Question: radiation pattern of a moved satellite

[sector_d]

I am curious about the possible alternatives of the resulting footprint of a "moved" satellite comparing with its previous position / original footprint. I don't remember the case, but some years ago I belive I was surprised by the outcome (can't remember which moved satellite it was). So, let me ask what happens, tell me which is more close to correct:


a) for most satellites, where the downlink antenna is fixed, the result pattern is simply the same as the original coverage, i.e., the shape will be similar, but just translated by the longitide difference, and so will be incident in another part of globe. I imagine Astra 5B @ 31.5 E is one example of this.
- Can in any case the satellite operator change the angle (to ground) of the antenna or any other parameters? For example related to the satellite axis stabilization, so that they can tweak the beam?

b) If the antenna is steerable, in theory the coverage area can be the same in new position if longitude difference is not very big, but normaly the coverage area will be different. The shape can slightly change due to the different angle to ground surface.

c) And, is there any possibility that the diagram is both translated to different zone of globe and pattern shape is significantly changed? At the moment, are there satellites with phased array technology or adpatvide antennas that can change completly the result footprint? (like next Eutelsat Quantum)

 

[Terryl]

On most satellites the coverage beams are fixed, if the satellite had spot beams (local coverage areas) then these would be affected, on some there are global coverage beams, or wide area beams, these beams would not be affected by a move, some if they are to be used as backups or emergency replacements have transponders that are not in use, these can be turned on to cover different areas then originally planned.

If the satellite in question has been moved to a new position and can still see the original coverage area, (not below the original horizon) it can be tilted in positioned to still cover that area.

If a satellite was originally designed to cover lets say northern Europe, and was moved to a location over lets say Japan, then the new coverage area would be a problem.

Here state side Dish Network and others use satellites with local spot beams, these spot beams cover very small areas, if one of those satellites goes down, there is not much they could do about moving a different satellite in to cover those areas, unless the replacement or standby satellite had originally been planed for replacement of that satellite with spot beams.

In some cases when a satellite for a location gets to a couple of years to end of it's planned life time, and a new satellite takes it's place, the old satellite is moved to a parking orbit, station keeping or place holding orbit, and is put in standby, it could replace the new bird if a problem comes up.

You can look at the coverage area on most satellites in a web site called ""satbeams.com"", it will show you on most satellites its coverage area for that satellite.

Opps sorry ...Tooo much coffee this morning...I will go away.