Large spatial variations in ionospheric delay of Global Navigation Satellite System signals observed during severe ionospheric storms pose potential threats to the integrity of the Ground-Based Augmentation System, which supports aircraft precision approaches and landing. Range-domain monitoring within the Ground-Based Augmentation System ground facility cannot completely eliminate all possible ionospheric threats, because ionospheric gradients are not observable to the ground monitor if they impact the satellite-to-ground lines of sight with the worst-possible geometry and velocity. This paper proposes an algorithm called position-domain geometry screening to remove potentially hazardous satellite geometries under worst-case ionospheric conditions. This is done by inflating one or more integrity parameters broadcast by the ground facility. Hence, the integrity of the system can be guaranteed without any modification of existing avionics. This paper develops an algorithm that allows the ground station to conservatively estimate the worst-case ionospheric errors for Ground-Based Augmentation System users. The results of this algorithm determine which potential aircraft satellite geometries are safe and which are unsafe, and inflation of the broadcast σvig parameter is used to make all unsafe geometries unusable for the Ground-Based Augmentation System. Although the elimination of unsafe geometries reduces system availability, this paper shows that acceptable availability for category I precision approaches is attainable at Memphis International Airport and Newark Liberty International Airport while guaranteeing system integrity under anomalous ionospheric gradients.
Bibliographical noteFunding Information:
The authors would like to thank Ming Luo at Stanford University; Mats Brenner at Honeywell; and John Warburton, Tom Dehel, Bruce DeCleene, Barbara Clark, and Jason Burns of the Federal Aviation Administration (FAA) for their help and support of this research. We also would like to express special thanks to Attila Komjathy of the NASA Jet Propulsion Laboratory for providing us with data and comments. Funding support from the FAA Satellite Navigation Local Area Augmentation System Program Office is greatly appreciated. However, the opinions discussed in this paper are those of the authors and do not necessarily represent those of the FAA or other agencies.
All Science Journal Classification (ASJC) codes
- Aerospace Engineering