For a sophisticated Rotorcraft Lander Sampling System, ALTEN Technology undertook the comprehensive development of its flight software, adhering strictly to NPR 7150.2D Class C mission standards. This involved deep collaboration with the client’s diverse engineering teams and meticulous trade studies to select the most suitable operating systems, file systems, and analysis tools. The project saw the creation of flight software featuring a custom publish/subscribe data flow architecture, modules designed with UML diagrams, and a custom interface transfer frame utilizing CCSDS packets. Furthermore, a robust DevOps system was implemented, automating builds, unit, and system-level testing, complete with code coverage and static analysis dashboards, and an automatic code generator. The results included a complete flight software framework and system architecture supporting 24 modules, alongside a sophisticated digital twin simulator replicating the lander’s electrical modules and mechanisms like the sample delivery carousel and percussive drill. ALTEN Technology also integrated a single-board computer and established a lander simulation for command and telemetry visualization. Emphasis was placed on reliability, incorporating error detection and correction, memory scrubbing, CRC on I/O, a journaled filesystem, and redundant firmware, all capped by comprehensive formal documentation for seamless client handoff.