[Laser] How much power? Ideed!

[Charles Pooley]

James Whitfield <n5gui at cox.net> wrote:

I did not suggest that you could see a 5 mW laser shining from the Moon with
the naked eye... 
   
  For Microlaunchers I have been using as a transmitter starting point 30 mw at 650 nm, that being a round number 10e17 photons/sec.
    
  A 7 cm or slightly larger optic can make a 2 arcsec beamwidth (10 microradians), so a data transmission would land on a 4 km dia spot on earth and be about 5th magnitude.
  Earth image and an uplink location transmission at, perhaps 780 nm.
   
  For practical reasons (like getting solar power to run it) this would be coming from the daylight side of the moon to a spot on the nightside, so spotting it would rely on a bandpass filter at the receiver end, a narrow field of view, and use of the modulation.
   
  I haven't done an adequate analysis of this situation yet, but I think it can work.
   
  Charles Pooley  KD6HKU, Microlaunchers