[amsat-bb] Re: Geostationary Satellites

Ken Ernandes n2wwd at mindspring.com
Tue Oct 11 03:31:23 PDT 2011

You are viewing it only from the point of view of signal interference.  In reality, the greater issue is maintaining our position and the risk of collision.  There is a very tight band that defines geostationary and there are some significant disturbing forces: Earth's triaxial gravity distribution, lunar and solar gravity, and solar radiation pressure.  This mandates that there be vigilance in monitoring the satellite's orbit and those of its neighbors and to also have a propulsion system capable of station-keeping on a regular basis.  Even without the risk of collision, not holding the position tightly nullifies the benefit of fixed antenna pointing.

For those believing in the large space, small satellite theory, the risk of collision is more real than one might think.  I could only imagine the legislation and regulations that might be placed on amateur satellites if we failed to control our bird and it collided with a very expensive commercial or government asset.  Until AMSAT can build enough experience to operate a propulsion system reliably for the long term, I don't think we can responsibly operate a satellite bus on a congested orbital highway.

73, Ken N2WWD

Sent from my iPad

On Oct 10, 2011, at 10:59 PM, Paul Williamson <kb5mu at amsat.org> wrote:

> On Oct 10, 2011, at 3:03 PM, Ken Ernandes wrote:
>> 1.  There are a finite number of orbital slots at Geostationary.  That is essentially like water front property.  
> I've heard that asserted before, but I question the reasoning.
> My understanding is that spacing of satellites around the geostationary orbit is dictated by the beamwidth of the ground station antennas. In other words, it's a matter of spatial frequency sharing. The satellites have to be far enough apart that a ground station antenna can illuminate one of them without causing too much harmful interference to the ones in the adjacent slots, after all the expected errors (orbital and ground station pointing) are taken into account.
> If that's correct, since amateur radio satellite operate on different frequencies from the commercial satellites, there is no conflict between amateur radio satellites and commercial satellites for orbital slots.
> Where have I gone wrong?
> 73  -Paul
> kb5mu at amsat.org

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