Overall results of the SMPAG work package on mission scenarios definition in response to the 2025 Planetary Defense Conference Hypothetical Asteroid Impact Threat Scenario

The members of the Space Mission Planning Advisory Group (SMPAG) per- formed an asteroid impact simulation exercise over a medium size asteroid with impact chances on 24 April 2041, in preparation for the 2025 Planetary Defense Conference. The exercise was articulated on two different simulation periods lasting, respectively, two months and a half and four months. In the first period, Epoch 1, the asteroid impact probability grew from 1.6% to 10% and was played in real time. A preliminary assessment of the required ac- tions that would need to be implemented and a set of recommendations were provided at a plenary SMPAG session held on 10 October 2024. Epoch 2 was simulated after the fast flyby of a reconnaissance mission by the asteroid in April 2028 that allowed refining the asteroid size, and impact location. An assessment of the decisions that were required and the feasible mission options was performed in order to facilitate a recommendation by the SM- PAG plenary. Based on a trade-off of several deflection mission strategies, mission options included kinetic impactors, ion-beam deflection and nuclear Preprint submitted to Acta Astronautica January 9, 2026 Revised manuscript (unmarked, editable source file) Click here to view linked