Physical and infrastructure modeling for the 2015 PDC asteroid threat exercise

The 2015 Planetary Defense Conference (2015 PDC) was held in Frascati, Italy on April 13-17 by the International Academy of Astronautics (IAA). In addition to customary technical sessions, we performed the first week-long threat exercise designed to simulate and examine the process of decision making that would accompany the discovery and response to an asteroid on a collision course with Earth. Our role in the exercise was to develop and present a plausible scenario that would be of interest to as many participants as possible while considering the broad diversity in technical expertise, approach, values, missions, and national affiliations of the conference attendees. Moreover, we strove to present a reasonable sequence of events spanning several years that would provide many opportunities for collective decision making under uncertainty by parties likely to have conflicting interests. In order to hold the attention of the participants throughout the week we tried to create a scenario that would be as dramatic as possible - including “cliffhangers” and unexpected turns of events - but without sacrificing realism. This allowed us to discuss a wide range of potential responses, including kinetic and nuclear deflection, and potential outcomes, including tsunami-forming ocean impacts, crater-forming land impacts, and airbursts by objects over a large size range. In addition to creating the scenario, members of our team served on an expert panel in a role-playing exercise that included participants acting as world leaders of nations, both directly and indirectly affected members of the public in at-risk areas, and the media. This paper summarizes the exercise, focusing on physical and infrastructure modeling. The exercise spanned the entire week, with daily “injects” (or updates) of new observed data about what was currently known on the imaginary date. We presented models of potential physical effects and resulting infrastructure damage, with emphasis on the uncertainties. Seven updates spanned most of the time between when the asteroid (dubbed “2015 PDC”) was discovered on April 13, 2015, and its impact date of September 3, 2022. Information about the orbit and technical response options were presented as a set of faux press releases that were made available to participants prior to each briefing. The scenario was based on an actual calculated orbit to provide as much realism as possible. The physical effects at each stage were predicted by using simulations for airburst and tsunami generation, and a shallow water model for tsunami propagation. Maps were generated using tools developed for the National Infrastructure Simulation and Analysis Center (NISAC), and were presented by expert panelists as part of a mock press briefing at each inject. We present the contents of those press briefings and put them into context with the threat exercise.