[Laser] moon repeater

Wed, 17 Dec 2003 18:27:18 EST

Dave, WA4QAL makes some good points about the glass beads being covered by 
Moon dust if they were balistically scattered.   If you want to know how much it 
takes to get ideas past the "filters" at NASA, ask someone about SAREX and 
ARISS.  For that matter, ask them it was worth the effort.  

The Moon is nice to think about.  So are orbital ideas and baloons.   I still 
need to work on what I can get out of my equipment on the ground.  

Found out some interesting things about reflective signs, cloth, and 
microspheres.  The spheres act like spherical lenses (duh?).  If you put a mirror at 
the focal point of a lens, then a ray of light that passes through the lens 
will strike the mirror and be reflected.  If everything is aligned, the reflected 
ray will travel back out the lens and be refracted parallel with the 
incomming ray.  The mirror does not have to be particularly good for a bright spot to 
show, as in the case of a cat's eye shining in the dark.  A lot of reflective 
signs are made with a reflective layer covered by a spacing layer, then the 
spherical lenses, and usually covered with a protective transparent layer.

The focal length of a spherical lens depends on the index of refraction of 
the material.  It is possible to have a material that will focus much of the 
light striking a sphere on the surface of the opposite surface of the sphere.  If 
the light is reflected from that surface, it will come back out.  This would 
make a cloud of such spheres a very interesting reflector.  There might also 
be preferential reflections like water droplets that make rainbows. 

Would such spheres be better at reflecting light than crystals?  I am sure 
that there are crystal structures that have a retroreflective character, but 
would they have as good a reflective characteristic?

If we got a supply of retroreflective "dust" would it be worthwhile to 
release some from a balloon?  Would it be any advantage over a few yards of 
reflective cloth (perhaps used to make part of the parachute?) hung underneath?   (Or 
as suggested, the body of the baloon.)  For that matter could it be released 
from a satellite close to geosynchronous orbit?  (The dust would have to be 
tiny, or it might pose a hazzard to other satellites?)  If you let glass beads 
out near a radio satellite, it should not  affect radio waves.  Again, would the 
mass of a dust cloud be better used in a more conventional reflector.

James 
N5GUI

In a message dated 12/17/2003 8:16:45 AM Central Standard Time, 
[email protected] writes:

Firstly, the environmentalists (and, probably the astronomers and 
planetary geologists) would throw a fit (possibly even justified).
Nextly, persuading NASA to do anything is almost impossible without
an excessive amount of paperwork and an incredible delay.  
Thirdly, I'm not real sure it would even work, since the glass
microspheres might settle into the lunar dust and be obscured.

Here's an alternate idea (just so I don't come across as 
throwing cold water over everthing).  What are the possibilities
of making either a hot air or Helium balloon out of the 
movie screen material (the kind covered with the 
micro-retro-reflectors) and sending it up?  Would there be
enough reflectance off of it to bounce laser signals off of
it?  Would this have to be done during the day, or could it be
floated at night?  I know the FAA has some rather stringent
rules on size and weight of balloons and their launch requirements,
but, since this would be just a balloon with no payload (other than
the envelope), it might qualify for a night launch.  Maybe.
Aiming might be a problem, but, then again, a simple sweep might 
be able to find it.  

Dave
WA4QAL

> Message: 2
> From: "Steve Bailey" <[email protected]>
> To: <[email protected]>
> Subject: Re: [Laser] moon repeater
> Date: Tue, 16 Dec 2003 10:30:07 -0500
> Reply-To: [email protected]
> 
> I suppose one could lobby NASA to explode a large package of glass
> micro-spheres [the kind used in highway centerline paint] over the lunar
> surface.    -ka1rxx