Equatorial Plasma Depletions Observed Over Brazil - Impact on Safety Critical GNSS Navigation

T. Dautermann, C. Mayer

Abstract:	We present measurements of a plasma bub- ble observed over Brazil on 2 October 2005 and characterize the bubble parameters in slant iono- spheric delay with the software used for generat- ing the GBAS threat model for Germany. Iono- spheric gradients within the bubble range from 32 to 152 mm/km, the velocity of the bubble is east- ward with its magnitude decreasing from 176 to 85 m/s. At the same time, the bubble depth in- creases from -1 m to -1.9 m. Moreover, we present a observed plasma irregularity with strong gra- dients around 340 mm/km. We use the bubble depth parameter as measured in a simulation of GBAS approaches conducted worldwide on 2 Oc- tober 2005 with the worst case assumption that the bubble travels eastward with the IPP such that the bias remains on the aircraft-satellite link till decision height. In this simulation mislead- ing information was observed frequently but haz- ardous misleading information did never occur. We resample the observed data at 2Hz and tested the standard GBAS code-carrier divergence mon- itor which did detect the observed plasma bub- ble on PRN28. Lastly, a simple threat model for plasma bubbles a_ecting GBAS is proposed.
Published in:	Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010) September 21 - 24, 2010 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2583 - 2591
Cite this article:	Dautermann, T., Mayer, C., "Equatorial Plasma Depletions Observed Over Brazil - Impact on Safety Critical GNSS Navigation," Proceedings of the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2010), Portland, OR, September 2010, pp. 2583-2591.
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