[Laser] Re: street light EME

[Art]

I read this thread with great interest, especially after I started 
thinking about a high altitude balloon helium/hydrogen based receiver 
receiving platform. I've recently become interested in high altitude 
balloon launches and streetlight EME sounds like an ideal application 
for an amateur based high altitude balloon group.

Here's what we have going for us at high altitude (over 75,000 feet)........

At 75,000 feet, 98 percent of the Earth's atmosphere is underneath 
the balloon. So, there would be very little scattering from ground 
based lights. Even during the daytime, a camera pointed towards space 
shows a pitch black background. Due to the cold temperatures, there 
would be very little water vapour, so there is very little there to 
scatter light. The temperatures are also very cold aloft, typically 
-60C at 75,000 feet (regardless of the season or the latitude and 
longitude of the launch).

At 75,000 feet, the magnetic fields from the power grid on Earth 
would be almost nil, so there would be less QRM from direct induction 
of magnetic fields produced by ground based power grids.

I submit that the best chances for detecting streetlight EME would be 
from a high altitude balloon, and the cold temperatures would allow 
much quieter optical receivers to boot, whether they were photodiode 
or photomultiplier based.

A close second might be to launch from a ship, 1000 miles from land 
or perhaps from the Arctic or Antarctic regions during their local Winters..

I have some 3/8 inch photomultiplier tubes (with sockets) that are 
highly sensitive to yellow and green although they are only 9 stage, 
so the gain is around 50,000 instead of 10^6 (10^6 is more typical 
for photomultiplier gain). I also have some cockroft-walton based 
power supplies for PMT's-the advantage here is that they don't use a 
resistive divider. Since there are no resistive dividers used, the 
heat from the resistors doesn't end up heating the tube and the total 
supply current from a 12 volt source is probably going to be 10 ma or 
so (in darkness).

One would have to set the elevation angle of the receiver prior to 
launch and a large bar magnet can be used to keep the receiver 
pointed at the proper azimuth.....so a fixed altitude and azimuth 
(aiming) is not a significant issue.

If the balloon launch could be timed to coincide with a total 
eclipse, I think the results would be pretty conclusive. Certainly 
we'd have our best chance of success with a high altitude based 
receiver launched during a total eclipse.

Regards,

Art