QUESTION:
The spacecraft can point the instruments with an accuracy of 1 milliradian.
This is like being able to shoot a quarter 12 meters away with a rifle.

should it not be

12 Miles instead of 12 meters ??

ANSWER from Trina Ray on January 14, 2000:
Weellllll, actually that number (12 meters) is correct.  If you ask "at
what distance does half a quarter (1.25 cm) subtend 1 mrad"; you get 12
meters.  (By the way you use 1/2 the quarter's diameter since the 1 mrad
pointing accuracy is a circle whose radius is 1 mrad).  I have also
verified that the pointing accuracy of Cassini, is in fact, 1 milliradian.
So, where does this leave us.

Well, 1 milliradian = 0.05729 degrees = 3.42 arcmin = 205 arcsec.  How
does this compare to an actual telescope.  My research telescope has a
pointing accuracy of about 1/2 an arcmin or 30 arcsec.  So, Cassini is
about 6 times worse...but, of course, the spacecraft is flying through
space with infinite degrees of freedom to spin and my research telescope
has only 2 degrees of freedom (it's sitting on the ground and can only move
around it's two axes).  So, where does this leave us.

I think where this leaves us, is that the pointing accuracy of Cassini
is not so amazing as most of the amazing capabilities of the spacecraft,
but that it's still really good for what it's doing.  I hope this
helps...at the very least you have sparked general debate amongst the
outreach team here on the project about how to describe the pointing
capability of our wonderful spacecraft.  Thanks.