Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008acasn..49..107m&link_type=abstract
Acta Astronomica Sinica, vol. 49, no.1, p. 107-112
Astronomy and Astrophysics
Astronomy
2
Atmospheric Effects, Methods: Numerical
Scientific paper
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 1cm 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 R0 (Z) is the instantaneous astronomical 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 H.S. Hopfield, and computed the path-curving corrections ds1 and ds2, respectively. These corrections at six major zenith distances are listed in table 1. Furthermore, for comparison we also list the calculated values of ?? with the formulae of Haojian Yan 1995, and the values given in Yanxing Li et al.2002.
Mao Wei
Tie Qiong-Xian
Yang Lantian
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