"Wayne Farmer" wrote:

Given the difficulty in assessing Comet 17C/Holmes' tail from an Earth
or Mars viewpoint, would there be value in imaging the comet from a
better viewpoint? Even if Cassini had enough resolution, I think the
comet would be too close to the Sun for viewing from Saturn. Are
there other options, such as Ulysses?

Ulysses does not have an imaging camera, and the MERs don't currently
have enough energy at night to use Pancam. I'm sure the guys at
http://www.unmannedspaceflight.com would be able to give a more
complete answer.