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Last Updated: Friday, 26 January 2007, 13:07 GMT
Recycled satellite radio planned
Car undserneath a satellite
The prototype system could take advantage of out-of-date satellites
An advanced in-car multimedia system that could use recycled television satellites coming to the end of their working lives has been unveiled.

The prototype system, developed by the European Space Agency (Esa), offers high-quality radio, video and data.

The satellite radio component also overcomes problems such as loss of signal when driving through tunnels.

If commercialised, the system would offer the first in-car satellite radio service available to Europeans.

The prototype was demonstrated at the Noordwjk Space Expo in the Netherlands.

Old technology

Satellite radio services already exist in countries like the US where 13 million people subscribe to the two main broadcasters, XM-radio and Sirius.

The digital signal offers near CD-quality sound and can contain up to 100 different radio channels as well as information such as the song title or the name of the artist.

These satellites have done their duty for so many years and generated revenues, this extra life is a bonus
Rolv Midthassel, Esa
In the US, listeners use satellite receivers built into cars to pick up radio signals from a network of specially designed orbiting platforms and ground-based repeater stations, used to ensure signal strength particularly in built-up areas.

To cut down on cost, the experimental system proposed by Esa does away with the need for a new satellite network.

Instead, the Esa researchers propose that the system could piggy-back on a network of satellites already used to broadcast satellite TV signals.

These typically only have a life of 10-15 years because after that time they run out of fuel and start to drift from their position. This means they are of no use to television services which require stationary spacecraft for satellite dishes to point at.

"From a technical point of view they are still fine," said Rolv Midthassel, a communications engineer at Esa.

Memory device

However, the proposed Esa system could still make use of them by tracking their position. A small mobile antenna built into the body work of the car would mean that the system was always pointing in the right direction to pick up a signal.

Car with satellie dish on roof
The researchers are hoping to shrink the size of the antenna
"As these satellites have done their duty for so many years and generated revenues, this extra life is a bonus and you can get them quite cheap," said Mr Midthassel.

The system also does away with the ground repeater station used in the US.

Instead, signals are sent as files and stored on a memory device, known as a cache.

These files are then reassembled into complete programmes as and when they are needed. Consequently, even when satellites are out of view of the car, the radio programme is uninterrupted.

This file-based approach also allows the car to store and display other information such as short videos for backseat entertainment or travel information. It could also allow updates to the digital maps for navigation devices.

The experimental system has been in development for three years at Esa with a range of technology companies and car manufacturers.

"The next step would be to make a product out of this but industry would have to take the initiative on this," said Mr Midthassel.

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