北斗卫星钟差异常值处理的似然比方法

北斗卫星导航系统(BDS)星载原子钟由于受到空间环境的影响和各种不确定因素的干扰,导致获取的卫星钟差数据中经常会出现异常扰动,从而降低了卫星钟性能分析的可靠性、破坏了钟差建模和预报的有效性、影响导航定位结果的精准度,需要对BDS卫星钟差数据中存在的异常值进行探测和处理。基于求和自回归移动平均模型建立BDS卫星钟差异常值探测的方差膨胀模型;运用似然比方法对BDS卫星钟差时间序列中的异常值进行探测;推导了Score检验统计量,运用最小二乘法对异常扰动的大小进行估计。试验结果表明,似然比方法能够准确探测BDS卫星钟差数据中异常值的位置,精确估计异常扰动的大小。

Likelihood Ratio Method for Outlier Detection and Estimation in BeiDou Satellite Clock Offset

Due to the interference of various uncertain factors, the abnormal disturbances often occur in the BeiDou satellite clock offset, which reduces the reliability of the performance analysis of the satellite clock, destroys the validity of the modeling and prediction of the satellite clock offset, and affects the accuracy of the navigation positioning results. So it is necessary to detect and process the outliers in the BeiDou satellite clock offset. In this regard, based on the autoregressive integrated move average(ARIMA) model, a variance expansion model for outlier detection of the BeiDou satellite clock offset is established;a likelihood ratio method for detecting outliers in the BeiDou satellite clock offset is applied;a Score test statistic is derived;the magnitudes of the abnormal disturbances are estimated by least square method. Test examples illustrate that the likelihood ratio method can detect the location of outliers and estimate the abnormal disturbances accurately in the BeiDou satellite clock offset.