In the analogue days why were most sats at western positions?

Manikm909

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such interesting reading...
 

steeviebops

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This might be an old thread but since it has been bumped I can contribute a bit!

Very interesting it is too, been reading a fair few articles up there, the ill fated launch of Astra 1K I didn't know about. That was an impressive bird 6 meters long.



Yeah I know Sky needed the capacity. My question was really concerned about what decides the orbital position, why did Astra decide upon 28.2e, seems very specific. As far as the UK is concerned 5w to 1e have to be better orbital positions as they satellite sits higher in the sky, so less chance of obstruction interfering with reception.
I'd say the reasoning for the specific positions is because of neighbouring allocations. For example, Arabsat were originally allocated 19°E in C-band, so Astra were slotted in at 19.2. Additionally, Kopernikus were allocated 28.5°E, which was taken over by Eutelsat, so Astra were assigned 28.2°E. The 28.2/28.5 split still exists today.

My uncle (professor of communication at a large UK university) says that gravity is not constant along the equator, and you in effect have troughs and peaks of gravity. It uses more fuel to keep the birds on the "peaks", so they would prefer them in the troughs where they have a tendency to stay.

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This is probably true. There's two "libration points" at 105°W and 74°E where an uncontrolled satellite in geosynchronous orbit will drift towards and eventually settle at.
 

Channel Hopper

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This is probably true. There's two "libration points" at 105°W and 74°E where an uncontrolled satellite in geosynchronous orbit will drift towards and eventually settle at.
Thanks. I was taught that 75 East and 105 West were the gravity wells. Not just GEO either.
 

ozumo

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Could there be anything in the choice of satellite position being influenced by the aesthetics of the installed dishes? In the UK for 28.2/5 east a typical offset dish face is near vertical when installed, which results in a neater looking installation.

Also if Sky was based at say 1W the dish would be 'leaning back' and more likely to collect snow - I noticed in recent snow my fixed 7E dish collected more snow than the fixed 22W dish which remained almost clear. The lower half of 7E dish also gets dirty relatively quickly.
 

Mark2021

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Iceland can receive the UK spot beams very well from 28˚E as it is a straight line to the satellite in line with the UK. I was there recently and the hotel had BBC1 London and Sky News Ireland on their distribution system. The dish was around 1.5m and was a very low elevation.

Regarding the original question: Early satellites had little battery backup and failed operate once eclipsed by the earths shadow. By placing them in the west this happened around 2AM when there were few viewers. I remember seeng 19˚W going off around 1AM regularly.
 
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