GNSS精密轨道产品不连续性分析及评估

按照目前的国际规范, 高精度GNSS (Global Navigation Satellite System)轨道产品一般以天为周期进行发布, 提供给用户使用. 连续使用多天的产品存在不同天间的跳变问题. 利用德国地学研究中心(GFZ)、欧洲定轨中心(COD)、欧空局(ESA)、美国喷气试验室(JPL)以及上海天文台(SHA)共5个GNSS分析中心2013---2017年的轨道产品, 分析了轨道跳变的特性. 计算结果表明: GFZ、COD、ESA、SHA和JPL的3维轨道跳变平均分别为7.79cm、1.51cm、7.77cm、11.75cm和2.51cm. 轨道跳变序列的周期特性分析表明: 序列存在90d、120d、340d左右的显著周期项, 对应于海潮对地球自转的影响, 其振幅为数毫米至1cm左右. 表明精密轨道确定需要进一步精化该项模型; GPS的跳变序列还存在与卫星星座相关的175d和352d左右的交点年显著周期项. 此外, 针对COD产品外推轨道的分析, 验证了地球反照辐射压和太阳光压模型等动力学模型对轨道的差异.

Analysis and Assessment of the Orbit Discontinuity of the GNSS Precise Products

Following the current IGS (International GNSS Service) convention, the precise satellite orbit and clock are archived with the standard ``SP3'' format, which is disseminated on daily basis. Thus, the adjacent IGS precise orbit products display discontinuity at the junction of two successive days. The orbit discontinuity reflects the orbit errors due to orbit propagation errors, owing to the orbit dynamics mis-modeling. Most researches use the Day Boundary Discontinuity (DBD) for the assessment of orbit quality. In this paper, the long period DBD time series of the precise IGS orbit products are analyzed. The precise orbit products of five GNSS (Global Navigation Satellite System) Analysis Centers (AC), including GeoForschungsZentrum (GFZ), Center for Orbit Determination in Europe (COD), European Space Agency (ESA), Shanghai Astronomical Observatory (SHA), and Jet Propulsion Laboratory (JPL), are used to derive the orbit discontinuity time series covering the period from the year 2013 to 2017. Analysis of the time series shows that the mean three-dimensional DBD of GFZ, COD, ESA, SHA, and JPL are 7.79 cm, 1.51 cm, 7.77 cm, 11.75 cm, and 2.51 cm, respectively. The periodic characteristic of DBD shows significant signals at the frequency of 90 days, 120 days, and 340 days, which correspond to the long period ocean tides. The amplitude of these periods is about millimeters to 1 centimeter, indicating the current utmost precision of GNSS orbits. The fundamental period terms of 175 days and 352 days match the GPS draconitic year, corresponding to the re-visit cycle of GPS constellation. The analysis of orbit extrapolation errors of COD products verifies the influence of dynamic models, e.g. the earth radiation pressure model and the solar radiation pressure model, on the orbit discontinuity, where the periodical and systematic effects are derived.