Wasn't it dave schneider who wrote:
(Henry Spencer) wrote in message news:Hzrzu9.318@spsystems.
net...
In article ,
Benign Vanilla wrote:
Even the biggest dish antennas are nearing the limits of picking up
Voyager's weak and distant signal...

I wonder why we would not launch some intermediate satellites to act as
repeaters. Seems they could be light, fast and cheap and extend the life of
these other missions.
What are the complexities?

Mostly, that the idea doesn't work very well. The problem is that a relay
satellite halfway to (say) Voyager 1 will be hearing a signal only four
times as strong as what Earth is hearing... and the antennas and receivers
on Earth are much more than four times as good as the ones on a cheap,
lightweight relay satellite.

At what point would it be worth it to add a long leg to the net of
earth-based dishes by placing a dish at, say, a Lagrangre point?

I don't think this would pay much in terms of making the effective
antenna any larger than building another eb dish, and synchronizing
things would probably be a bit fussy.

My take is that the advantage would be that this antenna would be
available for long stretches because diurnal pointing issues wouldn't
be involved. There would be occultations occuring slightly later or
slightly before the eb antennas experience them.

In fact, this sort of application would probably only happen if there
was another reason to populate that position and the dish could be
piggybacked on that for relatively low cost.

Well, yes. A modest sized dish at a Lagrange Point would be wonderful
for radio astronomy, because the resolution increases with the size of
the baseline. At present the synthetic apertures we can construct are
limited to the size of the Earth. Placing an antenna at a Lagrange point
increases the baseline by a factor of 30.

Synchronising the feed would be no harder that it is for long baseline
arrays on Earth. It might even be slightly easier because the linking
signals may be able to travel in a straight line rather than hopping
round the Earth.

It's not much use for tracking space probes, since you don't need high
resolution for that, you just need high gain. Gain is proportional to
the total surface area of the linked antennae. So you're much better off
building big dishes on the ground than modest sized antennae in space.

Having a continuous feed from a space probe might be a slight advantage,
but we've developed techniques, such as on-board data storage, to cope
with that. If you're piggybacking on a project that doesn't want to be
pointed at your probe all the time, then you lose the continuity anyway.


--
Mike Williams
Gentleman of Leisure