Evaluation of Impacts of Ionospheric Scintillation Noises on GAST-D Integrity Monitors

Susumu Saito, and Takayuki Yoshihara

Abstract:	GAST-D (GBAS Approach Service Type D) is a class of GBAS (Ground-based Augmentation System) based on single-frequency signals of GNSS (L1, centered at 1.57542 GHz) and is intended to support category II/III approach and landing of aircraft. Very high level of safety required for category II/III approach and landing is required for GAST-D. Since ionospheric disturbance is one of the serious threats to GAST-D, integrity monitors are required to be equipped to GAST-D. Though the effects of anomalous ionospheric delay gradients have been relatively well studied, effects of ionospheric scintillations to GAST-D, especially to the integrity monitors, have not been studied well. Our previous study modeled the responses of the integrity monito test statistics in the periods of strong ionospheric scintillation. However, the effects include both effects by ionospheric delays that often coexist with scintillation and increased noise by degradation of code and carrier measurements. To evaluate the performance of the integrity monitors, both effects have to be distinguished. In this study, the enhancements of the noise components of the test statistics of the code-carrier divergence (CCD) monitor associated with the low latitude ionospheric scintillations were studied using the data obtained on 30 days when strong ionospheric scintillations were observed. The noise in the CCD test statistics (CCDnoise) are positively correlated with the amplitude scintillation index (S4). The noise effects of the ionospheric scintillation on the CCD monitor has been presented for the first time. However, more parameters such as C/N0 of the signals, in addition to the S4 index, appear to play roles in CCDnoise enhancement. Further detailed analysis is necessary to model the effects of scintillations to the CCD monitor test statistics. It is also necessary to evaluate the noise effects on other integrity monitors.
Published in:	Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019) September 16 - 20, 2019 Hyatt Regency Miami Miami, Florida
Pages:	2916 - 2922
Cite this article:	Saito, Susumu, Yoshihara, Takayuki, "Evaluation of Impacts of Ionospheric Scintillation Noises on GAST-D Integrity Monitors," Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019), Miami, Florida, September 2019, pp. 2916-2922. https://doi.org/10.33012/2019.16928
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