V. Sreeja and M. Aquino Nottingham Geospatial Institute, University of Nottingham

1. Evaluation of the Ionospheric Scintillation Effects on GNSS Receiver Tracking Performance over Latin America with Tracking Jitter Maps V. Sreeja and M. Aquino Nottingham Geospatial Institute, University of Nottingham

2. Outline of Presentation Introduction Data and Methodology Results Conclusions

3. Ionospheric Scintillation Rapid fluctuations in the amplitude and phase of transionosphericsignals caused by small scale plasma density irregularities Basu, S. et al., J. Atmos. Terr. Phys, 2002

4. Ionospheric Scintillation Effects on GNSS receivers • Significantly degrade GNSS receiver tracking performance • Code and phase tracking loop performances can be degraded • Variance of the error at DLL / PLL output (tracking jitter) increases during scintillation • Good measure of scintillation effect on the receiver

5. Data and Methodology [1] Open sky scintillation data recorded in November 2012 by PolaRxS receivers during the Fp7 CIGALA project (2010-2012) PresidentePrudente(PPTE) - located close to the Equatorial Ionisation Anomaly (EIA) crest (dip lat12.3S) São José dos Campos (SJCI) - located under the EIA crest (dip lat17.8S) Porto Alegre(POAL) - located beyond the EIA crest (dip lat20.5S)

6. Data and Methodology [2] • PolaRxS receiver signal tracking performance at GPS L1C/A evaluated by: • Tracking model of Conker et al. (2003) • Variance of tracking error at the carrier tracking loop (PLL) output Phase scintillation Oscillator noise=0.01 rad2 Thermal Noise Conker, R. S. et al., Radio Sci., doi: 10.1029/2000RS002604, 2003

7. RESULTS

8. Maps of amplitude scintillation index, S4 dip lat12.3S dip lat17.8S dip lat20.5S All satellites with elevation > 30⁰

9. Receiver PLL jitter variance Maps dip lat12.3S dip lat17.8S dip lat20.5S V. Sreejaet al., Space Weather, doi: 10.1029/2011SW000707, 2011

10. Receiver PLL jitter variance Maps: High latitude • Data from CHAIN kindly provided by Dr Paul Prikryl

11. Application of Jitter variance Maps Provide users with the information on the prevailing tracking conditions under scintillation (possibly in near-real time) Mitigate the effects of ionospheric scintillation on GNSS positioning through the strategy introduced by Aquino et al. [2009] • Stochastic model – assigns satellite and epoch specific weights based on the estimated tracking jitter • Improvement between 17% and 38% in height accuracy was obtained by this method Aquino et al. J. Geod., 83, doi:10.1007/s00190-009-0313-6, 2009

12. Conclusions PLL jitter variance maps for GPS L1C/A signal during 13-16 November 2012 over PresidentePrudente, São José dos Campos and Porto Alegre in Brazil Jitter variances calculated using the scintillation-sensitive tracking model of Conker et al. [2003] Jitter variances calculated on all the simultaneously observed satellite-to-receiver links during 13-16 November during the local pre-midnight hours are large over PresidentePrudente and São José dos Campos This indicates the likelihood for cycle slips and degradation of measurement quality, consequently degrading positioning accuracy Jitter variance maps could be useful for improving the positioning accuracy by applying weights to individual satellite to receiver links using the method of Aquino et al. [2009]

13. THANKS