Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Second-hand satellites may gain new voice

05.02.2003


ESA engineers are proposing a technique to enable a digital satellite radio service for European drivers - without the need to launch a single new satellite into orbit.



Commercial digital satellite radio is already a reality in the United States, using a costly set of dedicated satellites. The rival American services allow subscribing drivers to choose between numerous near-CD quality radio channels without tune-out or static.
Two parallel ESA studies have examined a lower-cost method of providing in-car Europe-wide satellite radio, along with supplemental text, pictures and video data. ND Satcom (prime contractor), DLR, IMST and SES Astra conducted one of the studies while Alcatel Space (prime contractor), Frauenhofer Gesellschaft, Skygate and SES Astra performed the other.

"This service would include music and voice data," said ESA engineer Rolv Midthassel from the Technology Projects Division of the Telecommunication Department. "Plus additional data could be displayed on-screen such as information on songs, traffic and weather forecasts, and other services dedicated to car drivers."



It promises to be much cheaper to set up than US satellite radio, because it requires no new expensive satellite launches. Instead the proposal is to reuse existing TV satellites nearing the end of their operating life.

Once in position, 35,000 km away in space, TV satellites will remain in orbit forever, but their useful life amounts to 15 years or less. Onboard thrusters must keep each satellite pointed precisely in geostationary orbit so they stay lined up with fixed-position Earth-based receivers.

However once the thrusters’ propellant runs out the satellites drift out of correct orbit, and are left useless for TV broadcast applications. But further life can be squeezed from a low-propellant TV satellite switched over to mobile digital radio broadcasting where precision position control is less important.

Most thruster propellant is expended correcting satellite attitude in the north-south direction. But if station-keeping is limited to the east-west axis then satellite lifetime could be extended by some five years.

The satellite’s position would oscillate across the sky by a few degrees. But vehicle-mounted digital radio antennas would keep track of the satellite as it moves, just as they would maintain contact with it as the car bearing the antenna moves across the landscape.

"Satellite reception is frequently shadowed by trees, rain, or cloud or blocked altogether by mountains, tunnels or tall buildings," explained Midthassel. "In urban areas the studies indicate that the signal is blocked an average 30 per cent of the time, maybe for several minutes at a time."

These reception gaps make real-time broadcasting impracticable. Instead the service would operate on a cache system – data files are stored by the receiver for later playback.

"Sophisticated interleaving, data coding and large signal margins should enable the useful data to be reconstructed even when some of the signal has disappeared," said Midthassel.

Interleaving is a method whereby the burst of erroneous data arising from blockages and shadowing will be spread out in time and mixed with correctly received data bits. And coding data will then enable the receiver to interpret it in the correct context.

Studies indicate a useful data rate of a million bits per second per satellite transponder. With each satellite having several transponders, this makes the system performance comparable or even superior to US services.

"The receiver cache will contain files like songs, news flashes, and discussion programmes," Midthassel added. "Based on a pre-set user profile an individually-tailored radio programme could be constructed out of available files."

"Alternatively the user could choose which service he wants from the cache – so you could play the latest news then and there instead in a half-hour’s time. Exiting the car to fill up with petrol, you could halt the news then restart it once you’re back."

Test reception measurements have been carried out by both teams monitoring signals from SES Astra satellites.

The next steps come this year, with plans to design a low-cost fully electronically steerable antenna as well as develop a suitable gateway transmitter and user receiver which shall serve as a system demonstrator for extended field testing.

Dominique Detain | alfa
Further information:
http://www.esa.int/export/esaSA/SEM67L1A6BD_telecom_0.html

More articles from Communications Media:

nachricht The plastic brain: Better connectivity of brain regions with training
02.07.2018 | Leibniz-Institut für Wissensmedien

nachricht Arguments, Emotions, and News distribution in social media - Leibniz-WissenschaftsCampus Tübingen
04.05.2018 | Leibniz-Institut für Wissensmedien

All articles from Communications Media >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>