In the latest coup for the fledgling satellite radio industry, Sirius Satellite Radio Inc. (SIRI) Thursday named former Viacom Inc. (VIA.B) President Mel Karmazin (search) as its chief executive officer.

New York-based Sirius said current CEO Joseph Clayton would remain chairman.

Karmazin takes the helm of a company already buoyed by its recent deal to bring aboard one of Karmazin's biggest former talents at Viacom, radio host Howard Stern (search), known for his raunchy language.

Shares of Sirius rose over 20 percent in after-hours trade in response to Karmazin's appointment, hitting $5.75 from a Nasdaq close of $4.72.

Stern is due to quit Viacom Inc.'s Infinity Broadcasting (search) in January 2006, though speculation has persisted for weeks that his Viacom contract may be bought out sooner.

Karmazin, who was Stern's longtime benefactor and supporter at Viacom, left his post as president and chief operating officer of Viacom in June in a management shake-up of the media conglomerate.