Personalised digital radio services could be broadcast from disused TV satellites that are ‘stuck’ in geostationary orbit.
An ESA project aims to recommission the satellites in a bid to extend their lifespan by up to five years. Radio broadcasts relayed via orbiting satellites are already operating in the US where listeners can subscribe to numerous digital-quality channels.
TV satellites usually have a lifespan of 15 years. They eventually run out of fuel to power their orientation thrusters which are needed to maintain a precise position necessary for broadcasting. But they do not need to be as carefully aligned to allow radio transmissions.
ESA plans to demonstrate the new radio application in 2005. Signal strength testing has already confirmed that such a system would work and a low-cost digital radio set for consumers will also be designed later this year.
Rolv Midthassel, an ESA technology projects division engineer, explained the services that could be provided. ‘Songs, news flashes and discussion programmes would be available. Based on a preset user profile an individually tailored radio programme could be constructed. Alternatively the user could choose which service he wants, so you could play the latest news there and then instead of in half an hour’s time.
Drivers who leave the car to fill up with petrol could halt the news and then restart it once back in.’
This radio menu has been made possible because in urban areas the signal can be interrupted by up to several minutes at a time. The solution is to allow the radio sets to effectively download whole programmes in one go and store them for the listener to hear when convenient.
The radio unit will be designed to receive considerable amounts of information, despite the difficulties of maintaining a consistent service.
The ESA team has established that each transmitter on the satellite would be capable of relaying data at a rate of 125Mb/sec.
The satellites orbit at 35,000km above the Earth. At this height and at a speed equal to that of the planet’s rotation they can stay permanently above one point on the Earth’s surface.