Relative State Estimate of Non-cooperative Target by Multiple Spacecraft Collaborative Observation

For solving the weak observability problem of angle-only relative state estimate, a multi-spacecraft collaborative observation method is proposed. The multi-spacecraft collaboration angle-only relative state estimate model is developed, including state equation and measurement equation. Firstly, based on the second-order relative motion equation, the system state equation is established; secondly, considering the line-of-sight angle measured by different spacecrafts, the system measurement equation is established; then the unscented Kalman filter algorithm is used to estimate the target’s relative state. Finally, the numerical simulation validates that the aforementioned method can effectively improve the weak observability of angle-only relative state estimate, and with the increasing of the number of spacecrafts, the convergence speed and accuracy of the relative position, velocity are also higher. In addition, the performance of the aforementioned method under uncertainty is also validated by two scenarios where the measurement data is sometimes lost and the target is maneuvered.