[Laser] another lunar experiment

[Tim Toast]

Hi All
 While waiting for the next lunar eclipse, i thought even
though the interfering earthshine is maximum at this time,
why not try EME during the waxing moon phases when the
bright Tycho area is in darkness? This happens twice every
month when the moon is 2 to 5 days old and then again when
it is about 24 to 27 days old. 
 In order to use the Tycho area to help reflect a signal to
Europe, the transmitting must be done during daylight hours
from the US when it is early evening in Europe. So, imagine
for a bit, the moon is about 2 days old. At this time the
moon is a thin crescent in the western sky from Europe just
after sunset. And in the US, it is high in the sky about 30
degrees east of the mid afternoon sun. Assuming the moon
can be found at mid-day so early in the month - which is
very difficult without optical or computer aid, the signal
is transmitted at the moon in daylight, reflected and
received in Europe in darkness.
 Then over the next few days it gradually gets easier to
find the moon in the daytime as it moves away from the sun
about 15 degrees eastward each day. Also the window gets a
bit longer and the interfering earthshine reduces a bit
each day. So, starting at about the same time each day
during this window, a signal can be transmitted to Europe
from the US theoretically. 
 It is a one-way trip for sure though since it would be
impossible for the station in daylight to receive anything
but noise. Meanwhile the background earthshine light, which
interferes with reception, decreases by about 3 dB?? when
going from new moon to first quarter phase. 

 Now, at the end of the lunar month a similar situation
exists where everything is reversed. From about 24 to 27
days moon age, when the moon is a thinning cresent in the
eastern sky from the US before sunrise, while it is high in
the mid-day sky from Europe. 

While thinking about this it came to me that if i have to
transmit in the daytime, why not go low-tech and just use a
large flat mirror to reflect a powerful beam of sunlight at
the moon? (a-la heliograph) A one meter sized mirror can
reflect 1000 watts into a circular beam of about half a
degree - just the right size for illuminating the moon! At
1 Kilowatt CW no less. To compare that with my xenon strobe
transmitter, I am pushing the small tube to its limits to
get barely 3 kw peak and 3 watts average power to hit the
moon.

Which one would have the strongest signal i wonder??
1 killowatt CW vs. 3 kilowatts in pulses, assuming the
mirror is 100% modulated at the same frequency as the
strobe (10 Hz say)??

There are problems with the heliograph mirror though;
modulating it and aiming it. The greatest problem of which
is probably aiming. It would be simplified by a computer
controlled mount that could effortlessly position it with a
few key-strokes to an exact alignment and then track while
both sun and moon move. Seeing how they did it with
heliographs over a hundred years ago, it would probably be
a major pain to do it manually while tracking both sun and
moon.

I wanted to try this month (with my strobe transmitter) but
we had clouds today and they are forecasting rain for the
next few days. Maybe next month it will be better - June 5,
6 ,7 and 8 (moon's age 2 to 5 days)

I also wanted to add, when the moon is 2 to 5 days old, two
way transmissions become possible, after my local sunset,
between other stations in the US that are also in darkness.
And later with the 5 day old moon, the whole US would be in
range in darkness for a short time i think. (just after
sunset on the west coast, the moon would still be above my
horizon) Not that this is any shorter of a path really
considering how far away the moon is 8)

 There are other path possibilities no doubt, with or
without the Tycho constraints, just have to play around
with the astro-software to find out...

a page on my site with some info about this:
http://www.aladal.net/toast/lunarx.html





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