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AMOS 5i problem

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Space
Ex Member


Aug 28th, 2010 at 3:07pm  
Hello  List I have a few sites  on AMos 5i that Keep having a problem of low EBNO every day  for last three days.

problem starts  at around  3 Pm  EAT  .

Is there some information that we have not been told about the satellite?
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lighthouse
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Reply #1 - Aug 28th, 2010 at 7:29pm  
I read this about the satellite. follow the link below:

http://www.haaretz.com/business/israeli-satellite-amos-5i-about-to-run-out-of-fu...
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handeil
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Reply #2 - Sep 10th, 2010 at 10:58am  
Hi!

I think it's related to this information here:

http://satelliteserviceadviser.blogspot.com/2010/09/sun-outage-predictions.html

Just scroll down to the bottom to see some sample results.

Though there's a mistake on the table presenting the predition results, however, common sense will help you understand it correctly.

Good luck!

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Eric Johnston
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Reply #3 - Sep 10th, 2010 at 2:06pm  
If you do the calculation for a remote site location you will get the times for sun noise receive Eb/No reductions at the remote site.  If the sky is clear you will probably see the shadow of the feed horn at the bottom centre of the dish.  The sun is behind the satellite.  The radio noise from the sun tends to drown your wanted receive signal from the satellite.

Do the calculation again, but this time using the teleport hub lat/long (instead of your remote site), and you will get the dates and times when your site transmit signal may not be successfully received at the hub.

Sun noise degradations occur around the spring and autumn equinoxes, about the same time each day, for about 5 days in a row and for a few minutes.

Best regards, Eric.
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« Last Edit: Sep 14th, 2010 at 10:51am by Eric Johnston »  
 
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Space
Ex Member


Reply #4 - Sep 13th, 2010 at 9:25pm  
Hi

What other satellite  can we use for  Africa Beam (East Africa)..  Amos 5 is Failing us.

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Eric Johnston
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Reply #5 - Sep 14th, 2010 at 10:42am  
Sun outages last only a few minutes. Your site will get sun outages on your receive path.  Your hub site will get sun outages on its receive path at different times to you.

If you are getting much longer outages at regular times, every day or half day this may be due to the inclination of the satellite increasing so that at times of day the satellite moves out of the beam of your fixed pointing antenna.

Satellites are normally kept +/- 0.15 deg north south and they remain within the beam of small fixed pointing antennas.  If the inclination is much larger e.g. +/- 0.8 deg, or you have a large hub dish, then you need a trackling antenna, that repoints itself every 10 minutes or so.

satellite
This image shows the result of having a badly pointed dish, whose beamwidth does not include the whole of the daily satellite movement range. It does not work all day, even though the satellite is well within its box.  Outages occur daily when the satellite is towards the upper left.

AMOS 5i is due to soon run out of fuel for north south stationkeeping but as of now its inclination is only 0.0816 deg.  It has not yet run out of fuel.   The inclination gradually increases (about 0.8 deg per year) and every few weeks north-south stationkeeping fuel is used to reverse the drift. Think of it as gradually increasing from -0.1 to +0.1 and then being pushed back to -0.1 using the thrusters. Longer term gradual adjustment is also possible using lower thrust ion thrusters.

Recent 2-line orbit elements:
AMOS 5I                
1 23723U 95064A   10256.80216159  .00000089  00000-0  10000-3 0  3262
2 23723   0.0816  78.0600 0002460  85.5602 134.8296  1.00270992 54184
...

Regarding alternative satellites for East Africa please say where in East Africa are your customers and where is the teleport hub. What is your preferred frequency band and polarisation type (based on your existing hardware).

Best regards, Eric.

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« Last Edit: Sep 15th, 2010 at 10:51am by Admin1 »  
 
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