If all goes well with the Russian rocket's climb into space, the 8,377-pound (3,800 kilogram) spacecraft built by Loral Space and Communications will be delivered into its proper orbit some two hours and 25 minutes after launch.

The Sirius 2 satellite will then wait in space with Sirius 1 - launched into orbit on June 30 - until Sirius 3 is sent up on a Proton in October. Then when all three satellites are declared operational Sirius Radio Satellite is expected to begin offering programming, perhaps by the end of this year.

A fourth satellite - intended to remain on the ground as a spare until eventually needed - recently was damaged, sending Sirius Radio Satellite's stock price into freefall until calmer heads prevailed and the price began to recover. Such is the intense interest in this innovative use of space technology.

The idea: equip cars and trucks with a radio receiver that can tune in the Sirius satellites' programming, allowing drivers to stay tuned to a station with CD quality sound no matter where they drive in the United States.

Another attraction for many potential users will be the fact that half of the 100 channels Sirius intends to offer will be free of advertising.

For the price of a new radio - about $200 - and a monthly service fee of $9.95, listeners will be able to hear 50 channels of non-stop music to suit anybody's taste, as well as 50 channels of more conventional news, sports and entertainment from sources such as CNBC, National Public Radio and the BBC.