Analysis of ionospheric contributions to the Doppler shift of CW signals from artificial Earth satellites

Radio signals from artificial earth satellites propagated through the earth’s ionosphere are subjected to phase delay, refraction, and attenuation. These effects cause uncertainties in the determination of the vacuum Doppler shift of CW signals. To understand the nature of these ionospheric contributions to the Doppler shift, a theoretical expression for the refracted Doppler shift that is an inverse power series in terms of the frequency of the signal has been derived. A computer program has been written that uses ray theory in conjunction with a model ionosphere to evaluate each term of this expression. The nature of each term is discussed, and its relative importance is shown. The ionospheric contributions that are proportional to (1/ƒ) and (1/ƒ³), which result from phase delay and refraction, respectively, are the predominate terms; therefore the effects of refraction on a radio signal can be connected by using three-frequency Doppler data. The ionospheric contribution that is proportional to (1/ƒ²) is insignificant. Three-frequency Doppler data were recorded to evaluate the refraction effects in the refracted Doppler data. Two sets of experimental data are included that show the refraction effects.