Natural Signal Deformations Observed in New Satellites and their Impact on GBAS

M. Brenner, F. Liu, K. Class, R. Reuter, P. Enge

Abstract:	The Honeywell GBAS ground system SLS 4000 implements a powerful signal deformation monitor. This monitor uses measurements from multiple correlators and has been described in previous ION papers. As real satellite data was analyzed for algorithm validation in support of the FAA system design approval process establishing the integrity compliance, it was discovered that some new satellites have larger natural signal deformations than previously anticipated and that the resulting correlator measurement biases can change over time. These natural deformations do not impact satellite functionality so these satellites meet all specified tolerances. The problem identified by the FAA and associated key technical advisers (KTAs) is that firstly, such deformation although small could impact the error budget on a decimeter scale and secondly, there is no guarantee that the biases stay bounded i.e. they may gradually wander off to unacceptable levels over time. This paper explains the properties of the observed biases i.e. the threat model and demonstrates how this issue was solved in SLS 4000. This includes the technical solution to this problem and the associated assumptions that are supported in the final Honeywell safety analysis. It also includes the natural bias characterization of the satellites in the current GPS constellation.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	1100 - 1111
Cite this article:	Brenner, M., Liu, F., Class, K., Reuter, R., Enge, P., "Natural Signal Deformations Observed in New Satellites and their Impact on GBAS," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 1100-1111.
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