欧空局第二代空间天体测量卫星Gaia通过张角为106.5度的两个望远镜同时对天扫描观测获得数据。此张角的精确测定是Gaia获得高精度天体测量数据的前提，特此Gaia项目中称其为基本角。Gaia发射升空后，卫星自带的星上监测系统显示基本角存在超出预期的突变、长周期变化以及振幅为1毫角秒的6小时短周期变化等，严重威胁到预期科学目标的实现。为验证这些变化是真实的基本角变化还是来自于监测系统本身，迫切需要对这些基本角变化提供独立检验。在与意大利都灵天文台多年合作的基础上，我们已获得了参与Gaia数据分析研究的宝贵机会。本项目将基于卫星两个望远镜的实测数据，独立校验并解算卫星基本角的变化，并与卫星基本角监测系统结果进行交叉对比，核实并独立获得卫星基本角变化的各种周期和振幅数据，以供Gaia数据分析处理中心对其数据进行修正。这将对提高Gaia最终星表的精度、可靠性及其它科学目标的实现有重大意义。

The ESA’s second generation of space astrometry mission--Gaia is performing its observations with two identical reflecting telescopes. The two viewing directions are separated by a so-called basic angle of 106.5 degrees. A precise determination of the basic angle variations is the prerequisite for Gaia to obtain high accuracy observations to realize its scientific goals. The on board Basic Angle Monitor (BAM) data shows that there exist jump, long-term variations and a 1 milliarcsecond amplitude, 6-h period basic-angle oscillation. An immediate question is whether this signal is caused by a real variation of the basic angle, or simply an effect of the BAM itself. Based on the cooperation with the Turin Observatory in Italy, we have obtained the opportunity to participate the Gaia satellite data analysis. Here we propose an astrometric approach to determine the basic angle variations from the astrometric observations. We expect this astrometric approach can be used to crosscheck the basic angle variations in BAM data. This will make a significant difference in improving the accuracy, reliability of the final catalog and other scientific goals of Gaia.