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First, SIRI's satellites are in geosynchronous orbit. They are not in geostationary orbit. Satellites in geosynchronous orbit orbit Earth once every 24 hours. Satellites in geostationary orbit orbit Earth once every 24 hours over Earth's equator.

SIRI uses three satellites in a style of geostationary orbit called a Molniya orbit. They orbit the earth every 24 hours, but are inclined so that at its apogee (farthest and slowest part of the orbit) it is high over the United States. The period of which the satellite is in the best position to transmit is approximately eight hours, requiring three satellites to cover the United States 24 hours per day.

There are several errors above. First you claim that SIRI's satellite's are geosynchronous and in the next paragraph you claim they are geostationary. If they were in a geo orbit, the correct term would be geosynchronous, because the orbit is inclined. However...

You then claim that the satellites are in a molniya orbit. Molniya orbits are NOT any kind of geo-orbit. A geo-orbit has a period of 24 hours. A molniya orbit has a 12 hour period.

XMSR does the same thing. In fact, this is where SIRI should have an advantage. Their use of Molniya-orbiting birds is supposed to result in far less signal shadow becuase, during the eight-hour period that each satellite is overhead, they are much higher overhead than XMSR's satellites.

I would tend to hypothesize the opposite. The molniya orbit is only 5000 km higher at apogee (40080 km vs 35790). In addition, it is not at that height for the entire 8 hours. It is only higher for approximately 4.5 hours of the 12 hour orbit.
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