Ionospheric refraction correction model for single-frequency Doppler navigation

In single-frequency Doppler navigation, the ionosphere corrupts results by contributing to the measured frequency shift. During high solar activity periods, uncorrected ionospheric effects produce longitude errors that are as large as 400 m. Attention is given to a single frequency correction algorithm which has the objective to remove, on the average, 50% of the longitude error attributable to ionospheric refraction, when such errors are large, without adversely affecting results at times when such errors are small or unpredictable. Applications of this adjustment should be automatic and restricted to low and mid-latitudes, daytime passes, and periods of high solar activity. The ionospheric model reported by Feen and Ebert (1979) is modified, and incorporated in the correction algorithm.