doi:10.1016/j.actaastro.2026.04.026engShi, QianHuang, YinchienArnas, DavidDeLaurentis, DanielA system-of-systems approach to US space sustainability governanceART-2026-149491The rapid expansion of satellite deployments and commercial activity in low Earth orbit has outpaced existing policy frameworks, raising urgent concerns about long-term space sustainability. This work proposes and applies a system-of-systems-based framework to assess structural and operational gaps in the United States’ approach to orbital stewardship. The framework combines a knowledge graph method to map institutional relationships and oversight fragmentation, with system-of-systems design principles to characterize structural drivers of the sustainability challenge and guide policy development and prioritization. The resultant analysis covers three major governance gaps: weak enforcement, fragmented standards, and policy lag, and organizes efforts to close these gaps into the domains of space situational awareness, space traffic management, and space environment preservation. A taxonomy of sustainability metrics organized by aim, method, and scope is also provided to support future policy evaluation and capacity planning. Overall, this work serves as a foundation for systematic sustainability assessment and informed governance strategies that can support adaptive policy design, compliance planning, and long-term orbital stewardship.2026http://zaguan.unizar.es/record/17174010.1016/j.actaastro.2026.04.026http://zaguan.unizar.es/record/171740oai:zaguan.unizar.es:171740Acta Astronautica 247 (2026), 315-336All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/closedAccess