Real-Time Responsiveness and Communication Validation Platform for CubeSats

This paper presents a real-time testing platform designed to evaluate the timing behavior and communication reliability of CubeSat subsystems. At its core, the platform integrates a custom logger, along with mock software modules that simulate key CubeSat subsystems. These modules are implemented using the Zephyr Real-Time Operating System and communicate using the CubeSat Space Protocol over a Controller Area Network bus. The system supports controlled and repeatable experimentation, enabling precise assessment of message latency, deadline adherence, and inter-task communication dynamics. In addition, the platform offers extensible interfaces to support the integration and testing of flight software components under realistic operational constraints. The proposed platform facilitates early-stage design validation and performance characterization within the CubeSat development lifecycle, offering deeper insights into inter-subsystem communication behavior. This enables development teams to deliver more reliable software and produce more accurate data link budgets, with particular emphasis on timing determinism and subsystem interaction fidelity.