colejl

Perhaps some GPS satellites have gone offline? Read here GPS
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Cannot get to that site from work, but....GPS constellation is healthy. We are moving a few around (drifting), but have plenty to satisfy all civil and military applications. It takes 24 satellites for a full constellation and we have 28 up and running. The first Modernized (IIR[M]) was launched a little more than a week ago and will undergo a 120 day shakedown. Next launch with the 2nd new modernized IIR(M) version is slated for NET 1 FEB '06.
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Here's the text from the link:

Firms that rely on the US Global Positioning System (GPS) should ensure that they have a fallback plan, as one of the UK's top navigation experts has warned that the system may prove unreliable.

Speaking at a Cambridge University conference in September, Norman Bonnor, a retired RAF Air Commodore and president of the Royal Institute of Navigation, said the GPS signal is more fragile than many users might suppose. "Too many people don't understand its foibles and vulnerabilities," he added.

GPS is widely used in systems ranging from car navigation to emergency services co-ordination; and for time-keep- ing in utilities, finance and telecoms sectors.

The system relies on a network of satellites, which cannot be repaired once launched and have a limited lifespan. Sixteen of the present 28 satellites were built to last seven and a half years, but are now between eight and 14 years old. Twenty-four satellites are required for full coverage.

Bonnor said launches of new satellites are "only just keeping up" with current losses of around two satellites per year. But the failures could accelerate due to the number of satellites that have used up their redundant hardware. "Many are on their last legs," he explained.

The first of eight modernised satellites, built to last 10 years, was due to launch yesterday after a series of delays. A European alternative to GPS, called Galileo, is not expected to be complete until 2010.

cobradav

Perhaps some GPS satellites have gone offline? Read here GPS
[/quote]

Cannot get to that site from work, but....GPS constellation is healthy. We are moving a few around (drifting), but have plenty to satisfy all civil and military applications. It takes 24 satellites for a full constellation and we have 28 up and running. The first Modernized (IIR[M]) was launched a little more than a week ago and will undergo a 120 day shakedown. Next launch with the 2nd new modernized IIR(M) version is slated for NET 1 FEB '06.
[/quote]
Here's the text from the link:

Firms that rely on the US Global Positioning System (GPS) should ensure that they have a fallback plan, as one of the UK's top navigation experts has warned that the system may prove unreliable.

Speaking at a Cambridge University conference in September, Norman Bonnor, a retired RAF Air Commodore and president of the Royal Institute of Navigation, said the GPS signal is more fragile than many users might suppose. "Too many people don't understand its foibles and vulnerabilities," he added.

GPS is widely used in systems ranging from car navigation to emergency services co-ordination; and for time-keep- ing in utilities, finance and telecoms sectors.

The system relies on a network of satellites, which cannot be repaired once launched and have a limited lifespan. Sixteen of the present 28 satellites were built to last seven and a half years, but are now between eight and 14 years old. Twenty-four satellites are required for full coverage.

Bonnor said launches of new satellites are "only just keeping up" with current losses of around two satellites per year. But the failures could accelerate due to the number of satellites that have used up their redundant hardware. "Many are on their last legs," he explained.

The first of eight modernised satellites, built to last 10 years, was due to launch yesterday after a series of delays. A European alternative to GPS, called Galileo, is not expected to be complete until 2010.
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While technically accurate to say they cannot be repaired once launched, they do have backup and redundant systems as stated in the article. But once on the backup or redundant system they could last many more years. And as also stated several have, indeed, had to use their backup or redundant systems. But these are generally (not always) at or near the end of their designed lifespan. On lifespan, this is a contractual spec the gov puts in the contract with the satellite builder. 95% of all satellites far exceed their design life. Witness the current Mars rovers operating in their 18th month on a 90 DAY mission. Or the Voyagers that went decades beyond their design life. So too, do the GPS operate well beyond their design life. Once the IIR(M) is certified (about another 110 days) we could nearly ripple fire (approximately every 14 days) the next 7 GPS satellites if we had to. Then will be the next generation GPS, IIF, then the GPS III. GPS III is not slated to launch until 2010 or later around the time of the EU system if the EU can get their act sorted out on Galileo. Perhaps this was intended to spark some breakthrough on EU negotiations amongst member nations. Nobody in GPS JPO is in panic mode at this time and they are far more concerned with the warfighting mission than the civil concerns although important too. If fact that is driving several of the upgraded systems capabilities on the new satellites.