Varenius Eskil, Haas Rüdiger, Nilsson Tobias
Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology, 439 92 Onsala, Sweden.
Lantmäteriet - The Swedish Mapping, Cadastral, and Land Registration Authority, Lantmäterigatan 2C, 801 82 Gävle, Sweden.
J Geod. 2021;95(5):54. doi: 10.1007/s00190-021-01509-5. Epub 2021 Apr 22.
We present results from observation, correlation and analysis of interferometric measurements between the three geodetic very long baseline interferometry (VLBI) stations at the Onsala Space Observatory. In total, 25 sessions were observed in 2019 and 2020, most of them 24 h long, all using X band only. These involved the legacy VLBI station ONSALA60 and the Onsala twin telescopes, ONSA13NE and ONSA13SW, two broadband stations for the next-generation geodetic VLBI global observing system (VGOS). We used two analysis packages: to pre-process the data and solve ambiguities, and to solve for station positions, including modelling gravitational deformation of the radio telescopes and other significant effects. We obtained weighted root mean square post-fit residuals for each session on the order of 10-15 ps using group-delays and 2-5 ps using phase-delays. The best performance was achieved on the (rather short) baseline between the VGOS stations. As the main result of this work, we determined the coordinates of the Onsala twin telescopes in VTRF2020b with sub-millimetre precision. This new set of coordinates should be used from now on for scheduling, correlation, as a priori for data analyses, and for comparison with classical local-tie techniques. Finally, we find that positions estimated from phase-delays are offset mm in the up-component with respect to group-delays. Additional modelling of (elevation dependent) effects may contribute to the future understanding of this offset.
我们展示了对昂萨拉空间观测站三个大地测量甚长基线干涉测量（VLBI）站之间干涉测量进行观测、相关性分析的结果。2019年和2020年共进行了25次观测，其中大部分观测时长为24小时，均仅使用X波段。观测涉及传统VLBI站昂萨拉60以及昂萨拉双望远镜，即ONSA13NE和ONSA13SW，这是下一代大地测量VLBI全球观测系统（VGOS）的两个宽带站。我们使用了两个分析软件包：一个用于对数据进行预处理并解算模糊度，另一个用于解算测站位置，包括对射电望远镜的重力变形及其他显著效应进行建模。利用群时延，我们获得了每个观测时段加权均方根拟合后残差约为10 - 15皮秒，利用相位时延则为2 - 5皮秒。在VGOS站之间（相对较短）的基线上取得了最佳性能。作为这项工作的主要成果，我们以亚毫米精度确定了昂萨拉双望远镜在VTRF2020b中的坐标。从今往后，这组新坐标应被用于观测调度、相关性分析、作为数据分析的先验信息以及与经典的本地连接技术进行比较。最后，我们发现从相位时延估计的位置在垂直分量上相对于群时延偏移了 毫米。对（与仰角相关的）效应进行额外建模可能有助于未来对这种偏移的理解。
