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Re: AO-40, double hop and the Moon?



I would have to say AO-40 is probably not ideal for relaying to lunar 
ops or radio astronomy, although I'd be interested in seeing sats that 
are designed with these applications in mind.

Double hop via chain of two satellites is possible if one sat's uplink 
can hear another one's downlink, but again, the pattern of both sats' 
antennas would have to be compatible, and AO-40 was definitely designed 
to have its maximum Rx sensitivity and TX envelope in the earth-facing 
direction at apogee near GEO distance (it wasn't moved far from GTO 
before the propellant accident but was intended to operate in a 
sun-synchronous orbit fairly near the original GTO anyway) so it is 
unlikely that it would be able to cross link to another sat.  Again, an 
idea with interesting possibilities, just not likely to be feasible 
with *this* satellite.

Now .. extending the idea in terms of possibilities for future systems 
.. if it were possible to design sats as part of a "constellation" that 
could relay between each other, sideband and packet on 2m/440/1.2/2.4 
etc. could become far more useful in general, worldwide.  Basically the 
equivalent of a "linked repeater" system in orbit, although linear 
transponders and digipeaters are more practical than FM for obvious 
reasons.  This could be a worldwide (more or less) satellite packet 
relay system at the very least ..

As far as assisted EME, I don't know if a sat could help.  What would 
be better would be something like an RTG-powered linear transponder on 
the lunar surface, with a very simple and rugged construction to last 
at least a few years of day/night heating and cooling.  I don't know if 
that device is even possible to design and construct, and I do know it 
would be *hideously* expensive by AMSAT standards to launch and deliver 
it, but if any future lander missions go to the moon it would be nice 
to have a design ready for a small package that could piggyback on it, 
something like a simple translator and TFT amp that could act like a 
simple "bent pipe" frequency-wise.  I've thought extensively on this 
and have some ideas, but not sure if they'll stand up to experiment or 
not because I can't afford to prototype it with the parts that would be 
suitable to build it.  It's on the table though ..

On Wednesday, Mar 12, 2003, at 00:43 US/Central, A Thomas wrote:

> Woke up at dawn thinking about using satellites as relays to longer
> distances, looking out of earth orbit rather than staying in it.
>
> If AO-40 at apogee is 53k + kilometers out then at some point it must 
> be at
> its best position relative to the earth and the moon, therefore could 
> act
> as a relay to any moon expedition (or moon data uplink)? easier for us
> earthbound to reach AO-40 due to power considerations. Like a 2 stage
> rocket really. The same would apply to an expedition to Mars should 
> humans
> ever do so. There must be times when the antenna in AO-40 can be 
> oriented
> towards earth and elsewhere in the universe - if the LittleGreenMen 
> have
> the squint pointing at them then they could come up on 70cm and be 
> heard on
> earth on 2.4 GHz! But I wonder if we could not listen on say 2m (144 
> Mhz
> isn't a bad frequency for Pulsars) for amplitude as the antenna scans
> through distant radio sources? We would need to visualise the orbit in
> relation to these sources.
>
> The double hop could also be tested with ao-40 as a second stage. If 
> say
> FO-29 was visible from AO-40 would AO-40 hear her? Then you could be 
> heard
> on 2.4GHz downlink over a whole hemisphere while calling into 
> LEO..(return
> path again AO-40).If the ISS ever used ssb could that go to AO-40 (I 
> assume
> 2m packet wouldn't be welcome on AO-40)...

Heard from a flight instructor:
"The only dumb question is the one you DID NOT ask, resulting in my 
going out and having to identify your bits and pieces in the midst of 
torn and twisted metal."
----
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