研制低纬子午环初衷的沿革

The Course Changes of Development of the LLMC

介绍了在低纬子午环研制过程中，如何跟踪国内外测量方法和科学技术的发展，调整该仪器的主要课题目标：开始时仅计划在低纬度地区进行天体位置的绝对测定，改善基本星表系统；在１ｍ望远镜试验ＣＣＤ底片重迭法成功后，打算把该仪器绝对测定的恒星位置与河外天体联系起来，间接地建立准惯性天球参考架；当国外传统子午环配备ＣＣＤ测微器作相对测量后，提出了在该仪器上配备ＣＣＤ测微器作绝对测定的方法，用其观测数据直接建立实用的准惯性天球参考架，并为太阳系和银河系研究提供有用数据的总体目标。

The purposes of the LLMC(Lower Latitude Meridian Circle)is to meet new demands and the development of astrometry.In the seventies,the fundamental catalogues were all compiled by the observations obtained by traditional meridian circles in high latitude regions, some systematic errors were variable with the changes among different sky regions existed in the catalogues,and the observational purpose of LLMC was to connect both observations obtained by traditional meridian circles in the south and north hemispheres and to develope the fundamental catalogue. In the middle of eighties,extragalactic radio reference frame appeared.As this frame is not available for the optical observation,the stellar positions observed by the LLMC were designed by means of the method of CCD plate overlapping to be connect with the positions of extragalactic bodies.Therefore,the absolute proper motions of some stars could be determined and a stellar reference frame could be transfered into a quasi-inertial reference frame.At the beginning of ninties,the Hipparcos satellite began to observe,and some traditional meridian circles were equipped with CCDs to do relative measurements.It is the time to observe the absolute positions of extragalactic bodies and stars by the LLMC equipped with CCD and construct directly a quasi-inertial reference frame.Furthermore,the observations can provide some useful information about our solar system, stars galaxies for astrophysics and geophysics.