XM threw the switch on Friday and began broadcasting through their new XM-4 satellite, nicknamed "Blues."

The combination with the XM-3 satellite (nicknamed "Rhythm") back in March of 2005, replaces the ailing "Rock" and "Roll" satellites that were launched in 2001. Rock and Roll will remain in-orbit as backups.

John Dealy, XM's Senior Advisor who leads the XM Satellite Systems Team said, "both satellites are healthy and expected to deliver excellent service beyond their contract requirement of 15 years, providing the richest entertainment content to XM subscribers for the long-term."

No word on whether any additional functionality is available with these new birds, but at the very least XM doesn't have to worry about them for the next 15 or so years. 

[Press Release]