[Laser] Lunar downlink

[Stewart Nelson]

> A good test would've been to shut the laser off and see how many
> photons (thermal radiation from the atmosphere, the telescope or
> even the mirror itself) they got then! I don't know if they did
> something like this.

Perhaps I'm missing something, but isn't the dominant noise caused
by earthshine?  It seems obvious that you have to do this experiment
at night.  Also, you would need to do it when it's night at the lunar
target.  For example, if you did it at half moon, then the moon is
seeing approximately half earth.  So, the target area is illuminated
by lots of earthlight.

You could avoid most of the noise by testing during a lunar eclipse,
but I believe that is not necessary, because the range gate eliminates
99.9996% of the noise (open for 100 nanoseconds every 25 milliseconds).
http://physics.ucsd.edu/~tmurphy/apollo/timing.html

73,

Stewart KK7KA