EDM に於ける大気補正について

概要

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The very first VLBI observation was carried out only 20 years ago. But the VLBI technique faces some difficult problems, such as measurement of propagation delay due to the atmosphere, improvement of the physical model etc. GPS interferometric observations were carried out in Japan for a variety of baseline lengths, and from this analysis it is concluded that 1∿2ppm accuracy of baseline lengths can be attainable with the GPS interferometric positioning. One of the important problems in the Electro-optical Distance Measurement (=EDM) is how to estimate the refractive index n or refractivity N (=(n-1)×(10)^<-6>) under concerned atmospheric conditions. In practise the mean refractivity N_m is calculated by the mean temperature T_m and pressure P_m averaged from the observations at the two end points. The reasonable results can be obtained by using these N_m and P_m when the observations are carried out two hours before or after the sunset or sunrise. When the observations are obliged to be carried out at other times, We need another estimation of refractivity. Kukkamaki proposed a refraction correction formula based on his empirical temperature model : t=a+bZ^c where a, b, and c are constants and Z is the height above the ground. We estimated the temperature midway between the two end points by this formula.
山口大学の論文