Stochastic Dynamics of and Collision Prediction for Low Altitude Earth Satellites
Stochastic Dynamics of and Collision Prediction for Low Altitude Earth Satellites
复制标题
低空地球卫星的随机动力学和碰撞预测
DOI：
--
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
W. Wiesel
中科院分区：
文献类型：
--
作者：
Adam T. Rich;K. J. Stuart;W. Wiesel
来自地球卫星单元集的空气阻力B *因子通常表现出高斯-马尔可夫过程的近高斯分布和自相关指数衰减特征。假设“最新”的轨道元素集是正确的，那么可以使用较早的元素来构建协方差矩阵，作为预测未来时间的函数。如果在圆柱形轨道坐标系中进行解析，这些数据的结构非常明显，基本上只显示了轨道内误差的增长。通常，轨道位置协方差元素的增长遵循四次时间规则，并且肯定是由空气阻力因素的不确定性所强迫的。这一观察结果得到了扰动理论和随机状态协方差传播模型的证实。意识到SGP4模型下几乎所有的误差增长都在轨道上，宇宙2251/铱33事件被重新审视。虽然最后一个元素的碰撞预测显示最小的脱靶距离约为700米，但同样的元素显示最近的轨道距离仅为32米。考虑到较大的轨道不确定性，最小轨道间距可能是机动决策更可靠的度量。
Air drag B∗ factors from Earth satellite element sets often show the characteristic near Gaussian distribution and autocorrelation exponential decay typical of a Gauss-Markov process. Assuming the “most current” set of orbital elements are correct, earlier elements can be used to construct covariance matrices as a function of prediction time into the future. If resolved in cylindrical orbit frame coordinates, these are remarkably structured, essentially showing only in-track error growth. Often the in-track position covariance element growth follows a fourth power in time rule, and is definitely forced by the uncertainty in the air drag factor. This observation is confirmed both by perturbation theory and by modeling stochastic state covariance propagation. Realizing that almost all error growth under the SGP4 model is in track, the Cosmos 2251/Iridium 33 event is reexamined. While a collision prediction from the last elements shows a minimum miss distance of about 700 m, those same elements show a closest approach distance of the orbits of only 32 m. Given large in-track uncertainty, minimum orbit separation may be a much more reliable metric for maneuver decisions.