Satellite orbits from radio-interferometric observations

With GPS system becoming operational and with a number of new satellite projects in preparation the method for obits determination from interferometric data become more and more important. Several groups proposed their own procedures but the common problems which have to be solved are: precision of time measurements and of the frequency standards stability baseline lengths determination, correlation of parameters in the solution, influence of refraction. In the paper the aforesaid problems are discussed and solutions of different authors are compared with author's simulating calculations. The covariance analysis shows the strong influence of geometry on the solution: inter-station separation, baselines directions and network points distribution influence the solution substantially. The corrupting effect of the atmospheric refraction can be reduced to acceptable level by appropriate modelling.