[Laser] comments about Moon pictures

[Art]

>
>
>Taking pictures on the Moon and teaching science on the Earth is exactly the
>kind of thing that international treaties are trying to encourage.  If you
>want to throw boulders down onto cities you don't like.... Now that will 
>bring
>out more than just the lawyers.
>

I'm not sure what the optimum picture taking conditions are, but for trying 
to receive a laser, you need the laser to be in the dark. The telescope 
will need to be a fairly narrow field of view in order to reject the 
photons from the lighted portion of the Moon.  For us, this probably means 
we want the laser transmitter attempts timed when the Moon is mostly dark.

>I think I said something before about retro-reflectors in orbit.  It would be
>better if the return beam width was greater.  The true geo-synchronous orbits
>are too valuable to tinkerers like us to be allowed to use.  But the
>mechanics of orbits is such that a satellite can be "hung" in a small 
>patch of sky for
>a few hours below the geosynchronous altitude.  Above the geosynchronous
>altitude has some more potential.  Circular vs eliptical.... too far off 
>topic for
>now.


I used to belong to a visual satellite viewing mailing list. These people 
tracked and viewed many of the satellites in orbit and they were very 
knowledgeable about the satellites purpose and it's construction. I 
remember discussions about corner reflectors and about multiple mirrors on 
a randomly rotating ball type structure.

The group also had specialized tracking software, called 'skymap'. It took 
the entire unclassified Weekly Keplarian element set and would match the 
reported path of a satellite with likely hits, including estimated 
brightness and the point at which the satellite winks out (passes in the 
darkness from the earth's shadow).  The time and alt/az at wink out is a 
big clue regarding which satellite you are viewing!

I have no idea where that group is now, but anyone interested in trying to 
hit satellites with lasers should seek them out and ask about what 
satellites might be appropriate.

Much of the calculations necessary for returned timing and signal strength 
has already been done, a search on google for 'satellite laser ranging' 
will yield tons of useful information for amateurs. The SLR people have 
been doing this for years now, although they are not QRP:>: The 
professional SLR stations use multiwatt laser and 1 meter in diameter 
telescopes. Technically, they are looking for a pulse to be returned, so 
it's possible that us amateurs might not need so much transmit power and 
big optics as we are not looking for pulse returns.

I think there was a Texas University that had a HUGH SLR station that was 
well documented on the web.

I tend to think that QRP satellite laser ranging is a tall order, mainly 
because return from the transmitter in the lower atmosphere (which is 
significant) will mask the return from the satellite and it would be 
difficult to tell the difference.



>Thanks to all.
>
>James
>N5GUI
>
>
>--- StripMime Report -- processed MIME parts ---
>multipart/alternative
>   text/plain (text body -- kept)
>   text/html
>The reason this message is shown is because the post was in HTML
>or had an attachment.  Attachments are not allowed.  To learn how
>to post in Plain-Text go to: http://www.expita.com/nomime.html  ---
>_______________________________________________
>Laser mailing list
>Laser@mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/laser