What are key considerations for spacecraft onboard computer architecture?

Onboard computers manage all spacecraft functions. Architecture considerations: Processing - Radiation-tolerant processors (RAD750, LEON, etc.) or COTS with mitigation, Processing margin for nominal and contingency operations; Memory - EDAC for error detection/correction, Radiation-resistant technologies (MRAM, flash qualification); Software - RTOS for deterministic timing, Fault-tolerant design, Autonomous operations capability; Redundancy - Cold/warm/hot spares, Voting architectures for critical functions, and Cross-strapping for flexibility; Interfaces - Standardized buses (SpaceWire, 1553, CAN), Sensor and actuator interfaces. Design drivers: Mission criticality level, Autonomy requirements (ground contact frequency), Heritage and development risk, and Power and mass constraints. Validation includes extensive testing, fault injection, and hardware-in-the-loop simulation.