[amsat-bb] Re: Phase 4 versus Eagle
vk3jed at gmail.com
Tue Dec 11 22:08:44 PST 2007
At 04:24 PM 12/12/2007, Edward Cole wrote:
>Good points! Most of you probably do not realize that geostationary
>satellites are not high in the sky from high latitudes. From my QTH
>(60.7 degrees north) the maximum elevation angle to the Geostationary
>orbital plane (also called the Clarke Belt) is 21 degrees. That is
>to a satellite positioned over the latitude of Hawaii (Longitude
>150). If the satellite is parked too far east or west, it will be
>below the horizon to us. That is true equally to north and south hemispheres.
Agreed on that one. here at 38S, that's not too much of a problem
over a fairly wide arc.
>I have written this before. The reason the Phase-3 satellites were
>so popular was that they were in highly inclined orbits (to the
>equator). Geostationary orbits are not inclined at all (ideally zero
Well, the planned orbit of AO-40 wasn't that great down here. The
high altitude segments would have reached a maximum of 20 degrees
above the horizon. At the time AO-40 was launched, I had
obstructions up to 30-40 degrees up. The orbit it wound up in was
_much_ better, but of course as we know, AO-40 died prematurely,
unfortunately. I wasn't around for the earlier P3 birds. :( Where I
am currently, a 20 degree elevation would be difficult again, with a
block of flats forming a major obstruction. Some win, some lose.
>This does not mean I am apposed to P4A. I am thoroughly in favor as
>it is a great opportunity. But designers do need to realize the
>impact for access to them (and I am sure they are aware). The rest
>of you need to think about it to see the difference it will
>make. NZ, AK, Aust. and Japan all will only be able to access a
>Pacific satellite. DX range will be quite different than of the Heo
>(Molinya) orbit. Africa will never be in range of Alaska on
>Geostationary sats, unless satellite-to-satellite linking is
>incorporated. We have already heard that this is not being considered.
Well, not direct satellite to satellite, but there has been talk of
linking via the ground segment, which would be much easier to
maintain and upgrade, with all the "intelligence" on the ground.
>For this reason I hold on to hope that P3E and one Eagle gets into a
>high inclined orbit. If not then you can always work me on
>OSCAR-ZERO since the (Moon) orbit is inclined 26 degrees!
Well, for me, the previous high inclined orbits aren't that
interesting, but if both proposals eventually got off the ground (so
to speak ;) ), then we'd have a mix of birds to play with. :) As for
the Moon, I'm afraid that's outside my capabilities for the
forseeable future. :(
>Here is another fact to consider: ISS only reaches 11-12 degrees
>elevation above our southern horizon. The orbit of ISS is inclined
>51 degrees above the equator. Of course partly this is because it is
>only 200 miles above earth. 23,500 miles is a bit more. The Moon at
>250, 000 miles is even more.
> How about earth-bound sat-gates to relay between Geo's?
That has been talked about, and I support that idea.
73 de VK3JED
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