Consistent celestial and terrestrial reference frames by improved modelling and combination

该项目的目标是在改进空间大地测量观测模型和发展和应用先进组合方法的基础上，提供具有最高一致性的天体参考框架（CRF）、地面参考框架（TRF）和相应的地球定向参数（EOPs）。将均匀处理的VLBI、SLR和GNSS观测时间序列结合起来，通过应用两种不同的方法来推导这些参考框架：a)在观测方程水平上（在BKG）， b)在无约束正常方程水平上（在DGFI）。这两个机构除了计算长期的多年参考系外，还将每周结合不同的空间大地测量技术来计算历元参考系。因此，BKG生成具有一致应用的合适地球物理流体模型的解，并将研究后者对参考框架结果的影响。BKG还将开发改进的组合方法，通过包括卫星共定位，即通过额外使用单反观测到GNSS卫星，来实现一致的TRF和EOP估计。DGFI将应用非线性台站运动的扩展参数化进行长期参考框架计算，并将为CRF、TRF和EOPs生成一致的结果。不同的策略和参考框架结果将相互比较，并与IERS提供的外部解决方案进行比较。最后，本项目的结果将允许评估改进的TRF、CRF和EOP组合方法与标准IERS方法相比的增益。

The goal of this project is to deliver a celestial reference frame (CRF), a terrestrial reference frame (TRF), and the corresponding Earth orientation parameters (EOPs) with highest possible consistency based on improved modelling of the space geodetic observations and on the development and application of advanced combination methods. The combination of the homogeneously processed VLBI, SLR and GNSS observation time series to derive those reference frames will be performed by applying two different approaches: a) on the level of observation equations (at BKG), and b) on the level of constraint-free normal equations (at DGFI). Both institutions will compute epoch reference frames by combining the different space geodetic techniques on a weekly basis, in addition to the computation of long-term multi-year reference frames. Thereby, BKG generates solutions with suitable geophysical fluid models consistently applied, and the impact of the latter on the reference frame results will be studied. BKG will also develop improved combination methods for a consistent TRF and EOP estimation by including satellite co-locations, i.e., by additionally using SLR observations to GNSS satellites. DGFI will apply the extended parameterization of non-linear station motions for long-term reference frame computations and will generate consistent results for CRF, TRF and EOPs. The different strategies and reference frame results will be compared with each other and with external solutions provided by the IERS. Finally, the results of this project shall allow to assess the gain of the improved combination methods for TRF, CRF and EOP compared to standard IERS approaches.