XM Satellite Radio is powered by its two orbital vessels, nicknamed Rock and Roll. A third is scheduled to launch in February.
Image: Rock 'n' roll heaven for XM
XM Satellite Radio has two music boxes in the sky, Rock (XM-1, pictured at right) and Roll (XM-2), built by Boeing and in orbit since 2001. Each transmits up to 100 channels of digital radio to subscribers across the continental United States. XM-3 is scheduled to lift off from Earth in February.