Didn't we leave a retro-reflector up on the moon on one of the last trips?
It might be fun to illuminate that again.
Ed
----- Original Message -----
From: "Art" <artky1k@UNINETS.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, March 13, 2004 9:30 PM
Subject: Re: [EE]: Long-Range, Low-Power IR Transceiver


> >
> >Anyone doing EME (earth moon earth) with light? Presumably
> >a sufficiently narrow band optical filter and collimation would
> >do the trick.
>
>
> EME won't work at amateur power levels, even if you use the
retroreflectors
> left there on the surface. With kilowatt powered lasers, you only get a
> couple hundred photons per second back. So, us civilian laser folks will
> never get to do EME. Even at these power levels, ultranarrow field of
views
> are needed in the receiver optics, the receiver optics must be very large
> very large collimators are needed. The large collimator makes a very tight
> beamwidth on transmit, but this causes the shots at the retroreflector to
> miss most of the time because the moon's libration becomes a problem then.
> The large amount of ambient light from the moon's surface puts the final
> nail in the EME coffin, at least for us civilian types.
>
>
> >Per HOUR seems rather pointless though. Almost as bad a
> >submarine communications using ULF radio.
>
> It depends on your purpose. Several characters per hour is OK as long as
> you don't want to transfer pictures or wav files:>: Seriously, the idea of
> ultra narrow bandwidth receivers is to research and study tropospheric
> bending, ducting and reflections to see if non-line of sight
communications
> is practical. For this purpose, we only need to put up a stable frequency
> and then look for traces with the same frequency on the other end of the
> path. It's a long term study, so we set the receiver up and then go to bed
> and check out the stored data the next day at our leisure.
>
> >Speaking of submarines, do they not now use laser communications
> >from satellites to ultrasensitive optical detectors?
>
> Unknown, but I did read that the military uses satellite based laser to
> uplink and downlink from their unmanned surveillance aircraft.
>
> Good luck.
>
> Art
>
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