The UK Telegraph has an interesting article on GPS 2 covering some of the technical, scientific, historic and political background to the system.
On a side note, I'm happy to observe that statements like this aren't as common as they used to be:
Slightly worryingly, when I was invited to watch a “contact” in another control room earlier in the day, the software crashed and a familiar, blue Microsoft Windows screen appeared on the wall
- yes I made this up. My entry for Internet memedom!
- don't worry, it's still safe to use your cellphone after visiting this site