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Re: Laser Satellite Comms



At 06:31 PM 3/1/99 -0500, Dr Thomas A Clark (W3IWI) wrote:
it produces a diffraction limited "glint" reflection. ...
 ~1/40000 radians = 5 arc seconds. On the ground, the "spot
size" will be about 10 meters in diameter.

Oops.  You're right.  My calculated spot size was too small, as I did the calc with straight geometry and forgot to consider diffraction. 


If the satellite is spinning at ~1 RPM, it will spinning at an angular
rate of (3600 arcsec/degree)*(360 degrees/rev)/(60 sec/rev) =
21600 arcsec/sec, so the 5 arcseconds "glint" is swept out by the
mirror in 5/21600 = 230 microseconds.

Aren't you missing a factor of 2 here?  The spot spins around the disco twice as fast as the disco ball spins.  5/(21600*2) = 115 microseconds.

In any case, I agree with your conclusion.





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