European 'sat nav' joins the space race
22 December 2005
Satellite navigation is big business, but dashboard 'sat nav' in today's cars and boats relies on signals beamed from US or Russian military satellites. Now Europe's first global-positioning satellite is ready for liftoff.
Antenna goes into orbit for a closer look...
Image: ESA
Thirty satellites forming the Galileo network will be orbiting Earth by 2010.
Video: ESA
The satellite's launch is the first bold step towards Europe's own network of global-positioning satellites, collectively known as Galileo. |
Why does Europe need its own sat nav?
Today's satellites weren't designed to help motorists get from A to B without arguing over directions, but for military missions. There's no guarantee that the signals will be available to civilians all the time.
Today's satellites weren't designed to help motorists get from A to B without arguing over directions, but for military missions. There's no guarantee that the signals will be available to civilians all the time.
Some of the technology on board is twenty years old, and if you're lost in certain parts of northern Europe, you may not even be able to pick the signal up. Galileo's scientists are sure the new network will be an improvement.
Image: ESA
'With Galileo, you'll be sure that you can trust the signal. It will give a guarantee of service that the US or Russian satellites don't provide. And Galileo will be more accurate.'
Dominique Detain, Galileo expert, European Space Agency
Dominique Detain, Galileo expert, European Space Agency
Dominique Detain, Galileo expert, European Space Agency, stands in front of the rocket that will launch the first Galileo satellite into space.
Image: Dominique Detain
How does satellite navigation work?
Your sat-nav receiver works out exactly where you are by picking up radio signals sent out by a network of satellites orbiting the Earth. Each satellite uses a highly accurate atomic clock to label each signal with the exact time the message was sent.
Your sat-nav receiver works out exactly where you are by picking up radio signals sent out by a network of satellites orbiting the Earth. Each satellite uses a highly accurate atomic clock to label each signal with the exact time the message was sent.
A quick sum by your receiver tells it how long each signal took to arrive from the satellite. Now it can calculate how far away the satellite is.
Image: ESA
Your sat-nav receiver needs signals from four satellites to work out your location.
Video: ESA
Finally, once it's repeated this to work out how far away four different satellites are, it can calculate exactly where you are. By using the Galileo satellite network, it'll be able to get this right to the nearest metre. |
The Galileo satellite and the rocket that will blast it into orbit are standing by at the Baikonur Cosmodrome in Kazakhstan, with liftoff set for 28 December.
The part of the rocket that protects the satellite during launch will be ejected once the rocket leaves the Earth's atmosphere.
Image: ESA
It's the first of two test satellites and scientists have packed it full of new technology that they need to check before they start launching the main Galileo satellites.
'We have technology on board that will measure how much radiation the main Galileo satellites will be exposed to in space. The main satellites will carry more equipment, transmit more signals and will last longer than the test satellites - 15 years instead of three years.'
Andrew Bradford, Surrey Satellite Technology Ltd
Andrew Bradford, Surrey Satellite Technology Ltd
The test satellite is the first of two that scientists are launching.
Image: SSTL
A second test satellite will be launched in 2006, and if all goes well scientists will start sending up the 30 main satellites. The whole network should be up and running by 2010.
The Galileo satellites will orbit the planet around 24,000 km above our heads. That's slightly higher than the US satellites.
Image: ESA
'A low Earth orbit would cost less and would expose the satellites to less radiation, but literally hundreds of satellites would be needed to achieve a global coverage for navigation. The medium Earth orbit of 24,000 km is a sensible compromise, although electronics must be able to tolerate the high levels of radiation.'
Andrew Bradford
Andrew Bradford
With Galileo in place, sat nav will be accurate enough to keep your car journeys on the straight and narrow. And boat owners will benefit whether they're navigating the Atlantic or cruising in the Caribbean.
'Galileo will work for the whole world, not just Europe.'
Dominique Detain
Dominique Detain