Active observation trajectory planning for non-cooperative spacecraft

Non-cooperative spacecraft operating in high-value orbits pose significant threats to space security, as ground-based navigation and orbit determination systems cannot effectively acquire key information such as payloads and attitudes, making it difficult to assess their functionality and threat level. Traditional passive observation methods suffer from security concerns and long observation cycles. To address these limitations, this paper proposes an active observation trajectory planning method that integrates a state-gain reachable set-based collision avoidance strategy with Fast Model Predictive Control (FMPC). To tackle the issue of rapidly declining safety in traditional navigation error ellipsoids over time, the proposed method utilizes an analytical approximation of the geometric bounds of the spacecraft's size-expanded state-gain reachable. This enables the development of a collision avoidance strategy that balances high computational efficiency with enhanced safety. Additionally, to overcome the challenges of prolonged observation cycles and insufficient mission concealment in traditional free-flight approaches, a reference trajectory is designed to ensure the sensor's field of view fully covers the target body and its critical payload. FMPC is then employed to calculate trajectory tracking control laws in real time, satisfying the constraints of mission cycles and forming a trajectory planning strategy that combines short cycles with comprehensive information acquisition. Compared to traditional methods, this approach achieves significant improvements in safety, concealment, and observation efficiency, providing an effective solution for the identification of non-cooperative on-orbit targets.