通过正规方程组的组合实现多频天体参考系
Realization of a multifrequency celestial reference frame through a combination of normal equation systems
摘要：
上下文我们提出了一个天体参考系（CRF）的基础上的组合，独立的，多频率的无线电源位置目录使用近40年的甚长基线干涉测量观测在标准的大地测量频率在SX波段和约15年的观测在更高的频率（K和XKa）。最终的目录包含4617个来源。目的。我们产生了一个多频目录的所有输入目录的所有射电源位置的全部方差-协方差信息的射电源位置。方法.我们合并了三个目录，一个在8 GHz（X波段），一个在24 GHz（K波段）和一个在32 GHz（Ka波段）。而不是只使用无线电源的位置，我们开发了一种新的，严格的组合方法，通过携带完整的协方差信息，通过添加正常方程系统的过程。使用特殊的验证程序来表征输入参考系和组合星表之间的随机误差和系统误差。结果由此产生的CRF包含4617个紧凑型射电天文学物体的精确位置，其中4536个在8 GHz测量，824个源也在24 GHz观测，674个在32 GHz观测。该框架与ICRF 3在3 $μ$内对齐，并且在赤经和赤经上显示出0.1 mas的平均位置不确定性。未发现明显变形。与Gaia-CRF的比较仍然是不确定的，但是可以证明所有帧之间的显著差异。
英文摘要：
Context. We present a celestial reference frame (CRF) based on the combination of independent, multifrequency radio source position catalogs using nearly 40 years of Very Long Baseline Interferometry observations at the standard geodetic frequencies at SX band and about 15 years of observations at higher frequencies (K and XKa). The final catalog contains 4617 sources. Aims. We produce a multifrequency catalog of radio source positions with full variance-covariance information across all radio source positions of all input catalogs. Methods. We combined three catalogs, one observed at 8 GHz (X band), one at 24 GHz (K band) and one at 32 GHz (Ka band). Rather than only using the radio source positions, we developed a new, rigorous combination approach by carrying over the full covariance information through the process of adding normal equation systems. Special validation routines were used to characterize the random and systematic errors between the input reference frames and the combined catalog. Results. The resulting CRF contains precise positions of 4617 compact radio astronomical objects, 4536 measured at 8 Ghz, 824 sources also observed at 24 GHz, and 674 at 32 GHz. The frame is aligned with ICRF3 within 3 $μ$as and shows an average positional uncertainty of 0.1 mas in right ascension and declination. No significant deformations can be identified. Comparisons with Gaia-CRF remain inconclusive, nonetheless significant differences between all frames can be attested.
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