1. The book that knew where it was

Neal Stephenson’s The Diamond Age returns as the recalled work because the Young Lady’s Illustrated Primer must know its position and context to respond appropriately. The desktop must similarly know its orbit, predict its decay, and decide when to act.

This entry asks what autonomous orbit maintenance needs from the desktop.

2. Sensors

The platform needs data to decide. Possible sensors and data sources include:

  • GNSS receiver: position, velocity, and timing.
  • Ground-based orbit determination: uploaded ephemeris and covariance from ground tracking.
  • Conjunction data messages: such as CDMs from space surveillance networks.
  • Propulsion telemetry: tank pressure, temperature, valve states, thrust history.
  • Atmospheric density proxies: solar activity indices and geomagnetic data.

No single sensor is enough. GNSS gives current state; ground tracking refines it; CDMs give collision risk; propulsion telemetry tells the platform what it can still do.

3. Models

Sensors need interpretation. The platform needs models that map data to decisions:

  • Orbit propagation model: predicts future state given current state and perturbations.
  • Atmospheric density model: predicts drag as a function of altitude, solar activity, and geomagnetic conditions.
  • Conjunction risk model: computes collision probability from miss distance and covariance.
  • Maneuver model: predicts delta-v and propellant cost for candidate burns.
  • Propellant budget model: tracks remaining usable propellant and reserves.

These models do not need to be perfect. They need to be conservative enough to avoid collisions and propellant exhaustion, and discriminating enough to avoid unnecessary maneuvers.

4. Actuators

The platform must be able to act on its decisions. Actuators include:

  • Electric thrusters for routine stationkeeping.
  • Chemical or cold-gas thrusters for rapid collision avoidance.
  • Valves and isolation systems for propellant management.
  • Attitude control system for pointing the thrusters correctly.
  • Communications system for reporting maneuvers to ground and receiving updates.

5. Policy

Autonomy without policy is just drifting. The desktop needs rules such as:

  • Conjunction thresholds: at what collision probability does the platform maneuver?
  • Maneuver windows: when can burns occur relative to customer operations and ground contacts?
  • Propellant reserves: how much propellant must remain after any maneuver?
  • Notification rules: how soon must ground be informed of an autonomous maneuver?
  • Override: how does ground cancel or modify an autonomous maneuver plan?
  • Disposal priority: how does the platform protect propellant for end-of-life deorbit?

6. What this changes

  • Autonomous orbit maintenance is a closed-loop system of sensors, models, actuators, and policy.
  • It draws on the same infrastructure as autonomous power budgeting, radiation mitigation, and pointing management.
  • The next entry will close the autonomous orbit maintenance wondering arc and record the decision.