Intelligent satellites use orbital drift to save fuel observing targets
An intelligent satellite must do nothing well
Robotics
Summary
Watching other spacecraft in space usually needs careful planning and uses a lot of fuel. The authors found that a satellite that lets itself drift naturally in orbit can observe a target using almost no extra fuel. How well this works depends on whether the satellite remembers where drifting took it and if it plans far enough ahead. They also showed that safety can be improved by adding a control filter to avoid forbidden zones automatically.
What this means in practice
- •For satellite operators: Manage satellite inspections more fuel-efficiently by allowing controlled orbital drift and long-term planning.
- •For autonomous spacecraft designers: Implement control barrier functions to ensure autonomous satellites avoid restricted space zones during inspections.
Authors
Fabrizio Pilone, Giordana Bucchioni
Abstract
Autonomous inspection of a resident space object is usually posed as a contest between classical next-best-view planning and reinforcement learning. We argue that the choice of algorithm is the least informative of the design axes. An inspector spacecraft has no rest state: when it stops thrusting, orbital dynamics carry it along a natural trajectory that can be used to observe the target at no fuel cost. On a controlled ladder in which one design axis is varied at a time, fuel efficiency turns out to be set by three things: whether the agent is allowed to drift, whether its state records where drifting has taken it, and whether its planning horizon is long enough for the benefit to appear. Removing any one of them doubles the fuel bill or more. The algorithm still matters, but through what it can represent: a model-based agent whose learned world model ignores fuel spends several times more of it. Finally, no learned policy is safe by construction, and a control barrier function filter beneath the decision layer removed every keep-out-zone violation in two thousand evaluation episodes.