Extension of the coordinate parameterization of radio sources observed by VLBI (ECORAS)

光学天体测量卫星使命盖亚（欧空局）将提供射电源的位置和自行，其精度可与目前的VLBI（甚长基线干涉测量）相媲美，甚至更高。在ECORAS项目的第二阶段，盖亚和VLBI天体坐标的比较将用于确定系统参考系效应，如银河系畸变，原始引力波，引力透镜和星际物质引起的类似变形。比较还将揭示VLBI和盖亚坐标可能的技术依赖性系统误差的重要细节。实现这些重要科学目标的步骤是探测、模拟和校正射电源结构对天体坐标和观测量的影响。由天体物理过程引起的内在结构的演化可以引起非常大的表观自行，因此，需要考虑它以进行精确的比较。同样，这种比较需要VLBI和盖亚参考框架的准确定位。ECORAS项目第二部分的重点是两个无线电和光学波长为基础的框架的对齐。根据观测频率的不同，同一天体很可能出现在不同的位置，这是无线电参考系和光学参考系精确联系时需要考虑的一种影响。

The optical astrometric satellite mission Gaia (ESA) is going to provide positions and proper motions of radio sources at a level of precision comparable to current VLBI (Very Long Baseline Interferometry) or even better. In the 2nd phase of the project ECORAS, the comparison of the Gaia and VLBI celestial coordinates will be exploited for the determination of systematic reference frame effects, such as the Galactic aberration, primordial gravitational waves, gravitational lensing and comparable deformations due to inter-stellar mater. The comparison will also reveal important details about possible technique-dependent systematic errors of the VLBI and Gaia coordinates. Steps towards these important scientific goals are the detection, modelling and correction of radio source structure effects on celestial coordinates and observables. The evolution of intrinsic structure caused by astrophysical processes can cause very large apparent proper motions and hence, it needs to be considered to enable the precise comparisons. Likewise, the comparison requires an accurate orientation of the VLBI and Gaia reference frames. In the focus of the second part of project ECORAS is the alignment of the two radio and optical wavelengths-based frames. The same celestial object is very likely to appear at different positions depending on the observed frequency, an effect that needs to be considered for the precise tie of radio and optical reference frames.