Experiences with the impedance probe on satellites

A system is presented for measuring the impedance of a dipole antenna on a satellite orbiting in the ionosphere. These impedance variations are used to determine the electron density of the ionosphere. Details of the instrumentation are given. Experimental results from many satellite flights are given in the form of antenna impedance to aid in antenna engineering. Electron density profiles are also presented. The density data show interesting spatial and temporal variations. Discussion is made of the electron density in the vehicle wake.