Error Sources of Imaging the Ionosphere and Assimilating the Ionospheric Observations from Multi-constellation/system.
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In this paper, using the International Reference Ionosphere model as the real field, ionospheric observational data from ground-based and spaceborne systems on Jan. 1st, 2008 were simulated. With the Nequick model as the background field,the global ionospheric density field was constructed by the Kalman-filter algorithm, and the subsequent work was processed. Various errors and influences in the ionospheric inversion, especially easily overlooked errors, were analyzed,and corresponding improvement methods were proposed and verified.The effects of constellation/system observations on the observation quality and spatial distribution configuration of the ionospheric inversion were analyzed.Then,the characteristics of the Kalman filter assimilation algorithm and Abel inversion algorithm were compared.
Through assimulation local areas in space were over corrected due to the effects of the top layer; these overcorrections should be reduced before processing,and the time/grid correction can effectively and steadily improve the assimilation accuracy. The introduction of COSMIC occultation data can effectively fill the void in the ocean data and increase the ionospheric observational density and horizontal accuracy significantly, and it was showed that the Kalman filter assimilation algorithm has higher accuracy,especially in ionospheric peak altitude.