[opendtv] Re: 47 year old television signals bouncing back to earth
- From: Olivier Houot <olho_avatar_i@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 21 Dec 2011 23:16:52 +0100
Albert Manfredi wrote:
>
> Stupid arithmetic problem, but it does change the answer, at least in
> an emotional way. Here are the corrected numbers:
>
>
> Pluto is between 4.2E+9 Km and 7.5E+9 Km from Earth, which means that
> in principle, this signal could be receivable just within our solar
> system.
>
This is the classical limit for the solar system, indeed, but it has
expanded recently to at least as far as Eris which currently lies at
14.6E+9 km.
If we had people there, they could not rely on leakage, then, but a
focused beam from earth could retransmit broadcasts with good quality in
digital format.
Perhaps some advertisers would be interested in sponsorizing the
link .After all, it would be possible to sell multimedia contents over
it, and be payed electronically in return (though the target population
is likely to remain scarce).
Mars Reconnaissance Orbiter is capable of 6Mbps at a 100 millions
kilometers range with a 3 meter antenna fed with 100 w at 8 Ghz(not
clear from nasa Website whether it is the power absorbed by the
amplifiers or delivered to the antenna). Are you willing to compute the
requirement for an equivalent Eris link (a bit late in the evening for
me to attempt it, or just plain lazyness :-) ?
A simple calculation based on inverse square law leads me to conclude
that increasing the power up to about 2 Mw would compensate for the
extra distance. But one would probably choose to relax that with bigger
antennas.
However, since both sending and receiving planets are rotating, to keep
constant contact it could be decided to put those antennas in orbit
rather than on the ground, which would put tighter limits on size and
available power.
But light is so slow that hot news would be at least 13 hours and 30 mn
old ...
I was never completely convinced quantum entanglement could not be used
for superluminic information transfer, but so far only science fiction
writers have risen to the bait.
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