Lessons Learned from Near-Earth Asteroid 2024 YR4 and the International Coordination that Retired the 2032 Earth Impact Risk

2024 YR4 provided the most apparent near-term risk of any asteroid the planetary defense community has discovered since the 2004 discovery of 99942 Apophis. The international effort related to the asteroid demonstrated decades of growth in technologies useful for Near-Earth Object (NEO) observation and a strategic maturation of the institutions and coordination mechanisms designed to defend the planet from potential impactors. Career-spanning efforts by individuals and organizations inside and outside of government brought about success in the 2024 YR4 event. These included NASA’s Planetary Defense Coordination Office (PDCO), international partners at the European Space Agency (ESA), UN Office of Outer Space Affairs (UNOOSA), International Asteroid Warning Network (IAWN), Space Mission Planning Advisory Group (SMPAG), interagency partners, universities, private institutions, orbital calculation groups, key individuals, and observatories across the globe and in space. In decades past, an object such as 2024 YR4 would have been missed altogether or lost prior to having the orbit defined. However, the growth of sophisticated redundant technologies and advances in how to employ them enabled the modern planetary defense community to detect and confirm 2024 YR4, carry out extensive follow-on observations to refine its impact probabilities and physical characteristics, and coordinate and communicate sufficiently to resolve its risk level within the first apparition. Such growth has been the outcome of strategic decisions by leadership of the planetary defense community.