>. I've read that on one of the Apollo missions they left a
> retro reflector on the moon. I've also seen that at the University of
> New Mexico, they had set up a laser to bounce a beam off the reflector
> and measure the distance to the moon.
Yes, this is true. The reflector assembly is about the size of a small
kitchen stepladder
> I have a two stage proposal:
Then stage 0 :
You'll want to do some research with Amateur Radio guys who have been
doing moonbounce (primarily at 432 MHz and 1296 MHz) for several
decades, using kilowatt CW transmitters and giant receiving antennas.
It is one thing to _see_ a laser beam reflected back to earth. It is
somewhat
more difficult to get a usable narrowband radio signal back and be able to
demodulate it well. Two problems are (1) phase scattering of the signal
due to being reflected from a non-homogeneous lunar surface and (2)
doppler shift of the received signal due to the round trip distance slowly,
and continuously varying as the lunar orbit is not precisely circular, and
as the earth rotates toward/away from the lunar reflection point. i.e. the
doppler shift itself varies. I would suspect that laser light starts looking
rather fuzzy spectrally when it comes back here.
The hams use CW (morse code) with a couple seconds on, a couple
seconds off, for the on/off pulses, in order to integrate the received
signal
out of the noise.
I saw a figure long ago for the RT path loss, I am not sure but think it
was 130 dB (at that bandwidth).
Bob
> 1) to replicate the above experiment and be able to accurately measure
> the distance to the moon to an accuracy of 1ns (.98 ft).
>
> 2) with a round trip delay of 2.68 sec, to encode the beam with data in
> a regenerative loop. Depending on just how fast you can modulate, you
> should be able to attain a storage density of several Gigabytes to
> possibly a Terabyte or more with a mean access of 1.3 sec.
>
> I've got a 60mW Argon laser that might be able to make the trip and I
> have a domain name registered for a project blog 'moonbounce.org'. Need
> a telescope (12" Cassegrain would work well), EO modulators, appropriate
> photo detection, clocking system with nanosecond resolution that can
> count for several seconds without a rollover and a Terabyte of test data
> (anyone have any contacts at the Library of Congress?).
>
>
> Todd
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