Satellite Radio - Sirius’ spacecraft Radiosat 1 through Radiosat 4 were manufactured by Space Systems/Loral. The first three of the series were orbited in 2000 by Proton-K Block-DM3 launch vehicles, with the final three-satellite constellation completed on November 30, 2000. Radiosat 4 is a ground spare, in storage at SS/Loral’s facility in Palo Alto, California, ready to be launched if any of the three active satellites encounter transmission problems. The series of satellites from which they come, the SS/Loral LS-1300, is known to have problems with their solar array cells — a similar issue affects the Boeing satellites belonging to competitor XM Radio.