Sirius recently filed an application for authority to launch and operate a new non-geostationary orbit satellite (NGSO, FM-6). The satellite will replace TWO existing NGSO satellites (FM-1 and FM-2) that are currently in operation. FM-6 would be placed half way between the where FM-1 and FM-2 operate today. The launch is expected to take place in 2010. Sirius has already been granted authority to launch a geostationary satellite (FM-5). This will significantly alter its existing satellite constellation. It will eventually operate with two non geostationary satellites (FM-3, FM-6) and one geostationary satellite (FM-5). Sirius explains it as follows:
The enhanced geographic coverage anticipated from the successful launch of FM-5, coupled with satellite technology advancements included on FM-5 and FM-6, will allow Sirius to reduce its GSO constellation from three to two satellites.
FM-6 will have twice the transmit power of FM-1 and FM-2.
In the appplication, there is this little nugget of information concerning its overlay modulation currently used for backseat video:
The digital stream throughput is 1.35 Mb/s. The additional transmission capacity will be used for providing subscribers with more audio channel programming and data and is currently providing three compressed video channels primarily for vehicle back seat viewing. Each video is compressed to approximately 255kb/s.
This gives us some ideas on what we might see for the number of audio channels. Presently, music is compressed to 44 kbps; voice, 20 kbps; and 16 kbps for low quality audio such as traffic and weather. The above implies spare capacity of 585 kbps, enough for 13 more music channels.
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