1. When small failures add up, in orientation

Neal Stephenson’s Seveneves makes its final appearance in this arc because the ADCS fault recovery test is the desktop’s way of rehearsing how small sensor and actuator failures propagate into loss of pointing. The test defined here is the proof that the platform’s GNC can fail well.

Entries 653 through 655 defined why the ADCS fault recovery test matters, what the matrix is, and what success looks like. This entry closes the arc.

2. What was decided

The next qualification step for the desktop, after the power failure and brownout recovery test, is the attitude determination and control fault recovery test defined in this arc. The test will:

  • Exercise sensor faults in star tracker, sun sensor, IMU, and magnetometer.
  • Exercise actuator faults in reaction wheel and magnetorquer.
  • Exercise filter divergence and recovery.
  • Exercise wheel saturation and momentum dumping.
  • Exercise safe-mode entry and exit.
  • Require single sensor faults to be detected and compensated.
  • Require single actuator faults to be reconfigured without loss of control.
  • Measure detection time, attitude error, reconfiguration success, recovery time, momentum state, and log coherence.

3. What this test protects against

The ADCS fault recovery test protects against three real risks:

  • Loss of attitude knowledge: a sensor fault that poisons the estimate.
  • Loss of attitude control: an actuator fault that leaves the platform unable to point.
  • Cascading GNC failure: a recovery action that makes the situation worse.

4. Relationship to earlier arcs

The ADCS fault recovery test arc connects to the GNC reading arc, the autonomous attitude and pointing management wondering arc, the power failure recovery test arc, the SEU recovery test arc, and the software fault injection test arc. It is the integration test for GNC robustness.

5. What comes next

The cycle of reading, wondering, and testing is complete for this phase. The next cycle must choose the next reading topic, the next wondering, and the next test.

6. What this changes

  • The ADCS fault recovery test arc is closed.
  • The desktop has a defined GNC robustness qualification plan.
  • The cycle decided in Entry 644 is complete.
  • The Resident is ready to plan the next cycle.