[BC] Failing XM Radio

[Broadcast List USER]

Actually, Sirius satellites are not in Low Earth Orbits (LEO).  If  
they were, they would move around the earth.  Also, not all Amateur  
Radio Satellites are LEOs either.  I forget the number, but one of the  
OSCARs was in a polar orbit, spending nearly 11 hours "hovering" very  
high over the North Pole, and then one hour very low zipping around  
the South Pole at a very low altitude.

Sirius satellites "average" altitude is the Clarke Belt, in fact, they  
zip through it.  The satellite tracks a figure 8 path, and has a large  
loop in the southern hemisphere, going low and fast, and goes high and  
slow in the northern hemisphere.

Since it flies through the same spot in the Clarke Belt, the period of  
the orbit is 24 hours.  Because of the inclination, the satellites  
spend the vast majority of the day in the northern hemisphere.  At  
least two of the three satellites are always in the northern hemisphere.

This orbit, called the Tundra orbit, was developed by the former  
Solviet Union because much of their country is far north, and a GEO  
orbit is much less useful for their communications satellites.  It is  
a modification of the Molniya orbit, which is commonly used by Russia  
for their communications satellites.

The Sirius satellites are the only satellites using the Tundra orbit.

--chip

On Apr 22, 2010, at 9:00 AM, broadcast-request at radiolists.net wrote:

> Message: 2
> From: RokprtMike at aol.com
>
> Well I am not sure that would help out too much. XM uses GEO sats  
> (the size of a three story building? and Sirius uses LEO sats that  
> are much mush smaller and much cheaper to store in the garage. Like  
> the Amateur OSCAR system.
> [...]
> Mike