By Jonathan Amos
BBC News science reporter
A new era in satellite navigation has begun with the launch of Giove-A.
The 600kg spacecraft was lifted into orbit on a Soyuz rocket from Baikonur, Kazakhstan, at 1119 (0519GMT).
Giove-A will demonstrate key technologies needed for Galileo, the 3.4bn-euro (£2.3bn; $4bn) sat-nav system Europe hopes to deploy by 2010.
The new network will give EU states guaranteed access to a space-borne precise timing and location service independent of the United States.
The perfect launch was a moment of celebration for the small British company, Surrey Satellite Technology Ltd (SSTL), which had been given the prestigious task of building the demonstrator.
SSTL staff had gathered at their Guildford base to watch the lift-off on a TV link from Baikonur.
The company put the spacecraft together in less than three years, a remarkably short timeframe for what is essentially an experimental platform.
Mission will trial technologies for future Galileo satellites
Will transmit sat-nav signals to claim frequencies for Galileo
Has instruments to assess radiation in 23,222km orbit
(1) Power demand of 660W through 4.54m-long arrays
(2) Butane propulsion system; tanks hold up to 50kg of fuel
(3) Payload has rubidium clocks and signal-generation units
(4) Antenna system to transmit signals for ground testing
"Three years ago I did a sketch of what I thought we could do. To go from that sketch to what we have now is amazing," recalled John Paffett, projects director with SSTL.
"It's not over yet - there's a lot of hard work to go ahead - but it's definitely a monumental occasion," he told the BBC News website.
Professor Sir Martin Sweeting, the CEO of SSTL, added: "This is going to be Europe's largest space project. As a relatively small company - we're an SME of 200 people, specialising in small and rapid-response spacecraft - to take the vanguard of such a large programme is quite an experience."
Giove-A will check out the in-orbit performance of two atomic clocks - critical to any sat-nav system - and a number of other components that will be incorporated into the 30 satellites of the fully fledged Galileo constellation.
These spacecraft - four of which have already been ordered - are expected all to be in orbit by the end of 2010.
Giove-A also has the important job of securing the radio frequencies allocated to Galileo within the International Telecommunications Union.
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
To do this, a sat-nav signal of the correct structure must be received on Earth by June 2006. The SSTL team believes it can complete this task within the first couple of weeks of flight.
Galileo is a joint venture between the European Union and the European Space Agency (Esa).
Once fully deployed, the new system should revolutionise the way we use precise timing and location signals delivered from space.
"We are aiming to provide one-metre, worldwide accuracy through Galileo's 'open' service - this is not possible today without regional or local augmentation," said Esa's Galileo project manager, Javier Benedicto.
"With the use of three signals, we will have access to centimetre accuracies, and with these you will see many more services than you have today; and European industry is working to develop those applications."
In few years' time, a small Galileo chip will be integrated in mobile phones, giving users the ability to pinpoint restaurants, hotels, movie theatres, hospitals or car parks.
Galileo will deliver the tools national governments need to introduce wide-scale road charging.
The network 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.
SSTL hopes a successful mission for Giove-A will bring more orders for sat-nav and other spacecraft.
"This is very good for our development," explained Max Meerman, a principal engineer with the company.
"It's the biggest satellite we've done so far, it's got big deployable tracking-arrays that we haven't done before, and it cost 28m euros (£19m; $33m)."
Satellite navigation systems determine a position by measuring the distances to a number of known locations - the Galileo satellites
The distance to one satellite defines a sphere of possible solutions; the distances to four satellites 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
The whole system is monitored from the ground to ensure satellite clocks do not drift and give out misleading timings