A system-of-systems is a mission architecture made up of multiple independent parts that only work as intended when linked together. In space operations, that can include spacecraft, ground stations, command links, timing services, navigation inputs, and support software. Each component may be built and managed separately, but the mission depends on all of them acting as one.
In cyber security, this matters because the attack surface is distributed. A spacecraft may be hardened in orbit, yet still inherit risk from a compromised ground network, a weak third-party service, or a spoofed navigation signal. Defenders use this concept to map trust boundaries, apply the right controls to each segment, and monitor the whole chain continuously. Common threats include command-path abuse, jamming, spoofing, and configuration drift; common defenses include segmentation, resilient communications, and lifecycle risk management.