The Sirius FM-6 satellite, also known as Radiosat 6, is a Commercial Communications Satellite operated by Sirius XM Satellite Radio and was built by Space Systems/Loral. It is based on SS/L’s flight proven LS-1300 satellite bus that can host powerful communication payloads. The satellite has a dry mass of 2,975 Kilograms and a launch mass of 6,018 Kilograms.
The spacecraft is equipped with two six-panel power-generating solar arrays, onboard batteries for power storage and avionics for power distribution and spacecraft control. The platform is three axis stabilized and uses state of the art navigation systems. Sirius FM-6 uses a combination of liquid-fueled and electric propulsion systems.
The main propulsion system that is used for orbit raising and adjustments uses a single R-4D engine. The R-4D engine is a Monomethylhydrazine/Nitrogen Tetroxide Engine that provides 490 Newtons of thrust. The engine is 0.55 meters long and 0.28 meters in diameter with an unfueled mass of 3.63 kilograms. The engine provides a specific impulse of 312s, has a thrust to weight ratio of 13.7 and operates at a chamber pressure of 6.9 bar. The original RD-4 was developed as an attitude control thruster for the Apollo Service and Lunar Lander modules. RD-4 engines were built by Kasier Marquardt.
The electrical propulsion system features SPT-100 plasma thrusters that are used for orbit maintenance, stationkeeping in Geostationary Orbit and attitude control maneuvers. The Stationary Plasma Thrusters provide 83 Millinewtons of thrust each.
The spacecraft is equipped with a single powerful X/S-Band transponder that provides digital audio services.
Sirius FM-6 will operate in Geostationary Orbit at 115 degrees west for at least 15 years to cover North America. The satellite will join the Sirius satellite fleet to provide commercial-free music, sports coverage, news, talk, entertainment, traffic and weather to more than 25 million subscribers of Sirius XM. The satellite fleet also provides traffic and data services to vehicles with navigational systems as well as mobile devices and home receivers.