Astra 1N - made it to geostationary orbit, now the fun starts

[Lazarus]

Scintillation ................. (qv)

 

[M60]

25.2E now folks, only three degrees to go!

 

[solly]

astra 1n now near eurobird 2 25.5e

 

[Huevos]

Actually Huevos on that bit your wrong. The atmosphere can play as huge role in how the signal is effected.

Nano that is a different case from what I am talking about, and certainly in the case of Astra 2D you could almost set your watch by the diurnal power fluctuations. When a satellite does the same thing day in day out, month in month out, and the satellite in the adjacent slot does the complete opposite it is unlikely to be anything to do with the time of day or atmospherics, and more likely to be down to how well the solar array is illuminated or the satellite's ability to maintain stable attitude control over the 24 hour period.

 

[M60]

Nano that is a different case from what I am talking about, and certainly in the case of Astra 2D you could almost set your watch by the diurnal power fluctuations. When a satellite does the same thing day in day out, month in month out, and the satellite in the adjacent slot does the complete opposite it is unlikely to be anything to do with the time of day or atmospherics, and more likely to be down to how well the solar array is illuminated or the satellite's ability to maintain stable attitude control over the 24 hour period.

I suppose with the acceptance angle of a 2.4 or 3.1mtr dish being 0.5deg or less then any fluctuations in the satellites orbit within it's "box" as it were, are going to cause issues.

 

[Huevos]

I suppose with the acceptance angle of a 2.4 or 3.1mtr dish being 0.5deg or less then any fluctuations in the satellites orbit within it's "box" as it were, are going to cause issues.

The 2D thing is not down to the satellite moving around in its box. The reason I say that is because the satellite not holding station does not follow a daily rhythm. It also is not down to the atmosphere or being night. Here's why. Where I am horizontal transponders are almost impossible on a 2.4m dish. 100km north of here (on the same size dish) horizontal transponders are lockable in the morning and continue through most of the afternoon and then drop below the receive threshold some time around 5 o'clock. On the other hand 100 km south of here the same transponders can't be received all day, but they appear about 6 o'clock and are receivable for most of the evening. This has been going on since the satellite arrived at 28ºE. To me this suggests there is a slight north/south shift of the satellite's footprint over each orbit. I've no idea what causes it but I can't come up with any other explanation for this phenomenon.

 

[A nonymous]

Nothing like a bit of banter is there

I do have to agree with you on the north/south shift, it makes perfect sence. I get this on the German beam on 23.5e. There seems to be no fixed time on wether or not i can get Kabel Deutchland. The weather seems to have very little influence on this, although the signal does stay stable a lot longer on a nice clear day but inevitably it disapears again.

I dare say with a bigger dish i could get it 24 hours a day, but as i am outside the official footprint and only with a Penta 85 dish i would imagine its the same effect as you have with 28.2e.

 

[dvdfilm]

at this point are the tracking sites still reliable regarding Astra 1N position or would the orbit be already modified by the control station?

 

[Analoguesat]

at this point are the tracking sites still reliable regarding Astra 1N position or would the orbit be already modified by the control station?

As soon as she starts decelerating to slot at 28E the tracking will become unreliable for a couple of days until its corrected. In the past Ive seen it take anything up to a week for a newly geostationary bird to be correctly identified on n2yo

 

[M60]

As soon as she starts decelerating to slot at 28E the tracking will become unreliable for a couple of days until its corrected. In the past Ive seen it take anything up to a week for a newly geostationary bird to be correctly identified on n2yo

Won't the deceleration only take place when the orbit raising burn is carried out so in effect the satellite will only slow down so it's in exact movement with the Earth and thus seen as 'stationary' from the Earth viewing perspective? The satellite won't in effect be slowed down, surely the orbit raising procedure will slow it's speed to that of the earth's rotation (being lowered somewhat it's currently in a faster Earth orbit so thus seen as 'moving' from our perspective being on the planet!). If this takes place about 12hrs before it's arrived at it's final orbital slot then that would only make the last 0.38deg eastwards movement slower? I suppose we're back to the same scenario we all discussed last week - I should read up about it on Wikipedia although this forum thread provides an interesting learning curve.

