A global model for ionospheric Faraday rotation of extraterrestrial signals

A simple program for the calculation of the ionospheric Faraday rotation is presented. The procedure is valid for geomagnetic latitudes less than 60 deg. The Faraday rotation indicates the ionospheric contribution to measured values of the polarization angle of extraterrestrial radio sources, and the ionospheric contribution must be taken into account in order to obtain accurate ground-based measurements of sources between 100 MHz and 5 GHz. The separation of the ionospheric from the extraterrestrial components is demonstrated by applying the global model to the coronal Faraday rotation experiment performed with the S-band carrier (2.3 GHz) of the Helios spacecraft during solar occultation.