SGP4模型用于空间目标碰撞预警的准确性与有效性分析

针对SGP4模型用于空间目标碰撞预警中的轨道推演阶段问题，编制了空间目标碰撞预警分析程序，并对其准确性与有效性进行分析. 对目前已确切掌握的3次空间目标碰撞事件进行分析，取碰撞历元时刻前10、7、5、3和1 d的两行根数，采用SGP4模型计算目标的位置和速度矢量，运用碰撞理论计算两目标的碰撞概率，按照通行的碰撞概率判别标准，分析SGP4模型用于碰撞预警的准确性与有效性. 结果表明，利用SGP4模型进行筛选计算得到的碰撞时间与实际碰撞时间相符，且碰撞概率达到预警门限，证明了空间目标碰撞预警分析软件的正确性，但其准确性与有效性随着预警时间的增加而下降，在预警天数小于5 d时效果最好. 

Accuracy and Effectiveness Analysis of SGP4 Implemented in Space Debris Collision Alert

To analyze the accuracy and effectiveness of using SGP4 model for orbit prediction and collision alert, the space object collision alert software was made to realize it. For the three space collisions that ever happened, the space objects' position and speed were calculated to get the collision probability, using the TLEs which NORAD announced 1, 3, 5, 7 and 10 days before the collision, and then analyzed the accuracy and effectiveness of SGP4 model. The results show that, the alert collision time calculated using SGP4 model for orbit prediction and collision alert is consistent with the actual collision time, and the collision probability gets the alert warning. However, the accuracy and effectiveness of SGP4 model decrease with the increase of the alert days, and SGP4 model works best when the alert day is less than 5.