基于SOFA的ITRS与ICRS相互转换方法研究

基础天文标准库(SOFA)是国际地球自转服务(IERS)协议提供的关于地球姿态、时间尺度和历法的一系列程序集;国际地球参考系(ITRS)与国际天球参考系(ICRS)是描述自然天体或人造天体在空间的方向或位置,地面站或运动物体在地球上的位置和运动速度的基础参考系统。本文主要介绍了ITRS与ICRS的发展以及基于SOFA的ITRS与ICRS之间不同的转换方法的实现。     

Proper motions of 59 766 stars absolutized using galaxies in 149 sky fields (PUL2)

The PUL2 catalog has been photographically compiled in Pulkovo according to Deutch's plan. The catalog contains the mean coordinates of stars in the ICRS system at epoch J2000.0 and their original absolute proper motions. The photographic observations were performed with a normal astrograph. The first and second epochs of the photographic plates are 1937–1965 and 1969–1986, respectively. The PUL2 fields uniformly cover the northern sky. The mean difference between the epochs is 24 years. At least three pairs of plates are available for each field. There are one-hour and five-minute exposures on all plates. One pair of plates was taken with a diffraction grating. Only bright reference stars were measured on the pairs of plates with a grating. Based on a reduction model with six constants and using faint (\(15\mathop m\limits_. 2\)) reference stars, we determined the relative proper motions of the stars. We used ～700 galaxies for absolutization. The mean errors in the relative proper motions of the PUL2 stars are 5.5 mas yr^?1 (milliarcseconds per year) in μ_α cos δ and 5.9 mas yr^?1 in μ_δ. When using galaxies, the mean absolutization error is 7.9 mas yr^?1 in both coordinates. By comparing the PUL2 and HIPPARCOS catalogs, we determined the components of the residual rotation vector ω for HIPPARCOS relative to the extragalactic (equatorial) coordinate system: ω_x,y,z=(?0.98, ?0.03, ?1.66)±(0.47, 0.38, 0.42) mas yr^?1. The mean error of one absolute proper motion of a bright PUL2 star in external convergence is 9 mas yr^?1 in both coordinates.     

IAU2000决议对卫星轨道的影响

研究了IAU2000对GPS卫星轨道确定的影响。以2006年DOY186的GPS数据为例,分析了GPS卫星在IAU2000决议模型以及原有模型下,惯性参考系统以及地固坐标系中轨道的差别。结果显示,采用不同模型,卫星轨道在惯性参考系中的差值存在周期性,其中X、Z方向的幅度达到了2.5 m,Y方向的幅度约为1 m;在地固系中,轨道差别也存在周期,幅度约为4 mm。并对卫星轨道的差值进行了统计,得出了在惯性系下,不同模型引起轨道差值的3D RMS为m级。     

Astrometric control of the inertiality of the Hipparcos catalog

Based on the most complete list of the results of an individual comparison of the proper motions for stars of various programs common to the Hipparcos catalog, each of which is an independent realization of the inertial reference frame with regard to stellar proper motions, we redetermined the vector ω of residual rotation of the ICRS system relative to the extragalactic reference frame. The equatorial components of this vector were found to be the following: ω_x=+0.04±0.15 mas yr^?1, ω_y=+0.18±0.12 mas yr^?1, and ω_z=?0.35±0.09 mas yr^?1.     

Kinematic control of the inertiality of ICRS catalogs

We perform a kinematic analysis of the Hipparcos and TRC proper motions of stars by using a linear Ogorodnikov-Milne model. All of the distant (r>0.2 kpc) stars of the Hipparcos catalog have been found to rotate around the Galactic y axis with an angular velocity of M ₁₃ ^? =?0.36±0.09 mas yr^?1. One of the causes of this rotation may be an uncertainty in the lunisolar precession constant adopted when constructing the ICRS. In this case, the correction to the IAU (1976) lunisolar precession constant in longitude is shown to be Δp₁=?3.26±0.10 mas yr^?1. Based on the TRC catalog, we have determined the mean Oort constants: A=14.9±1.0 and B=?10.8±0.3 km s^?1 kpc^?1. The component of the model that describes the rotation of all TRC stars around the Galactic y axis is nonzero for all magnitudes, M ₁₃ ^? =?0.86±0.11 mas yr^?1.