Gaia data release 2 (DR2) provides the best non-rotating optical frame aligned with the radio frame (ICRF) thanks to the inclusion of about half-million quasars in the five-parameter astrometric solution. We cross-match with Gaia DR2 the quasars from Large Quasar Astrometric Catalogue, Sloan Digital Sky Survey and LAMOST, obtaining 208,743 new sources (denominated as KQCG), and most of them are fainter than G = 19. Given their crucial diagnostic role for characterizing the properties of the celestial reference frame, we aim to probe more accurately the properties of the reference frame at the faintest magnitudes. Combining them with the quasars already identified in DR2, we estimate the moving mean of parallaxes and proper motions. The features of the proper motion are analyzed by means of vectorial spherical harmonics; the scalar field of parallaxes is expanded into spherical harmonics to investigate their spatial correlation, which reveals an angular scale of systematics of ≈18 with a rms amplitude of 13 μas. The global moving mean of the parallaxes and proper motions are calculated. The amplitude of proper motion bias can be up to ∼10 μas yr⁻¹ in some sky regions for both components, and these biases seem to be related to the patterns of the scanning law. The reference frame exhibits a (−6, −5, −5) 1 μas yr⁻¹ spin in the northern hemisphere and a spin of (0, +1, +3) 1 μas yr⁻¹ in the southern one, which may be caused by the star contamination. The quadrupolar anisotropy of the proper motion filed is analyzed, where a significant quadrupolar signal (the largest component’s amplitude is up to −15 μas yr⁻¹) is found.

Gaia数据发布2（DR2）提供了与无线电帧（ICRF）对齐的最佳非旋转光学帧，这是因为五参数天文解决方案中包含了约50万类星体。我们与Gaia DR2进行了大类星体占星学目录，Sloan Digital Sky Survey和LAMOST的类星体的交叉匹配，获得了208,743个新来源（称为KQCG），其中大多数比G更暗=19。鉴于它们在表征天体参照系特性方面起着至关重要的诊断作用，我们的目标是在最微弱的幅度下更准确地探测参照系特性。将它们与DR2中已经确定的类星相结合，我们估计了视差和适当运动的移动平均值。通过矢量球谐函数分析适当运动的特征；视差的标量场扩展成球谐调查其空间相关性，与RMS幅度13的揭示的≈18系统学的角度刻度μ为。计算视差的整体移动平均值和适当的运动。适当的运动偏压的幅度可高达〜10 μ为年^-1这两个分量在某些天空区域中都存在，这些偏差似乎与扫描定律的模式有关。该参考系在北半球的yr ^-1自旋为（-6，-5，-5）1μ，在南部的yr ^-1自旋为（0，+1，+3）1μ，这可能是由恒星污染引起的。提交的适当运动的四极各向异性进行了分析，其中四极显著信号（最大部分的振幅为至多-15 μ为年^-1）被发现。