FY-4气象卫星定位用导航星选取方法

给出了一种导航星的选取方法,该方法以J1991.25 Hipparcos星表为中心,联合Tycho-2星表、SAO星表及Pulkovo视向速度表,通过精密历元转换至J2000.0历元时刻,引入位置精度阈值,使得高精度的恒星作为导航星,为高精度的卫星姿态反演奠定了基础;引入辅助导航星,以提高星图识别率和识别速度;通过对星图识别失败的个例分析,剔除冗余星,以进一步提高星图识别效率。189颗辅助导航星遍及全天球,其中亮于3等星的恒星占34.4%,非常有利于提高星图识别率,且弥补了部分天区恒星稀疏的不足。参考星表的不精确将引起姿态输出的误差,这是无法避免的,通过精密历元转换计算FY-4观测历元时刻的导航星精确位置,与直接利用常用星表中提供的恒星位置相比,改善了参考星的输入误差,是提高姿态确定精度的手段之一。

Guide Star Sub catalog Method for FY 4 Meteorological Satellite

A method of selecting guide star for star tracker of FY-4 meteorological satellite is proposed. This method is based on the J1991.25 Hipparcos catalog and Pulkovo Compilation of Radial Velocities for Hipp-arcos Stars, through the rigorous treatment of epoch transformation, the star's position of the FY-4 runt-ime epoch can be determined. In order to search more accurate guide star, the stars whose magnitudes arebrighter than 6.5 of J1991.25 Hipparcos catalog are chosen, and the J2000.0 Hipparcos sub-catalog is got after the rigorous epoch transformation. With the help of Tycho-2 star catalog and SAO star catalog at the same epoch, the threshold of position precision is introduced, which can meet the precision of attitude de-termination in arc-second level. The additional guide star (with star flag 5) is brought into use for impro-ving the accuracy and speed of star identification. After the cases analysis of unsuccessful star identifica-tion, the guide star which always cause false star identification is given a star flag(such as 6), which de-notes that the star is a redundant guide star and can't take part in the star identification processing.Through the introduction of redundant guide star the accuracy of star identification is improved. The 189 additional guide stars distribute all over the whole sky, even the star sparse area. And 34.4% of them are of a magnitude brighter than 3, which can improve star identification. Inaccurate reference guide star cau-ses attitude error inevitably. Comparing with the guide star position of catalog epoch, using the guide star position of FY-4 runtime epoch through rigorous epoch transformation under the limit of the threshold of position precision is a good method to improve the precision of attitude determination.