41. Orbit Determination of Lunar Probe Brake Course Based on Compensation to Dynamic Parameters

During orbital maneuver process, the probe relays on propulsion system to generate thrust acceleration, which tunes attitude and orbit. The complicated course of propulsion makes thrust hard to be modeled. The difficulty of precisely modeling thrust acceleration mainly includes two aspects: firstly, the begin-and-final epochs of attitude control and orbital control are not easy to determine; secondly, the acceleration of attitude control and orbital control are not easy to model accurately. It focuses on modeling and building nearly real-time filter to estimate dynamic parameters to compensate the uncertainty of the force model during the maneuver process. In the first section, the background of modeling thrust acceleration was introduced. In Sect. 41.2, the linear attitude control acceleration and the average orbital control acceleration model were used to describe the accelerating motion. In Sect. 41.3, an Extended Kalman Filter (EKF) was developed for the orbit determination with thrust involved, also the variation equation about state vector with dynamic parameters were put forward for the linearization of the non-linear dynamic system. In Sect. 41.4, the third lunar orbital brake of Chang’E-1 was processed to ascertain that the algorithm developed here can estimate the acceleration precisely during the continuous thrust maneuver process. EKF Results show that compared with the precise post-results, the error is 216 m in semi-major axis and 0.001 in eccentricity.