空间目标碰撞预警的协方差计算与应用

碰撞概率是碰撞预警工程中空间目标危险交会的重要判据之一，其计算精度会受到预报协方差计算精度的影响. 本文统计计算了两种形式的预报协方差. 一是利用精密数值预报模型对卫星精密根数进行预报，将预报根数与精密根数的差作为样本，统计得出1～7天不同预报期的预报协方差；二是采用 SGP4/SDP4预报模型对TLE数据进行预报，将预报根数与TLE根数的差作为样本，统计得出1～7d不同预报期的预报协方差. 分别分析两种方法中包含变轨过程和无变轨情况下的轨道预报精度. 结合2012年某低轨道卫星的危险交会，分析了采用不同协方差时，协方差精度对碰撞预警精度的影响. 协方差计算可为实际碰撞预警工程提供参考. 

Study of Covariance Calculation in Space Objects Collision Warning

Collision probability is an important criterion in collision warning of space objects. The accuracy of forecast covariance calculation directly affects the accuracy of the collision probability calculation. In the paper we compute two forms of statistical forecast covariance. One is to use precision numerical forecast model and the satellite precision orbit data to forecast for a specified time period, and make statistical calculation of forecast covariance of different time period as 1～ 7 days. The other is to use SGP4/SDP4 forecasting model and TLE data to forecast, and make the statistical calculation of forecast covariance of the forecast time period as 1～ 7 days. Then the forecast accuracy through two methods with the data elements affected by orbit change and without orbit change is analyzed. Taking the 2012 risk conjunction of the satellite as example, the collision warning accuracy affected by the covariance accuracy is analyzed. This covariance calculation can provide reference for actual collision warning works.