The development of an ionospheric anomaly threat model is required to design an ionospheric anomaly monitor for Ground-Based Augmentation System (GBAS), which supports aircraft precision approach and landing. The Korean CAT-I ionospheric anomaly threat model was built to certify CAT-I GBAS operations in the Korean region. However, this model has different bounds from those of the current GBAS ionospheric threat model for the Conterminous United States (CONUS). Thus, an analysis of the GBAS performance is necessary when the Korean ionospheric threat model is applied to GBAS. This paper presents a methodology for evaluating GBAS availability based on the Korean ionospheric threat model. The methodology consists of three steps: Calculation of the ionospheric-induced range and position errors under the worst-case ionospheric scenario, determination of the worst-case inflation factor with ionospheric threat mitigation considering runway configurations and GBAS service coverage, and an analysis of GBAS availability by comparing the inflated Vertical Protection Level (VPL) to the Vertical Alert Limit (VAL). This methodology can be utilized to evaluate the performances of global and regional ionospheric threat models in the future.

Keywords: ground-based augmentation system, ionospheric anomaly threat model, ionospheric threat mitigation