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The project was launched to define a potential stand-alone Robust Timing Service for Galileo and for EGNOS.
Contract Number: Call for Tenders No 431/PP/GRO/RCH/15/8380
Project Segment: Accurate timing services
Duration: 21 months (Jan 2016 – Oct 2017)
Budget: €599 404
Project Partners: Netherlands Aerospace Laboratory (Netherlands), Finnish Geospatial Research Institute (Finland), Netherlands Metrology Institute (Netherlands), Finnish Metrology Institute (Finland) and NavCert (Germany)
Hein Zelle, NLR
European Commission Project Manager:
Kjell Arne Aarmo
GSA Project Manager:
Global navigation satellite systems (GNSS) rely heavily on accurate timing. The mechanism to determine a receiver position on Earth using satellites is based on multiple distance measurements between the receiver and a number of visible GNSS satellites. These measurements are performed as time measurements: the receiver measures the travel time of the signal from transmission (encoded in the signal), to reception. This process requires nanosecond-level timing accuracy at signal transmission (1 nanosecond at the speed of light translates into a positioning accuracy of approximately 0.3 meters). This accuracy is achieved through the use of atomic clocks on-board the satellites.
The clock in the user receiver is generally not as accurate however. To resolve this issue, additional satellites are used (4 instead of a theoretical minimum of 3) to account for the unknown receiver clock errors. The end result is that a GNSS receiver solution provides position, velocity and time (PVT). The time solution has a typical accuracy of 20–100 nanoseconds, depending on the receiver quality and environmental conditions. Effectively, the GNSS receiver is an extremely accurate clock, a feature which is heavily used in many application areas.
This project had two aims:
1. Research and development (R&D) based on users' needs for a timing service provided by Galileo and by EGNOS. This R&D focused on the development of concepts that could improve the robustness and trust of current Galileo and EGNOS timing capabilities, as this was the timing community's highest priority. The objective was to take timing capabilities to the next level by turning those capabilities into a proper Timing Service for Galileo and for EGNOS. The R&D also focused on finding additional ways to support the provision of synchronisation services.
2. Exploration of standardisation and certification options to increase user uptake and provide added value to applications using the Galileo and EGNSS timing service.
The main project outcomes were:
- A first version of a Galileo and EGNOS timing service definition was proposed.
- Robustness features for the timing service were identified and tested.
- Experimentation with real data confirmed the expected very good performance of timing solutions based on Galileo signals.
- The project concluded that standardisation would be useful for guaranteeing end-to-end performance. Several approaches can be followed for standardisation. In any case, receiver calibration is essential.
- A synchronisation concept was defined and the corresponding cost-benefit analysis was conducted.
- Additional features such as authentication and high accuracy were recommended. These could provide extra benefits and should be further elaborated with the potential of being incorporated into the final service definition.
The robust timing project defined the possible implementation of a timing service based on EGNOS and Galileo. These services can do a lot for European users of timing-critical applications. Timing services will also likely be essential in elements of European critical infrastructure elements that rely heavily on timing.
Some of these aspects will be further elaborated in a new project called 'EGNOS and Galileo service extension and consolidation'.
Disclaimer: The project results represent the views of the consortium. They do not necessarily represent the views of the European Commission and they do not commit the Commission to implementing the results.