RMW - search www.space.com - h

Sirius uses a trio of Loral FS1300 satellites in unique elliptical orbits in an effort to avoid the problems posed by geostationary satellites.

The orbits, shaped like figure eights, allow the satellites to appear higher in the sky than XM’s, cutting down on the potential for a listener to be out of range of a satellite signal -- and allowing Sirius to have a much smaller number of repeaters.

Sirius’ repeater network also avoids the need for specialized antennas that can track the company’s non-geostationary satellites as they move about the sky, Sirius feeds its repeaters using capacity on a geostationary satellite leased from a traditional satellite operator. Listeners can’t tell that the signals they receive via the repeaters do not travel over Sirius’ fleet of satellites.

The Sirius satellites each spend about 16 hours over the United States, then whip around the other side of the Earth and return eight hours later for another stint hovering over Sirius’ listening area, according to Ted Hessler, the company’s vice president of space segment and enterprise operations.

Two Sirius spacecraft cover the United States at any given time, Hessler said.

Heckler,

I did not find anything there that I had not already seen on Google.  (especially since it used google search)

I was already aware of most of what you related to me, but I don't remember where I got it.

I still would like to see where the satellites go when they are not over north america, and where they are at the various points when they are.  Someone must know.

rmw

Come on folks,

They just announced that the fourm membership is approaching a quarter million.  There has to be someone within a quarter million people who knows the answer to my question.

A little help please.

rmw

Have you tried STK?
http://www.stk.com/products/order/

TTFN

IRstuff,

That looks like what I am looking for, but (1) I am not an aerospace professional, and I don't want to represent myself as such, and (2), when I tried to look at their order screen to see what would be ask regardng (1) above, it would not go there, so I seem to be stuck.  Got any suggestions??

rmw

Sorry, nothing better comes to mind...

TTFN

Thanks for trying to help.  I guess I am still stuck.

rmw

RMW,

There is a site online that will show you the two line element set of the Sirius satellites that is updated once or twice a day.  Its available from the Norad tracking stations.  Here's a link to the tracking data for all unclassified objects that Norad tracks.

http://celestrak.com/NORAD/elements/

And specifically for the Sirius constellation:

http://celestrak.com/NORAD/elements/other-comm.txt

The two line element set is going to give you their location at a point in time and to see a track of their position, you have two easy options.  One is to get a book on celestial mechanics and figure out how to convert a two line element set and then propagate the orbit mathematically.  The second, and already mentioned option, is to download an evaluation copy of STK and enter the set and let it do the conversions and propagation for you.  STK hands out thousands of CDs with free evaluation versions so I would imagine that they would let you download one.  Just checked their website, the following link will let you order a free evaluation copy.

http://www.stk.com/products/eval/eval0.cfm

Hope this helps.

Brian Lewis
The Aerospace Corporation
http://www.aero.org/

valhala,

I don't know who gave you the first star, but I gave the second one.

The links worked, and I got in and got an order in place.

Thanks for your help.

rmw

RMW,

I do hope that helps.  I reread your initial post and another item that STK might help you with is that you can set up mobile ground stations (your car) and then have STK compute the AZEL (azimuth and elevation) that you would need to point an antenna to in order to track the satellite.  Its somewhat complicated, but the STK help files should be able to walk you through the process.

Brian Lewis
The Aerospace Corporation
http://www.aero.org/

Took forever to find, but I found a site with the information and graphing for all three SIRIUS SATELLITE RADIO satellites.  Looks like they complete 366 rotations in 365 days for 8 hour periods.

SIRIUS 1 -
http://www.heavens-above.com/orbitdisplay.asp?sati...

SIRIUS 2 -
http://www.heavens-above.com/orbitdisplay.asp?sati...

SIRIUS 3 -
http://www.heavens-above.com/orbitdisplay.asp?sati...

I don't know why they don't provide this information on the SIRIUS website since it will NOW help me.

Hope it helps someone else,
Robert

robsters,

That is exactly what I was looking for.  I was unable to load the software that valhalla recommended to me because of the boat anchor OS that my computer uses, so I was still stuck.

This answers my question and gives me the help I needed.  Thanks.

rmw

there is an animation here http://www.cashflowbusiness.net/siri_orbit.htm
of the sirius and the xm sats

dffd,

Thanks for that.  That is the best that I have seen, and it makes my observation regarding reception make sense.

I went back to the home page of the site you found this on, and could not find the link to this page.  How the heck did you find this???  I never would have looked here, for sure.

Thanks again.

rmw

it was a link from this page http://www.cashflowbusiness.net/SIRI_vs_XM_radio.h... and i found that page in google

oops i forgot to add this i found too.  so from this it sounds like the keep the link to the sats when they are in the norther hemisphere and they lose there link till them come back 8 hr later


The orbits, shaped like figure eights, allow the satellites to appear higher in the sky than XM’s, cutting down on the potential for a listener to be out of range of a satellite signal -- and allowing Sirius to have a much smaller number of repeaters.

Sirius’ repeater network also avoids the need for specialized antennas that can track the company’s non-geostationary satellites as they move about the sky, Sirius feeds its repeaters using capacity on a geostationary satellite leased from a traditional satellite operator. Listeners can’t tell that the signals they receive via the repeaters do not travel over Sirius’ fleet of satellites.

The Sirius satellites each spend about 16 hours over the United States, then whip around the other side of the Earth and return eight hours later for another stint hovering over Sirius’ listening area, according to Ted Hessler, the company’s vice president of space segment and enterprise operations.

I get some kind of strange effect when in towns with repeaters.  It seems like every highway sign I go under, I lose the signal for a couple of seconds.  It is real annoying.  This happens in large towns like Dallas, and goes away as soon as I get away from the city and back into open country.

When I first began to search for what you gave me, I wanted to know if I would be able to get reception deep into Mexico.  I have been twice, going several hundred miles into Mexico each time, and except for mountain blockage, the reception was fine.

Seems they switch the satellites on far enough south, so that it was not a problem.

Love my Sirius.

rmw

I am fascinated by the Sirius system.   Where can I get orbital elements for their satellites.  By the way, the orbits are not figure 8's (God and Sir Isaac Newton say that is impossible).  They are (I'm guessing) 24 hour (actually 23 56 min) period orbits with a selected inclination, apogee longitude and argument of perigee.  Their GROUND TRACKS  are figure eights.  You can get some really wild ground tracks by varying inclination, period and argument of perigee of an orbit.

Someone had mentioned in a previous post that the Serius Orbits are shaped like Figure Eights. I just wanted to clarify that the orbits are not a figure eight, it just appears that way on a ground track, since a ground track is a 3D-orbit, transposed onto a 2D map.