Thought this was interesting. European's own version of GPS satellites transit a signal that, unlike GPS, is only available to those who pay a license. Well a group at Cornell cracked the PRNG and can now receive telemetry.
Cracking the Secret Codes of Europe's Galileo Satellite
This prompted a few questions from people when I mentioned this:
Q: Why does Europe charge for access to their satellites when GPS is freely available?
A: GPS was built by the U.S. military with taxpayer dollars. The European equivalent was funded by commercial entities who want to recover their investment.
Q: Why did Europe deploy their own satellites? Why didn't they just use the existing GPS?
A: The GPS system is owned by the U.S. government. It was originally designed with Selective Availability. This is an intentional distortion in the signal that makes commercial receives inaccurate while U.S. military receivers can still get an accurate signal. While Selective Availability was turned off in 2000, the Europeans are concerned about the control that the U.S. government could exercise over them if they wanted to (for example, in response to a political disagreement). By Europe having its own equivalent to GPS the European countries would not be at the mercy of the U.S. government.
Wikipedia has a pretty good article on the Galileo satellite network.
