Trajectory Determination For Lunar Probe Soft Landing And Earth-moon Libration Orbit

In the past two decades,with the opening of China's deep space exploration,China has successfully implemented a series of important lunar exploration missions.An important subsystem of the measurement and control system in deep space exploration,in which the calculation requirements for orbit determination and positioning are one of the core tasks in the measurement and control system,which is related to the success or failure of the engineering task,and is also the guarantee for the scientific results of deep space exploration.China's orbital missions have expanded from early Earth satellites to more distant solar systems.The types and requirements of orbital calculations also vary,including traditional orbiting satellite orbit determination,as well as a series of orbital positioning scenarios such as planetary or lunar surface soft landing trajectory determination,planetary or lunar surface walking positioning.In this context,the main direction of the thesis research is to study several types of external data processing methods and their applications in lunar exploration.The main research results and innovations of this paper mainly include the following aspects:(1)The commonality of orbit dynamics orbit determination,kinematics statistical orbit determination and planetary(moon)surface statistical positioning method in deep space exploration is analyzed,and the unified processing equation is given.The use of unified equations to describe the orbital positioning problem in deep space exploration is conducive to the engineering of multi-functional software development.The track calculation problem of different application requirements can be developed into corresponding software modules to facilitate software implementation.(2)The mathematical approximation method of complex trajectory during the soft landing of the planet(the moon)is studied,and the optimal solution to the trajectory is given under the condition of the standard B-spline approximation method.This method is general and can be extended to other forms of numerical approximation methods.Since the measurement equation is nonlinear,even if the linear system is approximated,it is still nonlinear in terms of estimation.The paper analyzes the initial value problem and gives a regularization strategy in the case of overfitting.For the problem of flight orbit calculation with dynamic constraints,the method of ballistic determination for joint solving differential equations and algebraic equations is studied.(3)For the GNC trajectory of the CE-3 simulation,the simulation calculation was carried out by the standard B-spline approximation method.The data analysis shows that the B-spline achieves the solution to the simulated trajectory with very high precision and strong stability.In the implementation of the No.3 mission,the software used the real-time processing of the precision ballistics determination of the lunar segment,and reported the solution results to the decision of the Beijing Aerospace Control Center.The use of this method is the first time that China has used external testing to estimate the lunar soft landing trajectory.(4)The orbit determination data processing of the detector during the Halo orbital flight at the L2 point of the Earth-moon is studied.The measurement data of the “The Magpie-Bridge” of the CE-4 relay satellite is analyzed,and the orbit determination accuracy is up to 100 meters.The influence of VLBI on the accuracy of the orbit during this period is analyzed.The Halo orbit is an important flight orbit in deep space exploration missions.It has its special engineering and theoretical value.This paper studies the accuracy of its orbit determination by ground control and control with specific engineering background,and discusses the corresponding Track characteristics.It has certain reference value for subsequent similar missions.(5)The 1-way Doppler positioning technique for the lunar back detector is studied by using the lunar satellite L2 point relay satellite.Using the ground system crystal data as the system measurement noise,the statistical positioning analysis of the lunar back detector is carried out.The results show that the positioning performance is poor in the case of single-star measurement and unstable crystal oscillator.In the case of measuring geometry and crystal instability,one of the effective measures to improve the positioning accuracy is to constrain the lunar elevation.Since the rear target of the moon cannot be directly measured by the ground-based measurement and control network,the position measurement using the L2 translation point Halo orbit relay star provides a possibility for the implementation of the project,but it must be demonstrated that the accuracy under certain conditions is The determination of the project plan provides decision support.The development of deep space exploration precision orbit calculation software requires a long time of accumulation.Through the research on the requirements of different orbits and positioning tasks in the lunar exploration,the orbital software function of the research group has been enriched,which lays a good foundation for the subsequent more complex measurement and control data processing requirements.