QUESTION:  
How do scientists prevent micro-meteorites from colliding with the
Hubble mirrors while the telescope is in use and pointed toward space?

ANSWER from  Andrew Dougherty on May 29, 1996:
During periods when there are known micro-meteorite 'showers', such as
the Perseid showers in Aug and sometimes the Leonid showers in Nov, we
orient the telescope to point away from where the meteorites are
coming. During other times, which is most of the time, we don't do
anything special to avoid them. At a recent meeting, we were shown
data based on video analysis of 1st servicing mission (Dec 1993) that
there were over 700 visible impacts on the aft shroud (the lower part
of HST on cylinder sides). On the one solar array that was returned
after the 1st servicing mission over 200 debris hits were seen. Based
on this you can assume that there are many impacts on the main mirror.
I don't know how many it would take to blur an image, but it is many
times more than there are now.