objectives, particularly to inform the development and implementation of mitigation strategies and techniques. Significantly, the RMA study concluded that increased detection and characterization of the NEO population is critical to reducing risks and ensuring successful mitigation, given the diversity of physical characteristics among these objects.
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mitigation technology requires a balance between generating an adequate amount of deflection/disruption without causing deleterious results (e.g., unwanted disruption or ineffective deflection)
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FIGURE 18.4 Numerical results from simulating deflection capabilities of various techniques across a variety of asteroid sizes following fifteen different Earth-impacting orbits. Kinetic impact (KI)
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• A kinetic impact mission on a smaller NEO and at a higher closing speed than DART to acquire experience needed for more challenging mitigation missions. • A slow-push/pull mitigation demonstration, such as ion beam deflection, to develop several different technologies that may be employed against future hazardous objects.
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• NEO Reconnaissance Technologies: Development of these technologies is needed to make necessary measurements during either flyby or rendezvous missions, and are focused on determining key NEO physical characteristics that will inform the required subsequent mitigation efforts given the available warning time. Such technologies include spacecraft systems (e.g., high speed gimbals)
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Finding: Promising new technologies for both characterization and mitigation demonstration missions could be tested upon relevant NEOs. Technologies such as those for guidance, navigation, and control (GNC)
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several rapid response strategies exist which could be tested on planetary defense demonstration missions. Finding: A study of specific rapid-response strategies as part of planetary defense demonstration missions would help assess what preparations and resources would enable a launch 1, 2, 3, or 4 years from time of alert.
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NEO IMPACT EMERGENCY PROCEDURES AND ACTION PROTOCOLS Devastating NEO impacts are low-probability, high-consequence events that may result in extensive loss of life, and warrant appropriate levels of preparedness. As in the case of hurricanes and other natural disasters, damage prevention depends on developing and exercising response protocols to support reliable communications, sound decision-making, and employment of effective mitigation measures.
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possesses sufficiently mature telescope and space operations technologies to provide two of the three elements necessary to prevent a NEO impact. First, NASA is expanding its NEO search abilities and, with its U.S.
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Harris, A W., Chodas, P
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PDCO Planetary Defense Coordination Office, NASA.
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