The Research Of Atmospheric Refraction Delay In Space Geodetic Techniques

Along with the application and development of space geodetic techniques, the atmospheric refraction delay has become one of research directions in modern space geodetic techniques. The atmospheric refraction of electromagnetic wave is one of error resources of current space geodetic techniques, the atmospheric refraction error lies on atmospheric models and computational methods to a great extant. The influence of atmosphere to space geodetic techniques can be divided into ionosphere influence and neutral atmosphere influence according to the influence characteristic. Currently, scholars at home and abroad generally use continued fraction mapping function to get atmospheric refraction delay, the research purpose of this paper is to find out refractive delay models which have higher precision. This article firstly gives refractivity′s IUGG model at optical and near-infrared wavelengths, radio and microwave wavelengths, simultaneously gives the series expansion of the refractivity, and retains toλ-6 item, frequency correction item has been added to refractivity which caused by hydrosphere. And then analyzes and compares several commonly used zenith delay models by using measured data, gives models which have high precision and much better corrective result. It has given the curves which reflect mapping functions changing along with temperature, pressure, vapor pressure and day of year; it considers that the temperature is the biggest factor which influences the precision of the mapping functions by comparing the difference and sensitivity of several mapping functions. When elevation angle is very low, various mapping functions begin to have great difference. And then gives models which have high precision and much better result. Finally, the article describes several atmospheric refraction corrective models which work at optical wavelengths; it considers that if we want to improve the corrective precision of the models we should consider frequency relevance of the mapping functions, through comparing working at different wavelengths and the same elevation angle, or working at different elevation angles and the same wavelength.