PRS: Galileo, the diamond in the crown

19 January 2021

Use of satellite navigation has become such a strongly rooted habit that we have practically forgotten how to use traditional, bulky printed maps.

Many people consider satellite navigation as synonymous with GPS, which stands for Global Positioning System: the American system which is now the best-known in the world. The well-informed will know that GPS is not the only satellite system; there are other systems created to perform the same function. But few realise that one of the European Union’s biggest projects is the Galileo satellite navigation system, now fully operative in its basic form.

The Galileo programme officially began in 2003 under an agreement between the European Union (EU) and the European Space Agency (ESA).

Unlike GPS, which was developed and managed by the US Department of Defense – which controls its coverage and supply – Galileo was born and evolved under the joint control of the governments of member states and is available all over the world for dual use as a civil and military system.

Galileo may be defined in technical terms as a Global Navigation Satellite System (GNSS) programme with global coverage. Its basic features include not only great precision supplying coordinates, but extremely stable references in terms of time and frequency.

GNSS systems have a wide range of possible applications, but the most advanced and complex of these require perfect reliability of the signal received, in order to guarantee certain, reliable data at all times. This requirement is one of the principal reasons Europe decided to create its own GNSS system and achieve independence from the GPS system. The Galileo system also has a “unique” signal which cannot be fooled and may be trusted with 100% certainty.

“Open” services such as the GPS Standard Positioning System and the Galileo OS open service are very useful and easy to use, making them perfect when the associated application is not particularly sensitive, but unsuitable for highly critical purposes.

This means not only military applications, but all those in which accurate, dependable data is essential for defending the safety of people, infrastructure or economic interests.

The EU has therefore come up with a special “trusted” service, the Public Regulated Service (PRS), which has been called “the diamond in the crown” for its prestige.

Let us now look at a number of key features of the PRS:

  • It is provided under government control to authorised PRS users.
  • The service is encrypted and available only to authorised users in possession of a valid key. This means it is impossible to deceive receivers, ensuring the utmost reliability of information on users’ Position / Speed / Time & frequency (PVT)
  • Though it is in some ways similar to military GPS (robustness in relation to interference, encryption), there are several important differences. These include the fact that, unlike GPS, Galileo is under civil control, for dual use: civil and military.
  • The PRS service was designed to be perfectly compatible with GPS military services, permitting use of multi-constellation receivers simultaneously exploiting multiple secure signals. This offers obvious benefits for performance, particularly where visibility of the sky is limited or in the presence of directional disturbances such as military jammers, television/radio antennae or airport radar for civil use. It is worth noting that the USA is among the non-European countries that have requested an agreement for access to the PRS service.

Leonardo’s involvement with the Galileo PRS began just over a decade ago, with the goal of developing technology for the creation of Secure Modules.

The project was made particularly challenging by a number of basic conditions:

  • The real-time HW / SW platform needed high calculation power, but at the same time had to be efficient and capable of protecting PRS classified information against potential external attackers. This meant it was critical to work in partnership with our laboratories, taking advantage of Leonardo’s unique experience in Italy.
  • It required the know-how and infrastructure to develop algorithms to retrieve encrypted information from the PRS signal.
  • New generation techniques for processing GNSS signals and calculation methods for satellite navigation had to be developed. Building on in-house know-how, agreements were signed with national centres of excellence for the acquisition of indispensable new know-how.

Milestones in Leonardo’s participation in the Galileo programme include the successes of the GAL-PRS team in partnership with Telespazio:

  • 2012: showing the new authority responsible for PRS an initial version of the software for a PRS receiver installed on a dedicated computer.
  • 2013: first experimental CARTESIO receiver, which successfully participated in the Initial Operation Configuration (IOC) phase for the Galileo PRS, the only receiver developed by a company independently of the ESA.
  • 2014: Leonardo leads an Italian/German consortium (Airbus) which wins the GSA (European Global navigation Satellite systems Agency) P3RS-2 competition for supply of the first receivers for users.

The quality of GAL-PRS’s work in the protection of information is proven by the fact that even today, the only user receivers certified as unclassified when keyed (meaning they remain unclassified even when they contain classified keys) are those made by Leonardo. This detail permits the PRS service to be used by organisations and personnel who do not possess the requirements necessary for handling classified information.

Leonardo is now working on a new generation of PRS receivers with compact formats that may be integrated either with US military receivers, to obtain maximum performance for defence purposes, or with “open” GPS signals for non-military applications.

The entire Group is committed to Galileo with:

  • Telespazio having built one of the programme’s two control centres in its Space Centre in Fucino (the Galileo Control Centre or GCC), where the satellites in the constellation are managed.
  • Spaceopal, a joint venture of Telespazio and the German space agency, DLR, responsible for the operation and integrated logistics of the entire system and management of the global communication network.
  • Leonardo is now working on setting up PRS service management centres (Galileo Security Monitoring Centres), as it is in the unique position of being able to generate a PRS signal and simultaneously capable of receiving and decoding it – essential knowledge for continuing to grow a market that is only just beginning.

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