Which onboard system stores and processes data to enable autonomous spacecraft operation?

• A. Ground control server
• B. Onboard computer / flight computer
• C. Reaction wheel assembly
• D. Telemetry relay

Answer: (B)

Autonomy hinges on the onboard computer, which acts as the spacecraft’s brain. It stores data locally and runs the flight software that turns sensor inputs into actions, performing guidance, navigation, and control in real time. This processor handles sensor fusion from instruments like inertial measurements, star trackers, and cameras, executes decision-making, and commands attitude control and propulsion or reaction wheels as needed. It also runs fault-detection and recovery routines and keeps mission data and logs on board. Operating with low latency and high reliability, often with redundancy and radiation tolerance, the onboard computer enables the spacecraft to operate independently when Earth is far away or communication delays exist.

The ground control server is used for mission planning, sending commands, and receiving data from Earth, but it isn’t capable of autonomously steering the spacecraft in real time. The reaction wheel assembly provides the physical rotation control but does not process data. The telemetry relay handles data transmission to Earth, not onboard decision-making.