[Laser] How much power? Ideed!

[Charles Pooley]

Art <KY1K at verizon.net> wrote:
  
>I think 4 Km footprint on the Earth is a problem. That's just to 
>small to hit reliably. Libration makes that small footprint nearly 
i>mpossible, unless your aiming platform on Earth and the one on the 
>Moon have fast response times and can lock on a star to constantly 
>correct for the libration.
   
  The 4 km is 1/10e5 of the earth-moon distance, from a 10 microradian beamwidth.
  By use of a small CCD camera imaging the crescent Earth and onboard stored information the aimpoint can be maintained.  If that has to be refined, an uplink at, say 780 nm will cause the steerable tranciever to aim to that.  It is explained in a short article in my site.
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>Does a 10 milliradian wide beam end up being 4 Km when it reaches the 
>Earth? That sounds small.
   
  10 microradian, or 2 arcsec.
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>When we listen to EME, the libration is fast enough to modulte a 
>carrier in the 10's of Hz range, so both platforms would have to be 
>pretty 'fast' to correct for the libration.
   
  Active tracking of the Earth image makes that a non-issue
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>You might store energy, so it can be used after the Moon base is in 
t>he dark as well.
   
  In any Microlauncher lunar craft there will be no batteries ir electrolytic capacitors.  They do not easily survive the  cold-soak each lunar night.  Each sunrise the sun will warm and "reawaken" the lander.
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>I notice your sig file says you are involved with microlaunchers. Is 
>this part of a plan to put a laser on the Moon?? 
   
  Microlauncher first missions will be for NEOs at about 1/10 AU and useng laser only (no RF)for data.  A lunar lander (which will have to be less than 100 grams landed weight) would also use the laser.  But seeing that against the daylit ground might be difficult--but the 1/400 AU distance will help.  I haven't thoroughly analyzed that yet.
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  >I remember someone 
>in AMSAT was talking about putting a comm center on the Moon. It 
>would be a transponder, allowing 133/432 Mhz Oscar class stations to 
>be able to QSO (single yagi and 100 watts on both ends).
   
  I do not plan any RF transmissions.
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  > I think they 
>had plans for a laser beacon as well. Are you part of that plan or do 
>you have any other information about it?
   
  I have not yet contacted AMSAT.  They are mainly centered around different ideas--RF from LEO satellites which have no launch means.
   
  A central requirement for Microlaunchers is that there is to be a Microlauncher launch vehicle.  Without that we have "tabletop spacecraft" which look good on a coffee table but have a hard time getting up there.
   
  Also, LEO craft are hidden over the horizon 99% of the time and zoom across the sky when they are visible.
   
  Charles Pooley