IMPACT OF SMOOTHING TIME CONSTANTS ON GAST-E OBSERVABLES DURING SCINTILLATION EVENTS

This paper evaluates the performance of smoothing filters applied to observables used in GAST-E under ionospheric scintillation conditions. Additionally, it provides a brief overview of the current state of GBAS research and development in Brazil. Motivated by INCT GNSS NavAer interest in enhancing GNSS reliability within Brazilian airspace—and building upon national research efforts—this study investigates the behavior of smoothing filter time constants in the presence of equatorial plasma bubbles (EPBs), leading to scintillation occurrences. Data from one station of a network of monitoring stations in São José dos Campos, SP, are analyzed to assess how different time constants affect observables during ionospheric disturbances. Results indicate that longer time-constant filters effectively reduce noise during quiescent periods; however, their convergence is significantly challenged by frequent cycle slips during intense scintillation, thereby compromising their reliability for positioning solutions. These insights aim to contribute to the development of robust smoothing standards for GAST-E operations in challenging equatorial regions.