GRC-MS project consisted in controlling the quality and completeness of the European Galileo global navigation system observations. It is a long-term program, implemented in annual grants awarded by EUSPA (European Union Agency for the Space Programme), which allowed the requirements to be adapted to the changing conditions and development of the Galileo system. The project was intended to support the GRC (Galileo Reference Centre) organized by EUSPA, established on the basis of the European Union regulations concerning GNSS (Global Navigation Satellite Systems). The GRC-MS project was designed to enable monitoring of the Galileo system by research institutes from European Union countries, independently of the system administrator.

CBK PAN participated in the project since autumn 2018 and took a part in four packages related to the analysis of the Galileo system. The first task included work on providing measurement data from the CBKA station, located on the roof of the CBK PAN building in Warsaw. The Trimble NetR9 receiver collected data with an interval of 30 s; daily RINEX files were sent to a server prepared by BKG (Bundesamt für Kartographie und Geodäsie), whose task was to prepare and run a collection service for data, calculated products and reports. The second task was to create an assimilated model of the ionosphere for Europe. The H2PT model was based on GNSS observations and data from ionosondes. It provides the height of a single layer of the ionosphere and the TEC (Total Electron Content) value for the assumed geographic grid nodes (5° × 5°), with a time resolution of 15 minutes. Another task included work on monitoring the Galileo system’s KPIs (Key Performance Indicators). CBK PAN dealt with the determination of the following indicators:

• SISE (Signal in Space Error) parameter for single frequencies E1, E5a, E5b and frequency combinations E1E5a, E1E5b;
• availability of OS DF (Open Service Dual Frequency), i.e. at least one dual-frequency combination (E1E5a, E1E5b) for the entire system operation area;
• availability of PDOP (Position Dilution of Precision) below 6 for the entire system operation area;
• accuracy of determining the horizontal and vertical position for selected 14 permanent GNSS stations, using the SPP (Single Point Positioning) method:
• dokładność wyznaczania pozycji poziomej i pionowej dla wybranych 14 stacji permanentnych GNSS, przy użyciu metody SPP (Single Point Positioning):
  • for the E1 frequency using the NeQuick-G ionosphere model,
  • for linear combinations of frequencies E1E5a and E1E5b – iono-free, removing the main part of the ionosphere influence;
• accuracy of 3D velocity determination for selected GNSS permanent stations (based on Doppler shift, for E1 frequency and E1E5a and E1E5b combinations).

These parameters were determined for each day and month of the project, the results were sent to the project server as monthly summaries.

As part of the last task, the NeQuick-G model transmitted in the navigation message by Galileo satellites was compared with the profile obtained from the vertical ionosphere sounding by the ionosonde in Warsaw, as well as with the H2PT model determined for Europe.

Moreover, after the end of each quarter, reports containing quarterly statistics of the maps, parameters and comparisons as well as descriptions of special cases detected during daily and monthly calculations and analyzes were prepared.

Additionally, at the request of the EUSPA (European Union Agency for the Space Programme), detailed analyzes were carried out for multipath effect in the case of station localized in CBK, and for the noisy behavior of the station KOUG (Kourou, French Guiana) on the E1 frequency; it was also checked whether the difference of all the stations behavior in terms of HPE (horizontal position errors) and VPE (horizontal position errors) for E1 frequency during the quarter is related to the NeQuick-G model.