QUESTION:
What could the HST see if it could be trained safely onto the earth?

ANSWER from Bill Gutsch on April 8, 1996:
It could certainly see individual houses but would be limited in
itself beyond that because of turbulence in the earth's atmoshere.
Remember, turbulence  works both ways -- for telescope down here looking
up and telescopes up there looking down.   But ... computers have long
been able to correct for such atmospheric distortion and so, yes, we
really can read license plates from orbit  (but that's a secret).
And, if we can do that with computers ... why do we need an HST ???
Well ... that's an even better question.  Hummmmm


ANOTHER ANSWER from Anuradha Koratkar on April 15, 1996:
If the HST was pointed to the Earth AND was in focus, an observer would be 
able to see two objects which are separated by 12-15cm. That is from the 
distance of HST in the sky (~601km) the telescope can see the number 
plate on a car although it would not be able to read the letters on 
the number plate!

Please note that most instruments on HST would be damaged if the telescope 
was indeed pointed to the Earth, since the Earth is too bright for these 
instruments. Further, the Earth is too close to the telescope and so the 
telescope is out of focus for such observations.  One instrument called 
the WFPC2 on HST does use the Earth as a calibration target.  
During these observations (which are out of focus and streaked, since there 
is no guiding), we have been able to distinguish  clouds, water masses etc.