Satellite Radio XM and Sirius

[blueflamerick]

I subscribe to XM and have one of the portable players. The only reason I bought it was to listen to Yankees games and the MLB talk channel. I do occasionally listen to Fungus 53.

[winston]

If I were to create a satellite radio service, I'd call it Flippant, so that the ads could say, "Flippant Satellite Radio ... we're not Sirius."

That is bloody marvelous IMO. Too funny! That would make great ad copy.

[8mileshigher]

Some pretty interesting stuff posted here by Forumites and cool links about Satellites.

May we assume that the better "reception" of XM over Sirius is because XM' s is a better type of satellite in the way it is positioned in the sky above the USA ?

If XM and Sirius merge, what happens to XM's one Satellite and Sirius 3 satellites ? Would it be logical to think if they have "surplus" satellites, once they merge, do they shift one or some of the satellite's position, so they can broadcast in other countries ?
Rich F.

[alanz]

XM is a single satellite parked in GEO, which is 24 000 miles (40 000 km) above our heads and from our reference frame on Earth that satellite never moves in the sky). It's not centered over the US, either, so its energy hits the US at an angle. Depending on where you are located that angle might be more overhead than in other places, which can affect reception. Also, because it is so far out it must have a bigger transmitter in order to have the energy reach us here. Sirius is a constellation of 3 satellites that are in a highly elliptical MEO type orbit, so they are constantly sweeping across the sky. Sirius uses a 2 out of 3 active handoff process similar to what happens when you use your cell phone driving down the freeway/expressway/motorway. As you get closer to the next cell the network moves your call to that cell. Similarly, Sirius satellites will hand off to the next one in line as it passes out of sight overhead.

So, you can see they are two totally different solutions to the same problem and there is essentially no commonality between them. In fact there is no commonality between these systems at any level; transmission frequencies are different, encryption is different, channelization is different.

Eventually the commonality we will see is in receiver products; they will integrate both system's tuners into one product so that you will have a seamless experience when you tune to a channel to listen to whatever program you want.

As to moving a satellite into a different orbit, well... that HAS been done, but it requires either a ton of propulsion, which most satellites aren't designed with or some extremely clever orbital mechanics that involve months of downtime and things like putt-putting it into a lunar orbit to sling it back.

Read this. They did in fact do this and it worked. It worked because this particular satellite had not burned its fuel getting to its final orbital location; it was stranded in a useless orbit because of a 4th-stage rocket engine failure of the rocket carrying it. If it had not had that large amount of fuel in it this incredibly ingenious solution would not have worked because the satellite would not have had enough remaining fuel to do a burn.

[alanz]

Here's an orbit tracker page. Doesn't include Sirius though.