电磁波折射延迟的弯曲改正  

The Path-curving Correction in Refraction Delay of Electromagnetic Wave

作　　者：冒蔚[1] 杨磊[1] 铁琼仙[1] 

机构地区：[1]中国科学院国家天文台云南天文台,昆明650011

出　　处：《天文学报》2008年第1期107-112,共6页Acta Astronomica Sinica

基　　金：云南省基金(2005A0010R)资助项目

摘　　要：针对中性大气折射延迟改正中压缩截止高度角和提高改正精度的要求,推导了电磁波折射延迟中由天文大气折射引起的路径弯曲改正的计算公式,这是在许多理论模型中给出中性大气折射延迟改正的公式时,都会在主项后边给出的,却又因为它是小量而常被忽略的一项改正.实际上,在不太低的高度角,例如15°,这一项就达到1cm量级,是不能忽略的.李延兴等人专门对这一改正作了推导,给出了逐步逼近的计算方法和计算值;严毫健也曾给出了直接计算的公式,计算结果却比李延兴等人的小3倍多,这说明对该项改正有必要作进一步的研究,拿出简便可靠的计算公式.In many theoretical modes of the neutral atmospheric refraction delay of electromagnetic wave, the path-curving correction usually came out behind the primary correction of the refraction delay, but it was always neglected because it is a small correction. The formulae and the computed correction values were not encountered in papers of foreign researchers. In fact, it is about lcm at elevating angle of 15° and about 20cm at 5°, so it can not be neglected on the low elevation. A progressive approximate calculation method （i.e. the Equations （1）-（3） in this paper.）and the computed values for this correction were given in Yanxing Li et al. 2002[1]. The formulae for direct calculation of the path-curving correction were given in Haojian Yan 1995[2] （i.e. the Equations （4）--（8） in this paper） in which the computed values are much smaller than that given in Yanxing Li et al.2002. These results indicate that the path-curving correction should be further studied, and the convenient and reliable formula should be given. In the light of the requirement to reduce the cut-off of height angle and to improve the correction accuracy, the rigorous calculating formulae of the path-curving correction in the refraction delay of electromagnetic wave is derived in this paper, that is the Equation （13）, where Ro（Z）is the instantaneous astronom- ical refraction on the zenith distance Z of observational object. The astronomical refractive values in the state of the standard atmosphere are obtained from the local observational model of the atmospheric refraction or a precise atmospheric refraction table, and must be corrected by the temperature and pressure of the observation. H is the effective height of atmosphere, being computed theoretically by the local atmospheric distribution model. We get the astronomical refractive values in the state of the standard atmosphere from Purkovo atmospheric refractive table, and use the effective heights of atmosphere H = 7469.9 of Yanxing Li et al. and HH=7972.5 of

关 键 词：大气效应 方法 数值 

分 类 号：P124[天文地球—天体测量]