QUESTION:
Can the "original" HST images of Pluto be used to provide an upper-size
limit for additional satellites of Pluto?

ANSWER from Sanjay Limaye on May 16, 1996:
In principle yes, however, without knowing the exposure time for the image,
it is difficult to tell.  The best way to discover moons is actually by
taking a long exposure such that undiscovered moons show up as trails,
particularly if the camera tracks the stars.  This is how Voyager
discovered many of the moons.  Even very small moons show up very
distinctly in the data this way.  Any undiscovered moons of Pluto are
likely to be much smaller than Charon.  I do not know of any systematic
effort to look for new moons of Pluto though.