Consistent dynamic satellite reference frames and terres-trial geodetic datum parameters

该项目的目的是利用现有全球导航卫星系统、SLR和DORIS对具有不同轨道高度、倾角和跟踪技术特点的个别和普遍观测卫星的观测优势，实现高精度动态参照系。这项工作的重点是改进对全球大地基准的认识，以及为定义地球参考框架的基准制定新的概念。与前一个项目相比，特别是通过至少两种技术观测到的低地球轨道卫星将被包括在内。这些类型的卫星充当移动的联合定位站点，以非常不同的和不断变化的观测几何来提供观测。因此，联合轨道确定将大大加强参考框架解，预计该解对大地基准参数的敏感性将大大增加。为了了解和评估对基准参数非常敏感的卫星和空间站的配置，进行了补充的模拟研究。模拟使它能够调查新的轨道和观测类型。将通过更广泛的模拟研究地球同步导航卫星以及导航卫星之间的Doris相位观测和卫星间精确测距链路对参照系稳定性的贡献。该项目的成果是具有今天所能达到的最高精度的基准实现的划时代和长期参照系。此外，还将提出建议，说明今后如何通过新的卫星飞行任务和优化的观测站网络以及通过使用新的观测类型来改进地面参照系的基准实现。

The aim of the project is the realization of high-precision dynamic reference frames by exploiting the strengths of the available GNSS, SLR and DORIS observations to individual and commonly observed satellites that are characterized by different orbit heights, inclinations and tracking techniques. The focus of the work is the improved realisation of the global geodetic datum as well as on the development of novel concepts for the datum definition of the terrestrial reference frames. Compared to the previous project, in particular low Earth orbiting satellites observed by at least two techniques will be included. These type of satellites act as moving co-location sites and provide observations with very different and changing observation geometries. Thus, combined orbit determination will strengthen the reference frame solution significantly and it is expected that the sensitivity of the solution with respect to the geodetic datum parameters will increase strongly. Complementary simulation studies are performed in order to realize and assess satellite and station configurations which are very sensitive to the datum parameters. Simulations allow it in addition to investigate new orbit and observation types. The contribution of geosynchronous navigation satellites as well as DORIS phase observations and precise inter-satellite ranging links between navigation satellites to the stability of the reference frame will be investigated with extended simulations. The outcomes of the project are epoch and long-term reference frames with a datum realization of the highest accuracy which can be reached today. Furthermore, recommendations will be made, how the datum realization of the terrestrial reference frames can be improved in future by new satellite missions and optimised observing station networks but also by using new observation types.