[Laser] How much power? Ideed!

[Pat Barthelow]

I've been reading the mail, with interest...
I did some research on how the science community has used the retroprisms in 
ranging experiments.  There is a lot of science data, here, with details of 
how long it takes to detect a single (or a few) photons returning from the 
moon, from powerful, telescope based transmitters.
Also, somewhere in there, is a telephoto of the moon with exact locations of 
the various retroprism arrays, placed on the moon, during the Apollo 
program.
Lots of good optical data here.... enjoy:

MOON RETROPRISMS:
http://funphysics.jpl.nasa.gov/technical/grp/lunar-laser.html
http://physics.ucsd.edu/~tmurphy/apollo/doc/matera.pdf
http://physics.ucsd.edu/~tmurphy/apollo/apparatus.html
http://physics.ucsd.edu/~tmurphy/apollo/apollo.html
http://physics.ucsd.edu/~tmurphy/apollo/TR_insight.html
http://physics.ucsd.edu/~tmurphy/apollo/lrrr.html
http://www.jpl.nasa.gov/news/features.cfm?feature=605
http://geophysics.ou.edu/solid_earth/readings/apollo_laser_ranging.html
http://www.anthonares.net/2006/03/bouncing-laser-beams-off-of-the-moon.html
http://www2.abc.net.au/science/k2/stn-archive1/posts/topic6189.shtm
http://science.nasa.gov/headlines/y2004/21jul_llr.htm
http://syrte.obspm.fr/journees2005/s1_20_Bouquillon.pdf
http://www2.jpl.nasa.gov/files/releases/lunlaser.txt

Sincerely, Pat Barthelow     aa6eg at hotmail.com
http://www.jamesburgdish.org
Jamesburg Earth Station  Moon Bounce Team
http://www.cq-vhf.com








>From: Art <KY1K at verizon.net>
>Reply-To: Free Space LASER Communications <laser at mailman.qth.net>
>To: Free Space LASER Communications <laser at mailman.qth.net>
>Subject: Re: [Laser] How much power?  Ideed!
>Date: Thu, 07 Jun 2007 14:06:02 -0400
>
>You wouldn't see a laser based on the Moon. Although the laser is 
>collimated, the few (at best) photons that arrived on Earth would be masked 
>by the Moon's reflectivity of the sun (light that bounces off the Moon and 
>makes it's way to Earth).
>
>The only hope of seeing a laser on the Moon (from the Earth) would happen 
>only if the laser was located on the dark side of the terminator. In such a 
>case, the field of view would have to be very narrow, about the same as the 
>divergence of the laser transmitter, or around 2 to 5 milliradians. It 
>would be just as difficult to aim receiver as it would be to aim the laser. 
>When you consider that both the Moon and the Earth move relative to each 
>other, both ends would need to be actively tracking each other.
>
>I think receiving a laser based on the Moon would be difficult and a 2 way 
>QSO between the Moon and the Earth would ne next to impossible for 
>amateurs.
>
>Receiving an Earth based laser from the Moon would be even worse, the Earth 
>is a much better reflector than the Moon is, so the background ambient 
>light level would be much worse.
>
>
>
>
>
>
>>If there
>>were a Moon Base or just a rover up there with the equivalent of a
>>laser pointer, 5 mW and 1.5 mR beamwidth, it could send a spot down that
>>would be 360 miles across. How much of a telescope would you need to see
>>that?
>
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