Estimating Electron Content Of The Ionosphere

Method for estimation total electron content of ionosphere. Based on measurements of signals transmitted from global positioning satellites (GPS's). Ionospheric delays obtained by measuring differential arrival times of signals at two different frequencies. Since GPS observations cover certain regions of sky, location of space probe to be calibrated might not overlap GPS field of view. Certain assumptions made about behavior of ionosphere so total electron content estimated in any direction from receiver.