Effects of the 2012–2013 solar maximum on GNSS signals in Brazil

To investigate the effects of equatorial ionospheric scintillation on GNSS signal tracking performance during the current solar maximum a research project was established between the Brazilian Institute of Geography and Statistics (IBGE), the University of the State of Rio de Janeiro (UERJ), and the Position, Location and Navigation (PLAN) Group of the Department of Geomatics Engineering, University of Calgary (UofC). This was done using intermediate frequency (IF) data processed with a software receiver and code and carrier phase data obtained using a standard geodetic receiver located at the same site. The main benefit of using a software receiver is flexibility. IF data was collected daily from 8 to 12 p.m. local time (11 p.m. to 3 a.m. UTC) using a dual-frequency front-end at IBGE facilities in Rio de Janeiro, from June 2012 to March 2013, whenever scintillation occurred. Four observation sessions were selected for processing along with another one with no scintillation, for comparison. The front-end antenna was located only 5 m away from a standard receiver antenna of the Brazilian active geodetic network, to allow a comparison of the two solutions under the same conditions. In the observation domain, the software receiver produced no actual cycle slips and only up to 4 % of missing L2 observations, indicating that the state-of-the-art acquisition and tracking algorithms used are resistant to equatorial ionospheric scintillation, whereas for the hardware receiver up to 288 cycle slips were detected and 13 % of L2 observations missing over a 4-h session under strong scintillation. The latter represents an improvement of a factor of 3 over the performance of another hardware receiver used at the same site 10 years ago during the previous solar maximum. In the position domain, Precise Point Positioning solutions using L1 code observations gave very similar results for the software and hardware receivers in all sessions, with the ionosphere being responsible for degrading coordinate accuracies up to a factor of 12. The best positioning accuracies were those given by dual-frequency solutions, at the centimeter to a few decimeters level in kinematic mode.