Why is Space Cybersecurity Unique?

As space systems become critical infrastructure, they have attracted increasing attention from the cybersecurity community. This paper argues that securing spacecraft requires a mission-centric cybersecurity paradigm that treats mission con- tinuity and availability as first-order design and security primi- tives, rather than adapting practices from terrestrial systems. We identify seven constraints that shape the space security problem: mission-specific designs that prevent standardization, physics that couples software to irreversible orbital dynamics, permanent loss of hardware access after launch, communication gaps that mandate autonomous decisions, environmental degradation of electronics, tight subsystem dependencies that enable cascading failures, and governance pressures that constrain feasible security architectures. None of these dimensions is unique in isolation, but their simultaneous presence and coupling produces a distinct security problem and design space.