岁差章动模型更新等因素对坐标转换的影响

Effects of Precession-Nutation Models Update,Polar Motion,Difference between UT1 and TT on Coordinate Transformation

GCRS(Geocentric Celestial Reference System,地心天球参考系)与ITRS(International Terrestrial Reference System,国际地球参考系)之间的坐标转换方法与岁差章动模型密切相关,IERS(International Earth Rotation and reference systems Service,国际地球自转与参考系服务)规范先后推荐了3组不同的岁差章动模型。论文分析了基于春分点的坐标转换过程,在比较3组岁差章动模型间差异的基础上,以太阳系10个天体为例,计算了岁差章动模型更新、极移、世界时与地球时差值等因素对坐标转换影响的具体数值。结果表明,IAU 2006岁差-IAU 2000AR06章动与IAU 2000岁差-IAU 2000A章动间的差异,对坐标转换的影响在0.5mas以内;而IAU1976岁差-IERS 1996章动与前2组岁差章动间的差异,对坐标转换影响的最大值达到37mas;极移对坐标转换影响的最大值达到0.6″,远高于岁差章动模型更新所带来的影响;当忽略世界时与地球时的差异时,结果完全错误。通过此分析,明确了极移、世界时与地球时的差异对坐标转换影响的具体数值,可为工程计算中岁差章动模型的选取提供参考依据。

Method of coordinate transformation between GCRS （Geocentric Celestial Reference System） and ITRS （International Terrestrial Reference System） is closely related to precession-nutation model. IERS （International Earth Rotation and Reference Systems Service） Conventions recommends three different kinds of precession-nutation models. This paper analyzes the spring equinox-based coordinate transformation process. On basis of comparison of the difference between the three models and taking ten celestial bodies in solar system as examples, we have compu- ted the values of effect on coordinate transformation generated by precession-nutation model update and polar mo- tion. The results show that the difference between IAU 2006 precession-2000AR06 nutation and IAU 2000 precession- 2000A nutation has an effect of within 0.5 mas on coordinate transformation. The difference between IAU 1976 pre- cession-IERS 1996 nutation and the two former precession nutation models has an effect the maximum value of which reaches 37 mas. The polar motion has a much greater effect on coordinate transformation and it could reach 0. 6 ＂, much higher than the effect of precession-nutation update. The results would be thoroughly wrong if the difference between TT and UT1 is neglected. The research conclusions provide reference to selection of precession- nutation models in engineering calculation, and give specific values of effects of polar motion and difference between TT and UT1 on coordinate transformation.