@InProceedings{PaulaKantReze:2004:ChGPSi,
               author = "Paula, Eurico Rodrigues de and Kantor, Ivan Jelinek and Rezende, 
                         L. F. C. de",
          affiliation = "{Divis{\~a}o de Aeronomia}",
                title = "Characteristics of the GPS signal scintillation during ionospheric 
                         irregulaties and their effects over the GPS system",
            booktitle = "Anais...",
                 year = "2004",
         organization = "Simp{\'o}sio Brasileiro de Engenharia Inercial (SBEIN), 4.",
             abstract = "The ionospheric irregularities can give origin to amplitude and 
                         phase scintillations in the GPS signal and can affect 
                         telecommunication systems. In this work we present briefly the 
                         physical mechanisms that give origin to the ionospheric 
                         irregularities, and their dependence with season, local time, 
                         solar activity and magnetic activity. Following we will describe 
                         the potential effects of the scintillations on the GPS systems, 
                         like the loss of lock, increase of the dilution of precision 
                         (DOP), decrease on the available number of GPS satellites and 
                         effects on the WAAS (Wide Area Augmentation System) navigation and 
                         positioning system. This study was based on L1 (1.575 GHz) GPS 
                         signal amplitude scintillations measured by an array of 11 
                         Scintillation Monitors located over the Brazilian territory. The 
                         GPS data were recorded at 50 samples/sec and the scintillation 
                         index S4 was used to quantify the scintillation intensity. Over 
                         the Brazilian territory the ionospheric irregularities incidence 
                         is normally from September to March, however they can be triggered 
                         at any month of the year during the incidence of a magnetic storm. 
                         The ionospheric irregularities incidence and intensity increase 
                         with the increase of the solar cycle. The irregularities are 
                         generated at equatorial region after sunset due to plasma 
                         instability processes and they occur in the pre-midnight time 
                         sector and after midnight during some magnetic storms. The 
                         ionospheric irregularity amplitudes are largely dependent of the 
                         ionospheric background ionization and over the Brazilian territory 
                         there are large ionization gradients from equator to low latitudes 
                         due to the Equatorial Anomaly. Due to this anomaly the Total 
                         Electron Content (TEC) presents 2 peaks at about 15o S and 15 o N 
                         of magnetic latitude and a decrease at equatorial latitudes, and 
                         as a consequence the ionospheric irregularities give origin to 
                         larger amplitudes close to these crests. For instance stations 
                         like S{\~a}o Jos{\'e} dos Campos and Cachoeira Paulista are 
                         under the Equatorial Anomaly peaks. The ionospheric irregularities 
                         can cause large fades on the GPS signal for stationary receivers 
                         that can cause losses of lock (tracking) that can persist for tens 
                         of seconds. As the ionospheric irregularity patterns (bubbles) 
                         drift in the east-west direction with about 150 m/s, for moving 
                         receivers like landing aircrafts, which have almost same velocity, 
                         the fades can be potentially much longer causing even longer 
                         tracking losses. In this work we show some statistics of loss of 
                         lock occurrence during ionospheric irregularities. One consequence 
                         of tracking loss is an increase in the dilution of precision due 
                         to the GPS satellite loosing, what increases the navigation 
                         errors. In severe conditions of irregularities incidence the 
                         number of tracked satellites may fall below 4 that is the minimum 
                         amount for calculating navigational solutions.",
  conference-location = "S{\~a}o Jos{\'e} dos Campos",
      conference-year = "17 - 19 nov.",
           copyholder = "SID/SCD",
             language = "pt",
         organisation = "Instituto Nacional de Pesquisas Espaiciais",
           targetfile = "De Paula et Rodrigues et Kantor.pdf",
        urlaccessdate = "16 jun. 2024"
}