[amsat-bb] Re: Redundant geostaionary birds?
hartzell at gmail.com
Sun Jan 28 16:41:41 PST 2007
I have often wondered the same, whether amateurs could use
out-of-service geostationary birds, but the reality is:
1) Most end-of-life geo-stat birds should get moved into a "disposal
orbit" well above 22,240 miles. The geo-stat parking spots are
precious and must be reused.
2) If for some reason a bird could not get into parking orbit, its
probably dead (e.g. no power, comms, etc). Drifting will begin, and
the spacecraft will probably move into a geo-sync orbit (figure eight
around its initial geo-stat orbit) and slowly toward the equilibrium
points. For this reason every effort is made to move the spacecraft
into the super-sync disposal orbit.
3) Most of the uplink freq's are in the 5.9 GHz range (out of our
allocation) and downlink in the 3.7 GHz range, again, (out of our
There was a plan for a C-band to C-band transponder on Eagle, but that
has been dropped.
I heard that several years ago there was talk of putting an amateur
transponder onboard a commercial geo-sync bird. But I suspect
economics and the fact that all extra mass is reserved for
stationkeeping fuel. Plus power is always critical, and over time,
the solar panels generate less. Anyone know more about this?
On 1/28/07, Andythomas <70374.440 at compuserve.com> wrote:
> Hi gang,
> I was reading an ESA press release about satellite radio experiments and
> didn't realise its emphasis on re-using redundant broadcast tv satellites
> until I read the bbc version of the story at:
> which explains that when the broadcast geostationary saetllites lose fuel
> for position control the tv guys lose interest in them, even though the
> transponders work fine.
> Then I fell to wondering:
> whether we in the amateur satellite service could not use both the up and
> down links on these redundant geostationary birds?
> I don't know the exaxct frequencies but there may be one out there that has
> frequencies we share (or at least the uplink). After all we have years of
> experience of chasing staellites which are not exactly where they should be
> in the sky and so the "wandering geostationary" satellite shouldn't be a
> I think each transponder channel is 27 MHz wide??
> I remember vaguely that there was a "pipe" on one of the birds from the UK
> to the USA which was used in amateur service about 15 years ago now (but I
> don' t remember very much else).
> If we could take over one channel on the transponder then immediately we
> would start looking at uplink equations, multiplex etc. and what about a
> mobile aprs service?!
> 90% of the world will tell you why it can't be done. Who can show how it
> can be done?
> 73 de andy G0SFJ
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