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Re: FM satellites (was: Re: SUNSAT OVER EUROPE)



At the risk of being branded a nay-sayer, I am going to respond to
some of the weaknesses in Mike's proposal.  Somebody has to.
I'm going to concentrate on the negatives; I'll leave it to others to
point out the positives.

At 04:18 PM 7/26/99 -0400, KF4FDJ (Mike in Ft. Myers, FL) wrote:
>What we need, and what I have proposed is a constellation of easy sats. 
>20 or 30 easy birds will facilitate "regular" users, as well as newbies.

If we had launch opportunities for 20 or 30 small satellites, I feel sure
we could find something more interesting to do than make one FM voice
channel.

If we were successful in somehow arranging for the system to be
reliable and easy to use, it would be instantly overloaded. Check out
the widest-coverage 2m FM repeater in a major metropolitan area,
and then multiply the potential user base to account for the size of
the satellite's footprint. This is a recipe for failure.

>If we built 20 or 30, and had them located in every country
>with launch capabilities, eventually we would be able to hitch enough
>rides to have an entire constellation of these birds orbiting the globe.

Each piggybacking opportunity would have special requirements
mechanically and require special approvals (possibly requiring design
changes). No one satellite design is going to work on all opportunities.

20 or 30 satellites without any position control is a long way from
"an entire constellation", assuming you mean full-time coverage of
populated areas, unless you get them into high orbits.  High orbits
are much harder to find piggyback opportunities for, and make for
more difficult link budgets.

You can't wait for "eventually". These satellites would have a limited
lifetime. You'd need to forecast a steady stream of at least a dozen
launches per year, dedicated to nothing but keeping up with failures,
forever.  Even if we're willing to believe in the availability of this many
launches for amateur radio purposes, that's a huge fortune in
precious resources to spend on such a modest goal.  Think how much
we could learn if we used those launches on separate innovative
missions!

Oh, and by the way, the idea of "production line" or "cookie cutter"
satellites has been tried.  It even sort-of worked.  I am referring to
the Microsat series.  AO-16, DO-17, WO-18, and LO-19 were
followed by several spacecraft based on the same design, or a
derived design.  It didn't do much to reduce the cost, or the
difficulty of designing for a specific launch, or the difficulty of
getting approvals.  It did put spacecraft design within reach for
some organizations that would have had more difficulty coming
up with a unique design.

>All of the "bent pipe" repeaters would be on the same frequency pair,
>but uniquely toned, so operators would not key multiple birds.

This would not prevent interference.

>Once the design is formalized, I'm sure the devices could be produced
>for less than $4,000 US.

I'm sure you're off by at LEAST a factor of ten. The days when amateurs
could build something that's just good enough to work and expect to get
a ride into orbit are decades behind us.

>Are you on the bus?

Not this bus.  I prefer one with an interesting destination and a practical
chance of arriving.

73  -Paul
kb5mu@amsat.org
In case it isn't obvious, I speak for myself only.


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