Abstract: GBAS availability prediction is a prediction of GBAS service status and satellite constellation statue in the whole approach and guidance process of Ground Based Augmentation System(GBAS).It is an important monitoring measure for civil aviation GBAS application to assist tower monitoring personnel in monitoring.In order to ensure the reliability and safety of GBAS airborne users’ precision approach and guidance landing in terminal area,this paper proposes a usability prediction method based on GBAS ground reference position.This method predicts the status of future satellite constellation through ephemeris or almanac,relevant peaks of satellite signal,GBAS message information,and then completes the prediction of GBAS service status,So that the system can send the forecast alarm to the tower monitoring personnel in time,adjust the GBAS approach procedure,and then achieve the purpose of availability monitoring,and improve the integrity and availability of the system.

Key words: GBAS(Ground Based Augmentation System), Satellite constellation Availability, Prediction