基于GNSS单站区域电离层模型的VLBI世界时测量精度分析
Accuracy Analysis of VLBI Universal Time Measurement Based on a GNSS Single-Station Regional Ionospheric Model
AI总结：
研究利用吉林 - 喀什基线VLBI站的GNSS数据构建单站区域电离层模型，用于VLBI观测的电离层延迟校正，提高UT1测量精度，其校正性能优于全球预测模型，接近全球后处理模型，对提升独立UT1产品及时性有重要价值。
AI中文摘要：
世界时（UT1）是表征地球自转的关键参数，甚长基线干涉测量（VLBI）是测量UT1的主流技术。为解决现有全球电离层模型在单频VLBI UT1测量的及时性和准确性方面的局限性，利用吉林 - 喀什基线VLBI站的GNSS数据构建单站区域电离层模型。将该模型应用于VLBI观测，并与全球预测模型和全球后处理模型的校正性能进行比较。结果表明，单站区域模型计算的视线电离层延迟和基线校正精度接近全球后处理模型，远优于全球预测模型。经单站区域模型校正后，导出的UT1值与美国海军天文台（USNO）参考值的平均偏差为 -15.6微秒，均方根偏差为82.3微秒，均优于其他两种模型类别的结果。独立于VLBI站可用GNSS数据构建的单站区域电离层模型可有效校正单频VLBI观测并支持准实时高精度UT1测量，对提高独立UT1产品的及时性具有重要价值。
英文摘要：
Universal Time (UT1) is a key parameter characterizing Earth's rotation, and very long baseline interferometry (VLBI) is the mainstream technique for measuring UT1. To address the limitations in the timeliness and accuracy of existing global ionospheric models for single-frequency VLBI UT1 measurements, we construct a single-station regional ionospheric model using GNSS data from the VLBI stations on the Jilin-Kashi baseline. We apply this model to VLBI observations and compare its correction performance with that of a global predictive model and a global post-processed model. The results show that the line-of-sight ionospheric delays and baseline corrections calculated with the single-station regional model have precision close to that of the global post-processed model and are substantially better than those of the global predictive model. After correction with the single-station regional model, the derived UT1 values differ from the US Naval Observatory (USNO) reference values by a mean bias of -15.6 us and an RMS deviation of 82.3 us, both better than the results obtained with the other two model classes. A single-station regional ionospheric model constructed independently from GNSS data available at VLBI stations can effectively correct single-frequency VLBI observations and support quasi-real-time high-precision UT1 measurements. It therefore has important value for improving the timeliness of independent UT1 products.
