Development of an Ionospheric Delay Model with Plasma Bubbles for GBAS

Susumu Saito, Takayuki Yoshihara, Naoki Fujii

Abstract:	Spatial gradient of the ionospheric plasma density is one of the most serious error source of differential GPS systems. Since Japan is located at relatively low magnetic latitudes (from 41 down to 19 degrees magnetic latitude), effects of low latitude ionospheric phenomena, especially a plasma bubble which is the region of depleted plasma density must be taken into account with great care. A 3-D ionospheric delay model which take into account the effect of the plasma bubble has been developed based on the NeQuick ionospheric/plasmaspheric plasma density model and knowledge on the plasma bubble obtained in more than 30 years history of its study. Slant ionospheric delay between a satellite and a receiver fixed on the ground with a rifting plasma bubble with a simple shape plane was calculated with our model. Temporal variation of the calculated delay looked quite reasonable compared with observed delays, although there were a number of simplifications made in our model. Difference between ionospheric delays of a fixed receiver and a moving receiver was calculated to simulate a case of the ground-based augmentation system (GBAS). Difference as much as 2 m in the slant ionospheric delay was obtained with the simple plasma bubble. Since a codecarrier divergence effect has not been taken into account, which will be soon implemented, the difference could be larger in a real case where smoothing of the pseudo-range by using the carrier-phase is adopted. Our model shows reasonable and promising performance in modeling the ionospheric delay with a plasma bubble. It is quite useful in studying effects of plasma bubbles on GBAS to implement it in low latitude region, although our model needs more improvements which are being in progress. We believe that this kind of simulating tools are very necessary to potential GBAS systems in low latitude regions.
Published in:	Proceedings of the 2009 International Technical Meeting of The Institute of Navigation January 26 - 28, 2009 Disney's Paradise Pier Hotel Anaheim, CA
Pages:	947 - 953
Cite this article:	Saito, Susumu, Yoshihara, Takayuki, Fujii, Naoki, "Development of an Ionospheric Delay Model with Plasma Bubbles for GBAS," Proceedings of the 2009 International Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2009, pp. 947-953.
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