The people’s navigator

Europe is building its own global satellite navigation system, Galileo, which will offer very accurate positioning and timing, under civilian responsibility. This system will be compatible with the two other existing systems, GPS and GLONASS. Users will be able to employ the same receiver to calculate their position from signals sent out by any satellite combination. However. Galileo will offer all users a bifrequency system that will allow location within one metre of accuracy – which is unprecedented for an openly accessible service.

Apart from extreme circumstances, the system will always be available and its users will be informed, in a few seconds, of any potential disruption. Thus, it will be usable for safety of life applications requiring the highest security level, such as plane landing, train circulation or car guidance.

A first Galileo satellite was launched in December 2005. This satellite, named GIOVE A (Galileo In Orbit Validation Element), marked the concrete start of Galileo in space. This successful launch managed to secure the frequencies allocated to Galileo within the International Telecommunications Union and also to check critical technologies currently under development for the Galileo system. Indeed, before having a full system operational in orbit, it is mandatory to double check any new technology; in the very hostile environment of space there is no way back, which is why everything has to be achieved step by step.

For example, with GIOVE, new types of atomic clocks are being tested, a key issue since time is at the heart of any satellite navigation system. The Galileo clocks will be accurate from one nanosecond to 10 nanoseconds over 24 hours! Also, the particular orbit chosen for the satellites has to be understood; it is the first time Europe has launched a satellite in what is called the Medium Earth Orbit (at an altitude of 23,222 km), and it is necessary to monitor the radiation encountered so as to characterise this specific environment and build the operational satellites accordingly.

The lessons learned from this phase will be implemented as follows: four satellites are to be launched to validate the basic design of the Galileo constellation and its associated ground segment. When this ‘In Orbit Validation’ phase is done, the remaining satellites will be launched to get to full operations capacity. Once fully deployed, the Galileo constellation will comprise 30 satellites (27 operational and three backup), posted on three orbital planes with an inclination of 56 degrees to the equator. This will ensure a perfect coverage of our planet.

Why Galileo?

Today, European users have no other choice than to use data provided by the American GPS or Russian GLONASS to know their position. But the military operators of both systems don’t wish to give any guarantee on the continuity of service. Satellite localisation has become the standard for high sea navigation and it will soon be standard for terrestrial airports and air traffic. If one day that signal were disrupted, a lot of sailors would find it difficult to go back to conventional methods of sailing, such as almanacs and sextants. In a few years, when satellite positioning becomes more widespread, the consequences of a signal disruption will be worse, endangering not only the efficiency of transports systems but also the security of people.

As early as the 90s, the EU understood how important it was that Europe had its own worldwide satellite navigation system. The decision to develop such a system can be compared to decisions taken in the 70s to launch other big European projects like Ariane or Airbus. The European Commission and the European Space Agency have therefore joined forces to create Galileo, an independent system, under civilian control and whose quality will be permanently guaranteed.

The Global Navigation Satellite System (GNSS) will allow the emergence of new value added services and products meant for road, rail, air and maritime transports and also for professional applications such as fishing, precision farming, oil prospecting etc. Furthermore, it will become a crucial tool for civil protection.

The social and economic spinoffs from Galileo, in Europe as in the world at large, are huge: most notably from the additional capacities that this system will bring to GNSS.

The design, development and ‘In Orbit Validation’ phase is co-financed by the European Commission and the European Space Agency (ESA) but the Galileo programme is open to the participation of the private sector notable for its operational phase. The Galileo Joint Undertaking, created by ESA and the European Commission, is currently selecting the future Galileo operator.

Waiting for Galileo, Europe is already working in the satellite navigation field: ESA, with the European Commission and Eurocontrol, is developing the European Geostationary Navigation Overlay Service (EGNOS). This is a network of ground station correcting and processing GPS signals, and transmitting the improved data via geostationary satellites. Compatible with equivalent systems in the world such as WAAS in the US or MSAS in Japan, EGNOS is expected to be declared operational this year for non safety of life applications and certified for safety of life services by 2008. Many applications have already been demonstrated, from tracking the riders on the Tour de France to guiding blind people, virtual tolling on highways and monitoring rail traffic.

This development of EGNOS is a tremendous experience, paving the way for Galileo. But, of course, if GPS is disrupted EGNOS will warn about it but will not be able to continue on its own. This is why the second step, Galileo, is necessary.

When operational – by 2010 – Galileo will allow a full set of services: from the Open service, similar to what GPS provides today but with increased accuracy, to services that GPS, a military system, cannot or does not want to offer. These include commercial services, safety of life for civil aviation, maritime transport, etc. and also the search and rescue service; a person in distress will be able to send an SOS associated to his/her position in quasi real time, a message that will be acknowledged, and the S&R team will be able to intervene rapidly in a very well defined area.

And finally, the public regulated service will be at the discretion of each European Union government for its ambulance, its customs, and its police forces.

Find out more: www.esa.int