Satgen 528  To Leo or not to Leo ?  by GM4IHJ (BID SGEN528) 1999-05-08

It is 3 years since a commercial consortium informed the American
Federal Communications Commission  that , " They required the Radio
Amateur VHF and UHF bands for their forthcoming fleet of Low Earth
Orbit (LEO) satellites". At that time there were several LEO projects
underway but none of them threatened amateur radio frequencies.
Developements since then are perhaps due for review. Noting that
things have not quite gone as planned for these existing projects.

Orbcom featuring a fleet of 28 store and forward satellites has
followed the simple pattern pioneered by Amateur satellites Uosat,
Koreasat, Pacsat, and Lusat. After a somewhat hesitant start, Orbcom
appears to be well established.

Iridium a much more complex project of 66 satellites has not fared so
well. Several satellites have failed in orbit and it has been
necessary to launch 20 or more extra satellites to fill in for
failures and, provide in orbit spares. Problems have included
electrical failure and failure to achieve or hold proper station with
respect to the rest of the fleet. In England the franchiser did not
offer handsets for the September 98 opening , and even as late as
February 99 was reported to be holding back sales until better
performance was achieved. Several interesting tests were shown on TV ,
using the simple connection between sats in the same orbit plane but
the more difficult performance using sats in different orbit planes
was not shown. As yet ( May 99) there has been no general advertising
of the service availability in England,

Problems with this ambitious Iridium fleet seem to concern :-
1. Passing a half complete call from a sat going out of range to one
coming in range, seamlessly, without the users being aware of the
shift.
2. Daisy chaining from/to satellites in different orbit planes.
3. A call from or to a phone on a terrestrial network must go to and
from a ground station with up and downlink facilities. ie a ground
station which needs to be licensed by the local government. Who may 
be, and apparently is in some cases, unhappy with the presence of the
satellites on some frequencies.
Nothing about the Iridium situation looks impossible , but as time
goes on it does begin to look as if this ambitious complex project may
be expensive.

By contrast. Globalstar due to begin operating towards the end of
1999, has a less ambitious strategy which should work well. ie Higher
sat altitude, less problematic sat downlink frequency . Plus a simpler
bentpipe repeater format, routing long distance calls via, terrestrial
linked ground stations rather than, intersat daisy chaining.

So is the Leo orbit looking less attractive than it did in 96. Will
venture capitalists be prepared to support exotic technically advanced
projects , gradually filling our skies and our frequencies. The jury
is still out. With a lot riding on the successful, in budget
completion , of existing projects.