中文摘要：

大气折射率的各向异性问题是目前空间大地测量技术中非常重要的课题．从天文观测的角度分析了长期以来不能直接测定天文大气折射值的几个主要障碍，介绍了现已具备排除这些障碍的条件．基于中国科学院云南天文台低纬子午环的特殊功能，以及新的仪器误差理论，给出了专用测量仪器的设计方案和实测天文大气折射值的基本原理．根据长期观测的数据表明，利用低纬子午环的测量原理测定瞬时大气折射值是可行的，可以建立随测站和随方位而异的大气折射实测模型．给出了云南天文台的东南西北4个方向的天文大气折射实测模型．

英文摘要：

The atmospheric refractive index anisotropy is a key problem in space geodetic technology. Several major obstacles resulting in no direct measurement of the astronomical refraction since a long time are analyzed in the view of astronomical observation, and necessary conditions now possessed to remove these obstacles are described. Based on special functions of the Lower Latitude Meridian Circle （LLMC） in Yunnan observatory, NAOC and according to a new instrumental error theory, a design plan of the special measuring instrument and a basic principle for measuring the refractions are presented. Long - term observed data indicate that it is feasible to determine instantaneous atmospheric refractions by the observation principle of the LLMC. Measured models of atmospheric refraction can be built consequently varied with change in observation station and azimuth. Furthermore, local measured refraction models in four directions of the east, west, south and north in Yunnan observatory are presented.