基于样条模型的高精度星间相对定位与定姿

针对分布式小卫星编队的星间相对定位与定姿的高精度要求，提出了基于样条模型的星间相对定位与定姿的新方法。新方法将一段连续时间内的卫星状态参数用样条参数模型表示，将直接估计状态参数转化为样条参数，减少了待估参数的个数，实现了多时刻状态联解，提高了姿态参数对距离变化的敏感性，结构更加稳定。仿真结果表明，相对定位精度由5mm提高到2mm，相对定姿精度由0．0004弧度提高到0．00003弧度，并解决了估计不稳定现象。

High Precision Determination of Intersatellite Relative Position and Attitude Based on Spline Model

Small-satellite distributed SAR is a new proposed conception of space-based radar system.It carries SAR interferometry antennas on formation flying satellites,and completes the tasks of SAR,GMTI and InSAR by the cooperation of satellites and SAR antennas.It develops the SAR satellite system's properties and enlarges its application fields as much as possible.Small-satellite distributed SAR has broad prospect,however,it also faces many problems,one of which is the high precision determination of distributed SAR formation states.At present,the main measurements of relative states of satellites formation conclude intersatellite radio measurement,laser measurement,optical imaging measurement,GPS measurement and so on.Most of these measurements determine the relative position and attitude indirectly.They make use of various equipments of relative measurement to gain observations such as relative distance,relative speed,angle of sight and so on.Then they set up the relationship between observations and parameters to be estimated,and design parameters estimator to estimate the relative position and attitude.Whether the estimator can make the best of measure information and whether the estimator's structure is stable becomes the key to improve the precision of the relative position and attitude determination.In order to meet the high precision requirement for intersatellite relative position and attitude determination in distributed small satellites formation.We proposed a new estimation algorithm based on spline model for determination intersatellite relative position and attitude.New algorithm represents continuous intersatellite state parameters with spline model,translates directly estimating Intersatellite state parameters into estimating spline parameters.New algorithm has such merits as reducing parameters,improving the attitude sensitivity to intersatellite distance changing,and making the estimator's structure more stable.The simulated results show that the relative position estimation accuracy is developed from 5mm to 2mm,the relative attitude estimation accuracy is developed from 0.0004rad to 0.00003rad,and new algorithm solves the estimation instable problem.