Clemens Rumpf

On the influence of impact effect modelling for global asteroid impact risk distribution

The collision of an asteroid with Earth can potentially have significant consequences for the human population. The European and United States space agencies (ESA and NASA) maintain asteroid hazard lists that contain all known asteroids with a non-zero chance of colliding with the Earth in the future. Some software tools exist that are, either, capable of calculating the impact points of those asteroids, or that can estimate the impact effects of a given impact incident. However, no single tool is available that combines both aspects and enables a comprehensive risk analysis. The question is, thus, whether tools that can calculate impact location may be used to obtain a qualitative understanding of the asteroid impact risk distribution. To answer this question, two impact risk distributions that control for impact effect modelling were generated and compared. The Asteroid Risk Mitigation Optimization and Research (ARMOR) tool, in conjunction with the freely available software OrbFit, was used to project the impact probabilities of listed asteroids with a minimum diameter of 30 m onto the surface of the Earth representing a random sample (15% of all objects) of the hazard list. The resulting 261 impact corridors were visualized on a global map. Furthermore, the impact corridors were combined with Earth population data to estimate the “simplified” risk (without impact effects) and “advanced” risk (with impact effects) associated with the direct asteroid impacts that each nation faces from present to 2100 based on this sample. The relationship between risk and population size was examined for the 40 most populous countries and it was apparent that population size is a good proxy for relative risk. The advanced and simplified risk distributions were compared and the alteration of the results based on the introduction of physical impact effects was discussed. Population remained a valid proxy for relative impact risk, but the inclusion of impact effects resulted in significantly different risks, especially when considered at the national level. Therefore, consideration of physical impact effects is essential in estimating the risk to specific nations of the asteroid threat.

The global impact distribution of Near-Earth objects

Asteroids that could collide with the Earth are listed on the publicly available Near-Earth object (NEO) hazard web sites maintained by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). The impact probability distribution of 69 potentially threatening NEOs from these lists that produce 261 dynamically distinct impact instances, or Virtual Impactors (VIs), were calculated using the Asteroid Risk Mitigation and Optimization Research (ARMOR) tool in conjunction with OrbFit. ARMOR projected the impact probability of each VI onto the surface of the Earth as a spatial probability distribution. The projection considers orbit solution accuracy and the global impact probability. The method of ARMOR is introduced and the tool is validated against two asteroid-Earth collision cases with objects 2008 TC3 and 2014 AA. In the analysis, the natural distribution of impact corridors is contrasted against the impact probability distribution to evaluate the distributions’ conformity with the uniform impact distribution assumption. The distribution of impact corridors is based on the NEO population and orbital mechanics. The analysis shows that the distribution of impact corridors matches the common assumption of uniform impact distribution and the result extends the evidence base for the uniform assumption from qualitative analysis of historic impact events into the future in a quantitative way. This finding is confirmed in a parallel analysis of impact points belonging to a synthetic population of 10,006 VIs. Taking into account the impact probabilities introduced significant variation into the results and the impact probability distribution, consequently, deviates markedly from uniformity. The concept of impact probabilities is a product of the asteroid observation and orbit determination technique and, thus, represents a man-made component that is largely disconnected from natural processes. It is important to consider impact probabilities because such information represents the best estimate of where an impact might occur.

Population vulnerability models for asteroid impact risk assessment

An asteroid impact is a low probability event with potentially devastating consequences. The Asteroid Risk Mitigation Optimization and Research (ARMOR) software tool calculates whether a colliding asteroid experiences an airburst or surface impact and calculates effect severity as well as reach on the global map. To calculate the consequences of an impact in terms of loss of human life, new vulnerability models are derived that connect the severity of seven impact effects (strong winds, overpressure shockwave, thermal radiation, seismic shaking, ejecta deposition, cratering, and tsunamis) with lethality to human populations. With the new vulnerability models, ARMOR estimates casualties of an impact under consideration of the local population and geography. The presented algorithms and models are employed in two case studies to estimate total casualties as well as the damage contribution of each impact effect. The case studies highlight that aerothermal effects are most harmful except for deep water impacts, where tsunamis are the dominant hazard. Continental shelves serve a protective function against the tsunami hazard caused by impactors on the shelf. Furthermore, the calculation of impact consequences facilitates asteroid risk estimation to better characterize a given threat, and the concept of risk as well as its applicability to the asteroid impact scenario are presented.

Asteroid impact effects and their immediate hazards for human populations

A set of 50,000 artificial Earth impacting asteroids was used to obtain, for the first time, information about the dominance of individual impact effects such as wind blast, overpressure shock, thermal radiation, cratering, seismic shaking, ejecta deposition, and tsunami for the loss of human life during an impact event for impactor sizes between 15 and 400 m and how the dominance of impact effects changes over size. Information about the dominance of each impact effect can enable disaster managers to plan for the most relevant effects in the event of an asteroid impact. Furthermore, the analysis of average casualty numbers per impactor shows that there is a significant difference in expected loss for airburst and surface impacts and that the average impact over land is an order of magnitude more dangerous than one over water.

Global impact risk of known asteroids

Asteroids that could collide with the Earth are listed on the publicly available Near Earth Object (NEO) hazard web sites maintained by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). The risk of 69 potentially threatening NEOs that produce 261 dynamically distinct impact instances, or Virtual Impactors (VIs), has been calculated using the Asteroid Risk Mitigation and Optimization Research (ARMOR) tool. ARMOR calculates the impact risk in terms of expected casualties based on three factors: impact probability, exposure and vulnerability. First, the impact probability of each VI is projected onto the surface of the Earth as a spatial probability distribution. The projection considers orbit solution accuracy and the global impact probability. Second, the global population distribution is introduced and represents the exposure to the hazard. Finally, the vulnerability of the population to the physical impact effects produced by a colliding asteroid is calculated. Impact effects are calculated based on asteroid size, impact speed and impact angle and the effects are: crater formation, thermal radiation, seismic shaking, overpressure shock wave, strong winds and the deposition of an ejecta blanket. Population vulnerability is determined based on the severity of the impact effects at a given distance from the impact site. Factoring together impact probability, exposure and vulnerability allows calculation of the risk for each VI as well as the combined risk of the 69 asteroids. To account for the uncertainty in the impact effect models, ARMOR produces three scenarios that represent the least harmful, the expected and the worst case outcomes. Because the risk calculation is dependent on the current impact probability, the risk calculation is subject to significant variability based on the availability of new asteroid observations. The calculated risk expresses the current best estimate of expected casualties that are associated with each asteroid. The method has the potential to form the basis of a new impact hazard threat scale similar to the Torino or Palermo scale. The results are presented in the form of global spatial risk distributions and as quantitative analysis.

Enhancing microelectronics education with large-student projects: Using the example of the University of Southampton Small Satellite

This paper discusses the benefits of using large-scale projects, involving many groups of students with different backgrounds, in the education of undergraduate microelectronics engineering students. The benefits of involving students in large, industry-like projects are first briefly reviewed. The organisation of undergraduate programmes is presented, and it is described how students can be involved in such large projects, while maintaining compatibility with undergraduate programmes. The generic discussion is illustrated with an example of the University of Southampton Small Satellite (UoS3) project, which has been running for two academic years and involved a number of students to date. It is discussed how the work on a project can be split between different student groups so that they can be assessed on it. Definition of interfaces between different groups, as well as how they are managed in the UoS3 project, are described. The difficulties that large, student-run projects are likely to face are mentioned and recommendations about the structuring of degree programmes to amend them to large projects, are made. Lastly, conclusions about the applicability and benefits of small satellite projects to undergraduate education in electronics are drawn.