Variability of ionospheric time delay in the Mediterranean region

Faraday rotation measurements of VHF radio waves from the SIRIO satellite have been used to determine statistics of variability of ionospheric time delay in the Mediterranean region for the current solar maximum period. Results show standard deviations of up to 25 percent, or up to sixteen times ten to the sixteenth power electrons per square meter column. During daytime periods the distribution of errors about the monthly average time delay is nearly Gaussian. Modern satellite ranging systems which require correction for the effects of the time delay of the earth's ionosphere need continued high accuracy ionospheric time delay data which is available from the Faraday rotation of VHF radio waves on the SIRIO satellite.