 

[Huevos]

Won't the deceleration only take place when the orbit raising burn is carried out so in effect the satellite will only slow down so it's in exact movement with the Earth and thus seen as 'stationary' from the Earth viewing perspective? The satellite won't in effect be slowed down, surely the orbit raising procedure will slow it's speed to that of the earth's rotation (being lowered somewhat it's currently in a faster Earth orbit so thus seen as 'moving' from our perspective being on the planet!).

It's not deceleration, it is acceleration. This is kind of contrary to rational thought because in its current orbit it is moving forward faster than geostationary, but to get it to geostationary it needs to be accelerated to a high speed. After the burn the satellite has more forward speed and this throws it further out, but by the time it arrives at the higher orbit that speed has been absorbed (by gravity) and it is then moving forward at a slower speed than its previous speed in the lower orbit. On the other hand, when a satellite is being drifted from east to west the opposite is true because an east to west drift requires the orbit to be raised above geostationary (so it goes slower than the sidereal period of the Earth).

 

[M60]

It's not deceleration, it is acceleration. This is kind of contrary to rational thought because in its current orbit it is moving forward faster than geostationary, but to get it to geostationary it needs to be accelerated to a high speed. After the burn the satellite has more forward speed and this throws it further out, but by the time it arrives at the higher orbit that speed has been absorbed (by gravity) and it is then moving forward at a slower speed than its previous speed in the lower orbit. On the other hand, when a satellite is being drifted from east to west the opposite is true because an east to west drift requires the orbit to be raised above geostationary (so it goes slower than the sidereal period of the Earth).

I'm with you now, it is sort of contrary to rational thought but I suppose that's because we're seeing it from Earth where we're also moving. If we could view the whole thing outside of Earth's orbit it would make perfect sense. Didn't realise that East to West movements require a higher orbit raise from GSO but again makes perfect sense as, like you say, your slowing the craft down in relation to the speed of the Earth's movement and as such gives us all the impression from a 'looking up' perspective that it's moving.

So when 1N does it's burn to take it back up to the higher orbit, will they calculate this so that once it gets there the thrust given is absorbed totally and in effect slows down totally to match GSO speed or would another slight opposite burn be required to, in effect, stop it where they want it?

 

[Zorba]

Edit - No wishes for spacecraft destruction if you please - admin.

 

[Huevos]

another slight opposite burn be required to, in effect, stop it where they want it?

Actually it is the opposite. The first burn speeds it up but once it reaches the higher orbit it has lost the extra speed used to overcome gravity and so it drops back down to the lower orbit. If left without any further burn it would oscillate between the lower altitude and GSO altitude over each successive orbit. What the second burn is for is to give it more energy to keep it at GSO, not to take speed out.

 

[Zorba]

Edit - No wishes for spacecraft destruction if you please - admin.

 

[M60]

Actually it is the opposite. The first burn speeds it up but once it reaches the higher orbit it has lost the extra speed used to overcome gravity and so it drops back down to the lower orbit. If left without any further burn it would oscillate between the lower altitude and GSO altitude over each successive orbit. What the second burn is for is to give it more energy to keep it at GSO, not to take speed out.

I'm with you. So after the first burn, it left at that, the satellite's Perigee would be it's lower orbit, Apogee at GSO and would oscillate between the two per orbit. The second burn therefore at Apogee circularises that new higher orbit (at GSO) to keep it there.

 

[solly]

satellite now 27.90e

 

[dvdfilm]

satellite now 27.90e

Where did you get that solly? n2yo still has 1N at 27.5E

 

[solly]

_http://www.lyngsat.com/tracker/astra1n.html
on lyngsat post il

 

[dvdfilm]

Thanks solly.
Anytime is good from now for SES to do their press release about 1N