Sirius Satellite Radio Inc. [SIRI] said in-orbit testing of its first radio broadcasting satellite, Sirius 1, was completed successfully July 31, with all systems performing to specifications.

Sirius is one of the two U.S. companies building and launching satellites for digital radio service. The company said Sirius 2, its second satellite, has arrived at the Baikonur Cosmodrome in Kazakhstan for its launch aboard a Proton rocket, which is scheduled between Sept. 5-15.

Sirius 3 is scheduled for launch in October, also aboard a Proton, and the company plans to begin broadcasting its 100-channel service at the end of the year. The arrival of a spare satellite, Sirius 4, previously scheduled for delivery to ground storage in December, has been delayed, company officials said, and a new delivery date is expected to be set within a few weeks.