[Laser] Lunar downlink

[J. Forster]

Glenn Thomas wrote:

> Not knowing the wavelength used, it's difficult to compute what kind
> of noise level can be expected due to thermal radiation.

It was almost certainly ruby. Most likely 694nm. It was a LONG time ago. To
increase the S/N, they almost certainly used a narrow band filter in the Rx chain.

> I'm not
> aware of any steps taken to discriminate between photons due to
> atmospheric thermal radiation and photons due to the lunar return.

The sky does not glow significantly in the red. The right filter would likely kill
molecular emission lines.

> The laser PRF and receiver gating characteristics also figure into
> this calculation of course. Does anyone have access to this
> information? Boltzmann's constant I can look up, these others I can't.
>
> 73 de Glenn wb6w

There was a recent post with quite a lot of information,
-John