Wednesday, May 20, 2009

Do you know where you are ?

Well of course you do! You open your phone and use the GPS receiver to tell you , complete with map.
But what if it doesn't, one day ?
It'll never happen, you say. It's a government project and things like that don't fail. . It's too big and too important to fail you say, as the words "Lehman Bros." creeps insidiously into your brain. A small shiver crosses your skin as you think of being out alone in the desert , broken down, phoning for help, and not knowing the answer when the operator asks you where you are.
Why this beginning to my blog today, you ask. Am I honing my art for writing the first in a series of blockbuster B-movies ? No. What caught my eye as I was at the Haddonfield Stitch 'n' Bitch this evening was a headline on the TV about a problem with the GPS system. Apparently the Air Force has been having such fun chasing bandits in Irak and Afghanistan that it hasn't managed to keep up with repairs on the small constellation of satelites that provide the signals for the GPS system.
The system is made up of a constellation of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. Periodically satellites fail and are replaced - this is normal.
However, right now the US Air Force, which has responsibility for maintaining the system (which is also used by the US military, of course) has apparently been having problems in designing and lofting replacement satellites. The satellites have multiple redundant backup systems, so failure isn't very frequent, but apparently many are down to and using their last set of spares for several functions, so just one failure might take a satellite out of the system.
One satellite won't kill off the entire system, but to get decent accuracy your GPS device needs to have four above the horizon to see.
Next year is predicted to be the year that satellites start dropping off without being replaced, says a government report out in the last few days. If you want to be really bored, it's here. Basically, it says that the Air Force hasn't been replacing satellites fast enough, hasn't coordinated development of new versions with purchasing and launching schedules, and hasn't been successful in building ground control facilities to control the newer satellites. To put it even more bluntly: the Air Force was tasked with maintaining and developing the system, and hasn't done so.
Is there an alternative, one asks (thinking again of the cold Arizona desert at night). Well yes, there kind-of is, but not yet. It's about three years late and is now due to enter service in 2013. It's called Galileo and is a constellation of 30 satellites due to be lifted by Ariane over the next few years It is supposed to have better resolution than the civilian GPS, but who knows when you'll be able to use it in the USA, as the phone makers probably won't make bi-system phones.
Finally there's another European program, Egnos, that's supposed to improve the accuracy of the GPS system. However, that may not fly if the GPS dies out!
So, if you want to find out where you are next year, keep up those donations to the Air Force
The picture at the top is from an AP site, and they got it from NASA. It's t
he Sombrero galaxy as seen by the Hubble Space Telescope. Rather cool.


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