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2021/07/14
Countdown team at Kourou, Guiana control center for July’s four-satellite launch. (Photo: ESA/CNES/Arianespace, P. Baudon)
By Javier Benedicto
Head, Galileo Programme department, European Space Agency
Since the declaration of initial services in December 2016, the European Space Agency (ESA) and the European GNSS Agency (GSA) have expanded Galileo’s system capabilities and service robustness with significant improvements of the ground segment and the last batch of four satellites launched by Ariane 5 in July. Once these satellites reach their final position and complete their in-orbit commissioning before the end of 2018, all 24 nominal slots of the Galileo constellation will be occupied.
Up to 22 satellites are planned to be commissioned in early 2019 and, eventually, the two FOC satellites injected in elliptical orbit should join the operational constellation after on-board software upgrade to provide for automatic health status flagging to users. This should lead to a total of 24 operational Galileo satellites supporting global PNT for users worldwide.
New Infrastructure Contracts
To further expand the system capabilities by 2020 and beyond, and reach Full Operational Capability (FOC), ESA has awarded new large industrial contracts in the context of the Exploitation Phase.
A contract to build and test another twelve Galileo satellites (so-called Batch-3) was awarded in 2017 to a consortium led by prime contractor OHB GmbH in Germany, with Surrey Satellite Technology Ltd in the UK as payload prime. These new satellites are based on the already qualified design of the previous Galileo FOC satellites. Production is advancing well, with first launch planned by late 2020.
With the Galileo constellation now expanded to 26 navigation satellites and plans to deploy additional Batch 3 satellites, the ground control infrastructure is undergoing a corresponding upgrades. In July, ESA awarded a new contract for the Galileo Ground Control Segment to GMV Aerospace and Defence, Spain. This contract includes upgrading the system architecture to manage a constellation of up to 41 Galileo satellites, updating obsolescent elements in the current system, improving operability linked to the provision of services and additional telemetry, tracking, and command capabilities to improve system robustness.
In October, Thales Alenia Space in France received a contract to upgrade the Galileo Ground Mission Segment and the Galileo Security Monitoring Centres (GSMC). This work includes upgrading Galileo’s system architecture to provide more accurate navigation products for broadcast by Galileo satellites, updating obsolescent elements in the current system and improving operability linked to the provision of services and enhanced robustness.
It will also include the construction of additional navigation message uplink and sensor stations. This contract will also augment the capabilities for implementation of the Public Regulated Service (PRS), the single most accurate and secure class of Galileo signals. Encrypted PRS signals will be made available only to authorized governmental users through approved national authorities. GSMCs in France and Spain will ensure the security monitoring functions for Galileo operational assets and manage PRS access and operations.
Growing Service Portfolio
The European Commission, GSA and ESA have jointly defined a broad range of service improvements and system capability enhancements to be deployed in 2019–2020, leading to FOC.
The newly qualified system infrastructure will support the broadcast of authentication information as part of the Open Service Navigation Message in E1; experimentation will start by end of 2019, leading to the possibility to offer trusted PNT to Galileo users.
Galileo will also be the first GNSS constellation to provide a Search and Rescue return link capability: as of 2019 the system will allow broadcast of acknowledgement of receipt message to users in distress with a very low latency, contributing to saving lives.
ESA has also started preparing the necessary modifications to the Navigation Signal Generation on-board the satellites to offer further capabilities to users after 2020. The signal-in-space will be enhanced with additional data transmitted in the I/NAV message, offering faster acquisition and more robust Galileo positioning on E1 and an encrypted navigation signal on E6 supporting authentication at signal level.
The new Galileo High Accuracy Service, soon entering the experimental phase, will consist in the delivery of un-encrypted high accuracy correction data in E6, enabling users to achieve sub-meter level positioning.
The usage of Galileo Open Service for aviation applications using horizontal advanced receiver-autonomous integrity monitoring techniques is being carefully assessed through measurements and review of the system design, including feared-events characterisation.
Longer Term Evolution
Galileo Second Generation has been the subject of technology pre-developments in the areas of platform and payload critical equipment, system techniques and processing algorithms, as well as system and segment Phase B studies over the past few years. We are now approaching the start of the implementation phase.
The European Commission, in close consultation with EU member states, has defined a decision roadmap aiming at very important future budget and programme implementation decisions in the course of 2019. In this context, ESA has launched a competitive procurement procedure for the first batch of so-called “Transition Satellites” with a broad range of enhanced and some new capabilities being considered. This includes improvements in the signal domain for faster acquisition and lower receiver power consumption, on-board clock technology, inter-satellite links, electrical propulsion, flexible payloads and power allocation by means of on-board digital technology and in-orbit re-configurability.
Transition satellites and related ground segment development contracts will begin by the end of 2019, aiming at in-orbit validation of second-generation capabilities from 2025 onwards.
EGNOS Evolution for Aviation
The adoption of Europe’s SBAS EGNOS by aviation is growing faster and faster. EGNOS will continue to evolve in the coming years. In particular, for 2019 and 2020, the evolutions under implementation focus on the obsolescence management of the hardware of some critical components, improvement of the system performances thanks to addition of new stations and system algorithms.
All these evolutions are planned to be qualified in 2021-2022, to continue to offer an excellent level of performance to Aviation Users until the operational take-over by the second generation of EGNOS V3,planned in 2025.
The European Performance-Based Navigation Implementing Regulation plans a growth from the current 35% to 66% in 2020 and 100% in 2024 of all European airports instrumental runways end-equipped with SBAS localizer performance with vertical guidance procedure.
On the aircraft manufacturer side, Airbus confirmed that it will continue equipping its aircraft; following the A350 family already equipped, both A320 and A330 families will be equipped for entry into service in summer 2020.
NAVISP
ESA’s Navigation Innovation and Support Programme (NAVISP), launched in 2017, will continue to boost member states’ industrial competitiveness and innovation in the upstream and downstream navigation sector, investigate the integration of satellite navigation with non-space technologies and complementary positioning and communication techniques, and study novel receiver-based techniques to counteract vulnerabilities and improve the robustness and reliability of GNSS.
Conclusion
The EU-built GNSS infrastructure systems EGNOS and Galileo are operational and serving users in Europe and worldwide. EC, GSA, ESA and European industries are committed to improvement plans over the next 2–3 years, with emphasis on endurance, resilience and robustness of the systems’ infrastructure, and delivering enhanced services.
For the longer term, the real challenge is to modernize the systems with new spaceborne and ground technologies, increase operational robustness and automation, and provide for additional system capabilities, while retaining a large degree of flexibility and in-orbit re-configurability to meet the long-term challenges and evolution of satellite-based navigation and timing.
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