The instrumental improvements are described of the net in West-Germany for optical and radio tracking of satellites. The observed ionospheric disturbances on radio bearings are especially discussed for a frequency of 20 Mcs. The results are extrapolated to higher frequencies. The different effects on upper air densities are analysed and discussed. Four effects strongly predominate in the years 1957 to 1962. They can be well described by simple formulas. A model for the variable air drag of satellites has been developed and its numerical functions are given. This model has been proved and describes the observed acceleration of several satellites within an error of about 20%. (Author).