VLBI台站高精度对流层延迟改正方法研究

Four Very Long Baseline Interferometry (VLBI) stations are used as the tracking stations in chinese TY-project, which are important base stations in chinese aerospace. But there are two critical problems in the use of four stations, one is that the observed data at low angles can not be applied ,which lead to deleting the observed data at low angles and shorting the Observation of arc, the other is that the tropospheric delay correction is used by symmetrical hypothesis, which seriously reduce the precision of the signal path troposheric delay correction, especially for Deep Space Exploration(DSE). These problems limit the use of four VLBI stations in TY-project and following DSE. Facing the urgent requirment of applying the observed data at low angles at four VLBI stations in TY-project, we study and model the tropospheric zenith delay(ZTD) with high precision and the asymmetrical mapping function at four VLBI stations for the application of observed data at low angles, through analysing the character of the variation for tropospheric zenith and slant path delay at different elevation and azimuth direction by applying the observed data from the water vapor radiometer (WVR) and global positioning system (GPS) co-located at four VLBI sites and the long period meterological data among the site’s area. The results will provide technological support for TY-project and following DSE application.

中国探月工程用4个甚长基线干涉测量（VLBI）站（北京、上海、昆明、乌鲁木齐）作为跟踪站进行卫星定轨，是我国航天事业的重要基站。目前这4个VLBI站的应用中，存在两个致命问题：一是低高度角观测无法应用；二是对流层延迟改正采用了方位对称的假设。这两个问题一方面减少了大量观测数据，缩短了观测弧段，另一方面方位对称的假设严重影响斜路径信号改正精度（特别对深空探测），致使这4个VLBI站在探月和今后深空探测（DSE）中的应用受到很大限制。本申请根据探月工程4个VLBI站低高度角观测应用的实际需求，利用并置在这4个站的水汽辐射计全方位高精度观测数据、多年的 GPS实测数据和邻近区域气象资料，进行对流层天顶和斜路径延迟随高度、方位等时空变化特征的精细分析，研究和构建适用于这4个站低高度角观测应用中的高精度对流层天顶延迟模型和非方位对称映射函数，为当前国家探月工程和今后的深空探测任务提供技术支持。

本课题收集了气象观测数据，水汽辐射计观测数据和全球定位系统（GPS）实测数据，对甚长基线干涉测量（VLBI）台站地区对流层天顶延迟（ZTD）和斜路径延迟特征进行精细分析，提取了特征参数库，在此基础上建立了高精度对流层天顶延迟模型和非方位对称映射函数，发表了相关研究成果，研究成果将为国家探月工程等深空探测任务中VLBI观测进行高精度对流层时延修正提供有力支撑。