The Investigative Status of the Neutral Atmospheric Refraction Delay and Its Astronomical Measure Method

Neither the astronomical atmosphric refraction correction of the classical astrometry and geodesic surveying nor the neutral atmosphric refraction delay of electromagnetic waves of modern space geodesy can meet the high accuracy requirements.The prime reason is that the astronomical atmosphric refraction and the parameter of refraction delay model can not be directly determined,and it is obliged to use the same isotropic theoretical model in all parts for correction.To improve the corrected accuracy,the experimental correcting model in different azimuth was built by the ex-post process of the determined data.According to the accuracy requirements of space geodesic surveying in the development of concerned subjects,the fact that the refraction delay quantity is related to topography around the observing station is clarified,and the necessity changing the correcting model with the observing stations and azimuths is pointed out.After analyzing several major obstacles to measuring the astronomical atmospheric refraction value directly and the existing conditions for removing these obstacles,based on the internal relations between the astronomical atmosphric refraction in optical band and the refraction delay in radio band,a new method is proposed:the determined data of the astronomical atmospheric refraction values at different station are utilized to build the observational astronomical atmospheric refraction model and refraction delay model,which change with the azimuths.In this paper,the general scheme for measuring the instantaneous astronomical atmospheric refraction and building two kinds of observational model is given.By means of this new method,the improved correction accuracy of the zenith delay will be within 1 mm,that of the refraction delay at elevation angle 5° to centimeter's magnitude,and the cut-off angle reduced to degree 5° or less.