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Old 02-09-2004, 01:31 AM   #46
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Default Re: Old Russian spy satellite orbits

Quote:
Originally Posted by tiga
Last year I spoke to a Sirius engineer that told me that Sirius had the orginal rights to XM's Satellite positions in space but choose the eliptical orbits instead. He said that the current orbits are old Russian spy satellite orbits and that the Russians had perfected these orbits years ago. He said that the satellites require seasonal rocket firing to mantain that exact orbits although gravitational forces take care of the rest.
That's somewhat correct. Sirius did originally file with the FCC for two geostationary orbital slots, and changed that to 3 geosyncronous satellites. The cost was slightly higher, because another satellite would have to be purchased, but it lowered the terrestrial cost since a smaller repeater network would be needed.
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Old 02-09-2004, 01:40 AM   #47
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Default Re: Old Russian spy satellite orbits

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Originally Posted by BuggyBoyVT
That's somewhat correct. Sirius did originally file with the FCC for two geostationary orbital slots, and changed that to 3 geosyncronous satellites. The cost was slightly higher, because another satellite would have to be purchased, but it lowered the terrestrial cost since a smaller repeater network would be needed.
Makes you wonder if that was the right decision after all? Especially considering the problem that most folks have with home/office reception.
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Old 02-09-2004, 02:09 AM   #48
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Each has it's pro's and con's.. I think Sirius's orbit has more advantages than disadvantages. More pro's especially in just how far the satellite signal propogates and how infrequently it is disrupted comparative with geostationary.
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Old 02-09-2004, 02:25 AM   #49
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Default Re: Old Russian spy satellite orbits

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Originally Posted by DAB
Makes you wonder if that was the right decision after all? Especially considering the problem that most folks have with home/office reception.
Think how much easier it will be to serve Canada.
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Old 02-09-2004, 08:54 AM   #50
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So 2 sats over US at a time. Does the antenna blend a signal from both or pick the strongest signal or the first signal it encounters.
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Old 02-09-2004, 09:20 AM   #51
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The same data is sent twice. First from the highest satellite then from the lower, as I recall.

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So 2 sats over US at a time. Does the antenna blend a signal from both or pick the strongest signal or the first signal it encounters.
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Old 02-09-2004, 04:47 PM   #52
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Quote:
Originally Posted by clockcalibrator
The same data is sent twice. First from the highest satellite then from the lower, as I recall.

Quote:
Originally Posted by rick123
So 2 sats over US at a time. Does the antenna blend a signal from both or pick the strongest signal or the first signal it encounters.
It can actually be in either combination, because it will rotate throughout the day as the satellites handoff. It's time diversity in either way..
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Old 02-12-2004, 09:43 AM   #53
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Default Costa Rica, Panama Canal and further south

With careful aiming of my little Audiovox antenna at an easterly angle (!) I was able to receive Sirius from the Island Princess cruise ship veranda from Costa Rica and while transiting the Panama Canal. The receiver showed three bars. I suspect that the Sirius satellite signal will vary and change direction in these Central American countries throughout the day. Based on the southern location of the Panama Canal I'll bet that one can receive Sirius in the northern part of South America at times.
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Old 02-12-2004, 12:12 PM   #54
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Quote:
Originally Posted by BuggyBoyVT
Currently,
XM is busy perfecting terms to launch XM-3 (replacement) and will have to purchase a new satellite to replace XM-1 and XM-2 within the next 4 years.

While Sirius is perfectly fine financially, and will currently get 15 years out of all 3 satellites. (Late 2015)... And they have virtually no debt, and all 3 satellite are completely paid for.
I think that XM-1 & XM2, operating at half power, will sucessfully reach the end of their design lifetime with no replacement. XM will have to *purchase* the replacement satellite (for ground spare), but they won't *have* to launch it.

So far as debt, Sirius chose dilution, XM chose debt. Both are valid business plans.
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Old 02-13-2004, 01:47 AM   #55
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I would guess that the sats also turn off above South America to save energy and charge up their batteries.
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Old 02-13-2004, 01:54 AM   #56
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Actually, most satellites have solar panels.. And being 22,300 - 29,000 miles away from the Earth, there is always sunlight.. so, there really is no reason to conserve power!
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Old 02-13-2004, 09:50 PM   #57
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Thats true but I was thinking more along the line that purhaps they don't have the battery capacity to transmit 100% of the time, so they use their off time to recharge the batteries. I don't know anything about satellites, I was just thinking out loud (so to speak). Tim
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Old 02-18-2004, 06:44 AM   #58
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I added the Keps from the link below to my Starry Night program. I now know exactly where the birds are located above my horizon . I discovered that all three birds are overhead at times even though only two are broadcasting at any given moment. Does anyone have a good satellite tracking program which will show the Sirius birds circling around the globe?

Quote:
Originally Posted by rickets
But, XM's satellites are over South America, so doesn't that make them just as far away as a Sirius satellite straight up?

http://www.fourmilab.ch/earthview/satellite.html

Right now, Sirius 2 is 40904 kilometer = 25,416.6 miles straight up from Missouri.

Quote:
Originally Posted by BuggyBoyVT
Sirius satellite are farther away than geostationary orbit, by quite a bit more.. ...Geostationary is 22,300 miles vs Sirius geosyncronous orbit which is about 28,500 miles from Earth.
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