[Laser] Goes-East weather satellite experiment

[Tim Toast]

Hi all,
Here's a geo satellite experiment i propose that does 
not require you to have a receiver, only a visible laser
transmitter. The receiver is already on-board the 
weather satellite - its own weather imaging camera 
operating in the visible waveband. 

The idea is to point your laser at the satellite for an
hour at least and then go download the latest visible 
weather image from it online. Examine the image closely
near your location to see if the laser is visible to 
the camera. This might best be done near or shortly 
after dusk in your area, so that the ground is in dark 
contrast with any light sources. 
Only the presence or absence of light can be detected.
No modulation or integration modes can be used since 
these sats generate the image by slowly scanning the 
earth over a period of several minutes on an hourly 
repeating basis.

Apparently the Goes-East sat does not pick up any city
lights at night, so that's a crude measure of its 
sensitivity. Although you might try a bit of image 
enhancement and look for the brightest cities like 
Atlanta, or New York at night. Maybe these are faintly 
visible to the weather camera when most of the western
hemisphere is dark..i've never tried that. This probably
means your pocket laser is going to have to out-shine or
at least equal a pixel from these cities in brightness.

I picked the visible band because they invert the video
on the long wave IR cameras such that a white pixel in 
an image represents "dark" or a cold area of clouds 
against the normally brightly glowing ground heat. An 
IR laser would appear to the camera as a black pixel 
amongst many others. In the visible band images, they 
don't invert the video, and white pixels are sources of 
visible light of course - ie. sun-lit clouds, the ground
normally being a darker color unless there is ice or 
snow cover.
The beam width used is up to the individual and could be
the "normal" 1.5 mrad of typical pocket laser pointers 
or a better collimated beam of your choice depending on 
your optics and aiming abilities. 
You will need the ability to aim the transmitter fairly 
accurately at the Goes-East weather satellite - located 
near 75 degrees west longitude. (picked since i am in 
the eastern us) If another weather sat is closer to you
then use it instead. Goes-East generates the familiar 
eastern usa based weather pictures in several wavebands.
I don't know the actual goes-## designation number for 
it and they change it from time to time. Many programs 
are out there that can give you the exact pointing 
angles for it depending on your location and altitude. 
Once you have these numbers you can set up a small 
alt-az mount, point it at the bird and leave it there.
*** just looked it up and it may be Goes-12 ***

So you may need to build a simple alt-az mounting for 
the transmitter that has a pair of setting circles or 
scales on it, so you can measure the degrees of 
altitude and azimuth. This is a fun project in itself.
It will also be needed to accurately level the 
platform the mount is on - so your altitude 
measurement will be reasonably accurate. A pair of 
bubble levels would work fine for this. And use a 
compass to align the azimuth with true north. There 
are websites devoted to helping set up a satellite 
dish which may be helpful.

What would really help alignment is being able to 
actually see the satellite through your finder scope - 
this is possible for some of the geo-sats for few weeks
either side of the equinoxes - September 21 or March 21
when the sun angle is just right. So, this is coming up
in a few weeks or may already be starting to happen. 

I'm not really sure what this will prove if it's
possible. Maybe that a small pocket laser can outshine a
major city's light pollution if collimated enough? Maybe
that a passive or active optical repeater on board a 
geo-sat is possible. Or to better predict what kind 
optical repeater system would be needed on the moon for 
this type of thing. It is something anyone can try at 
least since it requires no receiver or help from anyone.
And also, maybe something can be learned from a failure 
as well, you never know. 
And finally, as the Reverend suggested, a good rectal 
reaming is not out of the question if one is really 
lonely...j/k

-toast