Correlation between Ionospheric Spatial Decorrelation and Space Weather Intensity for Safety-Critical Differential GNSS Systems.

Jinsil Lee,Jiyun Lee

doi:10.3390/s19092127

Abstract

An ionospheric spatial decorrelation is one of the most dominant error factors that affects the availability of safety-critical differential global navigation satellite systems (DGNSS). This is because systems apply significant conservatism on the error source when ensuring navigation safety due to its unpredictable error characteristic. This paper investigates a correlation between GNSS-derived ionospheric spatial decorrelation and space weather intensity. The understanding of the correlation has significant advantages when modeling residual ionospheric errors without being overly pessimistic by exploiting external sources of space weather information. An ionospheric spatial decorrelation is quantified with a parameter of spatial gradient, which is an ionosphere total electron content (TEC) difference per unit distance of ionospheric pierce point (IPP). We used all pairs of stations from dense GNSS networks in the conterminous United States (CONUS) that provide an IPP separation distance of less than 100 km to obtain spatial gradient measurements under both ionospherically quiet and active conditions. Since the correlation results would be applied to safety-critical navigation applications, special attention was paid by taking into consideration all non-Gaussian tails of a spatial gradient distribution when determining spatial gradient statistics. The statistics were compared with space weather indices which are disturbance storm time (Dst) index and interplanetary magnetic field (IMF) Bz index. As a result, the ionospheric spatial decorrelation showed a significant positive correlation with both indices, especially under active ionospheric conditions. Under quiet conditions, it showed positive correlation slightly weaker than those under active conditions, and the IMF Bz showed preceding response to the spatial gradient statistics revealing the potential applicability for predicting the spatial decorrelation conditions.

Highlights

Global navigation satellite system (GNSS)-based safety-critical navigation systems are supporting world-wide aircraft operations while meeting the strict aviation requirements for various phases of flight from the en-route to the precision approach [1,2,3]
This study investigates the feasibility of utilizing space weather information for GNSS-based safety-critical navigation systems based on the well-known fact that the ionosphere is coupled to the space weather activity [18,19,20,21]
This study focuses on the relationship between the ionospheric spatial decorrelation and space weather indices which is an essential understanding for GNSS-based safety-critical systems

Summary

Introduction

Global navigation satellite system (GNSS)-based safety-critical navigation systems are supporting world-wide aircraft operations while meeting the strict aviation requirements for various phases of flight from the en-route to the precision approach [1,2,3]. There are two standardized systems from the International Civil Aviation Organization (ICAO) Standards and Recommended Practices (SARPS) [1]: the ground based augmentation system (GBAS) [4] and the satellite based augmentation system (SBAS) [5]. Both of these systems achieve the aircraft precision approach with vertical guidance meeting the integrity requirement. Integrity parameters accompany the corrections, providing information about the uncertainty of the corrections, as the corrections generated by ground systems cannot entirely capture the range error that an aircraft is experiencing

Results

Discussion

Conclusion