The Galileo Signal Authentication Service (SAS) is the next new feature to be offered by Galileo, the European GNSS. Its signal-in-space initial capability is expected already in the next months of 2025, starting with the L3 (Launch 3) Galileo elliptical-orbit satellites. It is the first-ever navigation signal authentication feature offered globally and openly. Galileo SAS uses the existing Galileo E6-C signal to be encrypted, in combination with OSNMA (Open Service Navigation Message Authentication), through the so-called semi-assisted authentication concept. In this concept, portions of the E6-C are re-encrypted with OSNMA future keys and published in a server. The concept allows signal authentication openly and for free, and without private key management by users. In exchange, the time between authentications is 30 s, inherited from OSNMA, and it introduces a latency between the E6-C signal reception and its authentication down to a few seconds. This work presents the status of Galileo SAS. It outlines its latest technical definition, already shared in previous publications. It will also present the MMARIO (Message and Measurement Authentication Receiver for Initial Operations) project, developing the first SAS server, receiver and testing platform. The paper also outlines the Galileo SAS plans for the near future, up to the Initial Service Declaration.

This work presents the probability of a Galileo receiver calculating a position fix and an OSNMA (Open Service Navigation Message Authentication) position fix in different environments, including discontinuous signal reception. To complement real-data tests already available, the results are based on simulations using AWGN (Additive White Gaussian Noise) and simplified LMS (Land Mobile Satellite) channels, combined with assumptions on satellite visibility to model opensky, urban and hard urban environments. TTFF (Time To First Fix) and TTFAF (Time To First Authenticated Fix) are compared for each environment for a 10 -minute window, corresponding to the usual navigation refresh rate. While the results focus on corner cases where the TTFF is achieved within the window, but not TTFAF, identifying the reasons, in most cases TTFF and TTFAF are both achieved.

The Galileo High Accuracy Service (HAS) has been operational since January 2023, offering good and stable performance. The next phase of HAS is currently being implemented, offering enhanced performance and new functionalities. One of the improvements in HAS Phase 2 will be the provisioning of ionospheric parameters to users in the European Coverage Area (ECA). This paper focuses on the new Message Type 2 (MT2) which will contain the ionospheric parameters, i.e., ionospheric vertical delays (IVDs) and ionospheric vertical accuracies (IVAs). IVDs and IVAs will be provided for ionospheric grid points (IGPs) which receivers in the ECA can see down to a certain elevation. Data for two ionospheric layers is planned to be provided. Because transmitting the IVDs and IVAs for a vast number of IGPs requires a significant amount of bandwidth, an investigation was also launched into different approaches for compressing the IVD data. To assess the efficacy of the compression, the percentage decrease in size was assessed through post-processing of historical data. Compared to non-optimized encoding of the IVDs using a fixed number of bits, processing of historical data showed a median IVD block size reduction of about 27% and 41% under solar maximum and solar minimum conditions, respectively. The IVD block compression approach will be evaluated further during the HAS Phase 2 implementation.

The European Commission (EC) is taking steps towards the implementation of a Galileo Timing Service. This service is now formally part of the mission of the Galileo Second Generation, and it puts emphasis on serving critical infrastructure. Implementing a proper service implies putting all the necessary elements in place to be able to meet the defined level of performance. In order to ensure the correct processing of the service’s signals and a minimum level of performance of the user receiver, corresponding standards are needed. Therefore, a fundamental element in the Galileo Timing Service concept is the standardization of Galileo Timing Receivers. The STARLITE project (Preparation of Standards for Galileo Timing Receivers) funded by the EC is the first international initiative to develop standards for GNSS Timing Receivers. The target users for the standard are all Galileo Timing users, with a special focus on critical infrastructure within the telecommunications, finance and energy sectors. The standard leverages the specificities of the Galileo Timing Service. This will become fundamental in order to ensure the end-to-end performance for those users operating a receiver compliant with the standard. At the same time, the standard allows the use of other systems to further enhance the performance. The project helped to establish a formal Working Group (WG9) for the development of the standard under CEN/CENELEC JTC5.

The European Navigation Conference 2023 (ENC 2023) took place at the European Space Research and Technology Centre (ESTEC) of the European Space Agency (ESA) in Noordwijk, The Netherlands, from 31 May until 2 June 2023