The production and analysis of transmission ionograms.

A transmission ionogram gives the group delay for radio pulses transmitted vertically through the ionosphere, as the radio frequency is varied. These virtual height curves may also be produced from fixed-frequency observations on orbiting satellites. Analysis of such records can give the thickness of the peak of the ionosphere, a quantity not readily obtained by other techniques. Using the ground reflection trace on topside ionograms, a rapid two-parameter analysis gives the peak thickness to better than 10 per cent.