Successful launch readies Galileo satellites for test
Positioning satellite constellation takes shape
The European Space Agency’s Galileo satellite positioning system is soon to enter its “service validation phase”, following the successful launch of the third and fourth satellites in the system.
The two satellites were hoisted to their orbit at around 22,300 km by a Soyuz ST-B launcher operated by Arianspace.
With four satellites in place, Galileo will now be able to begin testing the performance of the positioning system. If the system passes the validation tests, the ESA will go ahead with the launch of the rest of its planned constellation of 30 satellites.
If all goes as planned, Europeans will get first access to the service by the end of 2014 when 18 satellites are in place.
Once initial checks are complete, the satellites will be passed over to the Galileo control teams based in Germany (Oberpfaffenhofen) and Italy (Fucino) to be commissioned.
Galileo is designed to offer one-meter accuracy, compared to the three-to-eight meter accuracy of the US GPS. That accuracy is based on hydrogen-maser atomic clocks.
The 700-kg satellites were built by a consortium of Astrium and Thales Alenia Space (TAS). TAS developed the satellite’s chassis – including on-board propulsion and solar power systems – while Astrium handled the system integration of the payload components.
Future Galileo satellites are being built by Germany’s OHB-System in Bremen, which will be responsible for the platforms, and Surrey Satellite Technology, which is handling the payloads. ®
The standard, free to use signal is accurate to 1 metre, but there are four additional services that the system transmits.
There's an encrypted commercial navigation signal accurate to the centimetre. That's good enough for precision approaches to airfields that lack glideslope equipment (which is expensive to install and maintain).
There's an unencrypted safety of life service that includes error detection and warning.
There's an encrypted public regulated service that is resistant to jamming and is guaranteed to remain active if the other services are disabled.
There's also a Search & Rescue service that can pick up distress beacons and can send messages back to the beacon confirming reception and that rescuers are on the way.
The big political bonus is that the system is outside of the control of the US military so the EU can make its own decision if and when to disable the network.
Why? Glonass and Navstar are military systems
They can be switched off - and have been.
When the first gulf war started in 1991, a friend of mine ferrying a Beechcraft Baron across the pacific suddenly found himself without his most accurate navigational tool. There's an awful lot of ocean out there and when you can only fly at 10,000 feet, islands are easy to miss.
He had backups (dead reckoning, etc) but it's still not a good feeling when out of radio/loran range of everything.
GPS is more accurate over the US
Really, I've never seen that mentioned in any of the literature, the satellite orbits aren't biased that way and it wouldn't be the most useful thing for the US military. Do you have a link to something detailing how that works?
Incidentally the US GPS system is called Navstar.