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Re: AMSAT has a SECRET!



> > We will have what Irridium and Teledesic, and Globalstar all promised but
> > never delivered.
> 
> I can't speak for Iridium or Teledesic, but you can buy a working Globalstar phone
> right now.

And last time I checked, Teledesic was a fixed station LEO system (e.g.,
fixed user locations as compared to mobile users with handset-like radios).
That's got quite an effect on the system design.

> >Isn't it interesting!  I noticed, being from the telephone industry, that
> >those LEO proposalls did not seem to notice that 70% of the world is covered
> >in water and even I could see there were not many whales and sea lions that
> 
> Actually, Globalstar did notice this fact. The satellites are designed
> to use the quiet time over water to recharge batteries for use when
> loads are greater. Of course, right now they all have strongly
> positive power budgets anyway...
> 
> >Well this is doable IF AMSAT had satellites that were consistent and
> >reliable the manufacturers would rise to the opportunity.   What we need is
> >to keep the complexity on the ground (such as digital modulation schema etc)
> >and make the satellite as simple as possible.
> 
> Exactly. Not only would this make the satellites more reliable, but it
> would decrease the total system (ground segment + space segment)
> costs. I have never understood how so many members of an organization
> that prides itself on clever, ingenious and cost-effective engineering
> can miss the most basic principles of system engineering.

You might also look at the Skybridge system proposed by Alcatel and
others.  They made quite a different design choice than Teledesic
(also a fixed user system) with most of the interesting stuff on the
ground, and bent-pipe transponders on satellites.  This also enables
them to adapt to different user requirements (e.g., narrowband voice
vs. broadband data) without changes in the space segment hardware.

louie

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