摘要
用R.Bien等人的分析法计算了J_2000.0历元FK5-FK4恒星位置和自行系统差;给出了这些系统差对经典仪器的时间、纬度测定值的影响的计算公式;计算了这些系统差对1987—1988年全球经典技术确定的地球定向参数的影响.
In accordance with the recommendation by the International Astronomical Union, he IAU 1976 precession constant, the IAU 1980 nutation series and FK5 reference system have been applied to the data reduction of classical astrometry since 1984.0. However, the FK5 ca'alogue itself was not published till 1988. Therefore, only the quasi-FK5 could be adopted during this period. The quasi-FK5 was revised from FK4 by taking into account some systematic corrections such as: ——the error of FK4 zero point in right ascension, ——the effect of the E-term of aberration, ——the effect of the change of precession coustat, ——transformation of the epoch from B1950.0 to J2000.0, etc. However, the systematic difference FKS-PK4 in positions and proper motions of stars have not been included yet. This paper deals with the effects of the systematic difference FK5-FK4 on the Earth's Orientation Parameters (EOP) of 1987—1988 which were determined by the Analysis Centre of Optical Technique (ACOT) at Shanghai Observatory. By using the analytical method (Bien et al., 1978) the systematic differences FK5-FK4 (J 2000.0) in positions and proper motions are obtained and listed in Tables 1—4. At first, △α and △δ, the mean systematic differences of FKS-FK4 for the sky region covered by a group of stars, were obtained with different kinl of instruments. Then △U and △φ,the effects of △α and △δ on group results of time and latitude determinations were obtained with formulae (1), (2) and (3) for different instruments respectively. After △U and △φ were obtained for group results of time and latitude, the observational equations were constructed as X cos λ_i—Y sin λ_i+Z=(φ_(ij)—φ_(io)+△φ_(ij))—R_(ij), X sin λ_i tan φ_(io)+ Y cos λ_i tan φ_(io) +(UT1—UTC)=(UTO_(ij)—UTC+△U_(ij))—R'_(ij), where λ+i and φ_(io) are the adopted coordinates of the stations, φ_(ij) and (UTO_(ij)-UTC) are raw determinations of latitude and universal time reported by the stations, and R_(ij) and R'_(ij) are the systematic errors in latitude and time determinations. With the same weighting factors for the stations as in the routine service of ACOT, EOP at 5-day interval was solved by the least square method. By comparison of EOP obtained in his paper with those obtained routinely by the ACOT, △X, △Y and △U are drawn in Fig. 3, which shows some systematic features clearly. By comparing EOP obtained in this paper and from the routine service of ACOT with those of IERS the mean deviations and RMS are obtained and listed in Table 6. It is readily seen that the deviations of EOP obtained in this paper are smaller than those from the routine service of ACOT for all components but X component in 1988 and the RMS for both EOP are in the same level. The conclusion is that the effects of systematic differences FKS-FK4 on EOP derived by optical technique should be considered before the publication and application of FK5. The effects may reach a level of 0'.3 for X and Y and 0'.002 for UT.
出处
《天文学报》
CSCD
北大核心
1991年第2期165-175,共11页
Acta Astronomica Sinica
关键词
恒星
FK5-FK4星表
地球定向参数
Systematic Differences FK5-F K4—Determination of Time and Latitude— Earth Orientation Parameters
