The ground segment is the terrestrial side of a satellite system: antennas, mission control centers, tracking stations, networking gear, software, and operators that communicate with satellites, monitor their health, and send commands. It is the control layer that keeps a space asset useful after launch.
In cyber security, the ground segment matters because compromising it can let an attacker disrupt services, steal telemetry, alter commands, or hijack the mission picture. It is often a richer target than the satellite itself, since it uses standard IT and operational technology components, remote access tools, and supplier connections. Defenders protect it with strong authentication, network segmentation, key management, logging, tamper-resistant command paths, and strict separation between engineering, operations, and vendor access. In attacks, weaknesses such as exposed remote services, stolen credentials, or supply-chain compromise can provide a path into mission control.