A geostationary(GEO) satellite may serve as a navigation satellite,but there is a problem that maneuvers frequently occur and the forces are difficult to model.Based on the technique of determining satellite orbits by transfer,a predicted orbit with high accuracy may be achieved by the method of statis-tical orbit determination in case of no maneuver force.The predicted orbit will soon be invalid after the maneuver starts,and it takes a long time to get a valid orbit after the maneuver ends.In order to improve ephemeris usability,the method of rapid orbit forecasting after maneuvers is studied.First,GEO satellite movement is analyzed in case of maneuvers based on the observation from the orbit meas-urement system by transfer.Then when a GEO satellite is in the free status just after maneuvers,the short arc observation is used to forecast the orbit.It is assumed that the common system bias and biases of each station are constant,which can be obtained from orbit determination with long arc observations.In this way,only 6 orbit elements would be solved by the method of statistical orbit determination,and the ephemeris with high accuracy may be soon obtained.Actual orbit forecasting with short arc observation for SINOSAT-1 satellite shows that,with the tracking network available,the precision of the predicted orbit(RMS of O-C) can reach about 5 m with 15 min arc observation,and about 3 m with 30 min arc observation.
YANG XuHaiLI ZhiGangFENG ChuGangGUO JiSHI HuLiAI GuoXiangWU FengLeiQIAO RongChuan
以IGS(international GPS service)发布的电离层TEC(total electron content)资料为样本,用时间序列模型对全球的电离层总电子含量进行了预报。在时间序列预报模型中,不同的定阶方法导致不同的预报结果;实践证明本文使用的BIC定阶准则较好地实现了电离层总电子含量的预报。结果表明:对10d左右的预报时间段,时间序列模型的TEC计算结果相对精度高,预报相对精度优于60%的网格点数在总网格点数中所占百分比可达90%以上。
