Study of ionospheric models for satellite orbit determination

Means of improving the accuracy of the ionospheric correction of two empirical ionospheric models, the Bent (Schmid et al. 1973) and international reference ionosphere (IRI) models, have been evaluated. An improved IRI topside formula is found to minimize the tendency for the electron density profile to decrease too sharply with increasing altitude, and is shown to produce results which compare well with satellite data and ground-based incoherent scatter measurements. A model for the effective parabolic thickness is proposed for the bottomside. Comparison with results from a Meteosat tracking exercise demonstrates that the present changes improve the overall accuracy of ionospheric delays calculated using the two models.