What is the difference between a soft fault and a hard fault in spacecraft avionics?

• A. A soft fault is transient and recoverable; a hard fault is persistent and typically requires remediation.
• B. A soft fault causes permanent damage; a hard fault is temporary.
• C. Soft fault affects only sensors; hard fault affects actuators.
• D. Soft fault occurs during launch; hard fault occurs in orbit.

Answer: (A)

Fault classification in spacecraft avionics hinges on whether a detected problem is transient and recoverable or persistent and in need of remediation. A soft fault is a temporary anomaly that tends to disappear on its own or after a simple reset. It might arise from a brief radiation-induced bit flip, momentary electrical noise, or a sensor glitch. Because it doesn’t leave lasting damage and can be resolved quickly, the system can typically mask the fault, perform a recheck, or reboot to resume normal operation.

A hard fault, on the other hand, is persistent even after power cycles and reinitialization. It points to a real hardware or persistent software failure, such as a stuck memory bit, a degraded channel, or a failed actuator sensor. To preserve safety and mission capability, fault management must isolate or bypass the faulty element, switch to redundancy, reconfigure the system, or move to safe-mode procedures with planned remediation.

So the best way to think about it is: soft faults are transient and recoverable, while hard faults are ongoing and require a remediation or fallback strategy.