A new spacecraft to broadcast music, news and variety programming for Sirius XM Radio is scheduled to blast off Thursday from the Baikonur Cosmodrome in Kazakhstan.

The Sirius XM 5 satellite will join a fleet of spacecraft already beaming radio signals to receivers in cars, trucks, boats, aircraft, homes and mobile devices of more than 19.8 million subscribers.

A Russian Proton rocket and Breeze M upper stage will deploy the 13,192-pound spacecraft on a high-flying trajectory taking Sirius XM 5 more than 22,200 miles from Earth.

The rocket rolled to pad 24 at the Baikonur Cosmodrome on Monday morning.

The Proton rocket rolled to the launch pad Monday morning. Credit: Roscosmos
 
Liftoff is set for 1853:21 GMT (2:53:21 p.m. EDT) Thursday.

Burning toxic storable propellants, the 191-foot-tall rocket will accelerate east from Baikonur, dropping its first stage two minutes after launch and its second stage at T+plus 5 minutes, 27 seconds. The Proton's payload shroud will split open and jettison 20 seconds later, exposing Sirius XM 5 once the booster reaches the upper atmosphere.

After releasing the rocket's third stage at T+plus 9 minutes, 42 seconds, the Breeze M upper stage will coast for two minutes and ignite its main engine at T+plus 11 minutes, 46 seconds. It will fire four-and-a-half minutes to place itself and the payload in a circular parking orbit 107 miles above the planet.

Another four Breeze M burns will raise its altitude and reduce its orbital inclination. The upper stage is scheduled to release the satellite at 0405 GMT (12:05 a.m. EDT) Friday.

The launch vehicle is targeting an orbit stretching from a low point of 2,632 miles to a peak altitude of more than 22,200 miles. The planned inclination at spacecraft separation is 22.84 degrees, according to Khrunichev, the Proton rocket's prime contractor.

Sirius XM 5 is prepared for launch at the Baikonur Cosmodrome. Credit: Khrunichev

Thursday's flight will be the 360th Proton rocket launched since its first mission in 1965. It will be the ninth Proton launch of 2010 and the sixth this year under the auspices of International Launch Services, the Russian-owned, U.S.-based firm responsible for commercial Proton missions.

Sirius XM 5 will fire its on-board orbit-raising engine to reach a circular orbit 22,000 miles high in next few weeks. The satellite will eventually slide into position at 85.2 degrees west longitude over the equator to enable its powerful transmitters to reach customers across North America.

Two 29.5-foot-diameter unfurlable mesh antennas will broadcast Sirius XM Radio's 135 audio channels.

Built by Space Systems/Loral, the satellite is designed to last for at least 15 years in space.

The satellite will be an in-orbit spare for Sirius XM Radio's other spacecraft. Sirius XM 5 will be the ninth satellite the company has launched since 2000, including delivery missions for Sirius Satellite Radio and XM Satellite Radio before the firms merged in 2008.

Four of those satellites were launched by ILS Proton rockets.