What is Galileo?

Galileo will be a global network of 30 satellites providing precise timing and location information to users o­n the ground and in the air. It is costing some 3.4bn euros (£2.3bn; $4bn) of public and private investment and represents the biggest space project yet undertaken in Europe.

Galileo's first demonstrator spacecraft was launched o­n 28 December; a second platform will follow in the New Year. They will trial the in-orbit technologies needed to run the system. These include atomic clocks, the heart of any global positioning system.

If all goes according to plan, a full constellation of Galileo satellites will be in operation by the end of 2010.

Why does Europe want Galileo?

On an important level, Galileo is a political project.

GALILEO UNDER CONSTRUCTION A European Commission and European Space Agency project 30 satellites to be launched in batches by end of 2010 Will work alongside US GPS and Russian Glonass systems Promises real-time positioning down to less than a metre Guaranteed under all but most extreme circumstances Suitable for safety-critical roles where lives depend o­n service

GPS is a military-run programme; its signals can be degraded or switched off. Yes, the service is free, but its continuity and quality come with no guarantees - which means it cannot be relied upon, certainly not for safety-of-life applications such as landing planes and controlling trains (not without augmentation).

Galileo will be a civil system. It will be run by a private consortium and will offer guaranteed levels of service.

How will Galileo differ from GPS?

As brilliant as GPS is, its accuracy and availability can o­n occasions leave a lot to be desired, as anyone who has a receiver will know. Sometimes it can be very difficult to get a fix and the accuracy can drift out to 10m or more.

The new Galileo system will offer five service levels (see below) and bring a step-change in performance. Since the first GPS satellite was launched in the late 1970s, sat-nav technology has evolved enormously.

Galileo should offer greater accuracy - down to a metre and less; greater penetration - in urban centres, inside buildings, and under trees; and a faster fix.

The Galileo system will also come with an "integrity" component - it will be able to tell users if there are major errors that could compromise performance.

Users will also benefit enormously from the agreement between Europe and the US to make their sat-nav systems compatible and "interoperable". That is, future receivers will be able to get a fix using satellites from either constellation.

And when the US introduces the next generation of GPS, users will see a further jump in performance.

HOW SATELLITE NAVIGATION WORKS Satellite navigation systems determine a position by measuring the distances to at least three known locations - the Galileo satellites The distance to o­ne satellite defines a sphere of possible solutions; the distance to three defines a single, common area The accuracy of the distance measurements determines how small the common area is and thus the accuracy of the final location In practice, a receiver captures atomic-clock time signals sent from the satellites and converts them into the respective distances Time measurement is improved by including the signal from a fourth satellite. 'Galileo time' is monitored from the ground

What will Galileo be used for?

The central component of sat-nav is precise timing. The atomic clocks flown o­n the spacecraft keep near-perfect time, equivalent to the theoretical loss of o­ne second over several thousand years.

This precision timing already plays a fundamental but often neglected role not just in navigation, but also in electricity distribution, the functioning of email and the internet, and in the security of financial transactions.

THE SAT-NAV FUTURE Navigation for navigation's sake will not drive applications Uptake pushed forward by services that add value to data Huge potential for internet-linked services run off mobiles E.g. finding a restaurant, and directing you to nearest ATM Multimedia delivered to tourists' mobiles as they walk around 'Guardian angel' services will locate separated children Possibilities are endless; mobile firms already brainstorming Database and billing companies planning for large markets

The better penetration, accuracy and guarantees of service should also give many more entrepreneurs the confidence to build business plans around sat-nav.

With sat-nav capability increasingly incorporated into mobile devices, there is likely to be an explosion in new applications. Many of these will be quite novel and unexpected uses for sat-nav.

Nonetheless, the transport sector will obviously be a big beneficiary. Industry will derive major efficiency gains through better management of supply chains and haulage fleets.

Galileo will deliver the tools national governments need to introduce wide-scale road charging.

Galileo will also underpin Europe's new air-traffic control system. The single European sky initiative will overhaul current technologies used to keep planes at safe separations, and allow pilots to fly their own routes and altitudes.

Is Galileo worth the cost?

Europe's member states have had reservations about the cost from the outset - and, in particular, the uncertainties that exist about what the precise end cost will be.

This prompted o­ne sceptic to dub Galileo the "common agricultural policy of the sky".

There is also debate about the true scale of the revenue opportunities available. Who will want to pay for Galileo-enhanced services and how much will they be prepared to pay?

GPS was built at considerable cost by the US taxpayer but the returns for the American economy mean that investment has been repaid many times over.

All of Europe's big aerospace companies have been attracted to the Galileo project because they believe similar, if not better, returns can be achieved with an improved system.

Analyst forecasts talk of more than 100,000 new jobs being created in Europe, with eventually billions of sat-nav users worldwide generating revenues that are in the order of tens of billions of euros each year.

Is Galileo a "Big Brother" or "spy in the sky?"

Galileo, like GPS, is a passive system; it cannot of itself track individuals. Just because someone carries an active receiver does not mean their every move can be followed.

This o­nly becomes possible o­nce positional information is forwarded to a third party.

Some individuals will choose to do this; o­ne can imagine a mobile phone service that alerts friends when you are in their area.

Companies will "tag" high-value deliveries that report their position so that customers have a better idea of when their goods will arrive.

And governments will, in certain circumstances, insist this information is forwarded to collection centres. A good example would be road pricing, where a vehicle's movements built-up from sat-nav data are passed to roadside beacons or reported over cellular phone networks.

THE FIVE GALILEO SERVICES
NAVIGATION	Open Access	This will be 'free to air' and for use by the mass market; Simple timing and positioning down to 1m
	Commercial	Encrypted; High accuracy at the cm scale; Guaranteed service for which service providers will charge fees
	Safety of life	Open service; For applications where guaranteed accuracy is essential; Integrity messages warn of errors
	Public regulated	Encrypted; Continuous availability even in time of crisis; Government agencies will be main users
SAR	Search and Rescue	System will pick up distress beacon locations; Feasible to send feedback, confirming help is o­n its way