Galileo is fast for every user

The improvement comes from a new feature called ‘I/NAV’ for an improved navigation message, which was first shown on two Galileo satellites that were launched in December 2021 and entered service last summer. ESA as the Design Authority of the Galileo program contributed to the delivery of the improved navigation message ‘I/NAV’ starting from the design phase, the implementation of the satellite and the ground component, the qualification of the implementation and the orbit test.

Galileo’s service provider, the European Union Space Agency, EUSPA has now upgraded all other Galileo FOC satellites in service to broadcast this enhanced search message.

This improved search message improves Galileo’s time to fix the first location by two or three times – depending on whether the receiver is in the countryside or in a more difficult urban area.

This is made possible by improving the message’s ability to correct decoding errors and recover lost data. At the same time the receivers can get fast access to the ultra-accurate Galileo Time System without having to set up the whole search message.

ESA uses the Galileo Time and Geodetic Validation Facility – an independent network of monitoring stations around the world – to check the accuracy of the broadcast data and its relative performance. Their analysis showed that all the distribution data was correct. Also, the limited functionality of the new data is fully consistent with the functionality targeted in the design phase.

Meanwhile, ESA’s Navigation Laboratory, based at ESTEC in Noordwijk, the Netherlands, has deployed its Telecommunications and Navigation Testbed Vehicles on drives across the Dutch countryside to the center of Rotterdam to ensure improved functionality for various users.

These testbed vehicles include different types of satnav receivers and cameras and sensors to record all the details of the surrounding area.

Stefan Wallner, head of ESA’s Galileo G1 Signal in Space Engineering Unit explains: “Galileo signals provide the highest precision in the world, down to the decimetre-scale.

“In order to benefit from the excellent accuracy of the Galileo system, the user must also receive a consistent flow message from the Galileo signal and in challenging user environments – so the faster the better. In the Galileo search message, there was enough data volume available to justify this improvement.”

At the same time, these new elements in the ‘I/NAV’ message must be fully backwards compatible with the legacy receivers, so that the update does not affect their performance and functionality. Before the start of deployment, ESA in cooperation with EUSPA and the EC’s Joint Research Center (JRC) carried out intensive test campaigns covering a wide number of commercial Galileo receivers and successfully demonstrated that the new I/NAV message does not have any negative impact on them.”

The I/NAV upgrade is based on a trio of innovations.

• I improved time to fix the starting point it comes by reducing the amount of information required for the receiver to generate an initial fixation point, at the cost of a corresponding decrease in initial accuracy. This leads to the first correction within a few seconds, with a circular error of less than 4.5 m, it decreases continuously until it reaches the standard level of submeter accuracy after the reception of the complete message of the movement of Galileo.
• I/NAV’s improved fitness comes from a new coding method that introduces additional redundancy in the search message, so any lost or corrupted data – either blocked by high-rise buildings or reflected in polished artificial surfaces – can be easily recovered.
• At last, Time of the Galileo System made available to receivers without the need to fully decode the search message by introducing it as a ‘secondary synchronisaton pattern’ within the message, accessible in a few seconds. This is especially interesting for receivers who return a message to navigate through Galileo via the Internet or a parallel communication network and therefore miss the correct link to the Galileo System Time to provide the first correction.

The data collected through this current monitoring campaign is used to implement a set of recommendations for chipset manufacturers to increase their performance of I / NAV features.

All the information necessary to implement and achieve the improvement of the I/NAV message can be found in the Galileo Open Service Signal in Space Interface Control Document. The next version of the Galileo Open Service Definition Document will provide an indication of the expected functionality to be found in the enhanced I/NAV message.

About Galileo

Galileo is now the world’s most accurate satellite navigation system, serving four billion users worldwide since entering First Services. All smartphones sold in the European Single Market are now guaranteed to be Galileo enabled. In addition, Galileo makes a difference in all fields of railway, maritime, agriculture, financial services and rescue operations.

Galileo is a flagship program of the EU Space Programme, managed and funded by the European Union. Since its inception, ESA has led the design and development of space and ground systems, as well as acquisition and launch. EUSPA (EU Space Program Agency) acts as a Galileo service provider, dealing with the market and application needs and closing the loop with users.

For more information about Galileo: https://www.usegalileo.eu/EN/.