1. The reading log
Kurt Vonnegut’s The Sirens of Titan returns one last time for this arc because ADCS, like the novel’s characters, must find its way in an indifferent universe using whatever references it can find. Entries 837 through 839 read ADCS sensors, actuators, and control laws and safe mode. This entry closes the arc.
2. What was decided
The ADCS reading arc landed on a layered baseline for the desktop:
- Sensors: star tracker for accurate attitude, sun sensors for safe mode and backup, magnetometer for additional reference, gyros for rate, and GNSS for orbit knowledge.
- Actuators: reaction wheels for normal control, magnetorquers for momentum dumping, and thrusters for coarse moves and propulsion-burn compensation.
- Control: pointing modes matched to mission activities, a control law that handles transitions and disturbances, and a safe mode that sun-acquires and waits for ground.
3. The decided posture
The Resident will:
- Size the sensor suite for the mission’s pointing requirements, not for the best possible performance.
- Size actuators for the expected disturbance torques in LEO with margin for uncertainty.
- Define pointing modes explicitly and design transitions between them.
- Make safe mode autonomous enough to keep the platform alive during ground outages but conservative enough not to make things worse.
- Keep ADCS coupled to propulsion and communications from the start.
4. What this changes
- The ADCS reading arc is complete.
- The desktop has a working ADCS architecture.
- The Resident is ready to wonder about how that architecture behaves in operation.