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Improving dUT1 from VLBI intensive sessions with GRAD gradients and ray-traced delays

机译：从VLBI强化会议改善DUT1，渐变和雷追踪延迟

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摘要

Exact knowledge of the angle of Earth rotation UT1 with respect to coordinated time UTC, dUT1, is essential for all space geodetic techniques. The only technique which is capable of determining dUTI is Very Long Baseline Interferometry (VLBI). So-called Intensive VLBI sessions are performed on a daily basis in order to provide dUTI. Due to the reduced geometry of Intensive sessions, there is however no possibility to estimate tropospheric gradients from the observations, which limits the accuracy of the resulting dUT1 significantly. This paper deals with introducing the information on azimuthal asymmetry from external sources, thus attempting to improve the dUTI estimates. We use the discrete horizontal gradients GRAD and the empirical horizontal gradients GPT3 as well as ray-traced delays from the VieVS ray-tracer for this purpose, which can all be downloaded from the VMF server of TU Wien (http://vmf. geo.tuwien.ac.at). The results show that this strategy indeed improves the dUT1 estimates when compared to reference values from multi-station VLBI stations, namely by up to 15%. When converted to length-of-day (LOD), the estimates can be compared to LODs from global analyses of Global Navigation Satellite Systems (GNSS). Here, the improvement amounts to up to 7% compared to neglecting a priori information on azimuthal asymmetry. (C) 2019 COSPAR, Published by Elsevier Ltd.
机译：关于地球旋转UT1的精确知识对于协调时间UTC，DUT1，对于所有空间大地电解技术都是必不可少的。能够确定DUTI的唯一技术是非常长的基线干涉测量（VLBI）。所谓的密集VLBI会话是每天进行的，以便提供DUTI。然而，由于密集型会话的几何形状，无可能估计从观察结果的对流层梯度，这会显着限制所得DUT1的准确性。本文涉及从外部来源引入关于方位角不对称的信息，从而试图改善DUTI估计。我们使用离散水平梯度毕业和经验水平梯度GPT3以及来自Vievs Ray-Tracer的光线跟踪延迟，可以从Tu Wien的VMF服务器下载（http：// vmf。地理.tuwien.ac.at）。结果表明，与多站VLBI站的参考值相比，该策略确实改善了DUT1估计，即高达15％。当转换为日期（LOD）时，可以将估计与全局导航卫星系统（GNSS）的全局分析进行比较。这里，与忽略关于方位角不对称的先验信息相比，改善量高达7％。 （c）2019年Cospar，由elestvier有限公司出版

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