Space systems have become key enablers for a wide variety of applications on Earth through evolving capabilities in navigation, positioning, timing, data gathering and communications. These capabilities have become, in certain instances, critical to the functioning of critical infrastructure systems. These are interconnected sociotechnical systems which provide critical goods and services and whose destruction or disruption would cause significant loss of human life, material damage and other effects. The paper argues that space systems can provide a new category of critical infrastructures and highlights the differences between terrestrial and spaceborne systems from the perspective of the critical infrastructure protection framework.