Time as observable in integrated ground and space-based GNSS analysis

未来，地面和太空都将有超稳定的时钟，以及高精度的时间和频率传输系统。该项目的目标是将来自这些新工具的数据纳入全球导航卫星系统大地测量数据分析，并分析其计算全球导航卫星系统全球大地测量精度产品的潜力。该项目是FOR5456研究小组的一部分，其总体目标是充分利用超稳定时钟以及大地测量中的高精度频率和时间传输。在该研究小组内，将开发时钟与全球导航卫星系统信号之间的无损链接技术，将在Wettzell（GOW）和波茨坦大地测量观测台之间提供高精度激光空间链接，将在GOW安装和运行超稳定光学时钟，并通过补偿光纤或替代光纤在波茨坦观测台和布伦瑞克的PTB光学时钟之间建立链接，计划在波茨坦操作的光学时钟。本项目将详细研究由此产生的机会，重点是全球导航卫星系统。将利用闭合实验评价全球导航卫星系统接收器与GOW场地短基线和GOW与波茨坦之间长基线上的共同时钟无损连接的好处。与此同时，还将探索为改进卫星轨道、估计参数的去相关性和确定全球网络中的大地测量参数而建立现有地面和空间时钟模型的全部潜力。利用模拟和真实的数据，将所获得的研究结果外推到全球导航卫星系统网络，以便借助所开发的方法，评价全球网络中地面和空间链路实现时间一致性的潜力，以及为估计全球大地测量参数而建立高度稳定的地面和空间时钟模型的潜力。

In the future, ultra-stable clocks will be available on the ground and in space, as well as high-precision time and frequency transmission systems. The goal of this project is to integrate data from these new tools into GNSS geodetic data analysis and to analyse their potential for computing global geodetic precision products derived from GNSS. The project is part of the FOR5456 research group, whose overarching goal is to fully exploit ultra-stable clocks and high-precision frequency and time transmission in geodesy. Within the research group the technology for a lossless link between clocks and GNSS signals will be developed, a high-precision laser space link between the Wettzell (GOW) and Potsdam geodetic observatories will be provided, an ultra-stable optical clock at the GOW will installed and operated, and a link between the Potsdam observatory and the PTB optical clocks in Braunschweig via a compensated optical fiber or, alternatively, an optical clock operated in Potsdam is planned. The resulting opportunities will be investigated in detail in this project with a focus on GNSS. The benefits of lossless linking of GNSS receivers to a common clock on short baselines on the GOW campus and on the long baseline between GOW and Potsdam will be evaluated using closure experiments. In parallel, the full potential of modelling the available ground and space clocks for satellite orbit improvement, decorrelation of estimated parameters, and determination of geodetic parameters in a global network will be explored. The obtained findings are extrapolated to global GNSS networks using simulations and real data to evaluate, by means of the developed methods, the potential of time coherence realized by ground and space links in a global network and of modelling highly stable ground and space clocks for the estimation of global geodetic parameters.