US negotiators in Brussels expect to reach agreement with the European Union within a week regarding cooperative use of the American Global Positioning System (GPS) and the EU's proposed Galileo sat-nav constellations. Reuters reports that the American plan is for GPS and Galileo satellites to employ the same frequencies, …
"the American plan is for GPS and Galileo satellites to employ the same frequencies"
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Does that make sense to anybody? Surely, they need to be using DIFFERENT frequencies within the same overall band, in order to remain distinguishable but still be within the capability of a simple receiving device?
If they tried to work on the SAME frequencies, then the result would surely be that neither of them could work reliably, in exactly the same way as it is not sensible for two radio stations in the same area to broadcast on the same frequency.
<<hardcore permanent bureaucracy at Brussels>> As opposed to what exactly? The soft-centred sweeties of Whitehall? The soft-porn playthings of Washington? Please, please, tell me what on earth those words could possibly mean!
I think the point of the Galileo system was simply to offer the same service, only not subject to the same uni-lateral self-serving control that the US seems to exhibit in every other area of politics. They can't even follow laws that they helped set up (see Antigua/Remote Gambling/GAT). It therefore seems reasonable that noone would want to base future advancements like self-navigating vehicles on something that some wingnut in the US administration can just switch off.
As for the frequencies, right now there's multiple satellites all operating on the same frequencies which is how you triangulate your position. I presume that the proposal is to have the galileo system simply add to the number of satellites you could access via the same kit. If at some point someone decides to restrict the GPS system, you'd still have 30 Galileo sats to triangulate from instead of the 60 GPS + Galileos.
Obviously the devil is in the detail, but from the sound of it sounds like a pretty reasonable idea to me.
The right direction
Even more reasonable would be to use the same protocol, so that existing receivers work. Europe ends up with a GPS constellation that the Pentagon can't switch off, the US gets someone else to pay for half of the maintenance of the current system, and consumers get better service.
The only part of this plan that is missing is the ability to charge for the Galileo signals, but that was a moronic idea all along and if the system is going to be financed out of the European public purse (as now seems inevitable) then it had better be free at the point of delivery.
RE: Freqing out
Same frequency BANDS. Look up communication theory on 'spread spectrum' communications - your CDMA mobile phone works perfectly fine sharing the same band as hundreds of others with one basestation.
I've seen this on several sites, and I can't for the life of me work out what the story is here. I'm working on a Galileo based project that has been going since early 2006 which the *fundamental* idea was to use GPS + Galileo signals - why would you need an agreement from either party? They both have open signals which dual use receivers were always going to be designed to take advantage of.
During Desert Storm, the US turned off the civilian degraded mode because there weren't enough MIL Spec GPS units. And it's never been turned on again. If Galileo uses different clocks, they'll need different freqs. But if they have the same clocks, it all becomes one big system. Of course, I'm sure the Pentagon would LOVE to share the clocks with a purely civilian system.
Hasn't the British MoD publicly tested a GPS jammer? And would anyone like to speculate on the chances that the DoD has already done so?
Need the money first
Debate seems a bit superfluous until the consortium can agree on funding. With just one bird aloft and the typical consortium-type bickering over money, when can we expect the other 29 satellites to reach space? Don’t worry about resetting the receiver on your Tom Tom just yet.
How do you turn off the service to the war zone when the civilian zone is 100 miles away?
Turning off service to "the war zone" sounds easy, when you are in North America and the war zone is on another continenent.
But what is the war zone is only a few hundred miles away?
The signal comes from orbiting satellites. How do you turn off the signal to, say, Bosnia, and not affect Greece or Italy?
Pre-emptive party crashing
We have reports of the PRC flaunting their abilities to take out satellites. In the circumstances, it would be most convenient for the USA to freeload on Galileo if at some future time the PRC were to play the party pooper at the USA's space party by popping all their satellites. In a confrontation with the USA, the PRC would not necessarily want a face-off with the EU at the same time. But given that the Israelis have been already been allowed to climb onto Galileo with a space-based *satellite tracking system*, it would seem churlish to claim that there isn't room for one more on the old whore. C'mon boys, come and get it.
yes, same frequency
gps sats all transmit on the same frequency, using spread spectrum techniques, and all use a different spreading code... the receiver uses multiple correlators (often loosely referred to as channels) to be able to receive the different satellites simultaneously. the data rate from the sats is actually quite slow, hence it can take a long time to get a fix when the receiver's not been on for quite a long time in order for it to acquire the full ephemeris data (which is the satellite's deviation from expected position).
there are actually TWO gps frequencies, the full mil spec receivers use both as it helps counter atmospheric disturbancies and jamming.
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