Inside GNSS Media & Research

SEP-OCT 2018

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44 Inside GNSS S E P T E M B E R / O C T O B E R 2 0 1 8 T h e l a t e s t G a l i l e o s a t e l l i t e s , GSAT0219, GSAT0220, GSAT0221, and GSAT0222, were successfully launched with Ariane 5 ( Figure 1 ) from Europe's Spaceport located in French Guiana on the July 25, 2018. Aer their commis- sioning, the Galileo system will reach full worldwide coverage and availability with all constellation slots filled. As outlined in Table 1 , in parallel to the momentum in space, the Galileo ground infrastructure is going through important upgrade milestones, resulting in enhanced core processing facilities, and finally achieving the full redun- dancy and business continuity of the Galileo Control Centres in Italy and Germany (GCC-I and GCC-D). More operational stations have been added to the worldwide distributed network of Galileo Sensor Stations (GSS), Up-Link Stations (ULS), and Telemetry Tracking and Control (TT&C) stations. New ver- sions of the Ground Mission Segment (GMS) and Ground Control Segment (GCS) are expected to be deployed soon on the operational chain, contributing to further performance and operability improvements. System Performance Monitoring Platforms Continuous Galileo system performance monitoring and analysis is being carried out by several entities and independent processing facilities across Europe, with the main contributors as follows; 1. e Galileo Service Operator (GSOp) Spaceopal GmbH is in charge of the online mission monitoring embed- ded in the Galileo Control Centres (GCC-Italy and GCC-Germany). 2. GSA is managing the Galileo Refer- ence Centre (GRC) in Noordwijk, e Netherlands. e GRC primary function is to allow GSA, as Galileo Service Provider, to independently monitor the performance of the system and of the Galileo Service Operator (P. Buist et alia). e GRC was officially inaugurated on May 16, 2018. e current GRC v0 nucleus is already supporting the publication of Initial Open Service Quarterly Per- formance Reports on the European GNSS Service Centre (see Additional Resources). 3. ESA, as Galileo system architect, is supporting GSA and GCCs with the continuous monitoring of the system performance and functional behavior in near real time, supporting the diag- nosis and resolution of system anom- alies, managing system upgrades and associated System Integration and Verification (SIV) activities, as well as leading an end to end system reli- ability characterization in support of Safety of Life (SoL) applications. ESA is supervising two independent system performance monitoring facili- ties, which have supported the Galileo system performance verification since its early stages of development: 1. e Time and Geodetic Validation Facility (TGVF) has its core Galileo Processing Centre (GPC) located at the European Space Agency (ESA) European Space Technolog y and Research Centre (ESTEC), in Noord- wijk, e Netherlands, under a con- sortium led by GMV Madrid, Spain. 2. e Galileo System Evaluation Equip- ment (GALSEE) platform was devel- oped by Thales Alenia Space Italy (TAS-I) and is hosted in Rome, Italy. TAS-I is also leading Galileo System Engineering Technical Assistance (SETA), an industrial consortium supporting ESA in all system engi- neering and verification activities. As part of the Galileo SETA, it is important to mention the contribution provided by the performance team at Airbus Defence & Space (Ottobrunn, Ger ma ny) t h roug h t hei r i n-house expertise and Performance Assessment Facility (M. Kirchner et alia). e per- formance results provided in this article are a combination of outputs from ESA, TGVF, GALSEE, and Airbus. As illustrated in Figure 2 , TGVF is a distributed system comprising a world- wide network of Galileo Experimen- tal Sensor Stations (GESS), the Orbit Determination and Time Synchroni- zation Validation Facility (OVF), the Time Validation Facility (TVF), and the Galileo Processing Centre (GPC). Within the GPC, the Data Processing and Analysis Facility (DPAF) is the core soware element generating the system performance figures of merit in near real time and retrieving data collected in the centralized Data Server Facility. It is important to highlight that GESS stations are independent from the opera- tional Galileo Sensor Stations (GSS). TGVF is now evolving as a key exper- imentation and validation platform for state of the art algorithms, support- ing the prototyping of advanced Orbit Determination and Time Synchroniza- tion (ODTS) algorithms, as well as the Integrity Support Message for A-RAIM. e GALSEE high-level architecture is shown in Figure 3 (G. Galluzzo et alia). A key differentiator between GALSEE and TGVF is the availability of a direct interface with the Galileo Mission Seg- ment in GALSEE, enabling in-depth troubleshooting of critical ground ele- ments, such as the Orbitography and Synchronization Processing Facility (OSPF) and the Message Generation Facility (MGF). TGVF is primarily used to assess the broadcast navigation data accuracy as received by the end user, whereas GAL- SEE focuses on the functional verifica- tion of the on-ground ODTS processing leading to the navigation message gen- eration. Galileo Infrastructure Satellites 4 IOV + 22 FOC Galileo Mission Segment Fucino, Italy (GCC-I) Galileo Control Segment Oberpfaffenhofen, Germany (GCC-D) TT&C stations 6 TTC: Kourou, Kiruna, Noumea, Reunion, Redu, Papeete Up-Link Stations (ULS) sites 5 sites: Kourou, Reunion, Noumea, Svalbard, Papeete Galileo Sensor Stations (GSS) 15 GSSs. New sites operational: Papeete, Kiruna, Ascension, Azores Table 1 Galileo system overview MEASURING G ALILEO PERFORMANCE

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