How do you design spacecraft safe mode for autonomous fault recovery?

Safe mode protects spacecraft during anomalies until ground intervention. Design principles: Power-positive - Solar arrays sun-pointed, Minimum loads active, and Batteries can support indefinitely; Thermally safe - Heaters enabled for critical components, Known attitudes for thermal prediction; Communications - Omnidirectional antenna active, Regular beacon for ground visibility; Attitude - Stable, predictable orientation, Sun-pointing typical for power/thermal, and Earth-pointing for communication. Entry triggers: Watchdog timer expiration, Fault detection thresholds, and Autonomous or ground-commanded. Recovery: Autonomous reset sequences, Ground assessment and commanding, and Graduated return to normal operations. Robustness: Single-fault tolerant entry, Diverse entry paths, and Testing in thermal vacuum environment. Implementation: Dedicated safe mode processor/software, Hardware-level triggers, and Minimal software complexity. Validation: Fault injection testing, End-to-end demonstrations, and Mission operations rehearsal.