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Resolving VLBI correlator ambiguity in the time delay model improves precision of geodetic measurements
Publications of the Astronomical Society of Australia ( IF 6.3 ) Pub Date : 2020-12-01 , DOI: 10.1017/pasa.2020.43
O. Titov , A. Melnikov , Y. Lopez

The modern Very Long Baseline Interferometry (VLBI) relativistic delay model, as documented in the IERS Conventions, refers to the time epoch when the signal passes one of two stations of an interferometer baseline (selected arbitrarily from the pair of stations and called the ‘reference station’ or ‘station 1’). This model consists of the previous correlation procedure used before the year 2002. However, since 2002 a new correlation procedure that produces the VLBI group delays referring to the time epoch of signal passage at the geocenter has been used. A corresponding correction to the conventional VLBI model delay has to be introduced. However, this correction has not been thoroughly presented in peer reviewed journals, and different approaches are used at the correlators to calculate the final group delays officially published in the IVS database. This may cause an inconsistency up to 6 ps for ground-based VLBI experiments between the group delay obtained by the correlator and the geometrical model delay from the IERS Conventions used in data analysis software. Moreover, a miscalculation of the signal arrival moment to the ‘reference station’ could result in a larger modelling error (up to 50 ps). The paper presents the justification of the correction due to transition between two epochs elaborated from the Lorentz transformation and the approach to model the uncertainty of the calculation of the signal arrival moment. Both changes are particularly essential for upcoming broadband technology geodetic VLBI observations.

中文翻译:

解决时延模型中的 VLBI 相关器模糊性提高了大地测量的精度

现代超长基线干涉测量 (VLBI) 相对论延迟模型,如 IERS 公约中所述,是指信号通过干涉仪基线的两个站点之一时的时间纪元(从这对站点中任意选择并称为“参考”)站”或“站 1”)。该模型由 2002 年之前使用的先前相关程序组成。然而,自 2002 年以来,已经使用了一种新的相关程序,该程序产生 VLBI 群延迟,指的是地心处信号通过的时间纪元。必须引入对传统 VLBI 模型延迟的相应修正。然而,这种更正并没有在同行评审的期刊中彻底呈现,并且在相关器中使用不同的方法来计算在 IVS 数据库中正式发布的最终群延迟。对于基于地面的 VLBI 实验,这可能会导致相关器获得的群延迟与数据分析软件中使用的 IERS 约定的几何模型延迟之间的不一致高达 6 ps。此外,对“参考站”的信号到达时刻的错误计算可能会导致更大的建模误差(高达 50 ps)。本文介绍了由于洛伦兹变换阐述的两个时期之间的过渡而进行校正的理由,以及对信号到达时刻计算的不确定性进行建模的方法。这两项变化对于即将到来的宽带技术大地 VLBI 观测尤为重要。对于基于地面的 VLBI 实验,这可能会导致相关器获得的群延迟与数据分析软件中使用的 IERS 约定的几何模型延迟之间的不一致高达 6 ps。此外,对“参考站”的信号到达时刻的错误计算可能会导致更大的建模误差(高达 50 ps)。本文介绍了由于洛伦兹变换阐述的两个时期之间的过渡而进行校正的理由,以及对信号到达时刻计算的不确定性进行建模的方法。这两项变化对于即将到来的宽带技术大地 VLBI 观测尤为重要。对于基于地面的 VLBI 实验,这可能会导致相关器获得的群延迟与数据分析软件中使用的 IERS 约定的几何模型延迟之间的不一致高达 6 ps。此外,对“参考站”的信号到达时刻的错误计算可能会导致更大的建模误差(高达 50 ps)。本文介绍了由于洛伦兹变换阐述的两个时期之间的过渡而进行校正的理由,以及对信号到达时刻计算的不确定性进行建模的方法。这两项变化对于即将到来的宽带技术大地 VLBI 观测尤为重要。
更新日期:2020-12-01
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