Speaker
Description
The 2025 Planetary Defense Conference (PDC) hypothetical asteroid impact threat exercise is being conducted in coordination with the United Nations-endorsed Space Mission Planning Advisory Group (SMPAG), enabling an exercise of SMPAG’s process for producing technical recommendations for space mission options using inputs received from space agencies in participating nations. In this paper, we describe the work performed for this exercise by the NASA-led team.
We will discuss our methodology for assessing space mission options to respond to the hypothetical asteroid threat scenario, including reconnaissance missions and Earth impact prevention missions. For reconnaissance, we assessed flyby and rendezvous options and we included both re-tasked extant spacecraft and purpose-built spacecraft. Detailed results for analysis of re-tasking extant spacecraft for reconnaissance will be presented in a related paper. Fig. 1 shows some exemplar reconnaissance mission options. For Earth impact prevention missions, both asteroid deflection and robust disruption of the asteroid are considered, and the following mission types are assessed: ion beam deflection, kinetic impactor deflection and disruption, and nuclear explosive device deflection and disruption. Fig. 2 shows some example trade space evaluations for several deflection mission types.
We will also summarize simulation studies performed to 1) ascertain how much change-in-velocity ($\Delta v$) an asteroid can tolerate before fragmentation onset, and 2) establish requirements for robustly disrupting an asteroid, i.e., breaking it into small and widely scattered fragments posing little to no residual Earth impact risk. Detailed results of these simulation studies will be presented in a related paper and some example simulation outputs are shown in Fig. 3. The $\Delta v$ required for asteroid deflection as a function of time is shown in Fig. 4. Heuristics informed by the simulation results are incorporated into optimization of multi-action deflection mission campaign options that spread the total deflection impulse across multiple smaller impulses as a strategy for avoiding asteroid fragmentation during deflection. Studies were also performed assessing the minimum amount of time required between deflection impulses to measure the effects on the asteroid’s orbit before the next impulse. Details of that study are presented in a related paper.
We assessed mission options at two epochs in the scenario timeline: Epoch 1, about two months post-discovery when Earth impact probability climbs above the 1% threshold for SMPAG activation and large uncertainties in asteroid physical properties and Earth impact location drive large uncertainties mission requirements; and Epoch 2, just after a flyby reconnaissance mission has reconnoitered the asteroid, significantly reducing uncertainties in asteroid physical properties and Earth impact location and thus enabling more precise assessments of mission options.
Finally, we will summarize the results we provided as inputs from NASA to SMPAG for integration with all such results from other space agencies participating in this exercise. We also make some observations about useful generalizations from these results with potential applicability to any planetary defense scenario.